Mechanical Engineering Journal (Feb 2019)
Estimation method of interfacial stiffness of bolted joint in multi-material structure by inverse analysis
Abstract
Multi-material structure is expected to be the main scheme to construct automobiles. Many methods have been studied to properly fix or bond dissimilar materials. The fixing by the bolts and nuts is one of the primary fixing methods, and has the advantage of easy assembly and disassembly. The interfacial stiffness of the bolted joints is lower than the stiffness of the base materials and varied by the clamping force of the bolts and nuts, because the micro asperities formed on the interfaces just contact each other. The contact analysis by using the surface profile of the interfaces in microscale is one of the accurate estimations. However, the estimation method of the interfacial stiffness in macroscale is also necessary for the in-situ evaluation. This study has developed an estimation method of the interfacial stiffness by the inverse analysis of the clamping force and the natural frequency of the structure. The inverse analysis algorithm introduces the mathematical model of the interfaces in which the contact of the surfaces is assumed to be the contact of the elastic asperities whose peak heights obey the Gaussian distribution. The hammering test was conducted by using the specimen which consisted of the steel plate and the aluminum alloy plate joined by the bolts and nuts. Moreover, as the contact analysis, the finite element method simulated the contact of the asperities formed on the interfaces by using the surface profile of the interfaces. The results showed that the proposed method could estimate the interfacial stiffness which reproduced the natural frequency of the specimen subjected to the clamping force of the bolts and nuts. The interfacial stiffness estimated by the proposed method was comparable to that calculated by the contact analysis.
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