Engineering for Industrial Designers and Inventors

Chapter 4. Materials

One of the most dynamic areas of development related to design is in material science. Design is visually enhanced by material selection. The allure of gold seems to be driven into our DNA while the textured grit of iron seems to suggest permanence. We love the changing patina of copper, the warmth of brass, the shine of aluminum and silver, the technical appeal of carbon fiber, the understated strength of titanium, and the invitation to touch by leather, wood, and texturized plastic.

Even though this is not a material science book, we have to give materials some mention because materials can save the day for a design in unexpected ways. I have had designs saved by such things as beryllium copper that will never spark, polyethylene that could be purchased in extremely long lengths, fluorinated greases that will not dissolve in fuel, and exotic coatings that provided high temperature service and wear resistance.

We have already considered material strength and stiffness, which include yield and ultimate strength as well as its response to stress (modulus of elasticity). However, there are many other important material attributes. For example, a material’s hardness is a characteristic that has practical importance in determining a part’s strength and wear characteristics. Hardness is defined as the resistance to penetration and is directly related to material strength. Metal hardness is usually changed by various heat-treating processes that modify the grain ...