Effect Of Strain Hardening Exponent Research Articles

Assessment of the Local Residual Stresses of 7050-T7452 Aluminum Alloy in Microzones by the Instrumented Indentation with the Berkovich Indenter

The local residual stresses in microzones are investigated by the instrumented indentation method with the Berkovich indenter. The parameters required for determination of residual stresses are obtained from indentation load–penetration depth curves constructed during instrumented indentation tests on flat square 7050-T7452 aluminum alloy specimens with a central hole containing the compressive residual stresses generated by the cold extrusion process. The force balance system with account of the tensile and compressive residual stresses is used to explain the phenomenon of different contact areas produced by the same indentation load. The effect of strain-hardening exponent on the residual stress is tuned-off by application of the representative stress $$\sigma_{0.033}$$ in the average contact pressure assessment using the $$\varPi$$ theorem, while the yield stress value is obtained from the constitutive function. Finally, the residual stresses are calculated according to the proposed equations of the force balance system, and their feasibility is corroborated by the XRD measurements.

Theoretical and experimental analysis of sheet metal formability limits

The formability of sheet metals can be assessed by the forming limit diagram (FLD). In this study, a theoretical model is introduced for calculating the FLD. A « many slice » approach is used to simulate neck growth. The effect of strain-hardening exponent (n ), strain rate sensitivity (m ), anisotropy parameter (r ) and grain size (d ) have been investigated. Also, the FLDs of ST12 steel sheet with different grain sizes have been experimentally determined. It is shown that the FLD is quite sensitive on n, m, r and d. The model prediction is compared with the experimental results.