Materials technology for technicians 2

Materials technology for technicians 2

edition of "Physics for Engineers" and reads very much like an abbreviated 'O'-level or CSE physics text in both form and content. The author believes...

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edition of "Physics for Engineers" and reads very much like an abbreviated 'O'-level or CSE physics text in both form and content. The author believes that diagrams and illustrations describe engineering and science much more vividly than words and those which he includes to support a wellwritten and accurate text are clear, meaningful and many of them memorable - the "splat" of hydrogen nuclei fusing to form helium nuclei, the cartoon accompanying the caption "damp + electricity = danger" and the drawings illustrating the relative intensities of various sounds, to mention only a few. In addition to a good index, the book contains many questions (with answers) and problems (with answers). It is an excellent student textbook and deserves a wide readership. One might indeed be forgiven for mistaking this for a bestselling 'O'-level/CSE text were it not for the reference to TEC units in the preface and the TEC standard units Physical Science 1 and Engineering Science I set out in detail in the last eight pages. It could, perhaps, be argued that a textbook written specifically for students following TEC programmes should be more closely integrated with the general and specific learning objectives of the standard units. This is what the author has sought to achieve in "Materials Technology for Technicians 2" and "Materials Technology" which are intended to cover TEC level II (U 78/475 and U 80/738) and level IV (U 78/477) units. "Materials Technology for Technicians 2" includes chapters on the structure of metals, carbon steels, cast irons, non-ferrous alloys and polymers. Each chapter is prefaced by a list of objectives and ends with a list of twelve to twenty problems (without answers). The diagrams are clear but there is no index and in places the text needs some modification. For example, the reason given for the high extensibility of elastomers (p. 67) is incorrect whilst the section heading "Metals as Crystalline" (p. 3) and the sentence "another type of polymer is the elastomers" (p. 66) should have been spotted and corrected by the editor. The very high thermal expansivity of plastics compared with metals is worthy of mention in the section on the general properties of plastics since a lack of appreciation of this fact amongst technicians often leads to the

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failure of elevated temperatures of devices made from a combination of plastic and metal at room temperature. The reference to the table on p. 63 should read p. 62. Overall the book covers the two level II units adequately and some students may find it helpful to work from a book which limits itself to the narrow confines of the TEC units. Having said that, it should also be mentioned that the same information in more digestible form is also available in existing ONC/OND textbooks. Another book intended for students taking the TEC U 80/738 unit is "An Introduction to Engineering Materials". Unlike "Materials Technology for Technicians 2", the subject matter is not integrated with learning objectives and this makes it even more like existing ONC/OND textbooks in form, although it is much narrower in content. Following a sketchy but interesting introduction on materials in engineering the topics covered are atomic structure, the mechanical properties of materials, the mechanical testing of metals, the structure of polymers, polymers in practice, the structure of metals, metals for casting, metals for forming, the structure and properties of steels and, finally, the heat treatment of steels and cast irons. Whilst the book is much more readable than Materials Technology for Technicians 2, there are numerous errors, particularly in the chapters relating to non-metallic materials. Thus, for example, the author states (p. 16) that "most non-metals are non-crystalline" and that "in most non-metallic compounds atoms are joined together by covalent bonding" (p. 20). Titanium oxide is not an essential constituent of brick clays (p. 23) nor can its structure be represented in terms of molecular 0-Ti-0) units. The formula for sodium silicate (p. 23) depicting trivalent oxygen and silicon is clearly wrong and the formula for polyethylene is hardly ever written as CnH2n + 2. Ionic bonding is introduced (p. 24) using sodium chloride as an example but no mention is made of its presence in other commercially important inorganic non-metallic materials; in fact, ionic bonding, having been introduced is not referred to again in the text. The chapter on mechanical properties contains one or two half-truths but later chapters are well written and make an interesting read. The book

has a good index and clear diagrams but there are no problems to help the student test his knowledge and the paper cover is unlikely to stand up to as hard wear and tear as will the flexicovers of "Physical Science for Engineers", "Materials Technology for Technicians 2" and "Materials Technology 4". "Materials Technology 4" is a level IV textbook for students who have been awarded the TEC Certificate or are of comparable standard and who are setting out on studies leading to the Higher Certificate/Higher Diploma which include TEC unit U 78/477 in the programme. The overall theme of the units is an introduction to the selection of materials and processes; this is covered in chapters on mechanical properties, fracture, fatigue, creep, environmental stability, the forming of metals and non-metals, the joining of materials, choosing materials and processes and the book ends with a chapter containing source material for eleven well-chosen case studies. As in the level II textbook, each chapter is prefaced by a statement of the learning objectives and terminates with a series of problems (without answers). Most chapters cover the objectives adequately but Griffiths equation (p. 18) should be clearly stated in its more usual form and the primary importance of thermal expansivity should be mentioned in relation to thermal shock (p. 41). Chapter 9 "Choosing a Material" is very sketchy and it is unlikely that the learning objectives can be achieved from the one page of text and the fifteen selection of materials problems (without answers). On the credit side, an attractive feature of this volume is the extracts it contains from the journal "Engineering"; these include "10 ways to help corrosion" (April 1976), "10 ways not to have a component die-cast" (August 1978), "10 ways to take advantage of plastics" (July 1976) and eight other articles which form the source material for the majority of the case studies in Chapter 10. As in the case of the level II textbook "Materials Technology for Technicians 2" there is no index but a short bibliography is included which points the student in the direction of British Standards, the Design Council Engineering Guides and the excellent Open University 3rd level course (T 352)"Materials Processing".

MATERIALS IN ENGINEERING, Vol 3, APRIL 1982