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Shot peening - Theory and applications

Authors:
  • Electronics Incorporated

Abstract

The papers presented in this volume address a variety of topics that further establish controlled shot peening as an important manufacturing process capable of reproducible results. Topics discussed include shot peening and fatigue, measurement of residual stresses, control of shot peening process, shot peening technology, and applications. Papers are presented on the influence of shot peening on material properties and the controlled shot peening of turbine blades; shot blasting systems; and application of rotary peening in aircraft maintenance.
... It is a cold working process that shoots balls (shot) of steel, ceramics or glass beads at the workpiece (metals in particular) to mechanically prestress the material surface beyond its yielding point. [6][7][8][9] The localized plastic deformation induces residual stresses into the surface region of the material. The surface residual stresses are compressive. ...
... The residual kinetic energy carried by the shot enables it to deflect from the surface of the component. [5][6][7][8][9] The level of plastic deformation is dependent on the hardness and the thickness of the material. Therefore, more shot kinetic energy is required for thicker and harder surfaces. ...
... The denser steel shot has high deformation energy, which would impact the material in comparison with ceramic or glass particles. [5][6][7][8][9] However, for shot peening ceramics, it is necessary to employ a ceramic-based shot material to avoid deformation and enable the shots to be reused with maximum effect. ...
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Laser shock peening and conventional mechanical shot peening are both comparable processes generally applicable to surface treat various metals and alloys. Commercial advantages offered by the laser systems such as flexibility, deep penetration of laser-induced shocks with precise control of the thermal pulses, shorter process times, high speeds, accuracy and aesthetics are attractive in comparison with the mechanical shot peening technique. Laser shock peening in the recent years has proved to be successful with steels, aluminium and titanium surfaces and metallic alloys in general. Nevertheless, minimal research has been conducted on laser shock peening and mechanical shot peening of technical grade ceramics. This article presents an update of the theory and to-date relevant literature within the two subject areas, as well as a comparison and a contrast between the mechanical and laser shock peening techniques. In addition, various gaps in knowledge are identified to propose further research for the development of both the techniques applicable to the surface treatment of technical grade ceramics.
... Shot peening treatment is a widely used surface strengthening technique, which can significantly improve the fatigue failure resistance of structurals. The compressive residual stress is introduced on the surface of the material by the high-speed impact of metal shot particles, which can counteract the tensile stress produced by mechanical cyclic loads and thus significantly improve the fatigue performance of structures [1][2][3][4]. As illustrated in Fig. 1, shot peening treatments result in the change of target's surface morphology, microstructure and distribution of mechanical properties. ...
Article
In this paper, the stress relaxation behavior and fatigue performance of SS304 materials treated with three shot peening intensities (0.1 mmA, 0.25 mmA and 0.4 mmA) were studied and a life prediction model was proposed. The model can describe the stress relaxation process and fatigue failure process of shot peening specimens completely combined with the surface morphology of the specimens treated with different shot peening intensities. The predicted fatigue lives of three kinds of shot peening intensities based on the model was in good agreement with the test lives. Besides, the model can describe the life transition behavior of shot peening specimens under high mechanical stress levels and explained the life transition mechanism combined with the test results.
... Mechanical properties applied to the numerical simulation. SAE J-441 standardizes the ball applied to the shot peening processes [14]. For this research it was designated S-230 that has a radius of 0.3 mm. ...
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This research presents a numerical simulation of the shot peening process and determines the residual stress field induced into a component with a previous loading history. The importance of this analysis is based on the fact that mechanical elements under shot peening are also subjected to manufacturing processes, which convert raw material into finished product. However, material is not provided in a virgin state, it has a previous loading history caused by the manner it is fabricated. This condition could alter some beneficial aspects of the residual stress induced by shot peening and could accelerate the crack nucleation and propagation progression. Studies were performed in beams subjected to strain hardening in tension (5εy) before shot peening was applied. Latter results were then compared in a numerical assessment of an induced residual stress field by shot peening carried out in a component (beam) without any previous loading history. In this paper, it is clearly shown the detrimental or beneficial effect that previous loading history can bring to the mechanical component and how it can be controlled to improve the mechanical behavior of the material.
... This occurs during the impact as a portion of the kinetic energy supplied by the shot impacts the material surface, creating a zone of local plastic deformation. This in turn results in a small increase in the temperature at the point of impact and the residual kinetic energy supplied by the shot allows the material to deflect it from the surface [3][4][5][6][7]. The fired shots at high velocity causes plastic deformation, but this occurs by compression during the impact, whereby, the surface layer stretches and tighten which causes the surface beneath to compress-inducing a compressive zone beneath the impacted area. ...
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This paper presents the micro-shot peening of zirconia (ZrO2)-advanced ceramics applicable for bio-medical, dental, automotive and aerospace sectors. A ZrO2-advanced ceramic was micro-shot blasted with selected parameters as a first-step investigation focused on the topography, microstructure, surface hardness and the surface fracture toughness (K Ic) characteristics. A new technique of micro-blasting was conducted using a portable shot blaster. A white-light interferometer, scanning electron microscopy and Vickers indentation technique were employed for the analysis. This was followed by determining the K Ic using an empirical equation. Surface roughness was improved by 34 % after micro-shot blasting treatment. No surface cracking was present which generally exists due to the brittle nature of the ceramic. The hardness, however, reduced by 5.6 % with a reduction in the Vickers crack length of 9 %. This improved the K Ic by 3 % when comparing the micro-shot peened surface to the original, as-received surface. It is difficult to conclude if the ZrO2-advanced ceramic has undergone plastic deformation and the movement of dislocations increased to strengthen the ZrO2 ceramic at this stage. However, based on the results, it can be predicted that a level of surface compression was induced beneath the micro-shot peened layer as indicated from the result of the surface topography and integrity. This would justify the hardness modification and the enhancement in K Ic.
... On one hand, many surface treatments were studied to address at least one of these problems: nitriding [1,[3][4][5][6][7] and shot peening [8] for thermal fatigue resistance; steel boriding [9][10][11], vanadium carbide diffusion layers [2], thin nitride PVD coatings [12][13][14][15][16][17] and thermallysprayed boride coatings [18,19] mainly for corrosion resistance; oxide [20] or carbide [21] coatings for improved lubrication at high temperatures. ...
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Repeated fast surface temperature transients can damage the materials and/or their surface treatments by thermal fatigue. This happens in aluminium diecasting devices. One conducted thermal fatigue tests with samples of hot work tool steel, respectively untreated, simply borided and protected by a multi-layer. In the last case, top coat is yttria stabilised zirconia (YSZ), followed by a nickel superalloy and then a borided layer (undercoat). The zirconia coating was applied with plasma spray. The multi-layer showed poor resistance during the thermal fatigue tests. Better understanding these tests and the resulting thermal fatigue observed on the treated materials was achieved by a lifetime model based on Coffin–Manson equations.
Article
Peening is a very useful process for extending the service life of a large number of metallic components. To maximize its benefits, an understanding of the principles involved in the process is needed. This report promotes understanding of the most important principles of shot peening. The topics covered are as follows: shot peening basics; types of shot peening media; residual stress distribution; coverage and saturation; shot peening equipment and its control; and new advances in shot peening.
Article
Shot peening is an important surface enhancement process, which helps in assuring satisfactory fatigue life and reliability of the automotive, aerospace and marine components. One of the most important factors affecting shot peening performance is the type of shot peening machine. This paper presents an innovative design of a laboratory-based air blast shot peening machine. This machine has a vertical nozzle suction system to take the advantage of gravity feed as well as the feed created by suction of the pressurized air. Special attention was paid to the design of the nozzle and the mixing chamber so as to obtain adequate suction of shots. The performance of the machine was evaluated by carrying out various shot peening tests on AISI 1045 steel specimens. The tests included microscopic examination of coverage with ×10 magnification lens, fatigue and wear resistance. The wear resistance of the peened AISI 1045 material increased by 3.5 times the unpeened one. The fatigue tests showed improvement in fatigue life of the workpiece up to about four times. Besides, there was an increase in yield and torsional strength of the workpiece by about 1.5 times.
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