Question 15.6: Fasteners in Eccentric Shear Problem Determine a size for th...
Fasteners in Eccentric Shear
Problem Determine a size for the dowel pins in the bracket of Figure 15-41.
Given The static force P = 1 200 lb is applied at l = 5 in. The radius to the dowel pins is r = 1.5 in.
Assumptions All pins share load equally. Use 40-48 HRC alloy steel for the pin material.
See Figures 15-41 and 15-42.
1 Calculate the moment of the applied force.
M=P l=1200(5)=6000 lb -\text { in } (a)
2 Calculate the magnitude of the force due to this moment at each pin.
F_M=\frac{M}{n r}=\frac{6000}{4(1.5)}=1000 lb (b)
3 Find the amount of the direct force P felt at each pin.
F_P=\frac{P}{n}=\frac{1200}{4}=300 lb (c)
4 Based on the vector diagram in Figure 15-42, pin B is the most heavily loaded and its resultant force is
F_B=F_P+F_M=300+1000=1300 lb (d)
5 Assume a trial pin diameter of 0.375 in and calculate the direct shear stress in pin B.
\tau=\frac{F_B}{A_B}=\frac{1300(4)}{\pi(0.375)^2}=11770 psi (e)
6 Find the shear yield strength of the material from Table 15-12 and calculate the safety factor against static shear failure.
N_s=\frac{S_{y s}}{\tau}=\frac{117000}{11770}=10 (f)
7 The files EX15-06 can be found on the CD-ROM.
| Table 15-12 Minimum Strengths for Dowel Pins in Double Shear. Source: Drive-Lok, Inc., Sycamore, Ill. |
|
| Material | S_{ys} (kpsi) |
| Low-carbon steel | 50 |
| Alloy steel 40-48 HRC | 117 |
| Corrosion-resistant steel | 82 |
| Brass | 40 |
