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Advisor(s)
Abstract(s)
Este trabalho diz respeito ao dimensionamento de uma máquina de recolha e limpeza de castanhas, capaz de suprimir a falta de mão de obra e possibilitar a redução do custo da operação de coleta, garantindo o aumento da qualidade do produto com um trabalho mais atempado. Inicialmente procedeu-se ao estudo dos vários tipos de máquinas presentes no mercado, afetas à recolha e limpeza de castanhas, com o intuito de compreender o modo de funcionamento e assentar melhorias. Uma das lacunas verificadas prende-se com o facto deste tipo de máquinas não produzir resultados aceitáveis em terrenos com inclinação, o que levou ao estudo de sistemas de nivelamento implementados em máquinas agrícolas com capacidade de operação em terrenos acidentados, de forma eficiente e segura.
Após a verificação inicial do estado da arte, sucedeu-se a fase de modelação geométrica de uma máquina de recolha de castanhas por vácuo, montada em trator agrícola. Nesta fase recorreu-se ao software SOLIDWORKS para criar inicialmente a geometria do chassis da máquina através de ferramentas especificas de membros estruturais, seguindo-se a criação de cada peça constituinte da máquina onde foram utilizadas frequentemente ferramentas para chapa. Para a montagem das várias peças, utilizaram-se subconjuntos para reduzir o número de peças por montagem e assim tornar mais prática a organização da montagem final que engloba todos os subconjuntos.
Uma vez que o chassis desempenha uma importante função estrutural, sendo responsável pela integridade da máquina, efetuou-se uma análise estática que permitiu determinar a combinação de tensões resultantes, a localização de concentração de tensões, os deslocamentos e o fator de segurança.
Posteriormente, efetuou-se o dimensionamento dos órgãos mecânicos, procedendo-se ao dimensionamento dos veios à cedência através de critérios de tensão limite de cedência, à rigidez tendo sido avaliada a flecha, rotação e torção e foi efetuada a verificação à fadiga considerando critérios específicos para o efeito. Para os rolamentos que dão suporte aos veios utilizados na sequência de transmissão de potência, foram calculadas as capacidades de carga estática e dinâmica e estimada a vida útil. Foram também dimensionados sistemas de transmissão de potência, por correia em V, por corrente de elos e por engrenagem de dentado reto. Considerando fatores como a potência de trabalho e a relação de transmissão pretendida em cada secção, foram também escolhidos a parir de catálogos, redutores e multiplicadores mecânicos.
This work concerns the sizing of a machine for collecting and cleaning chestnuts, capable of suppressing the lack of manpower and making possible the reduction of the cost of the collection operation, guaranteeing the increase of the product quality with a timelier work. Initially we proceeded to the study of the various types of machines present in the market, assigned to the collection and cleaning of chestnuts, to understand the operation mode and to establish improvements. One of the gaps found is that this type of machines does not produce acceptable results on sloping terrain, which led to the study of leveling systems implemented in agricultural machines capable of operating on rough terrain, in an efficient and safe way. After the initial verification of the state of the art, a geometric modeling phase was carried out for a tractor-mounted vacuum nut harvesting machine. In this phase, SOLIDWORKS software was used to initially create the geometry of the machine chassis using specific tools for structural members, followed by the creation of each constituent part of the machine where sheet metal tools were often used. For the assembly of the various parts, sub-assemblies were used to reduce the number of parts per assembly and thus make it more practical to organize the final assembly that encompasses all the sub-assemblies. Since the chassis plays an important structural role, being responsible for the integrity of the machine, a static analysis was performed to determine the resulting combination of stresses, the stress concentration location, the displacements, and the safety factor. Subsequently, the mechanical parts were sized, proceeding with the design of the shafts to yielding through yield stress criteria, to stiffness, having been evaluated the deflection, rotation and torsion and the fatigue verification was performed considering specific criteria for this purpose. For the bearings supporting the shafts used in the power transmission sequence, the static and dynamic load capacities were calculated, and the service life was estimated. Power transmission systems, by V-belt, link chain and spur gear, were also dimensioned. Considering factors such as the working power and the desired transmission ratio in each section, reducers and mechanical multipliers were also chosen from catalogs.
This work concerns the sizing of a machine for collecting and cleaning chestnuts, capable of suppressing the lack of manpower and making possible the reduction of the cost of the collection operation, guaranteeing the increase of the product quality with a timelier work. Initially we proceeded to the study of the various types of machines present in the market, assigned to the collection and cleaning of chestnuts, to understand the operation mode and to establish improvements. One of the gaps found is that this type of machines does not produce acceptable results on sloping terrain, which led to the study of leveling systems implemented in agricultural machines capable of operating on rough terrain, in an efficient and safe way. After the initial verification of the state of the art, a geometric modeling phase was carried out for a tractor-mounted vacuum nut harvesting machine. In this phase, SOLIDWORKS software was used to initially create the geometry of the machine chassis using specific tools for structural members, followed by the creation of each constituent part of the machine where sheet metal tools were often used. For the assembly of the various parts, sub-assemblies were used to reduce the number of parts per assembly and thus make it more practical to organize the final assembly that encompasses all the sub-assemblies. Since the chassis plays an important structural role, being responsible for the integrity of the machine, a static analysis was performed to determine the resulting combination of stresses, the stress concentration location, the displacements, and the safety factor. Subsequently, the mechanical parts were sized, proceeding with the design of the shafts to yielding through yield stress criteria, to stiffness, having been evaluated the deflection, rotation and torsion and the fatigue verification was performed considering specific criteria for this purpose. For the bearings supporting the shafts used in the power transmission sequence, the static and dynamic load capacities were calculated, and the service life was estimated. Power transmission systems, by V-belt, link chain and spur gear, were also dimensioned. Considering factors such as the working power and the desired transmission ratio in each section, reducers and mechanical multipliers were also chosen from catalogs.
Description
Mestrado em IPB-ESTG
Keywords
Análise estática Apanha de castanhas Modelação geométrica Órgãos mecânicos Transmissão de potência