STUDY OF STIFFNESS BALANCE BETWEEN CHASSIS AND CABIN MOUNT IN FRONT IMPACT OF CABIN OF COMMERCIAL VEHICLE 2019-01-1034

During development of a cabin for any commercial vehicle program, meeting the strength requirements of front impact as per regulation (AIS-029) is a very critical milestone. AIS-029 regulation consists of three destructive tests, i.e. Front Impact Test (Test A), Roof Strength (Test B) and Rear Wall Strength (Test C). Simulation of frontal impact test (Test A – AIS-029), study of stiffness balance between chassis and cabin mount and its correlation with physical test is demonstrated in this study. Frontal Impact Test consist a swing bob, which strikes the cab with 45 kJ impact energy (for vehicles for which permissible maximum mass > 7T). This energy should be absorbed by cabin and allied structures. Enough survival space post impact to accommodate manikin and cabin should remain attached to the chassis are the two primary requirements of this test. From energy absorption point of view, the cabin chassis interface plays a very critical role. Front cabin mount is the most critical part of this interface and takes initial impact of swing bob. Hence stiffness balance between chassis and cabin mount is studied in details here to arrive at best balancing combination to meet the strength requirements. Front cabin mount was modeled in detail with solids (Hex) and given material failure limit. Bolts between front cabin mount and chassis are given pretension during simulation. Thus we were able to achieve real time material and bolt failure in simulation and its cumulative effect on the whole deformation pattern. Detailed modeling of the cabin along with vehicle chassis, suspension system etc. has been done. Boundary conditions, e.g. ropes and wooden blocks as like in physical test were represented well in CAE model. Deformation pattern of cabin front panels, cabin mount, long members on the floor and chassis studied in details and test results correlated quite well with simulation results. Thus, this study of frontal impact, various sensitive parameters and stiffness balance approach formed a base defining design strategy for cabin to meet frontal impact requirements.