In the Following Question, Select (Circle) the Most Appropriate Answer

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

6 /1 Mechanics of 17/3/2013 Materials

Notes Max. mark

2 Mechanics of 17/3/2013 Materials

:(Problem (1

:In the following question, select (circle) the most appropriate answer :The material is said to behave elastically if -1 .The strain is linearly proportional to stress .a

.The strain disappears when stress is removed .b

.The ratio between stress and strain is constant .c

.All of the above .d

:Referring to Figure-1, material A is -2

.Stronger and more ductile than material B .a More brittle with larger (E) than that of material B .b .Weaker and more brittle than material B .c .More ductile with smaller (E) than that of material B .d

:In Figure-2, two bars of same cross section and material but of different length -3 Axial (normal) stress in member A is smaller than that of member B .a

Axial strain in member A is equal to that of member B .b

Axial strain in member A is small than that of member B .c

.Total elongation of member A is equal to that of member B .d

In Figure-3, two bars of same cross section and length but of different materials (E) are fixed -4 :together and restrained at A and B. If a force (P) is applied as shown then (reaction (Ra) > reaction ( Rb .a

(reaction (Ra) < reaction ( Rb .b

(reaction (Ra) = reaction ( Rb .c

When subjected to torsion, a ductile specimen usually -5 breaks along a plane of maximum tension .a

breaks along a vertical plan .b

breaks along a plane of maximum shear .c

.None of the above .d

:Poisson’s Ratio is defined as -6 (Ratio (lateral elongation/axial elongation .a

(Ratio (lateral stress / axial stress .b

(Ratio (lateral strain / axial strain .c

(Ratio (lateral load / axial load .d

:(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.

4 Mechanics of 17/3/2013 Materials

:(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 

:(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 