![]() They may develop naturally during processing or treatment, or may be introduced deliberately to develop a particular stress profile in a component ( Brien, 2000). Mechanically generated residual stresses are often a result of manufacturing processes that produce non-uniform plastic deformation. The origins of residual stresses in a component may be classified as: mechanical, thermal and chemical. ![]() In general, residual stresses are beneficial when they operate in the plane of the applied load and are opposite in sense (i.e, a compressive residual stress in a component subjected to an applied tensile load). Both magnitude and distribution of the residual stress can be critical to the performance that should be considered in the design of a component.Tensile residual stresses in the surface of a component are generally undesirable since they can contribute to the major cause of fatigue failure, quench cracking and stress- corrosion cracking.Ĭompressive residual stresses in the surface layers are usually beneficial since they increase fatigue strength, resistance to stress-corrosion cracking, and increase the bending strength of brittle ceramics and glass. For this reason it is vital that some knowledge of the internal stress state can be deduced either from measurements or modeling predictions. The residual stresses may be high enough to cause local yielding and plastic deformation on both microscopic and macroscopic level, that can severely affect component performance. ( Withers & Bhadeshia, 2000 Rudd,1992 Borland, 1994 Kandil et. They arise from a number of sources and can be presented in the unprocessed raw materials, and can be introduced during manufacturing or can arise from in-service loading. Residual stresses developed during most manufactured processes involving metal forming, heat treatment and machining operations deform the shape or change the properties of a material. The modeled welding materials are aluminum and titanium alloys concerning flat and cylindrical shapes. Approximating the mechanisms of the transient temperature and longitudinal residual stress after temperature modification can be made. That can be achieved by using different methods of the mitigation technique which work as heat transfer enhancement. The purpose of this chapter is to develop Finite Element models that satisfy the analysis of the behavior of transient phenomena of residual stress and distortion. However, development of the modeling scheme gain demands a careful experimental data. Mathematical modeling for residual stress evaluation provides a resource effective method in comparison to the experimental methods when all interaction fields were correctly described in the modeling process. On the other hand, detailed experimental measurements of the residual elastic strain distributions in welded parts are typically not feasible due to significant resource (man, machine and material) consumption. It often fails to provide a complete picture of temperature and stress/strain, deformation distribution in the weldment. Measurement of transient thermo-mechanical history during welding process is of critical importance, but proves to be prohibitively expensive and time consuming. In welding design, the study and analysis of welding residual stresses and distortion become necessary in critical industries such as: aerospace engineering, nuclear power plants, pressure vessels, boilers, marine sector….etc. Correction of unacceptable distortion is costly and in some cases, impossible. ![]() In addition, it causes defaults during the assembly which result in repeating the process and productivity restriction. ![]() Welding deformation is undesirable owing to the decrease in buckling strength and injures the good appearance of structures. High tensile residual stresses are undesirable since they can contribute in causing fatigue failure, quench cracking and stress- corrosion cracking of welded structures under certain conditions. Transient thermal stresses, residual stresses, and distortion sometimes cause cracking and mismatching of joints. This is particular when fabrication involves the use of thin section sheet materials, which are not inherently stiff enough to resist the contraction forces induced by welding. As a result, residual stress, strain and distortion are permanently produced in the welded structures. Thus, result in plastic deformation in the weld and surrounding areas. The highly localized transient heat and strongly non-linear temperature fields in both heating and cooling processes cause non-uniform thermal expansion and contraction. In addition to that, cost savings, reduced overall weight and enhanced structural performance. Welding, among all mechanical joining processes, has been employed at an increasing rate for its advantages in design flexibility. ![]()
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