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Mech Sol - 2020 - Compre Part A&b

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BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI

First Semester 2019-2020


ME/ MF F211: Mechanics of Solids
Comprehensive Regular Examination
Date: 6.12.19 Time: 1 Hr Max Marks: 30

Note: (1) There are total 4 questions


(2) Both side of the paper is printed.
(3) The time allotted is 1 hr for Part-A but you can take time as per your convenience. After
submitting Part- A, you can take the question paper and answer sheet for Part- B.
___________________________________________________________________________
PART-A(CLOSED BOOK)

Q1. Bracket ABCD of solid circular cross-section has the shape and dimension (b = 37mm) as
shown in FigQ1. A vertical and horizontal load P (40 N) acts at the free end D.
(a) Draw the bending moment diagram of bracket ABCD. Hint: Show the variation of
bending moment along segments AB, BC and CD separately.
(b) Determine the minimum permissible diameter dmin of the bracket, if the allowable
bending stress in the material is 30 MPa. (Neglect the weight of bracket) [8]

Fig Q1

Q2. The principal strains in the plane of a flat aluminum plate loaded in its plane are
 1  8.1  10 4  2  5.7  10 4 . Using Mohr’s circle, find x, y, and xy where the x and y
axes are as shown in FigQ2. Take E = 72GPa and  = 0.33. [7]

Fig Q2
Q3. The curved cantilever beam in FigQ3 has a radius of curvature R and a circular cross
section of diameter d. It is subjected to a point load P at point B.
(a) Determine the reactions (i.e. axial force, shear force and bending moment) acting at any
section θ in the curved cantilever beam AB.
(b) Using Castigliano’s method (the strain energy method), determine the vertical
deflection of point B in terms of P, modulus of elasticity E, radius of curvature R, cross-
section area A, and moment of inertia of the cross section I. Neglect the effect of strain
energy due to shear [8]

Fig Q3

Q4. The state of plane stress shown (in FigQ4) occurs at a critical point of a steel machine
components. As a result of several tensile tests, it has been found that the tensile yield
strength is Y = 270 MPa for the grade of steel used. Determine the factor of safety with
respect to yield, using
(a) maximum-shearing-stress (MSS) criterion and (b) Distortion energy criterion [7]

Fig Q4
BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI
First Semester 2019-2020
ME F211/MF F211: Mechanics of Solids
Comprehensive Examination
Date: 6.12.19 Time: 2 Hr Max Marks: 50

PART-B (OPEN BOOK)

Q1. In Fig Q1, member OA can be considered rigid and weightless. Column BC is pin-ended and
column DF is pin-ended at A and fixed at F. Both the columns are of solid circular cross-sections
of diameter 10mm. Column BC is made of structural steel (E = 200GPa) and column DF is made
of an Aluminium alloy (E = 72GPa). Determine the magnitude of Q that will cause one of the
columns to buckle. [10]

Q2.The box beam is subjected to the 26 kN inclined force (as shown in FigQ2) that is applied at the
center of its width, 75 mm from each side.
a. Calculate the axial force F, shear force V, and bending moment Mb acting on the cross
section x-x.
b. Determine the stress components (i.e.  x and  xy ) on elements at points A and B.
c. Show these stresses on properly oriented 2-D elements.
d. Determine the principal stresses (i.e.  1 and  2 ) at point A. [18]

Section x-x:

Fig Q2
Q3.The beam AB in FigQ3 is fixed supported to the wall at A and pin connected to a 12 mm
diameter rod BC at B. The beam is subjected to a point load P = 40 kN at D as shown in Fig. If
E = 210 GPa for both the members (i.e. beam AB and rod BC),
a) Determine the force developed in the rod BC due to the loading.
b) State the proper boundary conditions and starting from the fourth-order differential equation
(i.e. the load equation), derive the equation of deflection curve for the beam AB.
c) Determine the deflection of point B on the beam.
The moment of inertia of the beam about its neutral axis is INA= 186 x 106 mm4. [10]

Fig Q3

Q4. The 60-mm diameter shaft ABC is supported by two journal bearings, while the 80-mm
diameter shaft EH is fixed at E and supported by a journal bearing at H (FigQ4). If the
angle of twist at gears A and C is required to be 0.05 rad, determine the magnitudes of the
torques T1 and T2. The shafts are made of A-36steel (G = 80 GPa). [12]

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