Page 296 - Shigley's Mechanical Engineering Design

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Fatigue Failure Resulting from Variable Loading 271

Medium-carbon steel
(ASTM A186)
30 dia
Web

Fracture Flange
(1 of 2)
Fracture Tread
(a) Coke-oven-car wheel

Figure 6–7

Fatigue failure of an ASTM A186 steel double-flange trailer wheel caused by stamp marks. (a) Coke-oven car wheel showing position of
stamp marks and fractures in the rib and web. (b) Stamp mark showing heavy impression and fracture extending along the base of the lower
row of numbers. (c) Notches, indicated by arrows, created from the heavily indented stamp marks from which cracks initiated along the top
at the fracture surface. (From ASM Metals Handbook, Vol. 11: Failure Analysis and Prevention, 1986, ASM International, Materials Park,
®
OH 44073-0002, fig 51, p. 130. Reprinted by permission of ASM International , www.asminternational.org.)

Figure 6–8 Aluminum alloy 7075-T73
Rockwell B 85.5
4.94
Aluminum alloy 7075-T73 25.5
landing-gear torque-arm 10.200
assembly redesign to eliminate
fatigue fracture at a lubrication
hole. (a) Arm configuration,
original and improved design
(dimensions given in inches). Fracture Lug
(b) Fracture surface where (1 of 2)
A
arrows indicate multiple crack
origins. (From ASM Metals Primary-fracture
Handbook, Vol. 11: Failure Lubrication hole surface
Analysis and Prevention, 1986, 1.750-in.-dia Lubrication hole
ASM International, Materials bushing,
0.090-in. wall
Park, OH 44073-0002, fig 23,
p. 114. Reprinted
by permission of ASM
1 in
®
International ,
www.asminternational.org.) 3.62 dia Secondary
fracture
Original design Improved design
Detail A
(a)