mec2405 machine dynamics - transtutors … · 2 mec2405 – machine dynamics introduction this book...

MEC2405

Machine dynamicsFaculty of Engineering and Surveying

In t roduc to ry bookSemester 1 2012

Published by

University of Southern QueenslandToowoomba Queensland 4350Australia

http://www.usq.edu.au

© University of Southern Queensland, 2012.1.

Copyrighted materials reproduced herein are used under the provisions of the Copyright Act 1968 as amended, or as a result of application to the copyright owner.

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without prior permission.

Produced by Learning Resources Development and Support using FrameMaker7.1 on a Pentium workstation.

Table of contents

Page

Essential information 1

Introduction 2Course leader 2Course overview 3Presentation of course 4

Resources 5DVD 5

Study schedule 7

Assessment 9Assessment scheme 9

Assignment 10

Sample examination papers 13

MEC2405 – Machine dynamics 1

Essential information

The topics in the following list provide important information that will assist you with your study. You can access a handout containing the information on your StudyDesk through the ‘Essential information (study materials)’ link <http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/essentialhandout.pdf>. You will need your UConnect username and password to access the file. Please make sure you read this information carefully before commencing your study.

• Getting started <http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/getting_started.pdf>

• Course specification <http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/course_specification.pdf>

• Support <http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/support.pdf>

• UConnect<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/u_connect.pdf>

• Assignment submission<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/assignment_submission.pdf>

• Grading levels<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/grading_levels.pdf>

• Course evaluation <http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/course_evaluation.pdf>

• Residential schools<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/residential_school.pdf>

• Library<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/library.pdf>

• Referencing APA<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/apa_referencing_guide.pdf>

• Referencing Harvard AGPS<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/harvard_referencing_guide.pdf>

• Optional purchase of study materials<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/optional_purchase.pdf>

• USQ policies and procedures<http://usqstudydesk.usq.edu.au/file.php/1/sitefiles/DeC/essential_info/policies_procedures.pdf>

2 MEC2405 – Machine dynamics

Introduction

This book is your guide to studying the course MEC2405 Machine Dynamics. It contains a study schedule as well as some general information you might find useful.

Machine Dynamics is a compulsory course in the Bachelor of Technology and the Associate Degree Program. In broad terms it develops the basic physical relationships between forces and motion and then applies these to a range of common practical situations and devices.

The external study package comprises study modules to a set text. Additionally some topics are supported by the DVD Applied mechanics 3rd edition. The DVD will be made available on loan for this semester from the USQ library. However, you can order your own copy from the USQ Bookshop if you would like to retain a personal copy.

The choice of textbook for this course was a real problem. There are several modern, well presented texts that cover the basic theory but do so at a more advanced mathematical level than is necessary for either the Bachelor of Technology or the Associate Degree.

At the other end of the spectrum were several texts which either were at too low an analytical level or were rather uninspiring in their presentation. Few in either category provided the practical application that I wanted.

The chosen text is by Ryder and Bennett. Its development of basic theory is about the right mathematical/analytical level, it covers the full range of topics treated by this course and it does incorporate practical applications. However some of you might find its descriptions and explanations rather terse. Therefore, expanded explanations are provided in the study book for those topics you might find difficult. Finally, Ryder and Bennett have set some pretty tough problems. Don’t be surprised or upset if you cannot do those that are not listed – they generally contain quite tricky (but interesting) aspects that expect analytical/mathematical ability beyond this course. Ryder and Bennett is a little short of suitable level problems in some topics. Supplementary problems in those cases are provided in the study books. The problems from Ryder and Bennett that you are expected to do are listed in the study books.

Course leader

The examiner for this course is Peter Penfold. Peter obtained a fitting and turning trade certificate and was later employed as a drafter in a tool design drawing office. Peter joined the faculty in 1977 and has been involved in many aspects of project design and manufacture for both postgraduate and undergraduate programs. Since 1985 Peter has been a part of the teaching team for the Mechanical Discipline.


Course overview

Kinematics

Rigid Body Motion

Friction Brakes

Clutches and Belt

Drives

Work, Energy

and Power

Kinematics

Mechanisms

Kinetics

Balancing

Rotating Masses

Kinematics

Angular Motion

Kinematics

Linear Motion

Impulse and

Momentum

Vibrations

Bearings*

Geared

Systems

* This topic is included as general information only and will not be assessed in this course.

However, it will be covered in detail in a subsequent course.


Presentation of course

The course is presented as 13 modules each of which deals with a single topic or group of closely related topics.

1. Introduction

2. Kinematics – linear motion of a particle

3. Kinematics – angular motion of a particle

4. Kinematics – rigid body motion

5. Kinematics of mechanisms

6. Kinetics

7. Work, energy and power

8. Impulse and momentum

9. Friction brakes/clutches and belt drives

10. Balancing rotating masses

11. Bearings (refer to the note on the previous page)

12. Geared systems

13. Vibration

While these modules are largely independent of each other and could be studied in any order, the following study schedule is suggested:

• to assist you to allocate an appropriate amount of time to each module

• to ensure that you have the requisite knowledge to complete the assignments by the set dates.


Resources

DVD

The DVD Applied mechanics, 3rd edition, is required as part of the course materials. It comprises a series of short topics (nominally 10 minutes duration) – each being very much specific to a module in this course.

Modules which have a video recording to complement the text display this symbol on the module title page.

To obtain a copy on loan of this DVD log on to DocEx on the Library website. Access can be gained from the USQ website>The Library> Off-Campus Students (under Information For…).

Remember: Fines and penalties will be incurred for late return or late renewal of the item on loan. This DVD must be returned to the USQ Library by the end of the semester.

You can purchase your own copy of this DVD by placing an order at the USQ Bookshop.


Study schedule

Week Module Activity/Reading Assessment

1 1. Introduction SB activity – 1.1; 1.2StudyDesk test 1

2 2. Kinematics – Linear Motion of a Particle

SB activity – 2.1StudyDesk test 2

3 3. Kinematics – Angular Motion of a Particle


4 4. Kinematics – Rigid Body Motion


Reminder: End of week 4 is the last date to drop courses without academic or financial penalty.

5 5. Kinematics of Mechanisms


6 BREAK

7 BREAK

8 6. Kinetics SB activity – 6.1StudyDesk test 6

Reminder: End of week 8 is the last date to drop courses without academic penalty.

9 7. Work, Energy and Power


10 8. Impulse and Momentum


11 9. Friction, Brakes, Clutches and Belt Drives

SB activity – 9.1; 9.2; 9.3; 9.4StudyDesk test 9

Assignment Due11 May 2012

12 10. Balancing Rotating Masses


13 12. Geared Systems SB activity – 12.1; 12.2; 12.3; 12.4StudyDesk test 12

14 13. Vibrations SB activity – 13.1; 13.2StudyDesk test 13

15 REVISION

16–17 EXAMINATION PERIOD


Assessment

See the course specification for the details of the assessment of this course.

In broad terms I believe that students need continual assessment and immediate feedback while they are actually studying so that they can recognise any misunderstandings they might be developing. They also need to do exercises that will develop their self-confidence to handle real problems. This is the purpose of the many solved problems given in the study modules and the ‘formative’ self-assessed problems available from the USQStudyDesk. These do not carry any marks towards your final grade, but they should help you to identify and correct any misunderstandings that you might have.

The summative assessment in this course consists of:

• one assignment worth 400 marks

• an open book examination worth 600 marks.

The final exam will be open book and will cover the whole of the course. Sample examination papers are given in this book and are also available on the USQStudyDesk.

Assessment scheme

The following table shows the course objectives assessed for each assessment piece.

Assignment Examination

Objective Q1 Q2 Q3 Q4 Q5

1. Analyse the kinematics of planar motion of a particle and rigid body

2. Use the free body diagram method to solve simple problems involving the forces on particles and rigid bodies and their resulting planar motion

3. Calculate the velocity and acceleration of any point within a simple 2D mechanism

4. Apply the principles of work-energy and impulse-momentum to the analysis of simple bodies in 2D motion

5. Calculate the dynamic forces resulting from out-of-balance masses and determine the corrective masses to balance that system

6. Determine the dynamic behaviour of a range of common engineering devices

7. Analyse the vibrational response of simple single-degree-of-freedom systems to determine damped and undamped frequencies, amplitude and the forces transmitted to the system’s support


Assignment

Question 1 (80 marks)

Rod AO is rotating counter clockwise about O and decelerates uniformly from 60 rpm to 20 rpm in a 0.8 second period. At the same time block B is moving outward and accelerating at 0.5 m/s2. At a particular instance in time AO is rotating at 45 rpm and is 30° below the horizontal. At the same instant block B is at a position 60 mm from O and moving at a velocity of 0.2 m/s. Determine the nett acceleration of the block at this instance.


A projectile is fired at an elevation of 30° with an initial velocity of 36 m/s. If the landing elevation is 20 m below the launch elevation and ignoring air resistance, calculate the:

(i) maximum height reached during the flight as measured from the launch elevation

(ii) total flight time

(iii) horizontal distance travelled

(iv) velocity at impact

Due date: 11 May 2012

Value: 400 of the 1000 marks for this course

A

O

B

30o



A 10000 kg truck travelling at 5.5 m/s along a straight level road rear ends a 1300 kg passenger vehicle travelling at 2.2 m/s in the same direction. If the coefficient of restitution between the two vehicles is 0.4 determine the velocity of each vehicle immediately after impact.


A shaft is supported by bearings at D and E as shown in the diagram below. The axial locations for planes containing out-of-balance masses A, B, and C are also depicted.

Out-of-balance at A is equivalent to 0.5 kg mass at a radius of 50 mm.

Out-of-balance at B is equivalent to 0.75 kg mass at a radius of 60 mm.

Out-of-balance at C is equivalent to 1.5 kg mass at a radius of 40 mm.

Determine the magnitude and the angular location of the bearing reaction forces when the shaft rotates at 500 rpm.

30º

20 m

A130° 30°

170°

B

C

600 mm

1200 mm

300 mm

950 mm

D

E



Rod AO in the stone crusher mechanism shown below is rotating counter clockwise at a constant 764 rpm. At the position and instant shown determine the:

(i) absolute velocity and acceleration of point A

(ii) angular velocity of link AB

(iii) angular velocity of link PB

(iv) absolute velocity of point C

(v) angular velocity of block containing point C

OA = 100 mm; AB = 850 mm; PB = BC = QC = 500 mm

The diagram is reproduced to scale but not 1:1

500

Q

C

A40°

600

B

P

O

1000

500


Sample examination papers

Included in this introductory book are the 1995 examination, with model solutions, plus the 2001 examination. Other past examinations are available through UConnect.

Please note that from 2008 and onwards the duration of the examination will be two (2) hours and not three (3) as in previous years.

mec2405 machine dynamics - transtutors … · 2 mec2405 – machine dynamics introduction this book...

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