Simulation of Roll Passes For Section Rolling Of Flat-Footed Rail Section with the help of FEA

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Simulation of Roll Passes For Section Rolling Of Flat-Footed Rail Section with the help of FEA

Sunil G. Janiyani 1, Prof. P. D. Solanki 2

1 P.G. Student, M.E. (CAD/CAM), 2 Professor. & Head,

Department of Mechanical Engineering, Department of Mechanical Engineering,

L. D. C. E., Ahmedabad 380015 L. D. C. E., Ahmedabad – 380015

Abstract – The rail sections are generally made of carbon steels by hot rolling process. The rolling of rail section is carried out in number of passes. For converting initial steel bloom into final rail section, the bloom is passed between numbers of rollers. Each rolle r has different grooves on it. The shape of groove decides the rolled section at each pass. So, to get desired section of each pass, we designed the sections which, in turn, reduce its cross-sectional area. The final finishing pass gives the standard rail section used in railways. Then the designed passes were simulated in Ansys workbench to determine induced stresses.

Keywords – hot rolling; steel; roll pass; rail section; FEM, Ansys workbench, Stress ;

  1. INTRODUCTION

    The process of plastically deforming metal by passing it between rolls is known as rolling. It is most widely used metalworking process because it tends itself to high production rate and close control of the final product. In deforming metal between rolls, the work is subjected to high compressive stresses from the squeezing action of the rolls and to surface shear stresses as a result of the friction between the rolls and the metal. The friction forces are also responsible for drawing the metal into the rolls.

    According to observation indicated by W. Zhang, C. Zhu and G. E. O. Widera, the rolling force and torque are the m ost important parameters influencing the determination of the energy for the rolling process [1]. Laila S. Bayoumi, concluded that Analysis of flow and stresses in isothermal steady- state round-oval-round pass sequence for the production of round bars has been obtained from a flowline field solution [2]. S.-H. Kim and Y. -T. Im investigated a knowledge-based expert system which was developed for the design of roll pass and profile sequences for the shape rolling of round and square bars [3]. Y. Lee, S. Choi and Y. H. Kim concluded that a reliable analytical model that determines the surface profile of a workpiece in round -oval-round pass sequence has been established [4]. Y. Lee and Y. H. Kim presented a semi-analytical method for the prediction of roll force in the oval-round pass rolling sequence [5]. A computer-aided-design (CA D) system to support roll pass design of bar rolling, where simple shapes like round and squares bars a re produced, was developed in order to minimize trial and errors in industry by H. C. Kwon and Y.

    T. Im [6]. Stanislaw Turczyn, Andrzej Nowakowski and Miroslaw Michalowski developed a safe and reliable roll pass design for producing ribbed bars [7]. E. N. Chumachenko, I. V. Logashina, and S.

    A. Aksenov proposed that the three -dimensional problem of rolling in passes be simplified by solving it approximately by the finite element method [8]. Karen Abrinia and Alireza Fazlirad proposed to study external shape and calculate pressure and torque for the process of rolling shaped sections [9]. F. Lambiase and A. Langella developed an automatic roll pass design method, capable of minimizing the number of roll passes [10]. For rail rolling by universal mill, a

    simplified three-dimensional theoretical model was built firstly by DONG Yang-gang, ZHANG Wen- zhi and SONG Iian-feng, [11].

    In the literature reviewed above, roll pass designs of different sections researches are carried out like round, diamond, square sections etc. Moreover, the numerical simulation by FEM has been used in universal rolling process. Then, the theory of universal rolling method has been developed and improved. Although the universal rolling method has been applied in rail rolling for 30 years, there are only few theoretical researches about the rail rolling by universal mills. Since the process of rail universal rolling is very complex and the exact solution of force-energy param eter is difficult to be obtained, there is large a scope to work with the rail section. So, present work is aimed at roll pass design of section rolling of rail section.

  2. STANDARD RAIL S ECTI ONS AND ITS SPECIFICATIONS

    Rails are the members of the track laid in parallel lines to provide an unchanging, continuous, and level surface for the movement of trains. To be able to withstand stresses, they are made of carbon steel. The details for chemical composition and mechanical properties are given in Table 2.1.

    Grade

    C

    Mn

    Si

    S (max.)

    P (max.)

    Al (max.)

    880

    0.6-0. 8

    0.8-1. 3

    1.3-0.5

    0.035

    0.035

    0.02

    Table 2. 1 Chemical composition of steel for rails [13]

    Rails are m ainly of three types so far used. These are double headed rail, bull headed rail and flat – footed rail. The first rails used were double headed and made of an I or dumb-bell section. The idea was that once the head wore out during service, the rail could be inverted and used. Experience, however, showed that while in service the bottom table of the rail was dented to such an extent because of long and continuous contact with the chairs that it was not possible to reuse it. The problem faced with double headed rail led to the development of the bull headed rail, which had an almost similar shape but with more metal in the head to better withstand wear and tear. This rail section had the m ajor drawback that chairs were required for fixing to the sleepers. A flat – footed rail is an inverted T-type section.

    The rail is designated by its weight per unit length. In FPS units, it is the weight in lbs per yard and in metric units it is in kg per metre. A 52 kg/m rail denotes it has a weight of 52 kg per metre [13].

    The standard rail sections in use in railways are 60 kg, 52kg, 90 R, 75 R, 60 R and 50 R. The two heavier rail sections, 60kg and 52kg, were recently introduced and are designated in metric units. Other rails are designated as per the revised Britis h Standard specifications and are designated in FPS units though their dim ensions and weight are in metric units. Mainly 60kg and 52kg are widely used in railways.

    Rail section

    Wt/m(kg)

    Dimensions(mm )

    A

    B

    C

    D

    E

    F

    52 kg

    51.89

    156

    136

    67

    15.5

    51

    29

    60 kg

    60.34

    172

    150

    74.3

    16.5

    51

    31.5

    Table 2.2 Det ails of standard rail sections [13]

    Figure 2.1 52-kg rail [13]

  3. ROLL P ASS DESIGN FOR S ECTION ROLLI NG OF FLAT-FOOTED RAIL SECTION

    The standard rail section is generally made from steel blooms by hot rol ling process. In rolling, the conversion of initial bloom to final section is achieved in num ber of passes. The number of passes generally depends on final section. The number of passes may be taken as 17 [14]. The initial bloom taken is having cross section of 90 mm x 285 mm and the final rail section is considered the 52 kg rail. F or maintaining smooth flow, the reduction in cross -sectional area is taken according to geometrical pro gression series. The designed exit sections at each roller pass are shown below.

    Figure 2.4 Section at pass 3

    Figure 2.5 Section at pass – 4

    Figure 3.1 Initial steel bloom Figure 3.2 Section at pass1 Figure 3.3 Section at pass2

    Figure 3.4 Section at pass3 Figure 3.5 Section at pass4 Figure 3.6 Section at pass5

    Figure 3.7 Section at pass6 Figure 3.8 Section at pass7 Figure 3.9 Section at pass-8

    Figure 3.10 S ection at pass-9 Figure 3.11 S ection at pass-10 Figure 3.12 S ection at pass-11

    Figure 3.13 S ection at pass12 Figure 3.14 Section at pass13 Figure 3.15 Section at pass 14

    Figure 3.16 S ection at pass-15 Figure 3. 17 Section at pass16 Figure 3.18 Section at pass17

  4. SIMULATION OF THE ROLL P ASS ES

    All the passes shown above then simulated in Ansys workbench t o determine the induced stresses during the rolling of the material. The set up of rolls and stands for the rolling stands is shown in below figure.

    Figure 4.1 Rolling stand sample and its components

    Coefficient of friction for the simulation is taken as 0.5. Other material properties us ed for the simulation are shown below.

    Roll stock material

    Rolling and stands material

    Material

    Structural Steel

    Titanium Alloy

    Density (kg/m3)

    7850

    4620

    Specific Heat (J/kg. C)

    434

    522

    Isotropic Elasticity

    Youngs Modulus (GPa)

    200

    96

    Poissons ratio

    0.3

    0.36

    Bulk modulus (GPa)

    166.67

    114.29

    Shear modulus (GP a)

    76.923

    35.294

    Bilinear Isotropic Hardening

    Yield strengt h (GPa)

    0.25

    0.93

    Tangent modulus (GPa)

    1.45

    2.15

    Table 4. 1 Material properties used for simulation

  5. RES ULTS AND DISCUSSIONS

    The simulat ed passes gave the stress values for eac h pass. The following table shows the results and ot her parameters considered during each roll passes.

    Pass No.

    Cross- sectional

    area (mm2)

    %

    reduction in area

    Temp. of Material (°C)

    Speed of rolls (rpm )

    Velocity of material (m/s)

    Angle of bite, (°)

    Stress (MPa)

    1

    94575

    14.91

    1150

    60

    1.0

    22.78

    1384.1

    2

    79950

    15.46

    1128

    60

    1.0

    22.19

    1187.2

    3

    68250

    14.63

    1107

    60

    1.0

    21.79

    1162.1

    4

    58500

    14.29

    1086

    60

    1.0

    19.63

    1162.8

    5

    48750

    16.66

    1066

    30

    1.2

    19.30

    1133.9

    6

    42000

    13.84

    1046

    30

    1.2

    30.78

    1183.0

    7

    35700

    15.00

    1027

    30

    1.2

    24.78

    1099.7

    8

    30100

    15.69

    1008

    30

    1.2

    24.15

    0935.4

    9

    25900

    13.95

    989

    30

    1.2

    21.92

    0801.2

    10

    21420

    17.28

    970

    30

    1.2

    19.75

    1062.9

    11

    18060

    15.68

    952

    30

    1.2

    18.50

    1073.5

    12

    15036

    16.74

    934

    30

    1.2

    19.79

    1775.6

    13

    12360

    17.80

    917

    10

    0.6

    23.81

    1810.2

    14

    10200

    17.47

    900

    10

    0.6

    27.55

    2457.5

    15

    8321.3

    18.41

    883

    10

    0.6

    29.08

    1926.2

    16

    7053.5

    15.23

    867

    10

    0.6

    29.08

    1407.9

    17

    6628.4

    06.02

    850

    10

    0.6

    29.08

    0807.9

    Table 5. 1 Results of simulation of each passes

    Figure 5.1 and 5. 2 show the graphs plotted for pass no. v/s % reduction in area and stress v/s angle of bite respectively.

    Figure 5.1 Pass No. v/s % reductions in area Figure 5.2 Stress v/s Angle of bite

    From the above results & graphs, we may conclude as below:

    The % reduction in cross-sectional area in each pass is nearly uniform. To get fine finishing at the end, the reduction in final pass is low compare to previous passes.

    The stress induced in each pass varies according to the % reduction in area. It means the stress reduces as the % reduction in area reduces and vice versa, in most of the passes.

    The stress induced in each pass varies according to the angle of bite also. It means the stress reduces as the angle of bite reduces and vice versa, in most of the passes.

    From the above conclusions and results, we can say that the stress induced in each pass is above the materials flow stress and below the materials breaking stress.

    The abrupt reduction in cross-sectional area results in higher stress values during pass no. 12 to 16.

    REFERENCES

    1. W. Zhang, C. Zhu and G. E. O. Widera, ON THE USE OF THE UPPER BOUND METHOD FOR LOA D DE TE RMINA TION IN H-BEAM ROLLING. Journal of m aterials processing technology 56(1996) 820-833

    2. Laila S. Bayoumi, FLOW AND S TRESSES IN ROUND -OVAL-ROUND ROLL PASS SEQUENCE. Int. J. Mech. Sci. Vol. 40, No. 12, pp. 1223-1234,1998

    3. S.-H. Kim, Y. -T. Im, A KNOWLEDGE-BASED EXPERT SYSTEM FOR ROLL PASS AND PROFILE DESIGN FOR SHAPE ROLLING OF ROUND AND SQUARE BARS. Journal of Materials Processing 89-90 (1999) 145-151

    4. Y. Lee, S. Choi, Y. H. Kim, MATHEMATICA L MODEL AND E XPE RIME NTAL VALIDA TION OF SURFACE PROFILE OF A WORKPIE CE IN ROUND -OVAL-ROUND PASS SEQUENCE. Journal of m aterials processing technology 108 (2000) 87 -96

    5. Y. Lee, Y. H. Kim, APPROXIMA TE ANA LYSIS OF ROLL FORCE IN A ROUND-OVAL- ROUND PASS ROLLING SEQUE NCE. Journal of materials processing technology 113(2001) 124-130

    6. H. C. Kwon, Y. T. Im, INTE RACTIVE COMPUTE R-AIDED-DES IGN SYS TEM FOR ROLL PASS AND PROFILE DES IGN IN BAR ROLLING. Journal of materials processing technoogy 123(2002) 399-405

    7. Stanislaw Turczyn, Andrzej Nowakowski, Miroslaw Michalowski, ROLL PASS DESIGN FOR RIBBED BARS. Metal 2004

    8. E. N. Chumachenko, I. V. Logashina, and S. A. Aksenov, SIMULA TION MODELLING OF ROLLING IN PASSES. Metallurgist, Vol. 50, Nos. 7-8, 2006

    9. Karen Abrinia, Alireza Fazlirad, THREE DIMENTIONAL ANALYS IS OF SHAPE ROLLINGUSING A GENE RALLIZED UPPER BOUND APPROA CH. Journal of Materials Processing Technology 209 (2009) 3264-3277

    10. F. Lambiase and A. Langella, AUTOMA TED PROCE DURE FOR ROLL PASS DESIGN. ASM international, JMEPEG (2009) 18: 263 -272

    11. DONG Yang-gang, ZHA NG Wen-zhi, SONG Iian-feng, Theoretical and Experim ental Research on Rolling Force for Rail Hot Rolling by Universal Mill. Journal of iron and steel research, International. 2010, 17(1) : 27-32

    12. Dieter G. E., Mechanical metallurgy, Tata McGraw -Hill Book Company, 1988, pp. 586-593.

    13. Chandra S., Agarwal M.M., Railway engineering, Oxford university press, 2009, pp. 81-87.

    14. Roberts W. L., Hot rolling of steel, Marcel Dekker Inc., 1983, pp. 367 -376.

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