Question

SECTION 3 - SHORT ANSWER Consider two different metals: 1040 steel (unalloyed, plain carbon steel - BCC) and 1100 aluminum (commercially pure aluminum alloy - FCC). The 1100 aluminum alloy has a stiffness of 10 E6 psi, and the 1040 steel has a stiffness of 30 E6 psi. a. To think about and compare the properties of these two materials: Sketch a NEAT tensile engineering stress-strain curve where the two materials are placed on the same diagram; use a solid line (__) for 1100 aluminum and a dashed line (---) for 1040 steel. Label the elastic modulus (don't need to put the value of this, just the \"definition\" ) on the aluminum curve. Label the offset (0.2%) yield point on the aluminum curve. Label the ultimate tensile strength on the aluminum curve - not the value ... just the place on the curve b. One of your design criteria for the intended application is impact resistance. Which mechanical property would this correspond to? c. One of these materials (1100 Aluminum or 1040 Steel) will respond better to cold working than the other. Which material is this, and why do you expect it to respond better to cold working? d. Suppose that 1040 steel is a rate-sensitive material. Illustrate (qualitatively) how you would expect its engineering stress-strain curve to differ at low strain rates, moderate strain rates, and high strain rates (ranging from quasi-static testing on an Instron load frame to dynamic testing on a Hopkinson bar). What happens to its strength and ductility as the strain rate increases?

SECTION 3 - SHORT ANSWER
Consider two different metals: 1040 steel (unalloyed, plain carbon steel - BCC) and 1100 aluminum
(commercially pure aluminum alloy - FCC). The 1100 aluminum alloy has a stiffness of 10 E6 psi, and the
1040 steel has a stiffness of 30 E6 psi.
a. To think about and compare the properties of these two materials:
Sketch a NEAT tensile engineering stress-strain curve where the two materials are
placed on the same diagram; use a solid line (__) for 1100 aluminum and a dashed
line (---) for 1040 steel.
Label the elastic modulus (don't need to put the value of this, just the \"definition\" ) on
the aluminum curve.
Label the offset (0.2%) yield point on the aluminum curve.
Label the ultimate tensile strength on the aluminum curve - not the value ... just the
place on the curve
b. One of your design criteria for the intended application is impact resistance. Which mechanical
property would this correspond to?
c. One of these materials (1100 Aluminum or 1040 Steel) will respond better to cold working than
the other. Which material is this, and why do you expect it to respond better to cold working?
d. Suppose that 1040 steel is a rate-sensitive material. Illustrate (qualitatively) how you would
expect its engineering stress-strain curve to differ at low strain rates, moderate strain rates, and
high strain rates (ranging from quasi-static testing on an Instron load frame to dynamic testing
on a Hopkinson bar). What happens to its strength and ductility as the strain rate increases?

Added by Steven G.

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