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Tractor cabin skelet optimization
Saňák, Stanislav ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This thesis addresses the issue associated with the design of the tractor cabin frame. Agricultural machinery, including tractors, is utilized for work in highly challenging conditions such as fields or forest terrains, characterized by uneven, hilly, and often unpaved surfaces. Working in such extremely hazardous environments poses a significant challenge, especially for the operators of these machines. It is very common for drivers to lose control of the vehicle while navigating such terrain, resulting in the tractor tipping over on its side or roof, and in worse cases, experiencing repeated rollovers due to inertia. In such situations, the presence of a protective frame around the tractor cabin is the only possible means of crew rescue. However, the rollover of such a vehicle imposes extreme stress on the cabin frame due to the weight of the tractor and often its cargo. Historically, rollovers have been the leading cause of accidents resulting in fatalities of tractor crews, which prompted the establishment of standards aimed at reducing this type of accident. Tractors are tested against these critical situations to ensure the maximum possible crew safety. Nowadays, every manufactured tractor must comply with these tests. Since these tests are of a destructive nature, it is more cost-effective and time-efficient to first conduct tests using numerical simulations, within which the tractor cabin is optimized to successfully pass the given tests. The actual test is then performed on the final, already optimized cabin frame. In this study, a numerical simulation using the finite element method was conducted on the tractor cabin skeleton for the ROPS (Roll-Over Protective Structure) test, which simulates the tractor overturning. Based on the simulation results, optimizations were made to the cabin that were necessary to pass this test, which consists of several load cases. The optimized cabin frame was subsequently subjected to a basic dynamic analysis (modal analysis). This analysis identified the natural frequencies of the cabin that could be excited in the event of typical excitations acting on this structure (road surface irregularities, vibrations from the engine unit, and so on). Finally, based on real values obtained from experimental measurements, a harmonic analysis was performed. This analysis monitored the response of the frame to excitations corresponding to actual excitations from the engine unit.
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