Peening

About: Peening is a research topic. Over the lifetime, 5538 publications have been published within this topic receiving 73073 citations.

Comparison of mechanisms of advanced mechanical surface treatments in nickel-based superalloy

Abstract: Mechanical surface enhancement techniques are used to introduce compressive residual stresses to enhance the fatigue life and corrosion resistance of metallic components. In this study, we compare the effects of three advanced mechanical surface enhancements treatments: laser shock peening, cavitation shotless peening and ultrasonic nano structure modification on residual stress, hardness, plastic deformation and changes in near surface microstructure introduced in a Ni-Base superalloy, IN718 SPF(Super plastic forming). Coupons of the alloy were peened using two different conditions of each treatment and results compared to achieve a better understanding of underlying mechanisms of these techniques. Results indicate that there are significant differences in mechanisms of these surface treatments leading to differences in material response.

Surface modification by machine hammer peening and burnishing

Abstract: A wide range of surface modification processes has been developed over the past decades. Beside the well-established processes such as shot peening, there are other emerging surface modification processes such as machine hammer peening with a potential of applications that still needs to be evaluated. Therefore, all surface modification processes using guided tools with periodic or continuous contact to the workpiece are compared in this paper. After a classification of the processes, the paper presents a systematic description by comparing the different technologies and it explains the proposed standardized nomenclature. It identifies the relevant physical mechanisms of the surface modifications processes and it compares the influences on surface roughness, residual stresses, work hardening and microstructure. One section is dedicated to the need of an accompanying quality assurance. Furthermore, the capabilities of different process simulation approaches are analyzed with respect to process mechanisms and the resulting surface layer characteristics. The service performance such as fatigue life, corrosion resistance, friction and wear are discussed based on best practice results. Finally, the paper discusses the actual and potential applications of surface modification processes: surface strengthening, post welding treatments, smoothing of tools and molds as well as surface structuring and embedding of coating materials.

About the role of residual stresses and surface work hardening on fatigue ΔKth of a nitrided and shot peened low-alloy steel

Abstract: Nitriding and shot peening are surface treatments widely used to improve the fatigue strength of mechanical and structural components. Both treatments enhance the mechanical properties of the surface layer of material: nitriding mainly by means of chemical transformations and formation of a very hard case, shot peening mainly due to compressive residual stress field in the sub-surface layer of material. The combined application of nitriding and shot peening has not been adequately investigated in literature and the known data do not allow to define a general criterion to assess if and when shot peening application after nitriding can be useful. In this paper the effect of nitriding plus shot peening on fatigue strength of a low-alloy steel is investigated by means of experimental tests carried out on specimens containing a micro-hole, acting as a pre-crack. To analyse the role played by shot peening induced residual stresses, a series of specimens was heat-treated after shot peening, being the aim the partial removal of residual stresses without strongly modifying the mechanical properties of the surface layer of material. After a critical discussion of the results in terms of residual stress, micro-hardness trend and fatigue strength, an original fracture mechanics based approach is proposed to predict the threshold value of the stress intensity factor of nitrided and shot peened steels. The results are in good agreement with the experimental evidence.