Often, a complete stress-strain history up to final fracture provides pertinent information on material behavior under controlled strain-rate tensile loading. Material properties such as: 1) stiffness as determined by modulus of elasticity; 2) total elongation; 3) total strain to failure; 4) ultimate tensile strength; 5) yield point or yield strength (0.1%, 0.2% offset or 0.5% Elongation Under Load); and 6) material strain hardening after yielding, can be determined by plotting the complete stress-strain history during tensile loading, Figure 1.

Figure 1: Schematic Stress- Strain Diagrams For Two Types Of Material Behavior.

High-sensitivity strain gages, Figure 2, are attached to the reduced section of machined tensile specimens during testing. Micro-strain versus load can then be plotted from data captured by the strain gages for further evaluation.

Figure 2: Strain Gage Attached To Reduced-Section Of Machined Rectangular Tensile Specimen.

 

A typical stress-strain plot generated for ASTM A 572, Gr.50 structural plate is shown in Figure 3.