THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Additive manufacturing of metallic components – Process, structure and properties

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.

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Metal Additive Manufacturing: A Review

Recent advances in friction-stir welding : Process, weldment structure and properties

Residual stress generated during welding can cause distortion, especially when applied on relatively thin plates. There are several standard and well documented techniques to reduce distortion and residual stress after welding, however these techniques are often costly and time consuming to implement on an industrial scale. In this paper we demonstrate the preand post-weld rolling techniques for reducing weld distortion. PreWeld Rolling (PWR) can be applied before fabrication, potentially by the steel manufacturer. An experimental investigation indicated that there was an average 38% reduction of distortion with this technique. Finite element analysis (FEA) was used to determine the stress distribution to understand the phenomenon. A number of conditions were analysed, including rolling on the top (weld bead side, Figure 1) and bottom (weld root side) surfaces at different distances from the edge where the material was subsequently welded. Both experimental and numerical results have shown that rolling on the bottom side gives better results in terms of distortion reduction. In addition the likely mechanism is the addition of stresses due to rolling which counteract those induced by welding. Some preliminary experimental results on post-weld rolling show that this is a more effective method for reducing distortion, producing virtually flat plates. This significant finding has the potential to eliminate distortion in welded structures where rolling can be applied.

Modelling distortion reduction on pre- and post-weld rolled gas metal arc weldedplates

With a view to raising awareness on the role of additive manufacturing in obsolescence management, this RAND Perspective Paper includes four contributions from experts in different sectors, bringing different analytical approaches to the issue.

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Additive manufacturing and obsolescence management in the defence context

Local rolling and other mechanical tensioning techniques can be highly effective at reducing residual stress and distortion in thin plate welds prone to buckling. However, the issues of high capital cost and low scalability currently prevent wider adoption of such processes. Pre-weld rolling aims to address these issues and can be applied easily to each component prior to fabrication. The results of an initial trial are presented, and indicate that post-weld distortion can be reduced by an average of 38% when correct rolling parameters are used. Finally, the mechanism by which pre-rolling acts to modify the state of residual stress around a weld line is discussed.

/pdf/the-effect-of-pre-weld-rolling-on-distortion-and-residual-gc4m6bitok.pdf

The Effect of Pre-Weld Rolling on Distortion and Residual Stress in Fusion Welded Steel Plate

This work has demonstrated the development and benefits of the Trivex™ tool over the conventional MX-Triflute™ tool in friction stir welding of aluminium alloys. This tool was developed from 2 dimensional models. Experiments made on 7075-T7351 aluminium alloy verified this result. Three dimensional thermal models that used the experimental heat input predicted the weld thermal profile, which correlated well with the experimental curves. The work also demonstrated several novel modelling techniques. The first was the slip boundary condition in 3 dimensions, where a limiting shear stress was applied at the surface and the material was allowed to slip against the tool. The second involved adjusting the limiting shear stress so that the weld power of the model matched that obtained experimentally. The final technique was the inclusion of the temperature profile by interpolating the result from a thermal model. This obviated the need to solve the thermal profile in conjunction with the flow model.

Henry Granjon Prize Competition 2004 Winner, Category A “Joining and fabrication technology”

Wire + arc additive manufacture (WAAM) is an attractive method for manufacturing large-scale aerospace components, however the microstructural changes that occur and the effect of interpass rolling are poorly understood. Therefore two fundamental studies were conducted: the first involved temperature measurement of a wrought dummy wall so that the microstructural changes in the heat affected zone (HAZ) could be related to the thermal cycle. This demonstrated that the white band in the microstructure corresponded to 825 C well below the beta-transus temperature and above this boundary the bi-modal substrate material was converted to lamellar. The second involved peening WAAM material along the side of a deposited wall before applying a typical WAAM thermal heat treatment. This showed that refinement occurred up to the first layer band in the microstructure and the smallest grains were observed just above this boundary at higher temperatures significant grain growth occurred. This study has provided the foundational understanding of microstructural changes that will facilitate future process developments.

Paul A. Colegrove

Papers

Modelling distortion reduction on pre- and post-weld rolled gas metal arc weldedplates

Additive manufacturing and obsolescence management in the defence context

The Effect of Pre-Weld Rolling on Distortion and Residual Stress in Fusion Welded Steel Plate

Henry Granjon Prize Competition 2004 Winner, Category A “Joining and fabrication technology”

The Effect of Thermal History on Microstructural Evolution, Cold-Work Refinement and {\alpha}/\b{eta} Growth in Ti-6Al-4V Wire + Arc AM