I want to use of damage plasticity model in abaqus. when i use of 3D8R elements, the running complete easily, but when i use of 3D20R, abaqus cant solve the model.
Is it necessary to use of 3D8R element in damage plasticity model in abaqus?
Almost using from 3D8R elements in any FE software can led to higher speed of analysis but achieved accuracy from using of these elements is low. For fully damage plasticity Modelling we should use from other elements such as 3D20R. For using from these elements, thermo mechanical and metallurgical behaviors must be considered. If you use from simple models, it is not necessary to use from other elements if accuracy of results is not very important otherwise you must import mentioned behavior parameters in your analysis and then use from 3D20R elements.
It would be interesting to see your model and understand a little more. However, a couple of points:
1) if you are using the eight-noded solid then you will need more elements than you would if you used twenty-noded solids since the latter has quadratic rather than linear displacement fields.
2) both the elements you mention use reduced integration. You could try changing the integration scheme to 'full' integration and see if that solves your problem.