Preface

Science-led or Design-led? Two approaches to materials teaching

The traditional approach to materials teaching starts with fundamentals: the electron, the atom, atomic bonding, and packing, crystallography, and crystal defects. Onto this is built alloy theory, the kinetics of phase transformations and the development of the microstructure on scales made visible by electron and optical microscopes. This sets the stage for the understanding and control of properties at the millimetre or centimetre scale at which they are usually measured. This science-led approach is grounded in a deep physical understanding of the origins of material properties but gives less emphasis to the behavior of structures and components in service, or methods for material selection and design (the schematic below, reading from left to right).

Science-led and Design-led approaches to materials teaching, and the length scales involved.

The alternative approach is design-led (the schematic, reading from right to left). The starting point comprises the requirements that materials must meet if they are to perform well in a given design. To match material to design requires a perspective on the range of properties they offer, how these properties combine to limit performance, the influences of manufacturing processes on properties, and the environmental impact over the product life-cycle—all coupled to the need to access data and expertise to evaluate them. Once the importance of each property is established, there is a clear platform and motivation from which to “drill down,” so to speak, to examine the science that lies beneath it—valuable because an understanding of the fundamentals itself informs material choice, processing, and usage.

Each approach has its place. The best choice depends on the nature of the course and the aspirations of the student. If the intent is to educate future scientific researchers, the first is the logical way to go. If it is any branch of engineering, design, or applied industrial research, the second makes better sense. This book follows the second, design-led, approach, while providing a balanced treatment of the fundamentals.

What is different about this book?

There are many books about the science of engineering materials; many more about design. What is different about this one?

First, its design-led approach, specifically developed to guide material selection and understanding for a wide spectrum of engineering courses. The approach is systematic, leading from design requirements to a prescription for optimized material choice, illustrated by numerous case studies. Practice in the approach is provided by worked Examples in the text and Exercises at the end of each Chapter.

Second, its emphasis on visual communication through a unique graphical presentation of material properties as material property charts and numerous schematics. These are a central feature of the approach, helpful in utilizing visual memory as a learning tool, understanding the origins of properties, their manipulation, and their fundamental limits, and providing a tool for selection and for understanding the ways in which materials are used.

Third, its inclusivity and breadth. Equal weight is given to all classes of material: metals, polymers, ceramics, and what we call “hybrids”—composites, foams, and most natural materials. The aim here is to present the properties of materials, their origins, and the way they enter engineering and design. A glance at the Contents pages will show sections dealing with:

1. • physical, mechanical and thermal properties, and selection methods to deal with them
2. • friction, wear, durability and corrosion
3. • electrical, magnetic and optical materials, as well as design with the “functional” properties they offer
4. • manufacturing processes, and associated selection methods in design
5. • materials processing, and the way it influences properties
6. • eco-design and the broader issues of sustainable technology

Throughout we aim for a simple, straightforward presentation, developing the materials science as far as is helpful in guiding engineering and design, avoiding detail where it does not contribute to this end.

The fourth feature is that of guided self-learning. Certain topics lend themselves to self-instruction with embedded exercises to build systematic understanding. It works particularly well for topics that involve a contained set of concepts and tools. Crystallography, as an example, involves ideas of three-dimensional geometry that are most easily grasped by drawing and problem-solving. And understanding phase diagrams and phase transformations relies on interpreting graphical displays of compositional and thermodynamic information. Their use to understand and predict microstructure follows procedures that are best learned by application. Both topics have been packaged into self-contained Guided Learning Units, with each new concept presented and immediately practiced using exercises, thereby building confidence. Students who have worked through a package can feel that they have mastered the topic and know how to apply the ideas it contains. Both topics appear briefly in the main text to give a preliminary overview. The full Guided Learning Units follow later in the book, providing for those courses that require a deeper understanding.

The design-led approach is developed to a higher level in five further textbooks, the first relating to Mechanical Design,¹

What's new in the fourth edition

Several main features are new to the fourth edition of this book:

1. • The text and figures have been revised and updated throughout, with particular additions in the following topic areas:
2. 1. • the distinction between bonding-sensitive and microstructure-sensitive properties, leading to a discussion of the nature of atomic and molecular bonding;
   2. • strengthening mechanisms, expanded to include grain-size strengthening;
   3. • functional properties, including dielectric, ferro, piezo, thermo- and pyro-electric behaviour, ferro- and ferri-magnetic, magneto-strictive and magneto-caloric responses, and optical attributes, with examples of their selection and use in design;
   4. • selection of manufacturing process, introducing a structured approach to managing the knowledge-base of expertise that links materials, processes, and design;
   5. • additive manufacture, a review of emerging methods, set within the same framework used to assess established processes;
   6. • materials and the environment, the coverage of which has been fully updated, with a section on sustainability and sustainable technology offering a new perspective.
3. • The number of worked examples in the text has been increased to provide broader illustration of key concepts and equations.
4. • The end-of-chapter exercises have been edited and their number expanded to more than 460, with a fully updated solution manual available to instructors.

This book and the CES EduPack materials and process information software

Engineering design today takes place in a computer-based environment. Stress analysis (finite element method, or FEM, codes for instance), computer-aided design (CAD), design for manufacture (DFM), and product data management tools are part of an engineering education. The CES materials and process information software⁶ for education (the CES EduPack) provides a computer-based environment for optimized materials selection and design, eco-auditing, and introducing processing, including the underlying materials science.

This book is self-contained and does not depend on the CES EduPack for its use. But at the same time, it is designed to interface with the CES software, which implements the methods developed in it, should the instructor and student wish to do so. This enables realistic design problems and selection studies to be addressed, properly managing the multiple constraints on material and processes attributes, particularly in project work. The methodology also provides the user with novel ways to explore how properties are manipulated. And with sustainability now a core topic in most materials-related teaching in engineering and design, the book and the software introduce students to the ideas of life-cycle assessment. Using the CES EduPack enhances the learning experience and provides a solid grounding in many of the domains of expertise specified by the various professional engineering accreditation bodies (analysis of components, problem-solving, design and manufacture, economic, societal, and environmental impact, and so on). In addition, the CES Elements database documents the fundamental physical, crystallographic, mechanical, thermal, electrical, magnetic, and optical properties of all 112 stable elements of the periodic table, allowing the origins and inter-relationships among properties to be explored. In a change from previous editions of this book, an extensive set of CES-based exercises for each chapter are now accessible online, again with a fully worked solution manual available for instructors (further details in the section: Resources that accompany this book).

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¹  Ashby, M. F. (2017), Materials selection in mechanical design, 5th edition, Butterworth Heinemann, Oxford, UK. ISBN 9780081005996. (An advanced text developing material selection methods in detail.)

²  Ashby, M.F. (2012), Materials and the Environment – eco-informed material choice, 2nd edition, Butterworth Heinemann, Oxford, UK. ISBN 978-0-12-385971-6. (A teaching text introducing students to the concepts and underlying facts about concerns for the environment and the ways in which materials and products based on them can both help and harm it.)

³  Ashby, M.F., Ferrer-Balas, D., and Segalas Coral, J. (2016), Materials and Sustainable Development, Butterworth-Heinemann, Oxford, UK. ISBN 978-0-08-100176-9. (A text presenting a methodology for assessing whether a material, product or even a whole technology can be regarded as sustainable.)

⁴  Ashby, M.F., and Johnson, K. (2013), Materials and design, the art and science of material selection in product design, 3rd edition, Butterworth Heinemann, Oxford, UK. ISBN 978-0-08-098205-2. (A text that complements those above, dealing with the aesthetics, perceptions, and associations of materials and their importance in product design.)

⁵  Tempelman, E., Shercliff, H.R., and Ninaber van Eyben, B. (2014), Manufacturing and design – understanding the principles of how things are made, Butterworth Heinemann, Oxford, UK. ISBN 978-0-08-099922-7. (The source of the manufacturing triangle and the structured approach to process-material-design interactions.)

⁶  The CES EduPack, Granta Design Ltd., Rustat House, 62 Clifton Court, Cambridge CB1 7EG, UK. www.grantadesign.com/education.