final term paper of dom

8/7/2019 final term paper of dom

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TERM PAPER OF MEC 302

TOPIC:- Slider crank mechanism

SUBMITTED TO: SUBMITTED BY:

MR Varun Avinash rajput

B4911 A1510906554

B.TECH (ME)

Acknowledgement


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First of all, I would like to express my deep sense of

gratitude to dynamic paragon, ingenious Teacher Mr.varun, who assigned me this topic.

I also express my sincere gratitude to my parents and

my friends, for their cordial support, affectionate help

and constant inspirations for the achievement of thiswork.I would also like to thank them for providing me

necessary facilities for conducting this work.


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Contents :-

Introduction

In the Four-stroke cycle

Multibody system

Applications

Example

Concept

Degree of freedom

Constraint condition


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Introduction:-

The purpose of the slider-crank mechanism is to convert the linear motion ofthe piston to rotational motion of the crankshaft. One common application of

this mechanism is in internal combustion engines.

Arrangement of mechanical parts designed to convert straight-line motion to rotary

motion, as in a reciprocating piston engine, or to convert rotary motion to straight-

line motion, as in a reciprocating piston pump. The basic nature of the mechanism

and the relative motion of the parts can best be described with the aid of the

accompanying

In which part 1, the fixed frame or block of the pump or engine, contains acylinder, depicted in cross section by its walls DE and FG, in which the piston, part4, slides back and forth. The small circle at A represents the main crankshaft

bearing, which is also in part 1. The crankshaft, part 2, is shown as a straightmember extending from the main bearing at A to the crankpin bearing at B, whichconnects it to the connecting rod, part 3. The connecting rod is shown as a straightmember extending from the crankpin bearing at B to the wristpin bearing at C,which connects it to the piston, part 4, which is shown as a rectangle. The threebearings shown as circles at A, B, and C permit the connected members to rotatefreely with respect to one another. The path of B is a circle of radius AB; when B
http://www.britannica.com/EBchecked/topic/510368/rotary-motionhttp://www.britannica.com/EBchecked/topic/510368/rotary-motionhttp://www.britannica.com/EBchecked/topic/493549/reciprocating-enginehttp://www.britannica.com/EBchecked/topic/496869/relative-motionhttp://www.britannica.com/EBchecked/topic/144176/cross-sectionhttp://www.britannica.com/EBchecked/topic/132981/connecting-rodhttp://www.britannica.com/EBchecked/topic/510368/rotary-motionhttp://www.britannica.com/EBchecked/topic/510368/rotary-motionhttp://www.britannica.com/EBchecked/topic/493549/reciprocating-enginehttp://www.britannica.com/EBchecked/topic/496869/relative-motionhttp://www.britannica.com/EBchecked/topic/144176/cross-sectionhttp://www.britannica.com/EBchecked/topic/132981/connecting-rod


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is at point h the piston will be in position H, and when B is at point j the piston willbe in position J. On a gasoline engine, the head end of the cylinder (where theexplosion of the gasoline-air mixture takes place) is at EG; the pressure producedby the explosion will push the piston from position H to position J; return motionfrom J to H will require the rotational energy of a flywheel attached to thecrankshaft and rotating about a bearing collinear with bearing A. On areciprocating piston pump the crankshaft would be driven by a motor.

A four-bar linkage with output crank and ground member of infinite length. Aslidercrank (see illustration) is most widely used to convert reciprocating to rotarymotion (as in an engine) or to convert rotary to reciprocating motion (as in pumps),but it has numerous other applications. Positions at which slider motion reversesare called dead centers. When crank and connecting rod are extended in a straightline and the slider is at its maximum distance from the axis of the crankshaft, theposition is top dead center (TDC); when the slider is at its minimum distance from

the axis of the crankshaft, the position is bottom dead center (BDC).
http://www.britannica.com/EBchecked/topic/226592/gasoline-enginehttp://www.answers.com/topic/linkagehttp://www.answers.com/topic/sliderhttp://www.answers.com/topic/crankshafthttp://www.answers.com/topic/tdchttp://www.answers.com/topic/business-development-bank-of-canadahttp://www.britannica.com/EBchecked/topic/226592/gasoline-enginehttp://www.answers.com/topic/linkagehttp://www.answers.com/topic/sliderhttp://www.answers.com/topic/crankshafthttp://www.answers.com/topic/tdchttp://www.answers.com/topic/business-development-bank-of-canada


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Principal parts of slider-crank mechanism.

The conventional internal combustion engine employs a piston arrangement inwhich the piston becomes the slider of the slider-crank mechanism. Radial enginesfor aircraft employ a single master connecting rod to reduce the length of thecrankshaft. The master rod, which is connected to the wrist pin in a piston, is part

of a conventional slider-crank mechanism. The other pistons are joined by theirconnecting rods to pins on the master connecting rod.

To convert rotary motion into reciprocating motion, the slider crank is part of awide range of machines, typically pumps and compressors. Another use of theslider crank is in toggle mechanisms, also called knuckle joints. The driving forceis applied at the crankpin so that, at TDC, a much larger force is developed at theslider. See also Four-bar linkage.

In the Four-stroke cycle:-

An internal combustion engine operates by burning a small amount of a high-Energy content fuel, such as petroleum, and using the energy released to driveashaft. The four-stroke combustion cycle, developed by Nikolaus Otto in1867, is
http://www.answers.com/topic/piston-pinhttp://www.answers.com/topic/crankpinhttp://www.answers.com/topic/four-bar-linkagehttp://www.answers.com/topic/piston-pinhttp://www.answers.com/topic/crankpinhttp://www.answers.com/topic/four-bar-linkage


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commonly used in petrol-driven internal combustion engines

Four-stroke engine cycle.:-The four strokes in the Otto cycle are shown in Figure .These are:

Intake: The inlet valve is open and the piston moves downwards, drawing inamixture of fuel and air into the cylinder.

Compression: Both valves are shut and the piston moves upwards to compress thefuel-air mix. The spark plug res just before the piston reaches its top deadcentre postion (the position where the piston reaches its maximum ver-tical location). This initiates the combustion of the mixture.Power: Again both valves are closed. The hot gases due to the combustion of thefuel air mix drive the cylinder down. The connecting rod transfers thislinear motion of the piston to rotational motion of the crankshaft. Thetorque thus applied to the crankshaft can be used to drive a mechanism,such as the blades of a lawn mower.

Exhaust: The exhaust valve opens and the upward motion of the piston drives theexhaust gasses out of the cylinder.


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Multibody system:-

Introduction:-The systematical treatment of the dynamic behavior ofinterconnected bodies has led to a large number of important multibodyformalisms in the field of mechanics. The simplest bodies or elements of amultibody system were already treated by Newton (free particle) and Euler(rigidbody). Euler already introduced reaction forces between bodies. Later on, a seriesof formalisms have been derived, only to mention Lagranges formalisms based on

minimal coordinates and a second formulation that introduces constraints.

Basically, the motion of bodies is described by its kinematics behavior. Thedynamic behavior results due to the equilibrium of applied forces and the rate ofchange in the momentum. Nowadays, the term multibody system is related to alarge number of engineering fields of research, especially in robotics and vehicledynamics. As an important feature, multibody system formalisms usually offer an
http://en.wikipedia.org/wiki/Mechanicshttp://en.wikipedia.org/wiki/Isaac_Newtonhttp://en.wikipedia.org/wiki/Leonhard_Eulerhttp://en.wikipedia.org/wiki/Joseph_Louis_Lagrangehttp://en.wikipedia.org/wiki/Kinematicshttp://en.wikipedia.org/wiki/Analytical_dynamicshttp://en.wikipedia.org/wiki/Mechanicshttp://en.wikipedia.org/wiki/Isaac_Newtonhttp://en.wikipedia.org/wiki/Leonhard_Eulerhttp://en.wikipedia.org/wiki/Joseph_Louis_Lagrangehttp://en.wikipedia.org/wiki/Kinematicshttp://en.wikipedia.org/wiki/Analytical_dynamics


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algorithmic, computer-aided way to model, analyze, simulate and optimize thearbitrary motion of possibly thousands of interconnected bodies.

Applications

While single bodies or parts of a mechanical system are studied in detailed withfinite element methods, the behavior of the whole multibody system is usuallystudied with multibody system methods within the areas:

Physics engine Robotics Vehicle simulation (vehicle dynamics, rapid prototyping of vehicles,

improvement of stability, comfort optimization, improvement ofefficiency, ...)

Biomechanics Aerospace engineering (helicopter, landing gears, behavior of machines

under different gravity conditions) Combustion engine , gears and transmissions, chain drive, belt drive Hoist , conveyor, paper mill Particle simulation (granular media, sand, molecules) Dynamic simulation Military applications

Example:-

The following example shows a typical multibody system. It is usually denoted asslider-crank mechanism. The mechanism is used to transform rotational motioninto translational motion by means of a rotating driving beam, a connection rodand a sliding body. In the present example, a flexible body is used for theconnection rod. The sliding mass is not allowed to rotate and three revolute jointsare used to connect the bodies. While each body has six degrees of freedom inspace, the kinematical conditions lead to one degree of freedom for the whole

system.
http://en.wikipedia.org/wiki/Physics_enginehttp://en.wikipedia.org/wiki/Physics_enginehttp://en.wikipedia.org/wiki/Roboticshttp://en.wikipedia.org/wiki/Roboticshttp://en.wikipedia.org/wiki/Vehicle_dynamicshttp://en.wikipedia.org/wiki/Rapid_prototypinghttp://en.wikipedia.org/wiki/Biomechanicshttp://en.wikipedia.org/wiki/Biomechanicshttp://en.wikipedia.org/wiki/Aerospace_engineeringhttp://en.wikipedia.org/wiki/Aerospace_engineeringhttp://en.wikipedia.org/wiki/Combustion_enginehttp://en.wikipedia.org/wiki/Combustion_enginehttp://en.wikipedia.org/wiki/Chain_drivehttp://en.wikipedia.org/wiki/Belt_drivehttp://en.wikipedia.org/wiki/Hoist_(device)http://en.wikipedia.org/wiki/Hoist_(device)http://en.wikipedia.org/wiki/Conveyorhttp://en.wikipedia.org/wiki/Paper_millhttp://en.wikipedia.org/w/index.php?title=Particle_simulation&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Particle_simulation&action=edit&redlink=1http://en.wikipedia.org/wiki/Dynamic_simulationhttp://en.wikipedia.org/wiki/Dynamic_simulationhttp://en.wikipedia.org/wiki/Physics_enginehttp://en.wikipedia.org/wiki/Roboticshttp://en.wikipedia.org/wiki/Vehicle_dynamicshttp://en.wikipedia.org/wiki/Rapid_prototypinghttp://en.wikipedia.org/wiki/Biomechanicshttp://en.wikipedia.org/wiki/Aerospace_engineeringhttp://en.wikipedia.org/wiki/Combustion_enginehttp://en.wikipedia.org/wiki/Chain_drivehttp://en.wikipedia.org/wiki/Belt_drivehttp://en.wikipedia.org/wiki/Hoist_(device)http://en.wikipedia.org/wiki/Conveyorhttp://en.wikipedia.org/wiki/Paper_millhttp://en.wikipedia.org/w/index.php?title=Particle_simulation&action=edit&redlink=1http://en.wikipedia.org/wiki/Dynamic_simulation


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The motion of the mechanism can be viewed in the following gif animation

Concept:-

A body is usually considered to be a rigid or flexible part of a mechanical system(not to be confused with the human body). An example of a body is the arm of arobot, a wheel or axle in a car or the human forearm. A link is the connection oftwo or more bodies, or a body with the ground. The link is defined by certain

(kinematical) constraints that restrict the relative motion of the bodies. Typicalconstraints are:

spherical joint ; constrains relative displacements in one point, relativerotation is allowed; implies 3 kinematical constraints

revolute joint ; only one relative rotation is allowed; implies 5 kinematicalconstraints; see the example above

prismatic joint ; relative displacement along one axis is allowed, constrainsrelative rotation; implies 5 kinematical constraints

There are two important terms in multibody systems: degree of freedom andconstraint condition.
http://en.wikipedia.org/wiki/Spherical_jointhttp://en.wikipedia.org/wiki/Spherical_jointhttp://en.wikipedia.org/wiki/Revolute_jointhttp://en.wikipedia.org/wiki/Revolute_jointhttp://en.wikipedia.org/wiki/Prismatic_jointhttp://en.wikipedia.org/wiki/Prismatic_jointhttp://en.wikipedia.org/wiki/File:Slidercrank_animation.gifhttp://en.wikipedia.org/wiki/File:Example_MBS.jpghttp://en.wikipedia.org/wiki/Spherical_jointhttp://en.wikipedia.org/wiki/Revolute_jointhttp://en.wikipedia.org/wiki/Prismatic_joint


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Degree of freedom

The degrees of freedom denote the number of independent kinematical possibilitiesto move. A rigid body has six degrees of freedom in the case of general spatial

motion, three of them translational degrees of freedom and three rotational degreesof freedom. In the case of planar motion, a body has only three degrees of freedomwith only one rotational and two translational degrees of freedom.

The degrees of freedom in planar motion can be easily demonstrated using e.g. acomputer mouse. The degrees of freedom are: left-right, up-down and the rotationabout the vertical axis.

The degree of freedom of slider crank mechanism is 4.

Constraint condition:-

A constraint condition implies a restriction in the kinematical degrees of freedomof one or more bodies. The classical constraint is usually an algebraic equation thatdefines the relative translation or rotation between two bodies. There arefurthermore possibilities to constrain the relative velocity between two bodies or abody and the ground. This is for example the case of a rolling disc, where the pointof the disc that contacts the ground has always zero relative velocity with respectto the ground. In the case that the velocity constraint condition cannot be integrated

in time in order to form a position constraint, it is called non-holonomic. This is thecase for the general rolling constraint. In addition to that there are non-classicalconstraints that might even introduce a new unknown coordinate, such as a slidingjoint, where a point of a body is allowed to move along the surface of anotherbody. In the case of contact, the constraint condition is based on inequalities andtherefore such a constraint does not permanently restrict the degrees of freedom ofbodies.
http://en.wikipedia.org/wiki/Constraint_algorithmhttp://en.wikipedia.org/wiki/Constraint_algorithm

final term paper of dom

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