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A nickel engine part is coated with SiC to provide corrosion resistance at high temperatures. If no residual stresses are present in the part at 20°C, determine the thermal stresses that develop when the part is heated to 1000°C during use. The elastic modulus of SiC is 60 × 106 psi. The Coefficient of Thermal Expansion for SiC is 4.0 x 10-6 / °C. If the SiC goes past a tensile strength 25,000 psi, the coating will crack. Does the thermal stress go over 25,000 psi?

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whitneytr12

Answer:

σ = 235200 psi.

Yes, the thermal stresses go over 25000 psi.        

Explanation:  

The thermal stresses (σ) can be calculated by:

[tex] \sigma = E \alpha \Delta T [/tex]  

where α: is the Coefficient of Thermal Expansion, E: is the Young's Modulus and [tex] \Delta T = T_{f} - T_{o} [/tex], [tex] T_{f}[/tex]: is the final temperature and [tex]T_{o}[/tex]: is the initial temperature.

[tex] \sigma = 4.0 \cdot 10^{-6} \cdot 60 \cdot 10^{6} (1000 - 20 ) = 235200 psi [/tex]

So, when the SiC is heated to 1000 °C, it develops 235200 psi of thermal stresses.

The answer to the question is yes, the thermal stresses go over 25000 psi.    

I hope it helps you!  

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