MIL-STD 810, Method 516, Shock Testing Overview

MIL-STD 810, Method 516, Shock Testing Procedure I – Functional Shock

Procedure II of Method 516 is used to evaluate the response of products to transportation environments that cause a repetitive shock load such as those occurring from ground vehicle shipping. This procedure uses the classical terminal peak sawtooth to characterize the transportation scenario.  Transportation shocks are typically repetitive low amplitude shock impulses. This procedure would be used in addition to shipping vibration testing and is not meant to be a substitute.

The items are usually tested in a packaged or unpackaged configuration in a non-operational state.  The shock test sequence is defined in Table 516.7-VI in Procedure II.  Normally, either the On-Road or Off-Road shock sequence is performed, not both.  The sequence in Table 516.7-VI is repeated along each applicable axis and direction as specified in the test plan.  After the shock testing is complete, operation of the product is verified and it is inspected for visual damage.

Table 516.7-VI Transportation shock test sequence^1,2,3

Note 1: The shocks set out in Table 516.7-VI must always be carried out together with ground transportation vibration testing as specified in Method 514.7, Category 4 and/or Category 20.

Note 2: The above tabulated values may be considered for both restrained cargo and installed materiel on wheeled and tracked vehicles. Transportation shock associated with two-wheeled trailers may exceed off-road levels as defined.

Note 3: The shock test schedule set out in Table 516.7-VI can be undertaken using either terminal peak sawtooth pulses applied in each sense of each orthogonal axis, or a synthesis based on the corresponding SRS that encompasses both senses of each axis.

Note 4: The above number of shocks is equivalent to the following distances: a) On-road vehicles: 5000 km; b) Off-road vehicles: 1000 km. If greater distances are required, more shocks must be applied in multiples of the figures above.

For more information on Shock Testing or other testing services, contact DES or call 610.253.6637.

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DES recently completed RTCA DO-160G vibration and shock testing for DB Integrations in Allentown PA, a manufacturer of aircraft components.  The testing was performed on ARINC 600 Mounting Trays.  The trays were vibration tested for use on fixed wing aircraft (Section 8, Category S) and for use on helicopters (Section 8, Category U2).  Shock testing was also performed per Section 7, Category A in RTCA DO-160G.  The trays withstood the rigorous testing that took 3 days to complete.

DES has extensive experience performing testing to standards such as RTCA DO-160G.  For more information contact DES or call 610.253.6637. 

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MIL-STD 810, Method 516, Shock Testing Overview

Shock testing according to Procedure I of MIL-STD 810, Method 516 is intended to test products while they are operating to see if any functional problems occur and to determine if they survive without damage.  The applied shocks usually represent those that may be encountered during operational service.  This article will focus on the shock test condition when measured field data is not available and the testing will use classical shock impulses.  The terminal peak sawtooth is the default classical shock pulse to be used for this condition.  Figure 516.7-10 from MIL-STD-810 shows its shape and tolerance limits.  Table 516.7-IV contains the terminal peak sawtooth default test parameters for Procedure I -Functional Test.  In limited cases a half sine shock impulse is specified.  Its shape and tolerance limits are shown in Figure 516.7-12.

The product should be mounted to the machine or fixture as it would in normal use.  So, if it is bolted using a flange, then it should be attached to a fixture using this flange with the same size and number of bolts.

The typical shock testing procedure is to first perform calibration shocks using a mass similar in size, weight and center of gravity (CG) of the product to be tested.  Most commonly a non-working mechanical product is used for this purpose.  Once the desired shock requirements are met with the calibration mass, the mass is removed and the product to be tested is installed on the shock test machine or fixture.  Since this is a functional shock, the product must be operating and monitored for anomalies.   Therefore, before the shock is applied, the product must be energized and the monitoring equipment should be operating.  After each shock, operation of the test item is verified and it is inspected for visual damage.

The most common requirement is to perform 3 shocks along both the positive and negative directions along 3 orthogonal axes.  This is a total of 6 directions and 18 shocks.  When setting up to perform shocks in each direction, calibration shocks with the mass simulant are performed first because the weight, CG and product response could require different settings on the shock machine.  The shocks are performed along both the positive and negative directions of each axis because classical shocks are single polarity.

For more information on Shock Testing or other testing services, contact DES or call 610.253.6637.

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MIL-STD-810 is a public military test standard that is designed to assist in the environmental engineering considerations for product design and testing.  For the purposes of this blog series we will focus on Method 516.7, Shock Testing.

The purpose of shock testing is to:

1. Evaluate if a product can withstand shocks encountered in handling, transportation, and service environments
2. Determine the product’s fragility level
3. Test the strength of devices during a crash situation to verify that parts do not break apart, eject and become a safety hazard

Shock testing failures are a function of the amplitude, velocity, and the duration of the impulse.  If a product has a resonance frequency that corresponds with the frequency of the shock, the effects of the shock will be magnified.

Typically shocks in Method 516.7 are limited to a frequency range not to exceed 10,000 Hz, and a duration of not more than 1.0 second.  Method 516.7 contains eight test procedures which are summarized in Table 516.7-I.

Table 516.7-I from MIL-STD-810G w/Change 1

The differences among procedures is briefly defined below:

1. Procedure I – Functional Shock. Procedure I is intended to test products while they are operating to see if any functional problems occur and to determine if they survive without damage. The applied shocks usually represent those that may be encountered during operational service.
2. Procedure II – Transportation Shock. Procedure II is used to evaluate products for repetitive shocks from transportation environments. This procedure typically uses a classical terminal peak sawtooth impulse to simulate transportation shocks.
3. Procedure III – Fragility. Procedure III is used to determine what shock conditions will cause a product to stop operating, degrade or fail. The shock magnitudes are systematically increased until a problem occurs.  This procedure can be also performed at environmental temperature extremes.
4. Procedure IV – Transit Drop. This procedure is used to test items that could be accidentally dropped such as when they are removed from a shelve or dropped when handling. The test item is physically dropped onto a hard surface during Procedure IV.  The items can be tested inside their transit case or unpackaged.
5. Procedure V – Crash Hazard Shock Test. Procedure V is used to test materiel mounted in air or ground vehicles. This procedure is intended to verify that parts do not beak loose which would cause a hazard to occupants or create significant damage to the vehicle.
6. Procedure VI – Bench Handling. This procedure is used to test products that may experience shocks on a work bench. Bench handling shocks could occur when items are being repaired or when they are in the process of being packaged.  The products are tested in an unpackaged configuration.  The drop heights are less than Procedure IV.

Procedures VII and VII are very specialized shock tests.  They are briefly mentioned because they are part of Method 516.7, Shock Testing.

1. Procedure VII – Pendulum Impact. Procedure VII is intended to test the ability of large shipping containers and their internal contents to resist horizontal impacts from accidental handling.
2. Procedure VIII – Catapult Launch/Arrested Landing. Procedure VIII is intended for materiel mounted in or on fixed-wing aircraft that is subject to catapult launches and arrested landings.

The laboratory shock test options are summarized below in Table 516.7-II.  The shock test options are divided according to the use of Time Waveform Replication (TWR), drop tests, classical shock pulses, or SRS shocks.  TWR is considered to be superior and the most realistic as it is based upon direct replication of field measured data, however it is not usually available.  Classical shock pulses are used when TWR data is unavailable.  Shock Response Spectra (SRS) refers to cases in which an SRS curve is used for the test specification.

Table 516.7-II – Laboratory Shock Test Options from MIL-STD-810G w/Change 1

TWR – Time Waveform Replication

Drop = free fall drop event

SRS = Shock Response Spectra

X_tp – terminal peak sawtooth classical shock

X_trap – symmetric trapezoidal classical shock

X_sin – two-second damped (Q=20) sine burst

Note (1)- Horizontal Impact

It is important that the shock data acquisition instrumentation is adequate to capture the shock impulse.  Method 516.7 provides guidelines for the shock test data acquisition system.

To learn more about our shock testing services, please feel free to contact us with your inquiry. Feel free to explore our site to learn about our full line of product testing services, and the test standards that we can help our clients with.

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High G Level Random Vibration Profile

Operating the vibration shaker at these levels is difficult because fixture resonances can create control problems causing the test to abort.  First a suitable fixture had to be designed by DES.  Then DES analyzed the fixture using FEA to make sure that it would not have significant resonances below 2000 Hz.  After the fixture was manufactured, it was first tested without product on the shaker to verify its performance.  The fixture performed as designed and did not have any significant resonances that would be imparted into the product under test or cause control problems.  The next step was to mount the product to the fixture and perform the high g level random vibration test.  During the vibration test, the part had to be electrically monitored for operation.  The well designed product passed the test and the customer was very satisfied with the test results and DES’s capabilities.  For more information on Vibration Testing or other testing services, contact DES or call 610.253.6637.

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Meeting these requirements separately would alone be a challenge for any lab.  Meeting these requirements concurrently requires specialized equipment and test setup.  Good insulation is an obvious concern for this test.  The lab must ensure that heat isn’t transferred to the armature of the shaker or else costly damage can occur to the shaker system.  Extreme temperature accelerometers are also necessary if a lab wants to obtain accurate acceleration data.  DES was able to perform this test with successful results and overcome the challenges associated by utilizing their combined temperature and vibration chamber, Figure 1.

For more information on Combined Temperature and Vibration Testing or other testing services, contact DES or call 610.253.6637.

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Category 4 of Method 514.7 Vibration testing details the transportation random vibration environmental conditions from cargo interaction with vehicle suspension and structures with road and surface discontinuities.  “This environment may be divided into two phases, truck transportation over US highways, and mission/field transportation.  Mission/field transportation is further broken down into two-wheeled trailer and wheeled vehicles categories.”

Truck Transportation over US Highways Vibration Testing

This vibration test method is used when products or equipment will be transported by large trucks tractor-trailers commonly seen on US highways.  The truck transportation over US highways random vibration profile is designed to simulate 1609 km (1000 miles) on interstate highways.  The random vibration profile along each axis can be seen in the plot below in Figure 1.  The length of this profile is 60 minutes per axis for each 1000 miles of transportation.  For example to simulate 2000 highway miles, the vibration test duration would be 2 hours per axis x 3 axes = 6 hours total.

Two-wheeled Trailer Vibration Testing

The two wheeled trailer (TWT) random vibration profile is a subcategory under the Two-wheeled trailer and wheeled vehicles category.  This vibration test method is used when products or equipment will be transported by two-wheeled trailers across paved, secondary, and cross-country road surfaces.  The random vibration profile simulates the cargo conditions of a two-wheeled trailer from the forward supply point to the using unit.  The length of travel to be simulated is 51.5 km or 32 miles.  The length of this vibration profile is 32 minutes per axis and can be seen in the plot below in Figure 2.  The vibration test duration would have to be increased accordingly for longer lengths of travel.

A typical two-wheeled trailer is shown in Figure 3.

Composite Wheeled Vehicle Vibration Testing

The composite wheeled vehicle (CWV) random vibration profile is another subcategory under the Two-wheeled trailer and wheeled vehicles category.  The vibration profile simulates the cargo conditions of transport by trucks or semitrailers across paved, secondary, and cross-country road surfaces.  The random vibration profiles along each axis can be seen below in Figure 4.  The length of travel to be simulated is 800 km (500 mi) from the port staging area to the forward supply point.  The length of this vibration profile is 40 minutes per axis for each 500 miles of transport.

Composite Wheeled Vehicles are military vehicles.  A typical Composite Wheeled Vehicle is shown in Figure 5.

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MIL-STD-810 is a public military test standard that is designed to assist in the environmental engineering considerations for product design and testing.  For the purposes of this blog series we will focus on Method 514.7, titled Vibration.  This section defines the environmental vibration conditions a material or product may experience during the product life cycle and translates these conditions into replicable test procedures.  Unfortunately, unless you’re familiar with this document, this section or any section for that matter may seem a little daunting.  This blog will hopefully provide some guidance into navigating your way through it.

The best place to start is Table 514.7-I which can be found shortly after the table of contents of Method 514.7.  This table basically acts as a summary for the section and directs you to the specific annex to look for the applicable environmental vibration category for your product.  Before you jump to the test profiles, there are some definitions and details worth pointing out.  The different types of test procedures, called out in the last column of the table, are defined further on in this section.  This is important because some of the test procedures require different or unusual test setups which may be more suitable to your product’s environmental vibration exposure.

Test I: General Vibration

This condition applies to material/products “to be transported as secured cargo or deployed for use on a vehicle.  This procedure applies to ground vehicles as well as fixed and rotary wing aircraft.  For this procedure, the test item is secured to a fixture or a vibration exciter, and vibration is applied to the test item as an input.

Test II: Loose Cargo Transportation

This condition applies to material/products “to be carried in/on trucks, trailers, or tracked vehicles and not secured to (tied down in) the carrying vehicle.  The test severity is not tailorable, and represents loose cargo transport in military vehicles traversing rough terrain.”  Essentially, worst case scenario.  For this procedure, the test item is not secured to the vibration exciter, and is free to move during the test.  Typically a fence is built around the vibration table to prevent the product from falling off of the table.

Test III: Large Assembly Transportation

This condition applies to “large assemblies of material installed or transported by wheeled or tracked vehicles.  It is applicable to large assemblies or groupings forming a high proportion of vehicle mass, and to materiel forming an integral part of the vehicle.”

Test IV: Assembled Aircraft Store Captive Carriage and Free Flight

This condition applies to “fixed wing aircraft carriage and free flight portions of the environmental life cycles of all aircraft stores, and to the free flight phases of ground or sea-launched missiles.”

Test procedures I and IV use standard laboratory vibration shakers while test procedures II and III require more specialized equipment.  For the most part, most of the categories in Table 514.7-I call for test procedures I and IV which most test laboratories should have and therefore can be configured to those test profiles.

Once you have determined the application type and test procedure your product/material falls under, you can move on to determining your test profile.  There are a variety of types of vibration profiles that are defined in Annexes B through E of MIL-STD-810 depending on the expected environmental vibration exposures of your product.  General definitions of the different types of vibration profiles can be found in Annex A of MIL-STD-810G Change 1, Method 514.7, however, more detailed understanding of sinusoidal, random and mixed vibration profiles can be found in the associated links as well as below.

Sinusoidal Vibration Testing

Sinusoidal & Random Vibration Testing Primer

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These tests demonstrate the unique capability of Delserro Engineering solutions.  Not many labs are equipped to perform combined temperature and vibration testing at the extreme temperatures of this test or are able to produce the high levels required for random vibration and shock testing.

For more information on Combined Temperature and Vibration Testing or other vibration testing services, contact DES or call 610.253.6637.

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DES recently performed a combined temperature and vibration package test according to ISTA 3A Over-The-Road Trailer Spectrum for a pharmaceutic company looking to evaluate their package design.  Utilizing our combined temperature and vibration test set up we were able to successfully perform random vibration tests on their packages at 60 °C.  The vibration profile specified a frequency range from 1 to 200 Hz at 0.53 Grms.  This was a relatively simple test given DES’s capabilities.  Package tests using combined temperature and vibration, however, is a special capability uncommon to many package test labs.  Temperature ramping as well as hot and cold dwells can also be incorporated depending on your reliability needs.

For more information on Package Testing please contact DES or call 610.253.6637.

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