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This study aims to investigate the effect of mechanical peening on the cooling rate of a subsequently deposited layer in a hybrid additive manufacturing (AM) process.

In this experimental study, 20 layers of 316 L stainless steel are built via directed energy deposition, with the tenth layer being subject to various peening processes (shot peening, hammer peening and laser shock peening). The microstructure of the eleventh layer of all the samples is then characterized to estimate the cooling rate.

The measurements indicate that the application of interlayer peening causes a reduction in primary cellular arm spacing and an increase in micro segregation as compared to a sample prepared without interlayer peening. Both factors indicate an increase in the cooling rate brought about by the interlayer peening.

This work provides insight into process design for hybrid AM processes as cooling rates are known to influence mechanical properties in laser-based AM.

To the best of the authors’ knowledge, this work is the first of its kind to evaluate the effects of interlayer peening on a subsequently deposited layer in a hybrid AM process.

Discusses the use of a corporate Internet in a geographically‐spread consulting firm, James Martin & Co., to share ideas, vision, client information and results. Illustrates with examples. Applications include a quarterly Employee Attitude Survey and regular discussion forums. Proposes that a well‐designed corporate intranet is a highly effective method of making intangible vision and mission pledges more tangible.

Controlled shot peening is widely accepted in the aerospace industry for fatigue life enhancement of critical aeroengine and airframe components. Less well known and little understood by many production engineers is the associated process of “peen forming”. This uses the basic principle of shot peening to form or shape curved sheet metal geometries which would be difficult to create with conventional methods such as die bending, stretch‐forming or rolling. It is particularly cost effective where the number of components involved is too small to justify expensive mass production processes.

The purpose of this paper is to investigate the fatigue and failure of commercial vehicle serial stress-peened leaf springs, emphasizing the technological impact of the material, the thermal treatment and the stress-peening process on the microstructure, the mechanical properties and the fatigue life. Theoretical fatigue analysis determines the influence of each individual technological parameter. Design engineers can assess the effectiveness of each manufacturing process step qualitatively and quantitatively, and derive conclusions regarding its improvement in terms of mechanical properties and fatigue life.

Two different batches of 51CrV4 were examined to account for potential batch influences. Both specimen batches were subjected to the same heat treatment and stress-peening process. Investigations of their microstructure, hardness and residual stress state on the surface’ areas show the effect of the manufacturing process on the mechanical properties. Wöhler curves have been experimentally determined for the design of high-performance leaf springs. Theoretical fatigue analyses reveal the influence of every above mentioned technological factor on the fatigue life of the specimens. Therewith, the effectiveness and potential for further improvement of the manufacturing process steps are assessed.

Microstructural analysis and hardness measurements quantify the decarburization and the degradation of the specimens’ surface properties. The stress-peening process causes significant compressive residual stresses which improve the fatigue life. On the other hand, it also leads to pronounced surface roughness, which reduces the fatigue life. The theoretical fatigue life analysis assesses the mutual effect of these two parameters. Both parameters cancel each other out in regards to the final effect on fatigue life. The sensitivity of the material and the potential for further improvement of both heat treatment and stress peening is appointed.

All quantitative values given here are strictly valid for the present leaf spring batches and should not be widely applied. The results of the present study indicate the sensitivity of high-strength spring steel used here to the various technological factors resulting from the heat treatment and the stress-peening process. In addition, it can be concluded that further research is necessary to improve the two processes (heat treatment process and the stress peening) under serial production conditions.

The microstructure investigations in conjunction with the hardness measurements reveal the significant decrease of the mechanical properties of the highly stressed (failure-critical) tensile surface. Therewith, the potential for improvement of the heat treatment process, e.g. in more neutral and controlled atmosphere, can be derived. In addition, significant potential for improvement of the serially applied stress-peening process is revealed.

The paper shows a systematic procedure to assess every individual manufacturing factor affecting the microstructure, the surface properties and finally, the fatigue life of leaf springs. An essential result is the quantification of the surface decarburization and its influence on the mechanical properties. The methodology proposed and applied within the theoretical fatigue life analysis to quantify the effect of technological factors on the fatigue life of leaf springs can be extended to any engineering component made of high-strength steel.

Because of the unrealistic demand of computer resources in terms of memory and CPU times for the direct numerical simulation of practical peen forming processes, a two‐stage combined finite/discrete element and explicit/implicit solution strategy is proposed in this paper. The procedure involves, at the first stage, the identification of the residual stress/strain profile under particular peening conditions by employing the combined finite/discrete approach on a small scale sample problem, and then at the second stage, the application of this profile to the entire workpiece to obtain the final deformation and stress distribution using an implicit static analysis. The motivation behind the simulation strategy and the relevant computational and implementation issues are discussed. The numerical example demonstrates the ability of the proposed scheme to simulate a peen forming process.

The purpose of this paper is to present an analytical framework for predicting the residual stresses that result from the laser shock peening of a friction stir‐welded 2195 aluminum alloy sample, using the finite element software LS‐DYNA.

The pressures resulting from the laser peening are directly applied in an explicit transient analysis as forces. At the completion of the transient analysis, an implicit springback analysis is performed to determine the final residual stresses. This cycle is repeated for the appropriate number of peen applications, including the appropriate overlap of application areas. To validate the analytical framework, a comparison of residual stresses between analysis and a test specimen is made using laser‐peened base material which was not friction stir‐welded. Friction stir welding (FSW) causes residual stresses and material property variations. In this work, the varying material properties regions are simplified and defined as discrete, separate materials. The residual stresses resulting from the welding are introduced directly as initial conditions in the peening transient analysis and so are combined within the analysis with the residual stresses from the peening.

Comparisons made between the experimental and analytical residual stresses are generally favorable.

Analysis of the laser shock peening of FSW has not been accomplished previously.

The purpose of this paper is to investigate the effect of peening on the fatigue limit of steels for welded structure with a crack in the weld toe zone.

An artificial semi-circular slit was created in the weld toe, and peening was conducted. Then, bending fatigue tests were carried out.

First, owing to the shot peening, the maximum slit depths that can be rendered harmless were 1.0 and 1.2 mm in SUS316 and SM490, respectively. Second, during the fatigue test, the fracture of a peened specimen originated outside the slit, which indicated that peening eliminated the effect of the slit on the fatigue limit. Third, the fatigue limit of a slit specimen was improved by the enhanced residual stress distribution and the decreased stress concentration due to plastic deformation at the weld toe.

There are very few studies about which a fatigue crack is rendered harmless by residual compressive stress, as a result the structures could be continued to use. Moreover, the study defining the concept about rendering crack harmless and systematic investigation was not able to be found.

A FIVE‐AXIS contouring‐type numerically‐controlled shot peening machine has solved the problem of strengthening certain critical structural components of the General Dynamics F.111 variable sweep wing tactical fighter/bomber which is being built at Fort Worth for the United States Navy, the United States Air Force, the Royal Australian Air Force and, possibly, for service with the Royal Air Force. Apart from the vital wing support assembly which must carry the entire weight of the aircraft during flight, over thirty other F.111 components are automatically shot peened with absolute uniformity in this tape‐controlled machine to give the necessary fatigue strength—among the components being 25 ft. long milled wing skins.

The aim of this paper is to give a simple and accurate tool for prediction and comparison of residual stresses in laser shock peened and shot peen treated materials.

This work applies finite element code ABAQUS in order to compare the residual stress state and plastic deformation in specimens in aluminium alloy 7050‐T7451, treated with shot peening (SP) and laser shock peening (LSP) processes. Both processes are simulated using the Hugoniot elastic limit (HEL) of the material in question, and the processes are modelled using same input parameters (pressure on the surface of the specimen and the duration of contact between the material and the peening medium).

By using the same approach in both the analyses, a sound comparison of two technologies can be made, by comparing the obtained residual stress profiles. In addition, surface pressure and contact time can be varied easily in a parametric analysis, allowing the calibration of the numerical results.

Owing to simplicity of used numerical models, different process parameters relative to SP process have not been taken in consideration directly, but through their effect on pressure on the surface of the specimen and the duration of contact between the material and the peening medium.

Application of HEL material model, usually applied to LSP problems, to the analysis of SP process gives promising results, in spite of simplicity of used numerical model.

The one‐step precision blasting method of glass bead cleaning, peening and corrosion removal involves impelling micron size spherical glass particles at controlled velocities against a work‐piece. The impact of the glass beads on the surface of the object pulverises and removes all forms of oxidation, corrosion and other foreign matter, including pit corrosion and corrosion in recessed and hidden areas around and under items such as rivets, The removal of all foreign matter down to the base metal is accomplished far more rapidly, hence far more economically, than currently utilised methods. There is no removal of base metal, no dimensional change and no contamination. Peening is achieved in a similar manner, as will be described later.