I have found the data sheet of PA6-GF30, and I have question about the Ultimate Stress and criteria of failure of the material.
In the following pic. whether capital letter Y means the Ultimate Stress (the largest stress) and can i put that value of stress (convert to true stress) as criteria of failure.
OR the failure will occur after the Ultimate Stress the end of necking (The necking is not showed in the below pic.) and because that U.Stress and strain can not be the failure criteria?
I read that the secant module is used for the plastic material, but i do not know when i can utilize that. The secant model of PA6-GF30 is shown the next pic.
If someone knows answer, please tell me.