TABLE OF CONTENTS The techniques and procedures, presented in this chapter, for random vibration damage evaluation, fatigue life prediction, screening probability calculation and optimum screen time determination, require the availability of the stress response PSD function in the structural element. As discussed previously, the PSD function directly reflects energy distribution in the frequency domain, and can be related to the number of zero-crossings and the peak distribution of a random stress process. Now the question is how one can get this PSD function for a particular randomly-vibrated equipment.
Actually measuring and recording the stress-response time history requires prototypes, measurement equipment and testing time. A very effective way of obtaining the stress response PSD function is to conduct a steady-state dynamic response analysis using the finite element analysis (FEA) technique such that the need for prototypes, test equipment and testing time will be eliminated or reduced.
There are commercial software for FEA of equipment subjected to random vibration stressing, such as ABAQUS by HKS Inc. [28] and PATRAN/P3 by PDA Engineering [29; 30]. Recently, Pacific Numerix Corp. at Scottsdale, Arizona presented a new software named PCB Vibration Plus [31]. PCB Vibration Plus is the first specialized 3-D FEA software that allows complete modeling of printed circuit boards ( PCB) along with components and lead/solder joint interconnects. PCB Vibration Plus can predict PCB's stress responses to various environments, including static loading, transient loading,...
