Thermoelastic Response of Metals at Different Loading Rates (original) (raw)
Related papers
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.
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.
Materials
This article presents a study on the effect of strain rate, specimen orientation, and plastic strain on the value and distribution of the temperature of dog-bone 1 mm-thick specimens during their deformation in uniaxial tensile tests. Full-field image correlation and infrared thermography techniques were used. A titanium-stabilised austenitic 321 stainless steel was used as test materials. The dog-bone specimens used for uniaxial tensile tests were cut along the sheet metal rolling direction and three strain rates were considered: 4 × 10−3 s−1, 8 × 10−3 s−1 and 16 × 10−3 s−1. It was found that increasing the strain rate resulted in the intensification of heat generation. High-quality regression models (Ra > 0.9) developed for the austenitic 321 steel revealed that sample orientation does not play a significant role in the heat generation when the sample is plastically deformed. It was found that at the moment of formation of a necking at the highest strain rate, the maximum sampl...
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
Metals
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 varia...
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.
American Journal of Engineering and Applied Sciences, 2010
Problem statement: Lifetime of standard dog-bone specimens made form steel as affected by phasing between thermal cycles and strains cycles and by cycle duration in thermomechanical fatigue is assessed under various conditions of loading. Approach: The methodology used was based on finite element post-processing analysis by specialized fatigue software package that takes into account coupling of damage from three primary sources: Fatigue, oxidation and creep. Results: A parametric study has been conducted for various thermomechanical loadings and effects of phasing and cycle duration on lifetime have been evaluated. The associated percentages of damage mechanisms due to fatigue, oxidation and creep have been determined. Conclusion: It has been shown that both phasing and cycle duration have considerable effect on lifetime. In the range of parameters investigated, the in-phase cycles were found to reduce considerably damage in the specimen for low pressures and low temperatures. The results have shown also that there was no way of unique comparison of the various phasing configurations, since there exists always a case of thermomechanical loading for which one phasing configuration yields higher damage than any another configuration.
Journal of Imaging, 2016
Stainless steels are the most exploited materials due to their high mechanical strength and versatility in producing different alloys. Although there is great interest in these materials, mechanical characterisation, in particular fatigue characterisation, requires the application of several standardised procedures involving expensive and time-consuming experimental campaigns. As a matter of fact, the use of Standard Test Methods does not rely on a physical approach, since they are based on a statistical evaluation of the fatigue limit with a fixed probabilistic confidence. In this regard, Infra-Red thermography, the well-known, non-destructive technique, allows for the development of an approach based on evaluation of dissipative sources. In this work, an approach based on a simple analysis of a single thermographic sequence has been presented, which is capable of providing two indices of the damage processes occurring in material: the phase shift of thermoelastic signal φ and the amplitude of thermal signal at twice the loading frequency, S2. These thermal indices can provide synergetic information about the mechanical (fatigue and fracture) behaviour of austenitic AISI 316L and martensitic X4 Cr Ni Mo 16-5-1; since they are related to different thermal effects that produce damage phenomena. In particular, the use of φ and S2 allows for estimation of the fatigue limit of stainless steels at loading ratio R = 0.5 in agreement with the applied Standard methods. Within Fracture Mechanics tests, both indices demonstrate the capacity to localize the plastic zone and determine the position of the crack tip. Finally, it will be shown that the value of the thermoelastic phase signal can be correlated with the mechanical behaviour of the specific material (austenitic or martensitic).
Analysis of nonisothermal tensile tests using measured temperature distributions
International Journal of Plasticity, 1987
Finite element modeling (FEM) of nonisothermal sheet tensile tests has been performed. The effect of deformation-induced heating was incorporated into an isothermal FEM program in two ways: (1) an experimentally measured temperature distribution was used to modify the plastic response of each element and (2) adiabatic heating was enforced by setting net heat production in each element equal to the work of deformation. For a specimen with a i ~/0 taper, these models predict up to a 7~0 reduction in ultimate elongation for adiabatic tests relative to isothermal ones. These heat transfer conditions were approached at strain rates greater than 10-2/s and less than lO-4/s respectively. Comparison of these models with experiment suggests that the two extreme approximations can be used, except for a relatively narrow range of rates, to provide good first-order estimates of the heating effect on ductility without the need for cumbersome self-consistent heat transfer calculations. For mild steel sheet specimens tested in still air, the critical strain rate range is near the typical testing rate, making interpretation of standard tests difficult.