Biaxial residual stress measurement by indentation energy difference method: Theoretical and experimental study.

In this paper, an energy difference method is proposed to estimate biaxial stress components based on indentation technique. The indentation energy is chosen as an analytical parameter, which can be calculated directly from the load-depth curve. The presence of residual stress in a material causes the change of indentation energy. The mapping relationship between uniaxial stress and indentation energy difference was established by finite element analysis. Meanwhile, the Knoop tip was applied since the indentation response varies according to the indenter orientation. Using this feature, a biaxial stress state can be transformed into two equivalent uniaxial stress states by indentation energy conversion. Finally, the biaxial residual stress components can be solved by the energy difference functions of two orthogonal indentations. A portable indentation instrument was developed to implement this approach, which is suitable for in-site measurement. The obtained results show good agreements with the artificial stresses applied by cross-shape sample experiment. • A new methodology is proposed to estimate biaxial stress components based on indentation method. • The Knoop indenter is applied to correlate the stress direction. • A biaxial stress state can be transformed into two equivalent uniaxial stress states by indentation energy conversion. • An indentation testing instrument was developed to validate this approach. • The biaxial stress components can be solved from the load-depth curves, without the need for contact area. [ABSTRACT FROM AUTHOR]