There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

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

Additive manufacturing (AM), widely known as 3D printing, is a method of manufacturing that forms parts from powder, wire or sheets in a process that proceeds layer by layer. Many techniques (using many different names) have been developed to accomplish this via melting or solid-state joining. In this review, these techniques for producing metal parts are explored, with a focus on the science of metal AM: processing defects, heat transfer, solidification, solid-state precipitation, mechanical properties and post-processing metallurgy. The various metal AM techniques are compared, with analysis of the strengths and limitations of each. Only a few alloys have been developed for commercial production, but recent efforts are presented as a path for the ongoing development of new materials for AM processes.

The metallurgy and processing science of metal additive manufacturing

Magnetic pulse welding (MPW) provides an efficient route to join overlapping metallic tubes by the application of a high magnitude electromagnetic (EM) force. The process is rapidly transient in na...

Magnetic pulse welding of metallic tubes – experimental investigation and numerical modelling

A coupled experimental and theoretical study is reported here on friction hydro-pillar processing of AISI 4140 steel, which is a novel solid-state joining technique to repair and fill crack holes in thick-walled components by an external stud The stud is rotated and forced to fill a crack hole by plastic flow During the process, frictional heating occurs along the interface of the stud and the wall of crack hole leading to thermal softening of the stud that eases its plastic deformation The effect of the stud force, its rotational speed and the total processing time on the rate of heat generation and resulting transient temperature field is therefore examined to correlate the processing variables with the joint structure and properties in a systematic and quantitative manner, which is currently scarce in the published literature The results show that a gentler stud force rate and greater processing time can promote proper filling of the crack hole and facilitate a defect-free joint between the stud and original component

Friction Hydro-Pillar Processing of a High Carbon Steel: Joint Structure and Properties

For successful commercial applications of additive manufacturing, metallic parts need to be defect free, structurally sound and reliable. However, additively manufactured metallic parts are susceptible to distortion, lack of fusion defects and compositional changes. Methods to measure susceptibilities of various alloys to these defects are needed but not currently available. Here we show that the necessary theories can be developed based on a well-tested numerical heat transfer and fluid flow model and decades of research in the field of welding. The proposed theories are validated with experimental results reported in the literature.

Heat and Fluid Flow Modeling to Examine 3D-Printability of Alloys

Probing magnetic pulse welding of aluminium and steel sheets

Gas metal arc (GMA) brazing of thin sheets requires active control of heat input, filler alloy deposition and temperature field on sheet surface. A novel attempt is presented here for a rapid synchronous real-time monitoring of current and voltage transients, filler alloy depositions and temperature field using, respectively, a high-frequency recorder, high-speed videography and two thermal infrared cameras during GMA brazing of galvanized steel sheets. For heat inputs from 100 to 200 J mm−1, the peak temperature varied from 1500 to 1700 K. The high-speed videography showed consistent filler deposition and bead profile. The methodology and results presented here depict a promising resource for real-time monitoring and feedback control of GMA brazing.

Amitava De

Papers

Magnetic pulse welding of metallic tubes – experimental investigation and numerical modelling

Friction Hydro-Pillar Processing of a High Carbon Steel: Joint Structure and Properties

Heat and Fluid Flow Modeling to Examine 3D-Printability of Alloys

Probing magnetic pulse welding of aluminium and steel sheets

Real-time heat input monitoring towards robust GMA brazing