Optimization & Development of Vehicle Rear Under-Run Protection Devices in Heavy Vehicle (RUPD) for Regulative Load Cases

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1 IJIRST International Journal for Innovative Research in Science & Technology Volume 1 Issue 6 November 2014 ISSN (online): Optimization & Development of Vehicle Rear Under-Run Protection Devices in Heavy Vehicle (RUPD) for Regulative Load Cases Prakash Kumar Sen Faculty Rohit Jaiswal Student (Bachelor of Engineering) Shailendra Kumar Bohidar Faculty Rajesh Anant Student (Bachelor of Engineering) Ravi Bhardwaj Student (Bachelor of Engineering) Abstract The paper focuses on simulation, optimization & analysis of a Rear under Run Protection (RUPD) system under crash scenario. The basic objective is to improve the safety of the car and the occupants by designing the RUPD and car bumper. The choice of material and the structural design are the two major factors for impact energy absorption during a crash. It is important to know the material & mechanical properties and failure mechanism during the impact. This study concentrates on component functions, geometry, behavior of material and other parameters that influence the compatibility of the car bumper and rear under run protection device. This analysis is a partial work of a major project wherein the RUPD will be subjected to static tasting with variable load distributions at different location on RUPD.Under-running of passenger vehicles is one of the important parameters to be considered during design, optimization & development of heavy vehicle chassis. In INDIA, the legal requirements of a RUPD are fixed in regulation IS which are derived from ECE R 58, which provides strict requirements in terms of device design and its behavior under loading that the device needs to fulfill for the approval of load carrying vehicles. Keywords: IS (Indian Standards), ECE R-58(Economic Commission Europe Regulation-58), Optimization, Simulated annealing I. INTRODUCTION Heavy vehicles accidents represent a significant factor in the overall road accident scene. Analyzing the Indian problem (1995), heavy vehicle like a trucks with a gross vehicle weight Optimization & Development of Vehicle Rear Under-Run Protection Devices in Heavy Vehicle (RUPD) for Regulative Load Casesof more than 3.8 tonnes are involved in around 22% of the fatal road accidents and approximately 62% of these are car to truck accidents. The injury risk of accidents involving heavy vehicles appears to be far greater for occupants of opponent vehicles, especially for cars. And this risk increase in the case of car to truck frontal collisions. All rights reserved by 27

2 Fig.1 Typical Rear Under-run Collision [1] During such accidents the passenger compartment of the small vehicle strikes the chassis of the heavy vehicle causing severe injuries to passenger in the smaller vehicle. Underride accident are of three different types namely front, rear and side under run accidents. To avoid such accidents an under run device has to be installed on the heavy good vehicle which would prevent the passenger of the small vehicle from getting fatal injuries. [1] In this paper we are going to increase the bearing capacity of the RUPD. Without the installation of the RUPD the entire energy will be on the pillars of the car structure which in turn would not be able take such impact. Fig (1) show damage caused to small passenger vehicle during an rear underride accident. The entire vehicle has gone underneath the truck and the entire structure of the car has got crumbled due to the sudden impact load. Table (1) shows the death involved in the under-run accident in the USA till the year It shows that 97% (2782 deaths) of passenger vehicle occupants are killed in two-vehicle crashed involving a passenger vehicle and large truck and only 5% (75 deaths) of large trucks occupants are dying. [2] Table.1 Death involved in the under-run accident in the USA till the year 2003 Occupant Type Death % Passenger vehicle occupants Large vehicle occupants 75 3 All occupants deaths EEVC WG14 started 1994 a research programme for defining the requirements of energy absorbing front under run protection systems for truck, and for the development of a procedure for these devices. The overall objective of the project, consist of developing a test procedure and performance standard for energy- absorbing rear under run protection systems for trucks in order to reduced injuries to passenger car occupants in frontal collisions. Fig. 2: Rear Impact without RUPD [2] In fig (2) it is very much clear that in case of crash without the RUPD the impact of the truck is on the passenger compartment due to the under running of the car under the truck. The energy absorption is not there before the impact of truck will take place to the passenger compartment so due to this there will be high energy collision and as a result more fatalities will occur.[3] All rights reserved by 28

3 II. REAR UNDER RUN PROTECTION DEVICE RUPD is a right part located on the rearmost side of a heavy duty vehicle in order to protect the passenger cars under-running from rear side of the vehicle, as seen in fig (3). Safely designed RUPDs helps to avoid the fatal and injury crashes of passenger cars and their underride collision to the vehicle rear side. It has been revealed that when a passenger car travels at a speed of 70 km/h and hits to a standing heavy duty truck with zero speed from the full head on, the passenger car will feel a deceleration of 38g or more which will also translate to the passengers inside. This possible life threatening decelerative impact increase directly to 46g or more when the passenger car speed increase from 70 to 100 km/h.[1] Fig. 3: RUPD on a heavy duty truck chassis [1] The maximum distance between the RUPD and the chassis of the vehicle must be not more than 450mm (side view). The RUPD must have maximum ground clearance as 550mm. It should have good load bearing capacity and must not come out of its fitment possition during the time of the impact. The height of the transversal profile of the device should not be smaller than 100mm. The side edges of this profile should not be cuverd back and should not have any sharp edges. [4] Fig. 4: Design and Mounting of RUPD Model RUPD s have two major effects on the outcome of crashes:- Firstly under run can expose light vehicle occupants to direct contact with rigid structural parts of the vehicle before the light vehicles crashworthiness has fully come into play. Secondly components of the heavy vehicle (e.g. Rear axle) can be compromised to the degree that, the vehicle is not controllable in coming to a stop or the vehicle can not be move after the collision.[1] III. RUPD MODEL The modeling of the Rear Under Run Protection Device has been done in CATIA V5 R17. The full assembly model of the rear under graed and its different components are shown in following Fig (5), shows the chassis and the guard pipe. The chassis is part on which whole body structure of the vehicle is mounted and the guard pipe comes in contact of the striking vehicle. All rights reserved by 29

4 Fig. 5: Chassis & Guard of RUPD Fig (6), the support bracket is the main connecting parts between the chassis and the guard pipe. These are the main part which take strength and energy absorption test. Fig. 6: Support Bracket and Stiffener IV. TEST PROCEDURE AND FEA MODEL OF RUPD A. Test Procedure: The test procedure for rear under run protection device is mentioned below of derived from the ECS R-58 and IS regulation. The order in which the forces are applied may be specified by the manufacture. A Quasi Static analysis was conducted on the Rear Guard assembly and its load bearing capacity is tested. A Quasi test is a slow form of the dynamic test and is used when a dynamic code is used to produced static result. A horizontal force of 100 KN or 50% of the force generated by the maximum mass of the heavy vehicle, whichever is lesser, shall be applied consecutively to two pointssituated symmetrically about the center line of the device of the vehicle whichever is applicable at a maximum distance apart of 700mm and maximum of 1m. A horizontal force of 50 KN or 25% of the force generated by the maximum mass of the heavy vehicle, whichever is lesser, shall be applied consecutively to two points locate mm from the longitudinal planes tangential to the outer edges of the wheels on the rear axle and to a third third point locate on the line joining this two points, in the median vertical plane of the heavy vehicle. A horizontal force of 50 KN or 20% of the force generated by the maximum mass of the heavy vehicle for which the device is intended, whichever is lesser, shall be applied consecutively to two point locate at the discretion of the manufacture of the rear under protective device and to a third poing loacte on the line joining this two ponit, in the median vertical plane of the device. In order to test RUPD according to ECE-R58 regulation, a test rig is constructed. Half chassis frame platfornm with a RUPD was rigidly mounted on the rigid test plate. 250 kn, hydraulic MTS TM actuator is also mounted on the same rigid test plate. The actuator is placed in parallel to the ground. A ball joint is attached to the tip of the hydraulic actuator in order to protect its shaft from transverse forces. In conjunction with ECE-R58 regulation, a test mandrel is machined in dimensions as 250mm in height, 200mm wide, and 10mm thickness, with a radius of curvature of (5+1) or (5-1) mm at the vertical edges. The test mandrel is mounted to the tip of the piston via four bolt connections. It was possible to attach the hydraulic actuator to a suitable location which is explained in ECE-R58 load application points. Those points are clearly represented in fig (7).[5] Table.2 Regulative Load Cases[5] Load Case Time (s) Force (kn) P P P3 0 0 All rights reserved by 30

5 There are three load cases for RUPD testing, which are defined in ECE-R58. P1 load case is the worst condition for the RUPD bumper beam. P2 load case is the worst condition for the RUPD beam mounting brackets to chassis frame. P3 load case is applied at the mid-section of the beam, which is not the severest condition at all. For this reason three replicative tests for P1 and P2 load cases are developed consequently, whereas, P3 load case was not necessary to be applied for the correlation study, as it is concluded by the team. In order to preserve the accuracy of the tests, every part on the RUPD for every test, has been renewed, except the chassis frame. The loading procedure of regulative test force, which is defined in ECE-R58, is presented in above table (2). B. Test Results A RUPD performance is approved according to ECE-R58 regulation, when the RRPD withstands 50 and 100 kn impact forces applied to the P1 and P2 positions respectively. As indicated earlier P1 is the worst load condition for the RUPD beam, whereas, P2 is worst load condition for the RUPD beam and chassis mounting brackets. ECE-R58 replicative real lifr test results of P1 and P2 are represented in Fig (7) and Fig (8). As shows in Fig (7), three replicative tests, P1_1, P1_2 and P1_3, fit onto each other, thus adequacy of the tests are confirmed. All test according to ECE-R58 norms. Fig (8), presents the P2 loading conditions for real life tests. Similar to P1 tests, three replication is also developed with ECE_R58 tests. Three of these results are compatible with ECE-R58, moreover chassis and RUPD beam mounting brackets are found to be more durable than expected.[6] Fig. 7: Test results for P1 (P1_1,P1_2,P1_3)[5] Fig. 8: Test results for P2 (P2_1,P2_2,P2_3)[5] C. Tensile Tests For Material Non-Linear Curve Assessment: As the FE model should be developed with material non-linerity assumptions, material stress-strain curves are necessary. ISO 6892 is the tensile testing standards of all metal types, including tube sections. For that reason, RUPD beam s tensile tests are conducted according to ISO 6892, see Fig (8). Stress-strain curves measured for the whole test parts are represented in Fig (10). Those data are used for the material cards of the FE analysis.[7] Fig. 9: Tensile test part specs for RUPD beam acc. To ISO 6892[7] All rights reserved by 31

6 Fig. 10: Stress-strain curves for RUPD beam according to ISO 6892[7] D. FE Model: In order to analyze the structural integrity of the RUPD system, a non-linear finite element model is developed using the commercially available code RADIOSS, which is widely used in automobile industry. The model is composed of a relevant portion of the stiffer truck chassis, on which the RUPD is mounted. The chassis portion is fixed for every DOFs. Non-linear material model is used. FE base model is shown in Fig (11). The best way to correlate FE simulation is to compare with the physiscal tests. At RUPD physiscal tests structural integrity and bolt failure can be captured easily. The correlated FE model should also verify these two failure modes. The tested RUPD system structure is modeled by shell elements in order to properly represent the structural characteristics of the sheet metal components. The bolts are modeled via beam elements and failure of the bolts is checked both for stresses of the beam and for clamping forces. The boundary condition of the RUPD system and actuator are constructed in line with physiscal tests. The ram is modeled as rigid and concentrated load is used as the loading condition.[8] Fig. 11: FE Model[8] E. FE Results: P1 and P2 loading is applied for the CAE in order ot verify the real life testing of RUPD. First of all, FE analysis of RUPD tube structural integrity is performed at P1 loading position, similar to the physiscal tests. Resultant force deflection curve and tube bucking behaviour of P1 load case is presented in Fig (12). After words, FE analysis of RUPD chassis brackets struvtural integrity is developed at P2 loading position, similar to real life testing. Resultant force deflection curve of P2 load case is presented in Fig (13). All rights reserved by 32

7 Fig. 12: FE results of P1 loading[8] Fig. 13: FE results of P2 loading[8] V. CONCLUSION The final results of the real life tests and the FE analysis of the P1 loading is represented in below Table (3). The present study dealing with the starte of deformation of the RUPD beam element. For that reason, P2 loading case, which represents the deformation state of the RUPD brackets, is out of the scope of this study. Table. 3 Correlation of the real life test and FE model for RUPD Max Force (kn) Load Case Testing Force (kn) Testing FE simulation P REFERENCES [1] Lambert, J., Rechnitxzer,G., Review of Truck Safety Stage, Frontal, Side and Rear Underrun Protection. Project for VICROADS, Report No.194, Monash University, Accident Research Center, 2002 [2] Matej Glavac, Univ.Dipl.Ing., Prof. Dr. Zoran Ren University of Maribor, Faculty of Mechanical Engineering. [3] Safety inspection of rear underrun protection device in Slovenia (No ), Uradni list RepublikeSlovenije, No. 3, [4] Liu Hong-Fei and Peng Tao Xu Hong-Guo, Tan Li-dong and Su Li-li College of Transportation University of Jilim, Changchun, Jilim province, Chinna Project on the Intelligent Rear Under-run Protection System of Heavy Vehicles 6 July 2010, Jinan, China. [5] ECE-R58 regulation, Rear Under run Protection. [6] Kaustabh Joshi, T.R. Jadhav, Ashok Joshi Finite Element Analysis of Rear Under-run Protection Deviec (RUPD) for Impact Loading IJERD ISSN: X, Volume 1, Issue 7 (June 2012), [7] ISO 6892, Metallic Materials-Tensile Testing. [8] Joseph, G, Shinde, D., and Patil, G., Optimazation & Development of the RUPD using FE Model. All rights reserved by 33