Midterm 1b

Midterm 1b - . In a carburization process of a large steel...

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1 Louisiana State University Mechanical Engineering Department ME 2733- Materials of Engineering; Spring 2003 (Section 2) Midterm Exam Part II March 25, 2003 Name:_________________________ Problem 1 . Consider a copper sample with the energy for vacancy formation Q v =0.9eV/atom. Knowing that at 400 o C the equilibrium concentration of vacancies is 1.46x10 22 vacancies/m 3 what is the vacancy concentration at 900 o C? The Boltzmann’s constant is k=8.62x10 -5 eV/atom K.
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2 Name:_________________________ Problem 2 . Consider a 5 mm thick steel plate through which a steady state diffusion of carbon takes place. The concentrations of carbon at the two faces are maintained constant at 0.62 Kg/m 3 and 0.17 Kg/m 3 . Knowing that the pre-exponential coefficient D 0 =6.2x10 -7 m 2 /s and the activation energy for diffusion is Q d = 80,000J/mol compute the temperature at which we have a diffusion flux of 5.8x10 -10 Kg/m 2 s.
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3 Name:_________________________ Problem 3
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Unformatted text preview: . In a carburization process of a large steel sample the concentration of carbon at the surface is c s =1.0 wt%. The initial carbon content of the steel is c =0.2wt%. How long it would take to reach a carbon content of 0.6 wt% at a distance of 1 mm from the surface. The diffusion coefficient at the processing temperature is D=2.98x10-11 m 2 /s. 4 Name:_________________________ Problem 4 . A cylindrical specimen of a metallic alloy is stressed in tension. The initial specimen diameter is 10 mm and the material parameters are: yield strength σ y =200 MPa, elastic modulus E=90GPa and the shear modulus G=36GPa. a) What is the maximum value of the load that this specimen supports while still in the elastic regime? b) What is the Poisson’s ratio for this alloy? c) What is the final diameter of the specimen if the tensile load is F=12000N ? d) Evaluate the modulus of resilience for this alloy....
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This note was uploaded on 01/22/2012 for the course ME 2733 taught by Professor Meng during the Fall '10 term at LSU.

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Midterm 1b - . In a carburization process of a large steel...

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