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Unformatted text preview: Sec_2.8-2.12.qxd 9/25/08 11:44 AM Page 219 SECTION 2.8 Impact Loading Problem 2.8-10 A bumping post at the end of a track in a railway
yard has a spring constant k 8.0 MN/m (see figure). The maximum
possible displacement d of the end of the striking plate is 450 mm.
What is the maximum velocity max that a railway car of weight
W 545 kN can have without damaging the bumping post when it
strikes it? Solution 2.8-10 Bumping post for a railway car
STRAIN ENERGY WHEN SPRING IS COMPRESSED TO THE
MAXIMUM ALLOWABLE AMOUNT U kd2
2 CONSERVATION OF ENERGY
k 8.0 MN/m d maximum displacement of spring d
Find max W 545 kN 450 mm v vmax KINETIC ENERGY BEFORE IMPACT
2g vmax kd2 2
2 A W/g d kd2
W/g k ; A (545 kN)/(9.81 m/s2) SUBSTITUTE NUMERICAL VALUES: max Mv2
2 U Wv2
2g 8.0 MN/m (450 mm) 5400 mm/s 5.4 m/s Problem 2.8-11 A bumper for a mine car is constructed with
a spring of stiffness k 1120 lb/in. (see figure). If a car weighing
7 mph when it strikes the
3450 lb is traveling at velocity
spring, what is the maximum shortening of the spring? ; v
k 219 ...
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This note was uploaded on 12/22/2011 for the course MEEG 310 taught by Professor Staff during the Fall '11 term at University of Delaware.
- Fall '11