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MIL-STD-202 Random Vibration Testing

The purpose of MIL-STD-202 Random Vibration testing is to determine the ability of component parts to withstand dynamic stress. This dynamic stress is exerted by random vibration. Random vibration testing is applied between upper and lower frequency limits. This simulates the vibration experienced in various service field environments in a test item’s life cycle.

Random vibration testing is characteristic of modern field environments produced by missiles, high-thrust jets and rocket engines. In these types of environments, the random vibration provides a more realistic test. For design purposes, however, a swept frequency sinusoidal test may yield more pertinent design information.

Keystone Compliance is a random vibration testing lab with significant MIL-202 random vibration test experience. Our vibration laboratory and test engineers understand the nuances of the vibration profiles and vibe testing.

The following information is extremely technical in nature. It was derived from test method 214 of MIL-STD 202G random vibration section. Even though the language is from MIL-202G random vibration, it applies to previous versions of the standard. This includes MIL-STD 202H random vibration.

What is the 202 Random Vibration Testing System?

The vibration system, consisting of the vibration machine, together with its auxiliary equipment shall be capable of generating a random vibration. The magnitude of this random vibration should have a gaussian (normal) amplitude distribution. However, the acceleration magnitudes of the peak values may be limited to a minimum of three times the rms.

The test equipment must be capable of being equalized. This is so that the magnitude of its spectral-density curve will be between specified limits during shaker testing.

The test item, or a substitute equivalent mass, must be appropriately secured to the military random shaker. The equalization of an electrodynamic vibration machine system is the adjustment of the gain of the electrical amplifier and control system. The ratio of the output-vibration amplitude to the input-signal amplitude must be of a constant value (or given values). This must be maintained throughout the required frequency spectrum.

Keystone Compliance laboratories have high quality vibration testing equipment, which enables us to perform complete military standard testing and vibration analysis.

How is Vibration Testing Monitored?

Monitoring involves measurements of the vibration excitation and of the test-item performance. When specified, the device shall be monitored during the test. The details of the monitoring circuit, including the method and points of connection to the specimen, shall be specified.

How is the Vibration Input for 202 Random Vibration Testing?

The vibration magnitude is monitored on a vibration machine, on mounting fixtures. These are in locations that are as-near as practical to the device mounting points. Sometimes the vibration input is measured at more than one point. In these cases, the minimum input vibration is made to correspond to the specified test curve.

Massive test-items and fixtures, and large-force exciters or multiple-vibration exciters can be used in the random vibration laboratory. In these instances, the input-control value may be an average of the average magnitudes of three or more inputs. Accelerations in the transverse direction are measured at the test-item attachment points. These are limited to 100 percent of the applied vibration.

What is the Method of Mounting used to Achieve the Best Random Vibration Testing?

The specimens shall be mounted in accordance with the instructions in the individual specifications. The orientation of the specimen or direction(s) of the applied vibration motion shall be as specified. Any special test fixtures or jigs required to run the test shall be as specified.

Detailed Individual specification assures reproducibility of the input motion applied to the specimen. These details shall include the dimensions, the materials, temper, etc., as applicable.

What are the Detailed Requirements of Mil-202G Vibration Testing?

Measurements: According to MIL-STD 202 G, measurements shall be performed before, during, and after the test. This is specified in the individual specification.

Also included in the individual specification must be details like monitoring instrumentation and order of application of vibration direction (if applicable). Additionally the number and location of test points, and the method of mounting and orientation should be detailed. Also necessary is details about test conditions, duration of the test, and measurements before, during, and after test.

Keystone Compliance has been recognized as one of the best random vibration labs in the country. Our capabilities include random vibration compliance testing to commercial and military random vibration testing standards. With one of the best vibration labs we use only state of the art vibration test systems. Our vibration laboratory and test engineers understand the nuances of the vibration profiles and vibe testing.

Looking to get a random vibration certification for your product? Talk to our experts to develop a streamlined test plan and receive a professional and affordable quote. Work with certified vibration analysts that understand the requirements of military vibration testing. Contact us to learn why so many manufacturers rely on Keystone Compliance to meet their vibration testing needs.

Looking for other MIL-STD-202 compliance tests? Click on a link below to learn more about the other test methods.

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