Re: Stress-srain graphs for these properties..

Dear friend,

I do not specifically know what it means to have a stiff-non ductile material. What I am sure about is that stiff equally means brittle. An example for brittle materials are ceramic materials and cast iron. These materials can withstand high compressions but they are weak in tension. I think you can find more by searching for stress-strain curves for these materials on the net.

For ductile materials, the best example is aluminum. Ductile materials are strong in tension, yet weak in compression. They can withstand a long plastic range of deformation without fracturing. The typical stress strain curve is composed of three regions. The first region is called the elastic region where stress is directly proportional to the strain. The slope of the straight line relations gives the well-known Young's Modulus. The second region is called the plastic zone where the material starts yielding. The relation between stress and strain is exponential at this zone.It is accompanied by the so called strain hardening, where the stress increases with the strain because the material resists failure. Until we reach to a maximum value for the stress called the ultimate stress. At that point, the material is in its way to break.

For brittle materials, the elastic range is the largest. There are almost no other ranges because the material breaks when it leaves the elastic zone.

On the other hand, ductile materials they have the three regions because they pass by the three regions before they fracture.

You can check this link for further information:
http://darkwing.uoregon.edu/~struct/courseware/461/461_lectures/461_lecture24/461_lecture24.html