##  [Residual Stress](/residual-stress-0) 

 Definition

Stresses that remain in a solid body after manufacturing, processing, or thermal treatment when no external mechanical loads or sustained thermal gradients are present; these stresses are self‑equilibrating internal force distributions that may be elastic, plastic or a combination and can vary through the thickness and at microstructural scales.

 

 

 

 

 

 





## Principle

Principle

A body can possess internal, self‑equilibrating stress fields that alter its mechanical response and stability independently of applied loads; these fields arise from incompatible deformations, phase changes, or constrained thermal histories and must be treated as an internal state variable in strength, fatigue and deformation analyses.

 

 

 

 

 





## Demonstration

Demonstration

Illustrative scenario → A welded rectangular steel plate is allowed to cool to uniform temperature after welding. Recognition → Residual tensile stresses concentrate near the weld, balanced by compressive stresses elsewhere. Action → A field measurement (e.g., hole‑drilling or X‑ray diffraction) or cutting a relief cut is performed. Consequence → Removal of a restraining region produces local distortion and measurable stress redistribution, confirming the presence and mechanical effect of residual stress.

 

 

 

 

## Misapplication

Misapplication

Interpreting any observed stress during inspection as a residual stress without excluding contemporaneous external loading or thermal gradients; or assuming residual stress is only a surface phenomenon. The error conflates external (applied or thermal) stresses with locked‑in internal stresses and ignores depth and microstructural variability.

 

 

 

 

 





## Consequence

Consequence

Residual stresses change dimensional stability, alter apparent yield or fracture behaviour, modify fatigue life and crack‑growth rates, and bias experimental measurements of material properties; they can cause unexpected distortion or failure when relieved by machining, welding, or crack propagation.

 

 

 

 

## Reversal

Reversal

Under conditions that permit stress relaxation—e.g., sufficiently high temperature for annealing, sustained creep under load, or intentional mechanical plastic deformation—the residual stress field can be reduced or redistributed; conversely, deliberate processes (shot peening, cold working) can introduce beneficial compressive residual stresses.

 

 

 

 

 





## Boundary

Boundary

Clearly within: self‑equilibrating stress field present in a manufactured part after it is free of external loads and has uniform temperature. Boundary case: a prestressed member where intended pre‑loads produce internal stresses that are part of its design (distinction depends on intent and method of introduction). Clearly outside: externally applied loads, instantaneous thermal gradients, or transient inertial loads acting during service.

 

 

 

 

 





## Semantic Tension

Semantic Tension

Designers may seek to eliminate residual stresses for dimensional accuracy while intentionally creating compressive residual stresses (e.g., by shot peening) to improve fatigue resistance; the tension is between geometric stability and beneficial residual stress engineering.

 

 

 

 

 





## Synthesis

Synthesis

Residual stress is an internal state variable produced by prior incompatible deformations or thermal/phase histories; recognizing it requires measurement or justified assumptions and managing it is an explicit part of design, manufacturing and inspection because it materially changes the mechanical response independent of applied loads.