Normal and shear stresses estimation in deformed metals based on infrared thermography data

The work is dedicated to the development and implementation of numerical-experimental method of evaluation of the stress and strain components on the base of infrared thermography. The infrared thermography is a non-contact method of visualization and measurement of temperature fields of objects. It could be used as a method of non-destructive testing. A program complex which could be used for the evaluation of the individual components of stress and strain is developed on the base of the solution of the boundary value problem and data of the sample temperature change caused by the thermoelastic effect. In order to verify the proposed method, a series of experiments on quasi-static tensile of specimens from structural steel 8X18H10 and titanium alloy VT1-0 with the stress concentrators were carried out. As a result, it is shown that in contrast to the similar approaches (e.g., TSA-Thermal Stress Analysis) the method allows us to obtain additional information about stress-deformed state of the material and to conduct a more detailed assessment of the degree of the critical state of the structure. The methodology of the proposed method is based on the experimental measurement of the first invariant of the stress tensor using the infrared scanning technique and its subsequent recalculation to determine boundary conditions. This allows us to identify all stress components at any point in the considered area of specimens or construction on the base of the numerical solution of the corresponding boundary value problem. Special feature of the developed approach is a small computational cost for the determination of the stress components, which allows using this technique in the analysis of a wide class of engineering structures in real time.