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MIL-STD-883 Random Vibration Testing

MIL-STD-883K random vibration testing is conducted for the purpose of determining the ability of the microcircuit. It determines the dynamic stress the microcircuit can withstand. This stress is exerted by random vibration applied between upper and lower frequency limits. This simulates the vibration experienced in various service-field environments. 

Random vibration is more 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, swept frequency sine testing may yield more pertinent design information.

The following information is extremely technical in nature. It was derived from version K of MIL-STD-883 random vibration section. Even though the language is from mil-883k vibration, it applies to previous versions of the standard. This includes MIL-STD 883G random vibration and MIL-STD 883H random vibration. 

Keystone Compliance is a random vibration test lab with significant MIL-STD 883 vibration test experience. Our random vibration laboratory and test engineers understand the nuances of the vibration profiles and vibe testing. They have an in-depth knowledge of MIL-883K random vibration, MIL-883G random vibration, and MIL-883H random vibration.

What is the Vibration System for Mil-883 Random Vibration?

The vibration system, consisting of the vibration machine and its auxiliary equipment must be capable of generating a random vibration. The magnitude of this random vibration has 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. 

The test item, or a substitute equivalent mass, must be appropriately secured to the vibration machine. 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.

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?

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 lab. 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 Random Vibration Test Procedure?

The device(s) are rigidly fastened on the vibration platform and the leads adequately secured during shaker testing. The vibration machine is then operated and equalized. Or it is compensated to deliver random frequencies and intensities that conform to the curves specified in the test condition I. 

The device(s) are subjected to a random vibration specified by the test condition letter.  This lasts for a duration of 15 minutes in each of the orientations (X, Y, and Z). Sometimes this test is performed as part of a group or subgroup of tests. In these cases the post-test measurements or inspections need not be performed exactly at the conclusion of this test.

How is Examination Completed?

After completion of the test, an external visual examination of the marking is performed without magnification. A viewer must not have a magnification of greater than 3X. A visual examination of the case, leads, or seals shall be performed at a magnification between 10X and 20X. 

This examination and any additional specified measurements and examination are made after completion of the final cycle. Or they are made upon completion of a group, sequence, or subgroup of tests which include this test.

What is the Random Vibration Test Failure Criteria?

After subjection to the test, failure of any specified measurement or examination will not receive random vibration certification. Any evidence of defects or damage to the case, leads, or seals, or illegible markings is a failure. Damage to marking caused by fixturing or handling during tests is not cause for device rejection. Such devices can still receive random vibration compliance certification. 

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

Looking to get a 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 random vibration testing standards. Contact us to learn why so many manufacturers rely on Keystone Compliance to meet their vibration testing needs.

MIL-STD-883 testing contains several test methods. For more information about these test methods, please click on one of the links below.