Finite element analysis of tapped thread joints: Setup of a computationally efficient modeling approach

This contribution deals with the efficient numerical modeling of tapped thread joints. Commercial FE packages provide different strategies to tackle the problem of modeling threaded joints, which is a recurrent one for the design engineer. Different modeling techniques are characterised by how the screw is modeled: either three-dimensional elements (thetra, hexa or wedge) or mono-dimensional elements (beam) can be used. In the case of three-dimensional approaches, the thread helix is seldom modeled: the actual geometry is often replaced by a plain cylinder and a suitable choice of contact settings between the screw and the "threaded" hole. In the case of road vehicles, due to the high number of threaded connections to be modeled, it is paramount to reach a trade-off between modeling accuracy and computational effort. This paper aims at comparing two modeling approaches, namely a three dimensional approach (baseline) and a mono-dimensional one (simplified model). Based on several criteria, such as equivalent stress on the screw shank, pressure distribution at the interface of the plates and in the underhead region, optimal contact settings for the simplified model are suggested. These settings allow replicating the results provided by the three-dimensional approach for given load case. The comparison is carried out on single lap, single screw joints, by the ANSYS R17 software. The methodology can be easily extended to other softwares or joint configurations.