Design of Shaft | Basis of rigidity

Design of Shaft | Basis of rigidity DESIGN OF SHAFT ON THE BASIS OF RIGIDITY AND STRENGTH CALCULATION AND ANGLE OF TWIST Design of Shaft: †¢ A shaft is a rotating member usually of circular crossection (solid or hollow), which is used to transmit power and rotational motion. Axles are non rotating member. †¢ Elements such as gears, pulleys (sheaves), flywheels , clutches , and sprockets are mounted on the shaft and are used to transmit power from the driving device(motor or engine) through a machine. †¢ The rotational force (torque) is transmitted to these elements on the shaft by press fit, keys, dowel, pins. †¢ The shaft rotates on rolling contact or bush bearings. †¢ Various types of retaining rings, thrust bearings, grooves and steps in the shaft are used to take up axial loads and locate the rotating elements. Design of Shafts on the Basis of Rigidity: †¢ Shafts must be rigid enough to avoid excessive deflection †¢ Two types of rigidity:  § Torsional rigidity  § Lateral rigidity Torsional Rigidity: †¢ Important for camshafts where timing of the valves are important †¢ Estimate the total angle of twist in radians †¢ Use torsion equation Lateral Rigidity: †¢ Important for  § Transmission shafting  § Shafts running at high speed †¢ Lateral deflection must be minimised to avoid:  § Gear teeth alignment problems  § Bearing related problems †¢ The lateral deflection (y) and the slope (ÃŽ ¸) may be determined by equations from the strength of materials Design of Shafts Based on Strength: Stresses in Shafts: †¢ Shear stresses due to torsional load †¢ Bending stresses due to the forces coming from gears, pulleys, etc. †¢ Stresses due to combined torsional and bending loads Angle of twist for circular members: Angle of twist : When one end of shaft is fixed and the other end is twisted, the angle twisted is the angle of twist. Find the relative rotation of section B-B with respect to section A-A of the solid elastic shaft as shown in the when a constant torque T is being transmitted through it. The polar moment of inertia of the cross-sectional area J is constant. Concepts involved: Angle of twist in circular members Formulae used: ÃŽ ¸=∠« Txdx/JG Where, φ= Angle of twist Tx = torque at distance x Jx = polar moment of area at distance x G = Shear modulus Solution: Step 1: Here neither torque nor J changes with x so, Tx = T and Jx = J And limit is between 0 to L so we get: ÃŽ ¸=TL/JG Note: In applying the above equation, note particularly that the angle φ must be expressed in radians. Also observe the great similarity of this relation equation Δ =PL/AE, for axially loaded bars. Here φ ⇔ Δ T⇔ P, J⇔ Α, and G⇔ E. By the analogy, this equation can be recast to express the torsional spring constant, or torsional stiffness, kt as Kt = T/ÃŽ ¸ = JG /L [N-m/rad] This constant torque required to cause a rotation of 1 radian, i.e., φ = 1. It depends only on the material properties and the size of the member. As for axially loaded bars, one can visualize torsion members as springs. The reciprocal of kt defines the torsional flexibility ft. Hence, for a circular solid or hollow shaft. ft = 1/kt = L / JG [ rad/N-m] This constant defines the rotation resulting from application of a unit torque, i.e., T = 1. On multiplying by the torque T, one obtains the current equation . Shaft Design: Shaft Design consists primarily of the determination of the correct shaft diameter to ensure satisfactory strength and rigidity when the shaft is transmitting power under various operating and loading conditions. Shafts are usually circular in cross section, and may be either hollow or solid. Design of shafts of ductile materials, based on strength, is controlled by the maximum shear theory. And the shafts of brittle material would be designed on the basis of the maximum normal stress theory. Various loads subjected on Shafting are torsion, bending and axial loads. Torsional stresses: (Ï„) The Torsional formula is given by: T/J=G ÃŽ ¸/L=Ï„/r Here T=torque or Torsional moment, N-mm J=polar moment of inertia, mm4 = Ï€ d4/32 ,Where d is the solid shaft diameter. = Ï€( do 4- d i 4 ) /32 Where do and di are outer and inner diameter of the hollow shaft respectively. G=Modulus of elasticity in shear or modulus of rigidity, MPa ÃŽ ¸=Angle of twist, radians l= Length of shaft , mm r= Distance from the Neutral axis to the top most fibre , mm = d/2 (For solid shaft) = do /2(For hollow shaft) Shear (Ï„) stress on the outer surface of a shaft, for a torque (T) : For solid circular section:  · Ï„ = Tr / J = 16T / Ï€ d3 For hollow circular section:  · Ï„ = Tr / J =16T do / Ï€ do 4- d i 4 ) Design of Shafts for Fatigue (Fluctuating Loads): †¢ Shafts are generally subjected to fluctuating torques and bending moments may fail due to fatigue †¢ Combined shock and fatigue factors must be taken into account †¢ Modify the equivalent twisting and bending moments. Power Transmitting Shaft: * Shaft Design consists primarily of the determination of the correct shaft diameter to ensure satisfactory strength and rigidity when the shaft is transmitting power under various operating and loading conditions. Shafts are usually circular in cross section, and may be either hollow or solid. * Design of shafts of ductile materials, based on strength, is controlled by the maximum shear theory. And the shafts of brittle material would be designed on the basis of the maximum normal stress theory. * Various loads subjected on Shafting are torsion, bending and axial loads. Crank Shaft: * A crankshaft is used to convert reciprocating motion of the piston into rotary motion or vice versa. The crankshaft consists of the shaft parts, which revolve in the main bearings, the crank pins to which the big ends of the connecting rod are connected, the crank arms or webs, which connect the crankpins, and the shaft parts. The crankshaft, depending upon the position of crank, may be divided into the following two types. * The crankshaft is the principal member of the crank train or crank assembly, which latter converts the reciprocating motion of the pistons into rotary motion. It is subjected to both torsional and bending stresses, and in modern high-speed, multi-cylinder engines these stresses may be greatly increased by resonance, which not only renders the engine noisy, but also may fracture the shaft. In addition, the crankshaft has both supporting bearings (or main bearings) and crankpin bearings, and all of its bearing surfaces must be sufficiently large so that the unit bearing load cannot become excessive even under the most unfavorable conditions. At high speeds the bearing loads are due in large part to dynamic forces-inertia and centrifugal. Fortunately, loads on main bearings due to centrifugal force can be reduced, and even completely eliminated, by the provision of suitable counterweights. All dynamic forces increase as the square of the speed of rotation. (i.e. FDynamic↑â‡⠀™Speed2↑) REFRENCES: * Engineering mechanics static and dynamics my A.K. Tayal * www.sciencedirect.com * Mechaical Sciences by G.K. LAL * www.physicsclassroom.com

Computer Games †Good or Bad? Essay

Before we decide whether or not computer/video games are bad, there are many facts and opinions to consider. For example, many people feel that these games are too violent and that they cause an undervelopment in the frontal lobe. Others feel that games are helpful and educational. There is also a health concern. According to Professor Ryuta Kawashima, â€Å"The importance of this discovery cannot be underestimated. There is a problem we will have with a new generation of children – who play computer games – that we have never seen before. The implications are very serious for an increasingly violent society and these students will be doing more and more bad things if they are playing games and not doing other things like reading aloud or learning arithmetic. † I do not agree with this statement fully, though I can understand that it does occur in some cases. I love playing computer and video games. When I was younger I used to play a James Bond game with my friends. We also played Mortal Kombat and Street Fighter. I used to love those games, and I remember making them â€Å"turn off the blood† because I ddin’t like that side to it. I still play video games, and though they may include shooting, fighting and other violence, you don’t see me beating up somebody because of a video game. I do know that there are some bad people in the world who have hurt someone because they were influenced by violent games. Another concern is the underdevelopment of the frontal lobe. As written by Tracy McVeigh, education editor, â€Å"Whenever you use self control to refrain from lashing out or doing something you should not, the frontal lobe is hard at work. Children often do things they shouldn’t because their frontal lobes are underdeveloped. The more work done to theicken the fibres connecting the neurons in this part of the brain, the better the child’s ability will be to control their behaviour. The more the area is stimulated, the more these fibres will thicken. † I think I agree with this statement, becasue I have seen the behaviour of the people around me, they seem out of control sometimes. They speak before they think, they fight constantly and are always in other people’s faces. One guy states â€Å"I’m not going to argue that violent entertainment is harmless. I think it has helped inspire some people to real-life violence. I am going to argue that it’s helped hundreds of people for every one it’s hurt, and that it can help far more if we learn to use it well. I am going to argue that our fear of ‘youth violence’ isn’t well-founded on reality and that the fear can do more harm than the reality. We act as though our highest priority is to prevent our children fron growing up into murderous thugs – but modern kids are far more likely to grow up too passive, too distrustful of themselves, too easily manipulated†. I agree more with him than Professor Kawashima, because I don’t find that video games influence EVERYONE to be violent. I feel that they release anger by hurting fictional characters on a screen rathern than real-life people and animals. Professor Angela McFarlane says â€Å"Adventure, quest and simulation type games have a lot of benefit – they’re quite complex and create a context in which children can develop important skills†¦We’re not advocating arcate, shot-the-baddie type games†¦Now that’s interesting when the stereotype is that children play on the computer exclusively on their own. Teachers and parents then broke that down into skills of negotiation, planning, strategic thinking and decision-making. † I feel that if television can teach us, so can video games. Video and computer games can cause health problems. In every instruction book for games there are warnings. Some people suffer from a condition called Photosensitive Epilepsy. As said by Professor Graham Harding, â€Å"Photosensitive epilepsy is best defined as a tendency to recurrent convulsions, precipitated either by flashing lights or patterns. † I have only ever had one fit in my life, when I was younger. I was diagnosed with occipital epilepsy. I’ve always played video games and hadn’t had a problem. We got a PS2 (PlayStation 2) for Christmas last eyar, and while I was playing I felt dizzy. This occured with every game on PS2 except Buzz, though it’s a quiz game and doesn’t have all those flashy graphics. I can play on the Computer, my Nintendo DS and my GameCube without a problem, it seems to just be the PS2. I agree that video games can cause health problems, though if you do everything you need to (e. g. not playing a certain game, having a break etc.) you should be alright. Computer games – are they good or bad? In my opinion, I think that they are enjoyable, though they aren’t for some people. Those people who can be so cruel as to murder an innocent kitten or beat up a person due to these games are the reasons why there are doubts about computer and video games. Computer games are both good and bad. Good because they are enjoyable and can be educational, though bad because they cause some violence. Just remember, more people kill in the name of God than violent computer games.

Fern Hill Essay - 1541 Words

The poem ‘Fern Hill† by Dylan Thomas clearly illustrates the content and joy of a young person’s connections to nature while playing on his farm. This character, who is probably a boy, has recounted some of his good times while living on the farm as a child. This child has experienced an endless landscape of a beautiful and vast nature through the existence of plants, animals, the sky, rivers and stars. The abundance of nature and life creates a sense of reality within the poem and appreciation for some of the fundamental things in the world. â€Å"Fern Hill† also presents the same view through the eyes of an adult who reflects on his past and the joys of the great things he or she has experienced. This poem helps one appreciate the nature†¦show more content†¦One quote recites â€Å"And wake to the farm forever fled from the childless land./Time held me green and dying/Though I sang my chains like the sea,† (Thomas ll 51-53). The reference t o â€Å"childless land,† obviously means there are no longer any children on the farm, and thus, the speaker has become an adult and has grown up. This implies that nature will always be around even as one ages. This ties into the meaning of the poem, which is appreciate nature while you are able to. The word â€Å"dying,† refers to aging and â€Å"green,† refers to lively and gratified and feeling young in a sense. Nature has brought a joy to the speaker’s life that is unmatched in quality and memorable experiences. It is important to lead an enjoyable life and value the joys that nature brings, as the older we become, the more chained, and limited we will become. Imagery of getting older and of dying creates a realization that we might not always have the time to enjoy nature. Uses of imagery depicting aging and nearing death are substantial to demonstrating nature’s indifference to time, which ties in to the use of symbols to help define the cre ation of life over time. Symbolism is another literary term used effectively in this poem. The sun plays a large role in the poem â€Å"Fern Hill† as it is a symbol of life. It is mention in stanzas two to five and is compared to youth andShow MoreRelated Poetic Analysis of Fern Hill Essay960 Words   |  4 PagesPoetic Analysis Fern Hill Dylan Thomass poem Fern Hill represents the passage of one mans life from boyhood to adulthood and the realization of his mortality. The speaker in this poem uses expressive language and imagery to depict a tale of growing up. The use of colour adds life and character to people and abstract ideas. He looks up to Time (313) as an authority figure who has strict control of his life, and with descriptions of biblical figures we can presume that he is aRead More Time in Thomas’ Fern Hill and Cummings’ anyone lived in a pretty how town3549 Words   |  15 Pagespoetry. In Thomas’ Fern Hill and Cummings’ anyone lived in a pretty how town, both modern poets utilize a juxtaposition of paradoxes to express the irrevocable passage of time and the loss of innocence attributed to it. While Thomas projects his mature feelings into a nostalgic site of his childhood, Cummings takes a more detached approach by telling a seemingly trivial, paradoxical story of noone and anyone, which through negation tells a universal life story. Fern Hill is a personal accountRead MoreA Look into the Photojournalistic Works of Ara Guler1473 Words   |  6 Pagesphotojournalism, and how photojournalism relates to art. There is much controversy in defining art because there are so many different categories to consider . There are several articles and essays written on the subject, some with a more traditional view and some with a more open view. Two of the most notable essays come from, one Rob Sharry about Eugene Delacroix’s more conservative definition of art, and F. Wellington Rucksthul , who carries a more open interpretation. According to Rob Sharry EugeneRead MoreLiterary Versatility And Legacy Of Dylan Thomas2387 Words   |  10 Pageshis death by swelling his liver, and also contributed to his poetry.[endnoteRef:5] [2: Walford Davies, Writers of Wales: Dylan Thomas (Cardiff, Wales: University of Wales Press, 2014.) 32.] [3: Jacob Korg, Dylan Thomas: A Collection of Critical Essays (Englewood Cliffs: Prentice-Hall, 1966.) 11-14.] [4: Korg 20-21.] [5: ?Dylan Thomas,? Poetry Archive, web, 22 June 2002.] Thomas had a very intriguing writing style by having a cosmic view of mysticism in his writings, especially in his earlyRead MoreExploring Machu Picchu1908 Words   |  8 Pagesbeen rated as one of the New Seven Wonders of the World. It is treasured by UNESCO, and continues to inspire and awe millions of people. A few years ago, I took my daughter to see the site since I wanted to give her a special treat. The following essay describes the history and beauty of the place so that I can, to some extent, relay my indescribable feelings of a magical place to the reader. Macchu Picchu is a pre-Columbian 15th century Inca site that is located in the Cusco region of Peru in SouthRead MoreThe Importance of Vital Signs in Contemporary Nursing Practice2278 Words   |  10 PagesThis essay aims to provide a discussion of vital signs and how they are relevant to contemporary nursing practice. This is done by; †¢ Discussing what vital signs are and when are they used in practice. †¢ Why are vital signs relevant to contemporary nursing practice? †¢ How the skills are performed with the consideration of the NMC (2008) code of conduct. †¢ Discussing potential risk issues associated with using automated blood pressure/pulse machine in relation to contemporary practice. †¢ SummaryRead MoreThe Natural World In Anne of Green Gables Essay examples2319 Words   |  10 Pagesand even so far as to become nature. Irene Gammel in her essay, Embodied Landscape Aesthetics In Anne of Green Gables, points out a significant scene, where Anne imagines that she is the wind. â€Å"Returning to Green Gables after apologizing to Mrs. Rachel Lynde, Anne Shirley in the epigraph immerses herself in nature, using the landscape as raw material for aesthetic transformation, as she imagines being the wind, gyrating through trees and ferns and clover and flowers, while also creating a narrativeRead More Virginia Woolfs Jacobs Room - Jacob Flanders, Many Things to Many Readers4383 Words   |  18 Pagestwo low chairs. There were yellow flags in a jar on the mantelpiece; a photograph of his mother; cards from societies with little raised crescents, coats of arms, and initials; notes and pipes; on the table lay paper ruled with a red margin B, an essay, no doubt Does Hi story consist of the Biographies of Great Men? There were books enough; very few French books; but then any one whos worth anything reads just what he likes, as the mood takes him, with extravagant enthusiasm. Lives of the DukeRead MoreEssay on Silent Spring - Rachel Carson30092 Words   |  121 Pagesoffprint from Gales For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare Contrast, What Do I Read Next?, For Further Study, and Sources.  ©1998-2002;  ©2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design ® andRead MoreAmerican Literature11652 Words   |  47 PagesEnlightenment American Renaissance/Romanticism Gothic Realism Naturalism Modernism Harlem Renaissance Postmodernism Contempora ry Puritan Times period of American Literature - 1650-1750 Content: ï‚ · ï‚ · ï‚ · errand into the wilderness be a city upon a hill Christian utopia Genre/Style: ï‚ · ï‚ · ï‚ · ï‚ · ï‚ · sermons, diaries personal narratives captivity narratives jeremiads written in plain style Effect: ï‚ · ï‚ · instructive reinforces authority of the Bible and church Historical Context: ï‚ · ï‚ · a

The Assassination Of John F. Kennedy - 3922 Words

Possibly the greatest unsolved mystery of the 20th century is the assassination of John Fitzgerald Kennedy, the 35th President of the United States. Many people have theorized to the exact nature of JFK’s death but no one can seem to agree, but what most people do agree on is that the Warren Commission’s findings were wrong. Fifty years after the incident, 61% of Americans believe that Lee Harvey Oswald was not the only person involved in the successful assassination attempt. (Majority in U.S. Still Believe JFK Killed in a Conspiracy) In the assassination of JFK, the evidence points toward the conclusion that a conspiracy to assassinate the President of the United States by Lyndon B. Johnson, carried out by Lee Harvey Oswald and covered†¦show more content†¦On June 30, 1961 JFK pledges to land a man on the moon by the end of the decade. Then in April of 1962 â€Å"US Steel announces that it is raising prices just weeks after President Kennedy convinced the ste el workers union to temper its wage demands. Kennedy’s anger with US Steel is reported in the press and Attorney General Robert Kennedy adds further to business anxieties by convening a grand jury investigation of the steel giant. The stock market will fall in the following weeks, climaxing with a 6% drop on 28 May.† (Shmoop Editorial Team) The next step in understanding the assassination of JFK is to understand anyone who would have wanted JFK dead or would benefit from his death. The first name on a list of possible enemies of JFK would be Lyndon B. Johnson, JFK’s Vice President. In 1963, LBJ did not see eye to eye with Kennedy and he knew that Kennedy was going to leave him off the ballot in the upcoming presidential election. (JFK Had Long List of Enemies) Next are the Cuban Freedom Fighters, who after the Bay of Pigs were abandoned and left to be executed by Castro’s henchmen. (JFK Had Long List of Enemies) Next is Fidel Castro, JFK and the CIA had pl otted to have Castro assassinated and failed, so it is safe to say that Castro would have known of these attempts. (JFK Had Long List of Enemies) After that is the American Mafia, Bobby Kennedy had been tirelessly