Mechanical Engineering Interview Questions with Answers

Interview Questions with Answers on Mechanical Design, Strength of Materials, Kinematics of Machine, Manufacturing Process, Engineering Mechanics & Mechanical Vibrations: Set 01


Question No. 01
What is mechanical engineering?
Answer:
Mechanical engineering is the discipline that applies 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.

Question No. 02
What is the difference between Technology and Engineering?
Answer:
Answer: Engineering is application of science. 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. 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 Calliper?
Answer:
Micrometer’s other name is Screw Gauze & Vernier calliper’s other name is slide calliper.

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 mould 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.

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 it 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.

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:
(A) Code is procedure of acceptance and rejection criteria.
(B) Standard is accepted values and compare other with it.
(C) 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.
(A)  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.
(B) Tube is easily shaped by bending, where Pipe needs some mechanical work to shape it.
(C) Tube is tight then Pipe.
(D) 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.
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