machine and mechanisms

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Theory of Machines

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machine and mechanisms

  1. 1. Machine and Mechanisms Introduction to mechanisms and Kinematics 2014/3/9 1
  2. 2. Kinematics  Kinematics  It is the study of motion (relative motion of different links), quite apart from forces which produce that motion. More particularly, kinematics is the study of position, displacement, rotation, speed, velocity and acceleration which arise in the design of mechanical system, or kinematics of machine.  Kinematic analysis  Determine Position, displacement, rotation, speed, velocity, acceleration  Provide  Geometry dimensions of the mechanism  Operation range   Dynamic analysis  Power capacity, stability, member load  Planar mechanism – motion in 2D space 2014/3/9 2
  3. 3. Machines and mechanisms  Machine  Oxford dictionary: an apparatus for applying mechanical power, consisting of a number of interrelated parts each having a definite function.  Devices used to alter, transmit, and direct forces to accomplish a specific objective  Mechanical advantage is sole object of a machine e.g. lathe, shaper, planer etc. 3
  4. 4. 2014/3/9 4
  5. 5. Machines and mechanisms  Mechanism  Mechanical portion of a machine that has the function of transferring motion and forces from a power source to an output 2014/3/9 5
  6. 6. Wind shield
  7. 7. Simple Mechanism Let's make a simple mechanism with similar behavior. Take some cardboard and make four strips as shown in. Take 4 pins and assemble them as shown in fig Now, hold the 6in. strip so it can't move and turn the 3in. strip. You will see that the 4in. strip oscillates.
  8. 8. Loader 4 bar mechanism
  9. 9. Slider crank mechanis
  10. 10. crank & piston
  11. 11. Block feeder
  12. 12. Mechanism terminology  Linkage  Frame  Links– rigid body  Joint  Primary joint (full joint)  Revolute joint (pin or hinge joint)– pure rotation  Sliding joint (piston or prism joint)– linear sliding 2014/3/9 12
  13. 13. Mechanism terminology cont  Higher-order joint (half joint)  Allow rotation and sliding  Cam joint  Gear connection 2014/3/9 13
  14. 14. Mechanism terminology cont  Simple link  A rigid body contains only two joints  Crank  Rocker  Complex link  A rigid body contains more than two joints  Rocker arm  Bellcrank  Point of interest  Actuator  A power source link 2014/3/9 14
  15. 15. Kinematic diagrams 2014/3/9 15

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