MIL-STD 810, Method 516, Shock Testing Overview

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

MIL-STD 810, Method 516, Shock Testing Procedure II – Transportation Shock

MIL-STD 810, Method 516, Shock Testing Procedure III – Fragility

MIL-STD 810, Method 516, Shock Testing Procedure IV – Transit Drop

MIL-STD 810, Method 516, Shock Testing Procedure V – Crash Hazard Shock

Bench Handling Shocks are 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.  Products are tested in an unpackaged configuration and are usually non-operational during the test.  Procedure VI is appropriate for medium-to-large test items that have a maximum dimension greater than approximately 23 cm (9 inches).  Smaller products are typically tested to higher shock levels using Procedure IV, Transit Drop.

Bench Handling Shocks are performed on a solid wood bench top that is at least 4.25 cm (1.675 inches) thick.   The procedure is:

• Perform an operational and physical checkout of the unit under test before start. Configure the test item as it would be for servicing, i.e., with a service panel removed, etc.
• Using one edge as a pivot, lift the opposite edge of the product until one of the following conditions occurs (whichever occurs first). This step is shown in Figure 1 above.

1. The lifted edge of the chassis has been raised 100 mm (4 in.) above the horizontal bench top.
2. The chassis forms an angle of 45° with the horizontal bench top.
3. The lifted edge of the chassis is just below the point of perfect balance.

• Release the product and let the chassis drop back freely onto the horizontal bench top. Repeat using other practical edges of the same horizontal face as pivot points, for a total of four drops.
• Repeat Step 3 on other faces until the item has been dropped for a total of four times on any face on which it could be placed practically during servicing.
• Perform a visual inspection of the test item. Then perform a final operational and physical checkout and compare the results to step 1.

Typical failures are damaged cover protrusions, connections or even internal damage to the product.  For more information on Shock Testing or other testing services, contact DES or call 610.253.6637.

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MIL-STD 810, Method 516, Shock Testing Overview

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

MIL-STD 810, Method 516, Shock Testing Procedure II – Transportation Shock

MIL-STD 810, Method 516, Shock Testing Procedure III – Fragility

MIL-STD 810, Method 516, Shock Testing Procedure IV – Transit Drop

Crash hazard shocks apply to materiel mounted in air or ground vehicles.  Shock testing according to Procedure V of MIL-STD 810, Method 516 is intended to test the strength of products during a crash situation to verify that parts do not break apart, eject and become a safety hazard.  Failures of this nature could cause dangerous projectiles that could impact occupants or create significant damage to the vehicle.

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 V – Crash Hazard Shock.  In limited cases a half sine shock impulse is specified.  Its shape and tolerance limits are shown in Figure 516.7-12.

Figure 516.7-10. Terminal peak sawtooth shock pulse configuration and its tolerance limits

Table 516.7-IV. Terminal peak sawtooth default test parameters for Procedure V – Crash Hazard Shock

Figure 516.7-12. Half-Sine shock pulse configuration and tolerance limits

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.

Typically, calibration shocks are performed first using a mass similar in size, weight and center of gravity (CG) of the product to be tested.  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.  The units under test do not have to be operating during crash hazard shocks.  After each shock, the test sample is inspected for visual damage.  Minor permanent deformations are usually acceptable as long as the product stays intact.  Significant damage such as large cracks may be cause for failure if they pose a risk of structural failure.

The most common requirement is to perform 2 shocks along both the positive and negative directions along 3 orthogonal axes.  This is a total of 6 directions and 12 total 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, 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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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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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 package testing per ASTM standard, ASTM D7386-12.  The test included shipping vibration testing which was conducted on DES’s Unholtz Dickie ED Shaker System.  ASTM D7386-12 requires packages to withstand random vibration levels of approximately ½ Grms over the frequency range 1 – 200 Hz.  This test is meant to simulate environments these packages could see in the field.  It is extremely important for manufacturers to test the effectiveness of their package designs prior to product shipment.  Shipping environments can put a lot of stress on products.

Improper package design can cause products to fail when the customer receives the product.  Environments such as high altitude, temperature, humidity, vibration and shock are common for most packages.  High return rates due to damage during shipment can cripple a company’s bottom line.  Prevent this from happening and send DES your packages to test!

Other package testing standards DES is capable of include (but not limited to):

• ISTA 1 Series
• ISTA 2 Series
• ISTA 3 Series
• ASTM D3580 Vibration (Vertical Linear Motion) Test of Products
• ASTM D4169 Performance Testing of Shipping Containers and Systems
• ASTM D4728 Random Vibration Testing of Shipping Containers
• ASTM D7386 Performance Testing of Packages for Single Parcel Delivery Systems
• ASTM D999 Vibration Testing of Shipping Containers

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Vibration of a mechanical system can be descried as an oscillatory motion about an equilibrium point. Certain vibrations of mechanical systems can be considered desirable, such as in musical instruments like a tuning fork or guitar.

However, often times vibrations of mechanical systems are undesirable, producing wasted energy, unwanted noise and catastrophic failures. Therefore it is critical during the product design phase that engineers are able to accurately characterize the vibration response of the system in order to ensure a safe and reliable product for their customers. We accomplish this through comprehensive vibration testing services.

There are two main categories of vibration responses engineers are concerned with: free (or natural) vibration, and forced vibration.

Free vibration is considered to be the natural stored energy of the system. When a disturbing force enters the system and is then removed, the resulting vibrational response is considered the free vibration, and the resulting frequency or frequencies of oscillation are considered to be the natural frequencies.

If such a disturbing force is repeatedly introduced into the system, the resulting vibrational response of the system is considered to be a forced vibration, and the resulting frequency of oscillations is considered the forcing frequency. If the forcing frequency is close to a natural frequency of the system and the system is lightly damped, huge vibration amplitudes may occur. This phenomenon is known as resonance.

Resonance can be fatal to mechanical systems and engineers must avoid it at all costs.  Large amplitudes imply large forces, and large forces cause material and system failure.  For example, consider the well-known Tacoma Narrows Bridge collapse.

The Tacoma Narrows Bridge was a suspension bridge crossing the Tacoma Narrows straight in Pierce County, Washington. On the morning of November 7, 1940, the force of wind gusts acting on the bridge reached a periodic frequency matching that of the natural frequency of the bridge. The result was a wildly unstable resonance response which caused the bridge to swing and twist uncontrollably until the bridge couldn’t support itself anymore and ultimately collapsed. Although the collapse produced no human casualties, it served as an example of the implications of vibrational resonance.

Examples of resonances in mechanical products can be seen in one of our videos.

In order to prevent a catastrophic failure in your product, DES is capable of controllably testing and analyzing the vibrational response of your product with its wealth of experience and knowledge, utilizing our vibration tables and vibration analysis software. Contact us to learn more about our vibration testing services today.

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This sounds like an easy shock to carry out because a peak of 35G is low compared to many shocks. However, this is a difficult shock to perform because 50 milliseconds is a long duration. Most typical shock durations are less than 20 milliseconds.

A half sine shock impulse has the shape of a half sine wave. More details can be found elsewhere on our blog, in an article titled “Classical Shock Testing“.

A half sine shock impulse is created when the shock machine table accelerates downward, then impacts a rubber material and changes direction abruptly. This abrupt change in direction causes a rapid velocity change which creates the shock impulse. Different rubber or foam materials are used to create half sine shocks with different magnitude and durations.

Half sine shocks can be performed on Electro Dynamic (ED) Shakers, Drop Tables or Drop Towers or Pneumatic Shock Machines. For this particular shock, DES used its Drop Tower Shock Machine. This machine has large bungee cords to increase its capability.

The required velocity change for a 35G, 50 millisecond duration half sine shock is 430 inches per second. A typical free fall drop table shock machine is only capable of a maximum velocity change of approximately 260 inches per second. A free fall drop machine could not attain a 35G peak, 50 millisecond duration half sine shock.

The addition of large bungee cords is used to create higher shock table velocities. The bungees act like large rubber bands or springs pulling the table downward. Higher shock table velocities can also be used to create higher peak G levels.

The impact material (sometimes called the shock programmer) for the 35G, 50 millisecond duration half sine shock was various density foam rubber pieces that were a total of 10 inches thick. It is a dramatic shock, as seen in the video above. As our customer described it, we are moving the shock table at a very high velocity to hit a bunch of pillows!

A typical plot for this shock impulse is shown below. DES was able to easily obtain both the 35G peak and 50 millisecond duration.

What sets DES apart from other labs is our in-depth experience and technical capability to understand and reproduce the most complicated shock profiles. DES has tested to the most complex shock requirements on products that are used in outer space, rockets, missiles, military environments, etc.

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Some of the shock levels were over 3200 G’s to simulate the rugged launch environment. Both the local manufacturer and Lockheed Martin Corporation were pleased with the testing. Their products successfully passed the shock tests at DES. They acknowledged DES’s role and informed DES that their products operated successfully during the launch!

What sets DES apart from other labs is our in depth experience and technical capability to understand and reproduce the most complicated vibration and shock profiles. DES continues to perform the most complex vibration and shock tests on products that are used in outer space, rockets, missiles, automotive & truck environments, military environments, hospitals, etc.

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