Solution manual
Materials selection in mechanical design 6th edition
By michael f. Ashby
6th edition
,Hapter 1. Introduction: materials and design
E1.1 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.
Figure e1.1. Vacuum cleaners: a hand-powered cleaner from 1880, the
electrolux cylinder cleaner of 1960 and the dyson centrifugal cleaner of
2010. (early cleaner courtesy worcester news.)
Answer. Here are some concepts for dust collectors. The list starts with the three in the figure to set the
style.
• Entrain dust in airstream created by hand-powered bellows; capture dust from airstream with
filter.
• Entrain dust in airstream created by axial electric fan; capture dust from airstream with filter.
• Entrain dust in airstream created by centrifugal fan; capture dust from airstream with
centrifugal separator.
Now some other possibilities.
• Sweep the floor with a brush; collect dust in dust pan. It has worked for generations and still
does.
• Entrain dust in airstream; remove with electrostatic separator. It works for industrial emissions.
• Entrain dust in airstream; remove with fine water spray to create a liquid slurry. It’s how oxides
of sulphur are removed from power station emissions.
• Entrain dust in airstream; remove by passing airstream across wet fabric. It’s what happens
when you hang clothes out to dry and a wind stirs up the dust.
• Trap dust on adhesive reel-to-reel adhesive tape rolled across the floor. Adhesive tape works
well as a way of trapping mosquitos; why not dust?
• Pay a cleaning agency to come and take the dust out of your house. They have their own
methods.
,E1.2 function structures. Make a function-structure diagram for the electrolux cleaner of figure e1.1.
Answer. The diagram is shown below.
E1.3 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 is sketched in figure e1.2. Its working principle is that of thermal conduction to fins
from which heat is removed by convection.
Figure e1.2. A heat sink
Four working principles are listed below: 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: 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).
Answer. Concepts for continuous or long-term operation.
• Transmission of heat by conduction; removal by natural or fan-assisted convection. (typical
system in personal computer.)
• Transmission of heat by conduction; removal by radiation. (possible system for operation in
space.)
• Transmission of heat by conduction, heat exchanger to pass heat to working fluid; heat removed
from working fluid by convection (a radiator).
• Transmission of heat by conduction; heat exchanger to pass heat to working fluid (water, for
instance) drawn from renewable source (a river, for example); working fluid then rejected.
• Transmission of heat by conduction, active removal by peltier (thermoelectric) cooling.
• Transmission of heat by conduction, active removal by magnetocaloric (mc) cooling.
Concepts for pulsed or short-term operation.
• Conduction of heat into heat sink so massive that the temperature rise is acceptably small.
• Conduction of heat to reserve of phase-change material (paraffins, hydrated salts such as
cacl2.6h2o); heat absorbed by the latent heat of melting.
, • Conduction of heat to sacrificial evaporative coating; heat removed by latent heat of
evaporation.
E1.4 function structures. Make a function-structure diagram for the heat sinks.
Answer. The diagram is shown below.
E1.5 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.
Answer.
Systems that rely on elastic stiffness (thus, elastic modulus) to provide the attachment force.
Wood mild steel spring steel spring steel polypropylene
Systems that rely on strength or plasticity to provide the attachment force.
Mild steel brass brass
Materials selection in mechanical design 6th edition
By michael f. Ashby
6th edition
,Hapter 1. Introduction: materials and design
E1.1 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.
Figure e1.1. Vacuum cleaners: a hand-powered cleaner from 1880, the
electrolux cylinder cleaner of 1960 and the dyson centrifugal cleaner of
2010. (early cleaner courtesy worcester news.)
Answer. Here are some concepts for dust collectors. The list starts with the three in the figure to set the
style.
• Entrain dust in airstream created by hand-powered bellows; capture dust from airstream with
filter.
• Entrain dust in airstream created by axial electric fan; capture dust from airstream with filter.
• Entrain dust in airstream created by centrifugal fan; capture dust from airstream with
centrifugal separator.
Now some other possibilities.
• Sweep the floor with a brush; collect dust in dust pan. It has worked for generations and still
does.
• Entrain dust in airstream; remove with electrostatic separator. It works for industrial emissions.
• Entrain dust in airstream; remove with fine water spray to create a liquid slurry. It’s how oxides
of sulphur are removed from power station emissions.
• Entrain dust in airstream; remove by passing airstream across wet fabric. It’s what happens
when you hang clothes out to dry and a wind stirs up the dust.
• Trap dust on adhesive reel-to-reel adhesive tape rolled across the floor. Adhesive tape works
well as a way of trapping mosquitos; why not dust?
• Pay a cleaning agency to come and take the dust out of your house. They have their own
methods.
,E1.2 function structures. Make a function-structure diagram for the electrolux cleaner of figure e1.1.
Answer. The diagram is shown below.
E1.3 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 is sketched in figure e1.2. Its working principle is that of thermal conduction to fins
from which heat is removed by convection.
Figure e1.2. A heat sink
Four working principles are listed below: 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: 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).
Answer. Concepts for continuous or long-term operation.
• Transmission of heat by conduction; removal by natural or fan-assisted convection. (typical
system in personal computer.)
• Transmission of heat by conduction; removal by radiation. (possible system for operation in
space.)
• Transmission of heat by conduction, heat exchanger to pass heat to working fluid; heat removed
from working fluid by convection (a radiator).
• Transmission of heat by conduction; heat exchanger to pass heat to working fluid (water, for
instance) drawn from renewable source (a river, for example); working fluid then rejected.
• Transmission of heat by conduction, active removal by peltier (thermoelectric) cooling.
• Transmission of heat by conduction, active removal by magnetocaloric (mc) cooling.
Concepts for pulsed or short-term operation.
• Conduction of heat into heat sink so massive that the temperature rise is acceptably small.
• Conduction of heat to reserve of phase-change material (paraffins, hydrated salts such as
cacl2.6h2o); heat absorbed by the latent heat of melting.
, • Conduction of heat to sacrificial evaporative coating; heat removed by latent heat of
evaporation.
E1.4 function structures. Make a function-structure diagram for the heat sinks.
Answer. The diagram is shown below.
E1.5 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.
Answer.
Systems that rely on elastic stiffness (thus, elastic modulus) to provide the attachment force.
Wood mild steel spring steel spring steel polypropylene
Systems that rely on strength or plasticity to provide the attachment force.
Mild steel brass brass
