Numerical Study of a Crimped Assembly Mechanical Strength

Abstract

Electrical contact crimping is a mechanical fastening process commonly used in aeronautical and aero spatial applications. In order to ensure the perfect electrical conduction and acceptable mechanical properties, the assembly have to fullfil some drastic holding force criteria. This outfit is directly dependent on the indentation depth at the end of crimping. The feedback generally reveals that an over crimping will lead to the cable breakage whereas an under crimping will be characterized by the cable sliding into the contact during pulling. The optimal behavior is a combinaison of both phenomena : the cable must become thinner before slipping into the contact. Numerical simulation is an efficient tool to limit the tedious experimental tests. It is the main topic of our work. This paper deals with prediction of the failure type and the force level required to tear out a contact crimped on multistrand cable for different indentation depths. The determination of optimal crimping condition is determined. In order to simulate the contact tensile test, crimping simulation has to be performed. The first step is then to be able to simulate accurately the crimping stage by using appropriate behavior laws and realistic conditions. One difficulty is linked to the small size of our objects. The first one is a 19 strands cable, in which each strand is about 0.15 mm diameter. The second sample is a 1 mm diameter cylindrical copper contact measuring 7 mm long. Adapted testing devices are described. Geometries and mechanical fields are obtained and then exported in the mechanical holding model to ensure realistic prediction [1]. Impact of crimping conditions on the pulling results is discussed. Pulling simulation results are compared to experimental values. The prediction of breakage mechanisms is also studied. Keywords: Crimping process, mechanical fastening operation, finite element computations, mechanical strength, breakout force, tensile test. [1] Fayolle, S., 2008, Etude de la modélisation de la pose et de la tenue mécanique des assemblages par déformation plastique : application au rivetage auto poinçonneur, Thèse de l'Ecole des Mines de Paris.