Name: residual stresses after welding and cooling
Uploaded: 2024-03-07T13:22:39.000Z
Duration: 1 min 26 s
Channel: JoVE

When a rod is stretched beyond its yield point, it permanently deforms and doesn&#39;t regain its original length.
The stresses created during loading are not completely removed even after unloading due to plastic deformations. These remaining stresses are known as residual stresses.
Consider a small plug welded to a large plate. During welding, the plug&#39;s temperature increases significantly, reducing both the modulus of elasticity and stress.
Once the plug cools down after welding, it causes an increase in the modulus of elasticity, and yielding happens at a fairly constant stress level, creating residual stress in the plug and the weld.
The cooling of cast or hot-rolled metals also causes residual stresses. In these cases, the outer layers cool faster than the inner core, causing them to regain their stiffness more quickly.
On returning to room temperature, the inner core gets contracted more than the outer layers, resulting in residual longitudinal tensile stresses at the inner core.
The outer layers develop residual compressive stresses. Large residual stresses are removed through reheating and slow cooling.

residual stresses

Residual Stresses

Residual stresses reside in a structure even after removing the original stress inducer. This phenomenon often arises from varied plastic deformations across different parts of a structure. Consider a rod stretched beyond its yield point. It will not regain its original length due to permanent deformation. Even after load removal, the rod does not entirely lose stress because of uneven plastic deformations, resulting in residual stresses. The computation of these stresses in structures is intricate. Factors like temperature changes during welding can cause plastic deformations, leading to a reduction in elasticity and the generation of residual stresses.
For instance, a plug welded to a plate heats significantly during the process, reducing its stress. As it cools post-welding, its elasticity increases, causing yielding at a constant stress level. This results in residual stress close to the steel&#39;s yield strength. Residual stresses also occur during the cooling of metals after casting or hot rolling. The outer layers cool faster than the inner core, regaining stiffness quicker and leading to tensile residual stresses in the core and compressive in the outer layers. These stresses can be significant, sometimes requiring removal through specimen reheating and slow cooling. Understanding and managing residual stresses is crucial in engineering design and manufacturing processes, ensuring the reliability and durability of structures and components.

When a rod is stretched beyond its yield point, it permanently deforms and doesn&#39;t regain its original length.
The stresses created during loading are ...

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Mechanical Engineering

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Stress and Strain - Axial Loading

KEY TERMS AND CONCEPTS

residual stresses after welding and cooling

Residual stresses are stresses that remain in a structure after the original load or heat source is removed. They often form when different parts of a material undergo uneven plastic deformation, which means permanent shape change. A rod stretched past its yield point is one example. It will not return to its original length, and some stress stays inside even after the load is gone.

These stresses can also develop during welding. Heat changes the material during the weld and can cause plastic deformation. For example, a plug welded to a plate heats up strongly, which reduces its stress. As it cools, its elasticity increases again. The material then yields at a constant stress level, and the residual stress can end up close to the steel yield strength.

Residual stresses are also common after casting and hot rolling. During cooling, the outer layers of metal cool faster than the inner core. The outer layers regain stiffness sooner, while the core stays hot longer. This can leave tensile residual stresses in the core and compressive residual stresses in the outer layers.

These internal stresses can be large enough to matter in engineering design and manufacturing. In some cases, they are removed by reheating a specimen and cooling it slowly. Understanding residual stresses helps improve the reliability and durability of structures and components.

Residual Stresses After Welding and Cooling

residual-stresses-after-welding-and-cooling

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Residual stresses are stresses that remain in a structure after the original load or heat source is removed. They often form when different parts of a material undergo uneven plastic deformation, which means permanent shape change. A rod stretched past its yield point is one example. It will not return to its original length, and some stress stays inside even after the load is gone. These stresses can also develop during welding. Heat changes the material during the weld and can cause plastic...

key terms and concepts

Learn how residual stresses form after stretching, welding, casting, and hot rolling, and why cooling can leave hidden stress inside materials.

Residual Stresses After Welding and Cooling | JoVE K12

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Residual Stresses After Welding and Cooling

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