Effect of Pressure Distribution on Energy Dissipation in a Mechanical Lap Joint

Mechanical joints, such as the bolted shear lap joint considered here, are ubiquitous in engineered structures, which realize vibration damping as well as load transfer from them. However, the prediction of the energydissipation characteristics of such joints remains a challenging problem. A cubic relationship between energy dissipated and load magnitude is often assumed in classical joint dynamics, but experiments generally fail to support this assertion. In nearly all of the joint models examined previously, Coulomb friction and uniform pressure in the joint were assumed. Realizing that the Coulomb model may not adequately represent the actual dynamic friction in the slip region of the joint interface and that the actual interfacial pressure is likely nonuniformly distributed, we utilize a distributed-parameter joint model to investigate the constitutive relation and energy dissipation associated with a shear lap joint under longitudinal loading. Two nonuniform pressure distributions in a one-dimensional structure are considered. In both, under the Coulomb friction law, the energy dissipation resulting from microslip can be expressed as a power series starting from the third order of the magnitude of loading. It is shown that the exact cubic relation is valid only for the uniform pressure distribution. The distributed-parameter joint model presented herein can be represented by a parallel–series Iwan model. The distribution function of critical slip force in the Iwan model can be obtained analytically from the constitutive relation associated with the joint model; results are given for the cases of the normal traction specified as a power function of the spatial coordinate, and as a Gaussian function.