Stress relaxation behaviour of connectors- development of simulation techniques

The stress relaxation behaviour of a connector has been simulated using the Finite Element Method. Material data from stress relaxation tests (four-point-bending) are utilized as input data to derive the relaxation behaviour of a connector subjected to a steady state temperature field. The model comprises forming of the connector to a specified geometry and loading to a specified contact force. Relaxation data from four-point-bending tests are fitted to a power law expression for creep by setting a linear stress distribution through the sheet thickness. Other, more complex stress distributions were also used, but the result did not deviate much from the simple case. The creep data are used as input data for connector relaxation simulations. If relaxation data for the as-received material are utilized the rate of relaxation of the connector is underestimated compared to experiments. It is suggested that it is necessary to perform relaxation tests on cold worked material in order to correctly describe the relaxation behaviour of the bent portions of the connector. The effect of this approach is demonstrated and found successful. However, it is necessary to develop more reliable experimental methods to produce relaxation data on cold worked material.