MSN-C has successfully showcased a new, comprehensive workflow to map residual strain on a challenging set of near-net-shape additive manufactured parts. This achievement signals MSN-C’s readiness to conduct such measurements for the broad community of academic, government and industry scientists and engineers seeking to understand and control failure in high performance structural components. Routine access to this kind of information now available at MSN-C holds great potential value for both DoD and commercial manufacturing.
Background
Residual stress refers to internal stresses that remain within a solid object in the absence of external applied loads. In structural components, especially metallic parts that support static or cyclic loads, residual stresses can significantly impact mechanical performance. Whether the presence of residual stress is beneficial or detrimental to mechanical response depends on details such as the sign, magnitude, and direction of residual stress, location and distribution throughout the part, and application conditions of how the part is loaded in service. Residual stress is also an important consideration during the manufacturing process; this is particularly true for developing additive manufacturing processes such as laser powder bed fusion, where generation of significant residual stresses during the build process can lead to distortions in part geometry or total build failure. In general, residual stress is a key consideration in mechanical design and engineering.
Because of the critical link to performance, the aerospace industry is deeply concerned with residual stress, and invests heavily in ways to model, measure, and engineer the presence or absence of residual stress for the vast array of components that comprise products like engines and aircraft. Despite significant innovation in these areas, however, a persistent challenge remains in developing a best practice for quantitative measurement of residual stress.
Stress cannot be measured directly, but rather can be calculated using Hooke’s Law from measurements of elastic strain when combined with knowledge of the elastic properties of the material. X-ray diffraction provides a means of directly measuring the elastic strains of a crystal by comparing the spacing of crystallographic lattice planes to those of an unstrained reference. Performing such measurements at a high energy synchrotron facility such as CHESS enables orders-of-magnitude greater efficiency and fidelity of elastic strain measurements, representing a great opportunity for addressing residual stress challenges.
MSN-C was founded in large part to develop and devote synchrotron-based methods to address challenges facing advanced manufacturing, including determination of residual strain.
Read more on CHESS website
Image: Five additive manufacturing samples mounted simultaneously with a calibration sample. A red dot from the laser that is used to measure the specimen surface is visible on the printed fan blade.