Preface

The subject of mechanics of materials is perhaps the most fundamental topic in engineering science. It is among the most widely taught and studied courses for engineers. It has been exhaustively analyzed, picked apart, described, and textualized. There are dozens of texts (with titles like Mechanics of Materials, Strength of Materials, Solid Mechanics, etc.) in use at colleges and universities around the world, some with decades-long histories and more than 10 editions. The logical question at this point may be “Why another?"

The motivation is two-fold. First, higher education in the United States has become prohibitively expensive. As of this publication, many textbooks cost in excess of $300. Some of the most notable contain entire chapters of extra information, hundreds of pages of homework problems, and reams of appendices that the average student will never use. There is certainly value in all of that, and those texts serve as excellent references if students or graduates need an odd, advanced topic, but the vast majority of students who have to buy those books do not recoup the investment. This text is written explicitly to cover a single-semester introductory course. While there are discussions of some advanced materials, it is by no means exhaustive. Relevant material is included, but extraneous “bonus" topics, problems, and references are excluded in the interest of accessibility.

The second, and perhaps more important, reason for writing this book is to overcome what could be seen as shortcomings in most current books. As stated previously, the subject is one of the oldest and most developed in engineering curricula. In the past, it was critical that engineers be able to simplify complex problems into manageable forms, know how to manipulate various equations and models, and identify as many surrogates and simplifications as possible for as wide a variety of situations as possible. In the modern era with the advent of computing technology, previously untenable problems are now solved as a matter of rote. The focus of what engineering students need to learn has shifted; gone is the value of dozens of convenient work-arounds and simplifications, replaced by a pressing need for understanding the basic physics surrounding deformable body mechanics. That is not to say that knowledge of those models is no longer important. Rather, the focus has shifted from how to appropriately use a model to when and why a model might be appropriate.

Each model presented in the text (bars, shafts, beams, plane stress) is derived from first principles. The focus of the derivation is on choice and application of assumptions. Why are certain assumptions made and what is the consequence of their inclusion or exclusion? When is the resulting model valid? Under what circumstances are the solutions of each model a reasonable representation of reality? Students will learn how to use the models for direct calculation, but will also learn when each might be a valid simplification for use in computational solutions such as FEA. Examples throughout the text are solved only after explicitly determining that the problem is appropriate (i.e., satisfies all assumptions and requirements) for the given model.

The text is intended to support a single-semester introductory course. It is organized in exactly the order the author teaches his own class, and almost all material (cover-to-cover) is taught. There are advanced topics, denoted by an asterisk in the section title, which may be considered optional. Each specific topic is treated in such a way as to prepare students for more advanced material; after completing this text, students will be ready for courses in applied mechanics, design, energy methods, elasticity, finite element analysis, or continuum mechanics.