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Materials Selection in Mechanical Design

Michael F. Ashby

Chapter 1

Introduction: Materials and Design - all with Video Answers

Educators


Chapter Questions

00:15

Problem 1

Concepts (working principles). Even if you shut the windows and doors dust settles in rooms like gentle snow. The need: a device to remove dust from household floors. Here are three established concepts:
- human-powered bellows pump with cloth filter;
axial-flow electric fan with muslin filter; and
centrifugal fan with centrifugal dust separation and collection.
What other concepts could fill this need? Nothing, at the concept stage, is too far-fetched; decisions about practicality and cost come later.

Dading Chen
Dading Chen
Numerade Educator
01:29

Problem 2

Function structures. Make a function-structure diagram for the Electrolux cleaner of Fig. E1.1.

Rikhil Makwana
Rikhil Makwana
Numerade Educator
03:27

Problem 3

Concepts (working principles) for cooling power electronics. Microchips, particularly those for power electronics, get hot. If they get too hot they cease to function. The need: a scheme for removing heat from power microchips. One such scheme is sketched in Fig. E1.2. Its working principle is that of thermal conduction to fins from which heat is removed by convection. Four working principles are listed as follows: thermal conduction, convection by heat transfer to a fluid medium, evaporation exploiting the latent heat of evaporation of a fluid, and radiation, best achieved with a surface with high emissivity.
The best solutions may be found by combining two or more of these, such as conduction coupled with convection (as in the sketch - an often-used combination). Consider both the case of long term, continuous-operation heat sinks and the case of short-term, intermittent heat sinks (with pause between operations for system to return to ambient temperature). Suggest designs for efficient heat sinks for these two cases.

Sunita  Kumari
Sunita Kumari
Numerade Educator
01:29

Problem 4

Function structures. Make a function-structure diagram for the heat sinks.

Rikhil Makwana
Rikhil Makwana
Numerade Educator
04:21

Problem 5

Attaching paper sheets. The need: documents consisting of several pages can become confused if the pages are loose. Use the internet to explore alternative concepts for attaching a small number of pages together in a way that still allows them to be read. Record, as far as possible, the materials of the attachment and the property that provides the attachment force.

Averell Hause
Averell Hause
Carnegie Mellon University