4.39 and 4.40 A copper strip (Ec = 105 GPa) and an aluminum strip (Ea = 75 GPa) are bonded together to form the composite beam shown. Knowing that the beam is bent about a horizontal axis by a couple of moment M = 35 N·m, determine the maximum stress in (a) the aluminum strip, (b) the copper strip.
Fig. P4.39
(a)
Find the maximum stress in the aluminum strip.
Answer to Problem 39P
The maximum stress in the aluminum strip is
Explanation of Solution
Given information:
The modulus of elasticity
The modulus of elasticity
The moment (M) in the beam is
Calculation:
Show the cross-section of the composite bar as shown in Figure 1.
Refer Figure 1.
Consider the Copper and Aluminum is represented by rectangle 2 and 1.
The width and depth of the rectangle 1 are
The width and depth of the rectangle 2 are
Consider Aluminum as the reference material, then the value of
Calculate the ratio
Substitute
Calculate the distance (
Here,
The value of
Substitute
Consider the entire cross-section of the composite bar is transformed into Aluminum.
Calculate the moment of inertia
Substitute
Calculate the moment of inertia
Substitute
Calculate the moment of inertia of the transformed cross-section using the relation:
Substitute
Calculate the maximum stress (
Calculate the maximum stress for Aluminum strip as follows:
Substitute
Thus, the maximum stress in the aluminum strip is
(b)
Find the maximum stress in the aluminum strip.
Answer to Problem 39P
The maximum stress in the aluminum strip is
Explanation of Solution
Given information:
The modulus of elasticity
The modulus of elasticity
The moment (M) in the beam is
Calculation:
Calculate the maximum stress for Copper strip as follows:
Substitute
Thus, the maximum stress in the copper strip is
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Chapter 4 Solutions
Mechanics of Materials, 7th Edition
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