Quiz: Mechanical Engineering 16 June 2020

Quiz: Mechanical Engineering
Exam: ISRO (TECHNICAL ASST.)
Topic: Miscellaneous

Each question carries 4 mark.
Negative marking: 1 mark
Time: 15 Minute

Q1. Permanent deformation of solid material under the influence of long-term exposure of high level of mechanical stresses that are still below the yield strength along with subjected to heat is……..
(a) Elasticity
(b) Isotropy
(c) Hardness
(d) Creep

Q2. The weld bead between a heavy steel section and a thin section occurs mainly due to the formation of:
(a) Bainite
(b) Spheroidite
(c) Martensite
(d) None of these

Q3. A solid and a liquid result in a liquid upon heating during _________ reaction.
(a) Eutectic
(b) Peritectic
(c) Monotectic
(d) Syntectic

Q4. Titanium in the steel improves the
(a) hardness
(b) strength
(c) resistance to corrosion of steel
(d) strength and resistance to corrosion of steel

Q5. In the casting, ‘’Bell’’ shape products are generally made by
(a) Single piece pattern
(b) Gated pattern
(c) Cope and drag pattern
(d) Sweep pattern

Q6. In straight polarity welding-
(a) electrode holder is connected to the negative and the work to positive lead
(b) electrode holder is connected to the positive and the work to negative lead
(c) electrode holder to be earthed and work to positive head
(d) electrode holder is connected to the negative lead and the work to be earthed

Q7. The value of side rake angle of the turning tool having tool signature:
0°,10°,8°,6°,20°,60°,0.01(mm) will be:
(a) 60°
(b) 20°
(c) 10°
(d) 8°

Q8. No liquid can exist as a liquid at
(a) 0 Deg C temperature
(b) 200 Deg C temperature
(c) Zero pressure
(d) Zero viscosity

Q9. A shock wave is produced when
(a) a sonic flow changes to supersonic flow
(b) a subsonic flow changes to sonic flow
(c) a supersonic flow changes to subsonic flow
(d) none of these

Q10. Consider the following statements regarding the ends of the pressure vessels flanged by pre-tensioned bolts:
1. Pre-tensioning helps to seal the pressure vessel.
2. Pre-tensioning reduces the maximum tensile stress in the bolts
3. Pre-tensioning increases the fatigue life of the bolts.
Which of the above statements are correct?
(a) 1 and 2
(b) 2 and 3
(c) 1 and 3
(d) 1,2 and 3

Solutions

S1. Ans (d)
Sol. Permanent deformation of solid material under the influence of long-term exposure of high level of mechanical stresses that are still below the yield strength along with subjected to heat is known as creep.

S2. Ans (a)
Sol. The weld bead between a heavy steel section and a thin section occurs mainly due to the formation of bainite.
Bainite is formed by isothermal decomposition of Austenite in alloy steels.

S3. Ans (c)
Sol. A solid and a liquid result in a liquid after heating during monotectic reaction.
i.e. Solid 1 + Liquid 1⇌Liquid 2

S4. Ans (d)
Sol. Titanium in the steel improves following properties-
1.Strength
2.Corrosion resistance

S5. Ans (d)
Sol. Sweep pattern is used for the casting of ‘’Bell’’ shaped or 3D symmetrical object.

S6. Ans (a)
Sol. In straight polarity welding, electrode is made negative and work-piece is made positive. Straight polarity welding increases penetration in welding.

S7. Ans (c)
Sol. We know that American standard association (ASA) tool signature has following sequence.
1.Back rake angle- 0°
2.Side rake angle- 10°
3.End relief angle- 8°
4.Side relief angle- 6°
5.End cutting edge angle- 20°
6.Side cutting edge angle- 60°
7.Nose radius- 0.01 mm

S8. Ans (c)
Sol. No liquid can exist as a liquid at zero pressure because at zero pressure, molecular momentum of the liquid becomes very high and if liquid taken to zero pressure which effectively means vacuum, in that case, it will boil and vaporize.

S9. Ans (c)
Sol. A shock wave is a type of propagating disturbance that moves faster than the local speed of sound in a medium. Shock wave is produced when a supersonic flow changes to subsonic flow.

S10. Ans (c)
Sol. Pre-tensioning increases fatigue life of the bolt, maximum tensile stress in the bolt and helps to seal the pressure vessel.

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