ENGR 0022
Structure and Properties of Materials
Exam 2
Spring 2026
Name (print): ______________________________________________
• 50 minutes
• Closed book
• You can use a calculator
I have neither given nor received unauthorized assistance on this test:
Signature: ________________________________________________
, Section 1
True/False Questions (2 points each, 20 points total)
__F__ 1. An edge dislocation is a planar defect created by adding an extra half plane of atoms
into the crystal structure. An edge dislocation is a linear defect.
__F__ 2. The slip vector of a screw dislocation is perpendicular to the dislocation line.
__T__ 3. Dislocation density is defined as the total number of dislocations per unit area. It is
equal to the total length of dislocations per unit volume, which is also equal to the total
number of dislocations per unit area.
__F__ 4. The way to strengthen a brittle material is to impede dislocation motion.
__F__ 5. The elastic modulus of a metal is much lower than the ideal strength. The elastic
modulus is approximately equal to the ideal strength multiplied by 10 or 15.
__F__ 6. Hard silicon carbide particles are added to an aluminum alloy to make a composite
material. If the volume fraction of silicon carbide particles is kept the same but their
size is decreased, the yield strength of the material would decrease. Decreasing the
particle size at constant volume fraction will increase the number of particles per unit
volume and decrease the spacing, which will increase the strength.
__T__ 7. Cracks propagate when the stress intensity factor exceeds a critical value, which is
called the fracture toughness.
__F__ 8. The way to strengthen a ductile metal is to eliminate defects which concentrate
stress, such as cracks.
__T__ 9. Thermal strains are produced in materials when the temperature changes.
__T__ 10. A coating with a relatively high thermal expansion coefficient is bonded to a massive
substrate with a lower thermal expansion coefficient at 300 K and is slowly cooled to
200 K. If the coating was stress-free at 300 K, it will be in tension at 200 K.
Structure and Properties of Materials
Exam 2
Spring 2026
Name (print): ______________________________________________
• 50 minutes
• Closed book
• You can use a calculator
I have neither given nor received unauthorized assistance on this test:
Signature: ________________________________________________
, Section 1
True/False Questions (2 points each, 20 points total)
__F__ 1. An edge dislocation is a planar defect created by adding an extra half plane of atoms
into the crystal structure. An edge dislocation is a linear defect.
__F__ 2. The slip vector of a screw dislocation is perpendicular to the dislocation line.
__T__ 3. Dislocation density is defined as the total number of dislocations per unit area. It is
equal to the total length of dislocations per unit volume, which is also equal to the total
number of dislocations per unit area.
__F__ 4. The way to strengthen a brittle material is to impede dislocation motion.
__F__ 5. The elastic modulus of a metal is much lower than the ideal strength. The elastic
modulus is approximately equal to the ideal strength multiplied by 10 or 15.
__F__ 6. Hard silicon carbide particles are added to an aluminum alloy to make a composite
material. If the volume fraction of silicon carbide particles is kept the same but their
size is decreased, the yield strength of the material would decrease. Decreasing the
particle size at constant volume fraction will increase the number of particles per unit
volume and decrease the spacing, which will increase the strength.
__T__ 7. Cracks propagate when the stress intensity factor exceeds a critical value, which is
called the fracture toughness.
__F__ 8. The way to strengthen a ductile metal is to eliminate defects which concentrate
stress, such as cracks.
__T__ 9. Thermal strains are produced in materials when the temperature changes.
__T__ 10. A coating with a relatively high thermal expansion coefficient is bonded to a massive
substrate with a lower thermal expansion coefficient at 300 K and is slowly cooled to
200 K. If the coating was stress-free at 300 K, it will be in tension at 200 K.
