Agricultural Tractor Cabin Structure Design for Durability and Rollover Protective Structure Test 2015-26-0163
A cabin on an agricultural tractor is meant to protect the operator from harsh environment, dust and provide an air conditioned space. As it is an enclosed space, cabin structure should be a crashworthiness structure and should not cause serious injury to operator in case of tractor roll over. There are International standard like OECD Code 4, SAE J2194 which regulates the crashworthiness of this protective structure. The roll-over protective structure (ROPS) is characterized by the provision of space for a clearance zone large enough to protect the operator in case of tractor overturn. None of the cabin parts should enter into the clearance zone for operator safety. In addition to meeting ROPS test criteria, the cabin structural strength should be optimized for the required tractor life.
In this paper, simulation process has been established to design an agricultural tractor cabin structure and its mountings to meet the above requirements. A Design Verification Plan (DVP) has been developed consisting of 3 load cases. Loads and boundary conditions have been arrived at based on the OECD Code 4 and road & field excitations. Design acceptance criteria have been formulated for clearing the ROPS test and durability for the tractor life. Virtual validation has been done by performing (i) A non-linear elasto-plastic simulation in ABAQUS for ROPS test and (ii) Static & modal analysis in MSC Nastran for durability. For ROPS test, equivalent plastic strain approach has been used for predicting the crack initiation and for durability analysis, fatigue based approach has been used for predicting the life. Lab test has been done for the ROPS test and has been correlated with CAE results. At the end, further design iteration has been done for mass and cost reduction. Biggest challenge in this work was to meet the above criteria within the constraint of material availability and manufacturing limitation.