Mechanical Environmental Reliability Test/Vibration Test/

Mechanical Environmental Reliability Testing:
1. Vibration test:
Vibration test simulates the vibration environment of products, equipment and engineering in the transportation and use environment, so as to test its reliability and stability. Mechanical vibration test is used to determine the weak link of machinery, the integrity and dynamic characteristics of product structure, and is often used in type test, life test, evaluation test and comprehensive test. The vibration resistance of automotive electronics is even more important.
Vibration test types are mainly divided into:
1) Environmental adaptability test: select the vibration environment that the test object may bear in the future to motivate the object, and test its adaptability to the environment.
2) Kinetic strength test: examine the dynamic strength of the structure of the test object, and test whether the specimen will cause fatigue damage under the given test conditions. The object of this kind of test is mainly the structural parts.
3) Dynamic characteristic test: test the dynamic characteristic parameters of the object, such as vibration type, frequency, and damping, etc.
4) Other tests: such as the vibration screening test, its
The purpose is to screen the vibration of the components, components and whole machines on the production line, find out the weak links in the process, and pick out the low-quality products so as to improve the reliability of the whole product.
The vibration is divided into sinusoidal vibration, random vibration, composite vibration, scanning vibration, fixed frequency vibration. The most commonly used vibration modes can be divided into sinusoidal vibration (Sine vibration) and random vibration (Random vibration).
Sinusoidal vibration is mainly based on the vibration resistance proof of simulated shipping and ship use equipment, product structure resonance frequency analysis and resonance point residence verification. Sinusoidal fixed frequency test: Conduct sinusoidal vibration test at the selected frequency (can be resonant frequency, specific frequency, or dangerous frequency) according to the specified value and reach the specified time. Sinusoidal sweep test: within the specified frequency range, according to the specified scan rate from low frequency to high frequency, and then from high frequency to low frequency as a sweep, until the specified total number of times.
Random vibration is simulated by the vibration strength of the overall structure of the product and the transportation environment in the packaging state. The random vibration environment condition assumes that the vibration response of each state goes through a smooth random process, and the power spectral density matrix is used to define the vibration condition. The order of the matrix is equal to the number of interface degrees of freedom controlled by the test. The diagonal term of the spectral density matrix is the autospectral density function describing the one-dimensional random vibration environment used in the traditional uniaxial vibration test. At the same time, it also stipulates the root mean square acceleration value of the corresponding vibration direction, the definition of the autospectral density can be followed, the existing environmental test standard, using the external field measurement envelope to cover all possible vibration processes of the product in the use process. Off-diagonal terms are a mutual spectral density function of complex form,
It reflects the correlation degree between the vibration response of different degrees of freedom, and the mutual spectrum from the external field data, especially when there is no acceptable envelope program to synthesize the influence of different vibration and dynamic process. An approximate treatment method in engineering is to stipulate the amplitude of the mutual spectrum with the coherent function, and expresses the phase of the frequency domain by a random variable uniformly distributed by [0,2 π]. The coherence function can adopt an average or envelope treatment corresponding to the autospectral definition, reflecting some directionality of the spatial motion.