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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

202

Finite Element Modelling and Analysis of BIW Part

Karwande A. H.

1

, Borkar B. R.

2

1Productionl Department (CAD-CAM), Amrutwahini College of Engineering,Pune University, Sangamner, India. 2Assistant Professor, Production Department, Amrutwahini College of Engineering, Pune University, Sangamner, India. Abstract— In this article we are going to analyze the BIW

(Body In White) using ANSYS software under the static loading. The BIW consist mainly two part i.e. top hat and flat plate which are joint together by using laser spot weld. Spot welds made by resistance spot welding are used extensively in automotive engineering. However, owing to increasing demands in the use of advanced and lightweight materials, laser welding has become a popular alternative for producing spot welds. Because of the complexity and uncertainties of laser welds and thus formed structures, the finite-element (FE) modeling of the welds for dynamic analysis is a research issue. In this project first outlines some of the existing modeling of top hat and analyzed by using ANSYS software for different static load and validate by using free hammer test. SOLID 285 (Tetrahedral 4 node 285) elements is used FE modeling. In this work, we are using LVDT accelerometer to calculate the modal frequency of the different BIW part at given static load. Also, by using ANSYS V 12.0 software we going to generate mesh BIW part and model generated by using PRO-E software.

Keywords— BIW, ANSYS 12.0, Free Hammer Test.

I. INTRODUCTION TO WELDING PROCESS

Modern welding technology started just before the end of the 19th century with the development of methods for generating high temperature in localized zones.

Welding generally requires a heat source to produce a high temperature zone to melt the material, though it is possible to weld two metal pieces without much increase in temperature. There are different methods and standards adopted and there is still a continuous search for new and improved methods of welding. As the demand for welding new materials and larger thickness components increases, mere gas flame welding which was first known to the welding engineer is no longer satisfactory and improved methods such as Metal Inert Gas welding,

Tungsten Inert Gas welding, electron and laser beam welding have been developed .In most welding procedures metal is melted to bridge the parts to be joined so that on solidification of the weld metal the parts become united. The common processes of this type are grouped as fusion welding. Heat must be supplied to cause the melting of the filler metal and the way in which this is achieved is the major point of distinction between the different processes.

The method of protecting the hot metal from the attack by the atmosphere and the cleaning or flux in gas way of contaminating surface films and oxides provide the second important distinguishing feature. For example, welding can be carried out under a shield comprising of a mixture of metal oxides and silicates which produce a glass-like flux, or the whole weld area may be swept clear of air by a stream of gas such as argon, helium or carbon dioxide which is harmless to the hot metals.

There is certain solid phase joining methods in which there is no melting of the electrodes, though heat is produced in the process. The melted and solidified cast metal is normally weaker than the wrought metal of the same composition. In the solid phase joining such melting does not occur and hence the method can produce joints of high quality. Metals which are dissimilar in nature can also be readily welded by this process. In the normal process joining of dissimilar metals will present problems because of the brittle inter metallic compounds formed during melting. Since the work pieces are closely pressed together, air is excluded during the joining process.

The welding processes covered in this chapter are gas welding, arc welding which includes manual metal arc welding (MMA), tungsten inert gas shielded arc welding (TIG), gas metal arc welding (MIG, MIG/CO2), submerged arc welding(SAW), etc. High energy density processes like electron beam welding, laser beam welding, plasma welding are also dealt with. Pressure welding and some special welding techniques like electro-slag welding etc.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

203

Joint quality and mechanical behavior are evaluated by energy absorption capability of weld before crack initiation. In these experiments, three overload failure modes were observed; pullout failure is the desirable one which is the ductile mode. Load carrying capacity and energy absorption capability for those welds which fail under the overload pullout mode are more than those welds which fail under the other modes. Optimum process parameters in the studied range were found which would ensure the desirable pullout failure mode and thus maximum failure energy.

II. HAT PLATE MODEL AND FEPRESENTATION

[image:2.612.344.543.120.310.2]

A hat-plate structure shown in Fig.1 is used in this work. The structure, which consists of a flat plate and a formed hat-like shell (or „top-hat‟) joined together by spot welds at the flanges, is designed to represent common structures used in the construction of a car BIW. The spot welds, which are produced by LW, are 5mm in diameter and 60 mm apart in the longitudinal. The hat-plate hat plate dimensions direction. The overall dimensions of the hat plates are as 564 mm long and 110 mm wide. The plates,of thickness 1.5 mm,are made of cold rolled mild steel sheet metal.

Fig. 1 The hat structure

The overall diemention of top hat and flate plate shown in fig 1 by using Pro-E software.A set of nine identical pairsof the structures are built in-house, each having the same nominal dimensions.Nominal values for the material

properties of mild steel are used for both

[image:2.612.336.550.383.575.2]

models,withYoung‟s modulus E = 210GPa, Poisson‟s ratioν= 0.3,and density ρ = 7860kg/m3.

Fig. 2 Part model of top hate diemension in PRO-E

Here,for FE modelling the top hate,flate plate and there assembly is created by using Pro-E software and it is import in ANSYS Autodyne 12.0 for furthe analysis fig 2 top hate diemension in PRO-E and fig.3 gives part model of flat plate in PRO-E software.

Fig.3 Part mpdel of top hat in PRO-E software

III. ACCELEROMETER

[image:2.612.83.252.406.568.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

204

The basic difference is in the method of mass displacement measurement (Free Hammer Test). In general, the specification sheets for an accelerometer will give the natural frequency, damping coefficient, and a scale factor that relates the output to an acceleration input. The values of test mass and spring constant are seldom known or required. There is mainly three type accelerometer as

1] Potentiometric Accelerometer-

This simplest accelerometer type measures mass motion by attaching the spring mass to the wiper arm of a potentiometer. In this manner, the mass position is conveyed as a changing resistance. The natural frequency of these devices is generally less than 30 Hz, limiting their application to steady-state acceleration or low-frequency

vibration measurement. Numerous signal-conditioning schemes are employed to convert the resistance variation into a voltage or current signal.

2] LVDT Accelerometer-

A second type of accelerometer takes advantage of the natural linear displacement measurement of the LVDT as shown in fig 4 to measure mass displacement. In these instruments, the LVDT core itself is the seismic mass. Displacements of the core are converted directly into a linearly proportional ac voltage. These accelerometers generally have a natural frequency less than 80 Hz and are commonly used for steady-state and low-frequency vibration. Fig. 4 shows the basic structure of such an accelerometer.

Fig.4 LVDT Accelerometer

This accelerometer type falls in the same general category as the LVDT in that an inductive principle is employed. Here, the test mass is usually a permanent magnet.

The measurement is made from the voltage induced in a surrounding coil as the magnetic mass moves under the influence of acceleration. This accelerometer is used in vibration and shock studies only, because it has an output

only when the mass is in motion. Its natural frequency is typically less than 100 Hz. This type of accelerometer often is used in oil exploration to pick up vibrations reflected from underground rock strata.

3] Piezoelectric Accelerometer-

The piezoelectric accelerometer is based on a property exhibited by certain crystals where a voltage is generated across the crystal when stressed. This property is also the basis for such familiar sensors as crystal phonograph cartridges and crystal microphones. For accelerometers, the principle is shown in Figure 5. Here, a piezoelectric crystal is spring-loaded with a test mass in contact with the crystal. When exposed to an acceleration, the test mass stresses the crystal by a force (F = ma), resulting in a voltage generated across the crystal. A measure of this voltage is then a measure of the acceleration. The crystal per se is a very high-impedance source, and thus requires a high-input impedance, low-noise detector. Output levels are typically in the mill volt range. The natural frequency of these devices may exceed 5 kHz, so that they can be used for vibration and shock measurements.

Fig.5 Piezoelecric Accelerometer

IV. MODEL UPDATING OF INDIVITUAL COMPONENT

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

[image:4.612.71.269.92.251.2]

205 Fig.6 Test set up for free hammer test on LVDT accelerometer

[image:4.612.331.522.356.500.2]

Modal testing with the free–free boundary condition was conducted on each specimen from both sets of components. Fig. 6 shows the experimental set-up for the flat plates and the top-hats. The flat plates were tested using one hammer point and measurement points (Fig. 7 (a)), while the top hat were tested using one hammer point and five measurement points (Fig. 7 (b)) as follows

Fig 7.Test set-up for (a) the flat plate and (b) the top-hat

With only the first five modes measured from both sets of tests. The locations of the impact and measurement points were carefully chosen such that they are not located near any nodal points. Furthermore, the mass of each accelerometer was only 1.6 g, while the mass of the flat plate and the top-hat was 0.7 and 1.1 kg, respectively. Hence, the effect of mass loading was very minimal. So we going to apply the load from 0.7 to 1.1 kg and see the results in ANSYS 12.0.Theorotically we take the maximum load 1.1 kg i.e. 21.582 N force and arbitrary height 100 mm and see the results of frequency in five mode as below. And compare with the initial load of 0.7 kg i.e. 13.734 N at same point. The horizontal nodal point for hammering test is taken as 225.6 mm. At 0.7 kg the frequency of flat plate for 5 modes 24.28, 42.46, 95.13, 149.55 and 154.07 respectively in Hz. For top hat 25.01, 45.56, 97.77, 155.98 and 161.89 in Hz respectively.

When we take the maximum load as 1.1 kg the first five mode frequency of flat plate and top hat are 24.20, 47.10, 98.07, 152.24, 159.54 and 25.04, 48.01, 99.87, 154.45, 160.76 in Hz respectively.

V. ABOUT SOLID 285

Here, we are going to analyze the BIW part by using ANSYS AUTODYNE 12.0. For analysis the BIW part i.e. top hat SOLID 285 element (Tetrahedral 4 node) is used for FE modeling. The reason as below-

1. Convergence of solution is better in tetrahedral element compare other element.

2. If we select the tetrahedral with more than 4 node i.e.8 nodes, 10 nodes, etc. So, it will take more time for analysis because number of nodal point is increases. 3. SOLID 285 is the nomenclature for 4 nodes quadrilateral

element according to NAFEMS (National Agencies For Finite Element Method And Standards, London). 4. Less number of nodes are taken to reduce computational

time (Reduce number of equation and number of boundaries. The element description as follows

Fig 8 SOLID 285 Geometry

[image:4.612.52.285.359.503.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

206

In geometry nodal location and co-ordinate system for this element are shown in fig 8.In addition to the node the input data includes the orthotropic or anisotropic material properties, material properties and anisotropic material direction correspond to the element co-ordinate direction. Element are describe in node and element load. Pressure load may be input as a element faces as shown in fig.8 Hence, the effect of mass loading was very minimal. So we going to apply the load from 0.7 to 1.1 kg and see the results in ANSYS 12.0.Theorotically we take the maximum load 1.1 kg i.e. 21.582 N force and arbitrary height 100 mm and see the results of frequency in five mode as below. And compare with the initial load of 0.7 kg i.e. 13.734 N at same point. The horizontal nodal point for hammering test is taken as 225.6 mm and result(i.e. frequency at first five mode ) for complete BIW part for 0.7 kg and 1.1 kg are

[A]30.23,52.27,95.74,157.24,164.18

[B]32.24,53.69,100.39,160.45,167.18 in Hz respectively.

VI. FEMODELING USING ANSYS 12.0

[image:5.612.322.569.218.405.2]

Here we used SOLID 285 element i.e.(Tet 4 node 285). The total number of mesh division is 25 i.e. each division of 22.56 mm distance .Total number of node taken in this type of element is 5965. Now, we are going to model i.e. top hate of BIW parts by using ANSYS software. The impact load is varies from 0.7 kg to 1.1 kg. But, in analysis this load acting like a static load so it varies from 1.5-2 times impact load. So, we assume according to impact theory of a load taken this load as 2 times impact load as 1.4 kg to 2.2 kg i.e. from 13.734 N to 21.582 N. Meshing of top hate is shown in fig 9

Fig 9 Meshing of top hat structure

After FE modeling and analysis of static load from 0.7 kg to 1.1 kg we calculated the maximum and minimum stress, maximum nodal displacement and frequencies for first five modes. Table I gives the comparison of this value at different static load as follow.

Table I

maximum stress, minimum stress and maximum nodal displacement for different static load

Sr. No.

Static load in

kg

Maximum stress in

N/mm2

Minimum stress in

N/mm2

Maximum nodal displacement

in mm

1 0.7 0.12844 0.07058 0.626x10-4

2 0.8 0.14679 0.0806 0.80488x10-4

3 0.9 0.16514 0.09746 0.80488x10-4

4 1.0 0.18349 0.10083 0.89431x10-4

5 1.1 0.20184 0.11091 0.98374x10-4

[image:5.612.337.550.481.610.2]

Figure 10 gives the nodal solution for stress after applying maximum static load i.e.1.1 kg, also figure 11 gives the nodal solution for nodal displacement after applying maximum static load i.e.1.1 kg. And figure 12 gives first five mode shapes for applying maximum static load i.e. 1.1 kg as follows-

[image:5.612.49.289.492.680.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

[image:6.612.328.554.113.379.2]

207 Fig 11 Nodal solution for displacement at 1.1 kg static load

Mode 1

Mode 2

Mode 3

Mode 4

Mode 5

Fig 12 First five mode shape of top hat for 1.1 kg static load

VII. RESULT AFTER FEMODELING

After FE modeling we know that failure of model is by means of the loading..

0 0.2 0.4 0.6 0.8 1 1.2

13.734 15.696 17.658 19.62 21.582

Max Dispacement x 10-4 mm

[image:6.612.70.269.121.246.2]

(Static load)

[image:6.612.331.560.460.586.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

208

0 0.05 0.1 0.15 0.2 0.25

13.734 15.596 17.658 19.62 21.582

Maximum stress in N/mm2

[image:7.612.56.287.176.479.2]

(Static load)

Fig 14 Maximum stress verses static load

0 0.02 0.04 0.06 0.08 0.1 0.12

13.73 15.7 17.66 19.62 21.58

Minimumum stress in N/mm2

(Static load)

Fig 15 Minimum stress verses static load

Impact loading because the laser spot weld is failure under action of heat treatment only. In case of BIW part the heat generation at the junction is negligible i.e. BIW part fail under the action of loading (vibration only.) Figure 13 gives variation of maximum nodal displacement at different static load. Figure 14 gives variation of maximum stress at different static load. Also figure 15 gives variation of minimum stress at different static load.

VIII. CONCLUSION

This work has reviewed some of the FE models developed to represent spot welds normally produced by RSW in the past. Amongst all these models, SOLID 285 is selected to modeling and different static load analysis and mode generation at that respective static load.

Initially, the capability of the element to represent the laser spot welds is uncertain and its potential in producing reasonably accurate values of natural frequencies is questionable. Most importantly, it is essential to have an appropriate mesh in the FE model since it will influence the size of the patch used in the FE model. In this work and the conclusion from modeling using ANSYS as above and after briefly studying the paper for thermal stress analysis of laser spot weld is an analytical and finite element analyses have been investigated to simulate the laser spot welding process on a mild steel sheet. We concludes some result from the analysis is as follows

1 The maximum displacement is 0.98374x10-4 mm at a

static load of 21.582 N i.e. at a 1.1 kg weight of accelerometer in free hammer test for complete structure.

2 The minimum displacement is 0.62602x10-4 mm at a static load of 13.734 N i.e. at a 0.7 kg weight of accelerometer in free hammer test for complete structure.

3 The graph between static loading verses maximum displacement is a little bit straight line i.e. the loading not produces the linear curve regarding displacement. That‟s indicates that displacement not varies with static loading (shown in fig 12)

4 The maximum stress is 0.20184 N/mm2 at a static load of 21.582 N i.e. at a 1.1 kg weight of accelerometer in free hammer test for complete structure.

5 The minimum stress is 0.12844 N/mm2 a static load of 13.734 N i.e. at a 0.7 kg weight of accelerometer in free hammer test for complete structure.

6 The graph between static loading verses minimum as well as maximum stress is a straight line i.e. the loading produces the linear curve regarding stress. That‟s indicates that stress varies with static loading (shown in fig 13 and 14 for maximum and minimum stress developed respectively)

7 Here the nodal position for maximum displacement, maximum stress and minimum stress is 3896, 3541 and 2387 respectively are constant for each static loading i.e. from 13.734 N- 21.582 N. Because we applying the static load at 225.6 mm.

8 For FE modeling we used SOLID 285 element (Tetra

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International Journal of Emerging Technology and Advanced Engineering

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9 The frequency generation at each mode at each loading is same with same nodal position .Also the frequency at first five modes is approximately equal to the calculated experimental value at accelerometer. 10Theoretical frequencies are in closer approximation

with experimental frequencies and hence theoretical values are validated. Also, induced stresses are within the limit of Permissible stress by which former are being found by using ANSYS software.

REFERENCES

[1 ] N A Husain,H H Khodaparast, A Snaylam, S James,G Dearden, and H Ouyang Department of Engineering, University of Liverpool, Liverpool, UK The manuscript was received on 16 June 2009 and was accepted after revision for publication on 2 October 2009. [2 ] Waldo J. Perez Regalado Dr. Roman Gr. Maev and Dr. Andrey

Chertov “Real-Time Ultrasonic Evaluation of the Aluminum Resistance Spot Welding Process”

[3 ] Mosoud Sanayei,Eric Santini Bell,Chitra N.Javdekar,Jennnifer L.Edelmann and Euges slavsky “Damage location and finite element model updating multiresponse NDT data”

[4 ] D.C. Kim, H.J. Park ,I.S. Hwang andM.J. Kang Advanced Welding and Joining R&D Department, Korea Institute of Industrial Technology, 7-47 Songdo-Dong, Incheon, Korea “ Resistance spot welding of aluminum alloy sheet 5J32 using SCR type and inverter type power supplies”

[5 ] Rohit Rai ,Rituraj Nandan and Chandan Kumar “Finite Element Analysis of Pulsed Laser Spot Welding”

[6 ] Ali. Moarrefzadeh” Study of Heat Affected Zone (HAZ) in Resistance Welding Process”

[7 ] Samuel R. Wilton” Tennis Racquet Finite Element Analysis” [8 ] Cho, Y., Hu, S. J., and Li,W. Resistance spot welding of aluminum

and steel: a comparative experimental study.J. Eng.Manuf., 2003, 217, 1355–1363.

[9 ] Oldfield, M., Ouyang, H., and Mottershead, J. E. Simplified models of bolted joints under harmonic loading. Comput. Struct., 2005, 84, 25–33.

[10 ]Ibrahim, R. A. and Pettit, C. L. Uncertainties and dynamic problems of bolted joints and other fasteners.J. SoundVibr., 2005, 279, 857– 936.

[11 ]Kim, J.,Yoon, J.-C., and Kang, B.-S. Finite element analysis and modelling of structure with bolted joints. Appl.Math.Modell., 2007, 31, 895–911.

[12 ]Osamah F. Abdulateef, Department of Manufacture Operation Engineering / AL-Khwarizmi College of Eng. / University of Baghdad

[13 ]Gladwell, G. M. L. and Ahmadian, H. Generic element matrices suitable for finite element model updating. Mech. Syst. Signal Process., 1995, 9(6), 601–614.

[14 ]Prof. P. C.Vasani”criteria for selection of FE models”

Figure

Fig. 2 Part model of top hate diemension in PRO-E
Fig 7.Test set-up for (a) the flat plate and (b) the top-hat
Fig 9 Meshing of top hat structure
Fig 11 Nodal solution for displacement at 1.1 kg static load
+2

References

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