Simulation of Quenching in Aluminium and Comparison With Neutron Diffraction Measurements

Abstract

The through life integrity of engineering components are routinely assessed using complex finite element methods. A critical input to such an assessment is an understanding of the operating environment, including service loading and temperature. Significant effort is expended identifying and understanding the effect of service loads on component integrity however there are many cases where service loading in isolation cannot account for premature failure of components during testing or in-service. A key assumption is that components in the as-built condition are often treated as stress and defect free and of nominal dimensions. This approach can however be inadequate and there are many documented cases where residual stress has influenced the in-service integrity of components. In this paper the magnitude and distribution of residual stresses are investigated in a quenched Aluminium 2014A TB test specimen. The test specimen has been specifically designed to contain design features representative of pressurised aerospace components which are quenched during manufacture. The specimen has two sections, one cylindrical (65mm internal diameter) and one oval (125mm largest internal diameter). The outer wall thickness is 10mm and the overall specimen length is 200mm with the two sections joined by a 30mm bridge section. The specimen has been subject to solution heat treatment at 505°C for five hours. Following heat treatment the specimen is rapidly quenched in cold water at 10°C with the cylindrical end entering the water first. Non-linear finite element methods have been developed to simulate the quenching process making use of user defined subroutines to enhance the standard features available in the finite element code. The accuracy of the predicted residual stresses has been assessed by comparison with neutron diffraction measurements at a range of critical locations. The work provides an extremely useful insight into how non-linear finite element methods can be successfully used to predict the residual stresses that are generated as a result of the quenching process. Where residual stresses are a potential integrity concern an understanding of the magnitude and spatial distribution of residual stress can be used to influence both the design and in-service operation of components.