ICAR AICE-JRF/SRF (PhD) — Agricultural Engineering subjects 38–43 · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersHow farm machines are made: joining, casting, machining, heat treatment and measurement, up to building a prototype.
In the exams: ICAR AICE-JRF/SRF subject 39 (FMPE) Unit 7 Manufacturing Technology; ASRB NET Farm Machinery & Power; machinery fabrication in PRC ABE
ICAR AICE-JRF/SRF (PhD) — Farm Machinery and Power Engineering (subject 39), Unit 7 Manufacturing Technology
Manufacturing processes for farm machine parts at postgraduate depth: heat treatment and hardenability of tillage steels, welding processes and weldability (carbon equivalent, hydrogen cracking), casting design (gating, risering, Chvorinov), press working forces, machining parameters and tool life, jigs and fixtures, and limits and fits.
How our questions for ICAR AICE-JRF/SRF spread across the units of Workshop Technology & Manufacturing. Difficulty: 1 easy, 8 medium, 24 hard.
| MIG and TIG welding and testing of welded joints | 5 | |
| Press working of sheet metal | 4 | |
| Jigs, fixtures and gauges | 4 | |
| Heat treatment of steels | 4 | |
| Casting processes | 3 | |
| Lathe operations | 3 | |
| Drilling, milling and shaping | 3 | |
| Metrology and measurement in the workshop | 3 | |
| Fitting, carpentry and smithy | 1 | |
| Arc and gas welding | 1 | |
| Specification of engineering materials | 1 | |
| Prototype fabrication | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A weld is made at 25 V and 200 A with a travel speed of 5 mm/s. Taking an arc efficiency of 0.8, what is the heat input per unit length?
A. 800 J/mm
Heat input = ηVI/v = 0.8 × 25 × 200 / 5 = 800 J/mm (0.8 kJ/mm). 1000 J/mm ignores efficiency; 4000 J/mm is the arc power ηVI in J/s, not divided by travel speed; 0.8 J/mm is a units slip.
Further reading: Hajra Choudhury, Elements of Workshop Technology
Using the IIW formula, what is the carbon equivalent of a steel with 0.45% C, 0.75% Mn and negligible other alloying elements?
D. 0.575
CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15 = 0.45 + 0.75/6 = 0.45 + 0.125 = 0.575. 0.450 ignores manganese; 1.200 adds manganese at full weight; 0.700 divides manganese by 3. A value this high normally calls for preheat and low-hydrogen practice.
Further reading: IIW carbon-equivalent formula
For a tool–work pair, Taylor's equation is VT^0.25 = 300 (V in m/min, T in min). What tool life is expected at 150 m/min?
D. 16 min
T = (C/V)^(1/n) = (300/150)^4 = 2⁴ = 16 min. 2 min treats life as proportional to the speed ratio; 4 min squares instead of raising to the fourth power; 1.19 min takes the 0.25 power instead of the 4th.
Further reading: Groover, Fundamentals of Modern Manufacturing
In orthogonal cutting with a rake angle of 10°, the uncut chip thickness is 0.5 mm and the chip thickness is 1.25 mm. What is the shear angle?
C. 22.9°
r = 0.5/1.25 = 0.4; tan φ = r cos α/(1 − r sin α) = 0.394/0.931 = 0.423, φ = 22.9°. 21.8° is tan⁻¹ r, ignoring rake; 67.1° is the complement; 32.9° adds the rake angle to the correct answer.
Further reading: Groover, Fundamentals of Modern Manufacturing
Why does down (climb) milling require a backlash eliminator on the table feed screw?
B. The cutter pulls the work in the direction of feed and drags the table forward through any backlash
In climb milling the cutting force has a component in the feed direction, so any slack between screw and nut lets the cutter snatch the table forward, causing chatter or a broken cutter. Lifting the work and a thin starting chip describe up (conventional) milling.
Further reading: Hajra Choudhury, Elements of Workshop Technology
When grinding a hardened tool steel, why is a softer-grade wheel normally preferred?
B. Blunted grains break out readily, exposing sharp new grains instead of glazing
Hard work blunts grains quickly; a softer bond releases them so the wheel self-sharpens and does not glaze and burn the work. Grade does not raise permissible speed, a soft bond holds grains less firmly (faster wear), and any vitrified wheel can be dressed.
Further reading: Hajra Choudhury, Elements of Workshop Technology
A 50.0 mm diameter blank is to be produced by blanking, with a clearance of 0.1 mm per side. What are the die and punch diameters?
C. Die 50.0 mm, punch 49.8 mm
In blanking the blank takes the size of the die opening, so the die is 50.0 mm and the punch is smaller by twice the per-side clearance: 49.8 mm. Die 50.2 / punch 50.0 is the piercing rule (punch = hole). Splitting the clearance gives the wrong blank size; 49.9 uses the clearance only once.
Further reading: Kalpakjian & Schmid, Manufacturing Engineering and Technology
A part is located on two accurately bored holes using two pins. Why is one of the pins made as a diamond (relieved) pin?
C. It allows for centre-distance tolerance while still stopping rotation
Two full round pins would jam if the hole spacing varies within tolerance. The diamond pin is relieved along the line joining the holes, so it only stops rotation about the round pin. It is not about hardness, and foolproofing is a separate design requirement.
Further reading: Hajra Choudhury, Elements of Workshop Technology
A 0.40% carbon steel is cooled slowly to just below 727 °C. Taking the eutectoid at 0.76% C and the carbon content of ferrite as 0.022%, what mass fraction of the structure is pearlite?
D. About 51%
Lever rule: W_pearlite = (0.40 − 0.022)/(0.76 − 0.022) = 0.378/0.738 = 0.512. 53% ignores carbon in ferrite (0.40/0.76); 49% is the proeutectoid ferrite fraction; 40% simply takes the carbon percentage.
Further reading: Callister & Rethwisch, Materials Science and Engineering
Which test is used to measure and compare the hardenability of steels for tillage tools?
B. Jominy end-quench test
In the Jominy test a standard bar is austenitised, water-sprayed on one end, and hardness is measured along its length, showing how deep martensite forms. Charpy measures toughness, Erichsen measures sheet formability, and a single Brinell value gives hardness at one point, not depth.
Further reading: Callister & Rethwisch, Materials Science and Engineering
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