A Thermoelastic Stress Analysis General Model: Study of the Influence of Biaxial Residual Stress on Aluminium and Titanium

Francesca Di Carolo,Davide Palumbo,Umberto Galietti,Rosa De Finis

doi:10.3390/met9060671

Abstract

All the studies on the thermoelastic behaviour of materials, including the revised higher order theory on the thermoelastic effect, are based on several assumptions that limit the application of such theory to the cases of isotropic materials in the presence of uniaxial residual stresses and undergoing uniaxial applied loads. These assumptions lead to some discrepancies in the description of the real thermoelastic behaviour of materials in the presence of residual stresses. In this work, by rewriting the thermoelastic equation in a different way, it was possible to study the behaviour of homogeneous and non-isotropic materials undergoing any loading conditions and residual stresses. Firstly, the error made by the calibration procedures of thermoelastic stress analysis (TSA) data in the presence of residual stresses has been investigated. Then, a statistical analysis was carried out to determine the minimum value of residual stress which would lead to significant and measurable variations in the thermoelastic signal. The simulations involved two non-ferrous metals: AA6082 and Ti6Al4V, which exhibit a specific thermoelastic behaviour.

Highlights

Thermoelastic stress analysis (TSA) is a well-established, non-contact technique used to assess the superficial stress field exploiting the thermoelastic effect
(13) hasresidual been considered, in which the thermoelastic signal signal is expressed as athis function the principal stresses and their direction with respect to is expressed as a function of the principal residual stresses and their direction with respect to the the applied loads
The proposed to study the of homogeneous non-isotropic proposed.undergoing proposed equation allows to study the By behaviour of equation, homogeneous and materials anythe loading conditions and residual stresses

Summary

Introduction

Thermoelastic stress analysis (TSA) is a well-established, non-contact technique used to assess the superficial stress field exploiting the thermoelastic effect. Real components [4,5], due to the advantages of being contactless, full field, totally safe for the component and not requiring substantial surface preparation In this regard, such a technique is very useful to validate structural finite element modelling (FEM) and to predict stress concentration in real components. Some materials, including steels, do not show sensitivity to this effect, while it is not negligible for non-ferrous titanium and aluminium alloys that are widely used in the design of lightweight structures This result has been widely demonstrated both analytically and experimentally by Wong et al through the revised higher order theory [7,8] showing the possibility to use the TSA for residual stresses estimation [9,10,11,12,13,14,15,16]

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