Mechanical Engineering job Interview Questions with Answers on MD, SOM, KOM, MP, EM & MV

Here are few mostly asked Mechanical Engineering Job Interview Questions With Answers On Mechanical Design, Strength Of Materials, Kinematics Of Machine, Manufacturing Process, Engineering Mechanics & Mechanical Vibrations.

Mechanical Engineering Job Interview Questions With Answers

Question No. 01

What is mechanical engineering?

Answer: Mechanical engineering is the discipline that combines the principles of engineering, physics and materials science for the design, analysis, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the design, production, and operation of machinery and tools.

Technology shows various methods of Engineering. A bridge can be made by using beams to bear the load, by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is laws of force/load distribution.

Question No. 02

What is the difference between Technology and Engineering?

Answer: Engineering is application of science

Question No. 03

What is the difference between Speed and Economic Speed?

Answer: The rated speed tells us about the maximum speed which can be achieved by a vehicle or some other machine but the economical speed means the speed limit at which the machine works efficiently with least consumption of fuel. e.g. in normal bikes(not racing),the maximum speed limit shown on speedometer is up to 120 kmph but companies always advice their customers to drive such bikes at around 60 kmph to have maximum mileage.

Question No. 04

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

Answer: The shape and distribution of the carbides in the iron determines 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.

Question No. 05

What is the difference between isotropic and anisotropic materials?

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

Question No. 06

What are orthotropic materials?

Answer: It is a special class of anisotropic materials which can be described by giving their properties in three perpendicular directions e.g. wood; composites.

Question No. 07

What is view factor?

Answer: View factor is dependent upon geometry of the two surfaces exchanging radiation.

Question No. 08

Explain difference between fissile and fertile materials.

Answer: The materials which can give nuclear fission e.g. U 35, Pu 39, U 33 are fissile materials. Fertile material itself is not fissionable, but it can be converted to a fissionable material by irradiation of neutrons in a nuclear reactor.

Question No. 09

Mention two types of dislocations.

Answer: Dislocation refers to a break in the continuity of the lattice. In edge dislocation, one plane of atoms gets squeezed out. In screw dislocation the lattice atoms move from their regular ideal positions.

Question No. 10

What is Powder Technology?

Answer: Powder technology is one of the ways of making bearing material. In this method metals like bronze, Al, Fe are mixed and compressed to make an alloy.

Question No. 11

What are the principal constituents of brass?

Answer: Principal constituents of brass are copper and zinc.

Question No. 12

What is Curie point?

Answer: Curie point is the temperature at which ferromagnetic materials can no longer be magnetized by outside forces.

Question No. 13

By which instruments the shear stress in fluids can be measured directly?

Answer: By Stanton tube or Preston tube.

Question No. 14

Explain the difference between the points of inflexion and contra-flexure.

Answer: At points of inflexion in a loaded beam the bending moment is zero and at points of contra- flexure in loaded beam the bending moment changes sign from increasing to decreasing.

Question No. 15

What is the difference between proof resilience and modulus of resilience?

Answer: Proof resilience is the maximum strain energy that can be stored in a material without

permanent deformation. Modulus of resilience is the maximum strain energy stored in a material per unit volume.

Question No. 16

What do you understand by critical points in iron, iron-carbide diagram? Answer:

The temperatures at which the phase changes occur are called critical points (or temperatures).

Question No. 17

Define buckling factor.

Answer: It is the ratio of the equivalent length of column to the minimum radius of gyration.

Question No. 18

State the difference between Anti Friction Bearing and Journal Bearing.

Answer: Generally, journal bearings have higher friction force, consume higher energy and release more heat, but they have larger contact surface, so normally used in low-speed high load applications. In anti-friction bearings friction is less. One object just rolls over each other.

Question No. 19

How to Find, Ductile-Brittle Transition Temperature in Metals?

Answer: The point at which the fracture energy passes below a pre-determined point for a standard Impact tests. DBTT is important since, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming.

Question No. 20

What is the difference between P-11 and P-12 Pipes?

Answer: P-11 the chromium molybdenum composition that is 1% of chromium and 1/4% of molybdenum P-12 the chromium molybdenum composition that is 1% of chromium and 2% of molybdenum.

Question No. 21

State the difference between Unilateral and Bilateral Tolerance?

Answer: A unilateral tolerance is tolerance in which variation is permitted only in one direction from the specified direction. e.g., 1800 +0.000/-0.060. Bilateral tolerance is tolerance in which variation is permitted in both directions from the specified direction. e.g., 1800 +0.060/-0.060

Question No. 22

What is the abbreviation of welding rod 7018?

Answer: 7018 is equal to

  • 70 = tensile strength
  • 70000 psi 1= welding position
  • 8 = current flux

Question No. 23

What is difference between Welding and Brazing?

Answer: In Welding concentrated heat (high temperature) is applied at the joint of metal and fuse together. In Brazing involves significantly lower temperatures and does not entail the melting of base metals. Instead, a filler metal is melted and forced to flow into the joint through capillary action.

Question No. 24

How to calculate bearing number from shaft Diameter?

Answer: Divide the shaft diameter size by 5, it will give last two digits of the bearing no. and according to type of load we have to choose the type of bearing and that will give prior number  of the bearing.

Question No. 25

Explain Bicycle Rear Wheel Sprocket working?

Answer: Rear wheel sprocket works under the principle of ratchet and pawl.

Question No. 26

The Fatigue life of a part can be improved by?

Answer: Improving the surface finish by Polishing & providing residual stress by Shot peening.

Question No. 27

Poisson’s Ratio is higher in Rubber, Steel or Wood?

Answer: When a material is compressed in one direction, it usually tends to expand in the other two directions perpendicular to the direction of compression. This phenomenon is called the Poisson effect. Poisson’s ratio is a measure of the Poisson effect.

For rubber = 0.5

For steel = 0.288 For wood < 0.2

Thus, Poisson’s ratio is higher in RUBBER.

Question No. 28

What is the other name of Micrometer & Vernier Caliper?

Answer: Micrometer’s other name is Screw Gauze & Vernier caliper’s other name is slide caliper.

Question No. 29

What is the need for drafting?

Answer: Drafting is the allowances give to casting process. It also used to remove the casting from mold without damage of corners.

Question No. 30

What is the difference between BSP thread and BSW thread?

Answer: The British Standard Pipe thread (BSP thread) is a family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. British Standard Whitworth (BSW) is one of a number of imperial unit based screw thread standards which use the same bolt heads and nut hexagonal sizes.

Interview Questions With Answers for Mechanical Engineering:

Question No. 31

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 than it is stainless steel

Question No. 32

What are the loads considered when designing the Nut and Bolts?

Answer: Shear Loads & crushing loads

Question No. 33

What is the difference between a Fence and a Wall?

Answer: A fence is either more temporary or constructed from materials, other than concrete, stone or brick.

Question No. 34

What is the Difference between Quantitative and Qualitative Research?

Answer: Quantitative research involves gathering data that is absolute, such as numerical data, so that i t can be examined in as unbiased a manner as possible. Qualitative research may yield stories, or pictures, or descriptions of feelings and emotions. The interpretations given by research subjects are given weight in qualitative research, so there  is no seeking to limit their bias. At the same time, researchers tend to become more emotionally attached to qualitative research, and so their own bias may also play heavily into the results.

Question No. 35

What is Bending moment?

Answer: When a moment is applied to bend an element, a bending moment exists in the element.

Question No. 36

What are the points in the Stress Strain curve for Steel?

Answer: Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.

Question No. 37

Define 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.

Question No. 38

How many Joules is 1 BTU? What is PS?

Answer: 1 BTU is equal to 1055.056 joules. PS is Pferdestarke, the German unit for Horsepower.

Question No. 39

Explain the nomenclature of a 6203-ZZ bearing.

Answer: 6 is the type code, which shows it is a single-row ball bearing, 2 is the series, means light, 03 is the bore, which is 17 mm and ZZ is the suffix meaning double shielded bearing.

Question No. 40

What is Gear ratio?

Answer: It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

mechanical engineering interview questions

Question No. 41

What is Annealing?

Answer: It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

Question No. 42

Define Torque.

Answer: Torque is defined as a force applied to an object those results in rotational motion.

Question No. 43

What is Ductile-Brittle Transition Temperature?

Answer: 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.

Question No. 44

What is Auto Dosing?

Answer: Auto dosing is an automated system of feeding the equipment with liquid products. It is the ideal way to ensure the correct calibrated dose at the right time every time in auto.

Question No. 45

Difference between Codes, Standards and Specifications.

Answer:

  • Code is procedure  of acceptance and rejection criteria.
  • Standard  is accepted values and compare other  with it.
  • Specification is describing properties of any type of materials.

Question No. 46

Which is heavier 1kg of Iron or 1kg of Cotton? And why?

Answer: Both of them have same weight. The only difference is the volume of Iron is small compared to Cotton.

Question No. 47

What is the difference between Pipe and Tube?

Answer: Ex. Iron Pipe, Carbon Tube, Steel Tube etc.

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

Example: 2 Inch pipe have 2.375 inch outer diameter, where 2 inch tube have same 2 inch outer diameter.

  • Tube is easily shaped by bending, where Pipe needs some mechanical work to shape it.
  • Tube is tight then Pipe.
  • Tube is applicable to non cylindrical sections like Square and Rectangular.

Question No. 48

How does Welding damage Eye sight?

Answer: An Electric welding arc produces Ultraviolet light and the UV light (Sun burn) will damage the retina. Welding shields or Goggles with the proper shade (Automatic shading) of lens is the best protection for welders. Light filtering curtains and reduced reflective surfaces help protect both welders and observers in the area.

Question No. 49

Explain why BCC, FCC and CPH lattice packing and features of grain structure affect the Ductility and Brittleness of parent metallic materials?

Answer: Ductility is the mechanical property of a material. (It is the material’s ability to deform under the tensile stress without fracture). So, it is depends on the atoms how they arranged in a lattice and its grain size. The ability to absorb the energy of the impact and fracture resistance depends on the arrangement of the atoms in a lattice and features of grain structure.

Question No. 50

Why do you have Truss Bridges?

Answer: Truss bridges carry load in tension and compression rather than bending (Self weight + the weight of vehicles crossing it + Wind loads). A truss has the ability to dissipate a load through the truss work. The beams are usually arranged in a repeated triangular pattern, since a triangle cannot be distorted by stress.

Question No. 51

Why I-section beam is preferred for heavy loading?

Answer: Cross sectional shape I, giving many benefits. It is very good for giving stiffness (less deformation on loading) and to withstand higher bending moments (as a result of heavy loading) on comparison with other cross-sectional shapes of same area. Also, it is very easy to manufacture. It will have more moment of inertia.

Question No. 52

What is difference between Center of Mass and Center of Gravity?

Answer: Both terms are same when gravity is uniform. When gravity is non-uniform following are the terms:

  • The centre of mass is a point that acts as if all the mass was centered there (the mass on one side of the point is equal to the mass on the opposite side). If supported at the centre of mass, an object will be balanced under the influence of gravity.
  • The centre of gravity is the point at which where the sum (vector) of the gravitational forces act on an object which will be balanced on that point.

Question No. 53

What are the differences between Weight and Mass?

Answer: Mass is a measure of how much matter an object has. Mass is specified in Gram or Kilograms. Weight is a measure of how strongly gravity pulls on that matter. Force is measured in Newton’s.

F=m.g

Thus, if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.

Question No. 54

What is the difference between Projectile motion and a Rocket motion?

Answer: A projectile has no motor/rocket on it, so all of its momentum is given to it as it is launched. An example of a projectile would be pen that you throw across a room. A rocket or missile does have a motor/rocket on it so it can accelerate itself while moving and so resist other forces such as gravity. In mechanics point of view projectile don’t have any particular shape it is a point mass. Whereas rocket has a particular shape and hence it has centre of gravity situated at particular point on its body. Therefore, rocket motion comes under kinetics and projectile comes under kinematics.

Question No. 55

What type of cooling used in High Voltage Transformer?

Answer: The big transformers you find on power poles usually use oil as a dielectric insulator, in smaller HV transformers, like the ones in TV’s are usually filled with resin.

Question No. 56

What is honing of Cylinder Liners?

Answer: The honing equipment used has been manufactured by “Chris Marine”. The head of the honing device consists of four synchronized stones. For the initial honing diamond stones are used to break up the hardened surface in the scuffed areas. For the main honing very coarse and hard stones are used to produce a very desirable rough surface all over the liner. The advantage, especially for the 2-stroke engines, is possibility to save the liner after a seizure, scuffing or blow-by or even to eliminate the ovality of the liner. Another advantage is that it is possible to machine a rough liner wall to obtain a well oiled surface.

Question No. 57

What is the difference between Speed and Velocity?

Answer: Speed is scalar quantity and Velocity is a vector. Velocity has both speed and direction. Speed is expressed as distance moved  (d) per  unit of time (t). Speed is measured in the same physical units of measurement as velocity, but does not contain an element of direction. Speed is thus the magnitude component of velocity.

Question No. 58

Difference between Yield Stress and Yield Strength?

Answer: Stress is a measure of the load applied to a sample relative to a cross sectional area of the sample. Strength is a quantification of the samples ability to carry a load.

The terms “yield strength” and “yield stress” of a material are usually used interchangeably (correct or not). It is the stress which will just cause the material to plastically deform. If a material yields at 30,000 psi, the yield stress is 30,000 psi. If the part in question has a cross sectional area of 2 square inches, the strength at yield would be 60,000 pounds, but usually we just say the yield strength is 30,000 psi.

Question No. 59

What is the difference between Yield and Ultimate tensile strength?

Answer: The yield strength is reached when the material becomes Non – linear (that is non elastic) and takes a permanent set when load is released. Material stretches but does not break. Ultimate strength is when it breaks and is higher than yield strength.

Question No. 60

What is the difference between Flexural strength and Tensile strength?

Answer: Flexural strength is resistance offered against bending. Tensile strength is resistance offered against tensile force.

mechanical engineering interview questions and answers book

Question No. 61

What is the difference between Shear and Tensile strength?

Answer: Tensile Strength for a Bolt is determined by applying a Force along it long axis. Shear Strength for a Bolt is determined by applying a Force across its diameter, as it would be loaded in a lug joint. Tensile strength is strength in tension when pulling force is applied. And shear strength is strength against cutting force which is known as shear force.

Question No. 62

What is the difference between Tensile strength and tensile modulus?

Answer: Tensile strength is the ultimate capacity of the material to resist a tensile load regardless of deflection.

Tensile modulus also known as Young’s modulus is a measure of the stiffness of an isotropic elastic material. It is defined as the ratio of the uni-axial stress over the uni-axial strain. It is determined from the slope of a stress-strain curve traced during tensile tests conducted on a sample of the material.

Question No. 63

What is OEE?

Answer: OEE means Overall Equipment Effectiveness. This terminology widely used in Total productive maintenance, which is used to calculate the effectiveness of machines in manufacturing. Basically, it captures the losses of machines in production and tries to improve defects on machines. Higher the OEE, more capable is the machine.

Question No. 64

Why Involutes Curve used in Gear?

Answer: Involute curve is the path traced by a point on a line as the line rolls without slipping on the circumference of a circle. Involute curve has a contact angle between two gears when the tangents of two gears pass through the contact point without friction.

Question No. 65

What is bearing stress?

Answer: The stress which acts on the contact surface area between two members is known as bearing stress. An example for this is the stress between nut and the washer

Question No. 66

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 carbon content, the more hardness will be. But it reduces  the Weldability due  to this  hardness. It is brittle too.

Question No. 67

What are the materials used for Sliding Wear pad?

Answer:

  • Urethane-Coated Base Material Provides Optimum Sliding Surfaces for Maximum Wear Ability.
  • Galvanized Steel for Backing on Head and Side Pads.
  • For crane services, we use Velcro Nylon wearing pad

Question No. 68

What is the difference between a Shaper machine and a Planner machine?

Answer: In Shaper machine tool is having reciprocating motion and work piece is clamped on table which is stationary. It is mostly suitable for light duty operation. In Shaping large cutting force is transferred to tool. In Planer machine tool is having stationary and work piece is clamped on table which is reciprocating motion. It is mostly suitable for Heavy duty operation. In planner large cutting force is transferred to table.

Question No. 69

How will you calculate the tonnage of Mechanical Press?

Answer:

  • F = (S × L × T)/ 1000
  • F = Force in kilo Newton’s
  • S = shear stress of material in MPa
  • L = the total length of peripheries being cut/ sheared in mm T = thickness of material in mm

Question No. 70

What is the composition of Grey cast iron Grade 20?

Answer: Carbon: 3.10 – 3.25%, Silicon: 1.75 – 1.95%, Manganese: 0.50 – 0.7%, Sulphur: 0.05 – 0.07%, Phosphorous: 0.04 – 0.07%

Question No. 71

What is the composition of Cast iron Grade 35?

Answer: Carbon=2.90 – 3.10%, Manganese=0.60 – 1.00%, Silicon=1.50 – 1.90%, Sulphur=0.10%, Phosphorus=0.15%, Chromium=0.30%, Molybdenum=0.30%, Cupper=0.25%

Question No. 72

What are the super alloys?

Answer: Super alloys are an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, having good surface finish.

Question No. 73

Why the Super alloys used for land based turbines?

Answer: Super alloys are the top most alloys used for their excellent strength and corrosion resistance as well as oxidation resistance. No other alloys can compete with these grades.

Question No. 74

What kinds of NDT methods are available?

Answer:

  1. Visual Inspection
  2. Microscopy inspection
  3. Radiography Test
  4. Dye Penetrate technique
  5. Ultrasonic testing
  6. Magnetic Particle inspection
  7. Eddy Current technology
  8. Acoustic Emission
  9. Thermograph
  10. Replica Metallographic

Question No. 75

What is Stress Corrosion cracking?

Answer: Stress corrosion cracking (SCC) is a process involving the initiation of cracks and their propagation, possibly up to complete failure of a component, due to the combined action of tensile mechanical loading and a corrosive medium.

Question No. 76

What is meant by D2 Material used for Die tooling?

Answer: D2 – High Carbon Cold Work Tool Steel.

D2 is a high Carbon, high Chromium, Molybdenum, Vanadium, Air hardening alloy tool steel which offers good wear resistance, high surface hardness, through hardening properties, dimensional stability and high resistance to tempering effect. D2 tool steel is also suitable for vacuum hardening.

Typical Composition: C. = 1.50%, Si. = 0.30%, Cr. = 12.00%, Mo. = 0.80%, V. = 0.90%

Question No. 77

What is Vacuum Induction Melting?

Answer: As the name suggests, the process involves melting of a metal under vacuum conditions. Electromagnetic induction is used as the energy source for melting the metal. Induction melting works by inducing electrical eddy currents in the metal. The source is the induction coil which carries an alternating current. The eddy currents heat and eventually melt the charge.

Question No. 78

What is the difference between Bolt and Screw?

Answer: The main difference was based on the load acting on it, and the size. For smaller loads, screws are enough but in case of greater-loads, bolts are to be used. In bolt we give centrifugal force or tangential force and screw we give axial force for driving.

Question No. 79

What is the function of a thrust bearing?

Answer: Thrust bearings keep the rotor in its correct axial position.

Question No. 80

What is the significance of Torque (in N-m) given in the engine specification?

Answer: It give the moment about any point or simple rotation.

Question No. 81

What are the uses of Graphite electrode in various fields?

Answer: Graphite electrode is used in EDM and in battery cells. It is also used in electric arc furnaces to melt the steel.

Question No. 82

Difference between TIG & MIG welding

Answer: TIG – Tungsten inert gas welding-non consumable electrode MIG – Metal inert gas welding-uses consumable electrode

Question No. 83

Do you know epicyclic gear box? What is the practical application of epicyclic gear box?

Answer: Epicyclic gear box consists of sun gear planetary gears and an annular called ring gear. Different speed ratios are obtained by locking any one gear. If you lock any two gears, direct gear will be obtained. Mostly used in over drives. Wrist watch is a practical application of epicyclic gear box

Question No. 84

What is the purpose of scrapper ring?

Answer: Scrap the excess lube oil from the cylinder walls. There by preventing oil from entering combustion zone.

Question No. 85

What is the difference between S.S to EN8?

Answer: SS- Stainless steel. En- Medium carbon steel. SS is Non Magnetic material & EN8 is Magnetic material SS is Corrosion resistant & EN8 is Magnetic material

Question No. 86

How to calculate the speed of conveyor in Meter per Minute

Answer: Measure the diameter of the rollers around which the conveyor belt is wrapped. Multiply the diameter of the roller by pi (3.14159). This calculation will yield the circumference of the rollers. Every time the roller spins one revolution, the conveyor will be moved a linear distance equivalent to the circumference of the roller. Pi is a dimensionless factor, meaning it does not matter whether inches, centimeters or any other units of measurement are used.

Measure the revolutions per minute (RPM) of the rollers. Count how many full revolutions (rotations) are made by the roller in one minute. Multiply the RPM by the circumference of the roller. This calculation will give the linear distance traversed by a point on the conveyor belt in one minute.

Question No. 87

What is the use of a PULLEY?

Answer: Transmission of power (force) in rotary form

Question No. 88

Why does cycle rim don’t bend even in heavy loads?

Answer: Because of rubber tires. The load is distributed and its effect reduces i.e. tires absorbs heavy load and shocks with the support of steel rim. The rim has many spokes. The spokes distribute the load equally and the rubber tires absorb more than half of the load.

Question No. 89

What is caustic embrittlement?

Answer: It is the actual physical change in metal that makes it extremely brittle and filled with minute cracks. It occurs particularly in the seams of riveted joints and around the rivet holes .

Question No. 90

What type of section of same area will resist maximum bending moment, I section, rectangular or circular section?

Answer: I- section of same area resist more bending moment than a rectangular or circular section. The reason is obvious. In i-section larger area is concentrated at larger distance from neutral axis and hence stressed more. In circular section, large area is concentrated near neutral axis and hence it is inefficient in resisting bending.

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