Engineering Stress And Strain Case Study

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1) What are engineering stress and strain?
Answer:
Engineering Stress:
Engineering stress is also called nominal stress, and it is defined as the applied load divided by the original cross sectional area of the material.
Engineering Strain: Engineering strain is defined as the amount of material that deforms per unit length in a tensile test. Engineering strain is also known as nominal strain.

2) In the figure below, graphically show the toughness of three class materials: Ceramics, Metals, and Polymers (un-reinforced)

3) Where is the elastic recovery in the graph below?

4) What is the relation between the yield strength of a material and the size of the grain in polycrystalline metal? What
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But on the other hand at higher cooling rates crystallization during solidification of a eutectic mixture will be much more clearly separated.
14) List the main characteristics of thermoplastic and thermoset polymers.
Answer # 14:
Thermoplastic Polymers:
Thermoplastics are defined as polymers that can be melted and recast for dissimilar use virtually indeterminately. They should be distinguished from thermoset materials which cure, or develop set, when they are heated. Thermoplastic materials are melt processable, which is they are formed, when they are in melted or viscous phase. Thermoplastics used in bearings, cup boards and gear wheels etc.
Thermoset Polymers:
Thermoset plastics are normally strong and resistant to heat, for the reason is that they melt first time, when they are heated to very high T and set permanent while cooling, they can never be melted or reshaped again. Thermoset plastic is used in kitchen work surface and in plastic cups.
15) What is the repeating unit in Polytetrafluoroethylene (PTFE)? Please provide a graphical answer.
Answer # 15:
The repeating unit of PTFE is
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OR
Self-diffusion is atomic migration in pure metals--i.e., when all atoms exchanging positions are of the same type. Inter diffusion is diffusion of atoms of one metal into another metal.

18) From the table below, compute the value of diffusion coefficient, D, for the diffusion of zinc in copper at 650C. Answer # 17:
D = (2.4 × 10-5 m2 /s) exp − 189,000 J/mol / (8.31 J/mol- K) (650 + 273 K) = 4.8 × 10-16 m2 /s
19) Extra Credit Question
Research Shape Memory Alloys and include information about their history, properties and the mechanism at the crystal structure level, which explains their unique properties
Answer # 19:
Shape Memory alloys is the materials that change shape by applying heat. It is a unique class of alloys that can recover apparent permanent strains when they are heated above certain temperature.
History:
Shape memory alloys were first discovered in 1930 by Olander in his studies.
Types:
1. One way memory effect
2. Two way memory effect
Advantages:
1. Bio- compatibility
2. Diverse fields of applications
3. Strong corrosion

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