Determination of biaxial residual stresses via indentation energy difference method
Abstract
<p indent="0mm">In this study, a novel method is proposed to estimate biaxial residual stress (RS) by using the indentation energy difference between the stressed and the stress-free samples. A Knoop indenter is applied along the directions of principal stresses, and the indentation energy obtained from the load-depth (<italic>F</italic>-<italic>h</italic>) curves is used as the calculation parameter without observing the indentation morphology. A work-energy transformation model is constructed to explain the change in the <italic>F</italic>-<italic>h</italic> curve with the RS in terms of energy. Then, the finite element analysis of different power-law hardening materials under different RS combinations is implemented to study the energy evolution. Consequently, the formula for calculating the indentation energy difference under a uniaxial RS is established. Meanwhile, the indentation energy difference of the Knoop indenter exhibits superposition and direction characteristics, which can be used to convert the indentation energy difference under a biaxial RS into the sum of that under two equivalent uniaxial stresses. Through this conversion, the two stress components can be calculated from the two indentation energy difference formulas. An indentation testing device is developed to verify the proposed method. The results obtained using the proposed method agree well with those obtained using the indentation strain-gage method.</p>
