Yield stress and Ultimate stress

Yield Stress:

Yield stress is defined as the lowest stress at which extension of the test piece increases without increase in load. It is the stress corresponding to the yield point. For ductile material yield point is well defined whereas for brittle material it is obtained by offset method. It is also called yield strength. 

Ultimate Stress:  

Ultimate stress or Ultimate strength corresponds to the highest point of the stress-strain curve. It is the ratio of maximum load to the original area of cross-section. At this ultimate point, lateral strain gets localized resulting into the formation of neck.

 ::See Also::

• Stress-Strain diagram for ductile Materials
• Stress-Strain diagram for Brittle Materials
• Stress-Strain diagram for Non-Newtonian Alloy