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

Course: B.Tech (Mechanical Engineering)
Subject Code: NME402
Subject Title: Manufacturing Science & Technology – I
Exam Type: Theory (Semester IV, 2016–17)
Duration: 3 Hours
Maximum Marks: 100

SECTION – A (10 × 2 = 20 Marks)

Short questions testing conceptual fundamentals.

SECTION – B (5 × 10 = 50 Marks)

Medium-length analytical questions combining theory and practical understanding.

(a) Open vs Closed Die Forging

Rolling Defects:

Wavy edges (uneven deformation)

Edge cracks (excessive tensile stress)

Zipper cracks (centerline tension)

Alligatoring (non-uniform flow)

(b) Jigs and Fixtures

Jig: Holds and guides tool (e.g., drill jig).

Fixture: Holds workpiece (e.g., milling fixture).

Types of Jigs: Plate, box, channel, sandwich, and indexing types.

(c) Punching vs Blanking & Force Relation

F=τs×Area=τsπdtF = \tau_s \times \text{Area} = \tau_s \pi d tF=τs​×Area=τs​πdt

If punch face has shear (s):

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

where ddd = diameter, ttt = thickness.
Thus, shear reduces cutting force and tool wear.

(d) Design Considerations in Powder Metallurgy

Uniform pressure distribution during compaction.

Control of particle size, shape, and distribution.

Proper die design and lubrication.

Sintering temperature control to ensure bonding.

(e) Tresca & Von Mises Criteria

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

Von Mises:

• (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 in metals under complex loading.

(f) Types of Dies

Simple Die: One operation per stroke.

Compound Die: Two or more operations at one station.

Progressive Die: Operations at successive stations.

Combination Die: Cutting and forming together.

(g) Gating System

Consists of:

Pouring Basin

Sprue

Runner

Ingate

Riser
Ensures smooth metal flow and minimizes turbulence.

(h) Rolling Process

Principle:
Thickness reduced by compressive forces from rotating rolls.
Maximum 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 RRR = roll radius, α\alphaα = angle of bite.

SECTION – C (2 × 15 = 30 Marks)

Derivation and numerical problems testing applied concepts.

Q3. Wire Extrusion with Friction

Derive:

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

where

DBD_BDB​ = inlet diameter,

DaD_aDa​ = outlet diameter,

μ\muμ = coefficient of friction,

α\alphaα = die half-angle,

B=μcot⁡αB = \mu \cot \alphaB=μcotα,

KKK = shear yield stress.

Q4. Rolling Defects & Calculation

(i) Defects: Wavy edges, edge cracks, alligatoring, zipper cracks.
(ii) Calculation:
Given:
h1=15 mm,h2=12 mm,R=200 mmh_1 = 15 \, \text{mm}, h_2 = 12 \, \text{mm}, R = 200 \, \text{mm}h1​=15mm,h2​=12mm,R=200mm

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. Radial Stress in Deep Drawing

Derivation:

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

where
KKK = strength coefficient, rmr_mrm​ = blank radius, rrr = instantaneous radius.

Summary

This NME402 – Manufacturing Science & Technology I paper comprehensively tests:

Metal forming fundamentals (rolling, extrusion, drawing, forging)

Casting design and allowances

Sheet metal operations (punching, blanking, deep drawing)

Powder metallurgy & plastic deformation theories