This is a materials Engineering class This is a materials Engineering class Thin
ID: 1842284 • Letter: T
Question
This is a materials Engineering class
This is a materials Engineering class
Think of a design where the selection of materials is critically important. write a one-page summary describing the design and the materials used to insure the design was successful. Be prepared to present your work to the class. Some questions for consideration: Why were those particular materials used? Where were other materials not used? What is the key design parameter(s) needing to be solved? High strength, low thermal conductivity, electrical isolation? small, lightweight? Was the design successful? How could it have been more successful? Is this an old design that could benefit from new materials being developed?
Explanation / Answer
Let us take the example of a turbine of a jet engine. In a turbine, fluid is expanded to extract useful work and therefore the pressure of the fluid falls across each turbine stage. The amount of power that can be extracted from a turbine stage is extremely high and a single turbine blade may contribute up to 250 BHP. So, an important part of a turbine is the design of the blade, which should be capable of withstanding high residual stresses, high temperature and high fatigue loads. This is done by constructing velocity triangles for each blade, by taking into account the tangential speed of the rotor and the stator.
The common choice for the material of a blade is Inconel, a Nickel based alloy, well suited for high temperature applications. It also exhibits excellent tensile and creep rupture strength. Corrosion and oxidation resistance of this alloy is excellent.
Other materials would not be able to withstand the high stress generated due to very high temperatures reached at turbine entry (around 1200- 1500 degree C). They would also be susceptible to creep rupture and corrosion.
The key design parameters would be high strength, high corrosion and oxidation resistance.
The design was successful. More success could have been achieved by heat treatment of Inconel parts.
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