Full-range Stress-strain Curves for Stainless Steel Alloys (No. R811)

The report develops an expression for the stress-strain curves for stainless steel alloys which is valid over the full strain range. The expression is useful for the design and numerical modelling of stainless steel members and elements which reach stresses beyond the 0.2% proof stress in their ultimate limit state. In this stress range, current stress-strain curves based on the Ramberg-Osgood expression become seriously inaccurate principally because they are extrapolations of curve fits to stresses lower than the 0.2% proof stress. The extrapolation becomes particularly inaccurate for alloys with pronounced strain hardening. The report also develops expressions for determining the ultimate tensile strength (σu) and strain (εu) for given values of the Ramberg-Osgood parameters (E0,σ0.2,n). The expressions are compared with a wide range of experimental data and shown to be reasonably accurate for all structural classes of stainless steel alloys. Based on the expressions for (σu) and (εu), it is possible to construct the entire stressstrain curve from the Ramberg-Osgood parameters (E0,σ0.2,n)