Unit Description and General Aims

Design is one of the most important engineering functions because new products and processes are born and the old ones are improved through design. This unit aims to use the underpinning knowledge that the student has gained earlier through studying other units and to focus the student's analytical skills towards synthesis of solutions by working through the design of several simple and commonly used mechanical components.

The students will have an opportunity to gain in-depth knowledge of the design process as well as the principles and practices of mechanical design. The subject matter covered in this unit will include basic design concepts such as stress; strain; a factor of safety; , fracture mechanics and fatigue. 

Systematic design of pressurised cylinders, shafts and shafting elements, bearings, gears and various joints will be covered. Students will also learn to use CAD software for stress analysis of simple components.

Learning Outcomes

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

1. Perceive design related concepts such as stress, strain, failure mechanisms and fatigue. 
   Bloom’s level 5

2. Analyse stresses in pressurized cylinders and interpret types of fits for compound cylinders. 
   Bloom’s level 4

3. Design shafts, shafting elements, bearings and gears. 
   Bloom’s level 6

4. Analyse stresses in simple components using CAD 
   Bloom’s level 4

5. Design threaded, riveted and welded joints. 
   Bloom’s level 6

6. Evaluate stresses and strain in springs. 
   Bloom’s level 5

Student assessment

Overall requirements: Students must achieve a result of 50% or above in the exam itself to pass the exam, and must pass the exam to be able to pass the unit. An overall final unit score of 50% or above must be achieved to pass the unit once all assessment, including the exam, has been completed.

Prescribed and Recommended Readings

Required Textbook

• Schmid, S. R., Hamrock, B. J., & Jacobson, B. O. (2014). Fundamentals of Machine Elements. CRC Press.
• Bhandari, V. B. (2020). Design of Machine Elements (5th edition). McGraw Hill.
• Hansen, L. S. (n.d.). Autodesk Inventor 2022: A Tutorial Introduction.

Unit Content

Topic 1

Introduction and General Considerations

1. What is Design?

2. Design of machine elements

3. Stress, stress element, stress tensor and plane stress

4. Strain, strain tensor and plane strain

5. Normal stress and strain

6. Torsion

7. Bending stress and strain

8. Transverse shear stress and strain

Topic 2

Failure prediction for static loading

1. Introduction

2. Stress Concentration

3. Fracture Mechanics

4. Modes of Crack Growth

5. Fracture Toughness

6. Failure Prediction for Uniaxial Stress State

7. Failure Prediction for Multiaxial Stress State

Topic 3

Fatigue

1. Introduction to fatigue

2. Cyclic Stresses

3. Strain Life Theory of Fatigue

4. Fatigue Strength

5. Fatigue Regimes

6. Stress Concentration Effects

7. The Modified Endurance Limit

8. Cumulative Damage

9. Influence of Nonzero Mean Stress

10. Influence of Multi-Axial Stress States

11. Fracture Mechanics Approach to Fatigue

12. Linear Impact Stresses and Deformations

Topic 4

Stresses and deformations in cylinders

1. Tolerances and Fits

2. Pressurization Effects

3. Rotational Effects

4. Press Fits

5. Shrink Fits

Topic 5

Shafts and associated parts

1. Design of Shafts for Static Loading

2. Fatigue Design of Shafts

3. Additional Shaft Design Considerations

4. Critical Speed of Rotating Shafts

5. Keys, Roll Pins, Splines and Set Screws

6. Retaining Rings and Pins

7. Flywheels

8. Couplings

Topic 6

Sliding and rolling contact bearings

1. The Reynolds Equation

2. Thrust Slider Bearings

3. Journal Slider Bearings

4. Squeeze Film Bearings

5. Hydrostatic Bearings

6. Bearing Types and Selection

7. Geometry

8. Kinematics

9. Separators

10. Static Load Distribution

11. Elastohydrodynamic Lubrication

12. Fatigue Life

13. Variable Loading

Topic 7

Gears

1. Loads Acting on a Gear Tooth

2. Bending Stresses in Gear Teeth

3. Contact Stresses in Gear Teeth

4. Elastohydrodynamic Film Thickness

5. Gear Design Synthesis 

6. Helical Gears

7. Bevel Gears

8. Worm Gears 

Topic 8

Introduction to stress analysis using CAD

1. Create a simple part

2. Apply material to a simple part

3. Apply fixture to a simple part

4. Perform a stress analysis on a simple part

5. Interpret results of a stress analysis

Topic 9

Threaded joints 

1. Threaded Joints

2. Basic Types of Screw Fastening

3. Bolt of Uniform Strength

4. Locking Devices

5. Terminology of Screw Threads

6. ISO Metric Screw Threads

7. Bolted Joint—Simple Analysis

8. Eccentrically Loaded Bolted Joints in Shear

9. Eccentric Load Perpendicular to Axis of Bolt

10. Eccentric Load on Circular Base

Topic 10

Riveted Joints

1. Types of Rivet Heads

2. Types of Riveted Joints

3. Rivet Materials

4. Types of Failure

5. Strength Equations

6. Efficiency of Joint

7. Caulking and Fullering

8. Longitudinal Butt Joint for Boiler Shell

9. Circumferential Lap Joint for Boiler Shells

10. Eccentrically Loaded Riveted Joint

Topic 11

Welded Joints

1. Butt and Fillet Joints

2. Strength of Butt and Fillet Welds

3. Maximum Shear Stress in Parallel Fillet Weld

4. Maximum Shear Stress in Transverse Fillet Weld

5. Axially Loaded Unsymmetrical Welded Joints

6. Eccentric Load in the Plane of Welds

7. Welded Joint Subjected to Bending Moment

8. Welded Joint Subjected to Torsional Moment

9. Strength of Welded Joints

10. Welded Joints Subjected to Fluctuating Forces

11. Welding Symbols

Topic 12

Springs

1. Types of springs

2. Terminology of helical springs

3. Styles of end

4. Stress and deflection equations

5. Design of helical springs

6. Design against fluctuating load

7. Optimum design of helical spring

8. Helical torsion springs

9. Unit Review and exam overview

Software/Hardware Used

Software

• Software: AutoDesk Inventor - It is a comprehensive 3D CAD software used for mechanical design, simulation, and documentation. It is crucial for mechanical engineers as it enhances design accuracy, reduces development time, and facilitates collaboration. Applications include creating detailed parts and assemblies, performing simulations, and generating technical drawings. 
• Version: N/A
• Instructions: N/A
• Additional resources or files: N/A

Hardware

• N/A

Unit Changes Based on Student Feedback