On the Mode Based Simulation of Dry Friction inside Lap Joints

Recently proposed joint interface modes (JIM), which have been presented at the IMAC 25th, consider Newton's third law across a joint already at the stage of mode generation. This approach leads to significant improvements in the subsequent mode based simulation, where nonlinear contact and frictional forces are applied. This contribution is focusing on the efficient computation of forces according to dry friction. The first part covers the friction model itself. A lot of literature points out that the discontinuity of the well known Coulomb friction is a major drawback in terms of efficient time integration. Therefore alternative friction models are investigated and a comparison with the Coulomb model is performed. The second part deals with the relevance of trial functions in tangential direction of the contact surface. The latter mentioned JIM can be subdivided into Ritz vectors, which are required to approximate the joint deformation in joint normal direction where the contact forces are acting, and such, which are required to approximate the joint deformation in joint tangential direction where the friction forces are acting. Theoretical considerations and a numerical example are presented which reveal, that the number of JIM in tangential direction is significantly smaller as the one in contact direction without losing remarkable quality of the result.