Mech and Dynamic wk2 notes

Page 1: Introduction

• Title: Mechanism and Dynamics of Machinery

• Topic: Introduction and fundamentals (Ch. 1 and Ch. 2)

• Lecturer: Dr. Loulin Huang (Contact: loulin.huang@aut.ac.nz)

Page 2: Course Description

• Course Title: Mechanisms and Dynamics of Machinery (Theory of Machines)

• Focus:

  • Understanding relationships between geometry, motion of machine parts, and the forces that produce these motions.

Page 3: Examples of Machinery

• Examples:

  • Robots

  • Engines

  • Additional examples include various machines.

Page 4: Course Scope

• Topics Covered:

  • Basic concepts of mechanisms and machines

  • Motion of machinery

  • Velocity and acceleration analysis of mechanisms

  • Design and analysis of:

    • Cams

    • Gears

    • Drive trains

  • Static and dynamic force analysis

Page 5: Recommended References

• Primary Text:

  1. Robert L. Norton, Design of Machinery: An Introduction to the Synthesis and Analysis of Mechanisms and Machines, 6th Edition, McGraw-Hill

• Additional Texts:

  1. Joseph Edward Shigley and John Joseph Uicker, Jr., Theory of Machines and Mechanisms, McGraw-Hill

  2. Charles E. Wilson and J. Peter Sadler, Kinematics and Dynamics of Machinery, 3rd Edition

  3. Lyndon O. Barton, Mechanism Analysis, 2nd Edition, Marcel Dekker, Inc.

Page 6: Definition of a Mechanism

• Mechanism:

  • Device that transforms motion into a desirable pattern.

  • Typically develops low forces and transmits minimal power.

  • Composed of elements arranged to transmit motion predictably.

Page 7: Definition of a Machine

• Machine:

  • Contains mechanisms designed to provide significant forces.

  • Two core functions:

    1. Transmitting definite relative motion

    2. Transmitting force

  • Motion and force combined represent power.

Page 8: Examples of Mechanisms

• Mechanisms:

  • Slider-crank

  • Cam-follower

  • Spur gears

  • Bevel gears

  • Helical gears

  • Herringbone gears

  • Worm and worm gear

  • Crossed shaft

Page 9: Types of Mechanisms

• Planar Mechanisms:

  • All rigid body motions occur in one plane or parallel planes (2D).

• Spatial Mechanisms:

  • Any relative motion not confined to one plane or parallel planes (3D).

  • This course primarily covers planar mechanisms.

Page 10: Kinematics and Kinetics Overview

• Kinematics:

  • Study of motion of parts without regard to the forces affecting this motion.

  • Concerned with concepts of space and time, including velocity and acceleration.

• Kinetics:

  • Study of the action of forces on bodies.

• Dynamics:

  • The combination of kinematics and kinetics.

Page 11: Degrees of Freedom (DOF)

• DOF Definition:

  • The number of independent parameters required to define a system's position in space at any time.

• Example: A pencil in a plane has three DOF.

Page 12: Types of Motions

• Pure Rotation: A single point (center of rotation) remains stationary; other points describe arcs.

• Pure Translation: All points describe parallel paths (curvilinear or rectilinear).

• Complex Motion: A simultaneous combination of rotation and translation.

Page 13: Transmission of Motion

• Methods of Transmission:

  • Intermediate links or connecting rods.

  • Direct contact between components (e.g., cam and follower, gears).

  • Flexible connectors such as belts or chains.

Page 14: Definition of Links

• Link:

  • A rigid body connecting two or more pairing elements to transmit force or motion.

Page 15: Definition of Joints and Pairs

• Joint (Pair):

  • Connection allowing motion between linked elements.

• Types of Joints:

  • Lower Pair: Full joint with surface contact (e.g., pin in a hole).

  • Higher Pair: Half joint with point or line contact.

  • Classification varies based on DOF, closure, and number of links connected.

Page 16: Joint Types and Degrees of Freedom

• Full Joints:

  • Example: Revolute joint (1 DOF) and Prismatic joint (1 DOF).

• Higher Pairs: Example: Roll-slide joints (2 DOF).

Page 17: Kinematic Diagrams

• Purpose:

  • Separate kinematic considerations from broader machine design problems.

Page 18: Motion Types in Mechanisms

• Types:

  • Pin joints, slider joints, half joints for varied motion transmissions.

Page 19: Frame and Links in Mechanism

• Defined Terms:

  • Kinematic chain: Assemblage of links and joints for controlled output motion.

  • Mechanism: Kinematic chain with at least one grounded link.

  • Machine: A combination of resistant bodies to perform work through determined motions.

Page 20: Kinematic Chain Examples

• Example: Chevrolet V-8 Engine

  • Components: Piston, connecting rod, crankshaft.

Page 21: Link and Joint Example

• Kinematic Diagram: Depicts links and their configurations within a mechanism prototype.

Page 22: Kinematic Diagrams Overview

• Examples: Weight-training mechanism kinematic diagrams highlighting actual contours of links.

Page 23: Kinematic Chain Definition & Classification

• Classification: Open/closed kinematic chains, dyads, etc.

Page 24: Mobility and Degrees of Freedom (DOF)

• Grubler’s (Kutzbach’s) Equation:

  • Formula: M = 3(L-1) - 2J1 - J2

  • Variables identified: M (degrees of freedom), L (number of links), J1, (1DOF joints), J2 (2DOF joints).

Page 25: Degrees of Freedom Example

• Examples of link connections:

  • Cases with varying degrees of freedom based on joint types.

Page 26: Degree of Freedom Calculations

• Example scenarios:

  • Analyzing DOF based on the type and arrangement of joints.

Page 27: Linking and Grounding

• Examples of Linkage with full/multiple joints:

  • Visual representation of configurations within the mechanism.

Page 28: Kinematic Chain with Joints

• Example: Linking full, half, and multiple joints and their implications on mobility.

Page 29: Four Bar Linkage Analysis

• Calculation of DOF:

  • Demonstration of Grubler’s rule applied to simple mechanisms.

Page 30: Complex Mechanism DOF Calculation

• Mechanism Examples:

  • Detailed examples of complex mechanisms and their DOF calculation.

Page 31: Joint Coincidence Impact on DOF

• Scenarios:

  • Effects of joint coincidence on the determination of mobility ratios.

Page 32: Freedom Degree Determination

• Calculated Lengths in Variables: Relationships between various lengths and position parameters.

Page 33: Grubler Criterion Paradoxes

• Exceptions: Specific mechanisms that contradict traditional DOF predictions.

Page 34: Linkage Isomers

• Characteristics:

  • Variation in nodes enabling diverse linkage motions and properties.

Page 35: Linkage Transformations

• Transformational Concepts:

  • Replacement of joints without affecting DOF in mechanisms.

Page 36: Example Transformations

• Mechanism Transformations:

  • Effects of altering link types on the configuration and function.

Page 37: Inversion and Grounding Effects

• Mechanism Examples:

  • Various machine types showcasing inversion through grounding different links.