BME204S

Unit Description and General Aims

The objective in presenting this unit is to provide students with an in-depth knowledge of the principles and practices of mechanical design, and the design process.

The subject matter covered in this unit will include basic design concepts such as stress; strain; a factor of safety; failure analysis; endurance; and, fracture mechanics. There will also be a systematic examination of the design and selection process involving mechanical system elements such as fasteners power screws; riveted and welded joints; keys; couplings; shafts; pulleys; flywheels; belts; ropes; chains; gears; bearings; springs; clutches; and brakes.

Students will have the opportunity to discuss at length all design related issues including designing for strength, rigidity, and stiffness, and design based on varying load conditions; they will also complete a detailed analysis involving the design of internal combustion (IC) engine parts such as piston; cylinder; connecting rod; and, crank shaft. The students will further learn to perform design calculations using simulation software. Students will also undertake project work involving designing a simple mechanical system.

At the conclusion of this unit, students will have been imparted with detailed knowledge of mechanical design concepts and the design process, and being equipped with the skills to design mechanical components.

Learning Outcomes

On successful completion of this Unit, students are expected to be able to:

1. Demonstrate relevant knowledge of design-related concepts such as stress, strain, a factor of safety, endurance, and fracture mechanics.
   Bloom's Level 2
2. Design threaded fasteners and power screws for different load conditions.
   Bloom's Level 6
3. Detail the design procedures involving riveted and welded joints.
   Bloom's Level 6
4. Design cotters, keys, couplings, and shafts for varying loads.
   Bloom's Level 6
5. Evaluate the design requirements for pulleys, flywheels, belts, ropes, and chains.
   Bloom's Level 5
6. Outline the design procedures for gears, bearings, springs, clutches, and brakes.
   Bloom's Level 6
7. Explain the design methodology for IC engine parts such as piston, cylinder, connecting rod, and crankshaft.
   Bloom's Level 2

Student assessment

Prescribed and Recommended Readings

Required Textbook

• R. Budynas, K. Nisbett, Shigley's Mechanical Engineering Design, 11th Edition. McGraw-Hill Education, 2020. ISBN-13: 978-0073398211

Reference

• Deutschman, AD, Michels, WJ & Wilson, CE 1975, Machine Design; Theory and Practice, 1st edn (Digitized 2007), Prentice Hall, ISBN: 978-23290008
• Robert, LN 2013, Machine Design, 5th edn, Prentice Hall, ISBN: 978-0133356717

Journal, website

Peer-reviewed journals and websites (advised during lectures)

Notes and Reference Texts

IDC notes and Reference texts as advised
Other material advised during the lectures

Unit Content

Topic 1 

Introduction and General Considerations

1. Engineering materials, their mechanical properties, and selection
2. Principal stresses
3. Stress-strain diagrams, stress analysis
4. Design stress and a factor of safety
5. Stress concentration factor in tension, bending, and torsion
6. Theories of failures
7. Design for variable and repeated loadings
8. Fatigue stress concentration factor, endurance diagrams
9. Fracture mechanics

Topic 2

Threaded Fasteners and Power Screws

1. Geometry of thread forms
2. Terminology of screw threads and thread standards
3. Stresses in threaded fasteners
4. Effect of initial tension
5. Relation between bolt tension and torque
6. Design of threaded fasteners under static, dynamic, and impact loads
7. Design of bolted joints due to eccentric loading
8. Mechanics and stresses of power screw
9. Efficiency of thread
10. Design of power screw

Topic 3

Riveted and Welded Joints

1. Types of rivet heads and riveted joints
2. Strength of rivet joint
3. Failure of riveted joint
4. Design of riveted joint
5. Eccentrically loaded riveted joint
6. Types of welded joints
7. Stresses in butt and fillet welds
8. Strength of welded joints
9. Eccentrically loaded joint
10. Welded joint subjected to bending moment
11. Fillet welds under varying loads

Topic 4

Design of Basic Elements, Couplings and Shafts

1. Design of Cotter and Knuckle joints
2. Design of keys and splines
3. Design of rigid, flexible and flange couplings, compression coupling, muff coupling, bush and pin type coupling, Oldham’s coupling
4. Transmission shafts
5. Torsion of shafts
6. Design against static load
7. Design for strength, rigidity, and stiffness
8. Design under continuous loading for fatigue

Topic 5

Pulleys, Flywheels, Belts, Ropes and Chains

1. Flywheel inertia
2. Stresses in flywheels and pulleys
3. Failure criteria
4. Design of flat and round belt drives, V-belts, timing belts, and wire ropes
5. Chain drives
6. Roller chains
7. Geometric relationships
8. Dimensions of chain components
9. Power rating of roller chains

Topics 6 and 7

Design of Gears

1. Spur gear terminology and definitions
2. Types of failure
3. Stress concentration
4. Lewis equation and form factor
5. Design for strength, dynamic, and wear loads
6. Helical gear definitions
7. Effective load on gear tooth
8. Helical gear design based on strength, dynamic, and wear loads
9. Bevel ear definitions
10. Effective load on gear tooth
11. Bevel gear design based on strength, dynamic, and wear loads
12. Worm gear definitions
13. Worm gear design based on strength, dynamic, wear loads
14. Efficiency of worm gear drives

Topic 8

Bearings

1. Types of ball and roller bearings
2. Rolling contact bearings – selection of bearings for radial and axial loads, bearing life
3. Design procedure
4. Mounting and lubrication for rolling contact bearings
5. Plain or journal bearings – types of lubrication, viscosity, hydrodynamic theory of lubrication
6. Somerfield number
7. Heat balance
8. Design procedure

Topic 9

Springs

1. Types of springs
2. Stresses in helical coil springs of circular and non-circular cross sections
3. Equation for stress and deflection
4. Tension and compression springs
5. Springs under fluctuating loads
6. Stresses in leaf springs
7. Equalized stresses
8. Energy stored in springs
9. Torsion, Belleville, and rubber springs

Topic 10

Clutches and Brakes

1. Introduction to clutches
2. Friction materials
3. Torque transmitting capacity
4. Design of single plate, multiple plate, centrifugal, and cone clutches
5. Introduction to brakes
6. Design procedure for block brake, internal expanding shoe brake, band brake, disc brake
7. Heat generation in brakes

Topic 11

Curved Beams, Cylinders, and Cylinder Heads, IC Engine Parts

1. Stresses in curved beams of standard cross sections used in crane hook, punching presses, and clamps, closed rings  and links
2. Lame’s equations for cylinders
3. Compound cylinders
4. Stresses due to different types of fits, cylinder heads, flats
5. Design of piston, connecting rod, and crank shaft

Topic 12

Unit Review

In the final week, students will have an opportunity to review the contents covered so far. Opportunity will be provided for a review of student work and to clarify any outstanding issues. Instructors/facilitators may choose to cover a specialized topic if applicable to that cohort.

Software/Hardware Used

Software

• Software: Autodesk Inventor

• Version: 2016 x 64

• Instructions: N/A

• Additional resources or files: N/A

Hardware

• N/A