This book is a simplified version of the author's book, An Introduction to Continuum Mechanics with Applications, published by Cambridge University Press (New York, 2008), intended for use as an undergraduate textbook. As most modern technologies are no longer discipline-specific but involve multidisciplinary approaches, undergraduate engineering students should be educated to think and work in such environments. Therefore, it is necessary to introduce the subject of principles of mechanics (i.e., laws of physics applied to science and engineering systems) to undergraduate students so that they have a strong background in the basic principles common to all disciplines and are able to work at the interface of science and engineering disciplines. A first course on principles of mechanics provides an introduction to the basic concepts of stress and strain and conservation principles and prepares engineers and scientists for advanced courses in traditional as well as emerging fields such as biotechnology, nanotechnology, energy systems, and computational mechanics. Undergraduate students with such a background may seek advanced degrees in traditional (e.g., aerospace, civil, electrical or mechanical engineering; physics; applied mathematics) as well as interdisciplinary (e.g., bioengineering, engineering physics, nanoscience and engineering, biomolecular engineering) degree programs.

There are not many books on principles of mechanics that are written that keep the undergraduate engineering or science student in mind.

Deformation and configuration

The present chapter is devoted to the study of geometric changes in a continuous medium that is in static or dynamic equilibrium under the action of some stimuli, such as mechanical, thermal, or other types of forces. The change of geometry or rate of change of geometry of a continuous medium can be used as a measure of so-called strains or strain rates, which are responsible for inducing stresses in the continuum. In the subsequent chapters, we will study stresses and physical principles that govern the mechanical response of a continuous medium. The study of geometric (or rate of geometric) changes in a continuum without regard to the stimuli (forces) causing the changes is known as kinematics.

Consider a continuous body of known geometry, material constitution, and loading in a three-dimensional space; the body may be viewed as a set of particles, each particle representing a large collection of molecules, having a continuous distribution of matter in space and time. Examples of such a body are provided by a diving board, the artery in a human body, a can of soda, and so on. Suppose that the body is subjected to a set of forces that tend to change the shape of the body.

Introduction

The kinematic relations developed in Chapter 3, and the principles of conservation of mass and momenta and thermodynamic principles discussed in Chapter 5, are applicable to any continuum irrespective of its physical constitution. The kinematic variables such as the strains and temperature gradient, and kinetic variables such as the stresses and heat flux were introduced independently of each other. Constitutive equations are those relations that connect the primary field variables (e.g., ρ, T, x, and u or v) to the secondary field variables (e.g., e, q, and σ). In essence, constitutive equations are mathematical models of the behavior of materials that are validated against experimental results. The differences between theoretical predictions and experimental findings are often attributed to inaccurate representation of the constitutive behavior.

A material body is said to be homogeneous if the material properties are the same throughout the body (i.e., independent of position). In a heterogeneous body, the material properties are a function of position. An anisotropic body is one that has different values of a material property in different directions at a point, that is, material properties are direction-dependent.

Introduction

In the beginning of Chapter 3, we briefly discussed the need to study deformation in materials that we may design for engineering applications. All materials have a certain threshold to withstand forces, beyond which they “fail” to perform their intended function. The force per unit area, called stress, is a measure of the capacity of the material to carry loads, and all designs are based on the criterion that the materials used have the capacity to carry the working loads of the system. Thus, it is necessary to determine the state of stress in materials that are used in a system.

In the present chapter, we study the concept of stress and its various measures. For instance, stress can be measured as a force (that occurs inside a deformed body) per unit deformed area or undeformed area. Stress at a point on the surface and at a point inside a three-dimensional continuum are measured using different entities. The stress at a point on the surface is measured in terms of force per unit area and depends on (magnitude and direction) the force vector as well as the plane on which the force is acting.

Introduction

This chapter is dedicated to the application of the conservation principles to the solution of some simple problems of solid mechanics, fluid mechanics, and heat transfer. In the solid mechanics applications, we assume that stresses and strains are small so that linear strain-displacement relations and Hooke's law are valid, and we use appropriate governing equations derived in the previous chapters. In fluid mechanics applications, finding exact solutions of the Navier–Stokes equations is an impossible task. The principal reason is the nonlinearity of the equations, and consequently, the principle of superposition is not valid. We shall find exact solutions for certain flow problems for which the convective terms (i.e., v · ∇v) vanish and problems become linear. Of course, even for linear problems flow geometry must be simple to be able to determine the exact solution. The solution of problems of heat transfer in solid bodies is largely an exercise of solving Poisson's equation in one, two, and three dimensions.

This book is about the design and application of industrial cleanroom robots in electronics manufacturing. It is intended as a hands-on technical reference for engineers and factory managers involved in manufacturing electronic devices in cleanroom environments. The book provides insight into the principles and applications of industrial cleanroom robotics, in particular in semiconductor manufacturing, the most demanding process in terms of cleanliness requirements. Other examples are the hard disk, flat panel display, and solar industries, which also use high levels of cleanroom automation and robotics. In contrast to the complex manufacturing process, the typical robotic designs often utilize relatively simple robot kinematics in the highly structured environments of process and metrology tools. Some industries, for example the semiconductor front-end industry, are governed by technical standards and guidelines, which are generally helpful during the design process of robotic systems. On the other hand, robotic engineers in electronics manufacturing face challenges that are unknown in other markets, most importantly the cleanliness required in certain factories. Strict cleanliness requirements have resulted in two categories of cleanroom robots: ‘atmospheric robots’ for high-quality cleanliness at ambient atmospheric pressure, and ‘vacuum robots’ for extreme cleanliness in enclosures under various vacuum pressures. These two categories are the focus of this book.

Robotics refers to the study and use of robots (Nof, 1999). Likewise, industrial robotics refers to the study and use of robots for manufacturing where industrial robots are essential components in an automated manufacturing environment. Similarly, industrial robotics for electronics manufacturing, in particular semiconductor, hard disk, flat panel display (FPD), and solar manufacturing refers to robot technology used for automating typical cleanroom applications. This chapter reviews the evolution of industrial robots and some common robot types, and builds a foundation for Chapter 2, which introduces cleanroom robotics as an engineering discipline within the broader context of industrial robotics.

History of industrial robotics

Visions and inventions of robots can be traced back to ancient Greece. In about 322 BC the philosopher Aristotle wrote: “If every tool, when ordered, or even of its own accord, could do the work that befits it, then there would be no need either of apprentices for the master workers or of slaves for the lords.” Aristotle seems to hint at the comfort such ‘tools’ could provide to humans. In 1495 Leonardo da Vinci designed a mechanical device that resembled an armored knight, whose internal mechanisms were designed to move the device as if controlled by a real person hidden inside the structure. In medieval times machines like Leonardo's were built for the amusement of affluent audiences. The term ‘robot’ was introduced centuries later by the Czech writer Karel Capek in his play R. U. R. (Rossum's Universal Robots), premiered in Prague in 1921.