Projeto e construção de uma célula de carga para medir força de tração em tratores agrícolas

Abstract

The pulling force, available on the agricultural implement drawbar, is the main parameter of comparison between various factors of agricultural tractors, such as hourly and specific consumption, for example. Thus, a traction force meter of agricultural implements that allows the acquisition of data in the time allows the evaluation of soil parameters referring to the regional reality, optimizing the work in the field. It also helps to identify critical points of operation under certain conditions of use / service. It is within this context that this work is located, whose objective is the design and construction of a load cell to measure the tractive force that an agricultural tractor exerts when pulling some implement. The project is initially done from numerical simulations through the Ansys Workbench software, for stress analysis, followed by the load cell manufacturing, with materials available at the UNIPAMPA / Campus Alegrete Mechanical Engineering course. The designed load cell utilizes strain gages or strain gages that are transducers that convert deformation into varying electrical resistance. Four strain gages are connected together in the form of a Wheatstone Bridge circuit that converts variation of electrical resistance into electric voltage variation. A device for connecting the load cell to the tractor and implement has also been designed and developed to ensure that it only undergoes axial loads when put into service. After the load cell was fabricated, it was calibrated using a universal test machine. Finally, the designed set (load cell and device) was used in experimental field tests, according to NBR 10400 and CODE 2 - OECD standards. The tests showed satisfactory and consistent results, validating the project. Calibration revealed the reproducibility of the designed load cell and high accuracy. The experimental field tests were performed in three load regimes and showed satisfactory results and were consistent with the expected, thus validating the developed project. The results also showed the complexity of performing a mechanical design, especially when it comes to a system that involves multidisciplinarity.