Papers by Keyword: Strain-Hardening Exponent

Abstract: The compressive strain hardening behaviour of a novel bimetal with pearlitic steel and low carbon steel was investigated by computational analysis based on the isothermal compression tests in a wide range of deformation temperature and strain rate. The Hollomon’s equation was employed to calculate the strain hardening exponent (SHE) with the assistance of mathematical manipulation. The result shows that the logarithmic relationship between the flow stress and plastic strain of the bimetal is highly non-linear, which results in the variation of the SHE of the bimetal. This variation reflects the dynamic competition between the strain hardening and softening mechanism by the varying value of the SHE in the range of 0.4 to-0.4. Furthermore, the influences of deformation temperature and strain rate on the SHE are significant. With decreasing temperature and increasing strain rate, the strain hardening of the bimetal was enhanced, while the dynamic recrystallisation was activated under the opposite conditions with the evidence of negative SHE value.

Abstract: Through dimensional analysis of indentation parameters in this study, we propose an artificial neural network (ANN) model to extract the residual stress and strain-hardening exponent based on spherical indentation. The relationships between indentation parameters and the residual stress and material properties are numerically calibrated through training and validation of the ANN model. They enable the direct mapping of the characteristics of the indentation parameters to the residual stress and the elastic-plastic material properties. The proposed ANN model can be used to quickly and effectively determine the residual stress and strain-hardening exponent.

Abstract: The Variation of the mechanical properties of coiled tubing with increasing of the bending cycles was studied based on the fatigue bending cycle machine. The results show that the tensile strength had no significance changes during cycle fatigue. The yield strength and the force value was significantly decreased after 300 cycles, and the corresponding decreased magnitude linearly increased with the increasing of bending cycles. The changing tendency of strain hardening exponent on compression surface is different from the one on extruded surface. When the cycles increase from 100 to 600, the exponent on compression surface shows increases firstly, and decreases afterwards, However, the one on extruded surface shows decreases firstly, and increases afterwards. The yield strengths of the compression surface and extruded surface show the same changing tendency as strain hardening exponent.

Abstract: In this study, we have used the FE method to investigate the effect of in-plane residual stress and strain-hardening exponent on the indenter load, indentation work and residual depth. Based on the reverse analysis, the 304 stainless steel’s residual stress and strain-hardening exponent can be measured fromone simple indentation test by using spherical indenter. The comparison between residual stress or strain-hardening predicted from reverse analysis and the input residual stress or strain-hardening used in numerical indentation experiments shows good agreement.

Abstract: An indentation method to determine equi-biaxial residual stress is proposed by examining the data from the incremental plasticity theory based FE analyses. We found that hardness is strongly dependent of the magnitude and sign of residual stress and material properties. We then selected some normalized parameters minimally affected by material properties and tip radius. With numerical regressions of the data obtained, we proposed new formulae for residual stress evaluation. The new approach provides a substantial enhancement in accuracy compared with the prior methods.