(SEM V) THEORYEXAMINATION 2017-18 MACHINE DESIGN - I

Machine Design – I (NME-501 / EME-501)

Section-Wise Important Questions & Study Notes

SECTION–A

(Attempt all | 2 × 10 = 20)
This section checks definitions, concepts, and design philosophy.
Write short, precise answers (2–3 lines).

BIS Method of Specifying Cast Iron
Cast iron is specified by minimum tensile strength (e.g., FG 200, FG 300).
Major types: Grey CI, White CI, Malleable CI, Ductile CI.

Standardization in Design
Standardization means using common sizes, materials, and components to reduce cost, simplify manufacturing, and ease maintenance (e.g., standard bolts, bearings).

Plastics vs Metals
Plastics are lightweight, corrosion-resistant, and cheap but have lower strength and temperature resistance compared to metals.

Factors Reducing Fatigue Strength
Surface finish, size effect, stress concentration, temperature, corrosion, and loading type.

Stress Concentration & Mitigation
Localized increase in stress due to discontinuities; reduced by fillets, keyway reliefs, surface polishing, and proper design.

Caulking & Filleting
Caulking seals riveted joints; filleting provides smooth stress flow at corners.

End Connections of Helical Springs
Plain ends, squared ends, squared and ground ends (draw simple sketch).

Eccentric Riveted Joint
A joint where load does not pass through the centroid of rivet group; designed using direct + secondary shear method.

Distortion Energy Theory
Failure occurs when distortion energy equals that at yield in simple tension (von Mises theory).

R5 & R10 Series (Standard Numbers)
For 5–50 kW (R5): 5, 8, 12.5, 20, 31.5, 50
For expansion to 8 models (R10): 5, 6.3, 8, 10, 12.5, 16, 20, 25, 31.5, 40, 50

SECTION–B

(Attempt any THREE | 10 × 3 = 30)
Design numericals + theory. Write formula → substitution → answer.

1. Overhang Crankshaft (Principal & Shear Stress)

Find bending moment due to tangential load

Combine bending + torsion       Use maximum principal stress and maximum shear stress equations

2. Fatigue Design using Goodman Line           Determine mean stress & alternating stress

Apply Goodman straight line                        Include stress concentration factor & FOS

3. Double Riveted Lap Joint                             Failure modes: tearing, shearing, crushing

Find minimum force per pitch                      Calculate actual stresses at given FOS

4. Protective Type Flange Coupling

Design steps:                                                    Shaft diameter

Key dimensions                                                Bolts (shear & crushing)

Flange dimensions                                           Draw neat assembly sketch

5. Square Threaded Power Screw                    Torque to rotate nut

Power required                                                Efficiency of screw
Include friction at threads and collar.

SECTION–C

(Attempt any ONE | 10 × 1 = 10)

3(a) Design Procedures

(i) Longitudinal Butt Joint of Boiler
Steps: determine plate thickness, rivet diameter, pitch, joint efficiency.

(ii) Bush Pin Type Flexible Coupling
Steps: torque calculation, pin, bush, flange design.

OR

3(b) Axially Loaded Connecting Rod           Completely reversed load

Use fatigue criterion                                    Neglect column action

Find suitable diameter