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:
Robert L. Norton, Design of Machinery: An Introduction to the Synthesis and Analysis of Mechanisms and Machines, 6th Edition, McGraw-Hill
Additional Texts:
Joseph Edward Shigley and John Joseph Uicker, Jr., Theory of Machines and Mechanisms, McGraw-Hill
Charles E. Wilson and J. Peter Sadler, Kinematics and Dynamics of Machinery, 3rd Edition
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:
Transmitting definite relative motion
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.