[moonspell]

Hello everyone. I just finished performing a tensile testing lab in my materials course and was itrigued by the particular behaviour of steel.

My doubt regards the Yield Point Phenomenon for steel. This phenomenon is related to the spike in the stress strain curve right after the daparture from the elastic region. The curve spikes to a max( upper yield point) then lowers down to a plateau (lower yield point), then continues to increase. One of the questions asks us to explain this phenomenon. I'd guess it has something to do with the microscopic stucture of the material (perhaps slip). So if somebody could give me a brief explanation of what is causing this that would be greatly appreciated.

Thanks