Residual stress plays an important role in many of the issues found in pipelines, such as stress corrosion cracking (SCC), hydrogen induced cracking (HIC), fatigue cracking, welding stresses, heat treatment effectiveness, surface enhancements due to cold work, ending due to seismic activity, and installation stresses. The significant effect that residual stress has on the performance and life of a component makes it extremely important to characterize these stresses.
The full benefit of a design can only be achieved when favorable residual stresses have been introduced into a component and harmful residual stresses have been minimized. X-ray diffraction is a portable, non-destructive, quantitative, highly accurate, and robust method to quantify residual stress. Modern equipment makes it quick and easy to do measurements in the laboratory, in line, and in the field. Proto’s portable measurement systems enable measurements to be easily performed on pipelines in the field.
Residual stresses created during the welding process can lead to stress corrosion cracking, distortion, fatigue cracking, premature failures in components, and instances of over design. The nondestructive nature of the x-ray diffraction technique has made the residual stress characterization of welds a useful tool for process optimization and failure analysis, particularly since components can be measured before welding, after welding, and after post-welding processes have been applied.
Peening effectiveness is normally characterized via the Almen intensity and the % coverage. It should be noted that many potentially different residual stress gradients can result from what may appear to be the same deflection of the Almen strip and observed % coverage. The % coverage is an optical assessment of the as-peened surface and is generally thought of as a measure of the uniformity of peening on the component surface.
3D printing is increasingly being used as an alternative method of manufacturing components. In particular, replacement parts that were manufactured via traditional methods such as casting are now being made using additive manufacturing processes. While a printer can produce a dimensionally identical part, the process may not produce the same residual stress distribution in the part.
The weight of the concrete and the steel superstructure in a bridge, and thus the resultant dead load in each of the critical members, are well known when the bridge is initially constructed, assuming all goes to plan. However, major maintenance, repair, or any significant damage to the structure can cause the loads to redistribute and thus change the dead loads and the load path.
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.
Residual stresses play a key role in the life of aerospace structures. Proto provides both measurement services and x-ray diffraction residual stress measurement instruments, enabling our customers to obtain residual stress measurements in the lab or in the field on various aerospace components.