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Jeppiaar Engineering College Jeppiaar Nagar, Rajiv Gandhi Salai, Chennai – 600119
Tamilnadu, INDIA.
Preliminary
Design
Report
Baja SAE-Asia 2010
Report submitted by:
Srikrishna.A.S
Akshay Arvind
Michael Tyson. I
Dinesh Kumar. N
Jeppiaar Engineering College Chennai -600119, Tamilnadu, INDIA
BAJA SAE-ASIA 2010, Design Report (Preliminary)
Copyright © 2009 SAE International
ABSTRACT
The aim of the initiative was to have a hands-on experience about the applications of computer in the field of designing with regards to the Mini Baja 2010. The task at hand was to design an All Terrain Vehicle taking into consideration all the basic loads and forces that may act on the same. The report deals with the basic approach followed for the roll cage design and then the analysis followed for the same. The configuration and modeling of the vehicle is also later discussed.
INTRODUCTION
According to the common objective of BAJA SAE-Asia 2010, TEAM MAVERIX, the SAE collegiate club team from Jeppiaar Engineering College had to initially formulate a virtual design of an All Terrain Vehicle aimed at the weekend off-road enthusiast at a reasonable price point and also factor in the manufacturability and marketing aspects.
The team used cutting-edge design and analysis software effectively to convert their mental ideas and designs to virtual reality on computers. The usage of computers aided us in checking the feasibility and safety of the designs.
The team consisted of 15 members who had basic knowledge in the field of designing and 3D CAD software like Pro/E, SolidWorks, and ANSYS etc. The team was committed to perform and envisioned the top prize as their goal. This commitment helped the team perform on an integrated scale thus ensuring a constant and laudable progress. The members complimented each other with healthy knowledge and experience transfer which helped in enthusiastic atmosphere maintenances.
Spurred by the coveted prize of “Champions of Baja SAE-Asia 2010” and the pride of working under the auspices of SAE-India, TEAM MAVERIX set out to test their prowess and prove their worth.
CHALLENGE AHEAD
The vision of the Design Event was to formulate an ATV that can be manufactured on a scale of 4000 vehicles per year. This was kept in mind at every step of the design. The designers sought to design a vehicle that possesses high static and dynamic stability, considerable ease of manufacture and economic viability too
The first step taken in this regard was to formulate a process flow chart that would be followed. This action plan proved to be a standard based on which the progress of the team was evaluated. Since no external technical assistance was available for the team, such intricate techniques helped the team progress well. At the same time, no compromise was made on the component quality and customer satisfaction keeping in mind the competition standards.
CHASSIS
The chassis forms an integral part of any vehicle. Since every other component of the vehicle is mounted and supported on the chassis, its design and fabrication required a lot of care and consideration. The team set out with a series of goals before starting the design of the chassis. Some of the common considerations for the chassis were:
Safety of the driver
Stability of mounting of the vehicle components.
Driver ergonomics.
Roll over prevention and
Aerodynamic stability
Other aspects like speed and ease of manufacture etc.
All these factors were taken into consideration at every single step undertaken in the design process of the roll cage.
A roll cage frame was adopted as per the rules laid down by the Baja SAEINDIA Rule Book. The roll cage
SRIKRISHNA.A.S AKSHAY ARVIND MICHAEL TYSON.I DINESH KUMAR.N [email protected]
provides a minimal three-dimensional space surrounding the driver and hence very safe for the same. The team endeavored to test their innovation by designing a roll cage that stuck to the rules and also proved to be innovative.
DESIGN AND ANALYSIS:
The team had to adhere to the rules and also provide an innovative design thus having a competitive edge. The flow in the design is as follows:
Rough sketching ( Pencil and Paper ).
2-D drafting and dimensioning.
Solid modelling using 3D CAD software.
Wireframe design.
Material assignment.
Reading model attribute values.
Finite element analysis. The details of the same are given below.
ROUGH SKETCHING:
For any designer, the preliminary ideas are always pencil and paper ones. A brainstorming session was convened for all designers to present their design ideas and the core design team zeroed in on the final draft. All subsequent design actions were based on the finalized draft.
2D DESIGN (Detailed Drawing and Dimensioning):
The 2-D detailed drawing of the Roll cage was generated using AutoCAD 2007. The standard views viz. plan, elevation and side views were generated and all the dimensions were clearly indicated in conformance with the ISO standards. The dimensioning showed that the Roll Cage met the specifications laid down by SAE-India. The 2-D design served as a template on which the next phase of the project, 3D solid modeling, was executed. However, the 2-D design was open to modifications to accommodate certain features in the 3D model which were incorporated with manufacturability in mind.
Figure 1 – Front View
Figure 2 – Top View
Figure 3 – Side View
DIMENSIONING
All the dimensioning was done as per ISO standards and the choice of dimension of cross-section was 1” I.D steel tube with 3mm wall thickness and 1-1/4” O.D.
SOLID MODELLING
The integral part of the challenge was the solid modeling of the roll cage. A sequential procedure was followed as that in real time production. Pro/E modeling software along with SolidWorks was adopted for the purpose. These software packages formed a potent combination in bringing out the final design efficiently and as visualized by the designers.
Figure 5 – Rendered isometric View
Figure 6 – Rendered Top view
Figure 7 – Rendered Front View
The final views of the model have been displayed by the above figures.
WIREFRAME DESIGN FOR FEA:
The Finite Element Analysis process required a sound wireframe design on which the appropriate type of elements could be assigned and used for further structural analysis by the application of meshing and loading techniques available in ANSYS software.
Thus, based on the points’ coordinates obtained from the solid model in Pro/E and SolidWorks, the wireframe was painstakingly generated from scratch in the ANSYS modeling interface. All keypoints were defined and connected with lines and meshed using BEAM 3 element type.
Figure 4 – Wireframe model in ANSYS
MATERIAL ASSIGNMENT
The material for the RCM was taken as AISI 1020. This belongs to the Carbon steel category. This was preferred due to the following properties:
Density 7.8 ×1000 kg/m3
Elastic Modulus 210 GPa
Poisson's Ratio 0.32
Carbon (% w/w) 0.18-0.23
Tensile strength 395 M Pa
Yield strength 295 M Pa
The values taken are as per the standards set forth by SAE-INDIA for Mini Baja.
PARAMETRIC CALCULATIONS
Once the material properties of the model were assigned, the next step was to obtain the various design parameters of the vehicle. This was achieved using facilities available with the design software.
Some of the parameters calculated are tabulated:
Material AISI 1020
Mass 111836.49 grams
Volume 14156517.52 mm3
Surface Area 5795139.15 mm2
Center Of Mass
X = 272.96 mm
Y = 510.96 mm
Z = 9.56 mm
FINITE ELEMENT ANALYSIS
Analysis of the RC was performed on two platforms:
1. COSMOS (Solid Works)
2. ANSYS V11.0
FINITE ELEMENT ANALYSIS
(IN ANSYS V10.0/11.0)
The roll cage was modeled in the ANSYS v10.0/11.0 interface using the coordinates obtained from the SolidWorks and Pro/E models. The various cases of vehicular deformation were categorized into:
1. Frontal Collision
2. Side Impact Collision
3. One-wheel (left) impact collision
Frontal Collision
In this case, the FBM Nose and LFS Nose were constrained of all their DOF. The load of 1000N was applied on four vital points of the RRH and the model was found to be sufficiently strong and the stress and deflection values were well within permissible limits and thus rendering the design safe for implementation.
Figure 12 Frontal Collision (DMX = 0.206 mm)
Figure 13 – Von Mises Stress (SEQV) SMX=13.379.
Figure 14 – Nodal Solution (UX) SMX=0.069.
Side Impact Collision
For this case it was assumed that the vehicle underwent a collision on one of its side. The right side SIM and LFS were arrested completely and a powerful load of 2500N was applied on the other side. A preventive LDB was provided in the LFS to ensure driver’s safety. Further analysis of additional required members will be performed once the other components are designed.
Figure 15 – Side Collision (DMX = 7.263 mm)
Figure 16 – Von Mises Stress (SEQV) SMX = 106.5
Figure 17 – Nodal Solution (UZ) SMX = 6.835
One-Wheel sudden impact collision A quite possible real-world situation was visualized wherein it was assumed that the Baja undergoes an impact collision on one on its wheels. The inertial forces act on the other RCM’s. This was reproduced in ANSYS by completely arresting the frontal part of the left SIM and LFS where the suspension links would connect and a force of 2500 N was applied on four points of the RRH in the direction of motion.
Figure 18 – One wheel Impact (DMX = 2.205 mm)
Figure 19 – Von mises Stress (SEQV) SMX = 33.8
Figure 20 – Nodal solution (ROTY) SMX = .002
From these diverse and elaborate FEA efforts, it has been deduced that the Roll Cage design is structurally sound and can be manufactured to perform with a very high level of reliability and withstand the rigours of rough terrain maneuvering
CONCLUSION
The end of the analysis evokes positive results in the roll cage progress. So far we have optimized the design report with regard to the roll cage in accordance to SAEINDIA requirements. The design and analysis validation of the various components proves the design stability and better manufacturability of the vehicle.
CONTACT
LEGEND OF ACRONYMS
ATV – All terrain Vehicle.
FBM – Front Bracing Member
RCM – Roll Cage Members
RHO – Roll Hoop Overhead
OSM – Overhead Supporting Member
LFS – Lower Frame Side
DOF – Degrees Of Freedom
RRH – Rear Roll Hoop
LDB – Lateral Diagonal Bracing
SMX - Maximum Stress
DMX – Maximum Deflection
