24-09-2014, 02:13 PM
ABSTRACT Engineering components with optimum use of material and easy manufacturability is a direction where prior simulation through finite element method is found to be very useful. Front Axle of Tractor is one of the major and very important component and needs very good design as this part experiences the worst load condition of the whole tractor. The objective of this paper was to analyse the new design of the front axle of tractor for Thirteen (13) different Certification Test load conditions. The existing design has no field failure reports; so the results of the existing design were taken as basis for comparison with results of the proposed models. Based on the finite element analysis results, redesign was carried out for the front axle for weight optimisation and easy manufacturability. This led to five proposed designs of the front axle which were evolved based on the above objectives. The proposed designs were evaluated for selected worst load cases of the existing design. The finite element analysis of new models yielded displacements and stresses close to the existing d
PROJECT REPORT
1.1 To Modify And Analyze The Design of Tractor’s Front Axle
1.2 ABSTRACT:
Engineering components with optimum use of material and easy manufacturability is a direction where prior simulation through finite element method is found to be very useful. Front Axle of Tractor is one of the major and very important component and needs very good design as this part experiences the worst load condition of the whole tractor. The objective of this paper was to analyse the new design of the front axle of tractor for Thirteen (13) different Certification Test load conditions. The existing design has no field failure reports; so the results of the existing design were taken as basis for comparison with results of the proposed models. Based on the finite element analysis results, redesign was carried out for the front axle for weight optimisation and easy manufacturability. This led to five proposed designs of the front axle which were evolved based on the above objectives. The proposed designs were evaluated for selected worst load cases of the existing design. The finite element analysis of new models yielded displacements and stresses close to the existing design. The increase in stresses was close to 15 % for all five models. The increase in displacement was not significant but all the new designs conceived had met the structural requirement. It was also observed that for the proposed designs there was a significant reduction in weight (approximately 40 %) and the proposed models did not involve a lot of welding, thereby significant savings of manufacturing was observed. The components used in the assembly were also found to be cost effective like smaller diameters bearing, smaller knuckle size etc. The reduction in cost of production and weight significantly reduced the cost of the new design of Front Axle. This analysis work showcases the use of finite element analysis as a method for reduction of cost in terms of materials and manufacturing.
1.3 INTRODUCTION:
Front Axle of Tractor is one of the major and very important component and needs very good design as this part experiences the worst load condition of the whole tractor. The objective of this work was to analyze the current design of the tractor front axle and evaluate the proposed designs for reduction in weight and for better manufacturability.
The current design was analyzed for 13 different Certification Test load cases. Five different models were proposed based on ease of manufacture and weight reduction. The welding and forming operations required in the proposed models were less than the current model. Also some of the connected components like bearings, bushes etc. have been redesigned for improved performance and decrease in cost. These were done based on field feedback.
1.4 CASES:
The Certification load cases as defined for the project is specified below:
1.4.1 DROP TEST:
In this case a pit of 2.5 feet deep and 2 feet wide and 5 feet long is dug on a very hard ground. The tractor comes on to it at maximum speed of 35 Kmph and one of the front wheels is allowed to fall into it. The tractor engine pushes the tractor further till the end of the pit and the engine keeps on humming in this case even after tractor has reached the end of the pit for some time and finally the engine stops. This is for tractors with 35/55 HP capacity.
1.4.2 TORTURE TEST:
The tractor is run on a test track which is having various types of humps/road conditions.
The conditions are described below:
Wheel 1
Condition
Wheel 2
Condition
OK
Pot Hole
Ok
Pot Hole
OK
Pot Hole
Ok
Hump
OK
On a small radius
Ok
On a big radius Hump
(i.e. the radius of hump vary across the width of road )
OK
On a Plane Road
Ok
On a Slope
(Like agriculture plot boundary)
Ok
On a V road with Humps
Ok
On a V road with Humps
(The road height is less at the centre and on an inverted V road with humps)
1.4.3 ‘8’ SHAPED TRACK TEST:
The Tractor runs at 35 Kmph speed on a ‘8’ shaped track with three medium sized humps positioned at 120o to each other in each circle of ‘8’. The Steering has to be turned till its locking position is reached while negotiating a curve.
1.4.4 THE IMPACT TEST:
One side of the tractor collides head on against a rigid wall at a speed of 35 Kmph.
1.4.5 EXTENDER WIDE OPEN TEST:
The front axle extenders are fully extended and the tractor runs on either type of the V road at a speed of 15 Kmph and also on one side slope condition.
1.4.6 PIT TEST:
At speed of 30 Kmph the tractor goes inside a pit of 10 feet deep with 20 degree slope on either side and comes out.
1.4.7 WORST LOAD TEST:
In this load case all the worst load conditions, except the impact load would be applied on the axle and the analysis would be carried out. Also an extender wide open test with worst load case would be carried out.
1.5 PROCEDURE:
9. 10 Solid Model of Current design
The geometric model for the current configuration was created based on the drawings provided. Small fillets and blends were ignored while creating the model. The geometric model was made using Unigraphics V16.0 (Fig-9.10).
The proposed models were based on the sketches, drawings and discussions with the manufacturing engineers. Five proposed models were created (See Figure 9.11).
9. 11 Solid Model of Proposed design
The geometric models created in Unigraphics were imported into ANSYS V5.6 and FE meshing was carried out with appropriate type of finite elements.
The current model was meshed using SOLID 45 and SOLID 92 Tetrahedral elements available in ANSYS. The inner box, outer box and the torch portions were meshed using the SOLID45 elements and the knuckle; pin, hub, bearings and bushes were meshed using the SOLID92 elements. The
9. 12 Finite Element Model of Current Design
bearings, knuckle, hubs and the bushes were restrained by coupling nodes (See Figure 9.12).
The proposed model was meshed using shell elements and solid tetrahedral elements. The boxes were meshed using the SHELL63 elements. SHELL63 was considered for the analysis as it saved a lot of time and effort for meshing of the proposed models with varying thickness. The knuckle, pin,
9. 13 Finite Element Model of Proposed Design
hub, bearings, torch and bushes were meshed using SOLID92 elements (See Figure 9.13).
Major components of the Front axle where FE meshing have been carried out were,
• Outer box
• Inner box with torch
• Hub
• Knuckle and pin
• Bushes and bearings.
The details of the loads applied on the model were calculated and given in the appendix-A. A typical load and boundary condition is given in Figure 9.14
9. 14 FE Model of Current Design with Boundary Conditions
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The individual components have been coupled together so that there is no free motion between components. The bearings and bushes have been coupled to the pin and the knuckle on the inner side and on the outer side they have been coupled with the sleeve / hub. The extender is coupled with the outer box at the end of the extender and at the bolts. In the proposed model the torch is coupled to the extender. The vertical restraints are applied on the bolts of the hub. The axial and transverse restraints are applied at the pin in case of the current model and on the sleeve in the proposed model.
The loads as applied on the current and proposed model are given in Table – 1
Table 1: Directional loads applied for different Certification Test Conditions
Sr No.
Load Case
Applied Loads
(N)
FX
FY
FZ
1.
Drop Test
(One Wheel in Pit)
0
12000
7548
2.
Torture Test
(Both Wheels in Pit)
0
24000
20120