Hybridní metody pro měření zbytkových napětí

Abstract

The aim of this dissertation thesis is to determine residual stress using new hybrid methods in mechanics. The theoretical part is focused on the general knowledge related to residual stress followed by the current state of the problems focused on the contour method, the indentation method and the hole-drilling strain-gage method. Special attention is also focused on optical methods. In the first section, a new methodology that evaluates residual stress using the hole-drilling method is described. Its principle lies in the numerical simulation of the gradual material removal and appropriate traction application on the inner surface of the created hole. Based on the experimental data, the values and the directions of the principal residual stresses can be determined using the repeated inverse algorithm calculation. The achieved results are compared with results gained using the ASTM E837-08 standard. A substantial part of the thesis deals with the suitability judgement of the ESPI (Electronic Speckle Pattern Interferometry) optical method with the sensor Q-100 for this issue. Another section deals with the indentation test regarding the residual stress solution. Effort was spent to verify the theoretical observations using a numerical approach by means of FEM. For the detailed study, the experiment was performed using the annealed specimen and the other specimen, where residual stress had been expected. In both cases, specimens are made from the same material. Considering these assumptions, the computational model can be set correctly enough using the inverse approach. Considering residual stress during the indentation test simulation, the subsequent numerical modelling showed new consequences between examined quantities, which could be a topic for further development. The final section is devoted to the contour method. This lesser known progressive destructive method destructive method enables the investigation of the residual stress on the whole area of the cut. The research was mainly focused on the performed experiment and subsequent finite element analysis (FEA). In the broader spectrum of investigation, the issue of the appropriate cutting technique, the technique of capturing surface deplanation, processing measurement data and the boundary conditions in numerical simulation were solved.