The multi-scale representation model of joint interface and its finite element analysis

A novel representation model of joint interface was constructed based on multi-scale surface profiles. The contact surface profiles at different loads need different-scale asperities to support, and the asperities at different scales were equivalent to groups of springs in parallel with different size and stiffness, so the joint interface was equivalent to the coupling of series-parallel springs and gaps. The multi-scale representation model was simplified according to three hypotheses, and was perfected in the finite element model of the bolted-joint member interface. In the member interface, the top contact surface was turned with a roughness of Ra=1.2 µm, and its surface profile curve was obtained and filtered by Fast Fourier Transform (FFT) filter method based on the multi-scale contact theory. The bottom contact surface was ground with a roughness of Ra=0.2 µm and was presumed to be smooth and rigid. The rougher contact surface profile was discretized to one layer of plane182 elements in place of the springs so that the local lateral displacement of rough asperities could be considered. The load transfer and contact characteristics of the multi-scale interface model were analyzed and compared with those of the literature. Results show that the multi-scale interface model can solve the macro and micro scale contact problems in the same model, and it provides a new way to improve the comprehensive performance of the member in.