Design and Analysis of Truck Chassis Using Finite Element Analysis (FEA)
Research work describes analysis of ladder chassis frame for TATA 2518TC chassis. Practically load distribution on the chassis is not the uniform across it’s the total area, so according to the intensity of the load it is the possible to vary the area of ladder chassis system. The Analysing the effect of reduction in the cross section area with constrains of the bending stress, shear stress and deflection, reduction in the area will be save amount of material required for ladder chassis system. Four different cases are the considered and in each case height is the reduced for some specific span of chassis system where intensity of the load is less. The reduction of area for some specific span will be distribute nearly uniform stresses across it’s the whole area. The research work is the carried out on side member of ladder chassis particularly.
The Automotive chassis is the skeletal frame on which various types of mechanical parts like engine, tires, axle assemblies, brakes, steering etc. are bolted. The chassis is to be considered to be the most significant component of and the automobile. It is the most crucial element that can be gives strength and stability to the vehicle under the different vehicle conditions.
The automobile frames provide the strength and flexibility to the automobile. The backbone of the any automobile system, it is the supporting frame which is the body of the engine, axle assemblies are the affixed. Automotive frames are basically manufactured from the steel. It is provides strength needed for the supporting vehicular components and payload placed upon it. It is the usually made of a steel frame, which holds the body and motor of the automotive vehicle. At the time of manufacturing, the body of a vehicle is flexibly melded according to the structure of the chassis.
The chassis frame plays a vital role in the automobiles system. All most all the components weight is acting on the chassis frame in the vehicles, thus chassis subjected to the static, dynamic and the cyclic loading condition on the road, therefore chassis must be the rigid enough to resist this loads. The static stress analysis is the important to be point out critical highest stress regions in the chassis frame. These critical regions may cause the fatigue failures. In this study, ladder type of chassis frame is the analysed. The Chassis frame consists of the side members attached with the series of cross members to be complete the ladder like structure, thus it’s the name.
They were the designed for functionality and provided the little torsional stiffness. The FEA is the common tool for the stress analysis. FEA with required the boundary conditions was the used to be the determine critical regions in the vehicles chassis frame. Static structural analysis is the performed to be identify critical regions and based on the results obtained design modification has to been done. The modal analysis of the vehicles chassis frame is carried out to be the determine the natural frequency of the the mode shapes of the system. The rigidity of the system was the analysed and their resonance could be the avoided.
The magnitude of the stresses can be the used to be predict the life span of the chassis frame. The location of the critical stress point is the important so that the mounting of the components like engine, suspension, transmission and more can be the determined and optimized, Finite Element Method (FEM) is the one of the most useful method to locate the critical point. Safety factor are the used to be provide the design margin over the theoretical the design capacity. This the allows consolidation of the uncertainties in the design process. Jadav Chetan Steal reviews various factors affecting the fatigue life of a structure like cyclic stress state, geometry, surface quality, material type, residual stresses, size and the distribution of internal defects, direction of loading and grain sizes.
Finite Element Analysis
There are the three main steps namely as the: pre-processing, solution and the post processing. In the pre-processing model definition is includes: define the geometric domain of the problem, the element type to be the used, the material properties of an the elements, the geometric properties of an the elements length, area, and the like, the element connectivity mesh the model, the physical constraints of the boundary conditions and the loadings. In the solution phase, the governing algebraic equations in matrix form are the assembled and the unknown values of the primary field variable are the computed. The computed results are then used by the back substitution to be determine additional, derived variables, such as the reaction forces, element stresses and the heat flow. Actually, the features in this step such as the matrix manipulation, numerical integration and equation solving are the carried out automatically by the commercial software. In the post processing, the analysis and evaluation of the result is the conducted in the step.
Principal Functions of Chassis
The providing mounting points for the suspensions, the steering mechanism, the engine and gearbox, the final drive, the fuel tank and the seating for the occupants. Protect the occupants against an external impact, To safety carry out the maximum load, Holding the all components together while the driving, Accommodate twisting on even the road surface, Endure the shock loading, It is the must be absorb engine and driveline torque.
From the literature survey it is the observed that strength is the prime important point for the vehicle chassis frame design if possible with reduced weight. The load acting on the chassis frame it is not uniform across it’s the total area. Due to the non-uniform loading on the chassis generated stresses are not the uniform across its total area. But where the intensity of the load is is less unnecessarily extra material is the provided.
Layout of Chassis
The chassis is an important part of automobile. The chassis serves as the frame for supporting the body and different units of automobile vehicles like engine, suspension, gearbox, braking system, steering, propeller shaft, differential, axle assemblies, etc. are welded or bolted as shown in figure.
Types of chassis
1. Ladder Frame chassis
The ladder chassis is the considered to be one of the oldest forms of automotive chassis or automobile chassis that is still been used by most of the SUVs till today. It is also resembles a shape of a ladder which having two longitudinal rails inter linked by several lateral and cross braces as shown in figure.
2. Backbone chassis
The other type of the chassis is backbone chassis which has to be rectangular tube like backbone and the simple in structure. It is the usually made up of glass fibre that is the used for joining front and rear axle together and responsible for most of the mechanical strength of the framework. The space within the structure is used for positioning the drive shaft in case area-wheel drive. This type of the chassis is strong enough to be provide support smaller sports car besides it is easy to make and cost effective.
3. Monologue Chassis
As for the monologue chassis frame, most of modern cars now a days use this type of the chassis. The monologue chassis frame is a single piece of the framework that gives shape to the car. The one-piece chassis frame is built by welding several pieces together. It is the different from the ladder and backbone chassis frame as unlike them incorporated with the body in a single piece, whereas the former only the support the stress members. The demanding of the monologue chassis highly increased since it is the cost effective and suitable for the robotized production.
4. Tubular space frame chassis
In this study, it is the decided that tubular space frame chassis is the used for the urban car. Since ladder chassis is not the strong enough, motor racing engineers have developed a 3-dimensional design which known as the tubular space frame. The tubular space frame chassis employs dozens of the circular-section tubes (some may use the square section tubes for the easier connection to the body panels though circular section provides the maximum strength of frame), position in different directions to be provide mechanical strength against the forces from the anywhere. These tubes are the welded together and form the complex structure.
The objective of the research work is design the ladder chassis frame according to the application of the load on it. It is the observed that some area of the chassis frame comes under heavy load and the remaining part of it is under low load. The generation of the stresses will be according to the applied load on the chassis frame i.e. in some area of the chassis frame magnitude of stresses will be high and remaining portion of chassis frame will be the under low stresses. Consider the conditions.
- Design the chassis frame by considering its existence dimensions. It will give the magnitude of stresses and deflection which is generating in the chassis frame.
- Reduce the area where the intensity of stress is less.
- Generated the stresses and deflection after reducing area must be the less than its allowable limit.
- Calculate amount of the weight reduction after the reducing area.
DESIGN CALCULATIONS FOR CHASSIS FRAME
The Material and Geometry of TATA (Model No. 1613) Truck
Side bar of the chassis frame are made from “C” Channels with 280mm x 90 mm x 6 mm
Material of the chassis frame is ASTM A710 Steel material
Front Over hang (a) = 935.00 mm
Rear Overhang (c) = 1620.00mm
Wheel Base (b) = 3800.00 mm
Modulus of the Elasticity, E = 2.10 x 105 N / mm2
Poisson Ratio = 0.28
Capacity of the Truck = 8 tons = 8000kg = 78480 N
Capacity of the Truck with 1.25% = 98100 N
Weight of the body and engine frame = 2 ton = 2000 kg
Total load acting on the chassis frame = Capacity of the Chassis frame + Weight of body and engine = 98100 N+ 19620 N= 117720 N
Chassis has two beams. The load acting on each beam is half of the Total load acting on the chassis frame.
Load acting single chassis frame in the vehicles = 117720/2 = 58860 N / Beam.
In the future scope, to be the work is done on the effect of dynamic load like a vibration and the loading due to external factors such as the air resistance, suspension effect, cornering, brake dip etc. By considering the all and some above loads, the analysis of the chassis can be made to be meet actual life of the situation. Impact analysis of the chassis frame can be the carried out. Using polymeric composite materials for heavy duty vehicle chassis frame reduced the weight approximately 70 %~85% having the same load carrying capacity and also 65~80% stiffer than the steel chassis frame.
Stresses analysis using the finite element analysis (FEA) was the successfully carried out to be determine the high stresses of the value, maximum deflection and it’s the location on a low loader chassis frame structure. Corresponding the technical drawing and the information of the low loader chassis frame obtained was utilized to be develop the finite element model. The results of the analysis revealed that the location maximum deflection and maximum stress agrees well with the theoretical maximum location of the simple beam under the uniform loading distribution. The design of the safety factor for low loader structure is the established to be at 3.5 based on the analysis.
This study found out that there is discrepancy between the theoretical (2-D) and the numerical (3-D FEA) results. Therefore further analysis will be the performed to be improve the current FE model. Apart from that, future study will be include experimental investigation to be determine actual deflection of the similar beam.
From the result of the analysis it is found that weight can be the reduce by making of the pockets on side and the cross members and it also found that the if we make pockets on the cross member weight reduction is more as compare to side member also strength of pockets on cross will be give high strength
By using the composite material we can be reduce weight but strength of chassis frame reduces.