Monday, 3 October 2016

Mechanical Interview questions

What will happen if we use petrol on diesel engine?
Petrol in Diesel:
ABNORMAL COMBUSTION
1. Combustion: initially the combustion process will be fine.. Until we get the combustion chamber temperature pretty high, then due to detonation, the mixture will start firing before TDC(As the compression ratio is much higher in Diesel)... As a result, abnormally it will fire and the forces on the mechanical components will be high.
2. Fuel system: This is about the Fuel injection system that includes fuel pump and all in the diesel engines.
Since fuel needs to be pumped in Diesel engines, they need to be self lubricated. I.e. the fuel is the lubricant for movable parts of the pump.
If petrol is put in a diesel engine, since it is less viscous, it will rather act as a solvent and the friction generated will be higher in the rubbing parts and that may fail.
What will happen if we use diesel on petrol engine?
Diesel in petrol:
NO COMBUSTION
1. Won't work: as diesel is more viscous and its comparatively non volatile. The air fuel mixture will be a non homogenous mixture. As a result it wouldn't burn.
2. Fuel system components: Even if we use GDI(Gasoline Direct Injection), the spray pressure of diesel in diesel engines is around 1500 bar, in gas it's a Max of 800-1000 bar. As a result, the atomisation of diesel won't take place. And again, it won't burn.

Mention any five engine manufacturers?
 Caterpillar Inc.
 JCB (company)‎
Perkins engines‎ 
Wärtsilä‎ 

Mention five machine tool manufacturers?
     
Kennametal   
Lokesh Machines   
United Drilling   
Tulive Develop   
Rapicut Carbide   
Rishi Laser   
Birla Precision   
ITL Industries   
Solitaire Mach   
Kulkarni Power   
Miven Machine   
EMA India   
Solid Carbide  

What is meant machine feed?
Cutting speed is defined as the speed at which the work moves with respect to the tool (usually measured in feet per minute). Feed rate is defined as the distance the tool travels during one revolution of the part. Cutting speed and feed determines the surface finish, power requirements, and material removal rate.

What is meant by depth of cut?
Depth of cut is the distance that the tool bit moves into the work. usually measured in thousandths of an inch or in millimeters. General machine practice is to use a depth of cut up to five times the rate of feed, such as rough cutting stainless steel using a feed of 0.020 inch per revolution and a depth of cut of 0.100 inch. which would reduce the diameter by 0.200 inch. If chatter marks or machine noise develops, reduce the depth of cut.

Difference between turning and facing?
The primary difference is that in Facing/ Turningoperations, your work piece that you need to machine is going to rotate, while in a milling operation, your tool is going to rotate. Turning is usually defined for cylindrical workpieces. This is used to reduce the diameter of a workpiece.

What is meant by knurling why its need?
Knurling is a manufacturing process, typically conducted on a lathe, whereby a pattern of straight, angled or crossed lines is cut or rolled into the material.
Purpose and meaning of knurling. Cylindrical parts, such as screw heads, round nuts, gripping surfaces on measuring tools and all kinds of handles or grips which have to be gripped firmly, must have roughened gripping surfaces.

Who is the father of industrial engineering?
Many sources say IE began with Frederick W. Taylor (1856-1915), who is often considered the father of industrial engineering/management science, and others say it was James Watt (1736–1819) inventing the steam engine, and some say it may have been Adam Smith (1723-1790), the laissez-faire economics pioneer who wrote 

What is meant JIT?
Just-in-time (JIT) is an inventory strategy companies employ to increase efficiency and decrease waste by receiving goods only as they are needed in the production process, thereby reducing inventory costs. This method requires producers to forecast demand accurately.

Saturday, 1 October 2016

DYNAMICS LAB VIVA QUESTIONS

Dynamics Lab Viva questions
1.      What is meant by mechanism?
a system of parts working together in a machine; a piece of machinery.
2.      Define Machine.
A machine is a device which receives energy in some available form and utilizes it to some particular type of work.
3.      Define Dynamics of Machines.
It deals with the study of forces acting on the parts of a machines.
4.      What is meant by slider crank mechanism?
The Slider-crank mechanism is used to transform rotational motion into translational motion by means of a rotating driving beam, a connection rod and a sliding body. 
5.      What is your aim of the experiment?
To find out the slider velocity and angular velocity of the experiment.
6.      Applications of slider crank mechanism?
·        Almost all reciprocating engines use cranks (with connecting rods) to transform the back-and-forth motion of the pistons into rotary motion. The cranks are incorporated into a crankshaft.
7.      What is meant by velocity?
the speed of something in a given direction.

8.      What is meant by angular acceleration?
Angular acceleration, also called rotational acceleration, is a quantitative expression of the change in angular velocity that a spinning object undergoes per unit time. It is a vector quantity, consisting of a magnitude component and either of two defined directions or senses.

9.      What is meant by beam?
Beams are generally horizontal structural members which transfer loads horizontally along their length to the supports where the loads are usually resolved into vertical forces. Beams are used for resisting vertical loads, shear forces and bending moments
10.  What are the types of beam?
a.       Simply Supported Beam
b.      Fixed Beam
c.       Cantilever Beam
d.      Continuously Supported Beam
11.   What are the types of Loading?
a.       Point load
b.      Uniformly distributed load
c.       Uniformly varying load

12.   What Is the aim of experiment?
To find the natural efficiency of the beam.

13.   What is meant by natural frequency?
the frequency at which a system oscillates when not subjected to a continuous or repeated external force.

14.  What is meant by frequency?
 It is defined as the number of cycles per second.

15.   What is the unit of frequency?

The SI unit of frequency is the hertz (Hz), named after the German physicist Heinrich Hertz. One hertz means that an event repeats once per second. A previous name for this unit was cycles per second (cps). The SI unit for period is the second.



16.   What is the use of cam?

A cam is a rotating or sliding piece in a mechanical linkageused especially in transforming rotary motion into linear motion or vice versa.
17.  What is meant by camp jump phenomenon?

Follower looses contact with cam surface when cam rotates beyond particular speed due to inertia forces
18.  What are types of cam?
a.       Wedge or flat cams
b.      Radial or Disc Cams
c.       Spiral cams
d.      Cylindrical cams
e.       Conjugate cams
f.        Globoidal Cams
g.       Spherical cams
19.  What are the types of follower available?
a.       (a) Knife edge follower
b.      (b) Roller follower
c.       (c) Flat faced follower
d.      (d) Spherical follower
20.  What is the aim of this experiment?
jump-speed characteristics of the cam & follower mechanism.


21.  What is meant by governor?
Governors are also known as speed limiters; they are used in different places like engines to measure and regulate the speed of an engine.
22.   What are types of governors?
a.       Watt governor
b.      Porter governor
c.       Proell governor
d.      Hartnell governor
23.  What is meant by stiffness of spring?
For an elastic body with a single degree of freedom (DOF) (for example, stretching or compression of a rod), the stiffness is defined as k = F δ {\displaystyle k={\frac {F}{\delta }}} ... δ is the displacement produced by the force along the same degree of freedom (for instance, the change in length of a stretched spring).
24.  What is meant by sensitivity of governor?
Sensitivity is definedas the ratio of the mean speed to the speed range of the governor over its limits of operation.
25.  What are classification of governors?
Generally Governors can be classified as either Centrifugal orInertia.
26.  What is meant by centrifugal governor?
The effort of the governor is obtained from the change in centrifugal force on (usually) two rotating masses known as Balls, when an increase or decrease in governor speed occurs.
27.  What is meant by inertia governors?
Inertia Governors work on a different principle. The governor balls are arranged so that the inertia forces caused by angular acceleration or retardation of the governor shaft tend to alter their positions. The amount of the displacement of the balls is controlled by springs and the governor mechanism to alter the supply of energy to the engine.

28.  What is meant by gyroscope?
a device consisting of a wheel or disc mounted so that it can spin rapidly about an axis which is itself free to alter in direction. The orientation of the axis is not affected by tilting of the mounting, so gyroscopes can be used to provide stability or maintain a reference direction in navigation systems, automatic pilots, and stabilizers.
29.  What is meant by gyroscope couple?
Gyroscopic Couple. If a uniform disc of polar moment of inertia is rotated about its axis with an angular velocity , its Angular Momentum is a vector and can be represented in diagram (c) by the line up which is drawn in the direction of the axis of rotation.
30.  What is the use of gyroscope couple?
Gyroscopes can be very perplexing objects because they move in peculiar ways and even seem to defy gravity. These special properties make ­gyroscopes extremely important in everything from your bicycle to the advanced navigation system on the space shuttle. A typical airplane uses about a dozen gyroscopes in everything from its compass to its autopilot. The Russian Mir space station used 11 gyroscopes to keep its orientation to the sun, and the Hubble Space Telescope has a batch of navigational gyros as well.
31.  What is meant by centrifugal force?
a force, arising from the body's inertia, which appears to act on a body moving in a circular path and is directed away from the centre around which the body is moving.
32.  What is meant by moment of inertia?
a quantity expressing a body's tendency to resist angular acceleration, which is the sum of the products of the mass of each particle in the body with the square of its distance from the axis of rotation.
33.  What is meant by whirling of shaft?
Whirling speed is also called as Critical speed of ashaft. It is defined as the speed at which a rotatingshaft will tend to vibrate violently in the transverse direction if the shaft rotates in horizontal direction. In other words, the whirling or critical speed is the speed at which resonance occurs.
34.  What is meant by flywheel?
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have an inertia called the moment of inertia and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed.
35.  What do you mean by inertia?
The property of matter offering resistance to any change of its state of rest or of uniform motion in a straight line is known as inertia.
36.  What is meant by axisymmetric?
symmetrical about an axis.
37.  What is meant by degree of freedom?
In statistics, the number of degrees of freedom is the number of values in the final calculation of a statistic that are free to vary. The number of independent ways by which a dynamic system can move, without violating any constraint imposed on it, is called number of degrees of freedom.
38.  What is meant by gear?
a toothed wheel that works with others to alter the relation between the speed of a driving mechanism (such as the engine of a vehicle) and the speed of the driven parts (the wheels).
39.  What is meant by gear ratio?
The Gear Ratio is defined as the input speed relative to the output speed.
40.  What is meant by gear train?
a system of gears which transmits motion from one shaft to another.
41.  What is meant by radius of gyration?
the distance from an axis at which the mass of a body may be assumed to be concentrated and at which the moment of inertia will be equal to the moment of inertia of the actual mass about the axis, equal to the square root of the quotient of the moment of inertia and the mass.
42.  What is meant by balancing of rotating mass?
The balancing of rotating bodies is important to avoid vibration. In heavy industrial machines such as gas turbines and electric generators, vibration can cause catastrophic failure, as well as noise and discomfort. In the case of a narrow wheel, balancing simply involves moving the centre of gravity to the centre of rotation. For a system to be in complete balance both force and couple polygons should be closed.
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43.  What is meant by mechanism?
When one of the links of a kinematics chain is fixed, the chain is known as mechanism. It may be used for transmitting or transforming motion e.g. engine indicators, typewriter etc.
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MECHANICAL ENGINEERING INTERVIEW QUESTIONS

MECHANICAL ENGINEERING INTERVIEW QUESTIONS
1.     What is meant by COP?
The coefficient of performance or COP (sometimes CP) of a heat pump is a ratio of heating or cooling provided to work required. Higher COPs equate to lower operating costs.
2.     What is meant by quality?
Fitness for use
3.     What is meant by entropy?
a thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.

"the second law of thermodynamics says that entropy always increases with time"

4.     What is meant by enthalpy?
a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.
5.     Density of steel?
8,050 kg/m3

The density of steel varies based on the alloying constituents but usually ranges between 7,750 and 8,050 kg/m3 (484 and 503 lb/cu ft), or 7.75 and 8.05 g/cm3 (4.48 and 4.65 oz/cu in).

6.     Density of water?

1,000 kg/m³

Type of steel
Percentage of carbon
Mild steel
Up to 0.25%
Medium carbon steel
0.25% to 0.45%
High carbon steel
0.45% to 1.50%
7.     Amount carbon percentage in steels?

8.     What is meant by firing order?
The firing order is the sequence of power delivery of each cylinder in a multi-cylinder reciprocating engine. This is achieved by sparking of the spark plugs in a gasoline engine in the correct order, or by the sequence of fuel injection in a Diesel engine.
The general firing order of a 4 cylinder engine is- 1---3---4---2.
9.     What is meant by curie point?
In physics and materials science, the Curie temperature (TC), or Curie point, is the temperatureat which certain materials lose their permanent magnetic properties, to be replaced by induced magnetism. The Curie temperature is named after Pierre Curie, who showed that magnetism was lost at a critical temperature
10. What is meant by tensile strength?
the resistance of a material to breaking under tension.
Material
Yield strength (MPa)
Ultimate tensile strength (MPa)
Steel, structural ASTM A36 steel
250
400-550
Steel, 1090 mild
247
841
chromium-vanadium steel AISI 6150
620
940
Human skin
15
20


GENERAL AWARENESS QUESTIONS

1.     What is meant by bitcoin?
a type of digital currency in which encryption techniques are used to regulate the generation of units of currency and verify the transfer of funds, operating independently of a central bank.

"bitcoin has become a hot commodity among speculators"

"bitcoins can be used for online transactions between individuals"
1 Bitcoin = 40160.14 Indian Rupee

2.     What is meant by PTC?
Paid to click (PTC) is an online business model that draws online traffic from people aiming to earn money from home. PTC websites act as middlemen between advertisers and consumers; the advertiser pays for displaying ads on the PTC website, and a part of this payment goes to the viewer when he views the advertisement.
3.     What is meant by ITC?
Its diversified business includes five segments: Fast-Moving Consumer Goods (FMCG), Hotels, Paperboards & Packaging, Agri Business & Information Technology. Established in 1910 as the Imperial Tobacco Company of India Limited, the company was renamed as the Indian Tobacco Company Limited in 1970 and further to I.T.C.

4.     How torrent works?
If 10,000 people are downloading the same file, it doesn't put a lot of stress on a central server. Instead, each downloader contributes upload bandwidth to other downloaders, ensuring the torrent stays fast. Importantly, BitTorrent clients never actually download files from the tracker itself.

5.     The manufacturer of apple phones?
Hon Hai Precision Industry Co., Ltd., trading as Foxconn Technology Group, is a multinational electronics contract manufacturing company headquartered in New Taipei, Taiwan. Foxconn is the world's largest electronics contractor manufacturer, and the third-largest information technology company by revenue.

The company signs all its products, "Designed by Apple in California," but in the U.S., design is as far as Apple is willing to go. The tech giant outsources hundreds of thousands of manufacturing jobs to countries like Mongolia, China, Korea and Taiwan.
6.     What is meant by C – level executives?
The highest-level executives in senior management usually have titles beginning with "chief" forming what is often called the C-suite. The traditional three such officers are chief executive officer (CEO), chief operations officer (COO), and chief financial officer (CFO).
7.     what is meant by OLED?
a light-emitting diode containing thin flexible sheets of an organic electroluminescent material, used for visual displays.

"because OLEDs emit light, they consume significantly less power"

8.     What Is meant by Wi-Fi?

The definition of WIFI is Wireless Fidelity.

9.     The basic plat form for android OS?
Java
The official language for Android development is Java. Large parts of Android are written in Java and its APIs are designed to be called primarily from Java. That said, it is possible to develop C and C++ apps using the Android Native Development Kit (NDK), however it isn't something that Google promotes.

10. Name five Languages used for computer programming?
SQL. It's no surprise SQL (pronounced 'sequel') tops the job list since it can be found far and wide in various flavors. ...
Java. The tech community recently celebrated the 20th anniversary of Java. ...

JavaScript. ... C# ... C++ ... Python. ... PHP. ... Ruby on Rails.