Numerical modelling of lockbolted lap connections for aluminium alloy plates

A numerical modelling method for lockbolted lap connections of aluminium alloy plates is studied based on experimental tests. The mechanical properties and constitutive models of aluminium alloy 6061-T6 and stainless steel 304HC were intensively determined by tensile tests. A tensile test of a single-lockbolted lap connection was conducted to obtain its elongation and strain responses. A basic numerical model that considers the lockbolt preload, interface contact and friction, and gaps between the lockbolt and bolt hole was established to simulate the tensile behaviours of this connection. This model was updated to minimize errors between the numerical and test results, and values for the friction coefficients of different contact surfaces were suggested. To improve the accuracy and efficiency of the numerical analysis, an incompatible mode solid element was adopted in the numerical model. It was determined to be better than refining the mesh or accepting a higher-precision element type. This numerical modelling method was investigated by two types of double-lockbolted connections, and its validity was verified by comparing the displacement and strain responses between the numerical and test models. The modelling method suggested in this paper is applicable for simulating the mechanical behaviours of complicated joints with lockbolted lap connections.