Interview Questions for Mechanical Engineers

Mechanical Engineers, both at the entry level and the expertise, often get confused about the level of preparation for the interviews. They are puzzled about the area they must be focusing on while preparing for their interviews.

Here is all that you need to know:

What are the subjects to prepare?

There are many streams in mechanical engineering. They are classified into the following types of which basic level comprises of Engineering Mechanics; Strength Of Materials; Design of Mechanical Elements; Thermodynamics; Heat and Mass Transfer; Fluid Mechanics; Materials and Manufacturing

The modern level comprises of Nanomaterials; Mechanical Measurements; Metrology; IC Engines, Gas turbines, and Jet Propulsion; Automobile Engineering; Production, Planning, and Control; Refrigeration and Air Conditioning; Finite Element Method (FEM); Robotics and many other streams.

It is generally advised to have expert level knowledge in all the basic level courses and mastery in at least one of the modern level courses. The basic level courses are usually considered as fundamentals for every mechanical engineer and the modern level courses give out the area of interest and scope of research.

Things to have complete knowledge of:

Academic level projects and internships are the areas on which interviewee must have complete knowledge. The entire project should be framed into words such that explaining briefly shouldn't take more than a minute. Talking about the roles played during the internship add values to your answer.

The interviewer is basically looking for the knowledge that transformed into a skill. The judgment in this area neither depends upon the company at which the interviewee has interned nor the project he/she has completed. Complete knowledge over the area of experience is what is tested.

Things to have basic knowledge about:

Interviewers expect the interviewees to have basic knowledge about the products and the outputs of the company. So, having basic knowledge about the company, the products manufactured and the services offered would convey interviewee's interest in the company. The interviewee should also have basic knowledge about the latest trends and the future scope of development and research.

The interviewee must also be aware of the top level in the company’s hierarchy. This displays interviewee’s interest in joining the group. 

If the candidate has mentioned about a subject as one of the areas of interest, then the candidate must be self-prepared about all the concepts related to that subject.

Probable Areas of Questions:

Engineering Mechanics

Basic concepts in vectors, kinematics, and kinetics; Concepts related to dynamics (translational and rotational) and theorems
Eg: What is the moment of inertia.?
It is the resistance against angular acceleration.

Strength of materials 

Basic concepts about stresses and strains; types of stresses and strains; Principal stresses and strains; Mohr's Circle; Slopes and deflections; Shear force and Bending moment diagrams; shear center. These are the areas where usually a lot of questions roll out.
Eg: Explain Hooke's law?
The law states that for an elastic body the stress is directly proportional to strain.

Design of Mechanical Elements

Theories of failure; Endurance and Fatigue stresses; Design of nuts, bolts, shafts, power screws. Design of IC Engine components; Design of flexible couplings; Design of Ball and roller bearings; Design of chain drives and belt drives; Design of springs.

Theory of Machines

Kinematics of machine elements; Concepts about Kinematic links and kinematic pairs; Degrees of freedom of kinematic joints; Gears and Powertrains.

Fluid Mechanics and Hydraulic machines

Properties of fluids; kinematics of fluid flow; flow through pipes; Mach number; Drag; Turbines; Impact of Jets; Pumps - rotary and reciprocating.


Laws of thermodynamics; Entropy; Enthalpy; Irreversibility; Rankine Cycle; Thermodynamic relations; Energy Balance; Air standard cycles.
Thermodynamics has a limited number of questions, the questions could be on the above and also on heat rejection; control volume; control surface.

Heat and Mass Transfer

Conductive heat transfer; Lumped systems with internal heat generation; convective heat transfer - natural and forced; Heat Exchangers; Radiation - Black body and grey body.

Materials and manufacturing

Properties of materials; Classification of elements; Iron-Iron Carbide Equilibrium Diagram; Copper and Brass alloys - composition and applications; casting; metal forming; Cold working and hot working processes; machining - Turning, Drilling, Milling; Unconventional machining processes; Tooi parameters and Merchants Circle.
Manufacturing and design have a lion's share in every interview. Mostly questions from Iron-Iron Carbide Equilibrium Diagram are asked as they form a chain of questions and they are important in every sector. Questions from design include mostly power screws, couplings, ball bearings.

General anticipated Questions:

What are the various phases of the design process?

Answer: The various phases of the design process are:
1. Recognition of need.
2. Definition of problem
3. Synthesis
4. Analysis and optimization
5. Evaluation
6. Presentation

Differentiate between repeated stress and reversed stress.

Answer: Repeated stress refers to stress varying from zero to a maximum value of the same nature.
Reversed stress of cyclic stress varies from one value of tension to the same value of compression.

Define stress concentration and stress concentration factor.

Answer: Stress concentration is the increase in local stresses at points of rapid change in cross 
section or discontinuities.
Stress concentration factor is the ratio of maximum stress at the critical section to the nominal stress

What are various theories of failure?

Answer: The failure theories are:
1. Maximum principal stress theory.
2. Maximum shear stress theory.
3. Maximum principal strain theory.

Give some methods of reducing stress concentration.

Answer: Some of the methods are:
1. Avoiding sharp corners.
2. Providing fillets.
3. Use of multiple holes instead of a single hole
4. Undercutting the shoulder parts.

What are principal stress and principal plane?

Answer: A plane which has no shear stress is called principle plane the corresponding stress is called the principal stress.

What causes hardness in steel? How heat treatment alters the properties of steel?

Answer: The shape and distribution of the carbides in the iron determine the hardness of the steel. 
Carbides can be dissolved in austenite is the basis of the heat treatment of steel. If steel is heated 
above the A critical temperature to dissolve all the carbides, and then cooled suitable cooling 
through the cooling range will produce the desired size and distribution of carbides in the ferrite, 
imparting different properties.

What is the difference between isotropic and anisotropic materials?

Answer: If a material exhibits the same mechanical properties regardless of loading direction, it is 
isotropic, e.g., homogeneous cast materials. Materials lacking this property are anisotropic.

What is the amount of carbon present in Cast Iron?

Answer: Carbon is basically present in the form of cementite in cast iron. Its percentage lies in the range of 2.03-6.67% by weight of cementite for Cast Iron. If the amount is less than the above range, then it is stainless steel

Define the Reynolds number.

Answer: Reynolds number is the ratio of inertial force and viscous force. It is a dimensionless 
number. It determines the type of fluid flow.

What is the difference between Pipe and Tube?

Answer: Tube is defined by Outer diameter and Wall thickness (OD and WT). While Pipe is defined by Inner diameter (ID).

Which is hard material Cast Iron or Mild Steel?

Answer: Cast iron. Due to the excess carbon content than mild steel, it is harder. The more the carbon content, the more the hardness will be. But it reduces the Weldability due to this hardness.

Above mentioned are a few questions with answers that can be asked in a technical interview. Apart from these, questions from latest technologies, problems in existing technologies and future scope of technologies are often asked.
There is nothing to panic about if one is not aware of the answer. Here, “Honesty is the best policy”. It works well with a parallel display of learning attitude instead of blurting out wrong answers confidently.

- Dinesh Srinivas


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