Measurement and prediction of quenched-induced residual stress in square bars

摘要

Long, square aluminum bars are quenched on multiple surfaces which produce essentially uniaxial stress fields that vary in two spatial dimensions. The quenches are either symmetric or asymmetric resulting in curvatures about one or two axes, respectively. Displacement transducers monitor the distortion of the bars. Thermocouples measure transient temperature history at selected locations. The complete thermal history, inferred from an inverse calculation, drives the mechanical analysis. Small strain constitutive relationships that span the range from high temperature to room temperature are employed. Two post-quench machining operations are performed. In the first, the bar is sectioned into an array of minibars, each of which yields a value in the residual stress field. In the second, a transverse groove is cut into the bar and strain gages measure the change in strains during the machining process. As in a previous work for one dimensional stress fields, predictions from numerical analyses give a mixed bag of results. Agreement between predicted and measured quench-induced curvature is only qualitative. However, the predicted residual stress field and strain produced from machining agree well with their measured counterparts.