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

Titanium alloys are widely used in the engineering field, namely in the aerospace, automotive and biomedical parts, because of their high specific strength and exceptional corrosion resistance. However, the machinability of titanium alloys is difficult due to their low thermal conductivity and elastic modulus, high hardness at elevated temperature, and high chemical reactivity. This article reviews the state of the art of machinability of titanium alloys, and focuses on the analysis of the process details, namely the especial techniques for cutting improvement, machining forces, chip formation and cutting temperature. The influence of titanium properties on the machinability is also highlighted. Particular attention is given to the turning process of Ti- 6Al-4V alloy. The conclusions presented at the end highlight some current trends, disagreement, and research needs.

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Review on machinability of titanium alloys: the process perspective

In the present study, the temperature distribution on the surface of workpiece and tool during a single discharge in the electrical discharge machining process has been simulated using ABAQUS code finite element software. The temperature dependency of material properties and the expanding of plasma channel radius with time have been employed in the simulation stage. The profile of temperature distribution has been utilized to calculate the dimensions of discharge crater. Based on the results of FEM and the experimental observations, a numerical analysis has been developed assessing the contribution of input-parameters on the efficiency of plasma channel in removing the molten material from molten puddles on the surfaces of workpiece and tool at the end of each discharge. The results show that the increase in the pulse current and pulse on-time have converse effects on the plasma flushing efficiency, as it increases by the prior one and decreases by the latter one. Later, the introduced formulas for plasma flushing efficiency based on regression model were utilized to predict the cardinal parameter of recast layer thickness on the electrodes which demands expensive empirical tests to be obtained.

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Mathematical and numerical modeling of the effect of input-parameters on the flushing efficiency of plasma channel in EDM process

Accurate measurement of residual stress in metallic components using the contour method relies on the achievement of a good quality cut, on the appropriate measurement of the deformed cut surface and on the robust analysis of the measured data. There is currently no published standard or code of practice for the contour method. As a first step towards such a standard, this study draws on research investigations addressing the three main steps in the method: how best to cut the specimens; how to measure the deformation contour of the cut surface; and how to analyse the data. Good practice guidance is provided throughout the text accompanied by more detailed observations and advice tabulated in Appendix.

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Towards good practice guidelines for the contour method of residual stress measurement

This paper presents the results of experimental studies carried out to conduct a comprehensive investigation on the influence of Electrical Discharge Machining (EDM) input parameters on characteristics of EDM process. The studied process characteristics included machining features, embracing material removal rate, tool wear ratio, and arithmetical mean roughness, as well surface integrity characteristics comprising of the thickness of white layer and the depth of heat affected zone of AISI H13 tool steel as workpiece. The experiments performed under the designed full factorial procedure, and the considered EDM input parameters included pulse on-time and pulse current. The results of this study could be utilized in the selection of optimum process parameters to achieve the desired EDM efficiency, surface roughness, and surface integrity when machining AISI H13 tool steel.

Influence of Input Parameters on the Characteristics of the EDM Process

Purpose: The aim of this research is to make a study of the influence of machining parameters on the surface integrity in electrical discharge machining. The material used for this study is the X200Cr15 and 50CrV4 steel for dies and moulds, dies castings, forging dies etc. Design/methodology/approach: The methodology consists of the analysis and determination of the white layer thickness WLT, the material removal rate MRR, the electrode wear ratio EWR and the micro hardness of each pulse discharge energy and parameters of electrical discharge machining. Findings: The Results of the tests undertaken in this study show that increasing energy discharge increase instability and therefore, the quality of the workpiece surface becomes rougher and the white layer thickness increases. This is due to more melting and recasting of material.With the increase of the discharge energy, the amount of particles in the gap becomes too large and can form electrically conducting paths between the tool electrode and the workpiece, causing unwanted discharges, which become electric arcs (arcing). these electric arcs damage the electrodes surfaces (tool and workpiece surfaces) and can occur microcracks. Research limitations/implications: A possible future work would be the development of a general the phenomenal of the residual stress of the wire electrical discharge machining in titanium alloys. The behavior is of the residual stress studies are planed in the future. Practical implications: The relationship found between the total energy of discharge pulses, composition of the steels and the type of machining on the surface integrity (the surface texture, the metallurgical surface aspect, the microhardness in the heat affected zone, HAZ) of different workpiece materials has an important practical implication since it allows selecting the best cutting condition combination from the points of view both the security and the economy for the established requirements in each case. Results are of great importance for aerospace and automotive industry. Originality/value: The paper is original since the bibliographical review has allowed testing that, although works about these themes exist, none approaches the problem like it has been made in this work. The paper could be an interesting source of information for engineers and researchers who work with machining dies and also significant complex parts in aeronautics.

Influence of machining parameters on the surface integrity in electrical discharge machining

Effect of the cutting speed on the chip morphology and the cutting forces

Effect of cutting parameters on chip formation in orthogonal cutting

Purpose: The aim of this work is to provide an in-depth understanding of the surface texture produced by various workpiece inclination angles using high speed finish ball end-milling of the titanium alloy Ti-6Al-4V. Design/methodology/approach: This paper presents an approach to develop a mathematical model of surface roughness in end-milling by the experimental design methodology. Machining variables such as cutting speed, feed and radial depth of cut, which are easily controllable, are considered in building the model. The influence of the workpiece inclination angle on the surface roughness of the machined workpiece was also investigated. Findings: According to the mathematical model, an increase in either the feed or the radial depth of cut increases the surface roughness, whilst an increase in cutting speed decreases it. The radial depth of cut ae is the most significant parameter in the model. Results analysis of the 2D/3D surface roughness parameters of the machined parts shows the improvement of the surface roughness quality when it is machined with a workpiece inclination angle of 25°. Research limitations/implications: As perspectives of this work, we can study the influence of the different machining strategies on the surface integrity of this titanium alloy, including the study of the residual stress. Practical implications: We propose to study the improvement of the surface quality of the orthopedic prostheses, which is an influencing parameter in their lifetime, by implementing the high speed cutting technique. The mathematical model of the surface roughness is a very important result of this work. In fact, it allows selecting the best cutting conditions to obtain a better workpiece surface quality. Originality/value: In this work, three dimensional surface roughness parameters were studied: the 3D surface topographies were obtained using a 3D measurement station and the mathematical model of Sa. The arithmetic mean deviation of the surface was established in order to minimize the experimental works and to have an idea about the surface roughness evolution as a function of cutting parameters.

M. Boujelbene

Papers

Influence of machining parameters on the surface integrity in electrical discharge machining

Effect of the cutting speed on the chip morphology and the cutting forces

Effect of cutting parameters on chip formation in orthogonal cutting

Influence of workpiece inclination angle on the surface roughness in ball end milling of the titanium alloy Ti-6Al-4V

Optimization of the surface roughness in ball end milling of titanium alloy Ti-6Al-4V using the Taguchi Method