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August 5, 2020
Interview Mechanical

Mechanical Engineering Interview Questions Set-2

  1. What is ductile-brittle transition temperature?

Ans. It is the temperature below which the tendency of a material to fracture increases rather than forming. Below this temperature the material loses its ductility. It is also called Nil Ductility Temperature.

 

2. What is a positive displacement pump?

Ans. A positive displacement pump causes a liquid or gas to move by trapping a fixed amount of fluid or gas and then forcing (displacing) that trapped volume into the discharge pipe. Positive displacement pumps can be further classified as either rotary-type (for example the rotary vane) or lobe pumps similar to oil pumps used in car engines. These pumps give a non-pulsating output or displacement unlike the reciprocating pumps. Hence, they are called positive displacement pumps.

 

3. What are the advantages of gear drive?

Ans. In general, gear drive is useful for power transmission between two shafts, which are near to each other (at most at 1m distance). In addition, it has maximum efficiency while transmitting power. It is durable compare to other such as belts chain drives etc. You can change the power to speed ratio.

Advantages: –

It is used to get various speeds in different load conditions.

It increases fuel efficiency.

Increases engine efficiency.

Need less power input when operated manually.

 

4. How pipe flanges are electrically insulated?

Ans. Pipe flanges are protected from corrosion by means of electrolysis, with dielectric flanges. The piping system is electrically insulated by what is called a sacrificial anode. A bag of readily corrodible metal is buried in the ground with a wire running from the pipe to the bag so that the sacrificial anode will corrode first. If any electrical current charges the pipe, it also serves as a ground.

 

5. What is a Process Flow Diagram?

Ans. A Process Flow Diagram (or System Flow Diagram) shows the relationships between the major components in the system. It also has basic information concerning the material balance for the process.

 

6. Where pneumatic system is used?

Ans. Any system needs redundancy in work needs pneumatics, because the compressor of the pneumatic system has periodical operations (intermittent work, not as hydraulic pump). The compressed air could be accumulated in tanks with high pressures and used even if the compressor failed.

 

7. Why gas containers are mostly cylindrical in shape?

Ans. The most efficient shape for withstanding high pressure is a sphere but that would be costly to manufacture. A cylinder with a domed top and a domed bottom (look underneath, the flat base is actually welded around the outside, the bottom of the gas container is actually domed) is a much cheaper shape to manufacture whilst still having good strength to resist the internal gas pressure.

 

8. What is representative elementary volume?

Ans. Smallest volume over which measurements can be made that will yield a representative of the whole.

 

9. How is martensite structure formed in steel?

Ans. Martensite transformation begins when austenite is cooled below a certain critical temperature, called the matrensite start temperature. As we go below the martensite start temperature, more and more martensite forms and complete transformation occurs only at a temperature called martensire finish temperature. Formation of martensite requires that the austenite phase must be cooled rapidly.

 

10. What is an ortographic drawing?

Ans. Orthographic projections are views of a 3D object, showing 3 faces of it. The 3 drawings are aligned so that if the page were folded, it would create part of the shape. It is also called multiview projections.

The 3 faces of an object consist of its plan view, front view and side view. There are 2 types of orthographic projection, which are 1st angle projection and 3rd angle projection.

 

11. Why are LNG pipes curved?

Ans. LNG pipes are curved because LNG is condensed gas (-164 deg cel) so it can expand the pipes that is what engineers designed the LNG pipes are curve type.

 

12. Can you use motor oil in a hydraulic system?

Ans. Hydraulic fluid has to pass a different set of standards than motor oil. Motor oil has tackifiers, lower sulfur content, and other ingredients that could prove harmful to the seals and other components in a hydraulic system. If it is an emergency only should you do it.

 

13. What does angular momentum mean?

Ans. Angular momentum is an expression of an objects mass and rotational speed.

Momentum is the velocity of an object times it is mass, or how fast something is moving how much it weigh. Therefore, angular momentum is the objects mass times the angular velocity where angular velocity is how fast something is rotating expressed in terms like revolutions per minute or radians per second or degrees per second.

 

14. Is it the stress that, produces strain or strain produces stress?

Ans. A Force applied to an object will cause a displacement. Strain is effectively a measure of this displacement (change in length divided by original length).

Stress is the Force applied divided by the area it is applied. (E.g. pounds per square inch)

Therefore, to answer the question, the applied force produces both “Stress and Strain”. “Stress and Strain” are linked together by various material properties such as Poisson’s ratio and Young’s Modulus.

 

15.. What is knurling?

Ans. Knurling is a machining process normally carried our on a centre lathe. The act of Knurling creates a raised criss-cross pattern on a smooth round bar that could be used as a handle or something that requires extra grip.

 

16. Name two vital conditions of a perfect gas.

Ans. Two vital conditions of perfect gas are:

  • It should satisfy the state equation.
  • Specific heat remains constant

 

17. What is the most basic characteristic of supercritical boilers?

Ans. Supercritical boilers do not have a heavy drum to separate steam from water and steam. They also require less steel metal.

 

18. What do you mean by emissive power?

Ans. It is the amount of radiation emitted per unit.

 

19. How Does An Equal-arm Balance Work?

Ans. Two pans of equal balances are placed at the end of the beam, one at each end. A long pointer attached at right angles to the beam at the point of support. Zero on a scale indicates the beam is at rest.

 

20. How Can You Convert Air Mass To Air Volume?

Ans. Air density is p/RT, where R is the gas constant for air (287 J/kg-K), T is the absolute temperature, and p is the pressure, equal to 101325 Pa at sea level.

At sea level and room temperature, the density of air is rho 101325 N/m2/ (287 N-m/ (kg-K)*293 K or about a) 2 kg/mc)

 

21. Which Is Better–a Dc Or An Ac Pump

Ans. Although DC pumps have an advantage over AC pumps in terms of higher efficiency and no requirement of an inverter for operation, the cost of DC pumps is higher. Also, the repair and maintenance of DC pumps are difficult in rural and remote areas due to lack of service centres in these areas.

 

22. How Much Area Can A System Irrigate?

Ans. Generally, it is said that a 2 HP pump can cater to about two acres of land and a 7.5 HP is said to cater to 10 acres of land, but this data vary depending on the groundwater levels and the type of irrigation required for a particular crop.

 

23. During The Drive Torque, What Will Be The Weight Shift?

Ans. In case of cars the torque is applied to the rear wheels, thus limiting accelerator due to front wheel drive due to weight transfer. This drive is bolted to the chassis of the car. Modern manufacturers therefore design rear wheel drive to have similar handling to front wheel drive wherever possible via suspension tuning.

 

24. Is It The Stress That, Produces Strain Or Strain Produces Stress?

Ans. A Force applied to an object will cause a displacement. Strain is effectively a measure of this displacement (change in length divided by original length).

Stress is the Force applied divided by the area it is applied. (E.g. pounds per square inch) Therefore, to answer the question, the applied force produces both “Stress and Strain”. “Stress and Strain” are linked together by various material properties such as Poisson’s ratio and Young’s Modulus.

 

25. How Can I See Where Pipes Are Behind The Wall?

Ans. By using radio waves.

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