27-07-2016, 03:53 PM
The National Programme on Technology Enhanced Learning (NPTEL), a project funded by the Ministry of Human Resource Development (MHRD), provides e-learning through online Web and Video courses in Engineering, Sciences, Technology, Management and Humanities. This is a joint initiative by seven IITs and IISc Bangalore. Other selected premier institutions also act as Associate Partner Institutions.
NPTEL is a curriculum building exercise and is directed towards providing learning materials in science and engineering by adhering to the syllabi of All India Council for Technical Education and the slightly modified curricula of major affiliating Universities. It has developed curriculum based video courses and web-based e-courses targeting students and faculty of institutions offering UG engineering programs.
Introduction to Kinematics
Kinematics is the branch of science which deals with motion without considering the forces which causes the motion. On the other hand, kinetics is the branch of science which also takes forces which causes motion as well as weight and inertia effects in study.
Kinematic Link and Kinematic Pair
Link: It is defined as a machine element having relative motion with respect to other parts of machine element.
Kinematic pair is defined as a joint of two links which permits relative motion between elements or links. Kinematic pair is constituted when there is mechanical contact between them and having arrangement of mechanism.
Lower pair is said to be constituted when two elements have surface contact between them.
Higher pair is said to be constituted when two element have point contact between them.
Kinematic Chain
Kinematic chain is one in which number of links are so connected that relative motion of any point on a page link with respect to any other point on the other page link follows a governing law
L = 2/3(J+2) Where, L = Number of links, J = Number of Joints
or
J = 3/2(L)-2, Where, H = Number of Higher pairs
One Higher pair = Two lower pair
The criterion for a chain to be constrained:
J+H/2 = 3/2(L)-2,
Where, H = Number of Higher pairs and J =Number of binary joints in chain
If R.H.S. = L.H.S. , Chain is said to be locked.
Mechanism
If the one of the page link of constrained kinematic chain is fixed, it results into 'Mechanism'
A mechanism with four links is called simple mechanism. Mechanism with single degree of freedom are having only even number of links.
Real life example is automobile propelling system which contains links in form of piston, connecting rod and cranks shaft to which flywheel and rear tire is attached.