Strength and engineering design

We would like to emphasize at this point that strength, fracture toughness, hardness and wear behavior, although important mechanical parameters for materials seleetion and engineering design, are not well-defined material properties, beeause they are intimately... 

Engineering design, then, involves many considerations (Fig. 1.7). The choice of a material must meet certain criteria on bulk and surface properties (strength and corrosion resistance, for example). But it must also be easy to fabricate it must appeal to potential consumers and it must compete economically with other alternative materials. In the next chapter we consider the economic aspects of this choice, returning in later chapters to a discussion of the other properties. 

The first component of the systems approach to error reduction is the optimization of human performance by designing the system to support human strengths and minimize the effects of human limitations. The hiunan factors engineering and ergonomics (HFE/E) approach described in Section 2.7 of Chapter 2 indicates some of the techniques available. Design data from the human factors literature for areas such as equipment, procedures, and the human-machine interface are available to support the designer in the optimization process. In addition the analytical techniques described in Chapter 4 (e.g., task analysis) can be used in the development of the design. 

The principles of strength of materials are applied to the design of structures to assure that the elements of the structures will operate reliably under a known set of loads. Thus the field encompasses both the calculation of the strength and deformation of members and the measurement of the mechanical properties of engineering materials. 

In plastics, these correlative properties, together with those that can be used in design equations, generally are called engineering properties. They encompass a variety of situations over and above the basic static strength and rigidity requirements, such as impact, fatigue, flammability, chemical resistance, and temperature. 

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