![]() ![]() For example, residual stresses are implemented in the designs of certain applications for positive effects. ![]() What Effects Do They Have?ĭepending on the application, residual stresses can be positive or negative. Once the load is removed, the material tries to recover the elastic part of the deformation, but is inhibited from full recovery due to the adjacent plastically deformed material. When a material undergoes deformation, one part is elastic and another plastic. Residual stress also occurs when plastic deformation is non-uniform through the cross-section of an object undergoing a manufacturing process, such as bending, drawing, extruding and rolling. The volume difference causes expansion or contraction of the material, resulting in residual stress. When a material undergoes a phase transformation, a volume difference between the newly formed phase and the surrounding material, which has yet to undergo phase transformation, occurs. Consequently, the inner portion will have a residual tensile stress and the outer portion of the component will have a residual compressive stress. As the material in the centre tries to cool, it is constrained by the cooler outer material. During cooling, the surface cools at a quicker rate, compressing the heated material at the centre. The differing thermal contractions develop non-uniform stresses. The difference in cooling rates experienced by the surface and interior of the object results in localised variations in thermal contraction. When an object is cooled from a high temperature (eg after welding), there is often a large difference in the rate of cooling throughout the body. There are three primary reasons for these stresses arising: Thermal Variations Residual stresses are generated when an object (especially a welded component) is stressed beyond its elastic limit, resulting in plastic deformation. Click here to see our latest technical engineering podcasts on YouTube. In others, they affect susceptibility to fracture and fatigue. In some cases, residual stresses result in significant plastic deformation, leading to warping and distortion of an object. Residual stresses are those stresses that remain in an object (in particular, in a welded component) even in the absence of external loading or thermal gradients. National Structural Integrity Research Centre.Structural Integrity Research Foundation. ![]()
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