Too high stress RD-3595: Three Point Bending

Altair Forum User

Hello,

 

I have a question. Why in tutorial  RD-3595: Three Point Bending the exercise expected results stress is upper than strength material. For example stress in solution is 1,203E+03 (Mpa) so it's 1203 MPa and the Rm (ultimate strength)  Elasto-Plastic Material /MAT/LAW36: Inner, Outer and Flat is 400 MPa?

 

thanks for answer

 

Altair Forum User

Hi,

The ultimate tensile strength or the tensile strength, is the maximum engineering stress level reached in a tension test. Since the UTS is based on the engineering stress, it is often not the same as the breaking strength. In ductile materials strain hardening occurs and the stress will continue to increase until fracture occurs, but the engineering stress-strain curve may show a decline in the stress level before fracture occurs. Moreover in this example the foam material is modelled as honeycomb material, which works well as an energy absorber also takes the load in the model.

Please note that if user is expecting a failure of the material we have to provide the failure parameters in the material card. Please refer RD-3500: Tensile Test Setup using HyperMesh and Example 26 - Ruptured Plate from the Help Menu which are modelled with dedicated failure criteria.