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Laser processing in manufacturing
Books and publications before dealing in more detail with specific features. These include armour and the behaviour of fibres under ballistic impact, reinforced rubber products belts, hoses and tyres and ropes and cables. The author adds the caveat that much remains to be learnt about the long-term behaviour of fibres in the latter uses. Kevlar pulp is emerging as an asbestos substitute in many uses and this is also described. The final chapter is a comparison of high-performance fibres, including polyesters, pobethylene, carbon and inorganic, with a special emphasis on the organic products. This is a well-produced, timely, book which covers the Kevlar fibre story in considerable detail, bringing together in the process a Io'. of useful information. Certainly a book for the composites library, it will be of interest to individual workers using organic and other fibres.
N. I. Haneox
Laser Processing in Manufacturing
R.C. Craler and P.J. Oakley (Eds; Chapman & Hall, 1902. ISBN 0-41241520-8, £5O This is a readable textbook at a reasonable price of £:50 from which anyone interested in laser processing could learn much. The reason is partly that the chapters are written by well-known people with considerable experience in their aspects of the subject and partly that the editors have contributed excellent continuity chapters. Thus the book starts with an introductioll to lasers by Roger Cral'er in which we are shown how populations become inverted, why slow-flow lasers can only produce 66 W/m of discharge length and yet fast axial flow lasers can get 4. "7 kW,'m~,'s. This chapter is followed by one on the background to laser processing by both the editors describing the physics of what will follow in the later chaptcrs. This includes transmission of the beam. beam monitoring, interaction with the workpiece and an outline of the various processes together with a dicussion of the heat flow involved. This part briefly carries on by describing radiation absorption, starting with the Maxwell equations. It may sound to some that this is the big switchoff but this should not be so since their style is readable and ~,he result is sufficient physics background that a connection can be made between the extensive literature describing processes and that on the physics of electromagnetic radiation. This surely is the essence of a useful textbook.
There is a whole chapter on beam transmission systems by D. Greening of V & S Scientific. In this chapter the Q factor and focusability of a laser beam in spite of mode and aberrations is discussed together with the design of a number of common optical elements such as beam expanders, polarizers and two-element lenses. There are some useful appendices to this chapter illustrating lens calculations, including the rupture strength of lenses working under high pressure. By Chapter 4 the book has settled into a systematic discussion of processes, starting with those for N d - Y A G lasers by Tim Weedon of Lumonics, in which there are some interesting examples of the current applications of Nd YAG lasers. Each example is discussed with adequate references so that if anyone wished, they could follow up the example in detail. A. May of Laser Lines has the next chapter on Nd.YAG CW and pulsed applications. After describing briefly how the laser can be pulsed, he also lists a number of applications from resistor trimming, through marking to laser soldering. Thus there is no overlap with the welding and cutting examples of Weedon in the previous chapter. The next two chapters are on CO~ laser processes and the final two chapters are on excimer laser processes. For CO: lasers the wicket is held by Martin Adams, the designer of the original Electrox F A F CO._ laser. Thus his remarks on the design of CO: lasers command respect and are very interesting. He points out the differences between RF and d.c. excitation and the differences possible with pulsing using the two power supplies. There are many other well-argued points concerning the design of CO, lasers. The second chapter on CO2 lasers is by Chris Williams of Laser Ecosse, in which he briefly describes the major processes of welding, cutting, surface treatment as well as the design of laser systems with many illustrations. Chapter 8 and 9 are dedicated to excimer lasers, both written by M. Gower of Exitec Ltd. In Chapter 8 he describes how an excimer laser works, its construction, methods of beam delivery with fibres or optics, pulse extenders and beam homogenizers. This is a new area for many in laser processing. His second chapter on excimers describes, with excellent pictures, the numerous applications for excimers which are being considered by industry. This chapter, Chapter 9, is by far the longest in the book, being 91 pages long, but most of this is taken up with pictures of machined hair, micromachined polycarbonate, etching cones caused by dust, stripped 8 /.ma diameter silica fibre, and machined eyeballs! The chapter finishes with most useful tables of threshold fluences and volumetric and linear cutting rates for different materials, and
another table lists many current applications under consideration. The book finishes with Chapter 10 by Peter Oakley, one of the editors, on some of the practical aspects of laser processing in which he draws much of the book together. 1 felt that the book covers the processing by lasers in manufacturing as the authors had set out to do. However, it could usefully have included something on automation, safety (there is a little in Chapter 4 by Weedon) and the growing number of applications in surface treatment. On the other hand, it is particularly strong in the area of excimer applications. One may wonder how such a team got together to write a book in which there is so little overlap of material and which does not read like conference proceedings. The answer is that this book is the result of a successful MSc course in laser material processing which has been running for many years at Essex University. It was felt that the course notes could be usefully brought together as a book for students, and, as I recommend here, for anyone else wishing to learn about laser processing. A final thought is that perhaps the book may inspire some to attend the Essex course, which lasts for one week in the spring of each year.
W. M. Steen
Mechanical Engineerhzg Department { '~niversity of Liverpool
Proceedings of the Sixth Japan-US Conference on Composite materials, 22-24 June 1992
Technomic Publishing Company, ISBN 1-56676-021-6 (no price imticated; The proceedings, of nearly 900 pages, contain 96 papers. Specific sections or sessions cover stress analysis, test methods, interfaces, material systems, smart structures, ceramic and metal matrix composites, durability, micromechanics, structural analysis, strength analysis and databases. This note reflects the interests of the reviewer and is in no way a comment on the value of the papers or topics not mentioned. Despite three decades of high-performance composites, testing is still a contentious issue. Hahn and Reifsnider compare the end-loaded, side-supported, compression test with the IITRI (Illinois Institute of Technology Research Institute) method for tabbed and untabbed, and non-bonded, end-tabbed, unidirectional carbon fibre bismaleimide specimens. The authors conclude that their
Materials & Design Volume 14 Number 5 1993
313
N. I. Haneox
Laser Processing in Manufacturing
R.C. Craler and P.J. Oakley (Eds; Chapman & Hall, 1902. ISBN 0-41241520-8, £5O This is a readable textbook at a reasonable price of £:50 from which anyone interested in laser processing could learn much. The reason is partly that the chapters are written by well-known people with considerable experience in their aspects of the subject and partly that the editors have contributed excellent continuity chapters. Thus the book starts with an introductioll to lasers by Roger Cral'er in which we are shown how populations become inverted, why slow-flow lasers can only produce 66 W/m of discharge length and yet fast axial flow lasers can get 4. "7 kW,'m~,'s. This chapter is followed by one on the background to laser processing by both the editors describing the physics of what will follow in the later chaptcrs. This includes transmission of the beam. beam monitoring, interaction with the workpiece and an outline of the various processes together with a dicussion of the heat flow involved. This part briefly carries on by describing radiation absorption, starting with the Maxwell equations. It may sound to some that this is the big switchoff but this should not be so since their style is readable and ~,he result is sufficient physics background that a connection can be made between the extensive literature describing processes and that on the physics of electromagnetic radiation. This surely is the essence of a useful textbook.
There is a whole chapter on beam transmission systems by D. Greening of V & S Scientific. In this chapter the Q factor and focusability of a laser beam in spite of mode and aberrations is discussed together with the design of a number of common optical elements such as beam expanders, polarizers and two-element lenses. There are some useful appendices to this chapter illustrating lens calculations, including the rupture strength of lenses working under high pressure. By Chapter 4 the book has settled into a systematic discussion of processes, starting with those for N d - Y A G lasers by Tim Weedon of Lumonics, in which there are some interesting examples of the current applications of Nd YAG lasers. Each example is discussed with adequate references so that if anyone wished, they could follow up the example in detail. A. May of Laser Lines has the next chapter on Nd.YAG CW and pulsed applications. After describing briefly how the laser can be pulsed, he also lists a number of applications from resistor trimming, through marking to laser soldering. Thus there is no overlap with the welding and cutting examples of Weedon in the previous chapter. The next two chapters are on CO~ laser processes and the final two chapters are on excimer laser processes. For CO: lasers the wicket is held by Martin Adams, the designer of the original Electrox F A F CO._ laser. Thus his remarks on the design of CO: lasers command respect and are very interesting. He points out the differences between RF and d.c. excitation and the differences possible with pulsing using the two power supplies. There are many other well-argued points concerning the design of CO, lasers. The second chapter on CO2 lasers is by Chris Williams of Laser Ecosse, in which he briefly describes the major processes of welding, cutting, surface treatment as well as the design of laser systems with many illustrations. Chapter 8 and 9 are dedicated to excimer lasers, both written by M. Gower of Exitec Ltd. In Chapter 8 he describes how an excimer laser works, its construction, methods of beam delivery with fibres or optics, pulse extenders and beam homogenizers. This is a new area for many in laser processing. His second chapter on excimers describes, with excellent pictures, the numerous applications for excimers which are being considered by industry. This chapter, Chapter 9, is by far the longest in the book, being 91 pages long, but most of this is taken up with pictures of machined hair, micromachined polycarbonate, etching cones caused by dust, stripped 8 /.ma diameter silica fibre, and machined eyeballs! The chapter finishes with most useful tables of threshold fluences and volumetric and linear cutting rates for different materials, and
another table lists many current applications under consideration. The book finishes with Chapter 10 by Peter Oakley, one of the editors, on some of the practical aspects of laser processing in which he draws much of the book together. 1 felt that the book covers the processing by lasers in manufacturing as the authors had set out to do. However, it could usefully have included something on automation, safety (there is a little in Chapter 4 by Weedon) and the growing number of applications in surface treatment. On the other hand, it is particularly strong in the area of excimer applications. One may wonder how such a team got together to write a book in which there is so little overlap of material and which does not read like conference proceedings. The answer is that this book is the result of a successful MSc course in laser material processing which has been running for many years at Essex University. It was felt that the course notes could be usefully brought together as a book for students, and, as I recommend here, for anyone else wishing to learn about laser processing. A final thought is that perhaps the book may inspire some to attend the Essex course, which lasts for one week in the spring of each year.
W. M. Steen
Mechanical Engineerhzg Department { '~niversity of Liverpool
Proceedings of the Sixth Japan-US Conference on Composite materials, 22-24 June 1992
Technomic Publishing Company, ISBN 1-56676-021-6 (no price imticated; The proceedings, of nearly 900 pages, contain 96 papers. Specific sections or sessions cover stress analysis, test methods, interfaces, material systems, smart structures, ceramic and metal matrix composites, durability, micromechanics, structural analysis, strength analysis and databases. This note reflects the interests of the reviewer and is in no way a comment on the value of the papers or topics not mentioned. Despite three decades of high-performance composites, testing is still a contentious issue. Hahn and Reifsnider compare the end-loaded, side-supported, compression test with the IITRI (Illinois Institute of Technology Research Institute) method for tabbed and untabbed, and non-bonded, end-tabbed, unidirectional carbon fibre bismaleimide specimens. The authors conclude that their
Materials & Design Volume 14 Number 5 1993
313