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Materials
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
The most common and versatile of the cold-working treatments is shot peening. It is widely used with springs, gears, shafts, connecting rods, and many other components. In shot peening, the surface is bombarded with high-velocity iron or steel shot (small, spherical pellets) discharged from a rotating wheel or pneumatic nozzle. The process leaves the surface in compression and alters its smoothness. Since fatigue cracks are not known to initiate or propagate in a compression region (see Section 7.1), shot peening has proven very successful in raising the fatigue life of most members. Machine parts made of very high-strength steels (about 1400 MPa), such as springs, have particularly benefited. Shot peening has also been used to reduce the probability of stress corrosion cracking in a turbine rotor and blades.
Lubrication and Coating Challenges in Extreme Conditions
Published in Ahmed Abdelbary, Extreme Tribology, 2020
Shot peening is a surface modification process that can improve substrate material properties of hardness, wear resistance, corrosion resistance and fatigue, thus improving the product’s service life. By using shot peening, the service life of springs can increase by 400% to 1200%, depending on the extent of peening already imparted on the spring. Shot peening processes can also increase the fatigue life of gears by over 500%. Figure 9.10 illustrates the general process of shot peening, where a stream of round hardened steel shot or similar is propelled onto the surface during the process. The presence of this surface compressive stress serves to retard the initiation and growth of fatigue cracks.
Metal additive manufacturing using lasers
Published in Rupinder Singh, J. Paulo Davim, Additive Manufacturing, 2018
C. P. Paul, A. N. Jinoop, K. S. Bindra
Property enhancements can be done with non-thermal techniques, such as shot peening. Shot peening is a mechanical surface treatment technique in which small balls are impacted on the surface of a component. The repeated impacts of the balls induce compressive residual stress and refine the microstructure. This helps in delaying the crack initiation and hinders the crack propagation [87]. Thus, the mechanical properties and microstructure can be tailored as per the requirement by shot peening. Infiltration is another post-processing technique used in laser-sintered components. Porous LS part is heated in contact with the infiltrant to a temperature at which the infiltrant is molten and will soak into the part through capillary action. The infiltrant solidifies on cooling and produces the final part. The significant attention is on the ability of the infiltrant to wet the solid preform and form the dense solid [88]. The strength of the structure after infiltration is a function of the time period of infiltration as shown in Table 2.5.
The Effect of Shot-Peening Time on Tribological Behavior of AISI5160 Steel
Published in Tribology Transactions, 2022
Xue Han, Zhenpu Zhang, Bo Pang, Gary C. Barber, Jianxin Zhao, Feng Qiu
Shot peening is a type of cold-working process that is a well-known mechanical surface treatment to improve the fatigue strength of metallic components, so it is widely applied in aerospace, automotive, and power generation industries (1–3). Generally, the shot-peening process is accomplished using 0.25-mm to 1-mm diameter cast iron, steel, or glass spherical shots continually bombarding the surface of components at speeds from 20 to 150 m/s (4). During this process, plastic deformation is produced and leads to a hardened surface. When the plastic deformation area expands to other areas, it is constrained by the adjacent deeper material. Then compressive residual stress is produced (5, 6). The shot causes strain hardening and grain deformation, which leads to modified mechanical properties of the components (7). The factors that affect shot peening are that (1) shot peening produces dents, which result in high roughness and stress concentration points; (2) the small balls continuously hit the surface and produce plastic deformation, so a hardened layer with lower ductility is produced on the surface; (3) the grain size may change from micro- to nanometers; (4) the deformation may cause phase transformations, such as the transformation of metastable austenite to martensite; and (5) compressive residual stress is produced (8–13).
Accuracy of X-ray diffraction measurement of residual stresses in shot peened titanium alloy samples
Published in Nondestructive Testing and Evaluation, 2019
Xuesong Fu, Zhiqiang Niu, Ying Deng, Jie Zhang, Chongyuan Liu, Guoqing Chen, Zhiqiang Li, Wenlong Zhou
Ti-6Al-4V(TC4) is widely used in gas-turbine engine as discs and blades because of its excellent specific strength, good corrosion resistance property and outstanding machinability. However, the blade root and disk are subjected to alternating loads during flight, resulting in fatigue and wear. Fatigue can reduce engine life and cause great economic loss. In general, shot peening is the most effective and widely used method to improve fatigue performance. Shot peening uses a high-speed moving small steel ball to impact the surface of the material, causing plastic deformation of the surface, and introducing residual compressive stress on the metal surface [1–3]. It is well known that residual compressive stress can improve the fatigue properties of materials [4]. In many cases, it is important to have the exact value of the residual stress. Residual stress can be measured by X-ray diffraction (XRD), neutron diffraction, wafer curvature, drilling, ultrasonic and electromagnetic methods.
Fatigue strength of hot-stamped spot welded joints*—study on spot welding tailored blank technology
Published in Welding International, 2018
Hiroki Fujimoto, Hideki Ueda, Eisuke Nakayama, Rintaro Ueji, Hidetoshi Fujii
Shot blasting during the hot stamping process is intended to remove scale and shot peening is an analogous process by which compressive residual stress is actively removed from metal surface. Shot peening may be used on cogwheels, springs and other mechanical parts and it is thought that cracking from the surface becomes more unlikely and fatigue strength is improved by the compressive residual stress caused by work hardening of metal surfaces [9]. In the case of the spot welded TB joints in this study, fatigue cracks originate at the notch end of the surrounding nugget corona bond and progress in the plate thickness direction towards the shot blasted outer surface. Since fatigue catching does not occur from shot blasted surfaces, the mechanism through which the fatigue life of spot welded TB joints is improved is different from that considered up to now to be involved with shot peening.