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  1. 3 likes
    Tyres are mixture of various rubbers with carbon black added. Carbon black improves traction and wear resistance of pure rubber. Another reason is that black color has higher absorption capability by which the tyre of any vehicle becomes adhesive to road
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    Basic Difference is the how their are measured.. [1] i.e. A pipe is measured by ID(inner diameter) and a tube is measured by OD(outer diameter). [2] a pipe is like a vessel to store a liquid/gas so inside volume is important factor, while a tube is seen as structual member so total volume is important factor.
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    Why slenderness ratio is considered in design of members? 1. You can answer this question 2. You can like the best answer 3. You can share the question.
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    Air cooled, liquid cooled, carburated or fuel injected, Direct injection, Air filter design, inlet roar, ohv or ohc, hydraulic valve adjustment, shimmed tapets manual tappet asjustment. How many more reasons for different engine sounds do you want
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    Why do mechanical components fail? List down - Theories of Failure 1. You can answer this question 2. You can like the best answer 3. You can share the question.
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    Free, cost $10 - funny. I have a few versions of Free CAD that was actually free. I wonder if the later versions are now sold.
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    Why efficiency of Gas turbine is lower compared to IC engine ? 1. You can answer this question 2. You can like the best answer 3. You can share the question.
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    What is the difference between knocking and detonation in IC engine? 1. You can answer this question. 2. You can like the best answer. 3. You can share the question You can get updates of new questions on Facebook linkedin twitter & google plus
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    Why Tractors have their exhaust system(Silencer) fitted in the front of the vehicle,while other automobiles have their silencer at their back? 1. You can answer this question 2. You can like the best answer 3. You can share the question.
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    Version 1.0.0


    A brief idea about kind of diesel locomotives existing in the world. and it's simple mechanism
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    Following are the reasonable points that conclude the high torque and efficiency of diesel engine. Diesel engine uses simple mechanism for combustion unlike in gasoline engine. Removal of ignition system not only makes the mechanism simpler but also reduces the risk of improper combustion due to damage in ignition system. In short burning of the fuel is easy and always accessible. This results in higher efficiency diesel engine. Diesel fuel is a heavier hydrocarbon in which carbon and hydrogen are strongly bonded with each other. And when energy is supplied in form of heat it gets explode releasing much higher energy then gasoline. In short diesel fuel has higher energy density then gasoline which results in huge explosion. One more factor for higher efficiency in diesel engine is its property of lubrication. Although all fuel has property of lubrication but diesel fuel has much higher lubrication then gasoline fuel. The compression ratio is much higher in diesel as compared to gasoline because in diesel engine air is alone compressed inside the cylinder and it’s a known fact that gas easily compresses then liquid. This is not so in gasoline engine because air-fuel mixture is compressed inside the cylinder. This higher compression gives higher heat and simultaneously higher torque. We can’t use Carnot cycle to get 100% efficiency but can use its principle to attain maximize efficiency. In diesel engine heat is added at constant pressure which results in higher utilization of heat energy to get maximize work output. These were the advantageous features of diesel engine but it has some demerits as well like it releases highly toxic gases, noisy, higher maintenance cost and starting problem (now starting problem is eliminated by using a bulb nearby to the cylinder) to heat the engine before ignition. And it is costlierthan gasoline engine but with optimum operation and good maintenance resolve all these problems.
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    Very nice art work and short, simple explanations. Well done! DrD
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    why flywheel are used in punching machine: It decreases the variation of speed during each cycle of punching machine and it decreases the fluctuation of speed due to difference in output and input and It also stores energy during idle stroke and releases during working stroke.
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    If there were no flywheel, the punch would require a very large motor in order to provide the required power for the punch stroke. When not in the punch stroke, all that power would be essentially idle, waiting to be called upon for a brief period for the punch operation. By including the flywheel, you have a means to store up energy, and make it available as needed during the punch operation. Then, during the idle period, the motor pumps energy back into the flywheel to bring it back to full speed. DrD
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    Rankine cycle: transition from isobar to adiabatic process. Carnot cycle: transition from isothermal to adiabatic process.
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    A pipe is measured by Nominal Pipe Size (NPS) per Inch and Schedule number ( Thickness of pipe ) and tube is measures by Outside Diameter (OD) and BWG number ( Thickness of Tube) . The common Pipes size as ANSI are produced from size 1/8" to 48". Pipes are used for mass. fluid and gas transfer in different industrial. Tubes are manufactured from size 1/32" to 12". Tubes are used for heat transfer in Heat exchanges,boilers,vessels and also in fire burners ( size 2" and more) and as instruments tubes and also accessories tools in Turbines and Compressors.
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    While both devices provide a form of forced induction for internal combustion engines The primary difference lies in how the devices are powered. Turbochargers are powered by exhaust gasses. Superchargers are powered by a belt, chain link, or gears, directly to the engine (the crankshaft in most cases). Turbochargers perform better at higher rpm's do to more exhaust gases spinning the turbine which then in turn causes the compressor to draw in more air. This has a downside due to lag time which can be referred to as spooling up. Superchargers work better at low RPM's due to the direct link to the engine and lack of lag time however they are limited to rotating at a max speed matching that which the crankshaft can turn the mechanical linkage to the supercharger itself. One system not mentioned in this article is the twin charger system. This combines the benefits of both the supercharger and a turbocharger in creating a zero gap power band. The supercharger takes care of the lower RPMs while the turbo kicks in during the higher rpm's. The applications of this are mostly seen on engines with smaller displacement and a wide rpm range.
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    Dial Gauge is a measuring instrument used to measure small distances Slip Gauge is a piece of hardened steel which is machined in a standard size.This is used to accurately make gaps
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    When we manufacture any product, usually we manufacture it by casting or forging process. To get a proper surface finish of that product we need a proper machining. At the time of maching a certain amount of material usually removed from the surface of the core product. For this reason a tolerance is needed over the designed dimension to maintain the actual dimension. Beside this reason, tolerances also kept to maintain the needed dimension after thermal expansion or contraction at the time of solidification during casting process.
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    In welding two metals are melted together. In brazing two or more materials are joined by the use of a third, dissimilar material, such as braze alloy. brazing is not stronger as welding
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    Turbo charger and super charger increase the compression ratio in an engine without changing cylinder and piston dimensions. In other words we can say super charger or turbo charger increases air density at intake manifold of the engine. Difference between Turbocharger and supercharger. Both perform same function but their driving mechanism is different. Super charger utilizes engine power for operation by coupling with engine rotary source. While Turbo charger use waste exhaust gas pressure and flow in order to rotate and produce air charge to intake manifold.
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    Atmospheric pressure is the pressure applied by the air on the ground as a result of the fluid volume of air directly above.....it is roughly 14.7psi or 1 bar. Atmospheric pressure is constantly changing asa result of the eweathter...stormy is generally low pressure (about .96bar) whereas fine weather can be a result of high pressure (1.012 bar) as a result this is standardised as atmospheric pressure at 1 bar....a more useful unit is mBar, but can also be psi, mmHg etc. The variation above or below 1 bar of pressure as measured is generally known as "gauge" pressure as it does not take into account the surrounding atmospheric pressure (which is hydrostatic btw) therefore only measuring the difference between the "zero" which is in effect atmospheric and the vessel being measured. Similarly vacuum pressure is a measure of pressure below that of surrounding ambient....generally in Bar or Torr. Vacuum pressure is ALWAYS that below the surrounding medium (which is generally air although occasionally within the confines of a high pressure environ. ). Absolute pressure is a corrected pressure which takes into account the surrounding air pressure to read the true pressure. It is not always the case, but it can generally be read as pressure + 1bar as it completely negates the effects of the surrounding medium...comparing directly to a total vacuum.
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    What is the exact difference between refrigerator and a air conditioner ? 1. You can answer this question 2. You can like the best answer
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    Go through this link http://www.skf.com/in/products/bearings-units-housings/ball-bearings/principles/selecting-bearing-size/bearing-life/load-ratings/index.html
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    With regard to materials, you must stay away from most metals, and especially aluminium. They will corrode rapidly in a salt water environment and lose strength accordingly. Think more of polyesters and epoxy materials. Are we to understand that rotation is in a horizontal or vertical plane? Assuming a horizontal plane for the rotation, you will need an airfoil shape, as the turning force is developed by hydrodynamic forces. Where will you generate power, below the water or above? This is a difficult problem, one that I worked on for the US Navy some years ago. You have a lot of hurdles to face to get this to work. DrD
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    Is P the number of planets, or the number of teeth on a planet gear? If it is the number of planets, I don't think it is true at all; at least, I do not see it. DrD PS: Remember that, for gears that actually mesh, the number of teeth on the two gears are each proportional to the pitch radii of the gears.
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    I"m glad to hear that you found something useful, Tim. It is almost comic that the name is FreeCAD, but it costs $10. I wonder what it would cost if it were called PayForItCAD? DrD
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    Look for an opportunity in a company that actually manufactures some product. Such an employer will usually lket you see the whole process, from design, through manufacturing engineering, to sales and service. This is particularly valuable for a student. Do not go to a company that only does paper studies or the like; this is not the whole picture. DrD
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    A shaft is a power transmission device, connected to a gear or coupler on both ends. An axle may or may not transmit power. An axle may just be used for a center of rotation on non-driven wheels such as the front wheel of a motorcycle. An axle may or may not be a shaft.
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    Turbocharger : it is used as economizer in commercial vehicles and some passenger vehicle to boost up performance in lesser quantity of fuel.It have a compressor wheel and a turbine wheel attached to a common shaft and runs by the exhaust gases of engine.Firstly turbine wheel starts to rotate as it is pushed by the exhaust gases then the compressor connected to same shafts rotates and manage its function to sucks fresh air and sends it engine combustion chamber extra air means better rate combustion ultimately batters the performance of the whole unit. But the problem of turbo lag occurs, it's the time taken for turbocharger comes in action after exhaust gases reaches the turbine wheel Supercharger : Supercharger is installed for the same purpose in the vehicle, but with more adaptivity. it is installed in sports class vehicle used for racing purpose they are only performance oriented,that's why they are connected to directly the output shaft of the vehicle.It will successfully fulfill the need of sports vehicle of rapid change in velocities with high power and torque, by neglecting the need of giving emphasis to fuel economy upto some extent.There is one input geared shaft and output geared shaft in a properly meshed condition which rotates and other ultimately do its job.
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    1. What is the difference between isotropic and anisotropic materials ? Ans: 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. 2. What are orthotropic materials ? Ans: It is a special class of anisotropic materials which can be described by giving their prop¬erties in three perpendicular directions e.g. wood; composites. 3. What is view factor ? Ans: View factor is dependent upon geometry of the two surfaces exchanging radiation. 4. What properties need to be considered for applications calling for following re¬quirements : (i) rigidity (ii) strength for no plastic deformation under static load (iii) strength to withstand overload without fracture. (iv) wear resistance (v) reliability and safety. Ans: (i) Rigidity—Elastic modulus and yield strength (ii) Strength (for no plastic deformation under static loading)—yield point (iii) Strength (overload)—Toughness and impact resistance (iv) Wear resistance—Hardness (v) Reliability and safety—Endurance limit and yield point. 5. Explain the effects of alloying chromium and nickel in stainless steel. Ans: Addition of nickel and chromium increases the tensile strength and increase in resistance to corrosion takes place. 6. Mention two types of dislocations. Ans: 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 fom their regular ideal positions. 7. What are the principal constituents of brass? Ans: Principal constituents of brass are copper and zinc. 8. What is Curie point ? Ans: Curie point is the temperature at which ferromagnetic materials can no longer be magnetised by outside forces. 9. Specific strength of materials is very high when they are in fibre size but lower when they are in bar form Why ? Ans: 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. 10. What is the percentage of carbon in cast iron ? Ans: 2.5%. 11. Which element is added in steel to increase resistance to corrosion ? Ans: Chromium. 12. Whether individual components in composite materials retain their characteristics or not? Ans: yes. 13. An elastomer is a polymer when its percentage elongation rate is ? Ans: Greater than 100%. 14. If percentage elongation of a material is more than 200%, it is classed as ? Ans: Rubber. 15. Why is it that the maximum value which the residual stress can reach is the elastic limit of the material ? Ans: 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. 16. Why fatigue strength decreases as size of a part increases beyond around 10 mm? Ans: Perfection of material conditions is possible at lower sizes and as size increases, it is not possible to attain uniform structure of the material. 17. Distinguish between creep and fatigue. Ans: Creep is low and progressive deformation of a material with time under a constant stress at high temperature applications. Fatigue is the reduced tendency of material to offer resistance to applied stress under repeated or fluctuating loading condition. 18. While normal carburising and nitriding surface treatments increase fatigue strength, excessive treatment may decrease the fatigue strength. Why ? .Ans: Normal carburising/nitriding treatments increase volume due to phase transformation at Surface and introduce residual compressive surface stress and thus increase the fatigue strength. By excessive treatment the high compressive stresses are introduced but these are balanced by high in¬ternal 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. 19. List at least two factors that promote transition from ductile to brittle fracture. Ans: Manner of loading, and the rate of loading promote transition from ductile to brittle frac¬ture. 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. 20. Which theories of failure are used for (a) ductile materials, and ( brittle materials ? Ans: 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. 21. What does thermal diffusivity of metals signify. Ans: Thermal diffusivity is associated with the speed of propagation of heat into solids during changes in temperature with time. 22. For conduction of heat, the instantaneous rate of heat flow is product of three factors. What are these ? Ans: (i) Area of the section of the heat flow path, perpendicular to the direction of heat flow. (ii) temperature gradient, i.e. change of temperature w.r.t. length of path. (ii) Thermal conductivity of material. 23. How convective heat transfer is effected and on what factors it depends ? Ans: Convective heat transfer is effected between a solid and fluid by a 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. 24. Which is the common element between brass and bronze ? Ans: Copper. 25. What does following alloy designation indicate FG 250 ? Ans: Grey cast iron with tensile strength of 250 MPa. 26. How is ceramic defined ? Ans: It is a solid formed by combination of metallic and non-metallic elements. 27. Give one example of metal classified as per structure as BCC, FCC, HCP and CCP. Ans: BCC (body centred cubic) structure—Molybdenum FCC (face centred cubic) structure—Aluminium HCP (hexagonal closed packed) structure—Zinc CCP (cubic dosed packed) structure-Copper. 28. What is the name of solid solution of carbon in alpha iron and delta iron ? Ans: Ferrite and austenite respectively. 29. Explain the difference between pearlite and cementile ? Ans: Pearlite is eutectoid mixture of ferrite and cementile. Cementite is chemical compound of iron and carbon. 30. Give one example each of the following proportion of materials dimensional, physical, technological and mechanical. Ans: Roughness, enthalpy, toughness, and hardness respectively. 31. For which parts the Wahl factor and Lewis form factor used ? Ans: For springs and gears respectively. 32. How oxygen can be removed from steel during melting? What are fully killed steels ? Ans: Oxygen can be removed by adding elements such as manganese, silicon or aluminium which, because of their high affinity for oxygen, react with it to form non-metallic oxides which rise into the slag. Steels which have had most of their dissolved oxygen removed are called "fully killed steels". 33. Hydrogen cannot be removed easily from molten steel. What harm hydrogen has on property of steel ? Ans: Execessive hydrogen results in the formation of small fissures often described as hairline cracks or flakes in the steel. Large forgings in alloy steel are particularly sensitive to this phenom¬enon. 34. What is allotrope ? In what forms of cubic pattern, iron exists ? Ans: 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 cubic (bcc) and face-centered cubic (fee). 35. What is the difference between alpha iron, delta iron and gamma iron ? Ans: 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". 36. Metals, in general are of low strength and do not possess required physio-chemical and technological properties for a definite purpose. Alloys are therefore more than metals alone. Discuss the arrangement of atoms and structures of alloys. Ans: Alloys are produced by melting or sintering two ore more metals, or metals and a non-metal, together. Alloys possess typical properties inherent in the metallic state. The chemical elements that make up an alloy are called its components. An alloy can consist of two or more components. The phase and structures of alloys describe the constitution, transformations and properties of metals and alloys. A combination of phases in a state of equilibrium is called a system. A phase is a homogeneous portion of a system having the same composition and the same state of aggregation throughout its volume, and separated from the other portions of the system by interfaces. For instance, a homogeneous pure metal or alloy is a single-phase system. A state in which a liquid alloy (or metal) coexists with its crystals is a two-phase system. Structure refers to the shape, size or the mutual arrangement of the corresponding phases in metals or alloys. The structural components of an alloy are its individual portions, each having a single structure with its characteristic features. 37. What is the difference between isotropic material and homogeneous material ? Ans: In homogeneous material the composition is same throughout and in isotropic material the elastic constants are same in all directions. 38. Explain the difference between the points of inflexion and contraflexure. Ans: 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 from increasing to decreasing. 39. What is the difference between proof resilience and modulus of resilience ? Ans: 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. 40. What is the difference between column and strut ? Ans: Both column and strut carry compressive load. Column is always vertical but strut as member of structure could carry axial compressive load in any direction. 41. Explain the difference between ferrite, austenite and graphite ? Ans: 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 temperatures in some stainless steels. Graphite has a hexagonal layer lattice. ' 42. Explain the terms solid solution, eutectic, eutectoid and peritectic. Ans: Solid Solution. When a homogeneous mixture of two (or more) atomic forms exists in solid state, it is known as solid solution. Eutectic. A mixture of two (or more) phases which solidify simultaneously from the liquid al¬loy is called an eutectic. Alloys in which the components solidify simultaneously at a constant tem¬perature the lowest for the given system, are called eutectic alloys. Eutectoid. Eutectoid alloys are the alloys for which two solid phases which are completely soluble become completely insoluble on cooling before a certain temperature called eutectoid tem¬perature. Peritectic. A peritectic transformation involves a reaction between a solid and liquid that form a different and new solid phase. This three phase transformation occurs at a point called peritectic point. 43. What do you understand by critical points in iron, iron-carbide diagram ? Ans: The temperatures at which the phase changes occur are called critical points (or tem¬peratures). 45. Why PERT is preferred over CPM for evaluation of project ? Ans: PERT is based on the approach of multiple time estimates for each activity. 46. What is the percentage of chromium in 18 : 4 : 1 IISS ? Ans: 4%. 47. What is stellite ? Ans: It is a non-ferrous cast alloy containing cobalt, chromium and tungsten. 48. Which rays are produced by cobalt-60 in industrial radiography ? Ans: Gamma rays. 49. What are killed steels and what for these are used ? Ans: Killed steels are deoxidised in the ladle with silicon and aluminium. On solidification no gas evolution occurs in these steels because they are free from oxygen. 50. What is critical temperature in metals ? Ans: It is the temperature at which the phase change occurs in metals. 51. Car tyres are usually made of ? Ans: Styrene-butadine rubber. 52. What is the structure of pure iron and whether it is soft or hard ? Ans: Ferrite and it is soft. 53. Which elements increase the corrosion resistance of steel ? Ans: Chromium and nickel. 54. What causes hardness in steel ? How heat treatment alters properties of steel ? Ans: 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. 55. Explain the formation of microstructures of pearlite, bainite and martensite in steel. Ans: If austenite containing about 0.80 percent carbon is slowly cooled through the critical temperature, ferrite and cementite are rejected simultaneously, forming alternate plates or lamellae. This microstructure is called pearlite. At temperatures just belot the A1, the transformation from austenite.to pearlite may take an appreciable time to initiate and complete, but the product will be lameller pearlite. As the transformation temperature is lowered, the time to initiate transformation shortens but the product is pearlite of increasing fineness, and at temperatures approaching 550°C it cannot be resolved into its lamellar constituents. Further deerease in transformation temperature causes a lengthening of the ncubation period and a change in structure of the product to a form known as "bainite". If the temperature is lowered sufficiently, the diffusion controlled nucleation and growth modes of transformation are suppressed completely and the austenite transforms by a diffusionless process in which the crystal lattice effectively shears to a new crystallographic configuration known as "martensite". This phase has a tetragonal crystal structure and contains carbon in supersaturated solid solution. 56. How with alloying of steel it is possible to a achieve properties which can not be achieved with heat treatment ? Ans: A prerequisite to the hardening of steels is that martensite should be formed on cooling, but this can only be achieved if the rate of cooling is great enough to suppress the formation of pearlite or bainite and in plain carbon steels this can be achieved by quenching relatively small specimens 57. What are the major effects of alloying elements? Ans: (1) To alter the transformation temperatures and times (2) To modify the room temperature and elevated temperature strengths of given structures by (a) stiffening the crystals and ( introducing complex precipitates which tend to harden the steel. (3) To modify the type of oxide film formed on the surface of the steel and thereby affect its corrosion resistance. 58. What is the difference between austenite stabilisers and ferrite stabilisers ? Ans: Austenite stabilisers have the effect of extending the temperature range overwhich austenite is formed. Such elements are carbon, manganese, nickel, copper and cobalt. Ferrite stabilisers have the effect of extending the temperature range over which alpha and delta ferrite are formed, which consequently reduces temperature range over which austenite is formed. Such elements are silicon, chromium, molybdenum, tungsten, titanium and niobium. 59. What are the effects of carbon on the properties of steel. Ans: In general, an increase in carbon content produces higher ultimate strength and hardness but lowers ductility and toughness of steel alloys. Carbon also increases air-hardening tendencies and weld hardness, especially in the presence of chromium. In low-alloy steel for high-temperature applications, the carbon content is usually restricted to a maximum of about 0.15% in order to assure optimum ductility for welding, expanding, and bending operations. To minimize intergranular corro¬sion caused by carbide precipitation, the carbon content of austenitic (18-8 type) alloys is limited in commercial specifications to a maximum of 0.08%, or even less, i.e. 0.03% in the extremely low-carbon grades used in certain corrosion-resistant applications. In plain carbon steels in the normalised condition, the resistance to creep at temperatures below 440°C appears to increase with carbon content up to 0.4% carbon, at higher temperatures there is but little variation of creep properties with carbon content. An increase in carbon content lessens the thermal and electrical conductivities of steel and increases its hardness on quenching. 60. What is the role of silicon as alloying element in steels ? Ans: Silicon contributes greatly to the production of sound steel because of its deoxidizing and degasifying properties. When added in amounts up to 2.5%, the ultimate strength of the steel is increased without loss in ductility. Silicon in excess of 2.5% causes brittleness, and amounts higher than 5% make the steel non-malleable. Resistance to oxidation and surface stability of steel are increased by the addition of silicon. These desirable effects partially compensate for the tendency of silicon to lower the creep properties of steel. Silicon increases the electrical resistivity of steel and decreases hysteresis losses. 61. Discuss the role of manganese in alloying steels. Ans: Manganese is an excellent deoxidizer and sulfur neutralizer, and improves the mechanical properties of steel, notably the ratio of yield strength to tensile strength at normal temperatures. As an alloying element, manganese serves as an inexpensive means of preventing "hot shortness". It improves rolling properties, hardenability, and resistance to wear. However manganese increases the crack sensitivity of weldments, particularly with steels of higher carbon content. 62. Define buckling factor. Ans: It is the ratio of the equivalent length of column to the minimum radius of gyration. 63. What do you understand by catenary cable ? Ans: A cable attached to the supports and carrying its own weight. 64. What is coaxing ? Ans: It is the process of improving fatigue properties by first under-stressing and then increasing the stress in small increments. 65. What is difference between conjugate beam and continuous beam ? Ans: A conjugate beam is an imaginary beam of same size as original beam and carrying a distributed load in accordance with the bending moment diagram. A continuous beam is one which is resting on more than two supports. 66. What is isotropic material ? Ans: It is a material having same elastic constants in all directions. 67. Explain difference between modulus of resilience and modulus of rigidity ? Ans: Modulus of resilience is the maximum strain energy stored in a material per unit volume and modulus of rigidity is the ratio of shearing stress to the shearing strain within the elastic limit. 68. What is the difference between basic hole and basic shaft ? Ans: A basic hole is one whose lower deviation is zero and in case of basic shaft the upper deviation is zero. 69. What for pyranometer is used ? Ans: It is used to measure the total hemispherical solar radiation. 70. Describe transfer machines in brief. Ans: It is an automatic machine in which workpiece alongwith fixture is transferred from one station to other automatically and several operation on workpiece are performed at each station. 71. What is burnt-out point ? Ans: It corresponds to maximum heat flux at which transition occurs from nucleate boiling to film boiling. 72. What do you understand by eutectic ? Ans: It is mechanical mixture of two or more phases which solidify simultaneously from the liquid alloy. 72. Explain the difference between grey iron and white iron. What is mottled iron ? Ans: The carbon in cast iron could exist at room temperature as either iron carbide, or as graphite which is the more stable form. Irons containing carbon as graphite are soft, easily machinable and are called "grey irons". Irons with carbon present as iron carbide are extremely hard, difficult to machine and are called "white" irons. Irons with fairly equal proportions of graphite and iron carbide have intermediate hardness and are called "mottled" irons. 73. The graphite in grey irons exists in the form of flakes which act as stress-raisers under tensile loading and consequently grey irons have relatively low tensile strength and ductility. Still grey iron is extensively used in engineering. Why ? Ans: Grey iron is extensively used in engineering because of following characteristics. (a) Cheapness. ( Low melting point and high fluidity making it suitable for castings of intricate shape. © Relatively good erosion and corrosion resistance. (d) High damping capacity, with respect to vibration. (e) Relatively good mechanical properties under compressive loading. 74. Under what condition a convergent divergent nozzle required ? Ans: When pressure ratio is greater than critical pressure ratio. 75. What is endurance limit and what is its value for steel ? Ans: Endurance limit is the maximum level of fluctuating stress which can be tolerated indefinitely. In most steels this stress is approximately 50% of the ultimate tensile strength and it is defined as the stress which can be endured for ten million reversals of stress. 76. How the net work to drive a compressor and its volumetric efficiency behave with increase in clearance volume ? Ans: Work remains unaltered and volumetric efficiency decreases. 77. What do you understand by sulphur print ? Ans: Sulphides, when attached with dilute acid, evolve hydrogen sulphide gas which stains bromide paper and therefore can be readily detected in ordinary steels and cast irons. While sulphur is not always as harmful as is sometimes supposed, a sulphur print is a ready guide to the distribution of segregated impurities in general. 78. What is the different between brass and bronze ? Ans: Brass is an alloy of copper with zinc; and bronze is alloy of copper with tin. 79. What is the effect of addition of zinc in copper? What is the use of 70/30 brass ? Ans: By addition of zinc in copper, both tensile strength and elongation increases. The 70/30 brass has excellent deep drawing property and is used for making radiator fins. 80, What for admirality brass used ? Ans: Admirality brass with 29% zinc and 1% tin has good corrosion resistance and is used for condenser and feed heater tubes. Aluminium is also added to brass to improve corrosion resistance. 81. What is the maximum use of magnesium ? Ans: Magnesium is used to alloy with aluminium and as an additive for making SG (Spheroidal Graphite) iron. 82. What for zinc finds applications ? Ans: Galvanizing consumes the largest proportion of zinc. Zinc is resistant to corrosion but is attacked by acids and alkalies. Zinc alloy.s are suited for making die casting since the melting point is reasonably low. 83. Which factors influence the type of fracture in failure of a material ? Ans: Seven factors influencing type of failure are : (i) Type of material (inherent structure properties), (ii) Manner of loading (Static versus dynamic), (iii) Range of imposed stress, (iv) Strain rate (static, dynamic, impact), (v) Stress distribution (discontinuity in material/shape), (vi) temperature, and (vii) surface treatment. 84. What is the name given to ratio of actual cycle efficiency and ideal cycle efficiency. Ans: Efficiency ratio. 85. List two effects of manganese in plain carbon steels. , Ans: Manganese increases tensile strength and hardness. It decreases weldability. 86. Name the strongest and weakest type of atomic bonds. Ans: Metallic bond is strongest and molecular bond also known as Vander Waals bond is weakest. 87. In which process internal energy remains constant ? Ans: Isothermal process. 88. What is temper embrittlement in alloy steels and what are its effects ? Ans: Embrittlement attack is usually intergranular in metals, i.e. cracks progress between the grains of the polycrystalline material. It imparts a tendency to fail under a static load after a given period of time in those alloy steels which are susceptible to embrittlement. 89. What are whiskers ? Ans: Whiskers are very small crystals which are virtually free from imperfections and dislocations. 90. What is Bauschinger effect ? Ans: According to Bauschinger, the limit of proportionality of material does not remain constant but varies according to the direction of stress under cyclic stresses. 91. What is the difference between heat capacity and specific heat of a material ? Ans: The heat capacity of a material is the amount of heat transformed to raise unit mass of a material 1 degree in temperature. The specific heat of a material is the ratio of the amount of heat transferred to raise unit mass of a material 1 degree in temperature to that required to raise unit mass of water 1 degree of temperature at some specified temperature. For most engineering purposes, heat capacities may be assumed numerically equal to;specific heats. 92. Explain the rule to find specific heat of aqueous solutions. Ans: For aqueous solutions of salts, the specific heat can be estimated by assuming the specific heat of the solution equal to that of the water alone. Thus, for a 15% by weight solution of sodium chloride in water, the specific heat would be approximately 0.85. 93. What do you understand by latent heat ? Give four examples of latent heats. Ans: For pure substances, the heat effects accompanying changes in state at constant pressure (no temperature change being evident) are known as latent heats. Examples of latent heats are : heat of fusion, vaporisation, sublimation, and change in crystal form. 94. Define the terms free energy and free enthalpy. What is their significance and importance ? Ans: Free energy (or Helmholtz function) is defined as/= u -Ts. It is equal to the work during a constant-volume isothermal reversible nonflow process. Free enthalpy (or Gibbs function) is defined as g = h - Ts (where u = internal energy, h = enthalpy, T = temperature, s = entropy) Gibbs function is of particular importance in processes where chemical changes occur. For reversible isothermal steady-flow processes or for reversible constant-pressure isothermal nonflow processes, change in free energy is equal to net work. 95.Which parameter remains constant in isochoric process ? Ans: Volume. 96. What is polytropic process ? Under what conditions it approaches isobaric, isothermal, and isometric process ? In which reversible process no work is done ? Ans: A polytropic process is one that follows the equation pun = constant (index n may have values from - oc to + oo. This process approaches isobaric when n = 0, isothermal when n = 1, and isometric when n = <x>. No work is done in isometric process. 97. Whether superheated steam can be treated like ideal gas ? Ans: Yes. 98. Out of constant pressure and constant volume lines on TS diagram which line has higher slope ? And whether slope is constant or variable ? Ans: Constant volume line. Slope is variable. 99. Whether entropy is intensive property or extensive property ? Ans: Entropy is extensive property. 100. In which process fluid expands but does no work ? Ans: Throttling process.
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    Both DrD and Edgardo have important information to add to this discussion however, they have only discussed a part of the answwer. I believe that they have spoken about relevant points for discussion. Here are my thoughts. The larger diameter wheels on the rear of the tractor deliver a far greater contact patch, due to the tangent ratio to be able to successfully deliver the enormous torque generated by the engine and drive line combination. Engineer John
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    Sajal, please explain the phrase, "This helps to man over the axle assembly ...." I don't know quite what this means. As I stated before, there is no single cone that will be appropriate to all track radii. Try rolling a cone with a very wide apex angle; it will roll in a fairly small circle. Then roll a cone with a very small apex angle; it will roll in a very large circle. There is no single cone that will fit perfectly for all situation. Thus, while the cone helps, it is not a complete fix. It improves the situation, but there is still some sliding in most curves. DrD
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    I agree with Mr Reid .Machining of wheel outside diameter with a taper profile eliminates need of differential in rail wagon.This taper has got a direct relationship with curvature of the rail track.Also,the final machining of wheel outside diameter is accomplished with fine grinding operation.This helps to man over the axle assembly to slide left or right depending upon left or right turn.When the car takes a left turn,wheel on left track has to travel less distance than the right one hence the smaller diameter area of the left wheel will be in contact with the track.Similarly,right side larger diameter of wheel will be active so that right side wheel can travel more distance.
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    In ci engines, as we know that when the mixing of fuel and air is not very homogeneous as compared to si engines, the pressure rise is also not uniform. Due to this, the combustion takes place non-uniformly at many places at the time of ignition, and when more than two flames are generated on two different sites in piston cylinder, they follow the knock phenomena.
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    When the belt moves over the pulley to transmit power, the tension in the tight side is more than than the tension in slack side. As the belt material is elastic, it elongates more on tight side than on slack side, resulting in unequal stretching on two sides of the drive. Therefore, the length of the belt received by the driving pulley is more than the length that moves of the driving pulley. Hence, belt must creep back slightly relative to driving pulley rim. On the other hand, the length of the belt received by the driven pulley is less than the length that moves of the driven pulley. Hence, the belt must creep forward slightly relative to driven pulley rim. This motion of belt relative to driving and driven pulley due to unequal stretching of the two sides of the drive is known as creep. The effect of creep back on the driving pulley is to slow down the speed of the belt with respect to driving pulley and the effect of creep forward on the driven pulley is to slow down the speed of driven pulley. Thus the net effect of creep is to reduce the speed ratio than the theoretical expected. Difference between slip and creep. Creep is due to the elastic property of belt whereas, the conventional slip is due to insufficient frictional grip between the belt and pulley. However, the effect of the creep as well as slip is to reduce the speed ratio, and hence power transmission.
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    1.tubes is used to the heat and mass transfer 2.pipes is used to the mass transfer
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    In crown gear the pitch angle is 90 degree and in mitre gears the axes of gears are at 90 degree and gears are of same size.
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    For cutting right hand helical gear right side of milling table is tilted up from normal position by helix angle. For cutting left hand helical gear,right side of table needs to be tilted down at helix angle,all other settings remaining unchanged.
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    when a belt rotate through two pulleys, upper side of this drive will tight side and lower side will be slack side, now a certain portion of belt will pass through the area where it will change from tight side to slack side, then the length of that specific portion of the belt will expand and contract subsequently and a relative motion will happen between belt and pulley surface. This phenomenon is called creep of belt. This effects a slight reduction in velocity of follower pulley than driven one. proper selection of belt material and belt length can reduce this loss.
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    Hexagonal stands for head type. M for Metric. 12 mm diameter, 1.5 mm of thread pitch and 70 for the lenght (head thickness H, not couting)
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    From the album Watch Escapements Diagrams & Pictures

    The diagram above shows a typical watch escapement and gear train.
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    Supercharger , the engine booster. Why supercharger ?? How it works ??? Working diagram of supercharger. Classification of supercharger. History. Roots supercharger. Twin-Screw Supercharger. Centrifugal Supercharger. Drives used in Supercharger. Supercharger, An edge over turbocharger Nothing is perfect. Conclusion.
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    Governor regulates the speed by regulating the quantity of working agent of the prime mover. Flywheel function is to store the energy and gives up whenever required during a cycle.
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    [This blog is a repost from my other blog site, thought would be useful to Mechanical Engineering readers] Now every mechanical engineer uses CAD softwares. Weather software is SolidWorks, SolidEdge, Inventor or CATIA, Creo or UG-NX it has same theory of CAGD and Computational Geometry. Unforuntaly we in Mechanical Engineering does not have subjects to taught this in detailed. I hope this blog series helps you to understand What Lies Benith Your CAD Software !!! Mechanical CAD solid models are consisting of geometry and topology. Geometry by virtue of its visualization capability is easy to understand and comprehend. Topology is on the other hand, more of pure virtual concept hence many find it difficult to understand. In this article brief introduction to manifold topology is illustrated. Intended audience is new CAD developers or students of computational geometry. Geometry is a part of mathematics concerned with questions of size, shape, and relative position of figures and with properties of space. Many scientists have made contribution to its theory and lot has changed since Euler first laid foundation stone of Geometry. Following is brief review of the development. Euclid 300 BC, also known as Euclid of Alexandria, was a Greek mathematician and is often referred to as the Father of Geometry. His work “Elements” is the most successful textbook in the history of mathematics. In “Elements”, the principles of what is now called Euclidean geometry were deduced from a small set of axioms. The geometrical system described in the “Elements” was long known simply as geometry, and was considered to be the only geometry possible. Today, however, that system is often referred to as Euclidean geometry to distinguish it from other so-called Non-Euclidean geometries that mathematicians discovered in the 19th century. Euclid undertook a study of relationships among distances and angles, first in a plane (an idealized flat surface) and then in space. An example of such a relationship is that the sum of the angles in a triangle is always 180 degrees. Today these relationships are known as two- and three-dimensional Euclidean geometry. An essential property of a Euclidean space is its flatness. Important point to note is other spaces exist in geometry that are not Euclidean. For example, the surface of a sphere is not; a triangle on a sphere (suitably defined) will have angles that sum to something greater than 180 degrees. Next major contribution in Geometry came after around 2000 year by Leonhard Paul Euler (15 April 1707 – 18 September 1783). In 1736, Euler solved the problem known as the Seven Bridges of Königsberg. The city of Königsberg, Prussia was set on the Pregel River, and included two large islands which were connected to each other and the mainland by seven bridges. The problem is to decide whether it is possible to follow a path that crosses each bridge exactly once and returns to the starting point. It is not: there is no Eulerian circuit. This solution is considered to be the first theorem of graph theory, specifically of planar graph theory. In the processEuler also discovered the formula V − E + F = 2 relating the number of vertices, edges, and faces of a convex polyhedron, and hence of a planar graph. The constant in this formula is now known as the Euler characteristic for the graph (or other mathematical object), and is related to the genus of the object. The study and generalization of this formula, specifically by Cauchy and L'Huillier, is at the origin of topology. Next path breaking contribution was from Georg Friedrich Bernhard Riemann (September 17, 1826 – July 20, 1866) an extremely influential German mathematician who made important Non-Euclidean geometries. This discovery was a major paradigm shift in mathematics, as it freed mathematicians from the mistaken belief that Euclid's axioms were the only way to make geometry consistent and non-contradictory. Research on these geometries led to, among other things, Einstein's theory of general relativity, which describes the universe as non-Euclidean. The subject founded by his work is Riemannian geometry. Riemann found the correct way to extend into n dimensions the differential geometry of surfaces. The fundamental object is called the Riemann curvature tensor. For the surface case, this can be reduced to a number (scalar), positive, negative or zero; the non-zero and constant cases being models of the known non-Euclidean geometries. contributions to analysis and differential geometry. He was first one to discover Riemannian geometry is the branch of differential geometry that studies Riemannian manifolds, smooth manifolds with a Riemannian metric, i.e. with an inner product on the tangent space at each point which varies smoothly from point to point. This gives in particular local notions of angle, length of curves, surface area, and volume. From those some other global quantities can be derived by integrating local contributions. Riemannian geometry deals with a broad range of geometries categorized into two standard types of Non-Euclidean geometry,spherical geometry and hyperbolic geometry, as well as Euclidean geometry itself. Non-Euclidean geometry describes hyperbolic and elliptic geometry, which are contrasted with Euclidean geometry. The essential difference between Euclidean and non-Euclidean geometry is the nature of parallel lines. Euclid's fifth postulate, the parallel postulate, is equivalent to Playfair's postulate, which states that, within a two-dimensional plane, for any given line l and a point A, which is not on l, there is exactly one line through A that does not intersect l. In hyperbolic geometry, by contrast, there are infinitely many lines through A not intersecting l, while in elliptic geometry, any line through A intersects l. Another way to describe the differences between these geometries is as follows: Consider two straight lines indefinitely extended in a two-dimensional plane that are both perpendicular to a third line. In Euclidean geometry the lines remain at a constant distance from each other, and are known as parallels. In hyperbolic geometry they "curve away" from each other, increasing in distance as one moves further from the points of intersection with the common perpendicular; these lines are often called ultra parallels. In elliptic geometry the lines "curve toward" each other and eventually intersect. We started discussing how we end up in geometry discussion? I felt it was necessary to create basic understanding of historical development of Euclidean Geometry and Non-Euclidian geometry to understand next topics. As we saw earlier Euler was first one publish paper on topology in seven bridge problem demonstrating that it was impossible to find a route through the town of Königsberg that would cross each of its seven bridges exactly once. This result did not depend on the lengths of the bridges, nor on their distance from one another, but only on connectivity properties: which bridges are connected to which islands or riverbanks. In other words to solve many of geometric problems we do not need to know spatial information but what is requiring to be known is neighborhood or connectivity information termed as topology. Problems like a Möbius strip, an object with only one surface and one edge; such shapes are alos an object of study in topology. Jules Henri Poincaré (29 April 1854 – 17 July 1912) was a French mathematician and theoretical physicist, and a philosopher of science. As a mathematician and physicist, he made many original fundamental contributions to pure and applied mathematics, mathematical physics, and celestial mechanics. He was responsible for formulating the Poincaré conjecture, one of the most famous problems in mathematics. In his research on the three-body problem, Poincaré became the first person to discover a chaotic deterministic system which laid the foundations of modern chaos theory. He was a founder of topology, also known as “rubber-sheet geometry,” for its focus on the intrinsic properties of spaces. From a topologist’s perspective, there is no difference between a bagel (shape like torus or from Indian menu medu wada J ) and a coffee cup with a handle. Each has a single hole and can be manipulated to resemble the other without being torn or cut. Poincaré used the term “manifold” to describe such an abstract topological space. The simplest possible two-dimensional manifold is the surface of a soccer ball, which, to a topologist, is a sphere—even when it is stomped on, stretched, or crumpled. The proof that an object is a so-called two-sphere, since it can take on any number of shapes, is that it is “simply connected,” meaning that no holes puncture it. Unlike a soccer ball, a bagel is not a true sphere. If you tie a slipknot around a soccer ball, you can easily pull the slipknot closed by sliding it along the surface of the ball. But if you tie a slipknot around a bagel through the hole in its middle you cannot pull the slipknot closed without tearing the bagel. Euler- Poincaré equation Euler’s polyhedron formula was applicable to only simple polyhedron. This new equation from Poincaré provides relationship between topological elements for any single two-manifold body. V -E + F - Li = 2(1 - G) where, V : Number of vertices. E: Number of edges. F: Number of faces. Li: Number of interior loops. G: Genus, the number of closed paths on a surface which do not separate the surface into more than one region. Or, genus is the number of handles to be added to a sphere to make it homeomorphic to the object. Classification of manifolds · 0-manifold is just a discrete space. Eg Point in Cartesian space corresponds to vertex in topological space. Point or set of points are zero dimensional manifolds · 1-manifold is curve in Cartesian space. Eg circle, line, parabole b-spline curve (non intersecting) · 2-manfold is surface Cartesian space. Sphere (empty inside), torus, plane, cylinder, b-spline surface (if closed empty inside, orientable and non self-intersecting ) , circular disc · 3-manfold is 3 dimensional manifold. Eg Solid Objects, Solid Sphere, Solid Cylinder, Our universe J Two-dimensional manifolds were well understood by the mid-nineteenth century. But it remained unclear whether what was true for two dimensions was also true for three. Poincaré proposed that all closed, simply connected, three-dimensional manifolds—those which lack holes and are of finite extent—were spheres. The conjecture was potentially important for scientists studying the largest known three-dimensional manifold: the universe. Proving it mathematically, however, was far from easy. Most attempts were merely embarrassing, but some led to important mathematical discoveries, including proofs of Dehn’s Lemma, the Sphere Theorem, and the Loop Theorem, which are now fundamental concepts in topology. By the nineteen-sixties, topology had become one of the most productive areas of mathematics, and young topologists were launching regular attacks on the Poincaré. To the astonishment of most mathematicians, it turned out that manifolds of the fourth, fifth, and higher dimensions were more tractable than those of the third dimension. By 1982, Poincaré’s conjecture had been proved in all dimensions except the third. In 2000, the Clay Mathematics Institute, a private foundation that promotes mathematical research, named the Poincaré one of the seven most important outstanding problems in mathematics and offered a million dollars to anyone who could prove it. After nearly a century of effort by mathematicians, Grigori Perelman sketched a proof of the conjecture in a series of papers made available in 2002 and 2003. The proof followed the program of Richard Hamilton. Several high-profile teams of mathematicians have since verified the correctness of Perelman's proof. The Poincaré conjecture was, before being proven, one of the most important open questions in topology. It is one of the seven Millennium Prize Problems, for which the Clay Mathematics Institute offered a $1,000,000 prize for the first correct solution. Perelman's work survived review and was confirmed in 2006, leading to him being offered a Fields Medal, which he declined. The Poincaré conjecture remains the only solved Millennium problem. This article was written with the help of various sources of web sources, mainly Wikipedia. Intention is to explain interesting subject such as manifold which carries paramount importance in CAD development in less mathematical and elaborative manner. Research in Manifolds is as recent as 2006 and is one of the most studied area in mathematics.