1. A sheet of steel 1.9 mm thick has nitrogen atmospheres on both sides at 1200°C and is permitted to achieve a steady-state diffusion condition. The diffusion coefficient for nitrogen in steel at this temperature is 5.4 × 10-11 m2/s, and the diffusion flux is found to be 2.8 × 10-7 kg/m2-s. Also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4.6 kg/m3. How far into the sheet from this high-pressure side will the concentration be 2.7 kg/m3? Assume a linear concentration profile.
m
2. For a steel alloy it has been determined that a carburizing heat treatment of 10.4 h duration will raise the carbon concentration to 0.37 wt% at a point 1.5 mm from the surface. Estimate the time necessary to achieve the same concentration at a 5.3 mm position for an identical steel and at the same carburizing temperature.
t =
h
3. The diffusion coefficients for carbon in nickel are given at two temperatures:
T(˚C) D(m2/s)
600 5.5 × 10-14
700 3.9 × 10-13
(a) Determine the value of D0.
m2/s (Use scientific notation.)
(b) Determine the value of Qd.
kJ/mol
(c) What is the magnitude of D? at 870˚C.
m2/s (Use scientific notation.)
3.
4. Using the Tabulation of Diffusion Data, answer the following:
(a) Calculate the diffusion coefficient for Cu in Ni at 550˚C.
m2/s (Use scientific notation.)
(b) What time (in h) will be required at 600˚C to produce the same diffusion result (in terms of concentration at a specific point) as for 10 h at 550˚C?
h
4. Determine the carburizing time necessary to achieve a carbon concentration of 0.49 wt% at a position 4.7 mm into an iron-carbon alloy that initially contains 0.11 wt% C. The surface concentration is to be maintained at 1.2 wt% C, and the treatment is to be conducted at 1090°C. Assume that D0 = 1.6 × 10-5 m2/s and Qd = 169 kJ/mol.
From Equation 5.5 calculate the Gaussian error function:
=
5.
A cylindrical specimen of a hypothetical metal alloy is stressed in compression. If its original and final diameters are 22.656 and 22.684 mm, respectively, and its final length is 78.4 mm, calculate its original length if the deformation is totally elastic. The elastic and shear moduli for this alloy are 106 GPa and 31.2 GPa, respectively.
mm
6. A cylindrical specimen of a hypothetical metal alloy is stressed in compression. If its original and final diameters are 22.656 and 22.684 mm, respectively, and its final length is 78.4 mm, calculate its original length if the deformation is totally elastic. The elastic and shear moduli for this alloy are 106 GPa and 31.2 GPa, respectively.
mm
7. A bar of a steel alloy that exhibits the stress–strain behavior shown in the Animated Figure 6.22 is subjected to a tensile load; the specimen is 375 mm (14.8 in.) long and has a square cross section 5.5 mm (0.22 in.) on a side.
(a) Compute the magnitude of the load necessary to produce an elongation of 7.5 mm (0.30 in.).
N
(b) What will be the deformation after the load has been released?
mm
8. An alloy to be used for a spring application must have a modulus resilience of at least 0.90 x 106 J/m3 (0.90 x 106 Pa). What must be its minimum yield strength (in MPa)? Assume that the modulus of elasticity for this alloy is 107 GPa.
MPa
9. For some metal alloy, a true stress of 345 MPa (50040 psi) produces a plastic true strain of 0.02. How much will a specimen of this material elongate when a true stress of 413 MPa (59900 psi) is applied if the original length is 490 mm (19.29 in.)? Assume a value of 0.22 for the strain-hardening exponent, n.
mm
10. (a) What is the indentation diagonal length when a load of 0.75 kg produces a Vickers HV of 460?
mm
(b) Calculate the Vickers hardness when a 680-g load yields an indentation diagonal length of 0.029 mm.
HV
PLACE THIS ORDER OR A SIMILAR ORDER WITH US
