Download Mid-term Dr naser 2013-1

The Islamic University of Gaza
Civil Engineering Department
2nd Semester 2012-2013
Instructors: Dr. Nasreddin Elmezaini
T.A. : Eng. Belal El Harazin
Date: March 17, 2013
Mechanics of Materials (ECIV 2313)
1st Midterm Exam 17/ 3 / 2013
Time Allowed: 80min.
11:00 - 12:20
Student Name
Q. No
Mark
ID
Max. mark
1
6
2
12
3
12
4
10
Total
40
1/ 5
Notes
Mechanics of Materials
17/3/2013
Problem (1):
In the following question, select (circle) the most appropriate answer:
1- The material is said to behave elastically if:
Mat. A
The strain is linearly proportional to stress.
The strain disappears when stress is removed.
The ratio between stress and strain is constant.
All of the above.
Stress
a.
b.
c.
d.
Mat. B
Strain
2- Referring to Figure-1, material A is:
Figure-1
a.
b.
c.
d.
Stronger and more ductile than material B.
More brittle with larger (E) than that of material B
Weaker and more brittle than material B.
More ductile with smaller (E) than that of material B.
A
B
3- In Figure-2, two bars of same cross section and material but of different length:
a.
b.
c.
d.
Axial (normal) stress in member A is smaller than that of member B
Axial strain in member A is equal to that of member B
Axial strain in member A is small than that of member B
Total elongation of member A is equal to that of member B.
P
Figure-2
P
4- In Figure-3, two bars of same cross section and length but of different materials (E) are fixed
together and restrained at A and B. If a force (P) is applied as shown then:
a. reaction (Ra) > reaction ( Rb)
b. reaction (Ra) < reaction ( Rb)
c. reaction (Ra) = reaction ( Rb)
Ra
5- When subjected to torsion, a ductile specimen usually
a.
b.
c.
d.
breaks along a plane of maximum tension
breaks along a vertical plan
breaks along a plane of maximum shear
None of the above.
6- Poisson’s Ratio is defined as:
a.
b.
c.
d.
Ratio (lateral elongation/axial elongation)
Ratio (lateral stress / axial stress)
Ratio (lateral strain / axial strain)
Ratio (lateral load / axial load)
2/ 5
E1
E2
P
E1 > E2
Figure-3
Rb
Mechanics of Materials
17/3/2013
Problem (2):
A 15 mm diameter steel rod AB is fitted to a round hole near end C of the wooden member CD.
For the loading shown, determine:
A. the maximum average normal stress in the wood,
B. the distance “b” for which the average shearing stress is 1.5 MPa on the surfaces
indicated by the dashed lines,
C. the average bearing stress on the wood.
3/ 5
Mechanics of Materials
17/3/2013
Problem (3):
Link BD is made of brass (E = 105 GPa) and has a cross-sectional area of 240 mm2. Link CE is
made of aluminium (E = 72 GPa) and has a cross-sectional area of 300 mm2.
Knowing that they support rigid member ABC, if a force of 18 KN applied vertically at point
A.
 Determine the deflection of point A.
4/ 5
Mechanics of Materials
17/3/2013
Problem (4):
The allowable shear stress is 50 MPa in the brass rod AB (diameter = 50 mm) , and 25 MPa in
the aluminium rod BC (diameter = 65 mm).
 Determine the maximum allowable Torque applied at A.
5/ 5