Reliability quantification of plates subjected to random vibration and temperature loads

Abstract

Random vibration coupled with thermal cycling is a common environment for a lot of mechanical and electrical products, especially for those experiencing transportation and handling frequently. Today, random vibration plus thermal cycling have been broadly applied as an important stimulus stress to expose the latent defects during development. In addition, drop tests are also necessary for these products since an accidental drop may seriously damage them. Both random vibration and drop tests are expensive. Plate element is popular in portable and transportation related products, for example, the Printed Circuit Boards (PCBs) in equipment installed in vehicles, the Liquid Crystal Displays (LCDs) in portable computers and the skin panels near the engines in airplanes. These plate elements are subjected to random vibration and thermal cycling, and some of them may encounter a drop. Even through the deterministic vibration theory of plates has been developed a lot, the random vibration theory of plates has not been well explored yet, particularly in reliability quantification, response analysis, and thermal load effect. In this dissertation, a random vibration analysis model for packaged plates is proposed for base excited random vibration coupled with temperature loads. Based on this model, a reliability quantification model is proposed, too. Two common random vibration power spectral densities "Ideal White Noise (IWN)" and "Band Limited White Noise (BLWN)" are researched. As a result, the closed form solution for IWN is derived and the numerical procedure for BLWN is presented. By comparing the IWN results with the BLWN results, an application limit to IWN is discovered. The effects of temperature and damping on reliability are then investigated. For the drop load case, the response process and the reliability are researched, and the illustrative example is given to demonstrate the methodology. The research results of the dissertation may supply designers with guidelines and supplement testing with analytical data; therefore, the test cost can hopefully be cut down. The methodologies can be applied to the evaluation of transportation reliability.