Problems – Mechanical Properties
1. A tensile test is to be performed on a piece of plaincarbon steel plate. Suppose its yield
stress is 50 ksi and its ultimate tensile stress is 65 ksi. The plate is 16 gauge (i.e. thickness =
0.05082”). For a flat tensile specimen cut from this plate with a gauge width of 0.75 in, does the
tensile test instrument have sufficient capacity to break tensile bars of this steel if the maximum
load it can apply is 10,000 lbs.? Quantitatively justify your answer.
2. A plaincarbon steel has a yield strength of 35 ksi, a tensile strength of 52 ksi and a modulus
of 29,000 ksi. Suppose a 3 inch diameter rod of this steel with a length of 10 feet is loaded in
tension with 10,000 pounds of force.
a. Determine the stress in the rod.
b. Determine the total strain of the rod.
c. What component of this strain is due to plastic deformation? Briefly explain.
3.
Steel pipe employed for oil drilling operations is made up of many segments joined
sequentially and suspended in an oil well. Suppose the pipe used in one such application has an
outer diameter of 7.5cm and an inner diameter of 5cm, a density of 7.90Mg/m
3
, and a yield
strength of 900MPa. If the pipe is designed with a safety factor of two [i.e. the maximum stress
in the field must be less than half the rated yield stress], what is the maximum depth that can be
safely reached for drilling. Where does the maximum elastic strain occur in the pipe?
4. During the growth of silicon singlecrystal boules, a small seed of silicon single crystal is
immersed in a melt of liquid silicon and then slowly removed from the melt. Silicon atoms from
the melt deposit on the solid surface, and the crystal grows at the melt surface as the seed is
pulled from the melt. The result is a singlecrystal solid with a circular cross section whose
length can be as much as 12 m. What is the maximum boule length that can be supported by the
seed if the boule diameter is 15 cm and the yield stress of Si is 210 MPa?
5. An 188 stainless steel is characterized by the following mechanical properties:
σ
y
= 120 ksi;
σ
T
= 180 ksi; elongation to failure = 12%; E = 12,000 ksi
Using these four properties as guides, sketch a welllabeled stressstrain diagram for this
material.
6. Given the following properties describing Ti6Al4V, sketch a possible stressstrain diagram
for this material: E = 110 GPa;
σ
y
= 825 MPa;
σ
T
= 895 MPa; % elongation to failure = 10
7. For the 7075T6 aluminum alloy described in the adjacent diagram, determine:
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a. the yield stress;
b. the tensile stress;
c. the elongation to failure; and
d. the modulus.
Suppose a tensile bar of this alloy is
deformed in tension to an
engineering strain of 0.02, the load
is released to F=0, then the
same bar is used in a second
identical tensile test. Sketch the
stressstrain curve for the second
test. Identify (i.e. give specific
values) the elastic modulus, the
yield stress, the ultimate tensile
stress, and the percent elongation to
failure.
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 Spring '09
 LIBERA
 Tensile strength, c.

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