Hi!

I am investigating the effect of triaxial stress state on the superelastic behavior in NiTi. In this regard I have conducted some simple tensile tests on notched specimen until fracture. The next step is to investigate the fracture surfaces in SEM to determine point of initiation and the structures. However, as my knowledge in fractography is limited at best, I am not really sure what to look for to determine eg. fracture initiation.

Can anyone say wether there exists a reliable way to determine fracture initiation points by SEM, or if there are some good papers that cover this issue that I should know about?

Regards

 Jim S. Olsen

I am working with shape memory alloys (nitinol), and am in that respect investigating fracture behaviour of NiTi, using, among other things, simulations in ABAQUS. ABAQUS doesn't have a material model that include plasticity unless you pay for it. I am wondering if anyone have implemented either of the following models as a UMAT, and if you are willing to share the code with me.

The models I am interested in are: