A Thermoelastic Stress Analysis General Model: Study of the Influence of Biaxial Residual Stress on Aluminium and Titanium (original) (raw)
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Thermoelastic stress analysis of titanium components and simultaneous assessment of residual stress
EPJ Web of Conferences, 2010
The thermoelastic effect describes a linear relationship between change in body temperature and state of stress in the presence of adiabatic conditions. This approach considers the material properties constant with temperature, which is not correct for all materials. Experimental results and a review of the theory, especially for the titanium and some alloys of aluminium, have shown that the thermoelastic signal is also dependent of mean stress of the material. The use of titanium in various fields of application makes interesting use of thermoelastic technique as full field stress analysis technique. However, it is necessary to make a correction of the measure in relation to the mean stress. The possibility to measure the mean stress allows also an evaluation of residual stresses on the surface of titanium components.
Data Correction for Thermoelastic Stress Analysis on Titanium Components
Experimental Mechanics, 2015
Thermoelastic Stress Analysis (TSA) is based on the thermoelastic effect, well described by a linear relationship between change in body temperature and state of stress in the presence of local adiabatic conditions. In TSA material properties are usually considered constant and a peak to peak variation of the state of stress provides a linearly correlated peak to peak temperature variation. For titanium and aluminium alloys thermoelastic properties of materials are not constant and, in fact, the second order effect due to mean stress on thermoelastic signal is not negligible any more. If neglected for these kind of materials, this second order effect could lead to an error that can be higher than 20 %. In this work a new procedure of thermal signal processing is investigated to obtain the corrected thermoelastic data through a new approach based on revised thermoelastic theory.
A review of residual stress analysis using thermoelastic techniques
Journal of Physics: Conference Series, 2009
Thermoelastic Stress Analysis (TSA) is a full-field technique for experimental stress analysis that is based on infra-red thermography. The technique has proved to be extremely effective for studying elastic stress fields and is now well established. It is based on the measurement of the temperature change that occurs as a result of a stress change. As residual stress is essentially a mean stress it is accepted that the linear form of the TSA relationship cannot be used to evaluate residual stresses. However, there are situations where this linear relationship is not valid or departures in material properties due to manufacturing procedures have enabled evaluations of residual stresses. The purpose of this paper is to review the current status of using a TSA based approach for the evaluation of residual stresses and to provide some examples of where promising results have been obtained.
Introduction to thermoelastic stress analysis
Strain, 1999
The theory of thermoelastic stress analysis is reviewed and the assumptions in developing the theory are assessed. The temperature relationship for an isotropic material under plane stress conditions equipment for thermoelastic stress analysis is based on infra-red detection systems. The commercially available
Numerical simulation of stress intensity factors via the thermoelastic technique
Experimental Mechanics, 1997
The purpose of this study is to investigate the accuracy of the least squares method for finding the in-plane stress intensity factors Kt and Kt/ using thermoelastic data from isotropic materials. To fully understand the idealized condition of El and Kzz calculated from thermoelastic experiments, the total stress field calculated from finite element analysis is used to take the place of data obtained from real thermoelastic experiments. In the finite element analysis, the J-integral is also calculated to compare with (K 2 + K21)/E evaluated by the least squares method. The stress fields near the crack tip are dominated by the two stress intensity factors; however, the edge effect will cause inaccuracy of the thermoelastic data near the crack tip. Furthermore, the scan area of thermoelastic experiments cannot be too small. Therefore, we suggest that three or four terms of stress function be included in the least squares method for evaluating stress intensity factors via the thermoelastic technique. In the idealized condition, the error can be smaller than 3 percent from our numerical simulations. If only the r -1[2 term (K I and Kit ) is included in the least squares method, even in the idealized case the error can be up to 20 percent.
Temperature patterns obtained in thermoelastic stress test at different frequencies, a FEM approach
International Journal of Structural Integrity
PurposeThe goal of this work is to create a computational finite element model to perform thermoelastic stress analysis (TSA) with the usage of a non-ideal load frequency, containing the effects of the material thermal properties.Design/methodology/approachThroughout this document, the methodology of the model is presented first, followed by the procedure and results. The last part is reserved to results, discussion and conclusions.FindingsThis work had the main goal to create a model to perform TSA with the usage of non-ideal loading frequencies, considering the materials’ thermal properties. Loading frequencies out of the ideal range were applied and the model showed capable of good results. The created model reproduced acceptably the TSA, with the desired conditions.Originality/valueThis work creates a model to perform TSA with the usage of non-ideal loading frequencies, considering the materials’ thermal properties.
Experimental Mechanics, 2021
Background The Stress Intensity Factor (SIF) is used to describe the stress state and the mechanical behaviour of a material in the presence of cracks. SIF can be experimentally assessed using contactless techniques such as Thermoelastic Stress Analysis (TSA). The classic TSA theory concerns the relationship between temperature and stress variations and was successfully applied to fracture mechanics for SIF evaluation and crack tip location. This theory is no longer valid for some materials, such as titanium and aluminium, where the temperature variations also depend on the mean stress. Objective The objective of this work was to present a new thermoelastic equation that includes the mean stress dependence to investigate the thermoelastic effect in the proximity of crack tips on titanium. Methods Westergaard's equations and Williams's series expansion were employed in order to express the thermoelastic signal, including the second-order effect. Tests have been carried out to investigate the differences in SIF evaluation between the proposed approach and the classical one. Results A first qualitative evaluation of the importance of considering second-order effects in the thermoelastic signal in proximity of the crack tip in two loading conditions at two different loading ratios, R = 0.1 and R = 0.5, consisted of comparing the experimental signal and synthetic TSA maps. Moreover, the SIF, evaluated with the proposed and classical approaches, was compared with values from the ASTM standard formulas. Conclusions The new formulation demonstrates its improved capability for describing the stress distribution in the proximity of the crack tip. The effect of the correction cannot be neglected in either Williams's or Westergaard's model.