Correlation of test results for ECE R 29 load cases with CAE ...

Correlation of Test Results for ECE R 29 Load Cases With CAE Simulation Joseph Philip,

Sujit Mungale

Manager Ashok Leyland Ltd. Vellivoyal Chavadi Chennai-600 103, India

Divisional Manager Ashok Leyland Ltd. Vellivoyal Chavadi Chennai-600 103, India

Abbreviations: expansion of any abbreviations used. Keywords: ECER 29, Frontal crash, Radioss Abstract The application of virtual simulations of crash has become an integral part of the vehicle development process. Virtual simulation offers opportunities to reduce development time and the number of physical prototypes consumed for design verification and validation. With the continuous increase in accident and regulatory scenario, the dependency to virtual simulation and validation is becoming an inseparable factor in product development. This paper presents simulations that are performed to verify various safety aspects to ensure crashworthiness of the truck cabin. The cabin structure was evaluated for various load cases as per ECE r29 rev 2.0 safety regulation. FE simulation was validated through physical test and correlated for frontal impact test and roof strength test as per AIS 029/ECE r29 rev 2.0. Paper also covers the challenges faced while correlating Analysis with Physical Test. Analysis was carried out through Altair explicit solver RADIOSS.

Introduction Commercial vehicle safety in India is mainly governed by regulatory requirement. For trucks ECE r29/AIS 031 is one of the important requirement. Test specifications (refer figure 1) are as follows:

1. Frontal impact test (Pendulum impact) 2. Roof Strength test 3. Rear wall strength test

. Figure 1: Load requirement as per ECE r 29 /AIS 29

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Frontal Impact test Frontal impact test is simulated to evaluate the strength of the cab in case of the frontal crash. As per the test requirement the cab is impacted by pendulum with a energy of 45 or 30 KJ. The energy of impact depends on the GVW of the vehicle. To meet the requirement, after the impact there should be gap between the manikin and the non-resilient parts. Roof Strength test Roof strength test is simulated to evaluate the strength of the roof in case of rollover. In the event of roll over, vehicle rest upside down with the axle load coming directly on the roof. As per the requirement, the roof of the cab would withstand a static load corresponding to the maximum mass authorized for the front axle or axles of the vehicle, subject to a maximum of 10,000 kgf. This load should be distributed uniformly over all the bearing members of the roof structure. Load is applied through suitable-shaped rigid former. To meet the requirement, after the application of load, there should be gap between the manikin and the roof parts. Rear wall strength test Rear wall strength test is simulated to evaluate the strength of rear wall to withstand a static load of 200 kgf per tonne of permissible useful load. This load should be applied by means of a rigid barrier perpendicular to the longitudinal median axis of the vehicle, covering at least the whole of the cab rear wall situated above the chassis frame, and moving parallel to that axis.To meet the requirement there should be gap between the manikin and the rear panel after the application of the load. This paper outlines the systematic approach for evaluation of truck for ECE r29 loads. FE model of a truck cabin was developed using Ashok Leyland standard modelling techniques. The model was validated through correlation study in frontal impact test and quasi-static roof strength as per ECE r29. CAE results were correlated with baseline frontal crash test. FE modeling techniques were reviewed and modified based on development tests and again revalidated in final certification tests. The correlation study provided confidence on the FE model in terms of modeling techniques, material characteristics, bolt force monitoring and failure methods etc. The correlated FE model was used for simulating various load cases to observe the status of the cabin structure not only in regulatory tests, but also for some commonly observed accidental scenarios assuming that the initial correlation achieved holds good for these similar boundary conditions.

Process Methodology The finite element modeling is done using shell elements with appropriate integration points through the thickness. Parts are connected using bolts (beam elements) and spot welds. An average element size of 10 mm is used along with the global quality parameters for jacobian, warpage, element minimum and maximum angles, aspect ratio, skew angle etc. The kinematics at the respective locations was represented using proper FE joint definitions. The approach for modelling and conversion of CAD to FE model is as explained in Figure 2. The simulations presented in this paper were performed using RADIOSS explicit solver.

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Figure 2: Approach is applied from the CAD data to FE analysis Baseline frontal Impact Test Base line analysis was carried out without any bolt failure .The bolt force were monitored and it was observed that shear force at front mounting bolts are above the design load. The analysis was rerun considering the bolt failure and CAE predicted that there will be front mounting failure and which may lead to cab shifting during frontal impact test.

Figure 3: Baseline model

Figure 4: Bolt forces Improvements suggested from CAE Based on the Baseline CAE analysis the front mounting were found to be stiff, also the mounting bolt grade need to be changed to higher grade. The bracket was redesigned and three stiffeners on mounting bracket were replaced with two stiffeners and also the bolt location was rearranged, so that the force is uniformly distributed during frontal impact. The modified analysis showed very good results and no mounting or bolt failure was observed. Below image shows the internal deformed view of cab after frontal impact.

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Figure 5: Improved Cab with CAE inputs Test was carried out and the cab cleared the test with very good correlation level and similar deformation behaviour as per Test.

Figure 6: Improved Cab with CAE correlation Table 1 : CAE vs. Test comparison Sr. No 1 2

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Dimensions Manikin chest to Steering wheel - Bottom Manikin knee to Dashboard - Left

Test vs .CAE difference (mm) 1 4

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Results & Discussions Using CAE tools like RADIOSS, number of physical tests and thereby saving lot of cost and time can be reduced. This also enhances multiple choices of design variation and verification. Simulation has helped in bringing down the number of physical test.

Benefits Summary Using CAE tools like RADIOSS, number of physical tests and thereby saving lot of cost and time can be reduced. This also enhances multiple choices of design variation and verification. Having got good correlation in vehicle level, confidence levels are increased to optimize the product design and this will even help in avoiding physical tests.

Challenges Key challenges involved in this project was selection of right front bracket design and relying on the bolt forces and bolt failure criteria's and validation of RADIOSS for correlation levels which were already established in Ashok Leyland with other software's.

Future Plans Based on the observations in the complete exercise and correlation study, the process of bolt model and bracket approach can be implemented in initial phase of design validation. The results will be conservative and will help in meeting the vehicle safety requirements.

Conclusions A good correlation in terms of deformations and bolt failure was observed in physical test and RADIOSS simulation of frontal crash. Based on the correlation exercise using RADIOSS, bracket modifications and the grade of bolt to be fixed were carried out and was confidently implemented to the final design. ACKNOWLEDGEMENTS I would like to express my sincere thanks to Dr. Sarma S.R. Akella for his continuous support. Apart from him, I would also like to thank to AL validation team members for their continuous support and input to make my job easier. [1] [2]

REFERENCES United Nations; Uniform technical prescriptions concerning the approval of vehicle with regard to the protection of the occupants of the cab of a commercial vehicle. Regulation 29. Altair HyperWorks 11.0 Help

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