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MECN 4110 Mechanisms Design Fall - 2010 Lecture 01

Chapters Objectives. Up on completion of this chapter, the student will be able toExplain the need for kinematic analysis of mechanism.Define the basic components that comprise a mechanism.Draw the kinematic diagram from a view of a complex mechanism.Compute the number of degrees of freedom of a

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MECN 4110 Mechanisms Design Fall - 2010 Lecture 01

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    1. MECN 4110 – Mechanisms Design Fall - 2010 Lecture 01 INTRODUCTION TO MECHANISM AND KINEMATICS

    2. Chapters Objectives Up on completion of this chapter, the student will be able to Explain the need for kinematic analysis of mechanism. Define the basic components that comprise a mechanism. Draw the kinematic diagram from a view of a complex mechanism. Compute the number of degrees of freedom of a mechanism. Identify a four bar mechanism and classify it according to its possible motion. Identify a slider crank mechanism.

    3. 1.1 ANALYSIS AND SYSTHESIS

    4. 1.2 DESIGN PROCESS

    5. 1.3 THE ENGINEERING REPORT LAB REPORT GUIDE Title Page of Lab Report (2) Table of Contents (3) Abstract (5) Objectives and Introduction (15) Theory (15) Result and Discussion (35) Conclusions (15) References (10)

    6. 1.4 UNITS There are several systems of units used in engineering. The most common in the United States are: The U.S. foot-pound-second (fps) system, The U.S. inch-pound-second (ips) system, and The System International (SI)

    7. 1.4 UNITS

    8. 1.5 THE SCIENCE OF MECHANICS

    9. 1.5 THE SCIENCE OF MECHANICS

    10. 1.5 THE SCIENCE OF MECHANICS

    11. 1.5 THE SCIENCE OF MECHANICS

    12. 1.6 DEGREE OF FREEDOM (DOF) OR MOBILITY A mechanical system’s mobility (M) can be classified according to the number of degrees of freedom (DOF) that it possesses. The system’s DOF is equal to the number of independent parameters (measurements) that are needed uniquely define its position in space and at any instant of time. This system of the pencil in the plane has three DOF The pencil in the this example represents a rigid body, or link, which for purposes of kinematics analysis we will assume to be incapable of deformation.

    13. 1.6 DEGREE OF FREEDOM (DOF) OR MOBILITY

    14. 1.7 TYPES OF MOTION Pure rotation Pure translation Complex motion, which is a simultaneous combination of rotation and translation

    15. 1.7 LINKS, JONTS AND KINEMATIC CHAINS A link is an rigid body that possesses at least two nodes that are points for attachment to other links

    16. 1.7 LINKS, JONTS AND KINEMATIC CHAINS A joint is an connection between two or more links (at their nodes), which allows some motion, or potential motion, between the connected links. Joints (also called kinematic pairs) can be classified in several ways:

    17. 1.8 JOINT PAIRS: THE SIX LOWER PAIRS

    18. 1.8 JOINT PAIRS: VARIOUS PAIRS

    19. 1.8 JOINT PAIRS: VARIOUS PAIRS

    20. 1.9 SOME DEFINITIONS CRANK: Link that makes a complete revolution and is pivoted to ground. ROCKET: Link that has oscillatory (back and forth) rotation and is pivoted to ground. COUPLER (or connecting rod): Link that has complex motion and is not pivoted to ground. GROUND: defined as any link or links that are fixed (nonmoving) with respect to the reference frame.

    21. 1.10 DETERMINING DEGREE OF FREEDOM OR MOBILITY Number or inputs that need to be provided in order o create a predictable output. Number of independent coordinates required to define its position Degree of Freedom (Mobility) in Planar Mechanisms Gruebler’s equation

    22. 1.10 DETERMINING DEGREE OF FREEDOM OR MOBILITY Kutzbatch’s modification of Gruebler’s equation

    23. 1.10 DETERMINING DEGREE OF FREEDOM OR MOBILITY

    24. 1.10 DETERMINING DEGREE OF FREEDOM OR MOBILITY

    25. 1.11 MECHANISMS AND STRUCTURES If the DOF is positive, it will be a mechanism, and the links will have relative motion. If the DOF is exactly zero, then it will be a structure, and no motion is possible. If the DOF is negative, then it is a preloaded structure, which means that no motion is possible and some stresses may also be present at the time of assembly.

    26. 1.12 EXAMPLES

    27. 1.12 EXAMPLES

    28. 1.12 EXAMPLES

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