THEORY EXAMINATION (SEM–IV) 2016-17 MANUFACTURING SCIENCE-I

Course: B.Tech (Mechanical Engineering)
Subject Code: EME402
Subject Title: Manufacturing Science – I
Exam Type: Theory
Duration: 3 Hours
Maximum Marks: 100

SECTION – A (10 × 2 = 20 Marks)

Short, concept-based questions to test basic definitions and fundamentals.

SECTION – B (5 × 10 = 50 Marks)

Medium-length descriptive and numerical questions.

(a) Open vs Closed Die Forging & Rolling Defects

Rolling Defects:

Wavy Edges: Uneven thickness

Zipper Cracks: Due to center tension

Edge Cracks: Excessive deformation

Alligatoring: Non-uniform flow

(b) Jigs and Fixtures

Types of Jigs: Plate, box, channel, and sandwich type (with sketches).

(c) Punching vs Blanking & Shear Force

Punching: Hole is workpiece, slug is scrap.

Blanking: Slug is useful, sheet is scrap.

Shear Relation:

• F=τs×A=τsπdtF = \tau_s \times A = \tau_s \pi d tF=τs​×A=τs​πdt

For shear on punch face:

• F=τsπdt1+stF = \frac{\tau_s \pi d t}{1 + \frac{s}{t}}F=1+ts​τs​πdt​

where sss = shear on punch, ttt = thickness.

(d) Design Considerations in Powder Metallurgy

Particle size and shape

Pressing pressure uniformity

Sintering temperature/time

Lubrication and die design

(e) Tresca & Von Mises Criteria

Tresca (Maximum Shear Stress):

• σ1−σ3=2k\sigma_1 - \sigma_3 = 2kσ1​−σ3​=2k

Von Mises (Distortion Energy):

• (σ1−σ2)2+(σ2−σ3)2+(σ3−σ1)2=6k2(\sigma_1 - \sigma_2)^2 + (\sigma_2 - \sigma_3)^2 + (\sigma_3 - \sigma_1)^2 = 6k^2(σ1​−σ2​)2+(σ2​−σ3​)2+(σ3​−σ1​)2=6k2

Used to predict yielding under complex stress states.

(f) Types of Dies in Sheet Metal Forming

Simple Die – Single operation per stroke.

Compound Die – Multiple operations at one station.

Progressive Die – Multiple operations at different stations.

Combination Die – Cutting and forming simultaneously.

(g) Gating System in Casting

Components:

Pouring Basin → regulates molten metal flow.

Sprue → vertical passage.

Runner → horizontal channel.

Ingate → entry into mould cavity.

Riser → compensates shrinkage.

(h) Rolling Process

Principle: Compression between rolls reduces thickness.

Max Draft:

• δmax=R(1−cos⁡α)≈Rα22\delta_{max} = R(1 - \cos\alpha) \approx \frac{R\alpha^2}{2}δmax​=R(1−cosα)≈2Rα2​

where α\alphaα = angle of bite, RRR = roll radius.

SECTION – C (2 × 15 = 30 Marks)

Analytical derivations and numerical problems.

Q3. Wire Extrusion with Friction

Given:

σ=Kln⁡DBDa(1+B)\sigma = K \ln\frac{D_B}{D_a} (1 + B)σ=KlnDa​DB​​(1+B)

where
σ\sigmaσ = extrusion stress,
DB,DaD_B, D_aDB​,Da​ = inlet and outlet diameters,
B=μcot⁡αB = \mu \cot \alphaB=μcotα,
μ\muμ = friction coefficient,
α\alphaα = die half-angle,
KKK = material constant (shear yield stress).

Q4. Rolling Defects & Calculation Example

Defects:
Wavy edges, edge cracks, alligatoring, zipper cracks.
Numerical:
Given:

Initial thickness = 15 mm

Final thickness = 12 mm

Roll diameter = 400 mm

α=h1−h2R=3200=0.122 rad≈7°\alpha = \sqrt{\frac{h_1 - h_2}{R}} = \sqrt{\frac{3}{200}} = 0.122 \, \text{rad} \approx 7°α=Rh1​−h2​​​=2003​​=0.122rad≈7° 

Q5. Deep Drawing – Radial Stress

Radial Stress:

• σr=Krln⁡rmr\sigma_r = \frac{K}{r} \ln \frac{r_m}{r}σr​=rK​lnrrm​​

KKK = strength coefficient, rmr_mrm​ = blank radius, rrr = radius under consideration.

Derivation involves equilibrium of annular element under tensile stress.

Summary

The Manufacturing Science-I (EME402) paper assesses understanding of:

Metal forming: rolling, extrusion, forging, drawing

Casting: gating, riser design, allowances

Powder metallurgy & plastics

Sheet metal operations (punching, notching, deep drawing)

Stress-strain analysis in plastic deformation