ANALYSIS OF STABILIZER BAR USING SIMPLIFIED APPROACH Manoj Purohit Senior CAE-Analyst #128/A, Sanghavi Compound, Chinchwad Purohit.Manoj@mahindraengg.com Wadkar Yogesh CAE-Analyst #128/A, Sanghavi Compound, Chinchwad wadkar.yogesh@mahindraengg.com Shailesh Kadre Principal CAE Analyst #128/A, Sanghavi Compound, Chinchwad Kadre.shailesh@mahindraengg.com Shreyas Shingavi CAE-Analyst #128/A, Sanghavi Compound, Chinchwad Shingavi.shreyas@mahindraengg.com Kachyap Drishtipran CAE-Analyst #128/A, Sanghavi Compound, Chinchwad Kachyap.Drishtipran @mahindraengg.com Abbreviations: FEA: Finite Element Analysis Keywords: Stabilizer Bar, Tensor plots Abstract The purpose of the stabilizer bar is to reduce body roll and related lateral motion, during vehicle's turning. The stabilizer bar is part of vehicle's suspension system and is designed to increase the vehicle's roll stiffness. The primary purpose of this analysis is to develop a simplified analyses approach which includes the effect of pre-tension loads, snow plow unbalance loads and all the service loads which a typical heavy commercial vehicle experiences during its normal operating condition. Competition in automotive market has made reduction of development time and cost a necessity. This paper presents an approach of FEA and correlation of the results with the test results and helps the design to move to the next level of concept quickly. The approach includes the effect of pre-tension loads, snow plow unbalance loads and all the service loads which a typical heavy commercial vehicle experiences during its normal operating condition. Measured strain data was available for the stabilizer bar from the tests conducted. Correlation of the strain gauge data from the test and the results from FEA is carried out. In the present work good correlation for the location of high stresses, the magnitude and direction of the principal stresses is observed. Capabilities in the HyperWorks products were found to be very useful while doing this work. Scale factor was worked out to establish relation for the Tensor and its magnitude. The methodology developed was useful in saving cost and time for multiple iterations during design and test. Introduction Stabilizer bar also known as a sway bar or anti-sway bar or roll bar is a series of circular rods that connects wheels along with suspension units on an axle. These rods form a torsion spring. The purpose of the stabilizer bar is to reduce body roll and related lateral motion during a vehicle's turning. The primary purpose of this analysis is to develop a simplified analysis approach which includes the effect of pre-tension loads, snow plow unbalance loads and all the service loads which a typical heavy commercial vehicle experiences during its normal operating condition. Objective and Methodology Outline of Methods followed: This analysis is carried out in four steps. Step 1: Preloading of Stabilizer Bar Assembly Step 2: Snow plow loading Step 3: Application of Suspension loads Step 4: Superimpose of step1, step2 and step3 results Step 5: Comparison Study for Strains in FEA and Test Step 1: Preloading of Stabilizer Bar assembly: Forces are calculated to obtain desired displacement at the right link of the assembly. Forces are applied in equal and opposite directions as shown in Figure 2. All the tire patches are constrained. (See Figures 1 and 2). Simulation Driven Innovation 1
FIGURE 1: SCHEMATIC DIAGRAM OF TRACTOR WITH STABILIZER BAR FIGURE 2: SCHEMATIC DIAGRAM OF STABILIZER BAR ASSEMBLY FOR PRE- LOAD APPLICATION Step 2: Snow Plow Loading Snow plow load is applied at the CG location of the snow plow device in vertical direction and is connected to frame rail with RBE2, as shown in Figures 3 and 4. CG location is for the plow in upward and stored position on the right hand side of the vehicle. The tire patches are constrained. Simulation Driven Innovation 2
FIGURE 3: DESIGN DESCRIPTION FOR TRACTOR WITH SNOW PLOW FIGURE 4: DETAILS OF SNOW PLOW LOADING Step 3: Apply Front Suspension loads: Tramp Jounce Brake windup Aggressive left Aggressive right Simulation Driven Innovation 3
Step 4: Superimpose results of step 1,step 2 and step3 Displacement Analysis: Step1: The following figure shows the displacement contour for the frame after step 1 (pre-load) loading. FIGURE 5: DISPLACEMENT STEP 1 FIGURE 6: DETAILS OF THE FRONT SECTION The right side frame rail moves vertically upward and left side frame rail moves in downward direction due to pre loading of Stabilizer Bar Assembly. Step 2: The following figure shows the displacement plot for the frame after step 2 (snow plow) loading. Simulation Driven Innovation 4
FIGURE 7: DISPLACEMENT STEP 2 FIGURE 8: DETAILS OF THE FRONT SECTION STEP 2 The left and right side frame moves downward. Superimpose the displacements. These should be less than the maximum acceptance criteria. Step 3: Apply service loads. Results obtained from step 1, 2, 3 can be linearly super imposed. Step 5: Comparison Study of Strains in FEA and Test at Sway Bar Right End The analysis was performed for stabilizer bar for which the measured strain data was available from the test. The correlation of strain gauge data from Test and FEA results was undertaken. In the preset work, good correlation for the location of high stress, magnitude and direction of principal stress was observed. The measured strain value from delta type transducer and orientation of the Tensor along with its magnitude when compared with FEA results showed very good correlation. The scale factor was calculated using this relation and was used for scaling the stresses for the new design of the bracket. The methodology developed was useful in saving cost and time needed for multiple iterations of designing, and testing. Simulation Driven Innovation 5
Figure 8 shows the details of the current design. The comparison of test setup and Tensor plots from FEA are given in Figure 9. The result comparison of the Test and FEA is given in Table I. FIGURE 8: DETAILS OF CURRENT DESIGN FIGURE 9: DETAILS OF TEST SET AND TENSOR PLOTS FROM FEA STEP 5 Simulation Driven Innovation 6
TABLE I: COMPARISON OF RESULTS OF TEST VS FEA Transducer No. % difference FEA vs Test PQG28 17 PQG30 11 From the results above the scale factor is calculated and used for scaling the results in further analysis Scale factor = Test / FEA ~ 0.85 Benefits Summary 1. This is a simplified approach in which multistep non- linear complex problem is simplified by using linear static analysis. 2. Using the existing Radioss solver a full vehicle system analysis can be carried out without any additional investment. Conclusion The present method of simplified approach uses linear super position approach to solve vehicle level problem which is otherwise very costly if handled through commercially available non- linear codes. ACKNOWLEDGEMENTS The author would like to thank the following for their valuable technical inputs 1. Ajit Jha, Strength and Durability Analysis Manager, Navistar Inc., USA. 2. Deepak Nidgalkar, Head- CAE, Mahindra Engineering Service Ltd. REFERENCES [1] Gillespie, T. D., Fundamentals of Vehicle Dynamics, Society of Automotive Engineers Inc., USA, 1992 [2] Michael Blundell and Damian Harty, Multibody Systems Approach to Vehicle Dynamics, Elsevier Butterworth-Heinemann, 2004 [3] Reference guide of MotionView 9.0 of Altair HyperWorks ABOUT THE COMPANY Ltd., a Mahindra Group company, provides design analysis testing solutions to Navistar Inc.' and Mahindra Navistar and Automotive Limited (a Joint Venture between Mahindra & Mahindra and Navistar Inc. to develop and market commercial vehicle product line). Simulation Driven Innovation 7