On the Accuracy of Finite Element Models Predicting Residual Stresses in Quenched Stainless Steel

Israel Medina-Juárez,Richard J Moat,Francisco Alfredo García-Pastor,Jeferson Araujo De Oliveira

doi:10.3390/met9121308

Abstract

Prediction of residual stress profiles after quenching is important for a range of industry applications. Finite element method (FEM) models have the capability of simulate the cooling and stress evolution during quenching; however, they are very dependent on the heat transfer coefficient (HTC) imposed on the surface. In this paper, an analysis of the HTC effect on the accuracy of the residual stress profile after quenching a 304L stainless steel Jominy sample was conducted. The FEM model was validated in its thermal accuracy using thermocouples and the residual stress profile was measured using the contour method. The results show that a thermally validated FEM model may yield results which overestimate the tensile residual stress and underestimates the compressive residual stress maxima while accurately calculating the maxima positions from the quenched edge. The FEM model accuracy was not improved by modifying the HTC or by using a different thermal expansion coefficient. The results are discussed in terms of the effect of plasticity due to twinning in the residual stresses calculated by the FEM model.

Highlights

There are numerous industrial applications where residual stresses generated during manufacturing affect the mechanical properties and fatigue life of structural and sensitive elements [1].The generation of residual stress in most manufacturing processes such as forming, rolling and welding, can be difficult to model because the complexity of decoupling stressed generated by thermal, deformation, and transformation mechanisms
The Finite element method (FEM) quenching model was validated in its thermal accuracy by comparing simulated and experimental cooling curves
It can be seen that there is a good agreement between the temperature values experimentally measured and those calculated in DEFORM 3D FEM

Summary

Introduction

The generation of residual stress in most manufacturing processes such as forming, rolling and welding, can be difficult to model because the complexity of decoupling stressed generated by thermal, deformation, and transformation mechanisms. Quenching consists of rapid cooling usually by means of immersion of a hot part in a medium, such as water or oil, generating steep temperature gradients between the surface and the center of the part. As a result of the rapid cooling, a temperature gradient is established between the part surface and center. This temperature gradient, in turn, generates a thermal stress gradient which leads to a residual stress distribution after quenching is concluded. The precise distribution and magnitude of the obtained stress profile will depend on factors such as: part geometry, material-related phase transformations and heat transfer coefficient (HTC)

Methods

Discussion

Conclusion