Making cars

Computer modelling has been used extensively in manufacturing industries for many years. One familiar application is in the design of car crash-worthiness. Cars must both protect the occupants from physical intrusions into the passenger compartment, and minimise the deceleration forces that act upon them. The first of these requirements could be achieved easily by making the car body rigid. Unfortunately, the deceleration forces would then be intolerably large, so instead the design aim is to make those parts of the vehicle that are outside the passenger compartment absorb as much of the impact energy as possible, by making them deform in the predefined time-dependent manner that minimizes peak deceleration levels.

In the past when car crashworthiness was designed entirely experimentally, full-sized prototypes were subjected to the crash scenarios required by the relevant authorities. If the performance was unacceptable, the shape deformations of the components making up the prototype were examined. A new prototype was engineered empirically to overcome the identified weaknesses before being built and then destroyed in a subsequent test. These tests would be repeated many times before an appropriate design was found. The cost of the process was enormous.

Nowadays, car manufacturers cannot afford to destroy thousands of prototypes when designing crashworthiness into their vehicles. Instead, they spend most of their time building and analysing models on computers, using a technique known as finite-element analysis (Figure 9.1). Only once a computer model is found to be consistent with statutory requirements do they resort to expensive and time-consuming physical testing. This beneficial relationship between modelling and experimentation is still in its infancy in biological research, thanks partly to the great complexity of biological organs.

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