Page 48 - Marks Calculation for Machine Design

P1: Shibu
January 4, 2005
12:26
Brown.cls
Brown˙C01
STRENGTH OF MACHINES
30
A = bh 4
3h
y = h y = 8
h 4
b
FIGURE 1.30 Intermediate first moment.
Direct Shear Versus Shear Owing to Bending. In Sec. 1.1.2 the rivet holding together
the two overlapping bars shown in Fig. 1.31 was said to be under direct shear loading.

P
P
Riveted joint
FIGURE 1.31 Direct shear loading.

It was found that if the rivet is cut in half at the overlap to expose the cross-sectional area
(A) of the rivet, then Fig. 1.32 shows the resulting free-body-diagram.

V
P
FIGURE 1.32 Free-body-diagram.

From equilibrium, the shear force (V ) is equal to the applied force (P), and the shear
stress (τ) is given by Eq. (1.43) as
V P
τ = = (1.43)
A A rivet
Consider the overlapping joint shown in Fig. 1.33, where again the rivet is under direct
shear loading.

P
2P
P Riveted joint
FIGURE 1.33 Direct shear loading.
To expose the cross sections of the rivet, the top and bottom plates need to be removed
to form the free-body-diagram shown in Fig. 1.34.

V
2P
V
FIGURE 1.34 Direct shear loading.