Simple Mechanism

Simple MechanismContents Introduction Kinematic link or ElementTypes of linksStructures Difference between a machine and structureKinematic pairTypes of constrained motion1. Introduction Definition:Theory of Machines deals with the study of various parts of a machine and forces acting on them.A Machine is a device which receives energy in some available form and utilizes it to do some particular work.ContSubdivisions of Theory of Machines Kinematics Dynamics Kinetics Statics ContKinematics: Branch of theory of machines which deals with the relative motion between various parts of machinesDynamics: Branch of theory of machines which deals with the forces and their effects acting on the moving parts of machinesContKinetics: Branch of theory of machines which deals with Inertia forces which arise from the combined effect of the mass and motion of the machine parts.Statics: Branch of theory of machines which deals with the forces and their effects while the machine parts are at rest.2. Kinematic link or ElementEach part of machine which moves relative to some other part is called kinematic link or elementConsists of several partsRigidly fastened so that they do not move relatively to one anotherLink must be a resistant body

ContExample:

3. Types of linksRigid links:Do not undergo any deformation during transmission of motionExamples are connecting rod and crank mechanism of a reciprocating engineFlexible links:Partly deformed in a manner not to affect the transmission of motionExamples are belts,ropes,chains and wires which transmit tensile forces only

ContFluid links:Formed by having fluid in a receptacle and motion is transmitted by fluid by applying pressure or compressionHydraulic presses, jacks and brakesHydraulic jack

4. StructureAssemblage of number of resistant bodiesHaving no relative motion Meant for carrying loads having straining actionsExamples are railway bridge, machine frames and roof truss5. Difference between a machine and structureMachineStructure Parts move relative to one anotherMembers of structures dont move relative to one anotherTransforms available energy to some useful workNo energy is transformed in useful workLinks of machine may transform both power and motionMembers of structure transmit forces only6. Kinematic PairTwo links of a machine are in contact with each other are said to a pairIf the relative motion is completely or successfully constrained, the pair is said to be a kinematic pair7. Types of constrained motionCompletely constrained motion: when the motion between the pair is limited to a definite direction, irrespective of the direction of the force applied, then the motion is said to be completely constrained motion.For example, motion of piston in cylinder. Cont

Example

ContIncompletely constrained motion:when the motion between a pair can take place in more than one direction, then it is said to be incompletely constrained motionChange in direction of impressed force may alter the direction of motion of pairExamples are, a circular bar or shaft in a circular hole as it may either slide or rotate. Cont

ContSuccessfully constrained motion:When the motion between the pair is such that the constrained motion is not completed by itself, but by some other means, then the motion is said to be successfully constrained motion. For example, the motion of IC engine.