Course Title: Aerospace Mechanisms

Part B: Course Detail

Teaching Period: Term1 2010

Course Code: AERO5392

Course Title: Aerospace Mechanisms

School: 130T Vocational Engineering

Campus: City Campus

Program: C6011 - Advanced Diploma of Engineering (Aerospace)

Course Contact: Program Manager

Course Contact Phone: +61 3 9925 4468

Course Contact Email: engineering-tafe@rmit.edu.au


Name and Contact Details of All Other Relevant Staff

Teacher : Yadana Wai
Contact Detail
Location: 57.5.20
Telephone: 9925 4461
Fax: 9925 8099
E-mail: yadana.wai@ rmit.edu.au

Nominal Hours: 40

Regardless of the mode of delivery, represent a guide to the relative teaching time and student effort required to successfully achieve a particular competency/module. This may include not only scheduled classes or workplace visits but also the amount of effort required to undertake, evaluate and complete all assessment requirements, including any non-classroom activities.

Pre-requisites and Co-requisites

MATH5156 Aerospace Mathematics 1
ONPS5098 Aerospace Physics 1
ONPS5100 Aerospace Physics 2
AERO5390 Stress 1

Course Description

The purpose of this course is to provide training in aerospace mechanisms, power transmission devices and associated calculations.
This course involves the principles of analysis and design of mechanical sub-systems commonly used in aircraft. Areas of study include: friction and gear mechanism, linkages, bearings and mechanical vibrations.


National Codes, Titles, Elements and Performance Criteria

National Element Code & Title:

VBH740 Aerospace Mechanisms

Element:

Analyse linkage operation and calculate stresses in linkages.

Performance Criteria:

Explain the operation of simple aircraft linkage mechanisms, including levers and bellcranks
Explain what is meant by ‘mechanical advantage’ 
Perform force transfer calculations on static linkages 
Analyse the operation of typical aircraft linkages 
Calculate the stresses in linkages subject to static conditions
Explain how dynamic linkages are analysed in terms of velocities, accelerations and stresses

Element:

Explain and evaluate a range of types of bearings and perform calculations relating to bearings.

Performance Criteria:

Describe the operating principles of plain bearings
Describe plain bearing types, applications and methods of lubrication
Compare advantages and disadvantages of plain bearing applications
Describe various configurations and applications of bearing types including:
• ball
• roller
• self aligning
• foil
Describe the load carrying capability and constructional features of rolling element bearings
Justify applications of rolling element bearings in aircraft 
Describe rolling element bearing failure modes, distress terms and causes
Explain why bearings have a limiting speed
List advantages and disadvantages of rolling element bearings
Describe the types and uses of lubricants used in rolling element bearings
Define the following terms:
• basic rated life
• basic dynamic load rating
• basic static load rating, and
• equivalent load
Calculate equivalent static and dynamic loads using bearing charts
Estimate bearing life
Select suitable bearings, for an aerospace application, from a catalogue

Element:

Explain aspects of mechanical vibration and perform related calculations.

Performance Criteria:

Describe the nature of vibrations
Describe the conditions for defining the number of degrees of freedom of a system 
Explain free and forced vibration
Describe damping
Describe sources of vibration in aircraft
Derive the differential equation of motion for an undamped, one degree of freedom system, subject to free vibration using force and energy methods
For an undamped, one degree of freedom system, using force and energy methods, calculate the following:
• natural frequency
• maximum amplitude
• displacement at a given time
Derive the differential equation of motion for a damped, one degree of freedom system, subject to free vibration using force and energy methods
For a damped, one degree of freedom system, using force and energy methods, calculate the following:
• natural frequency
• maximum amplitude
• displacement at a given time
Derive the differential equation of motion for an undamped, one degree of freedom system, subject to forced vibration
For an undamped, one degree of freedom system subject to forced vibration, calculate the following:
• natural frequency
• maximum amplitude
• amplitude ratio
Derive the differential equation of motion for a damped, one degree of freedom system subject to forced vibration
For a damped, one degree of freedom system subject to forced vibration, calculate the following:
• natural frequency
• maximum amplitude
• amplitude ratio
• maximum amplitude ratio
• phase angle between the response and the forcing function
Calculate the force transmitted by a vibrating machine to its foundation
Derive the differential equations of motion for an undamped two degree of freedom system subject to free vibration
Calculate the natural frequencies of a two degree of freedom system using matrix methods
Describe the principles of vibration measurement, monitoring and interpretation

Element:

Explain concepts and perform calculations related to torque transmissions driven through friction mechanisms.

Performance Criteria:

Explain applications of friction mechanisms in aircraft
Explain what is meant by the term ‘coefficient of friction’
Determine the forces acting on a body on an inclined surface
Explain the advantages of power screws
Calculate the torque required to operate power screws
Explain the differences between clutches and brakes
Describe types of clutches and brakes
Describe properties of friction materials
Describe common methods of brake/clutch actuation in aircraft
Describe a simple brake mechanism
Derive expressions for torque transmission in disc brakes/clutches subject to uniform pressure and water
Calculate the torque transmitted by single and multiple disk brakes/clutches
Calculate the torque transmitted by a cone brake/clutch
Calculate the torque transmitted by a centrifugal clutch

Element:

Explain in words and diagrams the manufacture and operation of gear mechanisms and perform related calculations.

Performance Criteria:

Describe common gear types and their applications including:
• bevel
• differential
• helical
• hypoid
• planetary
• rack and pinion
• sector
• spur
• worm
Sketch a spur gear and label its principal parts and dimensions
Describe the following in relation to spur gears:
• wheel
• pinion
• pitch circle diameter
• diametral pitch
• learning unit
• addendum
• dedendum
• pitch point
• base circle, and
• pressure angle
Explain the requirement for backlash
Describe interference of involute teeth and methods of overcoming it
Describe methods of gear manufacture
Explain the force transfer from spur and helical gears to a bearing on the shaft
Describe the relationships between rotational speed, number of teeth, pitch circle diameters, torque and centre distances for simple gear trains and for compound gear trains.
Perform calculations involving simple gear trains and compound gear trains
Calculate the torque on gear casings
Sketch a simple epicyclic gear train, label components and indicate directions of rotation
Explain the operation of an epicyclic gear train
Perform calculations involving epicyclic gears


Learning Outcomes


1. Explain concepts and perform calculations related to torque transmissions driven through friction mechanisms.
2. Analyse linkage operation and calculate stresses in linkages.
3. Explain and evaluate a range of types of bearings and perform calculations relating to bearings.
4. Explain in words and diagrams the manufacture and operation of gear mechanisms and perform related calculations.
5. Explain aspects of mechanical vibration and perform related calculations.


Details of Learning Activities

The purpose of this module is to provide the training in aerospace mechanisms, power transmission devices and associated calculations. This module also facilitates articulation into Aerospace and Engineering degree courses. This course will cover the areas in frictrion mechanisms, linkages, bearings, gear mechanisms and mechanical vibrations.
The students will participate in activities such as the class lectures, tutorials and exercises, assignment and exam.


Teaching Schedule

Teaching Schedule

Session Topic Note
 1 Introduction to the subject, basic concepts of force, torque, energy, power, work, linear and angular displacement, velocity and acceleration. Lecture & Class Exercise
 2 The concept of friction, coefficient of friction and properties of friction materials, inclined surfaces and power screw. Lecture & Class Exercise
 3 Fiction mechanisms-brakes/Clutches. Lecture & Class Exercise
 4 Common methods of brake/clutch actuation in aircraft and torque transmitted by brakes/Clutches. Lecture & Class Exercise
 5 Linkage mechanisms, their operations and calculation of stresses in linkages. Lecture & Class Exercise
 6 Gear mechanisms, commmon gear types, their appications and related calculations-relationships between rotational speed, number of teeth, pitch circle diameters, torque and centre distances for simple gear trains and for compound gear trains. Lecture & Class Exercise
 7 Gear mechanisms, commmon gear types, their appications and related calculations-relationships between rotational speed, number of teeth, pitch circle diameters, torque and centre distances for simple gear trains and for compound gear trains. Lecture & Class Exercise
 8 Types of bearings-plain bearing, ball, roller, foil and self-aligning, applications of rolling element bearings in aircraft , their operating principles and calculations of static and dynamic loads.

Lecture & Class Exercise.

Assignment is issued.
 9

Mechanical Vibration-the nature of vibrations & sources of vibration in aircraft, damping,free Versus forced Vibration, differential equation of motion for an undamped & damped one degree of freedom system subject to free vibration and calculations of
• natural frequency
• maximum amplitude
• displacement at a given time.

 Lecture & Class Exercise
 10 Differential equation of motion for a damped and undamped, one degree of freedom system, subject to forced vibration. Calculation of
natural frequency
maximum amplitude
amplitude ratio
maximum amplitude ratio (damped)
phase angle between the response and the forcing function (damped) .		 Lecture & Class Exercise
 11 Revision & Tutorial Assignment is due
 12 Closed Book Exam  


Learning Resources

Prescribed Texts


References

Hannah, J., and Stephens, R.C., 1984., Mechanics of Machines, Elementary Theory and Examples., E.Arnold, London. ISBN 0713134712

Baumeister, T. et al, 1987., Marks’Standard Handbook for Mechanical Engineers., McGraw-Hill

Hall, et al. 1980., Schaum’s Outline of the theory and problems of Machine Design., McGraw-Hill., ISBN 00784342X

Shigley, J.E., and Mitchell, L.D., 1983., Mechanical Engineering Design., McGraw-Hill.,
ISBN 007056888X


Other Resources

Class notes, lectures and exercises.


Overview of Assessment

To successfully complete this course the student is required to pass written assessment tasks and demonstrate skills and ability by completing pratical tasks to aerospace standard.


Assessment Tasks

Participants are required to complete two assessment tasks. The first assessment task is an assignment worth 30% and the second assessment task (70%) is a closed book final examination at the end of the course. In order to pass the course, student must attain minimum 50% on individual assessment.

Assessment Item 1 (30%): ASSIGNMENT

Assessment Item 2 (70%): FINAL EXAMINATION

Grading Criteria

HD High Distinction 80 - 100 %
DI Distinction 70 - 79 %
CR Credit 60 - 69 %
PA Pass ( High Grading available 50 - 59 %
PX Pass ( No Higher Grading available) 50 - 100 %
NN Fail 0 - 49 %


Academic Misconduct

Students are reminded that cheating, whether by fabrication, falsification of data, or plagiarism, is an offence subject to University disciplinary procedures. Plagiarism in oral or written presentations is the presentation of the work, idea or creation of another person, without appropriate referencing, as though it is one’s own. Plagiarism is not acceptable.

The use of another person’s work or ideas must be acknowledged. Failure to do so may result in charges of academic misconduct which carry a range of penalties including cancellation of results and exclusion from your course.

Students are responsible for ensuring that their work is kept in a secure place. It is also a disciplinary offence for students to allow their work to be plagiarised by another student. Students should be aware of their rights and responsibilities regarding the use of copyright material. It is strongly recommended that students refer to the RMIT 2001 Guidelines for Students or to the RMIT University Homepage.




Assessment Matrix

Assessment Matrix

Assessment Method Learning Outcomes Percentage
Assignment 1 to 5 30%
Closed book exam 1 to 5 70%

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