Determination of Valanis model parameters in a bolted lap joint: Experimental and numerical analyses of frictional dissipation

In this work, Valanis model parameters, and their variation with bolt preload, were determined for a bolted lap joint, which consisted in two steel plates held together by a metric 12 screw. For this purpose, a series of transitory non-linear analyses were performed on the basis of a three dimensional finite element model of the bolted lap joint subjected to varying bolt preloads and tangential displacements. Curve fitting of hysteresis cycles obtained from numerical simulations allowed determination of Valanis model parameters as well as assessment of bolt preload influence on these parameters. In addition, the present numerical simulations provided information about the evolution of the contact state from stick to slip regimes between the bolted plates, reflecting the non-linear behaviour of the joint. Quasi-static tests at several preloads and tangential displacements conditions were conducted to validate Valanis model parameters previously obtained from numerical simulations. The present findings provided detailed information about the evolution of the aforementioned Valanis parameters with bolt preload. Thus, we confirmed that equivalent stiffness values corresponding to the macro-slip regime as well as the upper limit of the sticking regime (Et and σ0, respectively) are highly influenced by bolt preload levels. These results may prove useful to appropriately design bolted joints to be used under specific stiffness and damping criteria, and therefore reducing the vibration response of the joint.