Assignment(09) 1 – Wk 1 & 2

Q1 Figure below shows 6-mm diameter steel pins fixed at A, B and C. The allowable shear stress of those pins are 90 MPa. The rod CB is 10 mm diameter with an allowable normal stress of 150 MPa. Determine the largest intensity w of the uniformly stibuted load that can be suspended from the beam.

Q2 The bar below is held in equilibrium by the pin supports at A and B. Note that the pin at A has a single leaf and therefore it involves single shear in the pin. The support at B has a double leaf and therefore it involves double shear. The allowable shear stress for the both pins is 125 MPa. If x = 1 m and w = 12 N/m , determine the smallest required diameter of pins A and B. Neglect any axial force in the bar.

Assignment(09) 1 – Wk 1 & 2

Q3 A scissors jack for an automobile is shown in Fig. 2-16. The screw threads exert a force F on the blocks at joint A and B. If F = 700 N, determine the shearing stress on a cross section of the 10 mm diameter pin at C, which is of single shear. When angle,

a) θ = 150

b) θ = 300

c) θ =450

Q4 The front-wheel suspension of an automobile is as shown in the figure. The pavement exerts a vertical force of 2700 N on the tire. Determine the minimum diameters of the pin A, B, C and D if all the pins are double shear and the shear stress in any pin cannot exceed 125 MPa.

Assignment(09) 1 – Wk 1 & 2

Q5 Figure below is a simplified sketch of the mechanism used to raise the bucket of a bulldozer. The bucket and its contents weigh 10 kN and have a center of gravity at H. Arm ABCD has a weight of 2 kN and a center of gravity at B; arm DEFG has a weight of 1 kN and a center of gravity at E. The weight of the hydraulic cylinders can be ignored. Determine the required diameter of the pin at D if the shearing stress cannot exceed 120 MPa. The pin is in double shear. (Hints: use the free body diagram of the bucket and arm DEFG. Neglect the forces on arm ABCD)

Q6 A pair of vise grip pliers is shown in the figure below. When a force P = 100 N is being applied to the handles, determine

a) The average shearing stress in the pin at A if it has a 4 –mm diameter and is in double shear.

b) The average shearing stress in the pin at B if it has a 5 mm diameter and is in double shear.

b=19.1070

Free body diagram of the bucket.

Assignment(09) 1 – Wk 1 & 2

Q7 In the steel structure shown, a 6-mm-diameter pin is used at C and 10-mm-diameter pins are used at B and D. The ultimate shearing stress is 150 MPa at all connections, and the ultimate normal stress is 400 MPa in link BD. Knowing that a factor of safety of 3 is desired, determine the largest load P that can be applied at A. Note that link BD is not reinforced around the pin holes.