jset: journal of science & engineering technology vol. 3

JSET: Journal of Science & Engineering Technology Vol. 3 Issue 2 (December) 2016 pp. 66 – 70

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Design and Analysis of Chassis for Go-Kart Using Finite Element

Ana Salwa Ramli1, Ahmad Yasir B Md Said2, Enzo Chalons3 1Mechanical and Manufacturing, University Kuala Lumpur Malaysia France Institute 2 Mechanical and Manufacturing, University Kuala Lumpur Malaysia France Institute

3 Université de Toulon, France

[email protected], 2nd [email protected], 3rd [email protected]

Abstract— This paper discuss on the study carried out using finite element method to analyze the strength of the chassis designed for Go-Kart. The software used in this study was CATIA. This Go-Kart will be participated in a national inter university competition. The stress concentrations at the bending and at the joint or welded part were analyzed. These are the weakest points of the chassis. Comprehensive analysis on this stress concentration needs to be carried out in order to avoid re-work after the chassis being fabricated. Results show that excessive bending on the chassis can produce high stress hence mitigates the fatigue strength. A proper handling when performing the welding process is very crucial in order to avoid part or component distortion and mechanical properties alteration. Any flaw on the chassis is very detrimental and can jeopardize the safety of the driver.

Keywords— Chassis Design, finite element method, stress analysis, bending and welding

I. INTRODUCTION Nowadays, the go-kart race has improved a lot in terms of

the criteria and requirement, which is, not only depends on the race itself but also included the analysis of parts used. With this, the race has brought to excellent results in developing innovative parts such as go-kart body structure. Most of the team used steel as a body structure. Steel commonly use in the application of mechanical structures which has an ability to absorb stress loads such as tension or compression loads.[1].

In order to reduce or avoid the re-work process for the structure, CATIA software is used to analyze the body structure before fabricate. With this, the modification can be made before the fabrication process and it can reduce cost and time consuming cause by repairing process.

Analysis by using CATIA software is to determine the weakness or critical point on the structure based on the result from the software used such as Generative Structure Analysis (GSA). According to the result produced by GSA, the improvement or restructure is made on the structure design. Besides that, the safety factors for the design can also be finalized by using this software. Therefore, the analysis needs to be done by using suitable software such as CATIA to ensure the durability of the structure before it can be fabricate.

II. FINITE ELEMENT METHOD IN BODY STRUCTURE Finite element analysis (FEA) is a computerized method

that was used for predicting on how a product reacts to real-world forces, heat, fluid flow, vibration and other physical effect. By using this software, it shows whether a product will be break, wear out, or work the way it was designed. The design modification was made according to the result given by the software and it can reduce the re-work process after the part is fabricated.

The finite element method (FEM) is useful in solving most of the engineering problems. Stress analysis, heat transfer, vibration, deflection and many other phenomena is considered a large class engineering problems. By using the finite element methods, those problems could be solved and it can be analyze either by using small or large scale.

To analyze a large structure, the simulation is required because of the astronomical number of calculation needed. Finite element analysis has an ability to deal with a complex structures [2],[3].

III. METHODOLOGY The studies are carried out by applying point load on the

chassis and were analyzed by using simulation. The simulation of the models are developed by using CATIA V5-6R2014 and analyzed by Generative Structural Analysis (G.S.A). The methodology of this study is shown in Fig. 1.

JSET: Journal of Science & Engineering Technology (Special Issue: August) No. 01 (2016) pp. 66 – 70

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Fig. 1 Methodology

A. Material Selection

The material used in this project was construction Steel S235. The mechanical and material properties used are base on mild steel which exhibited in Table 1. Those value was used during the analysis procedure by using Generative Structural Analysis (GSA).

TABLE 1 MATERIAL PROPERTIES OF THE CHASSIS

Material Type Mild Steel Young Modulus 210 GPa

Poisson’s Ratio, v 0.3 Density 7850 kg/m3 Yield strength 235 MPa Tensile Strength 340 MPa

Fig. 2 Section view of the material and dimension

The force applied for the specimens was analyzed using GSA. The yield strength of material S235 used in experiment procedure was 235MPa as in Table 1.

Fig. 3 Isometric view of chassis

Fig.4 Orthographic view of chassis

This chassis has been designed by using square hollow bar and round hollow bar. Total of bars used to build the chassis were 104 bars. Boolean operation was used to joint all bars to become one structure. For fabrication process, welded joint is used to weld all part of the structure.

IV. SIMULATION WORK

In this simulation work, using CATIA V5-6R2014 carries out finite element method. The works are divided into 2 sections, which are part design that consists of 2D and 3D design and Analysis and simulation by using Generative Structural Analysis (GSA).

A. Geometry Modelling by using Part Design

Part design is a tool used to design the go-kart body structure. The design process started with sketchers (2D) and continued with part modelling (3D) design.

This design consisted of 104 parts. Those parts need to be assembled to become one body structure. The permanent welded joint method is chosen to join the body structure. The chassis part was divided into 3 parts, which are front part, middle part and rear part. The front and the rear part of the chassis were chosen as a fixed component with coincidence constraint.

a. Front part b. Rear part


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c. Middle part

Fig. 5 Modelling Parts

To ensure the parts are really contacted to each other, the command contact and angle contact was used. The constraint is in green color. All parts need to be contact correctly to avoid a distortion between the parts.

B. Boolean Operation

A Boolean operation is similar to what is taught in Math; in fact this principle is borrowed from mathematical principle. It allows adding, subtracting geometries or simply finding the intersection between 2 or more geometry. Before the analysis could be done, it is compulsory to make all joints to become one single part. Boolean operation is used to regroup all 104 parts of the chassis.

Fig. 6 Boolean Operation

C. Part Design Analysis

After Boolean Operation is done, the next process is part design analysis. The parameter such as force which is applied to the chassis need to be considered. Those value was considered during the analysis procedure by using Generative Structural Analysis (GSA).

TABLE 2 THE PARAMETER

Component of GSA Value Weight of chassis

19.109 kg

Weight of pilot + seat 120 kg Weight of engine 30 kg Oil tank weight 12L (full of fuel)

9.6 kg

The weight of the pilot is 90 kg but due to safety reason, the weight used in GSA is 120 kg in order to have a security margin for the pilot.

D. Applied Force

The 2D view shows the value of the different component applied at the chassis. The manikin shows the contact point between the seat and the structure.

Fig. 7 Force applied to the chassis in 2D view

D. Generative Structural Analysis (GSA)

The clamping point is points, which attached to the absorber of the chassis was considered as a fix point during the analysis. There are 4 clamping points on this chassis. The forces were applied on the cylinder situated at the link between the chassis and the arm of the dumper or shock absorber.

Fig. 8 The Clamping Points

The parameters used for the generative structural analysis was as followed:

Material Type Mild Steel Young Modulus 210 GPa

Poisson’s Ratio, v 0.3 Density 7850 kg/m3 Yield strength 235 MPa Tensile Strength Gravity Mass of the structure Mesh Size Type of Mesh

340 MPa 9.81 19.67 kg 15 mm Octree Tetrahedron Mesh


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The different factor acting on the simulation is shown on Fig. 9. Even if four big red arrows on the extremities of the frame represent the gravity of the structure, the point of pressure is applied at the center of gravity of the structure. Those factors have been considered during analysis to calculate the constraint and the deformation of the structure.

Fig. 9 Structure before simulation G.S.A and forces apply

The first simulation result shows a structure without any important stress zone. Fig. 10 shows the Von Mises stress according to the force applied on the structure.

Fig. 10 Analysis Result for the first simulation

In order to get an accurate result, the meshing size needs to be reduced from 15mm to 2 mm. This action is to avoid the singularities, which can stop some calculation and delay the simulation process. By reducing the meshing size, CATIA software will calculate the result accurately.

Fig. 11 The difference meshing size

IV. RESULTS AND DISCUSSION The result from developed finite element model was taken

into account to improve the structure design. According to the simulation results, the critical zones need to be improved to ensure the increasing of the structure strength and safety factors during the endurance.

A. Simulation Results The adaptivity simulation consists of setting global

adaptivity specifications and computing adaptive solutions. The result gain after the adaptivity simulation was as followed:

Fig. 12 The result of adaptivity simulation

The result analyze by using GSA (Fig. 12) shows 4 critical zones (point 1, 2, 3 and 4), which are situated at the welded joint points. Those critical points are consisted of 3 to 4 bars at 1 joining point.

B. Critical Zones Analysis The 4 critical zones need a detail analysis in order to find a

suitable method of improvement for the structure.

a) Critical Zone 1 Analysis The critical zone 1 consists of 3 complex constraint points.

Two points are situated directly at the complex welded joining point and the software could not give a good meshing for this points. With this, those points are not going to be taken into account. The third constraint is situated a bit far from the welded joint point so it is considered as a risk zone and the modification need to be done to enhance the strengthen of the structure.

.

Fig. 13 Analysis of the critical zone 1

b) Critical Zone 2 Analysis The critical zone 2 consists of 2 importance constraint

points. The first point is situated directly on the bar cause by the pilot weight and the seat. According to the principle of Saint Venant, these points are not to be considered in the result.

Besides that, the second point is situated bit far from the welded joint and not in the complex geometry zone. This point is considered as risk zone and modification need to be done at this point.


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C. Structure Improvement According to the GSA result, the additional bars are added at the structure to reinforce the structure. These additional bars are positioned at the critical zone to reduce the stress at the areas and the GSA simulation need to be recalculated.

Fig. 15 Additional bars position

D. Result afterdesign improvement The improvement simulation design results proved that the

stress is dissipated. The compression stress which is concentrated on the welded area was dissipated after added the support bars.



The GSA result for the improvement design shows that the

additional bars able to reduce the stress at the critical zones. According to the results, Von Mises stress was decreased from 56 MPa to 35 Mpa for critical point 1 and for critical point 2, Von Mises stress was reduced from 53 Mpa to 29 Mpa. The amounts of additional bars added on the structure are 4 bars and total weights for the bars are 0.476 kg. With this, the total weights of the go kart structure are 19.109 kg.

V. RESULTS AND DISCUSSION The results obtained from the Solidwork analysis

proved that the additional bars have an ability to reinforce the structure. With this, the safety factor also increased accordingly. Finally, according to the analysis results, it can be conclude that, by increasing the mass of the structure to 2.49%, it can decrease the stress on the critical zones to 41.3%. By redesign the structure after obtained the analysis result could reduce the re-work process.

ACKNOWLEDGMENT The authors wish to thank Department of Mechanical and Manufacturing and Automotive Engineering Department University Kuala Lumpur-MFI for providing materials and facilities, and special thanks to Nur Azida Che Lah and Mohammad Hellmy Husain for their supports.

REFERENCES [1] C.N. Reid, K. Williams and R. Hermann, Fatique in compression.

Fatique Fracture, Engineering Material Structure 1, 1979: p.267-270. [2] O. B. Chan, A. E. Elwi, G. Y. Gilbert, Simulation of crack propagation

in steel plate with strain softtening model. Structural Engineering Report No. 266, May 2006.

[3] R. Hertzberg, Deformation and fracture mechanics of engineering materials. John Wiley and Sons, New York:1996

[4] Aidy Ali, Nur Azida Che Lah, Tan Soo Chin, Simulation of crack under compression loads, International Review of Mechanical Engineering (IREME), Vol.3, N.2, March 2009

[5] W. L. Lira, P. R. Cavalcanti, L. C. G. Coelho, L. F. Martha, A modelling methodology for finite element mesh generation of muti-region models with parameter surfaces. Computer and Graphics, 2002.6:p. 907-918.

[6] Dassault Systeme- Student Guide Book, 2003-2011

jset: journal of science & engineering technology vol. 3

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