Residual stresses are primarily caused by which processes?

• A. External impacts only
• B. Manufacturing processes such as welding
• C. Corrosion
• D. Thermal shock

Answer: (B)

Residual stresses are stresses that remain locked inside a material after it has been manufactured or processed, even when no external load is present. They come from nonuniform heating, cooling, and plastic deformation during processing. The dominant source is manufacturing processes such as welding. In welding, the weld area undergoes rapid heating and cooling while being restrained by the surrounding cooler material. This unequal expansion and contraction causes differential shrinkage, leaving tensile stresses in the weld region (and sometimes compressive stresses in adjacent areas) that persist after cooling. These stresses can influence fatigue life and crack initiation, especially in demanding environments.

External impacts tend to create stresses only while the load is applied and often disappear when the load is removed, unless yielding occurs. Corrosion can later interact with existing stresses to drive cracking, but it does not establish the initial residual stresses. Thermal shock can produce stress from rapid temperature change, but the most common and significant source across components is the processing step itself, particularly welding.