ABSTRACT
Gear drives are widely used in various fields and applications due to their properties and capacity. Their versatility, durability, and ability to transmit high torques as well as precision and reliability make them extremely useful in many fields of technology. They are widely used in industrial and energy machinery, vehicle drive systems, aerospace, medical devices, and many other areas. Gears can be manufactured using many technologies. This work focuses mainly on machining with particular emphasis on high-performance new technologies. The process of mathematical modeling of the gear and the machined profile is strongly related to CNC machining technologies. A robust correlation of systems supporting the design and modeling of sliding gears needed for the manufacturing process is presented in the article. It is very important to properly assess gears with correct manufacturing in accordance with a specific standard. The article presents an analysis of available methods for controlling gears using coordinate measurement techniques. Gear machining methods were assessed in terms of the technologies used as well as their productivity and manufacturing tolerance.
ABSTRACT
No-tillage (NT) is a major component of conservation agricultural systems. Challenges that have arisen with the adoption of NT include soil compaction, weed management, and stratification of organic matter and nutrients. As an attempt to overcome these challenges, occasional tillage (OT) has been used as a soil management practice in NT systems. However, little is known about the impacts of OT on agronomic and environmental factors. For this reason, the objectives of this meta-analysis were: 1) to summarize the effects of OT on crop productivity, soil physical, chemical and biological properties, soil erosion and weed control; 2) to discuss the main aspects of NT management to optimize the use of OT; 3) to point out shortcomings in the diagnosis of soil compaction in NT systems, which may lead to erroneous decision-making processes regarding the use of OT. Overall, OT did not affect crops yields, although increased crop yields were observed in regions under water restriction and in soils with low retention capacity and water availability; OT improved soil physical properties (penetration resistance, soil bulk density, macroporosity, and total porosity), with persistence, generally, greater than 24 months, and decreased the soil aggregates stability; total organic carbon was reduced, particularly when plow/harrow was used and NT was already consolidated, and there was no effect on pH and available P; OT increased microbial biomass carbon, but had no effect on total microbial activity; soil erosion was reduced due to increased soil-water infiltration and reduced runoff, and finally, weed management was also improved by OT. It is suggested that suitable NT implementation and management, with the correct application of NT principles, will overcome problems associated with NT. As soil compaction is the main justification for the use of OT, methods of diagnosis and monitoring of soil compaction should be improved to assist in decision-making.
ABSTRACT
O tráfego de máquinas agrícolas é considerado uma das principais fontes da compactação do solo. Uma prática utilizada para minimizar os efeitos da compactação é a escarificação, porém a haste escarificadora pode causar compactação subsuperficial. O objetivo deste trabalho foi avaliar a influência do tráfego de máquinas na compressibilidade de um Argissolo Vermelho-Amarelo distrófico arênico, de textura franco arenosa e avaliar o comportamento mecânico desse solo abaixo da linha de atuação da haste escarificadora. Os tratamentos investigados foram: semeadura direta há 13 anos, semeadura direta há 13 anos com tráfego adicional (intensidade de tráfego de 24,67Mg km ha-1), cultivo mínimo recém implantado e cultivo mínimo recém implantado com tráfego adicional. Para a determinação da densidade do solo, de índice de vazios, da pressão de preconsolidação e do coeficiente de compressão, foram coletadas amostras nas camadas de 0,0-0,10m, 0,10-0,20m, 0,20-0,30m e 0,30-0,40m. O tratamento semeadura direta há 13 anos apresentou a menor capacidade de suporte e maior suscetibilidade à compactação. A intensidade de tráfego de 24,67Mg km ha-1 aumentou a densidade do solo e reduziu o índice de vazios até 0,20m. A escarificação não afetou a pressão de preconsolidação e o coeficiente de compressão do solo na camada abaixo da linha de atuação da ponteira do escarificador.
Farm machinery wheeling is considered a major source of soil compaction. The use of chisel plow can minimize such effects, but the chisel can cause subsurface compaction. The aim of this study was to evaluate the effect of traffic and is present below the compaction layer thought compressive parameters of soil. The treatments investigated were: no-tillage, no-tillage with additional traffic (traffic intensity of 24.67Mg km ha-1), no-tillage chiseling recent implanted, no-tillage with additional traffic and chiseling recent implanted. For the density, void ratio, preconsolidation pressure and coefficient of compressibility determination in the layers 0.0-0.10m, 0.10-0.20m, 0.20-0.30m and 0.30 to 0.40m samples were collected. The treatment no-tillage showed the lowest load support capacity and greater susceptibility to compaction. The traffic intensity of 24.67Mg km ha-1 increased bulk density and decreased void ratio until 0.30m depth. The chisel plow did not affect the preconsolidation pressure and coefficient of compressibility of soil layer below the line of action of the chisel tip.
ABSTRACT
A avaliação da qualidade física dos solos agrícolas tem assumido importância cada vez maior, principalmente em áreas sob sistema plantio direto, uma vez que nesse sistema de manejo ocorrem importantes alterações na estrutura do solo. A resistência mecânica do solo à penetração (RP), o intervalo hídrico ótimo (IHO) e a densidade relativa (DR) têm sido apresentados como opções para essa avaliação. Os objetivos deste trabalho foram avaliar e modelar a RP em função da umidade e densidade do solo e determinar o IHO em função da DR em dois sistemas de manejo. Amostras de solo com estrutura preservada foram coletadas na camada de 0-5cm, em solo sob plantio direto (PD) e plantio direto escarificado (PDE) há seis meses. Em laboratório, determinou-se a RP utilizando penetrômetro eletrônico e efetuou-se um ajuste estatístico individual para cada manejo à equação de Busscher. No PDE, para uma mesma densidade e umidade do solo, a RP foi menor que no PD, e a diferença na RP foi maior entre os dois manejos quando a umidade do solo no campo foi menor. O IHO foi maior no PDE até a DR 0,9. Os resultados permitem concluir que a RP é um parâmetro sensível para determinar a qualidade estrutural do solo e que o PDE reduziu significativamente a RP e aumentou o IHO, o que proporcionará melhores condições para o desenvolvimento radicular das plantas por um período de tempo maior.
The assessment of the physical quality of agricultural soils has taken on added importance, especially in areas under no tillage, as important changes to soil structure occur as a result of this type of management. Soil resistance to penetration (RP), the least limit water range (LLWR) and relative density (RD) have been used as evaluation parameters. The aim of this study was to assess and model RP as a function of soil moisture and density and to determine the LLWR as a function of RD under two management systems. Samples of soils under no tillage (NT) and chiseled no tillage (CNT) for six months and whose structure had been preserved were collected at a depth of 0 to 5cm. In the laboratory, RP was assessed using an electronic penetrometer and each management system was statistically adjusted to Busscher's equation. In CNT soils, RP was lower for the same density and moisture, and lower than the PD, whereas the difference in RP was larger between the two management systems when soil moisture in the field was lower. The LLWR was higher under CNT up to an RD of 0.9. Results allow us to conclude that RP is a sensitive parameter for determining the physical quality of the soil and that CNT significantly reduced RP and increased the LLWR, providing favorable conditions for root growth for a longer time period.
ABSTRACT
Proporcionar condições ótimas ao desenvolvimento das plantas deve ser um dos objetivos do manejo do solo. O sistema plantio direto é um manejo conservacionista por excelência, mas tem apresentado problemas de compactação, afetando o desenvolvimento e à produtividade das culturas. A escarificação esporádica do solo nessas áreas tem-se apresentado como uma alternativa para minimizar os efeitos negativos do aumento da sua densidade. Neste estudo, avaliou-se a densidade do solo, a porosidade total e de aeração, a densidade máxima e a relativa do solo e o rendimento de grãos de trigo num Latossolo em duas áreas: plantio direto há 6 anos (PD) e plantio direto escarificado (PDE). Durante todo o ciclo da cultura do trigo, monitorou-se o potencial de água no solo por meio de sensores eletrônicos e "datalogger". A escarificação esporádica do solo sob sistema plantio direto diminuiu (5 por cento) a densidade e a densidade relativa do solo, aumentou a porosidade total e alterou a dinâmica da água no solo, proporcionou maior volume de poros livres de água (7,6 por cento) durante todo o ciclo da cultura do trigo e aumentou significativamente o rendimento de grãos (682kg ha-1).
The soil management should be aimed at providing optimal conditions for plant growth and development. No-tillage is a quintessential conservative system; however, it has caused compaction, thus affecting crop development and yield. Sporadic soil chiseling in these areas has been used as an alternative to minimize the negative effects of an increase in bulk density. The soil bulk density, total porosity, air-filled porosity, maximum density, relative density, and wheat grain yield of an oxisol were assessed in two areas: under no-tillage for 6 years and under no tillage chiseled. Soil water potential was monitored throughout the wheat crop cycle by using electronic sensors and a datalogger. Results show that sporadic chiseling of the soil under no-tillage reduced soil density and relative density by 5 percent, increased total porosity and changed the soil water dynamics, resulting in a higher volume of water-free pores (7.6 percent) throughout the wheat crop cycle, remarkably increasing grain yield (682kg ha-1).
