Chapter in vibrating direction and amplitude of exciting

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Chapter in vibrating direction and amplitude of exciting

Chapter 1

INTRODUCTION
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1.1   
Introduction

        Inline knockout machine is a kind of machine widely used in foundries for clean-up and separating castings and mold box. Machine is suitable for the above purpose because of simplicity of structure, reliability and provision for adjustment in vibrating direction and amplitude of exciting force. Main components of Inline Knockout Machine mainly consist of torsion bar, vibrating frame, vibrating box, vibrating motors installed on both sides of the vibrating box, spring and support device. When it works, the two vibrating motors rotate synchronously in the reverse direction. The vibration force in the vibration direction is generated by two vibration motors and the excitation force in the vertical vibration direction is equal to zero resulting in a straight line or an approximately straight line motion.

 

fig

The vibrating box may break in the
long-term work, especially the sides of the   vibrating box may suffer Fracture, and also
vibrating frame may suffer fracture in its structure. The main cause of mechanical failure in vibrating screen is the
vibration. Components like frame, vibrating box, spring dampers and bearings
are affected by this. The vibration will crystallize the molecular structure of
the metal causing what is known as metal fatigue to develop. The first sign
that an operator has indicating that the fatigue in the body of the screen deck
is almost at a critical stage in its development are the hairline cracks that
will appear around the vibration’s point of origin. This work adopted
components of inline knockout machine such as vibrating box, vibrating frame as
the object to study and analyze the stress distribution and deformation under
static loads, check the strength of vibrating box and analyze whether it will
resonate by calculating the natural frequencies and mode shapes of the
structure.

 

 

  1.2 Vibrating Screen Working
Principle 

The
simplest Vibrating Screen Working Principle can be
explained using the single deck screen and put it onto an inclined frame. The
frame is mounted on springs. The vibration is generated from an unbalanced
flywheel.

Fig1.2.1. inline knockout machine

   The vibration pattern of the horizontal frit
is back and forth and the inclined vibrating screen is round. There are
different ways to produce the vibration itself. The horizontal screen uses a
double balance system. A very erratic motion is
developed when this wheel is rotated.  A
double counterbalance system is used in the horizontal screen. The
counterbalance weight will alternately promote and retard the direction of
vibration depending upon where within each revolution the weights come opposite
each other.

 

              Fig 1.2.2. Counterbalance weight

Eccentric shaft is used in the inclined
vibrating screen. The vibration of an   unbalanced
flywheel is very violent. This causes mechanical failure and structural damage
to occur. The four bearing system greatly reduces this problem.

 

 

 

 

1.2   
Motivation Of The Present Work

 

            Inline
knockout machine consist of component like torsion bar,
vibrating frame, vibrating box, vibrating motors installed on both sides of the
vibrating box, spring and support device. Vibrating box may be damaged during long-term operation.
In particular, the sides of the vibrating box may break, and the structure of
the vibrating frame may also break.

The main cause of mechanical failure in
vibrating screen is the vibration. Components like frame, vibrating box, spring
dampers and bearings are affected by this. The first sign that an operator has
indicating that the fatigue in the body of the screen deck is almost at a
critical stage in its development are the hairline cracks that will appear
around the vibration’s point of origin. Failure analysis of above components will
give a closer theoretical look at the behavior of the above mentioned
components.

 

 

 

 

 

 

 

 

 

 

 

Chapter 2

 

LITERATURE
REVIEW
______________________________________________________

 

2   
 

2.1    Introduction

 

 

2.2    Classification of Literature
Review

 

2.2.1       
Classification
A

Report on major literature
referred and studied. Literature review should include current thinking,
findings, and approaches to the problem. Following citation format should be
adopted. Generally there are two types of citation formats are adopted.

Turner (1963) presented
analysis of structures using stiffness matrix method. Patil and Kulkarni (1990)
developed Sample Large-Angle-of-Attack Viscous Hypersonic Flows over Complex
Lifting Configurations. Various research carried out in debris and referred
from (Jadhav, 1990). Deshpande et al. (1998) revealed new development of
analytical tools.

Citations

Initially
this work is proposed by Patil (2011)

Initially
this work is proposed by Patil  and Kadam
(2011)

Initially
this work is proposed by Patil et al.
(2011)

 

 

 

 

 

 

 

 

2.3 Objectives of
present work

1.     
TO generate Numerical
finite element models to investigate the structural and dynamic behavior of a
vibrating screen.

2.     
To study the stress
distribution on the vibrating box and vibrating frame under current operating
condition.

3.     
To study the stress
concentration on the vibrating box and vibrating frame under current operating
condition.

4.     
Resonable selection of
vibrating screen working frequency.

 

 

Chapter 3

 

 Working
Conditions Of Inline Knockout Machine

 

The unit consists of the freely suspended screen and a
shaft assembly carried by the box. Near each end of the shaft, an eccentric
portion is turned. The shaft is counterbalanced, by weighted fly-wheels,
against the weight of the screen and loads that may be superimposed on it. When
the shaft rotates, eccentric motion is transmitted from the eccentric portions,
through the two bearings, to the screen frame.

Frame is mounted on vibrating box with the help of two
steel angels. Two L shaped angular plates restricts the motion on screen. The
vibrations are transferred from torsion bars to screen.

Spring dampers are mounted as per the load to
be applied on the vibrating screen, two on each side for damping purpose and
grounded.

 

Property

Specification(mm)

Wire diameter

19

Inner diameter

90

Outer diameter

128

Length

315

Pitch

39.37

Number of
turns

8

stiffness

120.94 N/mm^2
*

 

 

Stiffness values of  spring is calculated by using above property
and used in the modal analysis as one of the input value. Damping factor is
also one of the property to be used in harmonic analysis.
Stiffness of spring calculation –

 

1.?=8pd^3N/gd^4

  =8*39200*(109)^3*8/76920*19^4

  =324.109mm

 

2.k=p/ ?

     =39200/324.109

     =120.94 N/mm^2

 

       CHAPTER 4

 

    Modeling
Of The Component

 

For
the failure analysis of the knockout machine the main components to be
considered are vibrating box and vibrating screen. During the cycle of process
effect of vibration is mainly observed on the side plate of the box, secondly
the vibrating screen also suffers failure as result of frequent loading of
mould boxes.

The vibrating
box is divided into two parts: Vibrating frame and screen frame. Screen is
installed in the interior of screen frame. The box is located on the vibration
damper using springs. Material enters into the upper ports of vibrating box and
is discharged through the bottom ports during the working.

Because
of the complex of structure and too many parts of screen and screen frame, the
finite element models of them are very difficult to be building by using the
ANSYS. Because CAD is mature and operational software, it can quickly create
virtual models of screen and screen frame. Therefore, the combination of CAD
and ANSYS is very necessary for analyzing vibrating screen. The combination can
improve the speed of changing model and the efficiency of analyzing vibrating
screen .The CAD model was changed into a standard format which can is imported
into ANSYS in order to get finite element model.

CATIA
allows the creation of 3D areas, from 3D images, sheet metal, compounds,
shaped, made or pedaling areas up to the meaning of technical devices. The
application provides advanced technological innovation for technical
appearance. It provides tools to complete product meaning, such as functional specifications
as well as kinematics meaning. CATIA provides an extensive variety of
applications. CATIA v5 is able to read and produce STEP format files for
reverse technological innovation and surface recycling.

For
the analysis purpose following 2 components is considered:-

1.
Vibrating box

2. Vibrating screen

 

1. Vibrating Box-

            Vibrating box is main
component of inline knockout machine which supports all other components such
as frame, dampers ,torsion bar, angle plates etc. generally the box is
combination of welding and bending process.Torsion bar is mounted by bolting a
circular plate inside the box plate. The screen is mounted with the help of
angle plate.one net like structure is present at the top of screen but is not
considered in analysis.

 

Fig 4.1.1-Isometric View Of Inline knockout Machine

 

 

 

 

 

     Fig4.1.2- Detailed Drawing
Of Vibrating Box

 

 

 

 

 

 

 

 

 

 

2.Vibrating Frame-

Vibrating screen is the second part under consideration for analysis.
Function of the screen is to support vibrating net.mold boxes and castings
passes over this net. Vibrating screen act as a support for the vibrating box
and doesnot allow them to scatter over the surface.

 

 

       Fig 4.1.3- Detailed
Drawing Of Vibrating Screen

 

 

 

 

 

 

 

 

 

 

 

  
CHAPTER
5

 

                    ANALYSIS OF THE COMPONENTS

 

For
the Failure analysis of the machine, modal analysis and harmonic analysis
required to be carried out:

 

1.Modal analysis

Modal analysis is used to determine a structure’s vibration characteristics natural
frequencies and mode shapes. Different mode shapes for different frequencies of
structure can be determined in modal analysis. In modal analysis no any Pre-Stress and preloading’s are
applied to the structure. Only different types of supports are considered in
the analysis. The results of modal analysis is natural
frequencies and the corresponding formation that only related to the inherent
characteristics of the system and free from external forces and the method of
fixing. Natural characteristic includes natural frequency, natural vibration
modes and other modal. Parameters. The purpose of natural characteristic
analysis is to avoid resonance and harmful vibration modes and improve the
reliability and service life of screen and screen frame.

 

2.
Harmonic Analysis

The dynamic response of the vibrating screen at any moment can be obtained by finite element analysis and the stress distribution and weak point of the vibrating screen can be displayed on the operating frequency by harmonic analysis. In this type of analysis all  types of force, pressure, moment, displacement, nodal support, fixed support, elastic support, friction less support can be applied for the analysis. 

 

 

 

 

Dynamic Finite
Element Model-

The geometric
model of the screen box must be make some corresponding simplifies as possible
to reflect the true characteristics of its main structure under the premise of
units less to use or the simple unit form for finite element model.

The following
simplified steps are taken:

(a) Some small
connectors, fixing bracket, other non-bearing components and functional parts are
omitted.

(b) All
chamfers, fillets, rivets and welding spots are ignored which are not the major
factors to reduce the workload of the modeling.

(c) Ignore the
technological holes and bound holes on the screen box as such small diameter
holes has little effect on general strength and stiffness of the structure, but
the mesh units will greatly increase.

 (d) The parts of screen box are thin-walled
plate except the motor base.

Fig 5.1 -CAD Model
Of Inline Konckout Machine

 

 

 

Connections
and preloading –

          Import the modal in the ANSYS for the analysis
purpose. Auto connection feature is used to define all the connection of the geometry.
Spring is used as one more connection for dampers; there are two types of spring’s
1.body-body type 2.Body- ground type.

We have used
body-ground type spring here in this type of spring reference is grounded
(fixed) to the ground i.e there is no any directional moment along any side of body,
it will act as base of spring damper. Scoping- the working part of spring is considered
as mobile direction of body, the direction in which spring is going to experience
compression or expansion. By considering all above explanation constraints of
spring will be GROUND to part 325121 00 003 (upper part of spring damper
support)

Stiffness of
spring 120.94 N/mm^2 is used as one of the input characteristic of spring.
Preloading i.e the approximate load which is acting on the spring is also considered
in the analysis because spring may suffer pre deformation due the load applied
by the whole structure. Approximately 3 ton preload is applied on the spring.in
this analysis only one spring is considered as working condition.

Meshing
of model-

            Imported model from CATIA is required to mesh for
further analysis. Efforts are made to achieve finer mesh for accuracy of results.
Finer mesh on the parts likes vibrating box, torsion bar support is achieved because
these component suffer frequent failure during working, components like frame,
supports of damper, angle plates for supporting frame etc. are relatively less finely
meshed because the failure is not frequent for these parts, also considering
time consumed for analysis it is not convenient to achieve the finer mesh for
all

The components.

 

 

 

 

 

 

 

           

For meshing first auto mesh is generated, face
sizing and edge sizing is applied on the edges of circular part and face sizing
is applied on side walls of the box. Mesh is hex dominant In meshing number of
nodes formed are 403425 and number of elements are 57722.

 

 

 

 

 

 

 

 

Chapter 5

  MODAL ANALYSIS

____________________________________________________

 

For the model analysis material
used is mild steel. Material properties of mild are as following

 

Property

Value

Modulus Of Rigidity

76.92 Gpa

Modulus Of Elasticity

210000Mpa

Density

7860kg/m^3

Poissons Ratio

0.3

 

In modal analysis we have considered
here first ten modes of vibration for analysis.i.e the behavior of the system
for first ten mode and its corresponding frequencies.

 

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