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engineering Ass26504 engineering Ass26504 Document Transcript

  • ASSIGNMENT/ASSESSMENT ITEM COVER SHEET Donald HEATHERStudent Name: FIRST NAME FAMILY / LAST NAME 2 0 0 8 8 0 9Student Number: Email: donald.heather@det.nsw.edu.au Course Code Course Title E D U C 6 5 0 4 Engineering Education Studies 1(Example) (Example) A B C D 1 2 3 4 Intro to UniversityCampus of Study: Callaghan (eg Callaghan, Ourimbah, Port Macquarie) 23/4/2012Assessment Item Title: CHALLENGETutorial Group (If applicable): Word Count (If applicable): 1499Lecturer/Tutor Name: Chris HollisExtension Granted: Yes No Granted Until:Please attach a copy of your extension approvalNB: STUDENTS MAY EXPECT THAT THIS ASSIGNMENT WILL BE RETURNED WITHIN 3 WEEKS OF THE DUE DATE OF SUBMISSION Please tick box if applicable Students within the Faculty of Business and Law, Faculty of Science and Information Technology, Faculty of Engineering and Built Environment and the School of Nursing and Midwifery: I verify that I have completed the online Academic Honesty Module and adhered to its principles Students within the School of Education: "I understand that a minimum standard of correct referencing and academic literacy is required to pass all written assignments in the School of Education; and I have read and understood the School of Education Course Outline Policy Supplement, which includes important information related to assessment policies and procedures. I declare that this assessment item is my own work unless otherwise acknowledged and is in accordance with the University’s academic integrity policy available from the Policy Library on the web at http://www.newcastle.edu.au/policylibrary/000608.html I certify that this assessment item has not been submitted previously for academic credit in this or any other course. I certify that I have not given a copy or have shown a copy of this assessment item to another student enrolled in the course. I acknowledge that the assessor of this assignment may, for the purpose of assessing this assignment: Reproduce this assessment item and provide a copy to another member of the Faculty; and/or Communicate a copy of this assessment item to a plagiarism checking service (which may then retain a copy of the item on its database for the purpose of future plagiarism checking). Submit the assessment item to other forms of plagiarism checking. I certify that any electronic version of this assessment item that I have submitted or will submit is identical to this paper version. DATE Turnitin ID:STAMP (if applicable) HERE Signature: _____________________________________________________________ Date: ___________________Insert this way
  • D. HEATHER - C2008809COUPLINGSCouplings are devices that are ulilised to connect two shafts together for the purpose of transmitting power.The purpose of couplings is to join two rotating pieces of equipment together allowing for a small amount ofmisalignment or end movement in each piece of equipment.Substantial savings can be made by selecting, installing and maintaining couplings correctly which will result inreduced maintenance costs and downtime.Shaft couplings have several purposes when used with machinery with the most common reasons being: To introduce mechanical flexibility To allow for misalignment of shafts To reduce shock transmission loads from one shaft to another To introduce protection against overloading of machinery parts To change the vibration characteristics of rotating unitsTypes of Couplings:Rigid:A rigid coupling can be used to connect two separate systems, such as a motor and a pump, or can beutilised to repair a connection within a single system. A rigid coupling could also be used to reduceshock and wear at a point where two shafts meet.Rigid couplings are used when it is necessary to have precise alignment and the ability to hold the twopieces of machinery securely in place. By aligning the two shafts and aligning them securely helps tomaximise performance and increase the expected life of the machine. Rigid coupling are available intwo types: i) Sleeve style – they are a single tube of material with an inside diameter that is the same size of the shaft. The sleeve slips over the shafts with screws that can be tightened to the top of each shaft. Page |2
  • D. HEATHER - C2008809 ii) Clamped rigid coupling – they are made with two parts that fit together around the shaft and form a sleeve. They are secured by screws which pass all the way through the coupling and into the second half to hold it rigidly in place. They are used to connect shafts that are fixed in place.Constant-velocity couplings:Constant velocity couplings allow a shaft to transmit power at varying angles and at a constant speed.The constant velocity coupling was used in drive trains in cars with front wheel drive.The Thompson Coupling consists of two cardan joints assembled within each other eliminating the useof a shaft, along with a control yoke that geometrically constrains their alignment. The control yokehas minimal inertia and generates virtually no vibration.Shaft alignment and coupling setup need to be disconnected and connected easily. There should besome allowance for misalignment between the two adjacent shaft rotation axes. Couplingmaintenance should be relatively easy by performing visual inspections, cleaning couplings regularlyand checking for signs of wear. Detection of potential coupling failure would be abnormal noise,vibration and an indication of lubricant leakage.CouplingThe coupling will fit over the shaft and be bolted together with M12 bolts. The reason is it needs towithstand a lot of vibration. The coupling will be used to transverse power from an electric motor tocentrifugal pump to pump water for use in an agriculture farm. The precise alignment is necessary tominimise vibration and maintenance. Page |3
  • D. HEATHER - C2008809Incorrectly aligned shafts.The alteration to radius on the coupling body is to allow for more stress and strain to be absorbed.The radius will assist the coupling by reinforcing a weak point. When a coupling is manufactured itneeds to be designed to maximise its ability to transverse power without failure. The radius isdesigned to allow the component to have more strength at a point that would be weak.There are several methods which could be used to manufacture the coupling.Machining:The coupling could be machined out of a billet. The process would need to be accurate and finetolerances would need to be maintained. The emergence of Computer Numerical Control is how itwould need to be produced for it to be a viable proposition cost wise. The machine would cut theprofile and drill and bore the hole in one process. The advent of technology would also allow themachine to drill the four 12mm diameter holes while the coupling is in the machine. The chuck hasthe ability to rotate at a given angle anywhere within the 360° rotation utilising a universal head todrill holes. The keyway could be broached out to size.Drop Forging:The coupling could be drop forged to shape. If a material is worked by the application of localisedcompressive forces, it is said to have been forged.“Drop Forging is “it may be squeezed or hammered in between special dies so that the metal flowsand takes up the shape of the die cavity, Shlenkler 1986. Page |4
  • D. HEATHER - C2008809The machines utilise 2 dies that take up the shape of the coupling and have a capacity of up to 10 MN.Drop forging is a mass production process using one die or a series of dies. Dimensional accuracy isnot high with drop forging however the couplings outside surfaces do not need machining. The borewill be machined, holes drilled and keyway cut. When a components finished size is known theforging could allow for balance by allowing the mass taken out by the keyway being applied exactlyopposite. This will result in the coupling when completed being balanced which will assist in lessvibration when turning at high speed.Material:The material I would use mild steel. Mild steel „contains 0.15 – 0.3%C. Wrought forms are used asRSJ and other structural members, shafting, levers and various forgings”. Higgins 1977.Mild steel is readily available and reasonably cheap compared to other materials. Mild steel is easilyformed, machined and does not harden much if cooled quickly, and is quite ductile. Copeland 2000It should be noted that mild steel, like all steels (except stainless steels), readily corrode, and that theproduct of corrosion (commonly known as rust) is porous, thus promoting further corrosion.The radius is being applied to the coupling to add strength at the intersection of the two diameters.When two diameters meet which have been machined the flow lines of the material in this case “fibre”is cut. This reduces the strength of the coupling and is a weak point at which the material may fail dueto stresses. The coupling could develop cracks at this point running along the flow lines.“High stress concentration is likely to cause failure along exposed fibres and so weaken thecomponent” Higgins 1977 Page |5
  • D. HEATHER - C2008809The material being drop forged will have a radius at this point. The material has been upset from barstock with the result being flow lines following the contour of the coupling. This result is the radius atthe intersection of the two diameters being strengthened.Billet or bar stockFlow lines following outside profile.Section displaying flow lines. Page |6
  • D. HEATHER - C2008809Conclusion:By adding a radius at the point where diameters meet strengthens components so they will be able tobe utilised for longer periods. This results in less maintenance of the component, ability of thecomponent to withstand greater forces for longer periods and less down time replacing the component.The time it would take to connect the coupling correctly and fixing both components securely inposition would offset costs utilising different couplings or methods to transmit power. The finalprocess could be trying to minimise corrosion by painting the coupling, and installing a cover toprotect the coupling from direct weather conditions. This could also be a safety measure so norotating parts of the machinery are exposed. BibliographyCopeland, P. L. (2000). Engineering Studies, The Definitive Guide. Australia; Anno Domini Pty Lty.Higgins, R. A. (1977). Properties of Engineering Materials. Great Britain; The Chaucer Press.Schlenker. B. R. (1986). Introduction to Material Science. [SI. ed]. Milton; The Jacaranda Press. Page |7
  • D. HEATHER - C2008809Shaft WasherNut Key Page |8
  • D. HEATHER - C2008809Coupling Page |9
  • D. HEATHER - C2008809Cross section 3D Drawing P a g e | 10
  • D. HEATHER - C2008809Drawing displaying radii. P a g e | 11