Case study ass3 6505
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Case study ass3 6505 Case study ass3 6505 Document Transcript

  • ASSIGNMENT/ASSESSMENT ITEM COVER SHEETStudent Name: Donald HEATHER 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 5 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)Assessment Item Title: Case Study Due Date/Time:Tutorial Group (If applicable): Word Count (If applicable):Lecturer/Tutor Name: A FirthExtension 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 - C2008809 PRINCIPLES OF FLUID MECHANICSARCHIMEDES PRINCIPLEArchimedes principle explains buoyancy. If an object is placed in water and “weighted” it will register asmaller value than if weighted in air. (Copeland, 2005) The upward force of the water partially balancesthe weight force. The force exerted by the water on the object is the buoyancy force, and is dependenton the density of the fluid and the volume of the submerged object. The buoyancy force is equal in valueto the weight of displaced fluid by the object.Archimedes principle is used to calculate the specific gravity of objects.The formula: Specific Gravity: weight of object in air _______________________________ Weight loss when submerged in waterPASCAL’S PRINCIPLEPressure at the bottom of a container is greater than the top, and is independent of the shape of thecontainer. Pressure is also the same at all points at the same depth. Increasing pressure at the surfacewith a piston, forcing it into the liquid will increase the pressure throughout the liquid.This situation is known as Pascal’s principle and is stated as follows: Pressure applied to an enclosed liquidis transmitted undiminished to every point in the fluid and to all the walls of the container. (Copeland,2005) An example of Pascal’s principle Page | 2
  • D. HEATHER - C2008809HISTORY OF BRAKESThe early braking systems were used to stop vehicles with steel rimmed wheels. A curved block made outof wood was manipulated against the wheel by leverage systems. The brake shoe was the normal way ofbraking in a steam locomotive or a horse drawn vehicle.External spoon brakeIn 1895 the Michelin brothers replaced the steel rim with pneumatic rubber tyres. A new method was toapply the force to the axle or to a drum on the axle. This was operated by the driver depressing a pedal.The band and the drum had to be continuously replaced due to poor friction quality which led to areplacement friction material. Herbert Frood processed an asbestos fabric in 1908 which was used as areplacement.The next development in 1902 was drum brakes by Louis Renault who designed an internal expandingbrake shoe. This design principle remained for the next 50 years.Cams were used to force the shoes onto the drum with one having a pivot pin at the bottom to increasethe servo-assistance of the brakes. Equalising the brake pressure on both wheels was a problem Left, a leading/trailing shoe hydraulic brake; right the twin wheel cylinders create two leading shoes for the use on front brakes Page | 3
  • D. HEATHER - C2008809This was solved by the introduction of the hydraulic system, using fluid to transfer the force applied to thebrake pedal. One of the biggest developments of recent years has been the development of brakingsystems that inhibit the tendance of a car to skid under braking. (Copeland, 2005)The Anti-lock braking system works by using a sensor that detects the wheel when it begins to lock up, itthen releases the hydraulic pressure at the brake calliper to allow the wheel to spin again. The brake canbe reapplied and if the wheel locks again the process will be repeated. Anti –lock braking systems Page | 4
  • D. HEATHER - C2008809PUBLIC TRANSPORT BRAKESThe rocket train design expanded rail transport as it offered speedier transport. Mechanical brakes weredifficult to use, in 1869 George Westinghouse developed an air brake that was held off by air pressure.When air pressure was lost the brakes were applied which made it safer if the train lost air pressure.Electric trains have an advantage as they can have regenerative braking systems. The application of thebrakes on a train results in the electric motor switching to an electric generator which generateselectricity to power other items in the train such as lights or air-conditioning.REGENERATIVE BRAKING SYSTEMWhen disc brakes are applied the energy is wasted. Physics tells us that energy cannot be destroyed, ithas to go somewhere with most dissipating as heat and is wasted. The braking systems on cars wasteenergy and the driver can do nothing to stop this. Regenerative braking systems can recapture much ofthe cars kinetic energy and convert it into electricity. These brakes are primarily found in hybrid vehicles.Hybrid vehicles place a high degree of importance being able to keep the battery charged. Regenerativebrakes utilise the system that drives the vehicle to do the majority of the braking. When the brakes areapplied in an electric or hybrid vehicle the vehicles electric motor goes into reverse mode, causing it torun backwards thus slowing the cars wheels. When the motor runs backwards it acts as an electricgenerator, producing electricity that can be transferred to the vehicles batteries. This is best utilised incity or stop start traffic when the brakes are used constantly. The vehicles momentum is used to get themotor to run backwards as the mechanical energy puts the motor in reverse. Momentum is the propertythat keeps the vehicle moving once it is up to speed. When the motor is reversed the electricitygenerated by the motor is fed back into the batteries where it can be used to accelerate the vehicle again.Electronic control in a regenerative braking system allows the driver to select certain presets thatdetermine how the vehicle will apply the brakes and when. Regenerative brake controllers are electronicdevices that control brakes remotely, deciding when the braking starts, ends and how quickly the brakes Page | 5
  • D. HEATHER - C2008809need to be applied.The brake controller may decide if motor capability is capable of handling the force necessary to stop thecar. If it is not capable it will turn the braking to the friction brakes averting a catastrophe.The efficiency of regenerative braking system is the reason it has been developed. Conventional carsefficiency is 20%, with the remaining 80% of its energy being converted to heat through friction.Regenerative braking could capture as much as half that wasted energy and put it back to work.http://auto.howstuffworks.com/auto-parts/brakes/brake-types/regenerative-braking7.htm Regenerative braking system Page | 6
  • D. HEATHER - C2008809IMPACT OF HYDRAULIC LIFTING DEVICESHydraulic systems have the following advantages over power systems.• Equal forces are applied to each output cylinder• Higher efficiency than other systems• Less maintenance and more reliability• Low inertia of moving parts allows hydraulic systems to start and stop quickly. (Rochford, 2011)Hydraulic lifting devices contribute to safety in the workforce by reducing the human effort required toraise materials or supply a safe working platform. Hydraulic lifting devices greatly reduce the chance ofback injuries in construction workers.Hydraulic elevators are used in low-rise building up to 5 storeys. The elevator is pushed up the shaft byhydraulically controlled pistons or a telescopic piston to save space. The advantage of this system is itdoes not need overhead mounted equipment to lift the elevator. The pump can be located away fromthe shaft and installation and running costs are less than an electric elevator.Specialised work platforms that are hydraulically operated can lift workers up to heights quickly withminimum effort. They allow workers to move freely and work safely while high off the ground.Components of a hydraulic elevator Page | 7
  • D. HEATHER - C2008809RECENT INNOVATIONSHydraulic JackThe hydraulic jack forces compressible fluid into a cylinder by a plunger. Oil is used because it is a stablefluid and is self- lubricating which minimises maintenance.A Scottish machinist named Richard Dudjeon invented the hydraulic jack. Hydraulic cylinders have notchanged much over the years. The tolerances of the parts are tighter and the jack is still the hard workingpush-pull tools they have always been.Hydraulic jacks are easy to use, portable and lift loads from 1.5 to 3 tonnes. Hydraulic jacks have differentfunctions. Floor jacks are used to lift loads from the floor and in small areas bottle jacks are used. Ramjacks have long arms and are used in the construction industry.Jacks are utilised to make lifting and high pressure moving easy for industries. Hydraulic jacks are used byservice stations, storage establishments, automotive industries for a range of high pressure and heavyduty lifting procedures.The significance of jacks is that they make lifting and moving items or equipment easy for industries. Thehydraulic jack is easy to use and the process is accomplished quickly. Bottle Jack Page | 8
  • D. HEATHER - C2008809AERO INDUSTRYHydraulic systems in aircraft have multiple uses depending on the aircraft. Hydraulics is used to operatewheel brakes, landing gear and some constant speed propellers in small aircraft. Larger planes utilisehydraulics for flight control surfaces, spoilers, wing flaps and other systems.The hydraulic system compromises a reservoir, pump, filter, selector valve to control the direction of theflow, relief valve and an actuator.The fluid is pumped to an actuator. An actuator is a cylinder with a piston inside that converts fluid powerinto work which creates the power needed to move an aircraft system. Cylinders can be single or doubleacting depending on the systems requirements. A selector valve allows the control of the fluid direction.This system operates the extension and retraction of the landing gear during which the fluid needs towork in different directions. If the pressure within the system is excessive the relief valve provides anoutlet to reduce fluid pressure.The hydraulic fluid most widely used for aircraft has a mineral base. This fluid, a kerosene-like petroleumproduct has good lubricating properties. The fluid has additives to inhibit foaming and prevents theformation of corrosion. The fluid is chemically stable and changes viscosity very little with temperatureand is dyed for identification. Aircraft landing gear. Page | 9
  • D. HEATHER - C2008809 An example of a double acting cylinderThe gland is screwed into one end of the cylinder and the rod passes through it, a pressure seal and wiperseal are fitted to the gland to resist oil pressure and clean rod when it is moving in and out of the cylinder. Page | 10
  • D. HEATHER - C2008809 BibliographyCopeland.P.L. (2005). Engineering studies The Definitive Guide V2.Helensburg N.S.W. Anno Domini2000PtyLty.Rochford. J. (2011). Stage 6 Engineering Studies. [ed 2011]. Tumbi Umbi; KJS Publications. Page | 11