Machine design

1Lecture 1

Time: M _ _ _ _14:45 - 17:30

MECH 344/M

Machine Element Design

Instructor: Dr. S. Narayanswamy

Office Room: EV 004.124

Phone: 848-2424 (7923)

Office Hours: M _ _ _ _ 11:00 12:00 or by appointment

e-mail: [email protected]

Web site: http://users.encs.concordia.ca/~nrskumar

Contact Details

This course covers the basic principles employed in the

design of standard mechanical components subjected

to operating force and moment fields

Lectures - 3 hours each

13 Lectures of all - one is an introductory lecture

2 Term Tests

Final exam

About the course

3 Continuous teaching hours/week --W--

14:45 17:30 @ FGB040

13 lectures + 2 Term Tests + Final

Course Web Page

http://users.encs.concordia.ca/~nrskumar

Class logistics

TEXTBOOK

Fundamentals of Machine Component Design Robert C. Juvinall and Kurt M, Marshek, Wiley; 5th edition.

REFERENCES

1. Richard G. Budynas and Keith Nisbett, Shigleys Mechanical Engineering Design, 10th Edition, McGraw-Hill, 2014.

2. M. F. Spotts, T. E. Shoup and L. E. Hornberger, Design of Machine Elements, 8th Edition, Prentice-Hall, 2004.

3. Robert L. Norton, Machine Design An Integrated Approach, 5th Edition, Prentice Hall, 2013.

4. S. R. Schmid, B. J. Hamrock, and B. Jacobson, Fundamentals of Machine Elements, 3rd Edition, CRC press, 2013.

Text book and other reference

There will be 1 and half hour tutorial on Thursdays for

2 different sections

Tut MA ---J- (17:45-19:25) SGW H-564

Tut MB ---J- (17:45-19:25) SGW H-544

There will be TAs who will provide more details on

the problem solving

Attending tutorials is necessary as this will help in

preparing you for the exams

The Tutorial

There will be two term tests in all during the term

The tests will be for 75 minutes on the 6th and 11th week during

Tutorial hours

Test #1: Thursday February 19, 2015 (Open Book-textbook only)

Test #2: Thursday April 02, 2015 (Open Book-textbook only)

Material covered for each test will be given in class one week prior

to the date of the test (definitely not by email)

Duration of the test will be 75 Minutes

Open Book-textbook only

20% weightage towards final grade

Term Tests

Grade composition:

Two Term Tests : 40%

Final: 60%

Grading Scheme

To pass the course you have to

Pass the final

Attend the term tests as well as midterm and get good marks

The final exam will have problems similar to the ones in

tutorials

Conducted during the university wide exam period

Duration of the test: 3 hours.

Write the final exam with confidence that you will do

very well

It is IMPERATIVE to pass the final to pass the course

Final Test

In order to pass the course you have to obtain at least 50%

of mark from the Final Exam.

Electronic communication devices (including cell phones)

are not allowed in examination rooms.

Only Faculty Approved Calculators will be allowed in

examination rooms.

In the event of extraordinary circumstances beyond the

University's control, the content and/or evaluation scheme

in this course is subject to change

10

General Notes

Introduction

Machine Design

Design Process

Safety Factors

Contents of today's lecture

Chapter 1Mechanical Engineering Design

in Broad Perspective

Copyright 2012 by John Wiley & Sons, Inc. All rights reserved.

Fundamentals of Machine

Component DesignFifth Edition

Robert C. Juvinall Kurt M. Marshek

Whatever area you will choose

This course is fundamental.

Outline of the course12-Jan week 1 Introduction to Design: An overview of the subject, Machine Design Process -

19-Jan week 2

Fundamental Topics from Mechanics of Materials:

Stresses due to Axial, Bending, Direct Shear, Transverse Shear and Torsional Loadings; Curved

Beams; Combined Stresses- Mohr Circle; Stress Concentration Factors; Residual Stresses; Thermal

Stresses

4 (must be

reviewed by

students)

26-Jan week 3

Static Failure Theories: Failure of Ductile Materials under Static Loading (Maximum Shear Stress

Theory, Maximum Distortion Energy Theory); Failure of Brittle Materials under Static Loading

(Modified Mohr Theory)

6

(Sections 6.5-

6.12)

2-Feb week 4 Fatigue Failure Theories: Basic Concepts and Standard fatigue Test; Fatigue Strengths for Reversed

Bending, Reversed Axial Loading and Reversed Torsional Loading; Fatigue Strength for Reversed

Biaxial Loading; Influence of Surface and Size on Fatigue Strength; Effect of Mean Stress on Fatigue

Strength; Effect of Stress Concentration; Fatigue Life Prediction with Randomly Varying Loads

8

(Sections 8.1-

8.12)9-Feb week 5

16-Feb week 6 Design of Screws and Fasteners: Thread Forms, Terminology and Standards; Power Screws; Screw

Stresses; Threaded Fasteners; Fasteners Materials and Methods of Manufacture; Bolt Tightening

and Initial Tension; Bolt Tension with External Joint-Separating Force; Bolt Selection for Static

Loading; Bolt Selection for Fatigue Loading10

2-Mar week 7

9-Mar week 8

Design of Springs: Coil Spring Stress and Deflection; Stress and Strength Analysis for Helical

Compression Springs-Static Loading; End Designs of Helical Compression Springs; Bucking

Analysis of Helical Compression Springs; Design Procedure for Helical Compression Springs-Static

Loading; Design of Helical Compression Springs for Fatigue Loading

12

(Sections 12.1-

12.8)

16-Mar week 9

Design of Spur Gears: Geometry and Nomenclature; Interference and Contact Ratio; Gear Force

Analysis; Gear-Tooth Strength; Gear-Tooth Bending Fatigue Analysis- Basic Concepts and

Recommended Procedure; Gear Tooth Surface Fatigue Analysis-Basic Concepts and

Recommended Procedure

15

(Sections 15.1-

15.12)

23-Mar week 10Design of Shafts and Keys: Shaft Loads; Attachments and Stress Concentrations; Shaft Stresses; Rotating-Shaft Dynamics; Overall Shaft Design; Keys

17

(Sections 17.1-

17.6)30-Mar week 11

13-Apr week 12

Design of Journal and Rolling-Element Bearings: Rolling-Element Bearing Types; Fitting of Rolling-

Element Bearings; Catalogue Information for Rolling-Element Bearings; Bearing Selection based on

Fatigue Life Requirement

14

16-Apr week 13 Review

15Engineering design is the process of applying the various

techniques and scientific principles for the purpose of defining a

device, a process, or a system in sufficient detail to permit its

realization.

A Machine is:

(1) An apparatus consisting of interrelated units, or

(2) A device that modifies force or motion

A Structure has no moving parts, e.g. bridges, buildings.

A machine is a device that

transforms energy

Has fixed and moving parts

Connects the source of power and

the work to be done

In case of motor and generator

electricity is converted to mechanical

movement and vice versa

In IC engine, connecting rod and

crank shaft transfers energy

The design process

Design involves constrained creation

Constraints: Technology limits

Human and environment concerns

Durability and reliability

Cost

Market requirements

Etc.

Thedesign process

REPRESENTATION

PERCEPTION

KNOWLEDGE

INTUITION

CONCEPT

PURE CONCEPT

EMPIRICAL CONCEPT

NOTION

IDEA

Basic requirements to be able to

perform a design

All the above interacts in your

judgment even if you are not

aware of it

You have to train your judgment

to be able to perform solution-

solving based thinking

The design process

A design is created after analysis, full

understanding of requirements and

constraints and synthesis

Two individuals may not come with the

same solution to the same problem Example: Connect two straight pipes ND 4 to

avoid leaking of the gas and to permit easy

maintenance of the segment

Solutions to the problem

Multiple: flanges, clips, clamps, seals, etc.

Concurrent engineering

approach

The design process

1. Problem Defn.

2. Concept and

ideas

3. Solutions

4. Models/Prototype

5. Production and

working drawings

The design process

A Component !

Factor of Safety N =

Material StrengthDesign Load

37

51

The sections chosen for load determination in the previous examples were, by simple

inspection, clearly those subjected to the most critical loading.

In more complicated cases, however, several sections may be critical, and their locations

less obvious.

In such instances it is often helpful to employ an orderly procedure

of following the lines of force (approximate paths taken by the force, determinedby simple inspection) through the various parts, and noting along the way any sections

suspected of being critical. Such a procedure is illustrated in the following example.

52

Assumptions:

1. The weight of the yoke connection can be ignored.

2. The load is divided equally between the two prongs of the fork (the loads and

yoke connection are perfectly symmetrical).

3. The load in each prong is divided equally between the portions on each side of

the hole.

4. Distributed loads are represented as concentrated loads.

5. The effects of pin, blade, and fork deflections on load distribution are negligible.

6. The pin fits snugly in the fork and blade.

Machine design

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