Nondestructive Evaluation of Mechanical Properties Using Instrumented Indentation Techniques: Strength, Fracture Toughness, and Residual Stress

摘要

As the demands on structural systems increase, safety evaluation becomes more and more important, and material characterization at system weak points is essential to assess safety accurately. However, general methods such as uniaxial tensile tests and CTOD (crack tip opening displacement) tests are destructive and thus cannot be applied to systems in use. The instrumented indentation technique was developed to overcome this problem. However, current research on this technique focuses on hardness measurements, and its utility in measuring the flow property, fracture toughness, and residual stress has not been sufficiently evaluated. In this paper we introduce evaluation methods for flow properties, fracture toughness, and residual stress near a weldment. The algorithm for flow property evaluation was verified by comparison with experimental and FEA (finite element analysis) results. The fracture toughness model was verified by CTOD results, and the residual stress evaluation model was compared with mechanical cutting results.