Residual stresses are primarily caused by which processes?

• A. Residual stress
• B. Structural stress
• C. Pressure stress
• D. Flow stress

Answer: (A)

Residual stresses are the stresses that remain locked inside a material after it has been processed and external loads are removed. They come from processes that create nonuniform strain, especially those involving heat input and restraint, such as welding, quenching, casting, forming, machining, and surface finishing. When different regions heat, cool, or plastically deform at different rates, they tend to move by different amounts. The surrounding material resists these movements, so internal forces balance in a way that leaves residual stresses behind. These stresses can affect dimensional stability, fatigue life, and crack behavior.

Other terms describe different ideas. Structural stress refers to stresses arising from a component’s geometry and service loads, not from processing; pressure stress comes from external or internal pressures acting on a structure; flow stress is a material property describing how hard it is for a material to flow plastically. They aren’t the primary sources of the residual stresses introduced during manufacturing.