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

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

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