Page 262 - Marks Calculation for Machine Design

P1: Shibu
January 4, 2005
14:56
Brown.cls
Brown˙C06
244
s 2 STRENGTH OF MACHINES
Boundary of allowable Biaxial where
s = s > 0
combinations 1 2
3
84
Biaxial where
s = 2s > 0
2
1
2
–84
s 1
84
Uniaxial where
> 0, s = 0
s 1
5 2
4
–84
Pure shear where
> 0, s = –s
s 1 2 1
Scale: 7 MPa ¥ 7 MPa
FIGURE 6.9 Principal stress combinations in Example 1 (SI/metric).

Example 5 (Sec. 5.2):

1/2
2 2 2 2 1/2

σ + σ − σ 1 σ 2 1 ((83) + (−33) − (83)(−33))
1 2
= =
S y n 84
1 (6,889 + 1,089 + 2,739) 1/2 (10,717) 1/2 103.52
= = = = 1.23
n 84 84 84
1
n = = 0.81 (unsafe)
1.23
Example 2 (Sec. 5.3):

1/2
2 2 2 2 1/2

σ + σ − σ 1 σ 2 1 ((84) + (0) − (84)(0))
1 2
= =
S y n 84
1 (7,056 + 0 + 0) 1/2 (7,056) 1/2 84
= = = = 1.0
n 84 84 84
1
n = = 1.0 (okay, but marginal)
1.0