What is residual stress analysis?
Residual stress is stress that remain in the material after certain fabrication and heat treatment operations. Many products require this stress to be relieved prior to application due to the fact it will affect mechanical, chemical, physical performance of the products.
How does residual stress affect fatigue life?
Residual stresses are known to have a significant effect on fatigue crack propagation and thus fatigue life. Second, the residual stress tends to redistribute away from the crack tip with crack growth, and third, crack growth results in an overall relaxation of residual stress.
Why residual stress is important?
Residual stresses have various effects on the performance of materials. Fatigue, stress corrosion cracking, failures, distortion, structural stability are the common effects. Residual stresses often cause costly hidden problems which effects will be seen during the service life of the components.
What is residual stress in casting?
Residual stresses are developed during the solidification process due to the temperature gradients between different parts of casting or due to the mechanical constraints imposed by the mold during shrinkage of the cast metal and volumetric change and transformation plasticity associated with the solid state phase …
How is residual stress determined?
Surface stress measurements Surface residual stresses can be measured by photo-stress, speckle-shear, and X-ray diffraction techniques. However, X-ray diffraction is the only one that allows measurement of existing surface stresses.
What causes residual stress?
WHAT CAUSES RESIDUAL STRESS? Residual stresses are generated, upon equilibrium of material, after plastic deformation that is caused by applied mechanical loads, thermal loads, or phase changes. Mechanical and thermal processes applied to a component during service may also alter its residual stress state.
How do you relieve residual stress?
Post-weld heat-treatments are often used to relieve or redistribute the residual stresses in a welded object. From a mechanical perspective, techniques such as shot peening, cold rolling, and stretching can be applied to achieve the desired effect.
How does residual stress increase strength?
This layer remained elastic longer than adjacent layers during tension, producing high hetero-deformation induced stress to increase strength and enhancing work hardening even after the disappearance of the compressive stress to increase ductility.
What methods of determination of residual stresses do you think are the most effective?
Stripping is one of the most well-known methods for measuring the residual stress inside a workpiece. The accuracy of the traditional strain gauge method for measuring the internal residual stress is generally 30–50 MPa because of the influence of the strain gauge itself.
How do you determine residual stress?
Residual stresses are determined from the diffraction data by calculating the strain from the diffraction peak positions. The width of the diffracted peak is affected by micro stresses and imperfections in the crystal structure (i.e. dislocations, plastic deformation, etc.).
How does XRD measure residual stress?
Using laboratory-based or portable equipment, the XRD technique measures surface residual stresses to depths of up to 30μm by measuring the material’s inter-atomic spacing.
What happens when internal residual stresses are not removed?
Explanation: When internal residual stresses are not removed, distortion or warpage of the material may occur. Stress relief annealing is carried out to remove these stresses caused by castings, quenching, machining, welding etc.
Can residual stresses improve fatigue resistance?
Ali Fatemi-University of Toledo All Rights Reserved Chapter 8 –Residual Stresses & Their Effects2 RESIDUAL STRESSES AND THEIR EFFECTS ON FATIGUE RESISTANCE • To improve fatigue resistance we should try to avoid tensile mean stress and have compressive mean stress. This can often be achieved by using residual stresses.
What are residual stress and how do they affect welding?
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. In some cases, residual stresses result in significant plastic deformation, leading to warping and distortion of an object. In others, they affect susceptibility to fracture and fatigue.
What is residual stress and why is it important?
What is Residual Stress? 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. In some cases, residual stresses result in significant plastic deformation, leading to warping and distortion of an object.
Does residual stress affect the notch effect?
The residual stresses eliminated the notch effect almost completely. Note that with the residual stresses induced by stretching, the worst notched specimens became much stronger than the best notched specimens without residual stresses. Ali Fatemi-University of Toledo All Rights Reserved Chapter 8 –Residual Stresses & Their Effects7