Bending of a Staple

A staple is a short piece of wire driven through and bent to bind together papers etc. The bending process takes place very slowly such that inertial effects are negligible and it can be termed as quasi-static. Quasi-static problems can be simulated well with either Abaqus/Standard or Abaqus/Explicit. Typically, quasi static problems are solved with Abaqus/Standard but may face convergence difficulties due to contact or other nonlinearities. Such problems are a good candidate to be solved with Abaqus/Explicit as explicit procedure can resolve complicated contact problems and other discontinuous nonlinearities more easily than Abaqus/Standard.

The sharp corners make the resolution of contact a very difficult task using hard contact relationship. The “hard” contact relationship, which is default in Abaqus, implies zero-penetration of the contacting bodies. This could make the solving contact problems a challenging task

The “softened” pressure-overclosure relationship are used to overcome the convergence problems at the contact interface.

The “soft” pressure-overclosure relationship, which allows some penetration, can make it easier to resolve the contact difficulties. Although there is some penetration shown in the figure but the analysis does not stop.

von Misest stresses at the end of the step.

The following animation shows the evolution of von Mises stresses, equivalent plastic strain and strain.

Simulation of the bending of a staple