Papers by Keyword: Shot Peening

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Authors: David Deslaef, Emmanuelle Rouhaud, Shabnam Rasouli-Yazdi
Authors: Choumad Ould, Emmanuelle Rouhaud, Manuel François, Jean Louis Chaboche
Abstract: Experimental analysis can be very costly and time consuming when searching for the optimal process parameters of a new shot-peening configuration (new material, new geometry of the part…). The prediction of compressive residual stresses in shot-peened parts has been an active field of research for the past fifteen years and several finite elements models have been proposed. These models, although they give interesting qualitative results, over-estimate, most of the time, the level of the maximal compressive stresses. A better comprehension of the phenomena and of the influence of the parameters used in the model can only carry a notable improvement to the prediction of the stresses. The fact that the loading path is cyclic and is not radial led us to think that a model including kinematic hardening would be better adapted for the modelling of shot peening. In this article we present the results of a simulation of a double impact for several constitutive laws. We study the effect of the chosen constitutive law on the level of residual stresses and, in particular, we show that kinematic hardening, even identified on the same tensile curve than isotropic hardening, leads to lower stress levels as compared with isotropic hardening. Furthermore, the overall shape of the stress distribution within the depth is significantly different for the two types of hardening behaviour. Further, in order to check the modelisations, local measurements were carried on with X-ray diffraction on a large size impact and correlated with the topography of the impact.
Authors: Hua Wei Rong, Hyung Jim Kim, Won Jo Park
Abstract: At present, welding technology is not only emphasized in the development of manufacturing technology but also application is expanding. In these systems, application of SUS as high-temperature material which is used for special purposes is attempted, and improvement of manufacturing technologies bear watching together with increase of using rate. Specifically, Wings with surface of three-dimensional shape usually applied to Fastener with purpose of lightweight. However, due to development of welding technology, methods of existing assembly tend to be replaced by welding, recently. Specifically, if laser welding techniques is applied, it minimizes heat-affected zone than other welding techniques. However, in the case of these special welding, residual stress is raised, and it fatally affects fatigue life. In order to remove residual stress and delay effect of fatigue life, shot-peening is executed; it executes shot-peening and verifies delayed effects of fatigue life. The intention of this study is to obtain the optimal conditions of shot-peening
Authors: Bok Kyu Lim
Abstract: The light weight components, crucial in automobiles and machinery, is require hight strength. Mach peening process is one of many of techniques utilized for improving fatigue properties. From the results of rotary bending fatigue tests, the fatigue strength increases up to 129% in mach peening specimen compared with un-peening. A layer of highly compressed residual stress is obtained by mach peening. The compressive residual stress, induced by mach peening, seems to be an important factor for increasing the fatigue strength.
Authors: Won Jo Park, Sun Chul Huh, Sung Ho Park
Abstract: Small steel ball is utilized in Shot peening process. Called “shot ball” are shot in high speed on the surface of metal. When the shot ball hit the surface, it makes plastic deformation and bounce off, that increase the fatigue life by compressive residual stress on surface. In this study, the results of observation on the tensile strength, hardness, surface roughness, compressive residual stress and fatigue life of a shot peened Al6061-T651 were obtained. Experimental results show that arc height increase tremendously by shot velocity. Also, it shows that surface roughness, hardness, compressive residual stress and fatigue life increase as shot velocity increase.
Authors: Kook Jin Lee, Jae Heon Lee, Tae Kun Lee, Seong Kyun Cheong
Abstract: In this paper the life extension of automobile drive plates will be investigated. The material of specimen is a high carbon steel treated by shot peening, which is most important in the manufacturing process of drive plates. The optimum shot peening condition was investigated by changing the feeding speed and exposure time. The fatigue crack was observed at the fracturing surface of specimens by using scanning electron microscopy (SEM). The distribution of compressive residual stress induced by shot peening process was investigated by using X-ray diffraction. The number of cycles to failure increases at the beginning of exposure. The life cycle decreases after passing some interval of exposure, which will be called as optimum peening zone. Experimental results show that the residual stress distribution and the number of cycles to failure of a drive plate are greatly affected by peening process.
Authors: Dong Sun Lee, Tae Hyung Kim, Jae Heon Lee, Tae Kun Lee, Seong Kyun Cheong
Abstract: In this paper the fatigue life of spur gear was investigated by changing the shot peening condition. From bending fatigue test depending on various shot peening intensity, fatigue characteristics were investigated. The causes of reduction in fatigue life were analyzed by observing the surface of gear with Scanning Electron Microscope(SEM), and impact of residual stress to fatigue characteristics was identified by measuring compressive residual stress depending peening intensity by depth. The results show that the optimum shot ball velocity is 65 m/s and optimum peening time is 8 minutes. From SEM image, the micro-crack was observed at the surface in case of over peening. This seems to be the factor which reduces fatigue life by decreasing compressive residual stress of surface.
Authors: Andreas Nau, Goetz G. Feldmann, Joao P. Nobre, Wolfgang Zinn, Berthold Scholtes
Abstract: The incremental hole-drilling method is the method of choice to determine residual stress depth distributions with limited costs and minor destruction of the investigated component. With a spatial resolution of commonly two millimeters in diameter and one millimeter in depth especially the effects of frequently used surface treatments like e.g. shot peening or deep rolling can be reliably detected if the in depth residual stress gradients are relatively smooth. Nevertheless up to now the quantitative accuracy of the method is poor for residual stress analyses close to the materials surface up to depths of approximately 0.2 mm and in the case of steep in-depth residual stress gradients or oscillating residual stress depth distributions. In this paper, residual stress depth distributions of a broad range introduced by mechanical surface-treatments in flat specimens were analyzed with the hole-drilling method and compared with the results measured by X-ray diffraction as the reference. It comes out, that arbitrary residual stress depth distributions can be successfully determined with a modified differential evaluation formalism. For this purpose, often neglected well known weak points of the hole-drilling method were considered and improved, e.g. hole geometry, numerical calibration and data conditioning. Especially, the proposed strategy of data conditioning results in an almost user-independent evaluation formalism.
Authors: Ivo Černý
Abstract: The paper contains the main results of an investigation of an effect of shot peening on residual fatigue life of specimens made of an aircraft V-95 Al-alloy (equivalent to 7075 alloy) containing physically short fatigue cracks. In the first part, an adaptation and verification of direct current potential drop method for detection and measurement of short crack growth is described and discussed. The specific properties of the material and quite large dimensions of flat specimens with side necking with a low stress concentration factor had to be considered when the position of electrodes was specified. The specimen type and dimensions were proposed considering the investigation of shot peening effects. Physically short fatigue cracks of the length from 0.2 mm to more than 3 mm, most of them between 0.8 – 1.5 mm, were prepared under high cycle fatigue loading of the constant nominal stress amplitude ±160 MPa. Specimens with existing short fatigue cracks were shot peened using two different groups of parameters. Crack growth characteristics after shot peening were measured and compared with crack growth in specimens without shot peening. Retardation of crack growth was significant particularly for cracks shorter than 2 mm. Results are also discussed form the viewpoint of fracture mechanics approach. For the specific stress amplitude, evaluated results enable to estimate threshold length of defects, which after the application of shot peening will be reliably arrested.
Authors: J.B. Li, X.Y. Gai, D.L. Wang, S.Y. Ma, Vincent Ji
Abstract: The work hardening effect of the shot peening affected layer of hardened and low temperature tempered spring steel was investigated using the method for determining the yield strength of a metallic surface with biaxial residual stress. The results show that for the surface layer of the specimens, the microhardness and half-width values of X-ray diffraction lines is decreased, whereas the yield strength is increased during shot peening. Thus, shot peening leads the surface layer of steel in hard state to work hardening instead of work softening.
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