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Analysis of chassis

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Analysis of chassis

  1. 1. CADmantra Technologies Pvt. Ltd. All right reserved @ cadmantra technologies pvt. ltd. STRUCTURAL ANALYSIS OF A CHASSIS OF EICHER 11.10 USING “ANSYS” Bhola Patel Design Engineer CADmantra Technologies Pvt. Ltd. Contact: bholapatel.me@gmail.com ABSTRACT : Automotive chassis is an important part of an automobile. The chassis serves as an frame work for supporting the body and different parts of the automobile. Also, it should be rigid enough to withstand the shock, twist, vibration and other stresses. Along with strength, an important consideration in chassis design is to have adequate bending and torsional stiffness for better handling characteristics. So, strength and stiffness are two important criteria for the design of the chassis. This report is the work performed towards the optimization of the automotive chassis with constraints of stiffness, strength and natural frequency. The design improvement study performed resulted in a maximum torsional stiffness of 6448Nm/deg, an increase of 377% over the baseline model. A maximum increase in efficiency of 286% to 23g/Nm/deg for a mass of 148.3Kg accompanied this increase in torsional stiffness. Following optimization of the model to gain minimum mass for a stiffness of 6000Nm/deg a torsional stiffness of 6030Nm/deg was realised for a mass of 127Kg, giving an increase in efficiency of 322% over the baseline model to 20.99g/Nm/deg. 1. INTRODUCTION 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. 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, strength and lower weight provides the motivation for this project. The goal of the structural design is to obtain minimum component weight and satisfying requirements of loads (stresses), stiffness, etc. The process of producing a best structure having optimum structural performance is termed as structural optimization. Structural systems like the chassis can be easily analyzed for the stress, and stiffness, etc. using finite element techniques. The limitations on the stress, strength etc. are the constraints for optimization. 2. CASE STUDY The four models in this study represent the same bracket. It is rigidly supported at the back and loaded with uniform pressure applied to the top of the hollow cantilever. Each model produces different results. 3. MODEL It uses a first-order solid tetrahedral element which, by design, can only model constant stress within its volume. Knowing that, there are two big problems. First, only one element is placed across the thickness of the plate in bending. This model is not capable of representing bending stress which changes from compressive to tensile across the plate thickness. Consequently, bending stresses are badly represented by constant stress. The second problem is that the elements are highly distorted. Each type of element works well only if it is within specified shape limits. If element distortion is beyond these limits, then numerical procedures used to calculate displacements and stresses return false results. Figure 1. Results for Model show a maximum Von Mises stress of 18,000 psi
  2. 2. CADmantra Technologies Pvt. Ltd. All right reserved @ cadmantra technologies pvt. ltd. LOADS ON THE FRAME The frame experiences loads of different nature during motion of the vehicle. These loads, in turn, produce stresses and strains of various kinds. Generally, the following types of loads are sustained by the frame. FLEXURAL (OR BENDING) LOAD It is produced in a vertical plane of the side members due to  Dead weight of the vehicle  Weight of the passengers  Engine torque  Braking torque Flexure load also develops in lateral plane of the side members due to  road Camber  cornering force  side wind CALCULATION FOR EICHER E211.10 CHASSIS Model No. = 11.10 (Eicher E2) Capacity of Eicher = 8 ton Capacity of Eicher with 1.25% = 78480 N Weight of the Eicher = 2 ton Total Load acting on the Chassis = Capacity of the Chassis + Weight of Eicher Calculation of the Deflection for Individual Side Bar Mmax = 37526845 N-mm 76.20 203.20 h b1 b Moment of Inertia around the X – X axis:- Ixx = {bh3 – [b1(h)3 ]} / 12 = [(76.20 x 203.203 ) – (66.67 x 184.143 )] / 12 =18588475.09 mm3 Section of Modules around the X – X axis:- Zxx = {bh3 – [b1(h)3 ]} / 6h = [(76.20 x 203.203 ) – (66.67 x 184.143 )] / (6 x 203.20) = 182957.432 mm3 Basic Bending equation are as follow :=(M / I) = (σ / y) = (E / R) Material of the “C” channel:- Material : St 52 E = 2.10 x 105 N / mm2 Poisson Ratio = 0.28 Radius of Gyration R = (203.20 / 2) =101.60 mm Maximum Bending Moment acting on the Beam: - Mmax = 37526845 N-mm I = 18588475.09 mm4 Y = 101.60 mm CALCULATION FOR TORSIONAL STRESS GENERATED IN CHASSIS Reaction generated on Beam at the center of wheel alignment: - 29430 N With the consideration of at the rate of angle of twist = 1˚ θ = (1˚ x π / 180) = 0.017452 By considering the whole system as a one rotational body as per following data when in twist from its support. Width of the chassis: - 800mm Length of chassis; - 6900mm Distance between two reaction: - 4900mm Modulus of rigidity for structural steel: - 80000 N/mm2 Now basic rule for Twisting Moment is:- (T / J) = (τ / r) = (G x θ / L) Now equating (T / J) = (G x θ / L) For the rotational shaft J is 2 times higher the Mass Moment of inertia:- Mass moment of Inertia for Chassis body = 4.65 x 107 mm4 So, Polar Moment of Inertia J= 2 x I J= 2 x 4.65 x 107 J= 9.3 x 107 T = (G x θ x J) / L T = (80000 x 0.017452 x 9.3 x 107 ) / 6900 T = 18817808.70 N-mm Torsional stress generated in Chassis body :- Take width of body as a radius o rotational body r = 800mm (T / J) = (τ / r) τ = (T x r) / J τ = (18817808.70 x 800) / 9.3 x 107 τ = 161.87 N/mm2 4. CONCLUSION At present time the problem of enhancing safety is very actual for the world automotive industry and chassis is the backbone of the automotive system. Day by day modification has been done in existing system to increase strength and durability with minimum possible cost. Here is the one approach presented. This project represent to study the stress-distribution of automobile chassis. When different parts are mounted o n it at that time no. of stresses are produce in chassis. First Design stress is calculated then it was compare with the stress result of Finite element Analysis report by using pro-Mechanica tool. Its 9.53
  3. 3. CADmantra Technologies Pvt. Ltd. All right reserved @ cadmantra technologies pvt. ltd. comes within the limit So we can say that design is safe. 5. REFERENCES [1] Automobile Engineering – Vol.1 - K.M.Gupta , Umesh Publication – 2001, page no. 54 to 61 [2] Automobile Mechanics , Dr. N. K. Giri, Khanna Publisher, Delhi-2003, page no. 161 to 164 [3] Technical manual of Eicher E2 11.10, Apco motors pvt. Ltd., Himmatnagar. Eicher motors sells & service center. [4] www.eicherworld.com [5] Automobile Engineering, Vol.-I by Kirpal sing, Standard Publisher and Distributor, Delhi-2003. [6] Optimization of frameworks by means of FEM use, By J. GADUŠ, Slovak Agricultural University, Nitra, Slovak Republic, RES. AGR. ENG., 49, 2003 (1): 32–36 [7] Analysis of Torsional Stiffness and design improvement study of a Kit Car Chassis Prototype, by Wesley Linton, M.Sc. THESIS, CRANFIELD UNIVERSITY,SCHOOL OF INDUSTRIAL AND MANUFACTURING SCIENCE MOTORSPORT ENGINEERING AND MANAGEMENT 2001-2 [8] M.Tech. Dissertation “Structural Optimization of Automotive Chassis” By Roopesh Shroff, Department of Mechanical Engg. , IIT ,Bombay -Academic year 2002 [9] “Finite element analysis” by – Chandra Patla. [10] “Finite element analysis” by – Robert D. cook

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