Computer program, system and method to specify random vibration tests for product durability validation

A computer system for determining the testing profile for accelerated laboratory random vibrational testing of a product in accordance with an application program that controls testing equipment coupled to and for testing the product in accordance with test signals, the system comprising:

• a control processing unit coupled to and for controlling the testing equipment,
• a memory for storing the application program for controlling the central processing unit,
• program means for selecting the frequency range of 5 Hz to 200 Hz,
• program means for developing a simplified composite Power Spectral Density function PSD.sub.j (f), including scaling coefficients, representative of the PSD for random vibration loadings in expected field vibration levels,
• program means for developing the shape of PSD.sub.T by using approximately ten scaling coefficients, for producing on the product the test acceleration forces corresponding to the PSD.sub.j function,
• program means for calculating the stress response curve H(f) for the product representative of the transmissibility function from the input acceleration forces to the local vibration stress forces,
• program means for selecting the test duration based on the capabilities of the testing equipment and the testing time available, and then calculating the amplification factor AF from the relationship ##EQU23## program means for recalculating the accelerated PSD profile, PSD.sub.T (f) for testing based on the selected test duration and the amplification factor:
• ##EQU24## and program means for generating said test signal for testing the product using the selected PSD function to validate the required performance lifetime for the product when no test failures are observed over all of the T hours.

A method for determining the testing profile for accelerated laboraboty random vibrational testing of a product, comprising the steps of:

• (i) selecting the frequency range covered in the lab accelerated testing,
• (ii) developing a simplified composite Power Spectral Density function PSD.sub.j (f), including scaling coefficients, representative of the Power Spectral Density PSD for random vibration loadings in expected field vibration levels,
• (iii) developing the shape of Composite Power Spectral Density curves PSD.sub.T by using the scaling coefficients, for producing on the product the test acceleration forces corresponding to the PSD.sub.j function,
• (iv) calculating the stress response curve H(f) for the product representative of the transmissibility function from the test acceleration forces to the local vibration stress forces,
• (v) selecting the test duration based on the capabilities of the testing equipment and the testing time available, and then calculating the amplification factor AF from the relationship ##EQU28## (vi) recalculating the accelerated PSD profile, PSD.sub.T (f) for testing based on the selected test duration and the amplification factor:
• ##EQU29## whereby the product may be tested using the accelerated PSD profile to validate the required performance lifetime for the product when no test failures are observed over the T hours.