# Top Basic Mechanical Engineering Interview Questions

(Last Updated On: November 11, 2022)

## Top Basic to Advanced Mechanical Engineer Interview Questions

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Mechanical Engineering Interview Questions : Here are the most asked basic to advanced level Mechanical Engineering interview questions and answers for freshers and experienced candidates to get their dream job.

#### 1. What is the difference between a petrol engine and a diesel engine?

Answer : A diesel engine is an IC engine in which the ignition of the fuel occurs due to the high temperature of the air which is mechanically compressed in the cylinders. Petrol engines, however, employ a spark plug for ignition.

#### 2. Can you list at least one utility of a spark plug, apart from its use in a petrol engine?

Answer : Yes, spark plugs can be used to measure ionization in cylinders, especially in Saab Direct Ignition when they are not firing.
This ionic current measurement is used to replace ordinary cam phase sensor, knock sensor and misfire measurement function.

#### 3. How would you define the calorific value of a fuel?

Answer :  The calorific value of a fuel is the amount of heat produced by its combustion—at constant pressure and under “normal” (standard) conditions (i.e. up to 0 °C and a pressure of 1,013 mbar).

#### 4. What does auto-ignition temperature mean?

Answer :  The auto-ignition temperature of a substance is the minimum temperature at which it ignites spontaneously in a standard environment without any external source such as a flame or spark.

#### 5. Can you explain why LMTD is introduced in heat exchanger?

Answer :  LMTD stands for Logarithmic Mean Temperature Difference and is modeled as,
lmTD = {(∆T – t) / ln(∆T/∆t)}, where T and t is equal to the temperature difference between the fluids at both ends of the heat exchanger.

The temperature change occurring in the heat exchanger is not linear – it is exponential. LMTD is also a parameter used to determine the heat transfer rate through the heat exchanger. As the LMTD increases, the heat transfer accelerates.

#### 6.  What is the second law of thermodynamics?

Answer : The second law of thermodynamics states that the total entropy of an isolated system can never decrease with time.

#### 7. What is Ferrite?

Answer : Ferrite is a magnetic iron rock.

#### 8. Which pipes are used for steam lines?

Answer :Steel pipes with welded fittings are used for steam lines.

#### 9.  Distinguish between shear center and elastic center.

Answer : The shear center is a center where the force can act without turning, while the elastic center is located at the center of gravity.

• mechanical engineering interview questions
• mechanical engineering interview questions

#### 10. Name two important conditions of an ideal gas.

Answer : There are two important conditions of a perfect gas:

• It should satisfy the equation of state.
• The specific heat remains constant.

#### 11. What is meant by Greenfield Project?

Answer : These are projects that are built from scratch and do not create pollution.

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### Greenfield project Mechanical Engineering Interview Questions

#### 12.  What do you mean by cotter joint?

Answer : It is one of the types of a joint that are used to connect two rods, which are under compressive or tensile stress. This joint is made of steel or iron. Cotter joint is used for connecting a piston rod to the crosshead of the reciprocating steam engine.

#### 13.  Define pitting.

Answer : It is corrosion that turns to a small hole in the metal.

#### 14. What is the alloy of tin and lead?

Answer : Solder is an alloy of tin and lead. It is primarily used to make electrical joints.

#### 15. What is the importance of tolerance in engineering?

Answer : You cannot design any product without tolerance. It increases the chances of rejection rate and overall product cost. You utilize tolerance in part dimension to reduce cost and facilitate manufacturer.

Freshers Technical Interviews Questions and Answers 2022 – 2023

### Mechanical Engineering Interview Questions for Experienced

Following are the sample questions to be asked from the candidates having mechanical engineering job experience.

1. Can you differentiate between thermodynamics and heat transfer?

Answer: Thermodynamics changes one equilibrium state to another. Heat transfer is a non-equilibrium process.

2. Why is nitrogen used in welding?

Answer: Nitrogen is used in welding to prevent oxygen and air from entering the fused metal while welding.

3. Which gases can be used in place of nitrogen in welding?

Answer: Nitrogen can be replaced with argon, helium and carbon dioxide.

4. Why does a two stroke locomotive engine emit white smoke?

Answer: A two stroke locomotive engine emits white smoke when the engine is running out of fuel.

5. What is a turboprop engine?

Answer: A turboprop engine is a gas turbine engine that is used to power a propeller. It is an efficient engine for aircraft design.

6. How do you differentiate between rocket speed and projectile speed?

Answer: A rocket motion uses a rocket that can accelerate and resist forces such as gravity. Projectile momentum is the force exerted on a body during its launch.

7. What do you understand by handwriting sketch?

Answer: Orthographic drawing is a 3D representation of any object. There are 3 faces: Plan view, Front view and Side view.

8. Can you give us some examples of the mechanisms of our daily life?

Answer: Some examples that show the use of Tantra in our daily life are to turn a clock on or off.

9. Can you expand ABFC?

Answer: The full form of ABFC is Atmospheric Fluidized Bed Combustion.

10. Can you name the characteristics used to identify mild steel, cast iron and high carbon steel?

Answer: While mild steel gives medium and dense sparks, cast iron gives thick and small sparks. Meanwhile, high carbon steel gives longer and thicker spark.

11. Do you know why biological shields are used in nuclear plants?

Answer: The biological shield protects one from exposure to neutron, gamma and beta radiation.

12. Now, can you explain what is a nuclear reactor?

Answer: A nuclear reactor is a plant that controls, maintains and maintains a nuclear fission chain reaction, and thereby prevents exposure to radioactive radiation.

13. Why do you need to subject steel metal to heat treatment?

Answer: Heat treatment steel gives the desired properties to the metal.

14. Do you know why most gas containers are cylindrical?

Answer: Gas containers are made in cylindrical shape to withstand high pressure.

15. Is it possible to use motor oil in hydraulic systems?

Answer: You can use motor oil in hydraulic systems but it is best to avoid it. This is because motor oil contains ingredients that are harmful to seals and other parts of the hydraulic system.

16. Why do airplanes made of thick paper fly for longer distances?

Answer: This is because thicker paper has more mass and potential energy. It turns into kinetic energy when it is in motion and gives a huge lift to the aircraft.

17. What is the mechanical advantage of double pulley?

Answer: A double pulley halves the effort and takes the object twice the distance.

18. How are pneumatic and hydraulic systems similar?

Answer: Both the systems use pressure to act on a particular application. The difference is that pneumatic systems use gases such as air or nitrogen and hydraulic systems use oil or water.

19. What are Newtonian fluids?

Answer: Newtonian fluids are those that have a linear stress-strain relationship curve. It also passes through the origin.

20. Why don’t we use galvanized pipe for steam lines?

Answer: We do not use galvanized pipe for steam lines because the high pressure and temperature of the steam causes the zinc coating on the pipe to wear off.

21. What are the disadvantages of supercritical boilers?

Answer: Supercritical boilers do not have a heavy drum to separate the steam from the water and steam mixture.

22. Can you explain a process flow diagram?

Answer: A process flow diagram describes the elementary flow course. It shows the relationship between major equipment, plant streams and components.

23. What is a universal coupling?

Answer: A universal coupling is a pair of hinges connected by a cross shaft. Shafts are used to connect two shafts to each other with inclined axes.

24. What is Otto Chakra?

Answer: Otto cycle is a thermodynamic combustion cycle. This is how heat engines convert gasoline into motion.

25. Which type of computer program does a mechanical engineer use?

Answer: A Mechanical Engineer uses software like MathCAD, Matlab, Solidworks and Autodesk Inventor

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## Technical Mechanical Engineering Interview Questions to ask Candidates

Interested in testing the technical knowledge of the Mechanical Engineer you are interviewing?

Depending on the industry your company is in, it should be helpful to ask some of the questions listed below.

Explain how hydraulics work on a machine

Hydraulics are used to transmit force from one point to another using an incompressible fluid machines. In most cases, it increases the force applied to one end for a given effort.

What is a Process Flow Diagram?

Commonly used in chemical and process engineering. A process flow diagram (PFD) is a diagram used to indicate the normal flow of equipment and plant processes.

The PFD displays the relationship between the plant facility’s major equipment, but does not show minor details such as designations and piping details.

What is the difference between strut and column?

A column is always vertical but a strut can carry an axial compressive load in any direction. A strut and a pillar both carry the compression load.

What elements do you need to increase the corrosion resistance of steel?

Chromium and nickel.

What are the major components of brass?

Copper and since the major components of brass are copper.

An elastomer is a polymer when its percentage elongation rate is?

More than 100.

Distinguish between fatigue and creep.

Fatigue is the decreased tendency of a material to offer resistance to applied stress under repeated or fluctuating loading conditions.

Creep is the reduced and progressive deformation of a material over time under constant stress at high temperature applications.

What is the second law of thermodynamics?

The second law of thermodynamics states that the total entropy within a closed system will always increase and can never decrease with time.

What is a process flow diagram?

A process flow diagram is a diagram commonly used in chemical and process engineering to indicate the normal flow of plant processes and equipment.

Explain mechanical refrigeration

Using an artificial heat exchange system Mechanical refrigeration is a process where hot is removed from a chosen location.

This refrigeration system can be thermoelectric, magnetic, non-cyclic, cyclic, and will depend on the required refrigeration application.

Describe the difference between a tube and a pipe

Pipes are always round whereas tubes can come in various shapes such as rectangular, square, or cylindrical.

A pressing force is uniformly distributed due to the circular shape of a pipe.

The outer diameter (OD) and wall thickness (WT) are used to measure a tube.

Explain what is effect?

Bearings Precision-made components that enable machinery to run at high speeds while reducing friction between moving parts.

What is P&ID?

A P&ID is a piping and instrumentation diagram used in the process industry. This diagram shows the process equipment and piping in detail, along with control devices and instrumentation.

Explain what is GD&T

GD&T stands for Geometrical Dimensions and Tolerances which is a system for defining and communicating engineering tolerances

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