Mechanical engineering Interview Question an Answer for freshers/Engineering Interview Questions and Answers for Freshers & Experienced

How the net work to drive a compressor and its volumetric efficiency behave with increase in clearance

Work remains unaltered and volumetric efficiency decreases.

Posted Date:- 2022-06-25 05:20:21

What is endurance limit and what is its value for steel ?

Endurance limit is the maximum level of fluctuating stress which can be tolerated indefinitely. In most steels
this stress is
approximately 50o% of the ultimate tensile strength and it is defined as the stress which can be endured for ten million reversals
of stress.

Posted Date:- 2022-06-25 05:18:05

Under what condition a convergent divergent nozzle required ?

When pressure ratio is greater than critical pressure ratio.

Posted Date:- 2022-06-25 05:17:43

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

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.

Posted Date:- 2022-06-25 05:05:32

Which elemnents increase the corrosion resistance of steel ?

Chromium and nickel.

Posted Date:- 2022-06-25 05:02:42

What is the structure of pure iron and whether it is soft or hard ?

Ferrite and it is soft.

Posted Date:- 2022-06-25 05:02:22

Car tyres are usually made of ?

Styrene-butadine rubber.

Posted Date:- 2022-06-25 05:01:58

What is critical temperature in metals ?

It is the temperature at wlhich the phase change occurs in metals.

Posted Date:- 2022-06-25 05:01:07

What are killed steels and what for these are used ?

Killed steels are deoxidised in the ladle with silicon and aluminium. On solidification no gas evolution occurs in these steels because they are free trom oxygen.

Posted Date:- 2022-06-25 05:00:27

Which rays are produced by cobalt-6o in industrial radiography ?

Gamma rays.

Posted Date:- 2022-06-25 04:58:36

What is stellite ?

It is a non-ferrous cast alloy containing cobalt, chromium and tungsten.

Posted Date:- 2022-06-25 04:58:20

What is the percentage of chromium in 18: 4:1IISS ?


Posted Date:- 2022-06-25 04:57:55

Why PERT is preferred over CPM for evaluation of project ?

PERT is based on the approach of multiple time estimates for each activity.

Posted Date:- 2022-06-25 04:57:08

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

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

Posted Date:- 2022-06-25 04:56:45

Explain the difference between ferrite, austenite and graphite ?

Ferrite is the solid solution of carbon and other constituents in alpha-iron. It is soft, ductile and relatively weak. Austenite is the solid solution of carbon and other constituents in gamma-iron. It exists in ordinary steels at elevated temperatures, but it is also found at ordinary temperatilres in some stainless steels. Graphite has a hexagonal layer lattice.

Posted Date:- 2022-06-25 04:54:52

What is the difference between column and strut ?

Both column and strut carry comnpressive load. Column is always vertical but strut as member of structure could carry axial compressive load in any direction.

Posted Date:- 2022-06-25 04:54:14

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

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.

Posted Date:- 2022-06-25 04:43:34

Explain the difference between the points of inflexion and contraflexure.

At points of inflexion in a loaded beam the bending moment is zero and at points of contraflexure in loaded beam the bending moment changes sign trom increasing to decreasing.

Posted Date:- 2022-06-25 04:42:56

What is the difference between isotropic material and homogeneous material ?

In homogeneous mateial the composition is same throughout and in isotropic material the elastic constants are same in all directions.

Posted Date:- 2022-06-25 04:42:30

What is the difference between alpha iron, delta iron and gamma iron ?

The bcc form of iron exists between room temperature and 910°C, and between 1400°C and the melting point at 1539°C. The
lower temperature form is known as "alpha"-iron and the higher temperature form as "delta"-iron. The face-centered cubic
form existing between 910°C and 1400°C is referred to as "gamma-iron".

Posted Date:- 2022-06-25 04:41:51

What is the difference between alpha iron, delta iron and gamma iron ?

The bec form of iron exists between room temperature and 910°C, and between 1400°C and the melting point at 1539°C. The lower temperature formn is known as "alpha'-iron and the higher temperature form as "delta"-iron. The face-centered cubic form eXisting between 910°C and 1400°C is referred to as"gamma-iron.

Posted Date:- 2022-06-25 04:41:02

What is allotrope ? In what forms of cubic pattern, iron exists ?

Some elements exist in more than one crystalline form. Each form is known as "allotrope". Iron exists in two forms of cubic pattern, namely body centered culbic (bcc) and face-centered cubic (fee).

Posted Date:- 2022-06-25 04:40:26

Hydrogen cannot be removed easily from molten steel. What harm hydrogen has on property of steel ?

Execessive hydrogen results in the formation of small fissures often deseribed as hairline cracks or fakes in the steel. Large forgings in alloy steel are particularly sensitive to this phenomenon.

Posted Date:- 2022-06-25 04:40:01

For which parts the Wahl factor and Lewis form factor used ?

For springs and gears respectively.

Posted Date:- 2022-06-25 04:39:19

Give one example each of the following proportion of materials dimensional, physical, technological and mechanical.

Roughness, enthalpy, toughness, and hardness respectively.

Posted Date:- 2022-06-25 04:38:57

Explain the difference between pearlite and cementile ?

Pearlite is eutectoid mixture of ferrite and cementile. Cementite is chemical compound of iron and carbon.

Posted Date:- 2022-06-25 04:38:19

What is the name of solid solution of carbon in alpha iron and delta iron ?

Ferrite and austenite respectively.

Posted Date:- 2022-06-25 04:35:07

Give one example of metal classified as per structure as BCC, FCC, HCP and CCP.

• BCC (body centred cubic) structure-Molybdenum
• FCC (face centred cubic) structureAluminium
• HCP (hexagonal closed packed) structure-Zinc
. CCP (eubic dosed packed) structure-Copper.

Posted Date:- 2022-06-25 04:34:50

How is ceramic defined ?

It is a solid formed by combination of metallic and non-metallic elements.

Posted Date:- 2022-06-25 04:34:26

What does following alloy designation indicate FG 250?

Grey cast iron with tensile strength of 25o MPa.

Posted Date:- 2022-06-25 04:34:12

Which is the common element between brass and bronze ?


Posted Date:- 2022-06-25 04:33:40

How convective heat transfer is effected and on what factors it depends ?

Convective heat transfer is effected between a solid and fluid bya combination of molecular conduction within the fluid in combination with energy transport resulting from the motion of fluid particles. It depends on boundary layer configuration, fluid properties and temperature difference.

Posted Date:- 2022-06-25 04:33:19

For conduction of heat, the instantaneous rate of heat flow is product off three factors. What are these ?

1. Area of the section of the heat flow path, perpendicular to the direction of heat flow.
2. temperature gradient, i.e. change of temperature w.r.t. length of path
3. Thermal conductivity of material.

Posted Date:- 2022-06-25 04:31:16

What does thermal diffusivity of metals signify.

Thermal diffusivity is associated with the speed of propagation of heat into solids during changes in temperature with time.

Posted Date:- 2022-06-25 04:28:43

Which theories of failure are used for (a) ductile materials, and (b) brittle materials ?

For ductile materials, theories of failure used are maximum shear stress theory, and maximum energy of distortion theory; while for brittle materials, theory of maximum principal stress, and maximum strain are Used.

Posted Date:- 2022-06-25 04:28:06

List at least two factors that promote transition from ductile to brittle fracture.

Manner of loading, and the rate of loading promote transition from ductile to brittle fracture. A machine member may have ductile failure under static loading but may fail in brittle fashion when the load is fluctuating. Similarly a material may evidence
ductile failure under tensile loading at ordinary testing speed but if load is applied at a high velocity then failure may be brittle.

Posted Date:- 2022-06-25 04:27:44

While normal carburising and nitriding surface treatments increase fatigue strength, excessive treatment may decrease the fatigue strength. Why ?

Normal carburising/nitriding treatments increase volume due to phase transformation at Surface and introduee residual compressive surface stress and thus inerease the fatigue strength. By excessive treatment the high compressive stresses are introduced but these are balanced by high internal tensile stresses of equal value and the subsurface fatigue cracks may develop in the regions of high tensile stress and lead to early fatigue failure.

Posted Date:- 2022-06-25 04:27:05

Distinguish between creep and fatigue.

Creep is low and progressive deformation of a material with time under a constant stress at high temperalure applications. Fatigue is the reduced tendency of material to offer resistance to applied stress under repeated or fluctuating loading condition.

Posted Date:- 2022-06-25 04:25:33

Why fatigue strength decreases as size of a part increases beyond around 10 mm?

Perfection of material conditions is possible at lower sizes and as size increases, it is not possible to attain uniform structure of the material.

Posted Date:- 2022-06-25 04:17:55

Why is it that the maximum value which the residual stress can reach is the elastic limit of the material ?

A stress in excess of elastic limit, with no external force to oppose it, will relieve itself by plastic deformation until it reaches the value of the yield stress.

Posted Date:- 2022-06-25 04:08:49

If percentage elongation of a material is more than 200%, it is classed as ?

it is classed as Rubber.

Posted Date:- 2022-06-25 04:08:19

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

An elastomer is a polymer when its percentage elongation rate is
Greater than 100%.

Posted Date:- 2022-06-25 04:07:46

Whether individual components in composite materials retain their characteristics or not?

yes individual components in composite materials retain their characteristics

Posted Date:- 2022-06-25 04:07:15

Which element is added in steel to increase resistance to corrosion ?


Posted Date:- 2022-06-25 04:06:34

What is the percentage of carbon in cast iron ?

2.5% percentage of carbon in cast iron.

Posted Date:- 2022-06-25 04:06:16

Specific strength of materials is very high when they are in fibred size but lower when they are in bar form Why ?

Crystal structure has ordered, repeating arrangement of atoms. Fibres are liable to maintain this and thus have high specific strength. As size increases, the condition of ordered and repeating arrangements can't be guaranteed because of several types of defects and dislocations and thus the specific strength gets lower.

Posted Date:- 2022-06-25 04:04:40

What is Curie point ?

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

Posted Date:- 2022-06-25 04:03:01

What is view factor ?

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

Posted Date:- 2022-06-25 04:02:40

What are orthotropic materials?

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

Posted Date:- 2022-06-25 04:01:54

What is the difference between isotropic and anisotropic materials?

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

Posted Date:- 2022-06-25 04:01:23

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