THERMOELASTIC STRESS ANALYSIS BY MEANS OF A STANDARD THERMOCAMERA (original) (raw)
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T h e concept of applying thermomechanical analysis to residual stress investigation is not a new one. Thermoelastic stress analysis, based on the second-order effect, has been used in this role with some success.' However the second order nature of the information makes the technique less than robust, and the expensive infra-red detection equipment required precludes its widespread use. This work investigates a thermomechanical technique that is both robust and inexpensive to implement.
The Added Value of Infrared Thermography in the Measurement of Temperature-stress Coupled Effects
Sensors & Transducers, 2016
The attention of the present paper is focused on the use of infrared thermography to measure the very small temperature variations which are linked to thermo- elastic effects. Hereafter, the latter are associated with material volume variations undergone by a cantilever beam under cyclic bending load. This is a difficult task since the temperature variations can be very small and at the edge of the instrument resolution. The task creates the problem of the infrared camera choice since the sensor should have high thermal sensitivity and low noise, which may be almost impossible to achieve. In fact, a quantum well infrared photodetector (QWIP) is well suited for sensing the small thermal radiation associated with thermo-elastic phenomena, but it is affected by noise, mainly dark current effects, which can be of the same order of magnitude of the quantity to be measured. However, with the aid of a reference sample (reference-area method) it is possible to eliminate most of the instrume...
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A new concept of visual and virtual instrumentation based on infrared analysis of thermoelastic stress is presented in this paper. The parts of the construction where the highest tension occur are determined by the thermal analysis. It is predicted by installing devices for measure the level of strain suffered by excavator construction. Combining thermal imaging techniques with measurements using a measuring tape tension, the great benefit in maintaining these structures can be achieved. Thermal imaging analysis gives a general picture of the distribution of tension. Examined the structure on which the measuring tape to measure the intensity and possible direction of tension action. The TSA also helps to make a numerical analysis faster and in a predictable manner, without need for extensive iterative investigations, what reduces both time and costs. In this paper are shown results of thermal analysis wheel excavator construction.
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Because of the continuous evolution of the market in terms of quality and performance, the mechanical production industry is subjected to more and more pressing technological challenges. In this frame the use of advanced measurement technique as the thermoelasticity, allows the engineers to have a fast and reliable tool of experimental investigation, optimization and validation of the FEM models of those critical parts as for example parts of car frames. In this work it is shown how the thermoelastic measurement technique can be used to optimize mechanical components, as method of experimental investigation and as technique of validation of numerical models. The measurement technique developed for this purpose is described together with the calibration method used in the test benches normally used for fatigue testing and qualification of these mechanical components. The results obtained show a very good deal with FEM models and also the possibility to experimentally identify the concentration levels of stress in critical parts with a very high spatial resolution and testing the effective geometry and structure material.
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.
The “Strain-Gauge Thermocouple”: A novel device for simultaneous strain and temperature measurement
Review of Scientific Instruments, 2001
A novel methodology for simultaneous strain and temperature measurements by means of an ac powered electrical resistance strain gauge connected to a strain conditioner using thermocouple wires is proposed and validated. To this aim a specific device has been designed and implemented; the characteristics of the electronic circuit for signal conditioning have then been tested in order to determine the overall performances in temperature and strain measurements. The field verification of the method is conducted by imposing strain fields in the range from 0 to about 700 m/m and temperature variations in the range from Ϫ10 to 100°C. The difference between the strain measured by the proposed device and the one evaluated by a conventional digital strain meter was always less than 4 m/m while the mean temperature discrepancy was 0.5°C with respect to the reference temperature measured with a K-type thermocouple. Finally, compensation of temperature effects on the actual strain value has been performed while the temperature ranges from ambient to 100°C with a residual error value of 1.4Ϯ1 m/m.