Материаловедение: свойства металлов. Матросова Т.А - 23 стр.

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23
сплавов на основе никеля? 10. Зависит ли деформационное упрочнение от
структуры кристаллической решетки? 11. Чем обусловлена скорость
деформационного упрочнения в материалах с ГЦК-решеткой? 12. Дайте
сравнение скорости упрочнения меди и алюминия. 13. В какой решетке
реализуется механизм пластической деформации двойникованием? 14. Укажите
факторы, влияющие на деформационное упрочнение металлов. 15. Укажите
преимущества и недостатки деформационного упрочнения.
Topic 8. Relative cost of engineering materials
The design engineer is responsible for the initial specification of a material,
yet in many cases he spends little time checking alternatives. Many designers feel
that their obligation ends with the functional design, so they tend to minimize the
importance of material selection. The reasons are many, but two are likely to be (1)
lack of proper education in their engineering courses and (2) inadequate time
because of the need to meet a deadline.
In over 90 percent of all designs a material is selected primarily on the basis of
yield strength and ability to fill space
at the lowest cost. In some cases, other
criteria, depending primarily on
physical properties such as electrical
conductivity or chemical properties
such as corrosion resistance, are
dictated by the end-use of the design
and form the basis for the material
specification.
It is the designer's responsibility
to match the functional and esthetic
requirements of his design with the
behavior of a particular material so
that the total cost after manufacture is
minimized. In a large organization,
this undertaking is a team effort in
which design engineers, production
engineers, and materials specialists all play an important role. In a small company,
the designer may handle the entire assignment.
The costs of engineering materials are in a constant state of flux. Three
components may be recognized: first, the general price changes that follow the ebb
and flow of the national economy; second, the supply-and-demand effect on the
price of some metals, specifically copper and nickel; and finally, the effect of rising
production capacity and strong competition, as found in the polymer industry since
Plastics
Non ferrous castings
Steel castings
Cast irons
Wrought
steel
(forgings)
Sheet
Fig. 8.1. Comparative cost/unit
volume for several materials
Poud/libra
Per pound

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