Plastic deformation, or just cracks?

MJCfromCT

Hi everyone,

I'm having a bit of difficulty interperting the results of an ANSYS model I'm currently running. This is of a small, thin piece of metal (0.018" in thickness, ~1"x1" length x width), that I am fixing at one end and displacing the other end ~0.015". Essentially this is a cantiliver plate. On the plate, near the fixed end, are a series of small holes. ANSYS reports that at the boundary of one of the holes, there will be a peak stress concentration of 180ksi. This is when plotting von mises stress. This is about 150ksi higher than what I think this piece can handle.

Is there any way to determine if this piece will plastically deform in the area of the stress concentration, making the stress concentration a non-issue? On the other hand, is there some sort of rule-of-thumb to determine if initiating a crack could be a concern?

Thanks in advance, and I'd be happy to provide any additional information.

PerennialII

For both of your questions I'd start by asking what you know about the material in question with respect to mechanical properties (anything about tensile and fracture mechanical would be a start along with some sort of a "classification" what it is in general). The judgment would have to be done on the basis of stress-strain behavior / limit load and then progress towards a fracture mechanical approach with respect to the crack initiation & propagation part (and under what sort of conditions these might occur .... starting with temperature and such). And also would need to know how you arrived at your stress value, elastic analysis imagine?