Development of an improved screw model at Faurecia

Some years ago Faurecia used a very simple screw model. In this model the screw holes are filled by a rigid body and the screw shaft is modeld by a simple spring beam with an unrealistic stiffness. But this model doesn’t represent the behavior of screws in real test. With this simple model it was not possible to get the peeling effect of the holes. And the deformation of the part and the screw was unrealistic. Also the forces inside the screw were too high. Due to the goal to reduce the time to market and the number of prototypes to develop a new product it was necessary to develop a better screw model. At the end of 2008 a new keyword was available in LS-Dyna with which it was easy to implement a defined preforce on a beam element. This was the point to start with an improved screw model.