ANSWERS

ANNA UNIVERSITY EXAMINATIONS, MAY/JUNE – 2014

ME 2254 - STRENGTH OF MATERIALS

PART – A

1. BULK MODULUS:Bulk modulus is defined as the ratio of direct stress to the volumetric strain. It is denoted

by the letter ‘K’ and its unit is N/mm2.BulkModuls = Direct stress

Volumetric strain

2. RESILIENCE AND PROOF RESILIENCE:Resilience is the ability of a material to absorb the energy within the elastic limit, and

release that energy upon unloading. Proof resilience is defined as the maximum energy that can be absorbed within the elastic

limit, without creating a permanent distortion.

3. SHEAR FORCE AND BENDING MOMENT (BM) DIAGRAM:

4. ASSUMPTIONS MADE IN THEORY OF PURE BENDING:1. The material of the beam is homogeneous and isotropic.2. The value of Young's Modulus of Elasticity is same in tension and compression.3. The transverse sections which were plane before bending remain plane after bending

also.4. The radius of curvature is large as compared to the dimensions of the cross-section.

5. TORSION:Torsion is the twisting of an object due to an applied torque or a couple and its unit is

N·m

Examples: Drive shafts, Axles and Twisted drills

6. TYPES OF SPRINGS:i. Helical spring: They are made of wire coiled into a helical form, the load being

applied along the axis of the helix. They are both used in tension and compression.ii. Leaf springs: They are composed of flat bars of varying lengths clamped together so

as to obtain greater efficiency. These types of springs the major stresses are tensile & compressive.

iii.  Spiral springs: They are made of flat strip of metal wound in the form of spiral and loaded in torsion. In this the major stresses are tensile and compression due to bending.

7. MOHR’S THEOREM I AND II:I. The change of slope between any two points is equal to the net area of the B.M.

diagram between these points divided by EI.II. The total deflection between any point is equal to the net area of the B.M. diagram

between the two points about the last point divided by EI

8. EQUIVALENT LENGTH OF A COLUMN:The effective length of a given column with end conditions is the length of an equivalent

column of the same material and cross-section with hinged ends, and having the value of crippling load equal that of the given column.

9. THICK AND THIN SHELL:If the wall thickness of the shell is less than 1/15 to 1/20 of its internal diameter is

considered as the thin shell. If the wall thickness of the shell is greater than 1/20 of its internal diameter is considered

as the thin shell.

10. PRINCIPAL PLANE:A plane which has no zero shear stress is known as principal plane.