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  1. 2 points
    Amazing work, Murat!!! it often happens like this because the hand calculation consider 1-D effect (only the moment area not 1-D) while the FEA consider 3-D effect. if you make the FEA becomes line/ 1-D (Ansys and SW could do this), the answer would be much closer to hand calc.
  2. 2 points
    the result some different between hand solve and computer solve. why the results are ddifferent. I couldn't understand. you can learn more information about singularity method from this link:
  3. 2 points
    Sirazz92 has given a fairly good answer. Pressure usually refers to a distributed external load applied to a body. Stress is the distributed internal loading associated with displacement under load. DrD
  4. 2 points
    1. What is the difference between scavenging and supercharging ? Ans: Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air. 2. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes.Ans: Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively. 3. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ?Ans: It will decrease. 4. Why entropy change for a reversible adiabatic process is zero ? Ans: Because there is no heat transfer in this process. 5. What are two essential conditions of perfect gas ? Ans: It satisfies equation of state and its specific heats are constant. 6. Enthalpy and entropy are functions of one single parameter. Which is that ? Ans: Temperature. 7. Why rate of condensation is higher on a polished surface compared to rusty surface ? Ans: Polished surface promotes drop wise condensation and does not wet the surface. 8. How much resistance is offered to heat flow by drop wise condensation ? Ans: Nil How are these questions - please do add comments and if you like them please do share this post on facebook, linkedin, twitter and google plus. 9. What is the relationship between COP of heating and cooling ? Ans: COP of heating is one(unity) more than COP of cooling. 10. How much is the work done in isochoric process ? Ans: Zero. 11. When maximum discharge is obtained in nozzle ? Ans: At the critical pressure ratio. 1. Under what condition the work done in reciprocating compressor will be least ? Ans: It is least when compression process approaches isothermal. For this purpose, attempts are made to cool the air during compression. 13. What is the difference between stalling and surging in rotary compressions ? Ans: Stalling is a local phenomenon and it occurs when How breaks away from the blades. Surging causes complete breakdown of flow and as such it affects the whole machine. 14. Why the electric motor of a fan with backward curved blades is never got overloaded under any condition ? Ans: The maximum power is consumed at about 70% of maximum flow in case'of fan with backward blades. For higher flow, power consumption gets lower. 15. Why the work per kg of air flow in axial flow compressor is less compared to centrifugal compressor for same pressure ratio ? Ans: Isentropic efficiency of axial flow compressor is higher. 16. What is the name given to portion of thermal energy to be necessarily rejected to environment ? Ans: Anergy. 17. What is pitting ? How it is caused ? Ans: Non uniform corrosion over the entire metal surface, but occuring only in small pits is called pitting. It is caused by lack of uniformity in metal. 18. What is caustic embrittlement ? Ans: It is the actual physical change in metal that makes it extremely brittle and filled with minute cracks. It occurs particularly in the seams of rivetted joints and around the rivet holes. 19. Which impurities form hard scale and which impurities soft scale ? Ans: Sulphates and chlorides of lime and magnesium form hard scale, and carbonates of lime and magnesium form soft scale. 20. What is the difference between hard water and soft water ? Ans: Hard water contains excess of scale forming impurities and soft water contains very little or no scale forming substances. 21. Which two elements in feed water can cause corrosion of tubes and plates in boiler ? ' Ans: Acid and oxygen in feed water lead to corrosion. 22. What should be done to prevent a safety valve to stick to its seat ? Ans: Safety valve should be blown off periodically so that no corrosion can take place on valve and valve seat. 23. Why large boilers are water tube type ? Ans: Water tube boilers raise steam fast because of large heat transfer area and positive water circulation. Thus they respond faster to fluctuations in demand. Further single tube failure does not lead to catastrophy. 24. What type of boiler does not need a steam drum ? Ans: Super-critical pressure boiler. 25. Why manholes in vessels are usually elliptical in shape ? Ans: Elliptical shape has minimum area of opening and thus plate is weakened the least. Further it is very convenient to insert and take out the cover plate from elliptical opening. 26. Low water in boiler drum is unsafe because it may result in overheating of water tubes in furnace. Why it is unsafe to have high water condition in boiler drum ? Ans: High drum level does not allow steam separation to be effective and some water can be carried over with steam which is not desirable for steam turbine. 27. Why boiler is purged everytime before starting firing of fuel ? Ans: Purging ensures that any unburnt fuel in furnace is removed, otherwise it may lead to explosion. 28. What is the principle of mechanical refrigeration ? Axis. A volatile liquid will boil under the proper conditions and in so doing will absorb heat from surrounding objects. 29. Why high latent heat of vaporisation is desirable in a refrigerant ? Ans: A high latent heat of vaporisation of refrigerant results in small amount of refrigerant and thus lesser circulation system of refrigerant for same tonnage. 30. What is the critical temperature of a refrigerant ? Ans: Critical temperature is the maximum temperature of a refrigerantrat which it can be condensed into liquid and beyond this it remains gas irrespective of pressure applied. 31. Maximum combustion temperature in gas turbines is of the order of 1100 to 10°C whereas same is around 00°C in I.C. engine ? Why ? Ans: High temperature in I.C. engine can be tolerated because it lasts for a fraction of second but gas turbines have to face it continuously which metals can't withstand. 32. Why efficiency of gas turbines is lower compared to I.C. engines ? Ans: In gas turbines, 70% of the output of gas turbine is consumed by compressor. I.C. engines have much lower auxiliary consumption. Further combustion temperature of I.C. engines is much higher compared to gas turbine. 33. What do you understand by timed cylinder lubrication ? Ans: For effective lubrication, lub oil needs to be injected between two piston rings when piston is at bottom of stroke so that piston rides in oi during upward movement. This way lot of lub oil can be saved and used properly. 34. What is IIUCR in relation to petrol engine ? Ans: HUCR is highest useful compression ratio at which the fuel can be used in a specific test engine, under specified operating conditions, without knocking. 35. In some engines glycerine is used in place of water for cooling of engine. Why ? Ans: Glycerine has boiling point of 90°C which increases its heat carrying capacity. Thus weight of coolant gets reduced and smaller riadiator can be used. 36. Why consumption of lubricating oil is more in two-stroke cycle petrol engine than four-stroke cycle petrol engine ? Ans: In two-stroke engine lub oil is mixed with petrol and thus some lub oil is blown out through the exhaust valves by scavenging and charging air. There is no such wastage in four stroke petrol engine. 37. As compression ratio increases, thermal n increases. How is thermal n affected by weak and rich mixture strength ? Ans: Thermal n is high for weak mixture and it decreases as mixture strength becomes rich. 38. How engine design needs to be changed to burn lean mixture ? Ans: Engine to burn lean mixture uses high compression ratio and the highly turbulent move¬ment of the charge is produced by the geometry of the combustion chamber. 39. Horse power of I.C. engines can be expressed as RAC rating, SAE rating, or DIN rating. To which countries these standards belong ? Ans: U.K., USA and Germany respectively. 40. What is the use of flash chamber in a vapour compression refrigeration cycle to improve the COP of refrigeration cycle ? Ans: When liquid refrigerant as obtained from condenser is throttled, there are some vapours. These vapours if carried through the evaporator will not contribute to refrigerating effect. Using a flash chamber at some intermediate pressure, the flash vapour at this pressure can be bled off and fed back to the compression process. The throttling process is then carried out in stages. Similarly compression process is also done in two separate compressor stages. 41. Why pistons are usually dished at top ? Ans: Pistons are usually hollowed at top to (i) provide greater spa'e for combustion, (ii) increase surface for flue gases to act upon, and (iii) better distribution of stresses. 42. What is the function of thermostat in cooling system of an engine ? Ans: Thermostat ensures optimum cooling because excessive cooling decreases the overall efficiency. It allows cooling water to go to radiator beyond a predetermined temperature. 43. What are the causes of failure of boiler tubes ? Ans: Boiler tubes, usually are made from carbon steel and are subject to (a) high rates of heat transfer,( b ). bending stresses due to uneven heating, especially at expanded or welded joints into headers or drums, © external erosion from burners and flue gas, (d) possible corrosion on the boiler side, and (e) occasional manufacturing defects. Failure may occur due to following reasons : (a) High thermal ratings may lead to rapid failure if the internal fluid flow is reduced for any reason. The resultant overheating leads to a failure by creep, characterised by the bulging of the tube with the eventual development of a longitudinal split. (b ) Fatigue cracking due to bending stresses occur. These are associated with change of section and/or weld undercut, where tubes are expanded or welded into headers. © Failure may arise due to overstressing of a reduced section of metal. (d) Sudden failure of the boiler tube due to corrosion arises from embrittlement of the carbon steel due to interaction between atomic hydrogen from the corrosion process and the iron carbide present in the steel. (e) Defects in tube manufacture, although far from being a regular occurrence, can be a cause of serious trouble. Lamination in boiler tubes or score marks arising from the cold drawing of tubes, give rise to premature failure and may promote corrosion at these regions. 44. What are the causes of failure of superheater tubes ? Ans: Superheater tubes are subjected to the most severe combination of stress, temperature and corrosive environment. In addition to high-temperature strength, resistance to corrosion is also important. For example, low-alloy ferritic steel such as -1/% Cr, 1% Mo would not be used at metal temperatures above 580°C because of inadequate resistance to corrosion and oxidation over a full service life of 100,000/150,000 hr. Failures in superheater tubes may arise from : (a) Prior fabrication history (b ) Faulty heat treatment © Consequences of welding (d) Overheating of the tube metal (e) Gas-side corrosion (f) Stress corrosion (austenitic steels). 45. Why supercritical boilers use less amount of steel compared to non-supercritical boilers ? Ans: Supercritical boilers do not head heavy drum for separation of steam from mixture of water and steam. 46. Out of electric heater and heat pump, which is economical in operation ? Ans: Heat pump. 47. Which furnace burns low-ash fusion coal and retains most of the coal ash in the slag? Ans: Cyclone furnace. 48. How the thickness of thermal boundary layer and thickness of hydrodynamic boundary layer related ? Ans: Ratio of their thickness = (Prandtl number)-1/3. 49. What is the effect of friction on flow of steam through a nozzle ? Ans: To decrease both mass flow rate and wetness of steam. 50. Why gas turbine power plant needs efficient compressor ? Ans: Because a large portion of turbine work is eaten away by compressor and its inefficiency will affect net power output and cost of generation. 51. Why rockets using liquid hydrogen have higher specific impulse compared to liquid hydrocarbon ? Ans: Liquid hydrogen has higher burning velocity. 52. Why axial flow compressor is preferred for gas turbines for aeroplanes ? Ans: Because it has low frontal area. 53. What is the effect of inter cooling in gas turbines ? Ans: It decreases thermal efficiency but increases net output. 54. Why iso-octane is chosen as reference fuel for S.I. engines and allotted 100 value for its octane number ? Ans: Iso-octane permits highest compression without causing knocking. 55. Why thermal efficiency of I.C. engines is more than that of gas turbine plant ? Ans: In I.C. engine maximum temperature attained is higher than in gas turbine. 56. Which are the reference fuels for knock rating of S.I. engines ? Ans: n-heptane and ISO-octane. 57. When effect of variations in specific heats is considered then how do maximum temperature and pressure vary compared to air standard cycle ? Ans: Temperature increases and pressure decreases. 58. Quantities like pressure, temperature, density, viscosity, etc. are independent of mass. What are these called ? Ans: Intensive properties. 59. The amount of radiation emitted per scm per sec is called .... ? Ans: Emissive power. 60. In convection heat transfer, if heat flux intensity is doubled then temperature difference between solid surface and fluid will ? Ans: Get doubled. 61. How you can define coal ? Ans: Coal is a naturally occurring hydrocarbon that consists of the fossilised remains of buried plant debris that have undergone progressive physical and chemical alteration, called coalification, in the course of geologic time. 62. Which pollutant is major greenhouse gas and what is its effect ? Ans: CO is major greenhouse gas and it traps the radiation of heat from the sun within earth's atmosphere. 63. In order to increase efficiency and reduce CO emissions and other emissions, clear coal technologies are receiving major attention. What are these ? Ans: (i) Advanced pulverised and pressurised pulverised fuel combustion. (ii) Atmospheric fluidised bed combustion and pressurised fluidised bed combustion. (iii) Supercritical boilers. (iv) Integrated gasification combined cycle systems. (v) Advanced integrated gasification, including fuel cell systems. (vi) Magneto hydrodynamic electricity generation. 64. What are the important operational performance parameters in design of fuel firing equipment ? Ans: Fuel flexibility, electrical load following capability, reliability, availability, and maintenance ease. 65. What is the differenc between total moisture and inherent moisture in coal ? Ans: The moisture content of the bulk as sampled is referred to as total moisture, and that of the air dried sample is called inherent moisture. 66. Proximity analysis of coal provides data for a first, general assessment of a coal's quality and type. What elements it reports ? Ans: Moisture, volatile matter, ash and fixed carbon. 67. Ultimate analysis of coal is elementary analysis. What it is concerned with ? Ans: Carbon, hydrogen, nitrogen, and sulphur in coal on a weight percentage basis. 68. Explain the difference between AFBC, BFBC, PFBC and PCFB in regard to fluidised bed technologies. Ans: AFBC (Atmospheric fluidised bed combustion) process consists of forming a bed of inert materials like finely sized ash or ash mixed with sand, limestone (for sulphur removal), and solid fuel particles in a combustor and fluidising it by forcing combustion air up through the bed mixture. The gas flows thorugh bed without disturbing particles significantly but gas velocity is high enough to support the total weight of bed (fluidisation). At slightly higher velocity excess gas passes through the bed as bubbles (fluidised bed) and gives the bed the appearance of a boiling liquid. Bubbling fluidised bed combustion (BFBC) has a defined height of bed material and operates at or near atmospheric pressure in the furnace. Pressurised fluidised bed combustion (PFBC) system operates the bed at elevated pressure. Exhaust gases have sufficient energy to power a gas turbine, of course, gases need to be cleaned. In fluidised combustion, as ash is removed some unburned carbon is also removed resulting in lower efficiency. In circulating fluidised bed combustion (CFBC) system, bed is operated at higher pressure leading to high heat transfer, higher combustion efficiency, and better fuel feed. Circulating fluidised beds operate with relatively high gas velocities and fine particle sizes. The maintenance of steady state conditions in a fast fluidised bed requires the continuous recycle of particles removed by the gas stream (circulating bed). The term circulating bed is often used to include fluidised bed sys¬tems containing multiple conventional bubbling beds between which bed material is exchanged. 69. What for Schmidt plot for is used in heat transfer problems ? Ans: Schmidt plot is a graphical method for determining the temperature at any point in a body at a specified time during the transient heating or cooling period. 70. In which reactor the coolant and moderator are the same ? Ans: Pressurised water reactor. 71. Which reactor has no moderator ? Ans: Fast breeder reactor. 72. What are thermal neutrons ? Ans: Thermal neutrons are slow neutrons (having energy below 1 eV) which are in thermal equilibrium with their surroundings. 73. What is big advantage of fast breeder reactor ? Ans: It has rapid self breeding of fissile fuel during the operation of the reactor, and thus, it offers about sixty times the output with same natural uranium resources through ordinary non-breeder nuclear reactor. 74. What is the purpose of biological shield in nuclear plants ? Ans: Biological shield of heavy concrete prevents exposure to neutrons, beta rays and gamma rays which kill living things. 75. Which two elements have same percentage in proximate and ultimate analysis of coal? Ans: Moisture and ash. 76. On which analysis is based the Dulong's formula for the heating value of fuel ? Ans: On ultimate analysis. 77. Which element causes difference in higher and lower heating values of fuel ? Ans: Hydrogen. 78. Which heating value is indicated by a calorimeter and why ? Ans: Gross heating value because steam is condensed and heat of vapour formed is recovered. 79. State the difference between ultimate and proximate analysis of coal ? Ans: In ultimate analysis, chemical determination of following elements is made by weight: Fixed and combined carbon, H, O, N, S, water and ash. Heating value is due to C, H and S. In proximate analysis following constituents are mechanically determined by weight. Moisture, volatile matter, fixed carbon and ash. Heating value is due to fixed carbon and volatile matter. 80. What is fuel ratio ? Ans: Fuel ratio is the ratio of its % age of fixed carbon to volatile matter. 81. How the analyses and calorific values of fuels can be reported ? Ans: It may be reported as (a) as received or fired (wet) basis (b ) dry or moisture free basis © combustible or ash and moisture free basis 82. What is the difference between nuclear fission and fission chain reaction. Ans: The process of splitting of nucleus into two almost equal fragments accompanied by re¬lease of heat is nuclear fission. Self sustained, continuing, sequence of fission reactions in a con¬trolled manner is fission chain reaction. 83. Explain difference between fissile and fertile materials. Ans: The materials which can give nuclear fission e.g. U 35, Pu 39, U 33 are fissile materi¬als. Fertile material itself is not fissionable, but it can be converted to a fissionable material by irradiation of neutrons in a nuclear reactor. 84. What do you understand by fuel cycle in nuclear plants ? Ans: Fuel cycle a series of sequential steps involved in supplying fuel to a nuclear power reactor. The steps include : Mining, refining uranium, fabrication of fuel elements, their use in nuclear reactor, chemical processing to recover remaining fissionable material, re-enrichment of fuel from recovered material, refabrication of new fuel elements, waste storage etc. 85. What is heavy water and what is its use in nuclear plants ? Ans: Water containing heavy isotopes of hydrogen (Deuterium) is known as heavy water. Heavy water is used as a moderator. Heavy water has low cross section for absorption of neutrons than ordinary water. Heavy water slows down the fast neutrons and thus moderates the chain reaction. 86. What is a converter reactor ? Ans: A reactor plant which is designed to produce more fuel than it consumes. The breeding is obtained by converting fertile material to fissile material. 87. Explain nuclear reactor in brief. Ans: A plant which initiates, sustains, controls and maintains nuclear fission chain reaction and provides shielding against radioactive radiation is nuclear reactor. 88. What is the difference between conversion and enrichment ? Ans: The process of converting the non fissile U 38 to fissile U-35 is also called "Conversion". The material like U 38 which can be converted to a fissile material by the neutron flux is called "fertile material". The conversion is obtained within the nuclear reactor during the chain reaction. Enrichment is the process by which the proportion of fissile uranium isotope (U-35) is increased above 0.7% (original % in natural uranium). The concentration of U-35 in the uranium hexafluoride is increased from the 0.7% in natural uranium to to 4%. This is called enrichment and is accomplished in an enrichment plant. 89. Disposal of radioactive waste materials and spent fuel is a major and important technology. How the waste radioactive material is disposed off ? Ans: Nonusable fission products are radioactive and take short/medium/long time for radioactive decay to reach safe level of radioactivity. Accordingly three methods of disposal are : (a) Zero or low radioactivity material is dispersed or stored without elaborate shielding. (b ) Medium radioactivity material is stored for short duration of about 5 years to allow decay of radioactivity. © High radioactive material. They are stored in water for several months to permit radioactive decay to an accepetable low level. 90. Which nuclear reactor uses water as a coolant, moderator and reflector ? Ans: Pressurised water reactor. 91. Which reactor produces more fissionable material than it consumes ? Ans: Breeder reactor. 92. Which reactor uses natural uranium as fuel ? Ans: Gas cooled reacator. 93. Which reactor uses heavy water as moderator ? Ans: CANDU. 94. Which reactor requires no moderator ? Ans: Breeder reactor. 95. Which reactor uses primary coolant as fluoride salts of lithium, beryllium, thorium and uranium ? Ans: Molten salt breeder reactor. 96. Why an increase in area is required to produce an increase of velocity in case of supersonic flow ? Ans: Increase in area for increase in velocity for supersonic flow is required because the density decreases faster than velocity increases at supersonic speeds and to maintain continuity of mass, area must increase. 97. Under what circumstances would there be an increase in pressure in a diver¬gent nozzle ? Ans: For subsonic flow at inlet section of a diffuser a lower velocity and higher pressure will exist at the exit section. For supersonic isentropic flow at the inlet section a higher velocity and lower pressure will exist at the exit but if a shock wave occurs in the diffuser then a higher pressure will exist at the exit. 98. Why water can't be used as refrigerant for small refrigerating equipment ? Ans: The refrigerant should be such that vapour volume is low so that pumping work will be low. Water vapour volume is around 4000 times compared to R- for a given mass. 99. Which parameter remains constant in a throttling process ? Ans: Enthalpy. 100. What is the difference between isentropic process and throttlinglprocess ? Ans: In isentropic process, heat transfer takes place and in throttling process, enthalpy before and after the process is same.
  5. 1 point
    kalachoe

    Non destructive testing

    How is it related to mechanical engineering? Isn't it more related to materials science?
  6. 1 point
    Iam very interested to study mechanical engineering in abroad. Can anyone please guide me
  7. 1 point
  8. 1 point
    Check out this website http://www.autozine.org/technical_school/chassis/tech_chassis.htm It lists different types of chassis including ladder type chassis
  9. 1 point
    DrD

    Triple Rocker

    In terms of four-bar linkages, most of them obey Grashof's Law, but evidently a few do not. Those that do not are called "non-Grashofian" or "triple rockers." I have a difficult time visualizing a triple rocker. The name implies that no link can turn a full revolution. Can any of you point me to an example, a problem discussion, or any other information regarding a Triple Rocker linkage? DrD
  10. 1 point
    John Nduli

    Software used for Analysis

    I've only used the solidworks FEA tool to do analysis on my bodies. Anyone have any other tools they've tried? Also a comparison of tools used would be nice.
  11. 1 point
    I've been wracking my brain with this. I would like to calculate the displacement caused by the force on beam. I've simulated this on Solidworks and then started to calculate it by hand. The problem in this is the overhanging parts that do not give the right answer when calculating by hands while compared on simulation answer. Have I typed wrong value at some point or have I used wrong values? Material is S235J2G3 and beam is HE 300B. Recommendations and suggestions are welcome.
  12. 1 point
    You know that diesel engine is the most appropriate choice of the engineers when it comes to drive heavy automobile like trucks, aircraft, ships etc. But what makes it so torque, is it the engine design, working cycle or something else. Please share your deep analysis to answer this questions
  13. 1 point
    assume theta is the angle at right pin support. http://www.mathalino.com/reviewer/strength-materials-mechanics-materials/solution-problem-696-697-beam-deflection-method-supe M = w (0.9) (0.45) = 121500 theta = (w L^3 / 24 EI) - (ML / 3 EI) - (ML / 3 EI) theta = [(300000 x 1.2^3) / ( 24 EI )] - 2 [(121500 x 1.2) / ( 3 EI )] theta = (21600 / EI) - (97200 / EI) = - 75600 / EI Your (right) end displacement should be delta = 0.9 theta = - 0.9 x 75600 / EI = - 68040 / EI E is based on material properties (for steel, E = 200 GPa = 200 x 10^9 Pa) I is the second moment area of the beam (for HE300B, I = 2.517 x 10^-4 m4) delta = - 1.3516 x 10^-3 m = - 1.3156 mm
  14. 1 point
    DrD

    Engine

    " A single valve actuates all the valves." This is a nonsense statement. "Qualitatively governed engine" but you say nothing about what this means. I have never heard of such. Also, I see no mention of overhead valve engines, a very important design type today. DrD
  15. 1 point
    View this quiz Production engineering quiz 1 lets check your knowledge on production engineering Submitter saurabhjain Time 10 minutes Type Graded Mode Submitted 05/03/2017 Category Mechanical Engineering Quiz  
  16. 1 point
    Pressure and stress are both force unit per area. Pressure applies to fluid (liquid or gas). It is a force per unit area applied perpendicular to a surface. Stress is more often used in solids, a force per unit area that can act parallel to a surface and/or perpendicular to it (vector).
  17. 1 point
    Are you sure that this question has any answer other than "enough"? Do you think that there is a general answer that covers all cases? I really doubt that, but I certainly cannot answer your question. I'm anxious for you to post an answer. DrD PS: The answer to the "why?" part is simply to do whatever needs to be done.
  18. 1 point
    DrD

    Technical Report Writing

    Technical reports, like most other written documents, begin with an Introduction, continue with the Main Discussion, and end with a Conclusion. In the Introduction, you describe the situation that motivates the document. Why is this being written? In the Main Discussion, you make your argument, analysis, data interpretation, or whatever you have done. In the Conclusion, you state your finaly results, the conclusions drawn from the material in the main body that (we hope) address the questions opened in the Introduction. That's about it. DrD
  19. 1 point
    Pressure is the force acting upon the surface of an body.(Action) Stress is the resisting force developed in a body when an external force acts on a body.(Reaction)
  20. 1 point
    mitesh bairwa

    Types of Hydraulic Turbines

    nice images
  21. 1 point
    What useful information are obtained from tensile test of ductile material You can answer this question. You can like the best answer. You can share the question You can get updates of new questions on Facebook linkedin twitter & google plus
  22. 1 point
    Define "Mechanical property" of engineering material State any 6 mechanical properties, give their definition and one example of material possessing the property You can answer this question. You can like the best answer. You can share the question You can get updates of new questions on Facebook linkedin twitter & google plus
  23. 1 point
    The mechanical properties of a material are those properties that involve a reaction to an applied load. The mechanical properties of metals determine the range of usefulness of a material and establish the service life that can be expected. Mechanical properties are also used to help classify and identify material. STRENGTH: The strength of a material is its ability to withstand an applied load without failure or plastic deformation.In machine design yield point or ultimate tensile / shear / compressive strength is used while designing. Stiffness: Stiffness is the rigidity of an object — the extent to which it resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Hardness: Hardness is a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied. Some materials (e.g. metals) are harder than others (e.g. plastics). Elasticity: the ability of an object or material to resume its normal shape after being stretched or compressed. On a stress-strain diagram it is considered to be below proportional limit.But widely this point is taken as the yield point by drawing a line offset by 0.2% parallel to the straight line until it intersects the curve. Plasticity: It describes the deformation of a (solid) material undergoing non-reversible changes of shape in response to applied forces. Brittleness: A material is brittle if, when subjected to stress, it breaks without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength.
  24. 1 point
    'less Maintenance' you are wrong dude... Diesel engine have more part than petrol engine....Diesel engine have high pressure fuel line, high pressure fuel pump, fuel filter.
  25. 1 point
    Jayesh Sharma95

    Types of Hydraulic Turbines

    What a nice explanation! Really very nice sir. Thanks a lot.
  26. 1 point
    Akhil Yathirajula

    Types of Hydraulic Turbines

    Supperb its helps 2 understand very easily
  27. 1 point
  28. 1 point
    I messed up diesel kerosene gasoline. In the forming process
  29. 1 point

    Version 1.1.0

    15,503 downloads

    A COMPLETE INSTRUCTOR AND STUDENT SUPPLEMENT PACKAGE - Continued These ppts are set of instructor and student supplements. . A FOCUS ON DIAGNOSIS AND PROBLEM SOLVING The primary focus of these ppts is to satisfy the need for problem diagnosis. Time and again, the author has heard that technicians need more training in diagnostic procedures and skill development. To meet this need and to help illustrate how real problems are solved, diagnostic stories are included throughout. Each new topic covers the parts involved as well as their purpose, function, and operation, and how to test and diagnose each system.
  30. 1 point
    Hardness: Hardness is the resistance of a material to localized deformation. The term can apply to deformation from indentation, scratching, cutting or bending. hardness commonly refers to a material's ability to penetrate softer materials. An object made of a hard material will scratch an object made of a softer material.In metals, ceramics and most polymers, the deformation considered is plastic deformation of the surface. For elastomers and some polymers, hardness is defined at the resistance to elastic deformation of the surface. The lack of a fundamental definition indicates that hardness is not be a basic property of a material, but rather a composite one with contributions from the yield strength, work hardening, true tensile strength, modulus, and others factors. Hardness measurements are widely used for the quality control of materials because they are quick and considered to be nondestructive tests when the marks or indentations produced by the test are in low stress areas. Toughness: The quality known as toughness describes the way a material reacts under sudden impacts. toughness is the resistance to fracture of a material when stressed. It is defined as the amount of energy that a material can absorb before rupturing, and can be found by finding the area (i.e., by taking the integral) underneath the stress-strain curve. It can be defined as the work required to deform one cubic inch of metal until it fractures. Toughness, often expressed as the Modulus of Toughness, is measured in units of joules per cubic meter (J/m3) in the SI system and pound-force per square inch (sometimes expressed as in-lb/in3) in US customary units. Toughness is measured by the Charpy test or the Izod test. Both of these tests use a notched sample. The location and shape of the notch are standard. The points of support of the sample, as well as the impact of the hammer, must bear a constant relationship to the location of the notch. Difference: The hardness of a metal limits the ease with which it can be machined, since toughness decreases as hardness increases Toughness is a combination of high strength and medium ductility. It is the ability of a material or metal to resist fracture, plus the ability to resist failure after the damage has begun. A tough metal, such as cold chisel, is one that can withstand considerable stress, slowly or suddenly applied, and which will deform before failure. Toughness is the ability of a material to resist the start of permanent distortion plus the ability to resist shock or absorb energy
  31. 1 point

    Version 1.0.0

    651 downloads

    This PDF contains Constants and other Formulaes of different subjects.. SI Multiples. Basic Units (distance, area, volume, mass, density). Mathematical Formulae. Applied Mechanics. Thermodynamics. Fluid Mechanics. Electricity. Periodic Table.
  32. 1 point
    Jeff Macaskill

    Why parabolic fins are preferred ?

    I believe it is because of the way the heat is dicipated. The center copper core is going to be the hottest. A passive heat exchanger that allows for the coldest air away from the heat source to be drawn in at the outside exchanging heat at the tips of the fins while warming up towards the center of the fins where the core is hottest. The parallel heat transfer works its way down to the center core and then out by the fan. Effective heat transfer because the exchange happens across the entire fin in the process...Also slight s shape creates slight disturbance to work on both sides of fin instead of favoring one side in the process.
  33. 1 point

    Version

    10,795 downloads

    The Internal-Combustion Engine in Theory and Practice Volume I : Thermodynamics, Fluid Flow, Performance Second Edition, Revised by Charles Fayette Taylor Professor of Automotive Engineering, Emeritus Massachusetts Institute of Technology
  34. 1 point
    Om Prakash

    Difference between pump and compressor

    Pumps can handle both liquids and gases. But Compressor can handle only the gases due the incompressible nature of liquids.................
  35. 1 point
    saurabhjain

    Difference between pump and compressor

    Basically a Pump is used for liquid or fluid to transform it to a much high pressure head while a Compressor is used for gases to transform from low to a much high pressure. From Mechanical Engineering point of view liquid is incompressible so Compressor cannot be used for liquid substances. Posted by AbdulQadir Abba Sheriff on linkedin
  36. 1 point
    hardness is a mechanical property by virtue of which a material resist scratches or indentation on its surface. toughness is also a mechanical property of a material by virtue of which it absorbs shock loading.
  37. 1 point
    saurabhjain

    Variable Frequency Drives

    Introduction What Is a Variable Frequency Drive? Adding a variable frequency drive (VFD) to a motor-driven system can offer potential energy savings in a system in which the loads vary with time. VFDs belong to a group of equipment called adjustable speed drives or variable speed drives. (Variable speed drives can be electrical or mechanical, whereas VFDs are electrical.) The operating speed of a motor connected to a VFD is varied by changing the frequency of the motor supply voltage. This allows continuous process speed control. Motor-driven systems are often designed to handle peak loads that have a safety factor. This often leads to energy inefficiency in systems that operate for extended periods at reduced load. The ability to adjust motor speed enables closer matching of motor output to load and often results in energy savings.
  38. 1 point
    As I can see - you have added the quiz , but all questions has been added in the description.. The steps are as below 1 create a new quiz and write description 2 add question and add all answers to the question 3 select the write answer of the above question 4 Add another question You need to edit the quiz....to get it approved Regards Saurabh
  39. 1 point
    dws123

    hydraulic pumps

    Hydraulic pumps are the part of the hydraulic system .it is used in various purpose in mechanical engineering and big machine.in term of mechanical engineering we used in high voltage machine.using this we increase power of machine and can lot of work in easy manner. so they are backbone of mechanical work.
  40. 1 point
    Abdulsamad Valiya

    hydraulic pumps

    Simply we can define Hydro static pumps are positive displacement pumps while hydrodynamic pumps can be fixed displacement pumps, in which the displacement (flow through the pump per rotation of the pump) cannot be adjusted, or variable displacement pumps, which have a more complicated construction that allows the displacement to be adjusted.
  41. 1 point
    DrD

    Variable Frequency Drives

    It is true that VFDs offer some real advantages for motor applications. It is also true that they can just about destroy your motor if not applied with great care. The switching that is used to synthesize the variable frequency AC waveform creates all manner of high frequency content on the output of the VFD. The cable connecting the VFD to the motor needs to be very carefully matched to the motor such that resonances are avoided. If resonance occurs, extremely high voltage can develop due to ringing of the output circuit, with the resulting destruction of the insulation in the cable and more importantly destruction of the motor insulation. This can require a very expensive motor replacement soon after the application of the VFD due to the insulation failure. So the long and short of it it, properly applied VFDs can be really very useful. Improperly engineers VFDs can be very costly and destructive. Oh, and they are always expensive, bulky, and heavy, if that matters.
  42. 1 point
    saurabhjain

    Variable Frequency Drives

    Applications Variable speed drives are used for two main reasons: • to improve the efficiency of motor-driven equipment by matching speed to changing load requirements; or • to allow accurate and continuous process control over a wide range of speeds. Motor-driven centrifugal pumps, fans and blowers offer the most dramatic energy-saving opportunities. Many of these operate for extended periods at reduced load with flow restricted or throttled. In these centrifugal machines, energy consumption is proportional to the cube of the flow rate. Even small reductions in speed and flow can result in significant energy savings. In these applications, significant energy and cost savings can be achieved by reducing the operating speed when the process flow requirements are lower. In some applications, such as conveyers, machine tools and other production-line equipment, the benefits of accurate speed control are the primary consideration. VFDs can increase productivity, improve product quality and process control, and reduce maintenance and downtime. Decreasing cost and increasing reliability of power semiconductor electronics are reasons that VFDs are increasingly selected over DC motors or other adjustable speed drives for process speed control applications. Motors and VFDs must be compatible. Consult the manufacturers of both the VFD and the motor to make sure that they will work together effectively. VFDs are frequently used with inverter-duty National Electrical Manufacturers Association (NEMA) design B squirrel cage induction motors. (Design B motors have both locked rotor torque and locked rotor current that are normal.) De-rating may be required for other types of motors. VFDs are not usually recommended for NEMA design D motors because of the potential for high harmonic current losses. (Design D motors are those that have high locked rotor torque and high slip.) Additional Benefits of VFDs In addition to energy savings and better process control, VFDs can provide other benefits: • A VFD may be used for control of process temperature, pressure or flow without the use of a separate controller. Suitable sensors and electronics are used to interface the driven equipment with the VFD. • Maintenance costs can be lower, since lower operating speeds result in longer life for bearings and motors. • Eliminating the throttling valves and dampers also does away with maintaining these devices and all associated controls. • A soft starter for the motor is no longer required. • Controlled ramp-up speed in a liquid system can eliminate water hammer problems. • The ability of a VFD to limit torque to a user-selected level can protect driven equipment that cannot tolerate excessive torque.
  43. 1 point
    saurabhjain

    Variable Frequency Drives

    I nduction motors, the workhorses of industry, rotate at a fixed speed that is determined by the frequency of the supply voltage. Alternating current applied to the stator windings produces a magnetic field that rotates at synchronous speed. This speed may be calculated by dividing line frequency by the number of magnetic pole pairs in the motor winding. A four-pole motor, for example, has two pole pairs, and therefore the magnetic field will rotate 60 Hz / 2 = 30 revolutions per second, or 1800 rpm. The rotor of an induction motor will attempt to follow this rotating magnetic field, and, under load, the rotor speed "slips" slightly behind the rotating field. This small slip speed generates an induced current, and the resulting magnetic field in the rotor produces torque. Since an induction motor rotates near synchronous speed, the most effective and energy-efficient way to change the motor speed is to change the frequency of the applied voltage. VFDs convert the fixed-frequency supply voltage to a continuously variable frequency, thereby allowing adjustable motor speed. A VFD converts 60 Hz power, for example, to a new frequency in two stages: the rectifier stage and the inverter stage. The conversion process incorporates three functions: • Rectifier stage: A full-wave, solid-state rectifier converts three-phase 60 Hz power from a standard 208, 460, 575 or higher utility supply to either fixed or adjustable DC voltage. The system may include transformers if higher supply voltages are used. • Inverter stage: Electronic switches - power transistors or thyristors - switch the rectified DC on and off, and produce a current or voltage waveform at the desired new frequency. The amount of distortion depends on the design of the inverter and filter. • Control system: An electronic circuit receives feedback information from the driven motor and adjusts the output voltage or frequency to the selected values. Usually the output voltage is regulated to produce a constant ratio of voltage to frequency (V/Hz). Controllers may incorporate many complex control functions. Converting DC to variable frequency AC is accomplished using an inverter. Most currently available inverters use pulse width modulation (PWM) because the output current waveform closely approximates a sine wave. Power semiconductors switch DC voltage at high speed, producing a series of short-duration pulses of constant amplitude. Output voltage is varied by changing the width and polarity of the switched pulses. Output frequency is adjusted by changing the switching cycle time. The resulting current in an inductive motor simulates a sine wave of the desired output frequency (see Figure below). The high-speed switching of a PWM inverter results in less waveform distortion and, therefore, lower harmonic losses. The availability of low-cost, high-speed switching power transistors has made PWM the dominant inverter type.