September_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 2 0 3 3 It is often thought that residual stresses arising from surface treatment processes are completely beneficial. This is not always the case. For exam- ple, if a component is surface processed to produce a high level of compressive stress by peening, there will be a sub- surface value that will be in tension. If the volume of material is externally loaded further in cyclic tension during service, it could lead to reduced perfor- mance and compromised component fatigue life. Figure 7 shows a schematic of such impact to the cyclic loading be- havior of a material. This is a result of having a superposition of the residual and applied stresses, and local shift in R-ratio for the cyclic loading. If not ad- equately considered during the design, this could result in reduced product life. TECHNICAL COMMITTEE EFFORTS Residual stresses are not limit- ed to metallic materials. They can ex- ist in all classes of materials, including coatings, polymer matrix composites, and even ceramic matrix composites. Many ASM members and organizations have an interest in residual stress. To this end, ASM International recent- ly initiated a new technical commit- tee on the topic. The committee was formed in January with approximate- ly 35 initial ASM members from many organizations including: Air Force Re- search Laboratory, ANSYS, Cummins, Curtiss-Wright Surface Technologies, General Electric, Hill Engineering LLC, Howmet, Kaiser Aluminum, Lockheed Martin, Oak Ridge National Laborato- ry (ORNL), Pratt & Whitney, Proto Man- ufacturing Inc., Quaker Houghton, Rolls-Royce Corp., TEC Materials Test- ing, Universal Technologies Corp., Uni- versity of Connecticut (UCONN), Weber Metals, Worcester Polytechnic Institute, and ASM International. This committee’s work is aimed at furthering understanding and suc- cessful utilization of residual stresses in component and manufacturing pro- cess design, and associated assessment and control. The committee current- ly has three major subcommittees, fo- cused on education (led by Jeffrey Bunn of ORNL), conference symposia (led by Lesley Frame of UCONN), and indus- try standards (led by Dale Ball of Lock- heed Martin). The education efforts are aimed at gathering available information that can be compiled into training programs that may include a high-level overview of residual stress, measurement meth- ods, modeling and prediction meth- ods, manufacturing process controls, and others. Initial elements have been assembled into an introductory pre- sentation, where a subset is being intro- duced at a few ASM Chapter meetings. Further work will continue until the committee has sufficient material to al- low proposing a new formalized educa- tional program with the ASM Education Committee. The committee had been work- ing to develop a symposium on residu- al stress for IMAT 2020, which now will be targeted for IMAT 2021. The sub- committee is also looking to drive in- terest in focused talks at AeroMat 2021 and the International Conference on Fracture (ICF15) in 2021. The commit- tee encourages submission of abstracts on residual stress to these upcoming conferences. The committee is also looking to further rally the industry around the topic and develop industry standards. Fig. 7 — Schematic of fatigue behavior of peened and nonpeened material for a specific nominal R-ratio. Peening shows clear ability to improve LCF capabilities over nonpeened, but as stresses are lowered the HCF life of peened material can show a debit over nonpeened due to interactions of applied and internal tensile residual stresses.