05-03-2013, 11:41 AM
Theory of Machines
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Kinematics and Kinetics of Mechanisms
Introduction:
Theory of Machines: may be defined as that branch of engineering science, which deals with the study of relative motion between the various parts of machine, and forces which act on them. The knowledge of this subject is very essential for an engineer in designing the various parts of a machine.
Sub- divisions of theory of Machines:
They Theory of Machines may be sub- divided into the following four branches:
1- Kinematics: is that branch of theory of machines which is responsible to study the motion of bodies without reference to the forces which are cause this motion, i.e it’s relate the motion variables (displacement, velocity, acceleration) with the time.
2- Kinetics: is that branch of theory of machines which is responsible to relate the action of forces on bodies to their resulting motion.
3- Dynamics: is that branch of theory of machines which deals with the forces and their effects, while acting upon the machine parts in motion.
4- Statics: is that branch of theory of machines which deals with the forces and their effects, while the machine parts are rest.
There are some definitions which are concerned with this subject, must be known:
Mechanism: is a combination of rigid bodies which are formed and connected together by some means, so that they are moved to perform some functions, such as the crank- connecting rod mechanism of the I.C. engines, steering mechanisms of automobiles……. etc.
The analysis of mechanisms is a part of machine design which is concerned with the kinematics and kinetics of mechanisms (or the dynamics of mechanisms).
Translated bodies:
There are some bodies in the mechanism which are constrained to move in translation manner, such as the piston of crank- connecting rod mechanism, the body is used to be in translation motion, if any line remain in some configuration during motion; then all the points have the same absolute velocity and acceleration.