Acceleration In Mechanisms
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Acceleration In Mechanisms as PDF for free.
More details
- Words: 582
- Pages: 22
Topic
ACCELERATION IN MECHANISMS
CONTENTS 1) 2) 3) 4) 5)
Define mechanism Acceleration diagram for a link Acceleration of a point on a link Acceleration in the slider crank mechanisms Coriolis component of acceleration
INTRODUCTION The acceleration analysis plays a very important role in the development of machines and mechanisms.
MECHANISM A mechanism is used to produce mechanical transformations in a machine. This transformation could be any of the following. 3)It
may convert one speed to another speed.
4)It
may convert one force to another force.
5)It
may convert one torque to another torque. 6)It
may convert force into torque.
7)It
may convert one angular motion to another angular motion. 8)It
may convert angular motion into linear motion. 9)It
may convert linear motion into angular motion.
EXAMPLE OF MECHANISM
Can crusher Simple press
Rear-window wiper 6
EXAMPLE OF MECHANISMS
Rowing type exercise machine Conceptual design for an exercise machine 7
EXAMPLE OF MECHANISM •
A good example is a crank, connecting rod and piston mechanism.
•
If the crank is turned, angular motion is converted into linear motion of the piston and input torque is transformed into force on the piston.
CONSIDER THE NEXT MECHANISM USED IN SHAPING MACHINES AND ALSO KNOWN AS THE WHITWORTH QUICK- RETURN MECHANISM.
ACCELERATION DIAGRAMS It is important to determine the acceleration of links because acceleration produces inertia forces in the link which stress the component parts of the mechanism. Accelerations may be relative or absolute.
INERTIA FORCE
One of the reasons for finding the acceleration of links is to calculate the inertia force needed to accelerate or decelerate it. This is based on Newton’s second law.
Force = mass x acceleration F = M a
Torque = moment of inertia x angular acceleration T = Iα
ACCELERATION DIAGRAM FOR A LINK
ACCELERATION OF A PARTICLE WHOSE VELOCITY CHANGES BOTH IN MAGNITUDE AND DIRECTION AT ANY INSTANT HAS THE FOLLOWING TWO COMPONENTS :
The centripetal or radial component, which is perpendicular to the velocity of the particle at the given instant. 2. The tangential component, which is parallel to the velocity of the particle at the given instant.
CENTRIPETAL OR RADIAL COMPONENT
This radial component of acceleration acts perpendicular to the velocity VBA, In other words, it acts parallel to the link AB.
TANGENTIAL COMPONENT
This tangential component of acceleration acts parallel to the velocity VBA. In other words, it acts perpendicular to the link AB.
ACCELERATION OF A POINT ON A LINK
THE SLIDER-CRANK MECHANISM Another mechanism that is commonly encountered is a slider crank. This mechanism also consists of a combination of four links, with one being designated as the frame. This mechanism, however, is connected by three pin joints and one sliding joints.
17
SLIDER-CRANK MECHANISM Ken Youssefi
The mechanism has a stroke B1B2 equal twice the crank length r2.
UC Berkeley
Locations B1 and B2 are called the extreme positions (limiting) of the slider
In-line slider crank mechanism 18
ACCELERATION DIAGRAM FOR SLIDER CRANK MECHANISM
CORIOLIS COMPONENT OF ACCELERATION When a point on one link is sliding along another rotating link, such as in quick return motion mechanism, then the Coriolis component of the acceleration must be calculated. OR
the Coriolis effect is an apparent deflection of moving objects when they are viewed from a rotating reference frame.
CORIOLIS COMPONENT OF ACCELERATION
THE CORIOLIS COMPONENT OF ACCELERATION IS PRESENT IN (a) 4-bar mechanisms with 4 turning pairs (b) shape mechanism (c) slider-crank mechanism (d) Scotch Yoke mechanism
ACCELERATION IN MECHANISMS
CONTENTS 1) 2) 3) 4) 5)
Define mechanism Acceleration diagram for a link Acceleration of a point on a link Acceleration in the slider crank mechanisms Coriolis component of acceleration
INTRODUCTION The acceleration analysis plays a very important role in the development of machines and mechanisms.
MECHANISM A mechanism is used to produce mechanical transformations in a machine. This transformation could be any of the following. 3)It
may convert one speed to another speed.
4)It
may convert one force to another force.
5)It
may convert one torque to another torque. 6)It
may convert force into torque.
7)It
may convert one angular motion to another angular motion. 8)It
may convert angular motion into linear motion. 9)It
may convert linear motion into angular motion.
EXAMPLE OF MECHANISM
Can crusher Simple press
Rear-window wiper 6
EXAMPLE OF MECHANISMS
Rowing type exercise machine Conceptual design for an exercise machine 7
EXAMPLE OF MECHANISM •
A good example is a crank, connecting rod and piston mechanism.
•
If the crank is turned, angular motion is converted into linear motion of the piston and input torque is transformed into force on the piston.
CONSIDER THE NEXT MECHANISM USED IN SHAPING MACHINES AND ALSO KNOWN AS THE WHITWORTH QUICK- RETURN MECHANISM.
ACCELERATION DIAGRAMS It is important to determine the acceleration of links because acceleration produces inertia forces in the link which stress the component parts of the mechanism. Accelerations may be relative or absolute.
INERTIA FORCE
One of the reasons for finding the acceleration of links is to calculate the inertia force needed to accelerate or decelerate it. This is based on Newton’s second law.
Force = mass x acceleration F = M a
Torque = moment of inertia x angular acceleration T = Iα
ACCELERATION DIAGRAM FOR A LINK
ACCELERATION OF A PARTICLE WHOSE VELOCITY CHANGES BOTH IN MAGNITUDE AND DIRECTION AT ANY INSTANT HAS THE FOLLOWING TWO COMPONENTS :
The centripetal or radial component, which is perpendicular to the velocity of the particle at the given instant. 2. The tangential component, which is parallel to the velocity of the particle at the given instant.
CENTRIPETAL OR RADIAL COMPONENT
This radial component of acceleration acts perpendicular to the velocity VBA, In other words, it acts parallel to the link AB.
TANGENTIAL COMPONENT
This tangential component of acceleration acts parallel to the velocity VBA. In other words, it acts perpendicular to the link AB.
ACCELERATION OF A POINT ON A LINK
THE SLIDER-CRANK MECHANISM Another mechanism that is commonly encountered is a slider crank. This mechanism also consists of a combination of four links, with one being designated as the frame. This mechanism, however, is connected by three pin joints and one sliding joints.
17
SLIDER-CRANK MECHANISM Ken Youssefi
The mechanism has a stroke B1B2 equal twice the crank length r2.
UC Berkeley
Locations B1 and B2 are called the extreme positions (limiting) of the slider
In-line slider crank mechanism 18
ACCELERATION DIAGRAM FOR SLIDER CRANK MECHANISM
CORIOLIS COMPONENT OF ACCELERATION When a point on one link is sliding along another rotating link, such as in quick return motion mechanism, then the Coriolis component of the acceleration must be calculated. OR
the Coriolis effect is an apparent deflection of moving objects when they are viewed from a rotating reference frame.
CORIOLIS COMPONENT OF ACCELERATION
THE CORIOLIS COMPONENT OF ACCELERATION IS PRESENT IN (a) 4-bar mechanisms with 4 turning pairs (b) shape mechanism (c) slider-crank mechanism (d) Scotch Yoke mechanism
Related Documents
Acceleration In Mechanisms
May 2020 0
Acceleration
April 2020 20
Acceleration
May 2020 16
Mechanisms
November 2019 24
Housing Finance Mechanisms In Zimbabwe
July 2020 11