Principals of Applied Engineering

PrinciPles ofApplied Engineeringreid | reePing | stePhan

Chapter 1 engineering as a DisCiplineengineering 1.1 Define engineeringaccreditingABET The field of engineering operates under a slew of misconceptions held by the public. A modern day engineer does not operate trains; the scope of work within engineering hascriteria broadened since the early days of the hostler. Professionals in the field will likely not beconstraints found underneath our cars changing oil. Instead, engineers can be found behind the scenes of technological innovations – from the devices in our pockets capable of connect- ing us with others around the world to the composition of the rubber soles in shoes. We hear the word engineering in advertisements, tossed around as a potential career for those gifted in math and science (though one can have average math skills and still succeed), but what do we mean by engineering? The organization responsible for accrediting (or evaluating) programs in the field, the Accreditation Board for Engineering and Technology (ABET), provides a definition to encompass the primary aspects of what it means to be an engineer. Engineering is defined to be a profession that draws upon knowledge of mathe- matics and science to create ways to economically use available materials and the forces of nature to benefit the human race through the process of design. Scattered through the definition are various key words and phrases which charac- terize the profession: knowledge of mathematics and science, economic use of materi- als and natural forces, benefiting the human race, and finally – design. Now, what do all of these phrases mean and how do they capture what engineering is all about? Knowledge of Mathematics and Science: Engineers are heavily trained to ensure they are proficient in mathematics and science. The typical coursework an undergraduate engineering student will face includes study in the realms of calculus and physics. The mathematical concepts and methods we learn help us solve physical problems. Rising to the call of being an engineer goes beyond mere textbook exercises; instead, it requires us to solve problems on a grander scale. As eloquently stated by Galileo Galilei, “The laws of Nature are written in the language of mathematics.” Considering that our ability to harness the natural forces around us is dependent on being able to use mathematics in a practical sense, we are trained to speak the language fluently. Economic Use of Materials and Natural Forces: Although we can theoretically sketch out plans for an extravagantly costly and wasteful project, engineers must weigh their options and work within specifications, often called criteria. Beyond the requirements set by a customer, societal or political constraints could affect the creation and imple- mentation of the project. Practically, the common limitation that engineers face is the 7

8 Chapter 1 EnginEEring as a DisCiplinEdesign fact that material and energy cannot be created or destroyed; therefore, we need to bedesign process mindful of our consumption of natural resources. Benefiting the Human Race: Through an engineer’s work, he or she is meeting a par- ticular need. Whether the need in question is relieving poverty in a disadvantaged region of the nation or delivering a quality surround-sound experience in a family’s home theater, the process is fundamentally the same. Our modern lives can be attrib- uted to the work of engineers through the centuries. Design Process: Of all the terms in the definition, design lies at the heart of the engi- neering profession. In order to benefit the human race in a tangible way, we need to undergo a process that takes an idea and implements it physically. The process in ques- tion is called the design process, an iterative series of steps engineers use to arrive at the solution to a problem. Throughout this text, we will delve into the field of engineering and the manner in which an engineer goes about meeting the technological challenges of this century – design.Stone Age 1.2 The hisTorical DevelopmenT of engineering When did technology actually begin? People often think of our times as technological times and earlier eras as “before technology.” In fact, people have always used technol- ogy. Recall that technology is simply using the knowledge we have to create things that people need. Because our knowledge has grown, technology has grown with it—from the simple spears and grinding stones of our earliest ancestors to the complex machin- ery and systems of today. Much of our history has been defined by the materials that people used in a par- ticular era. They used these materials to make tools that helped them carry out every- day tasks. The names of these materials have given us a way to classify historical periods. Three important periods of early history are the Stone Age, the Bronze Age, and the Iron Age. stone age The Stone Age, the period during which people used stone to make tools, lasted for almost 1 million years—from about 1 million b.c. to about 3000 b.c. (Other common materials used during this time were bones and wood.) During this period, people lived very different lives from ours. Early humans used stone, bone, and wood to make axes, spears, scrapers, and even tools for starting a fire. They used the bow for hunting animals. They made needles from bone and used them to sew clothing from animal skins. During the Stone Age, there were few villages. Most people lived nomadic lives, wandering from place to place. They hunted animals and gathered plants, fruits, seeds, and roots for food. They used fire for cooking meat and for protection from wild ani- mals. When they had used up food sources in an area, they moved to a new location. The pace of technological change was very slow.

1.2 ThE hisToriCal DEvElopmEnT of EnginEEring 9Bronze Age Bronze agealloy During the Bronze Age, which lasted from about 3000 b.c. to about 1200 b.c., people began to craft tools and weapons from bronze rather than from stone. The Bronze Age actually began with the discovery of copper. Copper is a soft metal, so it was not prac- tical for tools. During the Bronze Age, however, people learned that copper ore could be heated using charcoal to yield pure copper. They discovered that by melting other ores with copper, they could produce a stronger metal. Bronze is a mixture of the met- als copper and tin. A mixture of two or more metals is called an alloy. Bronze is lighter than stone, and bronze tools and weapons can be made sharper than those made of stone. Using bronze, early humans created new tools such as knives, hooks, and pins. They could also craft large urns and vessels to hold water and food (Figure 1-1).Iron Age figure 1-1 Because bronze is lighter than stone, it was used tosmelting make urns, pots, and tools. iron age The Iron Age, the era when iron came into common use, followed the Bronze Age at different times around the world. It began around 1200 b.c. in the Middle East and about 450 b.c. in Great Britain. It was shorter than either of the two previous periods, lasting only about 1,000 years. Iron was made from iron ore through a process called smelting, in which the ore was melted to take out the impurities. The early iron-smelting furnace was a clay-lined hole in the ground. Iron ore and charcoal were placed in the hole, and then air was pumped in with a bellows. Air from the bellows made the charcoal burn hot enough to soften the ore into a mass of iron. This mass was hammered into the desired shape while it was still red hot (Figure 1-2).

10 Chapter 1 EnginEEring as a DisCiplinE figure 1-2 Iron-smelting furnaces were used to soften iron core. The blacksmith could then hammer the iron into different shapes. Iron eventually replaced bronze as the primary metal used in toolmaking because it was available in more areas and was cheaper to process. It could also be crafted into sharper, longer-wearing tools, such as chisels and saws. As with bronze, the techniques used to make iron varied in different parts of the world. People experimented with temperatures and with the amounts of the various ores they used. They often devel- oped these early technologies by trial and error, without an understanding of the underlying scientific principles. 1.2.1 Key invenTions of early hisTory During early history, people in different parts of the world used stone, bronze, and iron for many of their needs. Tools gradually became more sophisticated and easier to use. People in colder climates had a greater need for warm clothing and shelter. People who lived far from a river or lake wanted to be able to store water for later use. Over many thousands of years, important inventions were developed to meet these different needs. Although many tools were used in similar ways throughout the world, the inven- tions in a particular area often reflected the specific needs of those people. For exam- ple, when horses were used as a form of transportation, the saddle was then invented so riders could ride more comfortably. agriculture About 10,000 years ago—in 8000 b.c.—the nomadic, hunter-gatherer way of life changed. People learned how to grow their own food. They cultivated different types of grains for food, such as wheat and barley. They became farmers who grew flax, which provided fibers to make linen cloth. They invented the wheel and then vehicles with wheels. They built roads and stone houses. The plow was first developed approximately 4000 b.c. This simple tool (Figure 1-3) allowed farmers to turn over soil for planting more easily. It made farming much more efficient. Soon, strong animals such as oxen were used to pull the plow. Farmers could