2-2.4 Realism of Models
Models* are essential for any engineering analysis, but they are always approximate, e.g., Hooke’s law (stress is promotional to strain) and Ohm’s law (voltage is proportional to current). The more complicated tie situation being modeled, the more approximate the model. All that can be asked of model is that is be adequate for the purposes at hand and that its assumptions and limitations be clearly stated. As new technology is introduced and/or the requirements for the product or process become more strict, models that were adequate can become inadequate.
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|Military Handbook- System Engineer's Design for Discard.pdf||application/pdf||5.91 MB||English||DOWNLOAD!|
Many products have components that are discarded when they cease too function properly. The decision about which components to repair and which to discard depends on economies, on available personnel skill, and on constraints such as those imposed by time, law, ethics and safety, for example.
1. In the early 1900s many people straightened a bent nail rather than discard it because of the cost; currently, however. few people in Ibis country would do that unless finding a new nail would take ma much lime.
2. In earlier decades a contaminated cleaning solution of chlorinated hydrocarbons was discarded; currently, however, the cost to discard it properly is so high that the solution would probably be purified and reused many times. It is easy for engineers, managers, and legislators to view the costs of repairing an item Inn narrowly. This tendency is especially true of people who experienced the depression of the 1930s and the war of the 1940s.