A temperature correction methodology for quantitative thermoelastic stress analysis and damage assessment

Abstract

In thermoelastic stress analysis, an infrared detector is used to obtain the small temperature change resulting from the thermoelastic effect. The output from the detector, known as the thermoelastic signal, is dependent on both the surface stresses and the surface temperature of the component under investigation. For quantitative thermoelastic stress analysis, it is important that the response resulting from changes in the surface temperature is decoupled from the response resulting from the stress changes. In this paper, a means of decoupling the response is presented that involves making corrections for increases in surface temperature so that the thermoelastic signal is dependent only on the stresses. The underlying theory is presented and a correction factor is developed using an experimental approach. A methodology for applying the correction factor to full-field data is provided. The methodology is validated through a number of case studies and applied to a composite component subject to fatigue damage initiated at a central hole.

A generalised approach to the calibration of orthotropic materials for thermoelastic stress analysis

“…It is necessary to temperature correct the data from the test so that it is compatible with the temperature during the calibration. To do this a temperature correction procedure has been developed by the authors [22] that can be incorporated into the calibration analysis routine. From Eq.…”

“…The material properties for the laminate are given in Table 3. The values calculated from these UD laminates can be expected from a single UD lamina and form the basis of the calculation of Q 11 , Q 22 , and Q 12. The shear modulus and the coefficients of thermal expansion are detailed in Table 3 and were taken from values presented in literature [24,25].…”

Identification of the critical load for cyclic loading of shortfibre reinforced PA6 GF30 by a quantitative analysis of the thermoelastic response

“…The measured thermoelastic signal S is developed from this thermal signal S DC , thus the thermoelastic signal S DC changes also non-linearly with the temperature. It was shown by Dulieu-Barton et al [2], that the signal to temperature relation of the thermal signal S DC and the thermoelastic signal S is following a power law. This non-linear influence of the absolute temperature is not for all measuring systems corrected by the supplier of the system.…”

“…The influence of the absolute temperature on the thermoelastic signal S can be corrected either by the application of a correction routine directly on the measured thermoelastic signal S [2]. Another method, used in this work, is to calibrate the thermal signal S DC against the temperature values [3] by measuring the absolute temperature signal S DC at different absolute temperature values and implementing the measured values in a calibration file of the DeltaVision software.…”

Composite Materials for Marine Applications: Key Challenges for the Future

“…A methodology to decouple the response is provided in Ref. [34] that involves making corrections for increases in surface temperature so that the thermoelastic signal is dependent only on the stresses. The thermoelastic response from Shenoi / Composite Materials / 18 orthotropic composite laminates differs significantly to that from homogeneous isotropic materials.…”