Design and Analysis of Army Vehicle Chassis * Tandra Naveen kumar 1 N.Jeevan Kumar 2

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1 Design and Analysis of Army Vehicle Chassis * Tandra Naveen kumar 1 N.Jeevan Kumar 2 1PG Student (M. Tech- CAD/CAM, 2 Associate Professor, Dept. of Mechanical Engineering, Holy Mary Institute of Technology and Science, Jawaharlal Nehru technological University, Hyderabad, India. Abstract- In the current project manual design calculations of the army vehicle chassis are performed initially and the same design has been validated using finite element analysis. The following analysis was carried out to study the structural integrity of the Army vehicle chassis under various loading conditions. Firstly a static analysis with only equipment loads applied. Secondly static analysis in deployment mode. (The vehicle is lifted from ground with jacks. Loads on Army vehicle chassis include equipment as well as bare vehicle weight). Thirdly Modal analysis to find the Natural Frequencies was carried out. From the results obtained some changes were proposed and implemented to reduce the deflections and stresses and also efforts are made to increase the fundamental natural frequency of the chassis. Keywords: Army vehicle Chasis, Deflections, Stress, Modal analysis. 1 INTRODUCTION Chassis is a major component in a vehicle system. For vehicles, chassis consists of an assembly of all the essential parts of a vehicle (without the body) to be ready for operation on the road. This project deals with the design optimization of the Army vehicle chassis for the different loading conditions. Army vehicle chassis is steel welded Structure of size built on the vehicle. The Army vehicle chassis is used for carrying Shelter mounted Electronic Equipment and its accessories. The Design of the Vehicle Army vehicle chassis is carried so as to carry the below mentioned items. The Army vehicle chassis design is optimized to keep the weight of the Army vehicle chassis to the minimum. Finite Element Analysis is carried out for verification. The Army vehicle chassis has provision to fix the following major equipment. Shelter: A Shelter will be fixed on to the Army vehicle chassis with bottom four ISO corners using four Twist locks provided on the Army vehicle chassis. Generators: One Generator is mounted on the front portion of the Army vehicle chassis (behind Driver s Cabin).A frame covering the Generators with a provision for the exhaust and hot air outlet with maintenance door is provided. Mast: Mast is located between the Shelter and Generators. For better stability and to obtain verticality, the DF mast is located centrally. The Army vehicle chassis is fixed with Manual leveling Jacks which can be easily operated by the Operator. By leveling the Army vehicle chassis, the Mast is made Vertical. ISSN: Page 138

2 THEORITICAL CALCULATIONS: DESIGN CALCULATIONS OF ARMY VEHICLE CHASSIS Shear load (σ) = 24 kg(f)/mm^2 Total Load on the Chassis (w) = 4 tons Weight trasmitted at each Point Load(W) = w*1000/4 = 4*1000/4 = 1000 kgs Distance between Rails(L) = 1582 mm Distance between Shaft Loading Brackets(Lb) =888mm Maximum Bending Moment(Bmax1) = w*(l-lb)/2 = 1000*( )/2= Kg-mm Max Bending Moment(Bmax) = Bmax1/1000 = /1000 =347 kg(f)- m Required Sectional Modulus(Zr) = Bmax1/σ = mm^3 Sectional Modulus of flat bed C Section for Long Member Height of C-Section (h2) = 75 mm Width of C-Section (w2) = 40 mm Web Thickness of C-Section (t2) = 6 mm Flange Thickness of C-Section (Ft2) = 6mm Length of Box Section (L2) = 2460 mm Moment of Inertia(MI2) = (w2*h2^3- (w2-2*t2)*(h2-2ft2)^3)/12 = mm^4 Sectional Modulus(Z2) = MI6/h2/2 = mm^3 Considered Sectional Modulus of connecting flange Height of C-Section (h3) = 63 mm Width of C-Section (w3) = 25 mm Web Thickness of C-Section (t3) = 4 mm Flange Thickness of C-Section (Ft3) = 4mm Moment of Inertia(MI6) = (w3*h3^3- (w3-2*t3)*(h3-2ft3)^3)/12 = mm^4 Sectional Modulus(Z6) = MI6/h3/2 = mm^3 Required Sectional Modulus of Long Member Box Section Considered type Cantilever as the long member of Chassis is constrained all the sides Shear load (σ) = 24 kg(f)/mm^2 Total Load on the Chassis (w) = 4 tons Distance between Rail Wheels along length (L) = 1582 mm Distance between Roller Support and load Left Side (L1) = 653mm Distance between Roller Support and load Right Side (L2) = 653 mm Left Side Reaction(Rl) = w*1000/4 = 1000 Kgs Right Side Reaction(Rr)= w*1000/4 = 1000 Kgs Bending Moment Left Side(Bl) = Rl*L1 =1000*653 = Kg(f)-mm ISSN: Page 139

3 Bending Moment Right Side(Br) = Rr*L2 = 1000*653= Kg(f)-mm Maximum Bending Moment on the long member (Bmax2) = Max(Bl, Br) = Max (653000, ) = Kg(f)-mm Max Bending Moment(Bmb) = Bmax2/1000 = /1000 = 653 kg(f)- m Required Sectional Modulus(Z4) = Bmax2/ σ =653000/24 = mm^3 Required Sectional Modulus of flat bed Box Section Left Side Reaction(Rl) = w*1000/4 = 300 Kgs Right Side Reaction(Rr)= w*1000/4 = 300 Kgs Bending Moment Left Side(Bl) = Rl*L1 =1000*300 = Kg(f)-mm Bending Moment Right Side(Br) = Rr*L2 = 1000*300= Kg(f)-mm Maximum Bending Moment on the long member (Bmax2) = Max(Bl, Br) = Max (120000, ) = Kg(f)-mm Max Bending Moment(Bmb) = Bmax2/1000 = /1000 = 120 kg(f)- m Required Sectional Modulus(Z4) = Bmax2/ σ =120000/24 = 5000 mm^3 3D MODEL OF ARMY VEHICLE CHASSIS ASSEMBLY Considered type Cantilever as the long member of Chassis is constrained all the sides Shear load (σ) = 24 kg(f)/mm^2 Total Load on the Chassis (w) = 1.2 tons Distance between Rail Wheels along length (L) = 1576 mm Distance between Roller Support and load Left Side (L1) = 400mm Distance between Roller Support and load Right Side (L2) = 400 mm Fig. 1 The 3D Model of army vehicle chassis assembly FINITE ELEMENT ANALYSIS The material properties used for the design of Army vehicle chassis is given below. ISSN: Page 140

4 Frame: This consists of C sections made from wieldable quality hot-rolled structural steel IS: , Grade A, Fe 410WA. Mechanical Properties: Tensile Strength = 410 Mpa Yield Strength = 250 Mpa Density = 7850 kg/m3 The component weight is applied as Loads on the army vehicle chassis, the distribution of the load is shown in the below table. Below Table-1 Shows the total Loads applied on the army vehicle chassis S.No Equipment Operators Total Weight(kg) 1. Generator+Generator Cover Battery Bank Mast+Accessories Flat bed 710 converted into a parasolid to import into ANSYS. A Finite Element model was developed with shell and mass elements. The elements that are used for idealizing the Army vehicle chassis Assembly were described below. A detailed Finite Element model was built with shell and mass elements to idealize all the components of the Army vehicle chassis. Modal analysis was carried out to find the first 6 natural frequencies and their mass participations. Changes were also implemented to shift the fundamental natural frequency.the elements that are used for idealizing the Army vehicle chassis are Shell 63and Mass 21. STATIC ANALYSIS FOR EQUIPMENT LOAD Structural static analysis is performed on the army vehicle chassis by applying all the weights of the components which are mounted on the chassis. From the analysis the maximum stresses and deflections are identified and documented. The boundary conditions and loading applied on the chassis are shown in the below figure. 5. Shelter 1200 TOTAL 3685 FINITE ELEMENT MODELING: 3D model of the Army vehicle chassis assembly was developed in UNIGRAPHICS from the design calculations done. The model was then ISSN: Page 141

5 STATIC ANALYSIS IN DEPLOYMENT MODE During deployment condition the vehicle is lifted from ground with jacks. The purpose of this condition is when the vehicle is on the slanting or rugged ground, the mast will becoming slant. To keep the mast always vertical the vehicle is lifted on the leveling jacks. During this condition Loads on Army vehicle chassis include equipment as well as bare vehicle weight and wind load. The boundary conditions and loading applied on the chassis are shown in the below figure. Fig. 2 Boundary conditions and loading conditions applied for static analysis Fig. 4 Boundary conditions and loading applied for static analysis in deployment condition Fig.3 Deflections and stress plots for static analysis ISSN: Page 142

6 From the above results obtained in static analysis in deployment condition some high stressed locations were observed and to reduce the stresses additional C-sections were introduced as shown in the below figure. From the modal analysis it is also observed that there is a huge deflection at the center part of the chassis. To avoid this deflection and to increase the fundamental natural frequency an additional support structure is added as shown in the below figure. Fig. 5 Deflections and stress plots for static analysis during deployment MODAL ANALYSIS Modal analysis was carried out to determine the first 10 natural frequencies and mode shapes of a structure. A Block Lanczos mode-extraction method is used to extract the frequencies and mode shapes. Eigen values and their mass participations in all the three directions for the first 10 natural frequencies are listed in the below Table. Fig.7 Modifications made on the chassis Fig. 6 1 st Mode shape@12.3hz ISSN: Page 143

7 MODE FREQUENCY PARTICIPATION FACTOR EFFECTIVE MASS X-Dir Y-Dir Z-Dir X-Dir Y-Dir Z-Dir E E E E E E E E E E E E E E E E E E E E E E E E E E-04 Table. 2 Eigenvalues and Mass participation in X, Y and Z directions RESULTS AND DISCUSSIONS In this project manual design calculations of the chassis are performed initially and the same design has been validated using finite element analysis. The following analyses were carried out to study the structural integrity of the Army vehicle chassis to identify the maximum stressed locations under various loading conditions. Modal analysis was also carried out to find the first 10 natural frequencies to understand the dynamic behavior of the structure. Based on the results some changes were proposed and implemented on the chassis. It was observed that there was a 65% reduction in the stress value and 50% reduction in the total deflection for the static analysis with equipment load condition. It was also observed that the there is a 21% reduction in the stress value and 20% reduction in the total deflection value for the static analysis in deployment condition. It was also observed that the fundamental natural frequency is increased by 22% for the modified chassis as compared to the original one. Fig.8 Comparison graph of natural frequencies for original and modified chassis CONCLUSIONS Chassis is a major component in a vehicle system. For vehicles, chassis consists of an assembly of all the essential parts of a vehicle (without the body) to be ready for operation on the road. ISSN: Page 144

8 In this paper the army vehicle chassis has been designed and optimized to reduce the stresses and deflections. Optimization was also done to increase the fundamental natural frequency. Initially the design was done with theoretical calculations. From the theoretical calculations the design was developed and the same design was validated using finite element analysis. Optimization was also done based on the finite element analysis results. From the finite element analysis results it is concluded that the optimized modified army vehicle chassis safe for the given operating conditions. Authors Profile: Tandra Naveen kumar has performed this work while he is pursuing post graduation in CAD/CAM department at Holy Mary Institute of Technology and Science, Jawaharlal Nehru technological University, Hyderabad, India N.JEEVAN KUMAR completed his B.TECH in year 1995 from NAGARJUNA UNIVERSITY and HE completed his M.TECH(CAD/CAM) in the year 2001 from JNTU,HYD. Now persuing Ph.D from OSMANIA UNIVERSITY. Having total 17 years of experiance.out of which 12 years of teaching and 5years of industry. References 1. Aird, Forbes. The Race Car Chassis. New York, New York: The Penguin Group, Gaffney, Edmund F., and Anthony R. Salinas."Introduction to Formula SAE Suspension and Frame Design." SAE Technical Paper Series, Riley, William B., and Albert R. George. "Design, Analysis, and Testing of a Formula SAE Chassis." SAE Technical Paper Series , Milliken, William F., and Douglas L. Milliken. Race Car Vehicle Dynamics. Warrendale, PA: Society of Automotive Engineers, Inc., Cicek Karaoglu,N. Sefa Kuralay Stress analysis of a truck chassis with riveted joints Finite Elements in Analysis and Design 38 (2002) , Department of Mechanical Engineering, DEU Faculty of Engineering, Bornova, Izmir, Turkey. 6. Mohd Azizi Muhammad Nora,b, Helmi Rashida, Wan Mohd Faizul Wan Mahyuddinb,Mohd Azuan Mohd Azlanc, Jamaluddin Mahmuda, Stress Analysis of a Low Loader Chassis International Symposium on 7. Dr.R.Rajappan, M.Vivekanandhan, Static and Modal Analysis of Chassis by Using Fea The International Journal Of Engineering And Science (Ijes) Volume 2, ssue 2,Page (2013) ISSN: Page 145