Engineering Design: A Project-Based Introduction, Fourth Edition

CHAPTER 6

PROBLEM DEFINITION: ESTABLISHING FUNCTIONS

How do I express a design's functions in engineering terms?

WE NOW finish defining the client's design problem and move into engineering practice by (1) establishing the functions that the design must perform, and (2) writing specifications that express those functions in quantitative, engineering terms that enable us to ensure that those functions are performed. Since specifications detail or specify how the performance of those functions can be assessed, they have much in common with the metrics we use to assess the achievement of objectives, and very similar approaches can be taken to writing requirements for a design's features and behaviors.

6.1 ESTABLISHING FUNCTIONS

Asked what a bookcase does, a child might answer, “It doesn't do anything, it just sits there.” An engineer, however, would say that the bookcase does at least two things: It resists the force of gravity exactly to support the weight of the books, and it enables the organization of those books with dividers or by its shelf lengths. Thus, this bookcase doesn't “just sit there.” Understanding functionality is essential to successful design. There are consequences, often tragic, for failing to understand and design for all of a design's functions: recall the Hyatt Regency failure we discussed in Chapter 1. We will now explore how we talk about what designs ...