Heat and Mass Transfer Interview Question

Following are the three way of heat transfer:

Conduction

Convection

Radiation

What is Fourier law of heat conduction?

Concept of critical thickness of insulation.

What is Fin? Where it is require and why?

Heat Transfer By convection.

Free convection and force convection.

Newtons law of cooling.

Thermal Boundary layer.

What is Difference between free and force convection.

Fluid Mechanics Interview Question

Fluid mechanics is the science which deals with the fluid in rest or in motion.

It can be classified in static, kinematics and dynamic.

Fluid static deal with fluid at rest.

Fluid kinematics deal with fluid in motion without considers any pressure effect.

In Fluid Dynamics Fluid is in Motion and pressure effect is consider.

Following are some question which can be ask in Interview.

What are the different between liquid and gases?

Property of the fluid:

Density, Specific Weight, Specific Volume, Specific Gravity, Dynamic Viscosity, Kinematic Viscosity

What Is Newtons law of viscosity?

What are the changes in viscosity with temperature?

What is Cohesion, Adhesion and Surface Tension.?

What is Bulk modulus of elasticity?

What is pressure head? And what are the different types of pressure?

Which is the pressure measuring instrument?

What is buoyancy? Condition for equilibrium of floating Body.

What are the different types of flow?

Explain steady and unsteady Flow, uniform and non-uniform flow, Laminar and turbulent flow etc.

What is the use of Bernoulli Equation?

Mechanical Engineering Interview Question: Engineering Drawing Interview Question

1.Define engineering drawing. 
Engineering drawing is a graphical language of an engineer to convey one’s ideas most effectively, easily, conveniently and with high speed.
So Engineering drawing is a starting point of all engineering branches such as Mechanical, Production, Civil, Electrical, Electronics, Computer science, Chemical etc. 
It is spoken, read, and written in its own way. Engineering drawing has its own grammar in terms of projections, conventional representations, types of lines, abbreviations, symbols and various geometric constructions.

2. Name different drawing instruments.
Drawing board, drawing sheet, mini-drafter, scale, pencil and sand paper block, cello-tape, eraser and compass.

3. What are the standard sizes of drawing sheets according to I.S.I. and which is suitable for drawing work?

The standard size of sheets according to I.S.I. are
A0 (1189 X 841),
A1 (841 X 594), 
A2 (594 X 420), 
A3 (420 X 297), 
A4 (297 X 210) and 
A5 (210 X 148).

Common Mechanical Interview Question/Answer For Fresher

What are Bevel Gears and what are its types?

Bevel gears are the type of gears in which the two shafts happen to intersect. The gear faces which are tooth bearing are conical in shape. They are generally mounted on shafts which are 90 degrees apart but they can be made to work at other angles as well. The bevel gears are classified into the following types on the basis of pitch surfaces and shaft angles:

> Mitre Gears: These types of gears are similar to each other ie. they have the same pitch angles and contain the same number of teeth. The shaft axes intersect at 90 degrees angle.

> Angular bevel gears: When two bevel gears connect at any angle apart from 90 degrees.

> Crown bevel gears: When the two shaft axes intersect at an angle greater than 90 and one of the bevel gears have a pitch angle of 90 degrees they are known as crown bevel gears.

> Internal bevel gears: In these type of gears the teeth on the gears is cut on the inside area of the pitch cone.

What are the different values that need to be determined in order to design a cylinder for an ICE?

The following values are needed to be determined:

> Thickness of the cylinder wall: The cylinder walls in an engine is made witness to gas pressure and the side thrust of a piston. This results in two types of stresses: longitudinal and circumferential stress. Both the types of stresses are perpendicular to each other and hence it is aimed to reduce the resulting stress as much as possible.

> Length and bore of the cylinder: The length of the cylinder and the length of the stroke is calculated on the basis of the formula: length of cylinder L = 1.15 times the length of the stroke (l). L = 1.15(l)

> Cylinder flange and studs: The cylinders are always cast integral as a part of the upper crankcase or in some cases attached to it by means of nuts and bolts. The flange is integral to a cylinder and henceforth its thickness should be greater than that of the cylinder wall. The thickness of flange should generally be between 1.2t-1.4t where t is the cylinder thickness.

The stud diameter is calculated by equating gas load ( due to max pressure ) to the grand total of all the resisting forces of the studs.

General Mechanical Interview Question/Answer For Fresher

During the design of a friction clutch what are the considerations that should be made?

In order to design a friction clutch the following points must be kept in mind:

> The material for the contact surfaces must be carefully selected.

> For high speed devices to minimize the inertia load of the clutch, low weight moving parts must be selected.

> The contact of the friction surfaces must be maintained at all the times without the application of any external forces.

> Provisions for the facilitation of repairs must be there.

> In order to increase safety the projecting parts of a clutch must be covered.

> A provision to take up the wearing of the contact surfaces must be present.

> Heat dissipaters to take away the heat from the point of contacting surfaces must be there.

What are the different types of brakes and explain them briefly?

Brakes can be classified on the basis of their medium used to brake, they are as follows:

> Hydraulic Brakes: These brakes as their name suggest use a fluid medium to push or repel the brake pads for braking.

> Electric Brakes: These brakes use electrical energy to deplete or create a braking force.

Both the above types of breaks are used primarily for applications where a large amount of energy is to be transformed.

> Mechanical Brakes: They can be further classified on the basis of the direction of their acting force: Radial Brakes: As their names suggests the force that acts on the brakes is of radial direction. They can further be classified into internal and external blades. Axial Brakes: In these types of brakes the braking force is acting in an axial direction as compared to radial brakes.

General Mechanical Interview Question/Answer For Fresher

 What are the assumptions made in simple theory of bending?

The assumptions made in the theory of simple bending are:

> The material of the beam is homogeneous this implies that it is uniform in density, strength and have isotropic properties meaning possessing same elastic property in all directions.

> Even after bending the cross section of the beam remains constant.

> During the initial stages the beam is straight and unstressed.

> All the stresses in the beam are within the elastic limit of its material.

> The layers of the beam are free to contract and expand longitudinally and laterally

> On any cross section the perpendicular resultant force of the beam is zero.

> Compared to the cross-sectional dimension of the beam the radius of curvature is very large.

Why is stress considered important in a shaft?

The following types of stresses are prevalent in shafts:

> At the outermost surface of the shaft the max shear stress occurs on the cross-section of the shaft.

> At the surface of the shaft on the longitudinal planes through the axis of the shaft the maximum longitudinal shear stress occurs.

> At 45 degrees to the maximum shearing stress planes at the surface of the shafts the major principal stress occurs. It equals the max shear stress on the cross section of the shaft.

> For certain materials where the tensile and compressive strengths are lower in measure as compared to the shear strength, then the shaft designing should be carried out for the lowest strengths.

> All these stresses are of significance as they play a role in governing the failure of the shaft. All theses stresses get generated simultaneously and hence should be considered for designing purposes.

Common Mechanical Interview Question/Answer For Fresher

What are the different types of fits, Tolerance, Clearance?

On the basis of Indian standards fits can mainly be categorized into three groups:

> Clearance Fit: These types of fits are characterized by the occurrence of a clearance between the two mating parts. The difference between the minimum size of the hole and the maximum size of the shaft is called the minimum clearance, the difference between the maximum size of the hole and the minimum size of the shaft is known as maximum clearance.

> Interference Fit: In these types of fits the size of the mating parts are predefined so that interference between them always occurs. The tolerance zone of the hole is completely below the tolerance zone of the shaft.

> Transition Fit: As the name suggests these type of fit has its mating parts sized limited to allow either clearance or interference. The tolerance zone of the hole and the shaft overlaps in case of such fits.

For a shaft designated as 40 H8/f7, calculate the tolerances.

Given: Shaft designation = 40 H8/f7

The shaft designation 40 H8/f 7 means that the basic size is 40 mm and the tolerance grade for

the hole is 8 ( i. e. I T 8) and for the shaft is 7 ( i. e. I T 7).

Since 40 mm lies in the diameter steps of 30 to 50 mm, therefore the geometric mean diameter,

D = Square root of (30 x 50) = 38.73 mm

We know that standard tolerance unit,

i = 0.45 x Cube root of (D) + 0.001 D

i = 0.45 × 3.38 + 0.03873 = 1.559 73 or 1.56 microns

i = 1.56 × 0.001 = 0.001 56 mm ...(1 micron = 0.001 mm)

The standard tolerance for the hole of grade 8 (IT8)

= 25 i = 25 × 0.001 56 = 0.039 mm 

The standard tolerance for the shaft of grade 7 (IT7)

= 16 i = 16 × 0.001 56 = 0.025 mm