Sistema de medida de forças dinâmicas utilizando diafragmas piezelétricos para estudos dos mecanismos de corte de um único grão abrasivo visando a otimização do processo de retificação
Data
2022-01-07
Autores
Oliveira Junior, Reinaldo Götz de
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O estudo das forças presentes no processo de retificação possibilita o entendimento do mecanismo de remoção de material e a otimização dos parâmetros envolvidos nesse processo. As características construtivas da ferramenta de corte, que influem na sua eficiência e na qualidade da superfície da peça retificada, são em parte determinadas pelas forças que atuam no sistema abrasivo-ligante. Nesta tese de doutorado, é proposto um sistema de medida de forças dinâmicas como apoio nos estudos dos mecanismos de corte de um único grão abrasivo. Tal sistema de medida, construído a partir de diafragmas piezelétricos de baixo custo, é capaz de medir as componentes de força normal e tangencial presentes no processo de retificação plana. Também é apresentado aqui um método de calibração para o sistema de medida desenvolvido, que se fundamenta na Segunda Lei de Newton e que propõe o emprego de um sistema multissensor para o cálculo do impulso de força, decorrente do impacto de uma esfera metálica lançada em queda livre. O erro relativo apresentado pelo sistema de medida é de 4,62 % para a componente de força normal e de 6,47 % para a componente de força tangencial. Com base nas respostas em magnitude e frequência, o sistema de medida de forças, que inclui um circuito condicionador de sinais projetado com a configuração de um amplificador de carga, demonstra-se apropriado aos testes de riscamento a que fora submetido. O sistema também apresenta um bom compromisso entre custo e benefício, tendo seu custo de produção equivalente a 5,6 % do valor comercial do sistema usado como referência nos testes de calibração.
The study of the forces present in the grinding process enables the understanding of the material removal mechanism and the optimization of the cutting parameters governing this process. The constructive characteristics of the cutting tool, which influence its efficiency and the surface quality of the machined workpiece, are partly determined by the forces acting on the abrasive-binder system. In this PhD thesis, a dynamic force measurement system is proposed as an auxiliary tool in the study of cutting mechanisms of a single abrasive grit. Such a measurement system, built from low-cost piezoelectric diaphragms, is capable of measuring the normal and tangential component forces acting in the peripheral surface grinding process. It is also presented here a calibration method for the developed measurement system, which is based on Newton’s Second Law and proposes the use of a multisensor system for calculating the force impulse, due to the impact of a metallic sphere launched in free fall. The relative error presented by the measurement system is of 4.62 % for the normal force component and 6.47 % for the tangential force component. Based on the magnitude and frequency responses, the force measurement system, which includes a signal conditioning circuit designed in the configuration of a charge amplifier, proved to be appropriate for the scratching tests to which it was submitted. The system also presents a good compromise between cost and benefit, having its production cost equivalent to 5.6 % of the commercial value of the system used as a reference in the calibration tests.
The study of the forces present in the grinding process enables the understanding of the material removal mechanism and the optimization of the cutting parameters governing this process. The constructive characteristics of the cutting tool, which influence its efficiency and the surface quality of the machined workpiece, are partly determined by the forces acting on the abrasive-binder system. In this PhD thesis, a dynamic force measurement system is proposed as an auxiliary tool in the study of cutting mechanisms of a single abrasive grit. Such a measurement system, built from low-cost piezoelectric diaphragms, is capable of measuring the normal and tangential component forces acting in the peripheral surface grinding process. It is also presented here a calibration method for the developed measurement system, which is based on Newton’s Second Law and proposes the use of a multisensor system for calculating the force impulse, due to the impact of a metallic sphere launched in free fall. The relative error presented by the measurement system is of 4.62 % for the normal force component and 6.47 % for the tangential force component. Based on the magnitude and frequency responses, the force measurement system, which includes a signal conditioning circuit designed in the configuration of a charge amplifier, proved to be appropriate for the scratching tests to which it was submitted. The system also presents a good compromise between cost and benefit, having its production cost equivalent to 5.6 % of the commercial value of the system used as a reference in the calibration tests.
Descrição
Palavras-chave
Processo de retificação, Diafragma piezelétrico, Medida de força, Método de calibração, Grinding, Piezoelectric diaphragm, Force measurement, Calibration method