lR;eso t;rs jsy Hkou] ubZ fnYyh & 110001 MEMBER ELECTRICAL ...

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jsy Hkou] ubZ fnYyh & 110001MEMBER ELECTRICAL, RAILWAY BOARD

&EX-OFFICIO SECRETARY,GOVERNMENT OF INDIAMINISTRY OF RAILWAYS

RAIL BHAVAN, NEW DELHI - 110001

Foreword

WAG9H class of locomotives have been designed to cater to requirement of

higher Tractive Effort for hauling freight trains. The increased tractive effort leads to

increase in loading of various components involved with transmission of tractive effort.

These components e.g. pivot posts, traction motor suspension, TM mounting lugs

are located in underframe and are therefore critical not only from the point of view of

reliability but also from safety point of view.

Failures of these components have led to doubts about the adequacy of design of

these sub-assemblies in view of increased tractive effort. Though individual

components have been analysed and certain design modifications have been

undertaken, a need for analysis of system as a whole was felt.

I am happy to note that RDSO has taken up this task and carried out detailed

Finite Element Analysis for complete sub-system and summarized the results

component-wise in the report.

I hope that this will provide crucial data base to help Zonal Railways and

Production Units.

(Ashwani Kumar Kapoor)Member TractionRailway Board

Acknowledgement

The FEA analysis has been carried out with the help of Engineering and

Industrial Services group of Tata Consultancy Services, who ran the FEA simulation on

Abacus.

We also thank Shri Vipin Kumar and his team at CLW for providing the latest

drawing in CAD for modeling the components.

Thanks are also due to Shri Manish K. Gupta and Shri Ganesh for providing

insight into loading assumptions and boundary conditions.

Table of Contents

S. No. Page

1. Introduction 1

2. Tractive Effort Transmission System 1

3. Modeling 3

4. Loading 3

5. Analysis 4

5.1 TM Mounting Plate 5

5.2 Torque Arm 6

5.3 Bogie Pivot Assembly 8

5.4 Elastic Ring Housing (Bogie) 9

5.5 Push Pull Rod 11

5.6 Elastic Ring Housing (Body) 15

5.7 Body Pivot Post 17

5.8 Pivot Pin Bogie & Body 18

6 Summary and Conclusion 21

1

1. Introduction:

WAG9 classes of freight locomotives were procured from M/s Bombardier

Transportation with transfer of technology enabling CLW to manufacture these

locomotives indigenously. These locomotives have Co-Co bogie with axle-hung

nose-suspended traction motors type 6FRA6068. The weight of the locomotives

is borne by a two-stage suspension comprising of dampers and helical springs.

The tractive effort is transferred using axle guides from axles to bogie and push-

pull rod from bogie to body. These are provided with spheriblocs in case of axle

guides and elastic ring in case of Push-Pull Rod to take care of shocks.

The tractive effort of the WAG9 locomotive was increased by modification

to software and increasing axle load, resulting in WAG9H. Failures of mechanical

components like Motor Support, TM mounting plate, Brake Hangers have been

observed and certain changes in design have been made to address these

issues. Further, cracks in bogie pivot and Body Pivot welding were reported and

though these were found be due to deficiency in welding, it is considered

important to revalidate the design of the transmission system using FEM, taking

into account the modifications that have been done till date.

2. Tractive Effort Transmission System:-

The tractive effort is transferred from the bogie to body through push-pull

rod which consists of flange on both sides welded with a hollow tube in middle.

The flange is connected to elastic ring housing on both sides which contains

elastic ring to absorb shocks. The center of the elastic ring is mounted on the

pivot pin which is welded onto the pivot assembly. The pivot assembly is welded

on to the bogie transom at the bogie-end and to the central underframe of the

body of the locomotive.

The components of the tractive effort transmission sub-system for

which the study has been undertaken are:-

TM Mounting Plate

TM Spheriblocs

Torque Arm

Motor Pivot Support

Elastic Ring Housing

Elastic Ring

Push-pull Rod

Body Pivot

2

Torque Arm

Spheriblocs

TM Mounting

Plate

Bogie Frame

Tractive Effort

Fig 1 : Representation of Loads & Boundary conditions

Vertical force due to TM weight and torque reaction

Push-pull Rod Aclathan

Ring Housing

Aclathan Ring

Body Pivot

Fixed in all DOF except translation in

loading direction

3

3. Modeling:

The CAD drawings incorporating the modifications were used to create a

3D-model of the components in the transmission system. Meshing of the

components has been done in Hypermesh pre-processor mainly using 8-noded

Hexa elements and 1st order tetra elements. The components are connected

together by node to node matching mesh. Linear Elastic material model has been

used for all components. As the system is symmetrical in the vertical plane with

respect to components as well as material, half-symmetrical analysis has been

carried out with symmetric boundary conditions at the cut-section region i.e.

plane of symmetry, to arrive at the results. All interactions have been assumed

as tied.

In order to model Spheriblocs, rubber radial stiffness has been taken as

50000N/mm2 and 3D FE model has been used to iteratively converge to Young’s

Modulus of 6.29 MPa. For Elastic Ring, the radial stiffness of the material is

taken as 15789.47N/mm2 and 3D FE model is used to iteratively converge to a

Young’s Modulus of 9.642MPa. 3D Stress analysis has been conducted in

Abaqus Standard in SI-mm system.

4. Loading :

The load has been arrived at by considering the maximum tractive effort

generated by the bogie at the wheel rim. The force has been applied to the body

pivot. The force has been translated to arrive at the reaction force on the torque

arm assuming frictionless bearings for TM, Axle boxes and MSUs. This along

with the weight of traction motor has been considered to arrive at the vertical load

on the torque arm.

The simulation has been carried out for combinations of loads ie. Torque

reaction upwards and downwards and tractive effort in pushing and pulling

direction resulting in following four scenarios of loading:-

a) Case 1 : Torque Reaction downward and Tractive Effort pulling

b) Case 2 : Torque Reaction upward and Tractive Effort pulling

c) Case 3 : Torque Reaction downward and Tractive Effort pushing

d) Case 4 : Torque Reaction upward and Tractive Effort pushing

4

Motor Weight, W 2150kg 21091.5N

Half Motor Weight W/2 10545.75N

Distance of Torque Arm from TM center r1 513.194mm

Distance of TM center from Rail level R 546.00mm

Tractive Force Ftr 270kN

Tractive Force per motor Ftr/3 90kN

Torque Eqv. Force F 95.789kN

Torque Eqv. Half Symmetrical Force F/2 47.8945kN

Half Symm. Motor Weight W/4 5272.875N

Total Force F/2+W/4 53.157kN

5. Analysis:

Based on the loading and the material characteristics, Von Mises stress has

been computed and factor of safety evaluated for various components through

which the tractive effort gets transmitted. The Von-Mises stress reflects the

equivalent linear stress for the Cauchy Stress Tensor for a volume in cases of

multi-axial loading conditions in terms of distortion energy.

The Ultimate Tensile Stress value for evaluation of the factor of safety has

been taken as the lowest acceptable value in the material specification.

Torque Reaction

+ Weight/2

Figure 2: Loading

Assumptions

5

5.1. TM Mounting Plate :

The TM mounting plate is used to support the motor on the bogie and along

with the MSU shares the weight of the traction motor. However, it also takes the

torque reaction from the gear drive to the motor. This reaction force depends on

whether the traction motor is powering or braking as well as the direction of rotation

of the traction motor.

The Von-Mises stress plot for TM Mounting plate for various load cases are

plotted in Fig. 3a and 3b. From the plots it can be seen that the maximum value of

stress is at the inside fillet radius portion of the TM support plate as expected. The

maximum Von Mises stress observed in Load cases 1, 2, 3 and 4 are 276.09MPa,

220.78MPa, 275.86MPa and 220.77MPa respectively. The Ultimate Tensile Strength

of the material (Cast Steel GS20Mn5 to DIN 17182) is 500MPa resulting in a factor

of safety of 1.81 for load cases 1 & 3 and 2.26 for load case 2 & 4.

Max Von Mises Stress= 276.09 MPa

UTS = 500 MPa

Factor of Safety = 1.81

Max Von Mises Stress=220.78 MPa

UTS =500 MPa


LOAD CASE 1 LOAD CASE 2

Fig 3 : TM Mounting Plate : Von Mises Stress (MPa)

6

5.2. Torque Arm :

The torque arm is used to connect TM Mounting Plate to Bogie through

spheriblocs at both the ends It transfers the resultant force of torque reaction

and motor weight to the Motor Support on the bogie. The load carried by

torque arm is predominantly in vertical direction.

The Von-Mises stress plot for Torque Arm for various load cases are

plotted in Fig. 4. From the plots it can be seen that the maximum value of

stress is at the sides at the neck portion as expected. The maximum Von

Mises stress observed in Load cases 1, 2, 3 and 4 are 35.66 MPa,

26.50MPa, 35.63MPa and 26.52MPa respectively. The Ultimate Tensile

Strength of the material (AS: 3678 Grade 350 L15) is 450MPa resulting in a

factor of safety of 12.62 for load case 1, 16.98 for load case 2, 12.63 for load

case 3 and 16.97 for load case 4.

Fig 3b: TM Mounting Plate : Von Mises Stress (MPa)

12

Max Von Mises Stress=275.86 MPa UTS = 500 MPa Factor of Safety = 1.81



7

Max Von Mises Stress= 35.66 MPa Yield Stress = 450 MPa Factor of Safety = 12.62

Max Von Mises Stress= 26.50 MPa Yield Stress =450 MPa Factor of Safety = 16.98

Max Von Mises Stress=35.63 MPa Yield Stress =450 MPa Factor of Safety = 12.63




Max Von Mises Stress=26.52 MPa Yield Stress = 450 MPa Factor of Safety = 16.97

Fig 4 : Torque Arm: Von Mises Stress (MPa)

8

5.3. Bogie Pivot Assembly :

The bogie pivot is welded on to the bogie transom and is the element

transferring the tractive effort to and from Bogie to Body. The tractive effort

generates longitudinal force at the lowest point of Bogie Pivot i.e. pivot pin,

introducing shear force on the assembly. The assembly also comprises of

motor support and so resultant of torque reaction and share of motor weight

also acts in vertical direction.

The Von-Mises stress plot for Bogie Pivot Assembly for various load

cases are plotted in Fig. 5a and 5b. It is observed that the maximum stress

point is at the fillet radius for the motor support. The maximum Von Mises

stress observed in Load cases 1, 2, 3 and 4 are 144.16 MPa, 136.64MPa,

140.76MPa and 140.00MPa respectively. The Ultimate Tensile Strength of

the material (IS:2062 Grade 410C) is 540MPa resulting in a factor of safety

of 3.75 for load case 1, 3.95 for load case 2, 3.84 for load case 3 and 3.86 for

load case 4.

Fig 5a : Bogie Pivot : Von Mises Stress (MPa)



Max Von Mises Stress=136.64 MPa UTS =540 MPa Factor of Safety = 3.95

9

5.4. Elastic Ring Housing (Bogie-end) :

The elastic ring housing houses the elastic ring which is mounted onto the bogie

pivot pin to cushion the shock/jerks in tractive effort. It is connected to Push-pull

Rod Flange by means of bolts. The tractive effort is transferred though the housing.

The Von-Mises stress plot for Elastic Ring Housing (Bogie-end) for various load

cases are plotted in Fig. 6. From the plots it can be seen that the maximum value of

stress is at the sides at the neck portion as expected. The maximum Von Mises

stress observed in Load cases 1, 2, 3 and 4 are 311.38 MPa, 306.95MPa,

236.06MPa and 236.26MPa respectively. As expected this is not dependent on the

direction of traction motor and only on the direction of tractive effort i.e. bogie pulling

vs bogie pushing. The Ultimate Tensile Strength of the material (Cast Steel

GS20Mn5: DIN 17182) is 500MPa resulting in a factor of safety of 1.61 for load case

1, 1.63 for load case 2, 2.12 for load cases 3 and 4.


Fig 5b: TM Mounting Plate : Von Mises Stress (MPa)



10

Fig 6: Elastic Ring Housing (Bogie-End) : Von Mises Stress (MPa)

LOAD CASE 1

LOAD CASE 2

LOAD CASE 3

LOAD CASE 4



Max Von Mises Stress= 236.06 MPa UTS =500 MPa Factor of Safety = 2.12


11

5.5. Push Pull Rod :

Push-Pull Rod or Traction link is the connection between body to bogie

consisting of a hollow forged steel tube welded to cast steel flanges and both ends

which are in turn bolted to elastic ring housings. This is primary equipment

transferring tractive effort.

The model has considered flanges and tubes separately. The Von-Mises stress

plot for Push-pull Rod Flange (Bogie-end) for various load cases are plotted in Fig.

7(i)a and 7(i)b. The maximum Von Mises stress observed in Load cases 1, 2, 3 and

4 are 273.49 MPa, 270.71MPa, 261.89MPa and 262.02MPa respectively. As

expected this is not dependent on the direction of traction motor and only on the

direction of tractive effort i.e. bogie pulling vs bogie pushing. The Ultimate Tensile

Strength of the material (Cast Steel GS20Mn5: DIN 17182) is 500MPa resulting in a

factor of safety of 1.83 for load case 1, 1.85 for load case 2, 1.91 for load case 3 and

4.



UTS = 500 MPa



UTS =500 MPa


Fig7(i) a : Push-pull Rod Flange (Bogie-end) : Von Mises Stress (MPa)

12

The Von-Mises stress plot for Push-pull Rod Tube for various load cases are

plotted in Fig. 7(ii). The maximum Von Mises stress observed in Load cases 1,

2, 3 and 4 are 136.92 MPa, 135.38 MPa, 133.84 MPa and 117.46 MPa

respectively. The peak stress is near the welding joints with flange. The Ultimate

Tensile Strength of the material (DIN 2448 St37) is 350MPa resulting in a factor

of safety of 2.56 for load case 1, 2.59 for load case 2, 2.62 for load case 3 and

2.98 for load case 4.


UTS =500 MPa



UTS = 500 MPa



Fig7(i) b : Push-pull Rod Flange (Bogie-end) : Von Mises Stress (MPa)

13

LOAD CASE 1

LOAD CASE 2

LOAD CASE 3

LOAD CASE 4


UTS = 350 MPa



UTS =350 MPa



UTS =350 MPa



UTS = 350 MPa


Fig 7(ii): Push-pull Rod Tube : Von Mises Stress (MPa)

14

The Von-Mises stress plot for Push-pull Rod Flange (Body-end) for various load

cases are plotted in Fig. 7(iii)a and 7(iii)b. The maximum Von Mises stress observed

in Load cases 1, 2, 3 and 4 are 257.47 MPa, 254.42MPa, 248.31MPa and

249.03MPa respectively. As expected this is not dependent on the direction of

traction motor and only on the direction of tractive effort i.e. bogie pulling vs bogie

pushing. The Ultimate Tensile Strength of the material (Cast Steel GS20Mn5: DIN

17182) is 500MPa resulting in a factor of safety of 1.94 for load case 1, 1.97 for load

case 2, 2.01 for load case 3 and 2.00 for load case 4.



UTS = 500 MPa



UTS =500 MPa


Fig7(iii) a : Push-pull Rod Flange (Body-end) : Von Mises Stress (MPa)

15

5.6. Elastic Ring Housing (Body-end) :

The elastic ring housing houses the elastic ring which is mounted onto the

body pivot pin to cushion the shock/jerks in tractive effort. It is connected to Push-

pull Rod Flange by means of bolts. The tractive effort is transferred though the

housing.

The Von-Mises stress plot for Elastic Ring Housing (Body-end) for various

load cases are plotted in Fig. 8. From the plots it can be seen that the maximum

value of stress is at the sides at the neck portion as can be expected. The maximum

Von Mises stress observed in Load cases 1, 2, 3 and 4 are 324.05 MPa,

320.20MPa, 246.03MPa and 246.67MPa respectively. As expected this is not

dependent on the direction of traction motor and only on the direction of tractive

effort i.e. bogie pulling vs bogie pushing. The Ultimate Tensile Strength of the

material (Cast Steel GS20Mn5: DIN 17182) is 500MPa resulting in a factor of safety

of 1.54 for load case 1, 1.56 for load case 2, 2.03 for load cases 3 & 4.



UTS =500 MPa



UTS = 500 MPa


Fig7(iii) b : Push-pull Rod Flange (Bogie-end) : Von Mises Stress (MPa)

16

LOAD CASE 1

LOAD CASE 2

LOAD CASE 3

LOAD CASE 4


UTS = 500 MPa


Max Von Mises Stress= 320.20 MPa

UTS =500 MPa



UTS =500 MPa



UTS = 500 MPa


Fig 8: Elastic Ring Housing (Body-End) : Von Mises Stress (MPa)

17

5.7. Body Pivot Post

The body pivot post is welded on to the Central Under-Frame of the

Body and transfers the tractive effort to and from Body. The tractive effort

generates longitudinal force at the lowest point of Bogie Pivot through pivot

pin, introducing shear force on the assembly.

The Von-Mises stress plot for Body Pivot Post for various load cases

are plotted in Fig. 5a and 5b. It is observed that the maximum stress point is

at the welding between bottom plate and vertical plates. The maximum Von

Mises stress observed in Load cases 1, 2, 3 and 4 are 134.24 MPa, 134.12

MPa, 128.83 MPa and 128.94 MPa respectively. The Ultimate Tensile

Strength of the material (IS2062 grade Gr 410C) is 540MPa resulting in a

factor of safety of 4.02 for load case 1, 4.03 for load case 2, 4.20 for load



Fig 9a : Body Pivot Post : Von Mises Stress (MPa)



18

5.8. Pivot Pin:

The pivot pins are provided on both body and bogie pivots to provide elastic

ring. The elastic ring is mounted with the pivot pin inside and elastic ring housing

outside.

The Von-Mises stress plot for Bogie and Body Pivot Pin for various load

cases are plotted in Fig. 10a and 10b respectively.. From the plots it can be seen

that the maximum value of stress is at the sides at the neck portion as expected.

The maximum Von Mises stress for Bogie Pivot Pin observed in Load

cases 1, 2, 3 and 4 are 119.05 MPa, 117.23MPa, 113.49MPa and 114.24MPa

respectively. As expected this is not dependent on the direction of traction motor

and only on the direction of tractive effort i.e. bogie pulling vs bogie pushing. The

Ultimate Tensile Strength of the material (Cast Steel GS20Mn5: DIN 17182) is

500MPa resulting in a factor of safety of 4.20 for load case 1, 4.27 for load case 2,

4.41 for load case 3 and 4.38 for load case 4.



Fig 9a : Body Pivot Post : Von Mises Stress (MPa)


19

Fig 9a : Bogie Pivot Pin : Von Mises Stress (MPa)


UTS = 500 MPa



UTS =500 MPa



UTS =500 MPa



UTS = 500 MPa




20



Fig 9b : Body Pivot Pin : Von Mises Stress (MPa)


UTS = 500 MPa



UTS =500 MPa



UTS =500 MPa



UTS = 500 MPa


21

The maximum Von Mises stress for Bogie Pivot Pin observed in Load

cases 1, 2, 3 and 4 are 120.41 MPa, 120.41 MPa, 119.98 MPa and 120.12MPa

respectively. As expected this is not dependent on the direction of traction motor

and only on the direction of tractive effort i.e. bogie pulling vs bogie pushing. The

Ultimate Tensile Strength of the material (Cast Steel GS20Mn5: DIN 17182) is

500MPa resulting in a factor of safety of 4.15 for load cases 1 & 2, 4.17 for load


6. Summary and Conclusion :

The results from the analysis are summarized as under:-

Component Max. Von Mises Stress (in MPa)

Factor of Safety

TM Mounting Plate 276.09 1.81

Torque Arm 35.66 12.62

Bogie Pivot Assembly 144.16 3.75

Elastic Ring Housing (Bogie) 311.38 1.61

Push Pull Rod Flange 273.49 1.83

Push Pull Rod Tube 136.92 2.56

Push Pull Rod (Body-end) 257.47 1.94

Elastic Ring Housing (Body) 324.05 1.54

Body Pivot Post 134.24 4.02

Pivot Pin Bogie 119.05 4.20

Pivot Pin Body 120.41 4.15

From the results it is seen that the Von-Mises Stress is well below Ultimate

Tensile Strength of material used in the manufacturing of components. The

maximum stressed component is Elastic Ring Housing with Von-Mises Stress of

324.05 MPa which is well below 500 MPa which is the UTS for its material. The

factor of safety at this level of stress is 1.54.

The results thus validate the present design of mechanical sub-system

relating to tractive effort with modified motor support, push-pull rod and TM Mounting

Plates to cater to the increased starting TE generated by the WAG9H class of

locomotives.

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