Residual stresses created during the manufacturing process can lead to stress corrosion cracking, distortion, fatigue cracking, premature part failure, and instances of over design. The nondestructive nature of the x-ray diffraction (XRD) technique has made the residual stress characterization of power generation components a useful tool for process optimization, design improvements, and failure analysis.
Aggressive or abusive machining can create regions of tensile stress that can make certain areas of a component susceptible to crack initiation and increase the rate of crack propagation.
The residual stress state is critical when stress concentration geometries exist that can magnify the effects of applied loads. When issues of fatigue cracking are considered, potentially harmful tensile residual stresses alone or in combination with stress concentrations can lead to fatigue crack initiation and propagation.
The fatigue life of a component is often enhanced by cold-working processes such as shot peening. XRD residual stress measurement can be used to verify that these locations have been enhanced to the specified residual stress level. A residual stress value, once established, can be specified on the engineering and processing documents.
Following a “Design to RS, produce to RS, and manage to RS” philosophy helps to achieve reduced component weight, improve life expectancy, and lower manufacturing and maintenance costs.
Measuring residual stress on a turbine blade
Measuring residual stress on a nuclear reactor coolant pipe
