There are so many residual stress caused during machining：

Casting residual stress;

Welding residual stress;

Pressure Processing residual stress; 

Cutting residual stress; 

Heat Treatment residual stress; 

Coating residual stress; 

Surface hardening residual stress; 

Casting residual stress and case:

Castings may also have large residual stresses due to uneven cooling. Residual stress is often a cause of premature failure of critical components, and was probably a factor in the collapse of the Silver Bridge in West Virginia, United States in December 1967. The eyebar links were castings which showed high levels of residual stress, which in one eyebar, encouraged crack growth. When the crack reached a critical size, it grew catastrophically, and from that moment, the whole structure started to fail in a chain reaction. Because the structure failed in less than a minute, 46 drivers and passengers in cars on the bridge at the time were killed as the suspended roadway fell into the river below.

Welding residual stress and case:

In the process of welding,the welding stress and deformation produced mainly causes of welding parts of uneven heating and cooling.

Precision components, which are machined or aligned to tight dimensional or geometric tolerances. Examples include machine tool bases or columns, components of paper mill, mining equipment, or other large-scale processing machinery, and centrifuge rotors.

Heavily loaded metal workpieces, which are components designed and built with the ability to withstand heavy loads. Examples include lifting yokes, clamshell buckets, crane bases, vibratory screening system frames, ingot processing, and rolling mill equipment.

These stresses, called residual stresses,because they reside within the metal workpiece, rather than as a result of external loading, are caused by rapid, unequal cooling. This unequal cooling occurs during welding, casting, forging, rough machining or hot rolling. These stresses often lead to distortion or warping of the structure during machining, assembly, testing, transport, field-use or over time. In extreme cases, residual stress can cause structural failure.

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