Materials in design

The starting point is a market need or a new idea; the end point is the full product specification of a product that fills the need or embodies the idea. Figure 2.1: the stages of conceptual, embodiment and detailed designs, explained in a moment. The product itself is called a technical system. A technical system consists of sub-assemblies and components, put together in a way that performs the required task, as in the breakdown of Figure 2.2. It is like describing a cat (the system) as made up of one head, one body, one tail, four legs, etc. (the subassemblies), each composed of components—femurs, claws, fur. This decomposition is a useful way to analyze an existing design, but it is not of much help in the design process itself, that is, in the synthesis of new designs. Better, for this purpose, is one based on the ideas of systems analysis. It thinks of the inputs, flows and outputs of information, energy, and materials, as in Figure 2.3. The design converts the inputs into the outputs. An electric motor converts electrical into mechanical energy; a forging press takes and reshapes material. In this approach, the system is broken down into connected sub-systems each of which performs a specific function, as in Figure 2.3; the resulting arrangement is called the function-structure or function decomposition of the system. The function-structure gives a systematic way of assessing design options. The design proceeds by developing concepts to perform the functions in the function structure