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ME 375
HOMEWORK #6
Spring 2009
Out:
February 25, 2009
Due:
March 4, 2009 (at the beginning of class)
PROBLEM 1:
(35%)
A simple quartercar model of the suspension system in an automobile is shown below:
where
m
is ¼
the mass of the car body (the sprung mass),
k
is the suspension spring stiffness, and
b
is
the shock absorber damping.
The body displacement
y
is measured relative to static equilibrium.
The
displacement
r
is the input and represents the road surface profile.
(a)
Determine the equation of motion for this suspension system.
(b)
Assuming that
m
= 400 kg and
k
= 160,000 N/m, write the differential equation from part (a) in
terms of these numbers and the asyetunknown damping coefficient
b
.
(c)
Generate expressions that relate natural frequency and damping ratio to the numbers given in
part (b) as well as the damping coefficient
b
.
(d)
As part of a design project, you’ve been asked to select an appropriate shock absorber for this car
that provides a damping ratio close to 0.707.
Your choices of shock absorber have the following
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This note was uploaded on 08/28/2010 for the course ME 375 taught by Professor Meckle during the Spring '10 term at Purdue UniversityWest Lafayette.
 Spring '10
 Meckle

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