Feasible Evaluation of Flow Properties and Stress State of Structural Materials Using Instrumented Indentation Tests

Flow properties and stress state are indispensable factors for safety assessment of structural materials in operation, which were evaluated using instrumented indentation tests (IITs). Flow properties were obtained by defining representative stress and strain, and IIT results for 10 steel materials were discussed by comparing with those from uniaxial tensile tests. The indentation load-depth curve is significantly affected by the presence of residual stress, and the stress-induced load change was converted to a quantitative stress value. The stress state of a friction stir-welded joint of API X80 steel was evaluated and compared with that measured by energy-dispersive X-ray diffraction.