**Description**:

Perfect plasticity is a property of materials to undergo irreversible deformation without any increase in stresses or loads.

We considered an example where material has Elastic modulus of 159000MPa and will Behave as perfectly plastic once reached to 350MPa. After reaching 350 MPa material will undergo deformation without increase in stresses. It is expected that stress in model should not exceed 350 MPa

**Procedure:**

1.Create MAT1 card by Right click in model browser>Material.

2.Select card image as MAT1.

3.In MAT1 enable MATS1 and Select TYPE as plastic.

4.Select TYPSTRN as 1 ( Plastic) and in LIMIT1 put yield point as 350.0 MPa.

While requesting output request please make sure that Stress is requested output at the element centre and the Gauss integration points.

This can be done by selecting GAUSS in location tab

This will create Elastic perfectly plastic material in HyperWorks for OptiStruct solver.

This can be validated by checking Von mises stresses at GAUSS location for solver decks with varying enforce displacement. The enforcement displacement is considered as 0.2 mm,0.21 mm and 0.25 mm.

The corresponding stress for 0.2 mm is below 350 MPa and hence it is lying in elastic region, this can be seen in fig.2

Figure 1. Max von mises stress with stress-strain Graph Figure 2.Enf Disp Vs. Max Von Mises Stress

The graph of Enforced displacement Vs. Von mises stresses (Fig.2) shows that material is modelling expected behaviour of Elastic perfectly plastic material.