MIL-STD 810 Vibration Testing
The purpose of MIL-810H vibration testing is to provide guidance for vibration compliance testing. Mil-810 vibration is the standard for conducting vibration laboratory tests. It aids in defining the vibration environments that material may be exposed to throughout a life cycle.
Vibration tests are performed to develop material to function in, and withstands the vibration exposures of a life cycle. This includes synergistic effects of other environmental factors, material duty cycle, and maintenance.
What are the Effects of the Environment?
Vibration results in dynamic deflections of and within material. These deflections and their associated velocities and accelerations may contribute to structural fatigue and mechanical wear of structures, assemblies, and parts. Dynamic deflections may cause impact to elements and/or disruption of function.
Some typical symptoms of problems caused by vibration are:
- Chafed wiring
- Loose fasteners/components
- Intermittent electrical contacts
- Electrical shorts
- Deformed seals
- Failed components
- Optical or mechanical misalignment
- Cracked and/or broken structures
- Migration of particles and failed components
- Particles and failed components lodged in circuitry or mechanisms
- Excessive electrical noise
- Fretting corrosion in bearings
What are the Differences Amongst the Vibration Procedures?
MIL-STD 810 H Procedure I – General Vibration
This procedure is used to test material that is being 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 vibration exciter. Vibration is then applied to the test item as an input at the fixture/test item interface. Steady state or transient vibration may be applied as appropriate.
The general vibration includes random vibration. This procedure applies to not just 810H random vibration. It also applies to previous versions of the standard including MIL-STD 810G random vibration.
MIL-STD 810 H Procedure II – Loose Cargo Transportation
This procedure is used to test material that is not secured to the carrying vehicle. Carrying vehicles include trucks, trailers, or tracked vehicles and is not secured to the carrying vehicle. The test severity is not tailorable, and represents loose cargo transport in military vehicles traversing rough terrain.
This procedure language is taken directly from MIL-STD0810H. The procedure is similar to the previous version of the standard including MIL-STD 810G vibration.
MIL-STD 810 H Procedure III- Large Assembly Transportation
This procedure replicates the vibration and shock environment of large assemblies of material. These material assemblies are either installed in, or transported by wheeled or tracked vehicles.
This procedure is applicable to large assemblies or groupings that form a high proportion of vehicle mass. It is also applicable to material that forms an integral part of the vehicle. In this procedure, the specified vehicle type is used to provide the mechanical excitation to the test material.
The vehicle is driven over surfaces representative of service conditions. This creates a simulation of both the vibration environment and the dynamic response of the test material to the environment. Generally, measured vibration data is not used to define this test, but it is often acquired during this test. When acquired it is used to verify that vibration and shock criteria for material subassemblies are realistic.
MIL-STD 810 H Procedure IV- Assembled Aircraft Store Captive Carriage and Free Flight
This procedure is applied to fixed wing aircraft carriage. It is also applied to free flight portions of the environmental life cycles of all aircraft stores. It is also applied to the free flight phases of ground or sea-launched missiles.
The previous procedures are used for other portions of the store’s life cycle as needed. Steady state or transient vibration may also be applied as appropriate. Procedure I is not applied to fixed wing aircraft carriage or free flight phases.
What is the Test Item Configuration?
The test item is configured for each test as it will be in the corresponding life cycle phase. In cases representing transportation, all packing, shoring, and padding are duplicated in the vibration test lab. Other configuration modifications of the shipment are also considered. The transportation configuration may be different for different modes of transportation.
For loose cargo the procedure presented is a general representation based on experience as well as measurement, and is not tailorable. The most realistic alternative for truck, trailer, or other ground transportation requires the transportation vehicle and a full cargo load. This is the best vibration testing option.
In this test, the cargo is free to bounce, scuff and collide with other cargo, and the sides of the vehicle. The loose cargo environment includes conditions experienced by cargo transported in a vehicle traversing irregular surfaces. This test replicates the repetitive impact environment incurred by cargo transported under these conditions.
This procedure assumes no relative motion between the vehicle cargo deck, or cargo compartment and the cargo. This applies directly to material that is tied down or secured. The tethers should ensure that no relative motion is allowed considering vibration, shock, and acceleration loads.
Sometimes restraints are not used or they allow limited relative motions. When this occurs, allowances should be provided in the test setup, and in the vibration excitation system, to account for this. Procedure III is an alternative for ground transportation.
Stacking or bundling of sets or groups of material items may affect the vibration transmitted to individual items. Ensure the test item configuration includes appropriate numbers and groupings of items.
What is the Test Process?
Procedure I – General Vibration
Procedure I of mil-std-810 vibration, uses standard laboratory vibration exciters (shakers), slip tables, and fixtures. Choose what specific exciters to use in the shaker testing based on the size and mass of test items and fixtures. Consider the frequency range required,and the force, acceleration, velocity, and displacement required.
Procedure II – Loose Cargo Transports
Simulation of the environment used for Procedure II, requires use of a package tester. This package tester should impart a 25.4 mm, or 1.0 inch, peak-to-peak, circular synchronous motion to the table. This should happen at a frequency of 5 Hz. This motion takes place in a vertical plane.
The fixturing does not secure the test item(s) to the bed of the package tester. For best results, ensure the package tester is large enough to accommodate the dimensions and weight of specific test items.
This procedure is directly from MIL-STD 810H, but is accurate for previous versions including MIL-810G vibration.
Procedure III- Large Assembly Transport
The test facility for Procedure III requires test surfaces and vehicles that represent transportation. They may also represent service phases of the environmental life cycle. The test item is loaded on the vehicle and secured or mounted to represent the life cycle event. The vehicle is then driven over the test surface in a manner that reproduces the transportation or service conditions.
The test surfaces may include designed test tracks, typical highways, or specific highways between given points. Potentially, such testing can include all environmental factors related to wheeled vehicle transport, including: vibe testing, shock, temperature, humidity, pressure, etc.
Procedure IV – Assembled Aircraft Store Captive Carriage and Free Flight
Procedure IV of mil-std 810 vibration uses standard vibration laboratory exciters, or shakers. This enables driving the test item directly, or through a fixture. The test item is supported by a test frame independent of the shaker table.
Shakers are chosen based on the size and mass of test items and fixtures. Frequency range, and low frequency stroke length (displacement) required are also important. This procedure is directly from MIL-STD 810H, but is accurate for previous versions including MIL-STD-810G vibration.
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There have been several versions of vibration testing procedures in MIL-STD-810 vibration testing. Below is a list of each version and the appropriate method number:
- MIL-STD-810A Test Method 514 Vibration Testing
- MIL-STD-810B Test Method 514 Vibration Testing
- MIL-STD-810C Test Method 514.2 Vibration Testing
- MIL-STD-810D Test Method 514.3 Vibration Testing
- MIL-STD-810E Test Method 514.4 Vibration Testing
- MIL-STD-810F Test Method 514.5 Vibration Testing
- MIL-STD-810G Test Method 514.6 Vibration Testing
- MIL-STD-810H Test Method 514.8 Vibration Testing