wheeler prototype vehicle chassis, to convert the three wheeler passenger vehicle chassis into a load carrier chassis with the aim of reducing the tooling cost and increasing the rate of production. For this, analysis of existing chassis has to be performed. The analysis is carried out by using Finite Element Analysis (FEA). The parameters checked in the analysis are the displacement of the chassis structure and stresses under static condition. The modeling of new chassis is done by using PRO-E and FEA by using ANSYS. Specifications of materials selection become a priority in order to construct the new chassis, based on the results of FEA, we selected CRS-D grade (Cold Rolled Steel) of thickness 1.6mm. The best design with minimum self weight, maximum load capacity and minimum deflection under static loading was then identified based on the results obtained through FEA.
Keywords: Passenger Vehicle, Load carrier, Von Moisses stresses, Chassis 1.INTRODUCTION
Chassis is a French term and was initially used to denote the frame parts or Basic Structure of the vehicle. It is the back bone of the vehicle. A vehicle without body is called Chassis. The components of the vehicle like Power plant, Transmission System, Axles, Wheels and Tyres, Suspension, Controlling Systems like Braking, Steering etc., and also electrical system parts are mounted on the Chassis frame. It is the main mounting for all the components including the body. So it is also called as Carrying Unit. The types of chassis are: backbone chassis, body on frame, space frame, and monocoque. Monocoque is a structural approach that supports loads through an object's external skin, similar to a ping pong ball or egg shell. The term is also used to indicate a form of vehicle construction in which the skin provides the main structural support, although this is rare and is usually confused with either semi-monocoque or a unibody. The word monocoque comes from the Greek for single (mono) and French for shell (coque).The technique may also be called structural skin or stressed skin. Alternatives to the monocoque structure are the truss structure, geodetic structure, unibody, inflatable, and semi-monocoque. The semi-monocoque is a hybrid of a mutually reinforcing tensile shell and compressive structure. A common aircraft has longerons (ribs or frames) and stringers. Most car bodies are not true monocoques; instead modern cars use unitary construction which is also known as unit body, unibody, or Body Frame Integral construction. This uses a system of box sections, bulkheads and tubes to provide most of the strength of the vehicle, to which the stressed skin adds relatively little strength or stiffness. In 1912 Deperdussin introduced a monocoque racer using a fuselage made up of three layers of laminated strips of glued poplar veneer, which provided both the external skin and the main load-bearing structure. This reduced drag so effectively it was able to win most of the races it was entered into. This style of construction was copied, with some variations, in Germany by Albatros and others; however it was prone to damage from moisture and delamination.
In this paper a new model monocoque chassis is proposed to intgrate both variety of three wheeler :Passenger vehicle and Load carrier. The rest of the paper is organized as follows. The brief literature review is given in section 2. The results of simulation of Ansys models Passenger vehicle and load carrier are given in Section 3 and 4 respectively.. Section 5 draws the results of modified chassis. Results and discussions are covered in Section 6. Section seven draws the conclusions
2. REVIEW OF LITERATURE
Fig.3.1: Parts of mpnocoque chassis
The static analysis of the passenger chassis have done by constraining the front and rear wheels at desired locations and applied loads at front and rear positions by considering all the parameters like driver, passengers engine, fuel tank, self weight of chassis. Automobile chassis usually refers to the lower body of the vehicle including the tires, engine, frame, driveline and suspension. Out of these, the frame provides necessary support to the vehicle components placed on it. Also the frame should be strong enough to withstand shock, twist, vibrations and other stresses. The chassis frame consists of side members attached with a series of cross members Stress analysis using Finite Element Method (FEM) can be used to locate the critical point which has the highest stress. This critical point is one of the factors that may cause the fatigue failure. The magnitude of the stress can be used to predict the life span of the truck chassis. The accuracy of prediction life of truck chassis is depending on the result of its stress analysis. The parameters taken for the static analysis are:
1. Side bar of the chassis are made from “C” Channels with 165mm x 70 mm x 1.6 mm 2. Wheel Base (b) = 1720 mm
3. Overall length of the vehicle = 2800mm 4. Material of the chassis is CRS D Grade 5. Young’s modulus, E= 205 GPa 6. Poisson’s ratio = 0.3
7. Radius of gyration = 165/2 = 82.5
8. Capacity of the vehicle (3+1)= 4×75=300kg = 2943N 9. Weight of the body and engine = 440kg = 4316.4N
10. Total load acting on the chassis in normal load condition = capacity of the vehicle +weight of the body=2943+4316.4 = 7259.4N
11. Total load of the vehicle with 1.5% over load = 8731N
12. Chassis has two beams. So load acting on each beam is half of the total load acting on the chassis. 13. Load acting on single beam = 8731/2=4365N.
Fig.3.2: FEA Model of Chassis
Under Normal working conditions, a load of 230kg applied at front part and at rear 550kg is applied and simulation studies made. The obtained contour plots of deflection and stresses developed in the chassis are shown in Fig.3.3 and Fig.3.4.
Fig-3.3.Deflection in passenger chassis in normal load condition
Fig-3.4.Von misses stresses in passenger chassis in normal load
Maximum deflection for the normal load condition is: 6.44mm and Maximum stress for the normal load condition is: 387N/mm2.
Fig-3.5: Deflection in passenger chassis in over load condition
Fig-3.6.Von misses stresses in passenger chassis in over load condition
Maximum deflection for the over load condition is: 9.659mm and Maximum stress for the over load condition is: 580N/mm2
4. STATIC ANALYSIS OF EXIST CHASSIS OF LOAD CARRIER
Carrier of vehicle is used to carry loads from one place to other place. This chassis is different from passenger chassis; here riser member is not necessary only single long member is used to build the chassis. The model is shown in Fig.4.1.The carrier chassis has the parts: Long member, Cross member, Horizontal tunnel and Vertical tunnel.
Fig-4.1. Different parts in load carrier chassis
The static analysis of the carrier chassis have done by constraining the front and rear wheels at desired locations and applied loads at front and rear positions by considering all the parameters like driver, engine, fuel tank, self weight of chassis. The following parameters are being considered in the analysis:
1. Side bar of the chassis are made from “C” Channels with 165mm x 70 mm x 1.6 mm 2. Wheel Base (b) = 1720 mm
the normal conditions found to be 9.151mm and Maximum stress for the normal condition is: 0.889N/mm
Fig-4.2.Deflection in load carrier chassis in normal load condition
Fig-4.3.Von misses stresses in load carrier chassis in normal load condition
Fig-4.5.Von misses stresses in load carrier chassis in over load condition
5. STATIC ANALYSIS OF MODIFIED CHASSIS The modification proposed in chassis is shown in Fig.5.1.
Fig.5.1: Modified Chassis
The parameters that are considered in the modified chassis are :
1 .Side bar of the chassis are made from “C” Channels with 165mm x 70 mm x 1.6 mm 2 .Wheel Base (b) = 1720 mm
3. Overall length of the vehicle = 2800mm 4. Material of the chassis is CRS D Grade 5. Young’s modulus, E= 205 GPa 6. Poisson’s ratio = 0.3
7. Radius of gyration = 165/2 = 82.5 8. Capacity of the vehicle = 555kg = 5445N. 9. Weight of the body and engine = 440kg= 4316.4N
10. Total load acting on the chassis under normal load condition= capacity of the vehicle +weight of the body=5445+4316.4 = 9761.4N
11.Total load on the vehicle with 1.5% over load = 12484N
12.Chassis has two beams. So load acting on each beam is half of the total load acting on the chassis.
13.Load acting on single beam = 12484/2 = 6242N.
Fig-5.2.Deflection in modified model chassis under normal load condition
Fig-5.3.Von misses stresses in concept model chassis in normal load condition
Maximum deflection for the normal conditions is: 4.882mm and Maximum stress for the normal condition is: 5.156 N/mm2
Over load condition (i.e., 50% extra load) for front part 345kg force is applied and at rear 1155kg have applied. The simulation results of deflection and stresses are shown in Fig.5.4 and Fig.5.5.respectvely.
Fig-5.5.Von misses stresses in concept model chassis in over load condition
Maximum deflection for the over load condition is: 7.322mm and Maximum stress for the over load condition is: 0.573 N/mm2
6. RESULTS AND DISCUSSION
6.1: Results obtained through ansys for passenger vehicle: Static analysis has been performed on passenger vehicle under both normal and overload conditions. The loading was calculated by assuming its capacity as (3+1) persons and also its GVW as 995kg. It was constrained at three wheels and the loading was uniformly distributed load.Under normal loading conditions the vehicle has undergone a static deflection of 6.44mm vertically downwards and the stresses developed were 20N/mm2. Whereas with 50% overloading conditions the deflection and stress were 9.659mm and 27N/mm2 respectively.Since the material selected was CRS-D Grade of strength 450N/mm2, we can say that the body can withstand these stresses. Hence the vehicle is said to be safe under these conditions.
6.2 Results obtained through ansys for load carrier vehicle: The main difference between passenger and carrier vehicle chassis design is the former one consists of one rising member and two long members where as in the later there is no any rising number and it contains only one rear member on each side. This chassis was also subjected to structural analysis under two conditions namely normal and 50% overloading. Its capacity eas assumed as 690kg and its GVW as 995kg.Under normal loading conditions the vehicle has undergone a static deflection of 9.151mm vertically downwards and the stresses developed were 52N/mm2. Whereas with 50% overloading conditions the deflection and stress were 10.949mm and 65.4N/mm2 respectively. Since the material selected for this chassis was also CRS-D Grade of strength 450N/mm2, we can say that the body can withstand these stresses. Hence the vehicle is said to be safe under these conditions.
7. CONCLUSIONS
The concept model (or) prototype chassis is successfully designed and analyzed. The design is done by PRO_E software, analysis is done by using ANSYS. The design is developed after the study of the existing chassis design and analysis is performed on both the chassis to compare the results. Basic load calculations have been performed by using the concepts strength of materials and these results have been compared with the results obtained through ANSYS. The FE results and theoretical results are in closed agreement, and the design stresses are within the limits of strength of material. Based on these results the passenger chassis is modified into the load carrier chassis which decreases the tooling cost and increases Productivity.
ACKNOWLEDGEMENTS
The author thanks H.O.D. Mechanical Engineering AND Executive Director, SreeNidhi Institute of Science and Technology: Hyderabad for their encouragement and help in bringing out this technical paper.
REFERENCES
[1] Chassis Design: Principles and Analysis - William F.Milliken
[2] Automotive chassis and body: construction, operation, and maintenance-William Harry Crouse
[3] The automobile chassis-Benjamin George Elliott
[4] 3-wheeler automobiles-wikipedia
[5] Furukawa. Y. and Abe, (1997),” Advance Chassis for Vehicles” Vehicle Dynamics,28,59-86
