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

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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)

Boitumelo Ramatsetse 1 described in mineral processing

industries vibrating screens operate under high structural loading and

continuous vibrations. In this regard, this may result high strain rates, which

may often lead to structural failure or damage to the screen. In order to

lessen the possibility of failure occurring, theories and techniques for

analyzing machine structures are investigated and applied to perform a sensitivity

study of a newly developed vibrating screen. Structural strength and stability

of a vibrating screen is essential to insure that failure doesn’t occur during

production. In this paper a finite element analysis (FEA) on a reconfigurable

vibrating screen (RVS) is carried out to determine whether the structure will

perform as desired under extreme working conditions at the different

configurations of 305mm×610mm, 305mm×1220mm and 610mm×1220mm.This process is

aimed at eliminating unplanned shutdowns and minimizes maintenance cost of the

equipment. Each component of a screen structure is analyzed separately, stress

and displacement parameters are determined based on dynamic analysis. In

addition, a modal analysis was carried out for the first three (3) modes at

frequency f of 18.756 Hz, 32.676 Hz and 39.619 Hz respectively. The results

from the analysis showed weak points on the side plates of screen structure.

Sergio

Baragetti 2 An innovative design solution is

presented in this paper; it allows the enhancement of structural Resistance and

the dynamic performances of a vibrating screen for inert materials. The new

design does not significantly affect the geometry of the traditional screens,

keeping the same global dimensions and almost the same mass value. In fact the

aim of this study was to design a new vibrating screen having almost the same

dimensions but that could give a much higher dynamic structural resistance at

frequencies and load amplitudes much higher than the nominal ones. Numerical

finite element models were generated to investigate the structural and dynamic

behavior of a standard vibrating screen. These analyses allowed the

modification of the geometrical parameters of the traditional screen and to

design the new one. Accurate three-dimensional FE models were so generated in

order to evaluate the best design solution, in terms of dynamic structural

resistance, able to reduce the stress values at the most stressed area. The

fatigue resistance of all the components of the new screen was checked, with

particular attention to the welding joints. Experimental full scale tests on a

prototype of the new screen were carried

out in order to validate the

numerical models and mostly to verify the structural integrity of the vibrating

screen during the working conditions. Strains at the surface of the most

stressed areas of the screen were measured in dynamic working conditions, at

different frequencies and load amplitudes; these stress values were compared

with the numerical ones in order to validate the numerical results. The new

screen was patented.

Zhao Yue-mina, Liu Chu-shenga3 The reliability is a key factor

for the design and manufacture of large vibrating screen. In the paper, He

presented a new large vibrating screen with hyperstatic net-beam structure.

Dynamic characteristic of the vibrating screen was researched and dynamic

simulation method of large screening machines was explored. He used finite

element method (FEM) to analyze dynamic characteristic of large vibrating

screen with hyperstatic net-beam structure. Multi natural frequency, natural

modes of vibration and dynamic response of the vibrating screen were

calculated. The structural size of stiffeners on the side plate was optimized

under multiple frequencies constraints and an adaptive optimization criterion

was given. The results show that the vibrating screen’s structural strength is

increased and the natural frequency of bending deformation is enhanced. The

modal frequencies are far from working frequency, and thus the structure is

able to avoid resonance effectively and reduce the destructiveness. The maximum

transverse displacement of the vibrating screen is 0.13 mm, the maximum

difference in vibration amplitude of corresponding points is 0.44mm and the

maximum dynamic stress is 16.63MPa. The structural optimization shows that the

mass of the side plate is decreased by 194.50kg, the second and third modal

frequency is increased by 1.73% and 2.91% respectively and a better optimal

effect is received.

Yongjun Hou, Pan Fang and Lian Zeng 4 In order to study the stress

distribution of dual-frequency vibrating screen and ensure the screen box has

sufficient strength and longevity, a finite element model of dual-frequency

vibrating screen was built, and the stress, modes and fatigue life of the

screen box were analyzed. The results indicate that, the stress concentration

appears at the contacting parts between the crossbeam and the stiffener of

motor seat, the crossbeam, L-type stiffening plate, baffle of material added

and screen box. The middle of crossbeam and the L-type stiffening plate are

weaker parts of fatigue; they are easily fatigue failure under high frequency

vibration

Liu

Xinyong ,Cui Hongbin ,Cao Pengxian15 A simplified model of self-balance screen was constructed

by using SolidWorks, and then imported into the Simulation to analysis its

structure and modal. The stress distribution, deformation and structural

natural frequency, mode shapes under static loads of the self-balance vibrating

screen were calculated to provide theoretical basis for the following analysis

of the dynamic characteristics and structure optimization design of vibrating

screen.

I.B. Eryu¨ rek, M. Ereke, A. Go¨ ksenli 6 In this paper the failure of the rear

suspension spring is analyzed in detail. The rear axle suspension system of the

truck and fractured flat spring is investigated. Fracture surface, mechanical

and chemical properties and microstructure of the spring material is analyzed.

A force acting on the spring is determined and strength calculations are

carried out. Later, failure behavior and cause of fracture is revealed after carefully analysis of

microstructure and results of calculations. At the end precautions to be taken

to prevent a similar failure is recommended.

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

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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.

REFERENCES

IEEE format: for students of Electronics/Digital system/

Power system/CSE

ASCE format: for students of Structure/Construction &

management

ASME format: for students of Automobile/Production/

Design/CAD-CAM-CAE/Heat Power