چكيده به لاتين
Understanding of the principles of classical and quantum physics is very important in studying the behavior of materials. Stress is an important concept in describing the mechanical behavior of solid-state structures. Residual stresses are those stresses that remain in the body after removal of the external forces during manufacturing of industrial components. Such stresses can effectively affect the function of the component, and sometimes they can lead to early failure of the component.
Mechanical stresses can be analysied using two the classical or quantum approach. In the classical approach, stresses are achieved in a systems with macroscopic dimensions of continuous mechanics and molecular dynamics. In the quantum approach, stresses in a system of particles, including electrons and nuclei, are calculated.
The main purpose of this project is to investigate the possibility of developing a non-destructive method for measuring residual stresses in the depths of industrial components. In this regard, physical disturbances on an atomic scale due to the occurrence of stresses in the body are investigated in order to identify a physical parameter to be affected by residual stresses. The Density Function Theory (DFT) is used for this purpose. Models of different sizes of aluminum nanostructures are studied using the computational code of SIESTA. These models are strained of varying degrees, and strain effects on several physical parameters, including strain energy, are studied. In addition, samples of aluminum alloy are prepared and loaded up to the plastic yielding. The mechanical properties and residual stresses are experimentally measured in these samples. Finally, by conducting a literature survay, the ability of laser waves to detect and measure the disturbances caused by residual stresses in the deep bodies is investigated.
The results of the research indicate that the strain energy can be used as a sensitive parameter to the applied strains, and therefore on the residual stresses. The strains applying to an object lead to changes in the strain energy and atomic distances. By measuring the disturbances in the atomic distances of the body, the related residual stresses can be measured.
Keywords: Residual stresses, Density Functional Theory (DFT), Aluminium, and Strain energy.
