## Technical Interview Questions & Answers | Technical Interview Questions & Tips | Strength Of Materials Interview Questions

• ##### Which type of shaft is preferred for power transmission,solid or hollow one?

Hollow shaft utilize material strength more efficiently, so hollow shaft used if you concerned about weight.
But, when weight is not a concern, solid shaft is better (stronger, of course), easy to fabricate.

• Compared to the life of a spark plug of two stroke engine to the spark plug of four stroke engine is approximately
1. Same
2. Twice
3. One-half
4. One-quarter

Twice

• ##### What is structurally stronger, solid steel or hollow steel?

If a solid and hollow shape have the same outside dimensions, the solid one is clearly stronger.
The reason you see so many hollow sections is that they have an incredibly higher strength/weight ratio and can resist the same load with much less material used.

• ##### What will be the difference in torsional strength of hollow shaft & solid shaft of same outer diameter at equal load.

Compare the polar moment of inertia of the solid cross section to the hollow cross section. You’ll find that the difference between the two is equal to the polar moment of inertia of the portion removed from the hollow section.

The deflection of the shaft under a torsional load would be the product of the torsional load and the length of the shaft divided by the product of Polar Moment of inertia and modulus of rigidity of the shaft: theta=TL/JG.

• The principle of a radiator of an engine cooling system is to
1. Act as a reservoir for the water
2. Cause a heat flow by convection currents
3. Spread out the hot water over a larger area
4. Increase the air speed as it flows over the hot surface

Spread out the hot water over a larger area

• ##### What are the units for Poisson’s ratio?

It is a unit less quantity. Because it is one quantity divided by another quantity of the same units.
In fact, even the parent quantities that define Poisson’s ratio are unit less. Strain has no units.

• ##### What is the difference between Stress and Pressure?

Stress=Resistive force/Area.

Pressure=Force/Area.

Stress is pull force and Pressure is push force.

• ##### 2.Material OHNS Stands for

HRC Stands for –Rockwell Hardness C scale

OHNS Stands for — Oil Hardenable Non Shrinkage steel

• ##### Function of Fly wheel

Flywheel stores the Kinetic Energy during the idle portion of the work cycle,and delivers this Kinetic Energy during peak-load.

• ##### Bullet Proof Glass is made up of which material?

Bulletproof glass is usually constructed using a strong but transparent material such as polycarbonate thermoplastic or by using layers of laminated glass. The desired result is a material with an appearance and light-transmitting behavior of standard glass but offers varying degrees of protection from small arms fire. The polycarbonate layer, usually consisting of products  such as Cyrolon, Lexan and Tuffak, is often sandwiched between layers of regular glass. The use of plastic in the laminate provides impact-resistance, such as physical assault with a hammer, an axe, etc. The plastic provides little in the way of bullet-resistance. The glass, which is much harder than plastic, flattens the bullet and thereby prevents penetration. This type of bullet-resistant glass is usually 70-75 mm thick.

• ##### Difference between Performance and Efficiency?

Performance is the measure of quality of the work done by any machine. better  the quality better will be the performance of that machine. while efficiency is the ratio of desired output to the required input for any machine.

Performance is about the quality that a machine or plant is producing suppose there are two machines, first produces the job of accuracy .002mm and the second one produce product of the accuracy .001mm. then the second one will have higher performance.  while efficiency is the ratio of the o/p to the i/p. if same machines are producing 200 and 100 product per day respectively for the same i/p,then the eff. of the first machine will be high.

• ##### What are the causes of main engine black smoke?

There is many cause of black smoke.

1. It’s improper mixture of fuel supply by carburetor like very rich mixture so the fuel improper burn.

2. It’s when piston or piston ring is fail so back side cooling oil release in combustion chamber it cause black smoke.

3. Improper ignition system like not sufficient time of pressure rise delay period .