About this previous year paper
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.
| No. | Question | Explanation |
|---|---|---|
| (a) | Classify Manufacturing Processes | Primary (casting, forming), secondary (machining, joining), and tertiary (finishing, inspection). |
| (b) | Recrystallization | Process where new strain-free grains form in cold-worked metal upon heating. |
| (c) | Forgeability | Ease with which a metal can be deformed plastically without fracture. |
| (d) | Plane Stress vs Plane Strain | Plane stress: σz = 0 (thin sheets); Plane strain: εz = 0 (thick plates). |
| (e) | Angle of Bite & Neutral Plane in Rolling | Angle of Bite = contact angle between rolls and metal; Neutral Plane = point where velocity of roll = velocity of metal. |
| (f) | Pattern Allowances | Shrinkage, draft, machining, distortion, rapping allowances. |
| (g) | Notching & Nibbling | Notching = cutting metal from edges; Nibbling = contour cutting by successive notches. |
| (h) | Curing in Plastics | Cross-linking process converting soft plastic into rigid form under heat/pressure. |
| (i) | Steps in Casting | Pattern making → Mould preparation → Melting → Pouring → Solidification → Fettling. |
| (j) | Hot vs Cold Working | Hot working above recrystallization temp; cold working below it → increases strength. |
SECTION – B (5 × 10 = 50 Marks)
Medium-length descriptive and numerical questions.
(a) Open vs Closed Die Forging & Rolling Defects
| Aspect | Open-Die Forging | Closed-Die Forging |
|---|---|---|
| Material Flow | Unrestricted | Confined in die cavity |
| Accuracy | Low | High |
| Cost | Low | High (due to die) |
Rolling Defects:
Wavy Edges: Uneven thickness
Zipper Cracks: Due to center tension
Edge Cracks: Excessive deformation
Alligatoring: Non-uniform flow
(b) Jigs and Fixtures
| Tool | Function |
|---|---|
| Jig | Guides cutting tool (e.g., drilling jig). |
| Fixture | Holds workpiece securely (e.g., milling fixture). |
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=τsπdt
For shear on punch face:
- F=τsπdt1+stF = \frac{\tau_s \pi d t}{1 + \frac{s}{t}}F=1+tsτsπdt
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−cosα)≈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=KlnDBDa(1+B)\sigma = K \ln\frac{D_B}{D_a} (1 + B)σ=KlnDaDB(1+B)
where
σ\sigmaσ = extrusion stress,
DB,DaD_B, D_aDB,Da = inlet and outlet diameters,
B=μcotαB = \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=Krlnrmr\sigma_r = \frac{K}{r} \ln \frac{r_m}{r}σr=rKlnrrm
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