2 Objectives ofpresent work 1. TO generate Numericalfinite element models to investigate the structural and dynamic behavior of avibrating screen.2. To study the stressdistribution on the vibrating box and vibrating frame under current operatingcondition.
3. To study the stressconcentration on the vibrating box and vibrating frame under current operatingcondition.4. Resonable selection ofvibrating screen working frequency. Chapter 3 Working Conditions Of Inline Knockout Machine The unit consists of the freely suspended screen and ashaft assembly carried by the box. Near each end of the shaft, an eccentricportion is turned.
The shaft is counterbalanced, by weighted fly-wheels,against the weight of the screen and loads that may be superimposed on it. Whenthe shaft rotates, eccentric motion is transmitted from the eccentric portions,through the two bearings, to the screen frame. Frameis mounted on vibrating box with the help of two steel angels. Two L shapedangular plates restricts the motion on screen. The vibrations are transferredfrom torsion bars to screen. Spring dampers are mounted as per the load tobe applied on the vibrating screen, two on each side for damping purpose andgrounded. 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 * Table 3.1-Properties Of SpringDamper Stiffness values of spring iscalculated by using above property and used in the modal analysis as one of theinput value. Damping factor is also one of the property to be used in harmonicanalysis.
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 ModelingOf The Component _____________________________________________________ For the failure analysis of the knockout machine the maincomponents to be considered are vibrating box and vibrating screen. During thecycle of process effect of vibration is mainly observed on the side plate ofthe box, secondly the vibrating screen also suffers failure as result offrequent loading of mold boxes. The vibrating box is divided into two parts: Vibratingframe and screen frame. Screen is installed in the interior of screen frame.The box is located on the vibration damper using springs. Material enters intothe upper ports of vibrating box and is discharged through the bottom portsduring the working. Because of the complex of structure and too many parts ofscreen and screen frame, the finite element models of them are very difficultto be building by using the ANSYS. Because CAD is mature and operationalsoftware, it can quickly create virtual models of screen and screen frame.
Therefore, the combination of CAD and ANSYS is very necessary for analyzingvibrating screen. The combination can improve the speed of changing model andthe efficiency of analyzing vibrating screen .The CAD model was changed into astandard format which can is imported into ANSYS in order to get finite elementmodel. CATIA allows the creation of 3D areas, from 3D images,sheet metal, compounds, shaped, made or pedaling areas up to the meaning oftechnical devices. The application provides advanced technological innovationfor technical appearance.
It provides tools to complete product meaning, suchas functional specifications as well as kinematics meaning. CATIA provides anextensive variety of applications. CATIA v5 is able to read and produce STEPformat files for reverse technological innovation and surface recycling. Forthe analysis purpose following 2 components is considered:- 1.Vibrating box 2. Vibrating screen1.Vibrating Box-Vibrating box is maincomponent of inline knockout machine which supports all other components suchas frame, dampers ,torsion bar, angle plates etc.
generally the box iscombination of welding and bending process. Torsion bar is mounted by bolting acircular plate inside the box plate. The screen is mounted with the help ofangle plate.one net like structure is present at the top of screen but is notconsidered in analysis. Fig 4.
1.1-Isometric View Of Inline knockout Machine Fig 4.1.
2- Detailed Drawing Of Vibrating Box 2.Vibrating Frame-Vibratingscreen is the second part under consideration for analysis. Function of thescreen is to support vibrating net. Mold boxes and castings passes over thisnet. Vibrating screen act as a support for the vibrating box and does not allowthem to scatter over the surface.
Fig 4.1.2-Detailed Drawing Of Vibrating Screen CHAPTER5 ANALYSIS OF THE COMPONENTS_____________________________________________________ Forthe Failure analysis of the machine, modal analysis and harmonic analysisrequired to be carried out: 1. ModalanalysisModal analysis is used to determine a structure’s vibration characteristics naturalfrequencies and mode shapes. Different mode shapes for different frequencies ofstructure can be determined in modal analysis. In modal analysis no any Pre-Stress and preloading’s are appliedto the structure. Only different types of supports are considered in theanalysis.
The results of modal analysis is naturalfrequencies and the corresponding formation that only related to the inherentcharacteristics of the system and free from external forces and the method offixing. Natural characteristic includes natural frequency, natural vibrationmodes and other modal. Parameters. The purpose of natural characteristicanalysis is to avoid resonance and harmful vibration modes and improve the reliabilityand service life of screen and screen frame. 2.Harmonic AnalysisThe 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. 5.1 Dynamic FiniteElement Model-The geometric model of the screen box must be make some correspondingsimplifies as possible to reflect the true characteristics of its mainstructure under the premise of units less to use or the simple unit form forfinite element model.The followingsimplified steps are taken:(a) Some smallconnectors, fixing bracket, other non-bearing components and functional partsare omitted. (b) Allchamfers, fillets, rivets and welding spots are ignored which are not the majorfactors to reduce the workload of the modeling. (c) Ignore thetechnological holes and bound holes on the screen box as such small diameterholes has little effect on general strength and stiffness of the structure, butthe mesh units will greatly increase.
(d) The parts of screen box are thin-walledplate except the motor base. Fig 5.1 -CAD Model OfInline Konckout Machine 5.
2 Connectionsand preloading – Import the modal in the ANSYS for the analysispurpose. 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’s1.body-body type 2.Body- ground type. We have usedbody-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 ofbody, it will act as base of spring damper. Scoping- the working part of springis considered as mobile direction of body, the direction in which spring isgoing to experience compression or expansion. By considering all aboveexplanation constraints of spring will be GROUND to part 325121 00 003 (upperpart of spring damper support)Stiffness ofspring 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 alsoconsidered in the analysis because spring may suffer pre deformation due theload applied by the whole structure. Approximately 3 ton preload is applied onthe spring.
in this analysis only one spring is considered as working condition. 5.3Meshing of model- Imported model from CATIA is required to mesh forfurther analysis. Efforts are made to achieve finer mesh for accuracy ofresults. Finer mesh on the parts likes vibrating box, torsion bar support isachieved 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 theseparts, also considering time consumed for analysis it is not convenient to achievethe finer mesh for all the components. Fig 5.
3.1meshed model of Inline Knockout MachineFor meshing first auto mesh is generated, facesizing and edge sizing is applied on the edges of circular part and face sizingis applied on side walls of the box. Mesh is hex dominant in meshing number ofnodes formed are 403425 and number of elements are 57722. Chapter 6 MODAL ANALYSIS____________________________________________________For the model analysis materialused 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 Table no 6.1 –Material propertiesof mild steel In modal analysis we haveconsidered here first ten modes of vibration for analysis.
i.e the behavior ofthe system for first ten mode and its corresponding frequencies. 1. First mode – Mode Effect Name of part Deformation (mm) 1 Minimum 325 121 00 005 Default
78 Fig6.1-Total deformation-1 at frequency 0 HZ 2. Second Mode- Mode Effect Name of part Deformation (mm) 2 Minimum 325 121 00 005 Default
5326e-010 Maximum 325 121 00 013-6 130.58 Fig6.2-Total deformation-2 at frequency 0 HZ3. Third Mode- Mode Effect Name of part Deformation (mm) 3 Minimum 325 121 00 005_Default
3181e-009 Maximum 325 121 00 003 4.4984 Fig6.4-Total deformation-4 at frequency 0 HZ 5. Fifth Mode- Mode Effect Name of part Deformation (mm) 5 Minimum 325 121 00 005_Default
7307e-010 Maximum 325 121 00 013_Default
Seventh Mode- Mode Effect Name of part Deformation (mm) 7 Minimum 325 121 00 005_Default
7 mm Fig 6.8-Total deformation-8 at frequency 0.00055697HZ 9. Ninth Mode- Mode Effect Name of part Deformation (mm) 9 Minimum 325 121 00 005_Default
0005898 Hz. 10. Tenth Mode- Mode Effect Name of part Deformation (mm) 10 Minimum 325 121 00 018_Default
666 mm Fig 6.10- Total deformation-10at frequency 0.00060832 Hz.
Thefollowing bar chart indicates the frequency at each calculated mode. Fig 6.1 frequency at each calculatedmode. Mode Frequency Hz CHARACTERSTIC OF VIBRATION MODE 1. 0. Rigid motion(translational motion, pitch vibration) along x,y,z axis at second compartment. 2.
Rigid motion along x,y,z axis, at fourth compartment. 3. Rigid motion along x,y,z axis, at third compartment. 4. Displacement at damper support.
5. Rigid motion along x,y,z axis, at fourth compartment. 6. Rigid motion along x,y,z axis, at fourth compartment.
7. 0.00023262 Rigid motion along x,y,z axis, at third compartment. 8.
0.00055697 Rigid motion along x,y,z axis, at first compartment. 9. 0.0005898 Rigid motion along x,y,z axis, at third compartment 10. 0.
00060832 Rigid motion along x,y,z axis, supporting L plates of screen Table 6.2 -different modes of naturalfrequencies Chapter 7REFERENCES____________________________________________________ 1. Mr Boitumelo Ramatsetse”Failure and Sensitivity Analysis of a Reconfigurable Vibrating Screen UsingFinite Element Analysis”, “Case Studies In Engineering Failure Analysis”.2. SergioBaragetti “Innovative structural solution for heavy loaded vibrating screens”, MineralsEngineering 84 (2015) 15–26.3.
YongjunHou, Pan Fang and Lian Zeng,” FiniteElement Analysis of Dual-frequency Vibrating Screen”, Advanced Materials ResearchVols. 479-481 (2012) pp 2124-2128.4. LiuXinyong,Cui Hongbin,Cao Pengxian,Bao Xuechun,Liu Xinyu, “TQLZ Self-balance Vibrating Screen Static andModal Analysis”, Advanced Materials ResearchVol. 852 (2014) pp 619-623.5.
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Luo, W.J. Mortel, X.P. Wu, “Fatigue failureinvestigation on anti-vibration springs” Engineering Failure Analysis 16 (2009)1366–1378.