About this previous year paper
SECTION A
(2 × 10 = 20 marks | Very Short Answers)
a) Causes of residual stresses
Residual stresses are caused due to non-uniform plastic deformation, thermal gradients during cooling, phase transformation, welding, casting, forging, and machining operations.
b) Modes of heat transfer in welding
Heat transfer in welding occurs by: Conduction (major mode within metal)
Convection (molten pool movement) Radiation (heat loss from surface)
c) Centre-line Feeding Resistance (CFR)
CFR is the resistance offered to molten metal flow along the center line of a casting during solidification, which affects feeding efficiency and shrinkage defects.
d) Advantages of additive manufacturing
Complex geometry possible Reduced material waste
Rapid prototyping Customization
Shorter production time
e) Role of thermoplastic material in P/M injection moulding
Thermoplastics act as binders, providing flowability during injection and holding powder particles together before debinding and sintering.
f) Principles of plastic processing
Plastic processing is based on: Heating to soften
Shaping under pressure Cooling to retain shape
g) Importance of chipless machining in future
Chipless machining reduces material waste, energy consumption, and finishing operations, making it environmentally friendly and cost-effective.
h) Principle of powder metallurgy
Powder metallurgy involves powder production, compaction, and sintering to produce components without melting the material completely.
i) Bio-materials
Bio-materials are materials used in medical applications to replace or support body tissues, such as titanium implants and polymeric prosthetics.
j) Factors affecting suitability of casting
Melting temperature Fluidity
Shrinkage tendency Chemical reactivity
Cost and availability
SECTION B
(Attempt any 3 | 10 marks each)
a) Relation of mathematical modeling with problem solving
Mathematical modeling converts real manufacturing problems into mathematical equations. It helps in prediction, optimization, cost reduction, and understanding process behavior, thus improving decision-making.
b) Orthogonal vs Oblique cutting (Comparison)
| Feature | Orthogonal Cutting | Oblique Cutting |
|---|---|---|
| Cutting edge | Perpendicular | Inclined |
| Chip flow | Straight | Sideways |
| Force analysis | Simple | Complex |
| Practical use | Rare | Common |
c) Solid-state welding and its types
Solid-state welding joins materials without melting.
Types include: Friction welding
Diffusion bonding Ultrasonic welding
Explosive welding Advantages include minimal distortion and high joint strength.
d) Powder metallurgy process
Steps: Powder production
Blending Compaction
Sintering
Applications: gears, bearings, filters
Advantages: high precision, minimal waste, mass production
e) Finishing and packaging in micro/nano manufacturing
Finishing improves surface quality and functionality, while packaging protects devices from moisture, vibration, and contamination, ensuring long-term reliability.
SECTION C
Q3 (Attempt any one)
a) Effect of friction in forging and extrusion
Friction increases energy consumption, tool wear, and heat generation. Controlled friction improves material flow, while excessive friction reduces surface quality and causes defects.
b) Driving forces behind phase transformation
Phase transformations occur due to: Change in temperature
Reduction in free energy Diffusion of atoms
Examples include austenite to martensite transformation during heat treatment.
Q4 (Attempt any one)
a) Tool life calculation
Given:
V = 100 m/min, n = 0.25, C = 300
VTn=CVT^n = CVTn=C 100×T0.25=300100 \times T^{0.25} = 300100×T0.25=300 T0.25=3⇒T=81 minutesT^{0.25} = 3 \Rightarrow T = 81 \text{ minutes}T0.25=3⇒T=81 minutes
b) Importance of parameter identification
Correct identification of parameters improves model accuracy, process optimization, prediction of tool wear, and product quality.
Q5 (Attempt any one)
a) Mechanics of deep drawing
Deep drawing involves pulling sheet metal into a die using a punch.
Key parameters: Blank holder force
Material properties Die radius
Friction Proper control prevents wrinkling and tearing.
b) Heat source modeling in welding
Heat source models (Gaussian, double ellipsoid) help predict temperature distribution, weld penetration, and cooling rates using mathematical equations.
Q6 (Attempt any one)
a) Shrinkage in casting
Shrinkage occurs during solidification and cooling.
Minimization methods: Risers
Chills Directional solidification
b) Powder metallurgy vs traditional manufacturing
Powder metallurgy uses solid-state processing, while traditional methods involve melting. PM offers higher precision and less waste.
Q7 (Attempt any one)
a) Role of microstructure and residual stress evaluation
They help predict strength, fatigue life, distortion, and failure, ensuring better performance of welded and cast components.
b) Micro and nano joining techniques
Laser welding: precise, minimal heat affected zone
Diffusion bonding: high-strength joints
Applications include electronics, MEMS, and biomedical implants.