GTBL042-20 GTBL042-Callister-v3 September 21, 2007 19:48
Learning Objectives
After careful study of this chapter you should be able to do the following:
1.List and briefly discuss three factors over which an
engineer has control that affect the cost of a
product.
2.Diagram the total materials cycle, and briefly
discuss relevant issues that pertain to each stage
of this cycle.3.List the two inputs and five outputs for the life
cycle analysis/assessment scheme.
4.Cite issues that are relevant to the “green design”
philosophy of product design.
5.Discuss recyclability/disposability issues relative to
(a) metals, (b) glass, (c) plastics and rubber, and
(d) composite materials.20.1 INTRODUCTION
In previous chapters, we dealt with a variety of materials science and materials en-
gineering issues to include criteria that may be employed in the materials selection
process. Many of these selection criteria relate to material properties or property
combinations—mechanical, electrical, thermal, corrosion, etc.; the performance of
some component will depend on the properties of the material from which it is made.
Processability or ease of fabrication of the component may also play a role in the
selection process. Virtually all of this book, in one way or another, has addressed
these property and fabrication issues.
In engineering practice there are other important criteria that must be considered
in the development of a marketable product. Some of these are economic in nature
and, to some degree, are unrelated to scientific principles and engineering practice,
and yet are significant if a product is to be competitive in the commercial marketplace.
Other criteria that should be addressed involve environmental and societal issues
such as pollution, disposal, recycling, toxicity, and energy. This final chapter offers
relatively brief overviews of economic, environmental, and societal considerations
that are important in engineering practice.Economic Considerations
It goes without saying that engineering practice involves utilizing scientific principles
to design components and systems that perform reliably and satisfactorily. Another
critical driving force in engineering practice is that of economics: simply stated, the
company or institution must realize a profit from the products that it manufactures
and sells. The engineer might design the perfect component; however, as manufac-
tured, it must be offered for sale at a price that is attractive to the consumer and, in
addition, return a suitable profit to the company.
Furthermore, in today’s world and the global marketplace, economics doesn’t
always mean just the final cost of a product. Many countries have specific regulations
regarding the chemicals used, CO 2 emissions, and end-of-life procedures. Compa-
nies must make sure that they take into consideration a myriad of such factors. For
example, there are instances where deleting toxic chemicals (which are regulated) in
a product results in a cheaper fabrication process.
Only a brief overview of important economic considerations as they apply to
the materials engineer will be provided. The student may want to consult references
provided at the end of this chapter that address engineering economics in detail.
There are three factors over which the materials engineer has control and that af-
fect the cost of a product: they are (1) component design, (2) the material(s) used, and
(3) the manufacturing technique(s) that are employed. These factors are interrelated