Design and Analysis of Heavy Duty Vehicle (Trailer) Chassis through FEM Software Divyanshu Sharma 1, Y D Vora 2 1 M.E.Student, 2 Associate Professor, Department of Mechanical Engineering, L D College of Engineering, Ahmedabad, Gujarat, India. ABSTRACT Heavy duty vehicle plays a more important role in highway transportation. The major focus in the truck manufacturing industries is design of truck chassis with more pay load capacity and possible less weight. An important aspect of chassis design and analysis is the stress distribution and fatigue life of prediction process. Fatigue is one of the most important parameters to consider when designing truck components. The components are typically subjected to dynamic loads when in service. In this paper, an effort is made to alter the existing design of chassis by introducing hollow rectangular and T section. An analytical and numerical methodapproach is being adopted to calculate the weight reduction and stress at different points and also stress analysis has been done in ANSYS software to validate the result. Keywords: chassis design and analysis, Heavy Duty Vehicle (Trailer) Chassis, FEM Software I. Introduction Chassis is a Basic Structure of the vehicle. Chassis supports the components Power plant, Transmission System consisting of clutch gearbox, propeller shaft and rear axle, Wheels and Tyres, Suspension, Controlling Systems like Braking, Steering etc and electrical system parts are alsomounted on the Chassis frame. Automotive Chassis helps to keep an automobile rigid, stiff and unbending. Automobile chassis ensures less noise, vibrations and harshness throughout the automobile. The chassis frame consists of side members attached with a series of cross members. Along with the strength, an important consideration in the chassis design is to increase the stiffness (bending and torsion) characteristics. Adequate torsional stiffness is required to have good handling characteristics. Normally the chassis are designed on the basis of strength and stiffness. In the conventional design procedure the design is based on the strength and emphasis is then given to increase the stiffness of the chassis, with very little consideration to the weight of the chassis. One such design procedure involves the adding of structural cross member to the existing chassis to increase its torsional stiffness. As a result weight of the chassis increases. This increase in weight reduces the fuel efficiency and increases the cost due to extra material. The design of the Chassis with adequate stiffness and strength is necessary. The different types of automobile chassis are as follows: Conventional control chassis: In which engine is mounted in front of the driver`s cabin. This type of arrangement avoids full utilization of the space. Semi-forward control chassis:-in which engine is mounted that half of it is in the driver`s cabin whereas the other half is in front, outside the driver`s cabin. Full-forward control chassis:-in which engine is mounted completely insides the driver`s cabin. Obviously maximum utilization of space is achieved in this type of arrangement. The Different Types Of Automobile Chassis Frame Are As Follows: Conventional Frame:- It is non-load carrying frame. The loads of the vehicle are transferred to the suspensions by the frame. This suspension in the main skeleton of the vehicle, which is supported on the axles through springs. The body is made of flexible material like wood and isolated frame by inserting rubber mountings in between. The frame is made of channel section or tubular section of box section. 574 Divyanshu Sharma, Y D Vora
Ladder Chassis:-Ladder chassis is one of the oldest forms of automotive chassis these are still used in most of the SUVs today. It is clear from its name that ladder chassis resembles a shape of a ladder having two longitudinal rails inter linked by lateral and cross braces. Figure 1 chassis Types of ladder frame: Ladder frame are classified as follows. 1. C cross section type of ladder chassis frame 2. I cross-section type of ladder chassis frame. 3. Rectangular Box (Hollow) cross section type of ladder chassis frame. 4. Rectangular Box (Intermediate) cross section type of ladder chassis frame. II. Literature Review AshifIqubal, S. M. Oak et al. [4] (2013) has reviewed a design and analysis study that reduces chassis mass with also minimizing the cost impact. Considering the same material ST 52-3U for design of chassis and altering certain dimensions in cross sections used in chassis deign considerable amount of weight reduction have been achieved. Typical analytical method is being used for analyzing the results. N.Lenin Rakesh K.Gowtham Kumar et al. [5] (2014) has modelled chassis in CATIA software using actual dimensions. Material used here is Glass Fibber Reinforced Plastic. Steel Bedford s fiber glass reinforced plastic is highly corrosion resistant The main process involves with the both design and analysis of the model. At first all the possible design calculations are performed as per its physical specs, which later is used to convert the same into a 3D model so that it is easily perceptible. Once when done with the design process, structural analysis in which parameters like stress, strain and total deformation are applied,calculations are performed and all the properties are compared and represented graphically III. MethodologyEmployed Here, while redesigning the heavy duty trailer chassis keeping in mind weight reduction as main consideration with ease of manufacturing as per ISO, mainly the rigidity, strength, safety and economy are considered as main parameters for designing. According to Safety point of view, the design should be such that it should pass all safety norms as per give ISO standards so that it can move on safely on road without causing any damage. The high-end computer software s and CAD/CAE tools are used. The work is carried out step by step as below:- 1. Analysing of existing design of chassis 2. Improving/redesigning chassis as per ISO standard using different steel sections 3. Modeling and Analysis of the new improved chassis design through FEMsoftware. 575 Divyanshu Sharma, Y D Vora
Chassis specification: The specifications are as below Chassis:Sprung 9200 1125 mm size, st 42 a) Longbearers : Composite I-section of 450/250 140mm Cross section fabricated from 20mm thick plates b) Crossed bearers: 8 no. of hollow standard rectangular section and 2 T section ISST 250 as per ISO Body Size : Open box body - (9200 mm 2600 mm 1250 mm ) Length width height of box Basic chassis design calculation 1. MAIN CHASSIS LONG AND CROSS BEARERS : (a) Weight of long bearers :It is built up of composite I beam of 450/250 140 mm size from 20 mm thick plates as shown fig Specific weight 450 140 20 mm I beam = [(0.45 0.14) - ( 0.14 0.120)] 7860 = 108.47 kg/m Specific Weight of 250 140 20 mm I- beam = [(0.25 0.14) - ( 0.21 0.120)] 7860 = 77.03 kg/m Weight of two composite sections 9200 mm long bearers : = 2 [(1.45 77.03) + ( 7.50 108.47) + 0.25 ( 77.03 +108.47) / 2] = 1896.74 kg/m Weight of cross bearers: Specific Weight of standard hollow rectangular beam as per given standards for ISMC 200 150 is 22.1 kg/m and Specific Weight of standard T- section beam as per given standards for ISST 250 180 250 is 37.5 kg/m. Weight of cross bearers:= [ no. Of section used length of section specific weight ]= [8 2.6 22.1] + [2 2.6 37.5]= 654.68 kg Weight of main chassis : = total weight of two main long bearers + cross bearers = 1896.74 + 654.68 = 2551.42 kg or 2552 kg 2. WEIGHT OF CHASSIS FRAME : (a) Long bearers (sidebearers ) Size ISMC 250 sp. wt= 37.3 kg/m, Length = 9200 mm Weight = [no. of section used length of section specific weight] = 2 9.2 37.3 = 686.32 kg 576 Divyanshu Sharma, Y D Vora
(b) Riggers C-section: Size 250/ 50/150 mm in length 745 mm fabricated from5 mm plate. Specific Weight = [(0.25 + 0.05) / 2 + 2 (0.15)] 0.005 1860 = 17.685 kg/m Weight = ( 16 0.745 17.685 ) = 210.805 kg Weight of chassis frame : 686.32+210.805 = 897.152 kg or 898 kg Comparison for weight and induced bending stresss in chassis based on sections ( cross bearer ) Pre existing section New proposed sections Cases I SECTION HOLLOW RECTANGUALR AND T SECTUON weight 9300 kg 8760 kg 4.72 mm 2.72 mm IV. Finite Element Analysis There are three main steps, namely: pre-processing, solution and post processing. In pre-processing (model definition) includes: define the geometric domain of the problem, the element type(s) to be used, the material properties of the elements, the geometric properties of the elements (length, area, and the like), the element connectivity (mesh the model), the physical constraints (boundary conditions) and the loadings. In solution includes: the governing algebraic equations in matrix form and computes the unknown values of the primary field variable(s) are assembled. The computed results are then used by back substitution to determine additional, derived variables, such as reaction forces, element stresses and heat flow. Actually, the features in this step such as matrix manipulation, numerical integration and equation solving are carried out automatically by commercial software. 577 Divyanshu Sharma, Y D Vora
In post processing, the analysis and evaluation of the result is conducted in this step. Examples of operations that can be accomplished include sort element stresses in order of magnitude, check equilibrium, calculate factors of safety, plot deformed structural shape, animate dynamic model behavior and produce color-coded temperature plots. The large software has a pre-processor and postprocessor to accompany the analysis portion and the both processor can communicate with the other large programs. Specific procedures of pre and post are different dependent upon the program. The new model of chassis as per the dimension is as shown in Figure2.The model is then saved in IGES format which can be directly imported into ANSYS workbench. Figure 2 shows the imported model in ANSYS workbench. The model is being meshed up also. The meshing is done on the model with 274192 No. of nodes and 75694 No. of Tetrahedral elements. Figures sh2ow meshing of model Figure 2 Meshing Loading Condition of Chassis Frame The trailer chassis model is loaded by static forces from the truck body and load. For this model, the maximum loaded weight of loading container and body is 33660 kg. The load is assumed as a uniform distributed obtained from the maximum loaded weight divided by the total length of chassis frame. Detail loading of model is shown in Figure 3 and 4. Figure 3 Load distribution 578 Divyanshu Sharma, Y D Vora
Figure 4 Load variation Maximum deformation 2.78 mm Figure 5 Maximum deformation Figure 6 Stress distribution V Results: Chassissection ismodified by selecting hollow rectangular and T -section andanalysed for rigidity and weight compared and then with earlier design. The results are tabulated as below: Weigh of chassis(in kg) Bending stiffness of chassis(in KN/ mm) Saving in weight Improvement in chassis stiffness Existing design 9300 4.1 Modified/proposed design 8760 5.4 560 kg 75% 579 Divyanshu Sharma, Y D Vora
VI. Conclusion In the present work, heavy duty chassis frame was redesigned and analytically analysed along with an ANSYS analysis using ANSYS software, based on the analytic calculation and analysis following conclusion can be done. 1) The weight reduced to new proposed sections is about 560 kg. 2) Although the weight has been reduced to much extent but stiffness and rigidity remains the unchanged. 3) According to analysis it has been seen that a very little deformation oocur on the back side of the chassis which approximately negligible. REFERENCES [1]Yucheng Liu, Crashworthiness Analysis of Finite Element Truck Chassis ModelUsing LS-DYNA, 11th International LS-DYNA Users Conference, Department ofmechanical Engineering, University of Louisiana, Lafayette, LA 70504, USA. [2]Vijaykumar V. Patel, R. I. Patel, Structural analysis of a ladder chassis frame,world Journal of Science and Technology 2012, 2(4):05-08, ISSN: 2231 2587. [3]HemantB.Patil, SharadD.Kachave, EknathR.Deore, Stress Analysis of AutomotiveChassis with Various Thicknesses, IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE), Vol. 6, Issue 1 (Mar. - Apr. 2013), PP 44-49 [4]AshifIqubal, S. M. Oak, R. S.Kharatmal Analytical Optimization ofchassisframe for 40ft Dual-Axle Flatbed Trailer Design, IOSR Journal ofmechanical and Civil Engineering (IOSR-JMCE),Volume 7, Issue 6 (Jul. -Aug. 2013), PP 7684 [5]N.Lenin Rakesh, K.Gowtham Kumar, Dr. J. Hameed Hussain Design and Analysis of Ashok Leyland Chassis Frame Under 25 Ton Loading Condition,IOSRJournal of Mechanical and Civil Engineering (IOSR-JMCE),Vol. 3, Issue 11,November 2014 [6]Chassis calculations for Frame design FU14-116,6 th edition, Deckonkutzisinstitute of Linkoping university technology. [7] Code of Practice for Type Approval of Automotive Trailers Draft AIS-113/F7 23-Oct-2012, finalised draft automotive industry standard,page 1of 49. [8]Modern Automotive Technology 7th Edition, James Duffy, TheGoodheart-Wilcox Company, Inc., 2009. (ISBN: 978-1-59070-956-6) [9]Automotive Chassis Systems 4th Edition, James D. Halderman, Pearson Prentice Hall, 2008. (ISBN-13: 978-0-13-238487-2) [10]An Introduction to Modern Vehicle Design,Edited by, Julian Happian-Smith [11]Dutta, D., Würker, K.G.: HandbuchHohlprofile in Stahlkonstruktionen, Verlag TÜV Rheinland GmbH, Köln, Germany, 1988. ISBN 3-88585-528-3. [12]EN 10210-1: Hot finished structural hollow sections of non-alloy and fine grain structural steels - part 1: Technical delivery conditions, 1998. 580 Divyanshu Sharma, Y D Vora