MIL-STD-810G – Part 27 – (Rail Impact) Method 526

MIL-STD-810G covers Rail Impact in Method 526.  Method 526 is new to 810G and the purpose of this test method is to replicate the railroad car impact conditions that occur during the life of transport of systems, subsystems and units, and the tiedown arrangements during the specified logistic conditions.  Method 526 is short at 7 pages.

Method 526 is also not intended for testing small, individually packaged material that would normally be shipped when mounted on a pallet or as part of a larger shipment.  It is intended for testing items such as tanks, trucks, etc., that are transported by rail.

The rail impact test is intended to test materiel that will be transported by rail; to determine the effect of railroad car impacts that may occur during rail shipment, to verify the structural integrity of the materiel, to evaluate the adequacy of the tiedown system and the tiedown procedures, and to assess transportability1 by the Military Surface Deployment and Distribution Command Transportation Engineering Agency (SDDCTEA). All items are to be tested at their maximum gross weight (fully loaded) rating unless otherwise specified in the transportability requirements for the materiel. 

Subjecting materiel to a lab shock test or performing an analytical simulation does not eliminate the requirement to conduct a rail impact test.

Method 526 is not intended for railcar crash conditions. 

Effects of Rail Impact

Rail impact shock has the potential for producing adverse effects on the physical and functional integrity of transported materiel. The following are examples of problems that could occur when materiel is exposed to the rail impact environment.

1. Loosening of tiedown straps.


2. Failure of attachments, creating a safety hazard.


3. Shifting of materiel on the railcar.


4. Failure of materiel.


5. Structural failure.


6. Fuel spills.

Testing

Tests are performed with rail cars. 

Loaded cars are preferred for use as the buffer or struck cars. However, empty cars may also be used. In either case, the total weight of the buffer cars is to be at least 113,400kg (250,000 lb). The first buffer car must be a standard draft gear car. The remaining buffer cars should have standard draft gear, if possible.  Draft gear is the shock absorber which is part of the coupler.

The test railcar is equipped with chain tiedowns and end-of-car cushioned draft gear, unless other railcar types are approved by Director, SDDCTEA. SDDCTEA is the designated DoD agent for land transportation. Some materiel may require other types of railcars for testing to be representative of the intended shipping methods.

A locomotive and at least 200 feet of dry, level track is used to get the rail cars up to the required speed as below.  At the desired speed, the test load car is released so it rolls freely into the buffer cars with the couplings open.  An alternative method of testing is to use an inclined track of sufficient length and gradient to achieve the test speeds.

The test item secured to the test railcar should be at gross weight with the fuel tanks at least 3/4 full.

Subject the test item to four impacts, the first three of which are in the same direction and at speeds of 4, 6, and 8 mph respectively. Perform the fourth impact at 8 mph (+0.5, -0.0 mph) impacting the opposite end of the test car from the first three impacts. If it is not possible to turn the test car because of track layout, this may be accomplished by running the test item car to the opposite end of the buffer cars and impacting as above.

Analysis

1. The test item fails this test if the test item, or any item that is attached to it, or that is included as an integral part of the test item, breaks free, loosens, or shows any sign of permanent deformation beyond specification tolerances.


2. The test item and its subassemblies must be operationally effective after the test.


3. f tiedown securement items break or displace substantially, photograph and document the problem areas for evaluation of the procedures and materials used. The test director and SDDCTEA jointly decide if any failed securement items require reconfiguring and, if so, whether a complete retest is required.


4. Additional considerations:
   (1) Loosening of tiedown straps.
   (2) Failure of attachments, creating a safety hazard.
   (3) Shifting of materiel on the railcar.
   (4) Failure of materiel.
   (5) Structural failure.
   (6) Fuel spills.

MIL-STD-810G – Part 27 – (Rail Impact) Method 526

MIL-STD-810G – Part 27 – (Rail Impact) Method 526

MIL-STD-810G covers Rail Impact in Method 526.  Method 526 is new to 810G and the purpose of this test method is to replicate the railroad car impact conditions that occur during the life of transport of systems, subsystems and units, and the tiedown arrangements during the specified logistic conditions.  Method 526 is short at 7 pages.

Method 526 is also not intended for testing small, individually packaged material that would normally be shipped when mounted on a pallet or as part of a larger shipment.  It is intended for testing items such as tanks, trucks, etc., that are transported by rail.

The rail impact test is intended to test materiel that will be transported by rail; to determine the effect of railroad car impacts that may occur during rail shipment, to verify the structural integrity of the materiel, to evaluate the adequacy of the tiedown system and the tiedown procedures, and to assess transportability1 by the Military Surface Deployment and Distribution Command Transportation Engineering Agency (SDDCTEA). All items are to be tested at their maximum gross weight (fully loaded) rating unless otherwise specified in the transportability requirements for the materiel. 

Subjecting materiel to a lab shock test or performing an analytical simulation does not eliminate the requirement to conduct a rail impact test.

Method 526 is not intended for railcar crash conditions. 

Effects of Rail Impact

Rail impact shock has the potential for producing adverse effects on the physical and functional integrity of transported materiel. The following are examples of problems that could occur when materiel is exposed to the rail impact environment.

1. Loosening of tiedown straps.


2. Failure of attachments, creating a safety hazard.


3. Shifting of materiel on the railcar.


4. Failure of materiel.


5. Structural failure.


6. Fuel spills.

Testing

Tests are performed with rail cars. 

Loaded cars are preferred for use as the buffer or struck cars. However, empty cars may also be used. In either case, the total weight of the buffer cars is to be at least 113,400kg (250,000 lb). The first buffer car must be a standard draft gear car. The remaining buffer cars should have standard draft gear, if possible.  Draft gear is the shock absorber which is part of the coupler.

The test railcar is equipped with chain tiedowns and end-of-car cushioned draft gear, unless other railcar types are approved by Director, SDDCTEA. SDDCTEA is the designated DoD agent for land transportation. Some materiel may require other types of railcars for testing to be representative of the intended shipping methods.

A locomotive and at least 200 feet of dry, level track is used to get the rail cars up to the required speed as below.  At the desired speed, the test load car is released so it rolls freely into the buffer cars with the couplings open.  An alternative method of testing is to use an inclined track of sufficient length and gradient to achieve the test speeds.

The test item secured to the test railcar should be at gross weight with the fuel tanks at least 3/4 full.

Subject the test item to four impacts, the first three of which are in the same direction and at speeds of 4, 6, and 8 mph respectively. Perform the fourth impact at 8 mph (+0.5, -0.0 mph) impacting the opposite end of the test car from the first three impacts. If it is not possible to turn the test car because of track layout, this may be accomplished by running the test item car to the opposite end of the buffer cars and impacting as above.

Analysis

1. The test item fails this test if the test item, or any item that is attached to it, or that is included as an integral part of the test item, breaks free, loosens, or shows any sign of permanent deformation beyond specification tolerances.


2. The test item and its subassemblies must be operationally effective after the test.


3. f tiedown securement items break or displace substantially, photograph and document the problem areas for evaluation of the procedures and materials used. The test director and SDDCTEA jointly decide if any failed securement items require reconfiguring and, if so, whether a complete retest is required.


4. Additional considerations:
   (1) Loosening of tiedown straps.
   (2) Failure of attachments, creating a safety hazard.
   (3) Shifting of materiel on the railcar.
   (4) Failure of materiel.
   (5) Structural failure.
   (6) Fuel spills.

MIL-STD-810G – Part 27 – (Rail Impact) Method 526

MIL-STD-810G – Part 27 – (Rail Impact) Method 526

MIL-STD-810G covers Rail Impact in Method 526.  Method 526 is new to 810G and the purpose of this test method is to replicate the railroad car impact conditions that occur during the life of transport of systems, subsystems and units, and the tiedown arrangements during the specified logistic conditions.  Method 526 is short at 7 pages.

Method 526 is also not intended for testing small, individually packaged material that would normally be shipped when mounted on a pallet or as part of a larger shipment.  It is intended for testing items such as tanks, trucks, etc., that are transported by rail.

The rail impact test is intended to test materiel that will be transported by rail; to determine the effect of railroad car impacts that may occur during rail shipment, to verify the structural integrity of the materiel, to evaluate the adequacy of the tiedown system and the tiedown procedures, and to assess transportability1 by the Military Surface Deployment and Distribution Command Transportation Engineering Agency (SDDCTEA). All items are to be tested at their maximum gross weight (fully loaded) rating unless otherwise specified in the transportability requirements for the materiel. 

Subjecting materiel to a lab shock test or performing an analytical simulation does not eliminate the requirement to conduct a rail impact test.

Method 526 is not intended for railcar crash conditions. 

Effects of Rail Impact

Rail impact shock has the potential for producing adverse effects on the physical and functional integrity of transported materiel. The following are examples of problems that could occur when materiel is exposed to the rail impact environment.

1. Loosening of tiedown straps.


2. Failure of attachments, creating a safety hazard.


3. Shifting of materiel on the railcar.


4. Failure of materiel.


5. Structural failure.


6. Fuel spills.

Testing

Tests are performed with rail cars. 

Loaded cars are preferred for use as the buffer or struck cars. However, empty cars may also be used. In either case, the total weight of the buffer cars is to be at least 113,400kg (250,000 lb). The first buffer car must be a standard draft gear car. The remaining buffer cars should have standard draft gear, if possible.  Draft gear is the shock absorber which is part of the coupler.

The test railcar is equipped with chain tiedowns and end-of-car cushioned draft gear, unless other railcar types are approved by Director, SDDCTEA. SDDCTEA is the designated DoD agent for land transportation. Some materiel may require other types of railcars for testing to be representative of the intended shipping methods.

A locomotive and at least 200 feet of dry, level track is used to get the rail cars up to the required speed as below.  At the desired speed, the test load car is released so it rolls freely into the buffer cars with the couplings open.  An alternative method of testing is to use an inclined track of sufficient length and gradient to achieve the test speeds.

The test item secured to the test railcar should be at gross weight with the fuel tanks at least 3/4 full.

Subject the test item to four impacts, the first three of which are in the same direction and at speeds of 4, 6, and 8 mph respectively. Perform the fourth impact at 8 mph (+0.5, -0.0 mph) impacting the opposite end of the test car from the first three impacts. If it is not possible to turn the test car because of track layout, this may be accomplished by running the test item car to the opposite end of the buffer cars and impacting as above.

Analysis

1. The test item fails this test if the test item, or any item that is attached to it, or that is included as an integral part of the test item, breaks free, loosens, or shows any sign of permanent deformation beyond specification tolerances.


2. The test item and its subassemblies must be operationally effective after the test.


3. f tiedown securement items break or displace substantially, photograph and document the problem areas for evaluation of the procedures and materials used. The test director and SDDCTEA jointly decide if any failed securement items require reconfiguring and, if so, whether a complete retest is required.


4. Additional considerations:
   (1) Loosening of tiedown straps.
   (2) Failure of attachments, creating a safety hazard.
   (3) Shifting of materiel on the railcar.
   (4) Failure of materiel.
   (5) Structural failure.
   (6) Fuel spills.

MIL-STD-810G – Part 27 – (Rail Impact) Method 526

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MIL-STD-810G – Part 27 – (Rail Impact) Method 526

MIL-STD-810G covers Rail Impact in Method 526.  Method 526 is new to 810G and the purpose of this test method is to replicate the railroad car impact conditions that occur during the life of transport of systems, subsystems and units, and the tiedown arrangements during the specified logistic conditions.  Method 526 is short at 7 pages.

Method 526 is also not intended for testing small, individually packaged material that would normally be shipped when mounted on a pallet or as part of a larger shipment.  It is intended for testing items such as tanks, trucks, etc., that are transported by rail.

The rail impact test is intended to test materiel that will be transported by rail; to determine the effect of railroad car impacts that may occur during rail shipment, to verify the structural integrity of the materiel, to evaluate the adequacy of the tiedown system and the tiedown procedures, and to assess transportability1 by the Military Surface Deployment and Distribution Command Transportation Engineering Agency (SDDCTEA). All items are to be tested at their maximum gross weight (fully loaded) rating unless otherwise specified in the transportability requirements for the materiel. 

Subjecting materiel to a lab shock test or performing an analytical simulation does not eliminate the requirement to conduct a rail impact test.

Method 526 is not intended for railcar crash conditions. 

Effects of Rail Impact

Rail impact shock has the potential for producing adverse effects on the physical and functional integrity of transported materiel. The following are examples of problems that could occur when materiel is exposed to the rail impact environment.

1. Loosening of tiedown straps.


2. Failure of attachments, creating a safety hazard.


3. Shifting of materiel on the railcar.


4. Failure of materiel.


5. Structural failure.


6. Fuel spills.

Testing

Tests are performed with rail cars. 

Loaded cars are preferred for use as the buffer or struck cars. However, empty cars may also be used. In either case, the total weight of the buffer cars is to be at least 113,400kg (250,000 lb). The first buffer car must be a standard draft gear car. The remaining buffer cars should have standard draft gear, if possible.  Draft gear is the shock absorber which is part of the coupler.

The test railcar is equipped with chain tiedowns and end-of-car cushioned draft gear, unless other railcar types are approved by Director, SDDCTEA. SDDCTEA is the designated DoD agent for land transportation. Some materiel may require other types of railcars for testing to be representative of the intended shipping methods.

A locomotive and at least 200 feet of dry, level track is used to get the rail cars up to the required speed as below.  At the desired speed, the test load car is released so it rolls freely into the buffer cars with the couplings open.  An alternative method of testing is to use an inclined track of sufficient length and gradient to achieve the test speeds.

The test item secured to the test railcar should be at gross weight with the fuel tanks at least 3/4 full.

Subject the test item to four impacts, the first three of which are in the same direction and at speeds of 4, 6, and 8 mph respectively. Perform the fourth impact at 8 mph (+0.5, -0.0 mph) impacting the opposite end of the test car from the first three impacts. If it is not possible to turn the test car because of track layout, this may be accomplished by running the test item car to the opposite end of the buffer cars and impacting as above.

Analysis

1. The test item fails this test if the test item, or any item that is attached to it, or that is included as an integral part of the test item, breaks free, loosens, or shows any sign of permanent deformation beyond specification tolerances.


2. The test item and its subassemblies must be operationally effective after the test.


3. f tiedown securement items break or displace substantially, photograph and document the problem areas for evaluation of the procedures and materials used. The test director and SDDCTEA jointly decide if any failed securement items require reconfiguring and, if so, whether a complete retest is required.


4. Additional considerations:
   (1) Loosening of tiedown straps.
   (2) Failure of attachments, creating a safety hazard.
   (3) Shifting of materiel on the railcar.
   (4) Failure of materiel.
   (5) Structural failure.
   (6) Fuel spills.

MIL-STD-810G – Part 27 – (Rail Impact) Method 526

MIL-STD-810G – Part 26 – (Freeze/Thaw) Method 524

MIL-STD-810G covers Freeze/Thaw in Method 524.  Method 524 is new to 810G and was adopted from NATO STANAG 4370, AECTP 300, Method 315. The purpose of the test is to determine the ability of material to withstand the effects of moisture phase changes between liquid and solid (freezing) and the effects of moisture induced by transfer from a cold-to-warm or warm-to-cold environment.  It is a short 6 pages. This test is applicable to materiel that will experience one or more excursions through the freeze point while wet or in the presence of moisture (free water or vapor).

This test is not intended to evaluate the effects of low temperature, thermal shock, rain, or icing. These may be determined using Methods 502.5, 503.5, 506.5, and 521.3, respectively.

Effects of the Environment

This test induces physical changes in or on the materiel that is not stationary. Examples of problems that could occur during this test are as follows:

1. Distortion or binding of moving parts.


2. Failure of bonding materials.


3. Failure of seals.


4. Failure of materials due to freezing/re-freezing of absorbed, adjacent, or free water.


5. Changes in characteristics of electrical components.


6. Electrical flashover/reduced insulation resistance.


7. Fogging of optical systems during freeze-thaw transitions.


8. Inability to function correctly due to ice adhesion and interference or blockage of moving parts.

Test Procedures

Method 524 provides three test procedures:

Procedure I, Diurnal Cycling Effects – To simulate the effects of diurnal cycling on materiel exposed to temperatures varying slightly above and below the freeze point that is typical of daytime warming and freezing at night when deposits of ice or condensation, or high relative humidity exist.  Test for 20 cycles.

Procedure II, Fogging – For materiel transported directly from a cold to a warm environment such as from an unheated aircraft, missile or rocket, to a warm ground area, or from a cold environment to a warm enclosure, and resulting in free water or fogging.  Test for 3 cycles.

Procedure III, Rapid Temperature Change – For materiel that is to be moved from a warm environment to a cold environment (freeze) and then back to the warm environment, inducing condensation (free water).  Test for 3 cycles.

Because this is a freezing cycle test, the required temperature range is narrow with cycle ranges between +5 deg C and-10 deg C.  Use moisture from local, clean sources and apply as water vapor or free water spray.

 

 

 

MIL-STD-810G – Part 26 – (Freeze/Thaw) Method 524

MIL-STD-810G – Part 25 – (Vibro-Acoustic/Temperature) Method 523.3

MIL-STD-810G covers Vibro-Acoustic/Temperature in Method 523.3.  Method 523.3 is performed to determine the synergistic effects of vibration, acoustic noise, and temperature on externally carried aircraft stores such as bombs, missiles and sensor pods during captive carry flight.  It is 16 pages plus one 9-page Annex.

This method would apply to rugged embedded computer systems as installed in externally mounted sensor pods.

Application

For captively-carried stores, this method is intended primarily to test electronics and other electro-mechanical assemblies within the store for functionality in a vibro-acoustic/temperature environment.

Limitations

This method is not intended to provide for:

1. An environmental design qualification test of a store or any of its individual components for functionality. (For such testing see Method 500.5, Altitude; Method 501.5, High Temperature; Method 502.5, Low Temperature; Method 503.5, Temperature Shock; Method 507.5, Humidity; Method 513.6, Acceleration; Method 514.6, Vibration; Method 515.6, Acoustic Noise; Method 516.6, Shock; Method 517.1, Pyroshock; and Method 520.3, Temperature, Humidity, Vibration, Altitude).


2. An environmental design qualification test of a store air frame or other structural components for structural integrity.


3. Any test to satisfy the requirements of the Life Cycle Profile except that for the combined vibration, acoustic, and temperature environments related to reliability testing.

Tailoring Guidance

Possible effects of a combination of vibration, acoustic noise, and temperature include all effects that these factors can cause separately (see Methods 514.6, 515.6, and 520.3). In addition, increased stress as a result of moisture from thermal change may produce possible effects seen in Methods 501.5, 502.5, 503.5, and 507.5. The combined vibration, acoustic noise, and temperature environments may interact to produce effects that would not occur in any single environment or a lesser combination of environments.

Not all environmental stresses contribute equally to materiel deterioration or failure. Analysis of service-use failures caused by aircraft environmental stress on the store (paragraph 6.1, reference a) has identified the following four most important causes of failure:

1. loading of the store through captive carriage,


2. temperature,


3. vibration, and


4. moisture.

Operating any materiel item produces stress that can cause failure. In the case of external aircraft stores, operation generally means providing full electrical power, that produces thermal, electromagnetic, and electrochemical stress.

Temperature

The most severe temperature shock to internal components may come from powering the materiel when it is cold. In order to induce all the stresses related to temperature in their proper proportion, use a thermal model of the store to predict the temperatures and rates of change at several internal points under service mission profiles.  Temperature is constrained by the following:

1. Ambient Temperature
   The greatest variations in ambient temperature occur near the surface of the Earth. The low temperature extreme experience by a store is, in many cases, due to low ambient temperatures immediately preceding flight.


2. Aerodynamic Heating
   During captive flight, the high convective heat transfer rate will cause the surface temperature of an external store to be near that of the boundary layer.


3. Power Dissipation
   Although the high heat transfer rate will tend to keep the surface of a store at the boundary layer recovery temperature, internal temperatures may be considerably higher due to power dissipation of electronic equipment.


4. Temperature Gradients
   The strongest temperature gradients will usually be those associated with powering the materiel when it is cold. Temperature gradients will also occur due to changes in flight speed and altitude that change the surface temperature more rapidly than internal temperatures.

Vibration

Vibration may cause mechanical fatigue failure of parts, abrasion due to relative motion, dislodging of loose particles that can cause electrical shorts, and degradation of electronic functions through microphonics and triboelectric noise.

Moisture

Moisture, in conjunction with soluble contaminants, can result in corrosion. In conjunction with electrical power it may result in shorts. Freezing of water in confined spaces may produce mechanical stress. The test cycle should provide for diffusion of water vapor and condensation.

Shock

Shock can cause failure through mechanical stress similar to that induced by vibration. Shocks that are more nearly transient vibrations (many zero crossings), such as aircraft catapult and arrested landing shock, may be included in this test. Short duration shocks such as pyrotechnic shocks associated with store or sub-munition launch, flight surface deployment, etc., are generally too difficult to reproduce at the store level. Ensure that these events that are potentially destructive to electronics are accounted for in other analyses and tests.

Altitude

Barometric pressure is generally not a stress for external stores. However, variation in pressure may enhance the penetration by moisture. Reduced pressure may increase the temperature due to reduced power dissipation and there may be increased electrical arcing.

Testing

Testing for Method 523.3 is very difficult and requires highly specialized test facilities.  The test item is subjected, simultaneously, to high energy acoustic noise up to 165dB over the range of 150 to 2500 Hz, vibration by electrodynamic or electrohydraulic exciters and temperature in the range of -40 deg C to +85 deg C with a rate of change as high as 4 deg C.  The test item is power cycled to induce electrical stress.  The test item is instrumented for acceleration, acoustic pressure, and temperature plus other measurements as required by the particular store.

Typical Arrangement of MIL-STD-810G Method 523.3 Test Apparatus

MIL-STD-810G – Part 25 – (Vibro-Acoustic/Temperature) Method 523.3

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MIL-STD-810G – Part 24 – (Ballistic Shock) Method 522

MIL-STD-810G covers Ballistic Shock in Method 522.  Method 522 is somewhat lengthy at 13 pages and covers the momentum exchange between two or more bodies or momentum exchange between a liquid or gas and a solid.  The method is used to assure components mounted in, for example, an armored vehicle continue to operate after that vehicle has been hit buy non-penetrating enemy fire or a nearby mine.

Ballistic Shock Defined

Ballistic Shock is a high-level shock that generally results from the impact of projectiles or ordnance on armored combat vehicles.  Armored combat vehicles must survive the shocks resulting from large caliber non-perforating projectile impacts, mine blasts, and overhead artillery attacks, while still retaining their combat mission capabilities.  This is a very complex subject given actual shock levels vary with the type of vehicle, the specific munition used, the impact location or proximity, and where on the vehicle the shock is measured.  No good computational simulation has yet been  developed.  That is, the prediction of response to ballistic shock is, in general, not possible except in the simplest configurations. When an armored vehicle is subjected to a non-perforating large caliber munition impact or blast, the structure locally experiences a force loading of very high intensity and of relatively short duration. Though the force loading is localized, the entire vehicle is subjected to stress waves traveling over the surface and through the structure.

General characteristics of ballistic shock environments are as follows:

1. near-the-source stress waves in the structure caused by high material strain rates (nonlinear material region) that propagate into the near field and beyond;


2. combined low and high frequency (10 Hz – 1,000,000 Hz) and very broadband frequency input;


3. high acceleration (300g – 1,000,000g) with comparatively high structural velocity and displacement response;


4. short-time duration (<180 msec);


5. high residual structure displacement, velocity, and acceleration response (after the event);


6. caused by (1) an inelastic collision of two elastic bodies, or (2) an extremely high fluid pressure applied for a short period of time to an elastic body surface coupled directly into the structure, and with point source input, i.e., input is either highly localized as in the case of collision, or area source input, i.e., widely dispersed as in the case of a pressure wave;


7. comparatively high structural driving point impedance (P/v, where P is the collision force or pressure, and v the structural velocity). At the source, the impedance could be substantially less if the material particle velocity is high;


8. measurement response time histories that are very highly random in nature, i.e., little  repeatability and very dependent on the configuration details;
   i. shock response at points on the structure is somewhat affected by structural discontinuities;


9. structural response may be accompanied by heat generated by the inelastic impact or the fluid blast wave;


10. the nature of the structural response to ballistic shock does not suggest that the materiel or its components may be easily classified as being in the “near field” or “far field” of the ballistic shock device. In general, materiel close to the source experiences high accelerations at high frequencies, whereas materiel far from the source will, in general, experience high acceleration at low frequencies as a result of the filtering of the intervening structural configuration.

Effects of Ballistic Shock

1. a. materiel failure as a result of destruction of the structural integrity of micro electronic chips including their mounting configuration;


2. materiel failure as a result of relay chatter;


3. materiel failure as a result of circuit card malfunction, circuit card damage, and electronic connector failure. On occasion, circuit card contaminants having the potential to cause short circuits may be dislodged under ballistic shock. Circuit card mounts may be subject to damage from substantial velocity changes and large displacements.


4. materiel failure as a result of cracks and fracture in crystals, ceramics, epoxies or glass envelopes.


5. materiel failure as a result of sudden velocity change of the structural support of the materiel or the internal structural configuration of the mechanical or electro-mechanical materiel.

Selecting a Test Procedure

Method 22 provides for five ballistic shock tests:

Procedure I – Ballistic Hull and Turret
Procure an actual vehicle or prototype and fire appropriate threat projectiles at it.  This is a very expensive test.

Procedure II – Large Scale Ballistic Shock Simulator
Shock testing of complete components, with assemblies weighing up to 1100 lbs, can be accomplished using devices such as a Large Scale Ballistic Shock Simulator. For large items, the Large Scale Ballistic Shock Simulator (LSBSS) utilizes an explosive charge to drive a plate to which the materiel is mounted. This is considerably less expensive than Procedure I. 

Procedure III – Light Weight Shock Machine
For assemblies weighing less that 250 lbs, a Light Weight Shock Machine from MIL-S-901D can be used.

Procedure IV – Medium Weight Shock Machine
For assemblies weighing less that 5000 lbs, a Medium Weight Shock Machine from MIL-S-901D can be used.

Procedure V – Drop Table
Light weight components, usually weighing less than 40 lbs, can be tested using a drop table.  The commonly available drop test machine is the least expensive and most accessible test technique.

Test Evaluation

After the testing, evaluate the components for damage and proper operation.

MIL-STD-810G – Part 24 – (Ballistic Shock) Method 522

MIL-STD-810G – Part 23 – (ICING/FREEZING RAIN) Method 521.3

MIL-STD-810G covers Ice and Freezing Rain in Method 521.3.  521.3 is relatively short at 7 pages and covers the effects of ice and freezing rain on the operational capability of material.  Also included is evaluating the effectiveness of de-icing equipment and techniques. 

Icing and freezing rain occurs when the air is saturated with super-cooled water droplets which forms rime ice and/or glaze ice.  Rime ice is a white or milky accumulation and is lighter, softer and less transparent than glaze ice.  Glaze ice is a generally clear hard coating of ice.  Rime forms when super-cooled water drops freeze on exposed surfaces.  Glaze ice forms from a film of super-cooled water vapor freezing as a layer.

Method 521.3 can be applied to any material exposed to freezing rain conditions including large items such as vehicles, aircraft, and ships.  This method generally does not apply to electronic equipment such as rackmount computer systems.

Some adverse effects of ice and freezing rain include:

a. Binds moving parts together.
b. Adds weight to radar antennas, aerodynamic control surfaces, helicopter rotors, etc.
c. Increases footing hazards for personnel.
d. Interferes with clearances between moving parts.
e. Induces structural failures.
f. Reduces airflow efficiency as in cooling systems or filters.
g. Impedes visibility through windshields and optical devices.
h. Affects transmission of electromagnetic radiation.
i. Provides a source of potential damage to materiel from the employment of mechanical, manual, or chemical ice removal measures.
j. Reduces efficiency of aerodynamic lifting and control surfaces.
k. Reduces (aircraft) stall margins.

The principle goal of the test is to have super-cooled liquid water droplets impinge on the test item and freeze in place.  A chamber of suitable size capable of maintaining a temperature of -10 deg C (14 deg F) with the ability to spray cooled water on the test item is required.  The test can be performed outdoors if the ambient conditions are prone to icing.  Test conditions can be adjusted such as temperature, droplet size, water temperature, etc., to achieve satisfactory icing conditions.

MIL-STD-810G – Part 23 – (ICING/FREEZING RAIN) Method 521.3

MIL-STD-810G – Part 22 – (Temperature, Humidity, Vibration, and Altitude) Method 520.3

MIL-STD-810G covers the synergistic effects of Temperature, Humidity, Vibration and Altitude in Method 520.3. Method 520.3 is comprised of 22 pages.

810G covers each of these environmental factors individually in the following Methods:

Method 500.5 – Altitude

Method 501.5 – High Temperature

Method 502.5 – Low Temperature

Method 507.5 – Humidity

Method 514.6 – Vibration

It should be noted the above Methods are specific to the environmental factor being tested. For example, samples might be vibrated but will be done so at a benign temperature in a climate controlled facility. Conversely, a temperature test is done in a chamber mounted to the floor with no external vibration imparted on the sample.

Materials can exhibit much different characteristics at different temperatures such as thermal expansion or contraction causing binding, the material becoming much more brittle at a low temperature or much more ‘loose’ at high temperatures. This method is particularly useful in evaluating aircraft which may start a flight cycle hot from sitting on the ramp in the Middle East, climb to altitude with an external temperature of -65 deg F at 35,000 feet with vibration and shock from the engine and turbulence. Another example could be the SR71 which has to fuel immediately after take-off, then speed up to heat the air frame to seal the tanks due to thermal expansion.

Rugged computer systems, especially in flight environments, can be highly susceptible to the combined effects of altitude (less effective cooling), temperature (thermal contraction or chip failure), vibration (damage to components) and humidity (shorting).

Method 520.3 specifies tailoring the process to determine where these combined forcing functions of temperature, humidity, vibration, and altitude are foreseen in the life cycle of the materiel in the real world.

Some example failures are:

a. Shattering of glass vials and optical materiel. (Temperature/Vibration/Altitude)

b. Binding or loosening of moving parts. (Temperature/Vibration)

c. Separation of constituents. (Temperature/Humidity/Vibration/Altitude)

d. Performance degradation in electronic components due to parameter shifts. (Temperature/Humidity)

e. Electronic optical (fogging) or mechanical failures due to rapid water or frost formation.

(Temperature/Humidity)

f. Cracking of solid pellets or grains in explosives. (Temperature/Humidity/Vibration)

g. Differential contraction or expansion of dissimilar materials. (Temperature/Altitude)

h. Deformation or fracture of components. (Temperature/Vibration/Altitude)

i. Cracking of surface coatings. (Temperature/Humidity/ Vibration/Altitude)

j. Leakage of sealed compartments. (Temperature/Vibration//Altitude)

k. Failure due to inadequate heat dissipation. (Temperature/Vibration /Altitude)

The Method provides for three Procedures:

I. Engineering Development

Used to help find defects in a new design in the development state. The procedure is accelerated and failure-oriented to uncover design defects.

II. Flight or Operational Support

Used in preparation for, during and after flight or operational testing. Not accelerated and the test item can be moved from the test vehicle to the lab interchangeably to help determine failures or deficiencies.

III. Qualification

Used to demonstrate compliance with all contract requirements. Usually an accelerated test that emphasizes the most significant environmental stress conditions.

Follows is an example test profile combining all the environmental factors into one test cycle.

MIL-STD-810G – Part 22 – (Temperature, Humidity, Vibration, and Altitude) Method 520.3

Electronic Salesmasters Now Repping Chassis Plans

Continuing to expand our sales channels, we’ve added Electronic Salesmasters, Inc.,  as sales representatives.  ESI will represent Chassis Plans in West Virginia, Ohio, Indiana, Michigan and Kentucky.

 

ESI has a strong presence in:

• Industrial


• Appliance


• Communications


• Transportation


• Military


• Instrumentation


• Datacom


• Medical


• Automotive

 

ESI is characterized by sound financial management, motivation and plans for business continuity. They pride themselvesin being “businessmen in sales”, not just salesmen in business. ESI provides stability, trust and confidence that enhances their relationships with customers throughout the territory.

 

Additional information is available at www.chassis-plans.com/representatives.html.

Electronic Salesmasters Now Repping Chassis Plans

Adds Cornerstone and Midtec as sales representatives

Map of Chassis Plans Sales Reps

We’re please to announce the appointment of two new sales representative groups.

 

Cornerstone Technical Sales will cover Florida with an office in Palm Harbor, FL.  Cornerstone is available at www.ctsrep.com.

 

Midtec Associates covers Missouri, Southern Illinois, Iowa, Nebraska and Kansas.  Midtech has offices in Lenexa, KS, and St. Louis.  Midtech can be reached at www.midtec.com.

 

Both these companies have extensive experience in industrial and military computing and will bring a local presence to these states to offer our customers on-site assistance and product expertise.

Adds Cornerstone and Midtec as sales representatives

The 2016 Federal Budget has Healthy Increases for R&D and Defense

The 2016 US budget was released in early February by the President. In this budget there are increases in R&D spending in general and the defense budget. For the past several years, since the Budget Control Act (BCA) was passed in 2011, the Defense budget has been decreasing as has the overall spending on R&D in general. The 2016 budget is the start of a turnaround in both Defense related R&D as well as general Science and Technology R&D spending. Whether the proposed budget will pass the scrutiny of congress is another matter.

 

The military budget has been teetering on the brink of disaster for the past several years. With the emphasis on overseas contingency operations (OCO) and the effects of the BCA and sequestration the military has been forced to review every program and every expense for the past five years. This review has not been necessarily bad. The top-down and bottom-up review has forced each branch of the service to focus on what is important for the future needs of the US foreign and domestic policies.

 

The following chart shows the level of defense funding for the past several years as well as the projected spending for the next five years. Although the proposed budget for 2016 of $585B is below the 2010-11 level it is a significant increase from 2015. The majority of the Defense budget is for operations, facilities and personnel but there is still a significant portion allocated for procurement and R&D. The 2016 budget provides for $177.5 billion in procurement and research spending, an increase of $20.4 billion, or 13 percent, over the 2015 budget.

 

 

The Pentagon wants to spend $107.7 billion on procurement and $69.8 billion on research and development, with $12.3 billion falling within that for science and technology spending. The biggest investments include $48.8 billion for aircraft, $25.6 billion for shipbuilding, $8.2 billion for ground systems and $11.9 billion for missiles and munitions.

 

		Procurement and R&D Funding by Branch
Army			Navy			Air Force
Total	$126.5B		Total	$161B		Total	$122.2B
R&D	$6.9B		R&D	$17.9B		R&D	$18B
%	5.40%		%	11%		%	14.70%

 

For the Army, there are significant upgrades planned for existing vehicles such as Abrahams, Bradley and Striker vehicles. There is also funding for a Humvee replacement. A lot of the upgrades are for better computer and communications systems. For procurements, the Army is targeting Blackhawk and Apache attack helicopters, Chinook helicopters, WIN-T communication systems, and the MQ-1 Gray Eagle, a dual-purpose weaponized/ISR unmanned aircraft.  Areas in RDT&E specifically identified by the Army include basic research, applied research, advanced technology development, demonstration and validation.

 

The Air Force will fund R&D in nuclear operations to reduce risks to ground-based strategic defense such as ICBM guidance and propulsion, provide for B-2 fleet defensive management system upgrades related to attack capability and investments in domestic launch systems. They will invest in future capabilities and technologies to support adaptive engine transition program testing and provide critical command and control with better ISR capabilities and maintain its commitment to recapitalize the Air Force to sustain designs and developments for the KC-46 (an aerial refueling and transport vehicle), the F-35 Joint Strike Fighter, the LRS-B (a next generation stealth bomber), and a combat rescue helicopter.

 

The Navy in recent years has emphasized its desire for more unmanned systems plus next-generation strike aircraft to be interchangeable between manned and unmanned.  An example is the UCLASS, or unmanned carrier-launched airborne surveillance and strike program.  The Marine Corps R&D will focus on amphibious combat vehicles. The Marines have already awarded contracts to two vendors for procurement of additional vehicles.  Also, in the cyber domain, networks such as Naval Enterprise Networks (NGEN) and the Consolidated Afloat Networks and Enterprise Services (CANES) will see more investment as will combat and controls systems for tactical platforms.

 

All of the branches of the military are also increasing the funding for cyber programs and big data programs. Included is funding for security from cyber attacks from internal and external sources.

 

Overall the 2016 budget is encouraging for technology companies. With more R&D spending there are more opportunities to sell existing products as well as get funding for innovations and product enhancements. The question is will congress fight the budget since it is well over the BCA cap or will congress realize that the investment is needed for the future of technology growth and modernization of both the military and NASA. Hopefully the later, but we will probably have to wait until at least September 30th to get an answer.

 

We at Chassis Plans are already seeing a much-increased level of quote activity and programs which have been on hold being released.  There is a general feeling in Government procurement that the worst is behind us and that much needed money is being made available.  Based on our first quarter performance, we’re expecting a banner year.  Our systems form the foundation for many military programs so an increase in our business is a leading indicator for the health of the sector.

 

The 2016 Federal Budget has Healthy Increases for R&D and Defense

Mike McCormack Joins Chassis Plans as President

Mike McCormack

Chassis Plans is pleased to announce the appointment of Mike McCormack as President. Mike brings a comprehensive understanding of the Defense and Industrial markets through his past experience in senior management positions at IntelliPower,  Johnathan Engineered Solutions and Emerson.  The organizations managed, designed and manufactured a wide range of products including power conversion systems, electronic components, mechanical components and outside plant equipment to the Defense, Aerospace, Communications and Oil and Gas Exploration. Mike also previously served in the USAF as an Airborne Command Post Communications Systems Engineer on board EC-135’s.

 

With Mike on board Chassis Plans will continue with being the leader in the design and development of world class Rugged Custom Military and Industrial grade Computers, Monitors and Keyboards through innovative designs and outstanding customer service and support.

Mike McCormack Joins Chassis Plans as President

Is there an Engineering Graduate Shortage?

At Chassis Plans we have been supporting engineering students for several years via scholarships and hiring students as interns. As we go into the future there is a strong need for technologists to support future development in all fields of science and engineering.

Courtesy of S. Harris – http://www.sciencecartoonsplus.com

 

Is there a real shortage of Engineers and Scientists in the current marketplace? In 2008 the Bureau of Labor estimated there would be a shortage of 160,000 engineers and scientists by 2016. However, some of the more recent studies are showing that there is not a shortage of engineering talent but the issue is whether the math and science education in the United States requires development in both primary and secondary schools. What is being done about it and is there a light at the end of the tunnel?

 

Of all the reports, both pro and con, on the engineer shortage, the one thing that is agreed on is that students today need to develop better skills in Science, Technology, Engineering and Math (STEM). No matter what career path is taken by today’s students, knowledge of STEM skills will be an aid to better opportunities. In a 2011 article for the Wall Street Journal, Norman Augustine, former chairman and CEO of Lockheed Martin stated – “In my position as CEO of a firm employing over 80,000 engineers, I can testify that most were excellent engineers. But the factor that most distinguished those who advanced in the organization was the ability to think broadly and read and write clearly.”

 

The good news is that STEM programs are in almost all high schools and more primary schools. STEM programs are multidiscipline based incorporating the integration of disciplinary knowledge into a new whole. Technology helps us communicate; math is the language, science and engineering are the processes for thinking and all this leads to creativity and innovation.

 

Courtest of Ed Stein – http://edsteinink.com

 

In the past, there were huge government programs, such as the space program, that captured the imagination of many students and helped keep enrollment in engineering and science programs high. Today the government is sponsoring STEM programs to excite students. There are engineering-oriented competitions such as robotics competitions hosted by both the government and private companies.

 

There are resources outside of the normal school campus that can also help excite students to take an interest in science. Three of the key outside influences that can have an effect on students are:

 

• The Internet


• Transformation of public libraries


• Open source software and hardware development.

 

The information explosion created by the internet has greatly surpassed what has been available in the past. The challenge is to be able to discern what information is useful and what is not. In the past a student would have to go to the library and look up the topic of interest using the sources available in that library. If a student lived in a small town the resources were limited. The internet provides an almost unlimited number of sources on any topic. So does that make the local library an obsolete facility?

 

Computer Lab in McAllen Texas Library

 

The function of the library is changing. Libraries are moving away from just being a place where books are stored. Today’s libraries are embracing the internet culture and getting involved with STEM programs. More and more local libraries are adding Makers labs, computer labs and adding equipment such as 3D Printers that can be used by the public. One example is the new library in McAllen,Texas, where an old Wal-Mart building was turned into the largest single floor library in the United States. As part of the makeover computer labs were added as well as meeting rooms for STEM and Makers events.

 

Another driver of technology education is the concept of open source development projects which generate free or very low cost software and hardware solutions. Using open source developed products, schools, as well as individuals, can have hands on experience developing robotics, graphics applications and other technology projects.

 

The support of STEM programs by government agencies, schools and companies will go a long way to improving the skills of students in science, math and engineering and help to provide sufficient technology workers for the future.

 

Chassis Plans will continue to help with additional scholarships, equipment donations, and Intern programs.

Is there an Engineering Graduate Shortage?

Chassis Plans Awards Winter 2015 Leadership in Engineering Scholarship

Chassis Plans Winter 2014 Leadership in Engineering Scholarship Winner – Grace Bushnell

Chassis Plans is pleased to announce Grace Bushnell won the Winter 2015 Chassis Plans Leadership in Engineering Scholarship.

 

Grace’s outstanding essay is located here.

 

Grace is a second year PhD student in Biomedical Engineering at the University of Michigan. Grace is originally from a small farming town in Northern Illinois. She received her Bachelor of Science in Biomedical Engineering in 2013 and Master of Science in Biomedical Engineering in 2014, both from Northwestern University.

 

Her undergraduate research was focused on endovascular coiling of aneurysms and mussel-inspired biomaterials to serve as surgical adhesives. Her current graduate research is focused on developing biomaterials for the study, detection, and treatment of metastatic cancer.

 

Grace plans to work as a post-doctoral fellow following her PhD and hopes to eventually join academia as a faculty member to both teach and develop a biomaterials research program.

Chassis Plans Awards Winter 2015 Leadership in Engineering Scholarship

2015 Chassis Plans Calendars are Here

Chassis Plans’ 2015 Industrial Computer Calendar

Announcing the Chassis Plans’ 2015 calendar is here.  These are free to qualified users in the industrial and military computer markets.  Go to www.chassis-plans.com/industrial-computer-calendar.html to request your own copy.

 

This is a beautiful large format 11 x 17-inch work of art that everybody loves.

2015 Chassis Plans Calendars are Here

ISO 9001:2008 Surveillance Audit

Chassis Plans just completed its most recent two-day ISO 9001:2008 surveillance audit by the registrar International Standards Authority Inc.

 

Periodic surveillance audits are a requirement for maintaining ISO 9001:2008 registration.

 

External surveillance audits verify that the organization has an effective quality management system that meets all the requirements of the internationally recognized ISO 9001:2008 standard.

ISO 9001:2008 Surveillance Audit

RAID Data Storage

Introduction

 

RAID is an acronym which stands for Redundant Array of Independent Disks.  It combines multiple disk drives into a logical unit.  As its name implies, it provides redundancy which allows continuous access to data should a disk drive fail.  When a server wants to store data it sends a write command to the storage array with the data to be stored and a logical unit number (LUN) identifying where to place the data.  When the server wants to retrieve that data, it sends a read request to the storage array, again referencing the LUN from which to retrieve the data.  The server doesn’t realize that the data isn’t being stored on a disk drive but on a series of disk drives.  It doesn’t really care just as long as it can store and retrieve the data.  A RAID storage array is a virtual storage device.  Although virtualization in the server and network space is somewhat new, virtualization in the data space has been around for quite some time.

 

RAID Levels

 

Depending on the level of redundancy and performance required, data is distributed across the disk drives in one of several ways, most of which provide protection against sector or whole drive failures.  Let’s take a look at the more popular RAID levels.

 

RAID 0 – RAID 0 is a bit misleading as it provides no redundancy at all and as a result, no protection against drive failures.  RAID 0 is really a data distribution scheme to increase write performance.   In this scheme, data is stripped across a set of disk drives so that each drive only has to store a portion of the data and, therefore, the data as a whole is written in less time than if it were written to a single disk drive.  The downside to RAID 0 is the opportunity for a disk failure is doubled..

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RAID 1 – RAID 1 requires at least two drives and provides redundancy by mirroring the data on a second drive or on a second set of drives.  Therefore, if a drive fails, it is abandoned and the data is referenced from its mirrored drive.  Subsequent writes are then only written to the surviving drive pair until the failed drive is replaced and rebuilt with the data from the surviving drive.  Should the surviving drive fail before the failed drive is replaced and reloaded with the mirrored data, an unrecoverable error is said to have occurred.

 

 

 

 

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RAID 10 – RAID 10 is a combination of RAID 1 and RAID 0.  In RAID 10, data is stripped across a set of disk drives and the data on that set of drives is mirrored on another set of disk drives.  RAID 10 gives the system higher performance writes, as in RAID 0, as well as data protection from mirroring as in RAID 1.  The downside to RAID 10 is the cost of a larger set of disk drives.

 

RAID 5 – RAID 5 solves the higher cost of the combined performance and reliability found in RAID 10.  In RAID 5 data is distributed across a set of drives, as in RAID 0, yielding the higher performance.  However, the cost of redundancy is minimized by requiring only one extra disk drive.  This drive is for parity data.  When data is stripped across the drive set, parity is also generated by an exclusive OR Boolean function applied to each data element and saved on the parity drive.  Should a drive fail, it can be rebuilt with the data from the remaining drives.  The missing data element is regenerated using the information in the parity drive.  This not only allows the system to rebuild a replacement drive but to also operate without the replacement drive, albeit at a slower read pace as the system must regenerate the missing data on each read.  Although an extra drive is used for parity, the parity element is really distributed throughout the drive set so no one drive contains only parity information as can be seen in the RAID 5 diagram below.  The downside to RAID 5 is that each disk drive is read quite extensively to rebuild a failed drive.  If the heavy reading workload causes a second drive to fail all data now becomes unrecoverable. Today’s single disk drive capacity is up to 4 terabytes of data.  Rebuilding a 4 terabyte drive can take many hours.  The larger the drive, the longer the rebuild time, and the more likely the system will lose a second drive resulting in data loss.

 

RAID 6 – RAID 6 was developed to overcome the shortcoming of RAID 5.  If using large capacity drives, it is recommended that RAID 6 be implemented.  RAID 6 used double parity so that two drives can fail and the system still has enough information to rebuild both drives.  As in RAID 5, the parity is distributed throughout the drive set.

 

 

 

 

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JBOD – JBOD is an acronym that stands for Just a Bunch Of Disks.  It’s not a RAID level at all but is worth addressing in the RAID discussion.  JBODs address the need for capacities greater than can be found on a single disk drive but provide nothing in the way of redundancy.  There is no algorithm support for stripping, mirroring, or parity.  It’s simply an inexpensive way to provide for large capacity storage.

 

Application

 

Storage arrays with various RAID levels are used extensively in many applications today.  It is often used in deployed applications in rugged environments for data acquisition.  The most common environment is on an airborne platform or in a ground station to received collected data from an airborne platform.  Data collection sensors have evolved to provide greater resolution which means more data to store.  At the same time, disk drive capacities have increased while costs have declined.  This has allowed RAID to become the technology of choice for data acquisition applications.

 

Chassis Plans offers rugged storage arrays compliant and certified to the rugged MIL-STD-810G standard providing assurance that your data storage is protected in certain harsh environments.  The Chassis Plans rugged storage arrays support all RAID levels discussed here and are housed in a 2U high 19 inch rack mount enclosure with capacities up to 48 terabytes. For greater capacities, up to seven additional enclosures can be added to extend the total capacity under a single RAID group to 384 terabytes of data.

 

 

Graphics for this blog article attributed to Colin M.L. Burnett.

 

 

RAID Data Storage

MIL-STD-810G – Part 20 (Acidic Atmosphere) Method 518.1

MIL-STD-810G covers exposure to an Acidic Atmosphere in Method 518.1. Acidic atmospheres are of increasing concern, especially for materiel in the vicinity of industrial areas or near the exhausts of fuel burning devices. Method 518.1 is comprised of 7 pages.

 

This Method is used to determine the resistance of materials and protective coatings to corrosive atmospheres. This Method is appropriate for materiel likely to be stored or operated in areas where acidic atmospheres exist, such as industrial areas or near the exhausts of any fuel-burning device.

 

Note this method is not a replacement for the salt fog method, nor is it suitable for evaluating the effects of hydrogen sulfide that readily oxidizes in the test environment to form sulfur dioxide. Caution: Although salt fog chambers are usually used for this test, introducing an acidic or sulfur dioxide atmosphere in a salt fog chamber may contaminate the chamber for future salt fog tests.

 

Some problems as a result of an acidic environment include:

 

1. Chemical attack of surface finishes and non-metallic materials.


2. Corrosion of metals.


3. Pitting of cement and optics.

 

This Method should be applied late in a products test cycle. Also, separate items should be tested for Salt Fog.

 

Two test durations are suggested. For infrequent periods of exposure, three 2-hour spraying periods with 22 hours storage after each is sufficient. To represent approximately 10 years natural exposure in a moist, highly industrial area, or a shorter period in close proximity to vehicle exhaust systems, particularly ship funnel exhausts where the potential acidity is significantly higher, four 2-hour spraying periods with 7 days storage after each is sufficient.

 

The actual test is similar to Method 509.5 (Salt Fog) in that the acid solution is atomized into a fog and blown through a test chamber.

 

MIL-STD-810G – Part 20 (Acidic Atmosphere) Method 518.1

MIL-STD-810G – Part 19 (Pyroshock) Method 517.1

MIL-STD-810G covers Pyroshock in Method 517.1. Pyroshock is a high intensity, short duration shock event caused by the detonation of a pyrotechnic device on adjacent structures. Pyroshock is a physical phenomenon characterized by the overall material and mechanical response at a structure point from either (a) an explosive device, or (b) a propellant activated device. Method 517.1 is comprised of 23 pages.

 

Method 517.1 is not intended to test material exposed to external explosions.

 

Use this method to evaluate materiel likely to be exposed to one or more pyroshocks in its lifetime.

 

In general, the pyroshock sources may be described in terms of their spatial distribution – point sources, line sources and combined point and line sources. Point sources include explosive bolts, separation nuts, pin pullers and pushers, bolt and cable cutters and pyro-activated operational hardware. Line sources include flexible linear shape charges (FLSC), mild detonating fuses (MDF), and explosive transfer lines. Combined point and line sources include V-band (Marmon) clamps.

 

Pyroshocks are generally within a frequency range between 100 Hz and 1,000,000 Hz, and a time duration from 50 microseconds to not more than 20 milliseconds. Acceleration response amplitudes to pyroshock may range from 300 g to 300,000 g.

 

Pyroshock usually exhibits no momentum exchange between two bodies (a possible exception is the transfer of strain energy from stress wave propagation from a device through structure to the materiel). Pyroshock results in essentially no velocity change in the materiel support structure.

 

The characteristics of pyroshock are:

1. near-the-source stress waves in the structure caused by high material strain rates (nonlinear material region) propagate into the near-field and beyond;


2. high frequency (100 Hz to 1,000,000 Hz) and very broadband frequency input;


3. high acceleration (300 g to 300,000 g) but low structural velocity and displacement response;


4. short-time duration (< 20 msec);


5. high residual structure acceleration response (after the event);


6. caused by (1) an explosive device or (2) a propellant activated device (releasing stored strain energy) coupled directly into the structure; (for clarification, a propellant activated device includes items such as a clamp that releases strain energy causing a structure response greater than that obtained from the propellant detonation alone);


7. highly localized point source input or line source input;


8. very high structural driving point impedance (P/v, where P is the large detonation force or pressure, and v, the structural velocity, is very small). At the pyrotechnic source, the driving point impedance can be substantially less if the structure material particle velocity is high;


9. response time histories that are random in nature, providing little repeatability and substantial dependency on the materiel configuration details;


10. response at points on the structure that are greatly affected by structural discontinuities;


11. materiel and structural response that may be accompanied by substantial heat and electromagnetic emission (from ionization of gases during explosion).

 

Examples of electronic problems associated with pyroshock follow, but the list is not intended to be all-inclusive.

1. materiel failure as a result of destruction of the structural integrity of microelectronic chips;


2. materiel failure as a result of relay chatter;


3. materiel failure as a result of circuit card malfunction, circuit card damage, and electronic connector failure. On occasion, circuit card contaminants having the potential to cause short circuits may be dislodged under pyroshock.


4. materiel failure as a result of cracks and fracture in crystals, ceramics, epoxies, or glass envelopes.

 

MIL-STD-810G – Part 19 (Pyroshock) Method 517.1

MIL-STD-810G – Part 18 (Shock) Method 516.6

MIL-STD-810G covers shock in Method 516.6. Shock is an infrequent single pulse acceleration with a narrow pulse width imparted to a device. Method 516.6 is one of the more complicated Methods comprised of 38 pages. In addition there are three Annexes:

 

Annex A – Statistical Considerations (8 pages)

Annex B – Effective Shock Duration (4 pages)

Annex C – Autospectral Density (4 pages)

 

Method 516.5 is one of the more widely performed Methods, often in conjunction with Method 514.6 (Vibration).

 

Shock tests are performed to:

1. provide a degree of confidence that material can physically and functionally withstand the relatively infrequent, non-repetitive shocks encountered in handling, transportation, and service environments. This may include an assessment of the overall material system integrity for safety purposes in any one or all of the handling, transportation, and service environments;


2. determine the material’s fragility level, in order that packaging may be designed to protect the material’s physical and functional integrity; and


3. test the strength of devices that attach material to platforms that can crash.

 

A shock environment is generally limited to a frequency range not to exceed 10,000 Hz, and a time duration of not more than 1.0 second. (In most cases of mechanical shock the significant material response frequencies will not exceed 4,000 Hz and the duration of material response will not exceed 0.1 second.) The material response will, in most cases, be highly oscillatory, of short duration, with a substantial initial rise time with large positive and negative peak amplitudes.

 

Shock is the term applied to a comparatively short time (usually much less than the period of the fundamental frequency of the material) and moderately high level (above even extreme vibration levels) force impulse applied as an input to the material.

 

Failure modes to shock events include:

 

1. material failure as a result of increased or decreased friction between parts, or general interference between parts;


2. changes in material dielectric strength, loss of insulation resistance, variations in magnetic and electrostatic field strength;


3. material electronic circuit card malfunction, electronic circuit card damage, and electronic connector failure. (On occasion, circuit card contaminants having the potential to cause short circuit may be dislodged under material response to shock.);


4. permanent mechanical deformation of the material as a result of overstress of material structural and non-structural members;


5. collapse of mechanical elements of the material as a result of the ultimate strength of the component being exceeded;


6. accelerated fatiguing of materials (low cycle fatigue);


7. potential piezoelectric activity of materials, and


8. material failure as a result of cracks in fracturing crystals, ceramics, epoxies, or glass envelopes.

 

Method 516.6 includes eight procedures:

 

Procedure I – Functional Shock

Intended to test material (including mechanical, electrical, hydraulic, and electronic) in its functional mode (as installed in the field) and to assess the physical integrity, continuity and functionality of the material to shock.

 

Procedure II – Material to be packaged

The intent of this test is to ensure the functionality of materiel after it has been inadvertently dropped before, during, or after a packaging process.

 

Procedure III – Fragility

Used to determine a material’s ruggedness or fragility so that packaging can be designed for the material, or so the material can be redesigned to meet transportation and/or handling requirements.  This test is designed to build up in severity until a test item failure occurs, or a predetermined goal is reached.

 

Procedure IV – Transit Drop

Intended for material either outside of or within its transit or combination case, or as prepared for field use (carried to a combat situation by man, truck, rail, etc.).

 

Procedure V – Crash Hazard Shock Test

Intended for material mounted in air or ground vehicles that could break loose from its mounts, tiedowns or containment configuration during a crash and present a hazard to vehicle occupants and bystanders.

 

Procedure VI – Bench Handling

Intended for material that may typically experience bench handling, bench maintenance, or packaging.

 

Procedure VII – Pendulum Impact

Intended to test the ability of large shipping containers to resist horizontal impacts, and to determine the ability of the packaging and packing methods to provide protection to the contents when the container is impacted.

 

Procedure VIII – Catapult Launch/Arrested Landing.

Intended for material mounted in or on fixed-wing aircraft that are subject to catapult launches and arrested landings.

 

 

MIL-STD-810G – Part 18 (Shock) Method 516.6

MIL-STD-810G – Part 17 (Acoustic Noise) Method 515.6

MIL-STD-810G covers Acoustic Noise Susceptibility in Method 515.6. This Method tests material’s response to very loud noise such as from a jet engine, rocket engine (think Shuttle launch) or power plant. This is not a test to determine how much noise an item generates. Method 515.6 is 8 pages with two Annexes totaling 7 pages.

 

As with most of the Methods in 810G, tailoring is essential for this Method to have any meaningful results.

 

The acoustic noise test is performed to determine the adequacy of materiel to resist the specified acoustic environment without unacceptable degradation of its functional performance and/or structural integrity. It is applicable to systems, sub-systems and units that must function and survive in a severe acoustic environment.

 

The acoustic noise environment is produced by any mechanical or electromechanical device capable of causing large airborne pressure fluctuations. In general, these pressure fluctuations are of an entirely random nature over a large amplitude range (5000 Pa to 87000 Pa), and over a broad frequency band extending from 10 Hz to 10000 Hz. When pressure fluctuations impact materiel, generally, a transfer of energy takes place between the energy (in the form of fluctuating pressure) in the surrounding air to the strain energy in materiel. This transfer of energy will result in vibration of the materiel, in which case the vibrating materiel may re-radiate pressure energy, absorb energy in materiel damping, or transfer energy to components or cavities interior to the materiel.

 

Some of the effects of a high acoustic environment include:

 

1. Wire chafing


2. Component acoustic and vibratory fatigue


3. Component connecting wire fracture


4. Cracking of printed circuit boards


5. Failure of wave guide components


6. Intermittent operation of electrical contacts


7. Cracking of small panel areas and structural elements


8. Optical misalignment


9. Loosening of small particles that may become lodged in circuits and mechanisms


10. Excessive electrical noise

 

As with Method 514.6 (Vibration), loud acoustic environments can have an effect on the material that may change the material’s response to other tests. For example, noise can cause a vibration is a panel that cracks the finish which would cause a failure of the Salt Fog test. This test should be performed first or in conjunction with vibration testing.

 

The Method provides three procedures:

 

Procedure I – Diffuse Field Acoustic Noise.

A uniform intensity shaped spectrum of acoustic noise that impacts all the exposed materiel surfaces is provided. This would be a typically noisy environment with broadband widespread noise such as produced by aerospace vehicles or power plants.

 

Procedure II – Grazing Incidence Acoustic Noise.

Includes a high intensity, rapidly fluctuating acoustic noise with a shaped spectrum that impacts the materiel surfaces in a particular direction – generally along the long dimension of the materiel. An example is high speed airflow over the skin of an aircraft or airflow around a missile hanging on a wing pylon.

 

Procedure III – Cavity Resonance Acoustic Noise.

The intensity and, to a great extent, the frequency content of the acoustic noise spectrum is governed by the relationship between the geometrical configuration of the cavity and the materiel within the cavity. An example would be an open weapons bay on a fighter where the air in the cavity is turbulent. This can induce vibration in adjacent aircraft structures and equipment such as bombs or missiles still in the bay.

 

 

MIL-STD-810G – Part 17 (Acoustic Noise) Method 515.6