Experimental and theoretical study on workpiece temperature when tapping hardened AISI H13 using different cooling systems

Tapping operations on hardened steels have always been a great challenge. Dry machining and two cooling systems were used when tapping hardened AISI H13 (53 HRC). Embedded thermocouples were used for temperature measurement close to the thread diameter in the radial and axial direction. A FEA model was used to evaluate the heat "Q", and coefficient of convection "h". The lowest temperature peak occurred with the flooded system, followed by the MQL, and dry condition. The heat and coefficient of convection increased when using the flooded system, followed by the MQL, compared to the dry condition. Those values were also in accordance with early published works, using different techniques.FAPEMI

Evaluation of the Restricted Air Entry on the Discharge Rate from Silos

Storage and distribution of solid materials, as well as control under powder discharge, has been fundamental to ore transportation and lately, Additive Manufacturing (AM). AM demands fine powders materials to be fed with high accuracy, by hoppers. It is not only the reliability of flow that becomes important but also to have a trace of repeatability of material discharges and flow characteristics. In this perspective, two types of hopper feeders have been utilized the most: screw feeder and scraper feeder. In the present work, the characteristics of a steady granular flow through an orifice in scraper feeders with a flat and conical bottom have been experimentally investigated under the influence of top ventilation. The discharge rate of granular particles of magnesium, alumina, glass beads and crushed glass have been studied as a function of the outlet diameter and the ventilation configuration. Tests were performed three times under the same configuration, which consisted for both apparatuses, a measurement of discharge time and the mass through outlet orifices of 15, 30 and 50 mm, with different vent area percentage. The results have shown that the discharge rate increases with the increasing outlet diameter and top ventilation in the majority of the materials studied. In both hopper geometries, a rise in mass flow rate was generally observed when ventilation was added to the system, even though the difference when doubled the vent area was not significant

Enhanced grinding performance by means of patterned grinding wheels

In this paper, a new and innovative method for the patterning of grinding wheels is presented. The patterns are machined with a patterning tool by using fly-cutting kinematics. By changing the patterning process parameters, different pattern sizes and densities can be machined in a flexible way. Surface and cylindrical grinding experiments show that grinding with patterned grinding wheels can significantly reduce process forces, grinding burn, and grinding power. The surface roughness increases because less active cutting edges remain when grinding with patterned wheels. But especially for roughing processes, the results show great potential for increasing the overall grinding performance. The final publication is available at Springer via http://dx.doi.org/10.1007/s00170-014-6579-8.DFGFAPES

Catálogo Taxonômico da Fauna do Brasil: setting the baseline knowledge on the animal diversity in Brazil

The limited temporal completeness and taxonomic accuracy of species lists, made available in a traditional manner in scientific publications, has always represented a problem. These lists are invariably limited to a few taxonomic groups and do not represent up-to-date knowledge of all species and classifications. In this context, the Brazilian megadiverse fauna is no exception, and the Catálogo Taxonômico da Fauna do Brasil (CTFB) (http://fauna.jbrj.gov.br/), made public in 2015, represents a database on biodiversity anchored on a list of valid and expertly recognized scientific names of animals in Brazil. The CTFB is updated in near real time by a team of more than 800 specialists. By January 1, 2024, the CTFB compiled 133,691 nominal species, with 125,138 that were considered valid. Most of the valid species were arthropods (82.3%, with more than 102,000 species) and chordates (7.69%, with over 11,000 species). These taxa were followed by a cluster composed of Mollusca (3,567 species), Platyhelminthes (2,292 species), Annelida (1,833 species), and Nematoda (1,447 species). All remaining groups had less than 1,000 species reported in Brazil, with Cnidaria (831 species), Porifera (628 species), Rotifera (606 species), and Bryozoa (520 species) representing those with more than 500 species. Analysis of the CTFB database can facilitate and direct efforts towards the discovery of new species in Brazil, but it is also fundamental in providing the best available list of valid nominal species to users, including those in science, health, conservation efforts, and any initiative involving animals. The importance of the CTFB is evidenced by the elevated number of citations in the scientific literature in diverse areas of biology, law, anthropology, education, forensic science, and veterinary science, among others

An inverse method to estimate the moving heat source in machining process

The present work propounds an inverse method to estimate the heat sources in the transient two-dimensional heat conduction problem in a rectangular domain with convective bounders. The non homogeneous partial differential equation (PDE) is solved using the Integral Transform Method. The test function for the heat generation term is obtained by the chip geometry and thermomechanical cutting. Then the heat generation term is estimated by the conjugated gradient method (CGM) with adjoint problem for parameter estimation. The experimental trials were organized to perform six different conditions to provide heat sources of different intensities. This method was compared with others in the literature and advantages are discussed. (C) 2012 Elsevier Ltd. All rights reserved.FAPESPFAPES

TEMPERATURE AND HEAT FLOW WHEN TAPPING OF THE HARDENED STEEL USING DIFFERENT COOLING SYSTEMS TEMPERATURA Y FLUJO DE CALOR AL ROSCAR CON MACHOS ACERO ENDURECIDO UTILIZANDO DIVERSOS SISTEMAS DE LUBRICACIÓN

Machining hardened steels has always been a great challenge in metal cutting, particularly for tapping operations. In the present paper, temperature was assessed when tapping hardened AISI H13. Dry machining and two cooling/lubrication systems were used: flooded and minimum quantity of fluid (MQF) with 20ml/h, both using mineral oil. The tapping operation was performed on 100 x 40 mm, 14 mm thick workpieces with 55 HRc. An implanted thermocouple technique was used for temperature measurement at distances very close to the highest thread diameter (at 0.1, 2.5 and 5.0 mm). Three thermocouples were used for each distance along the workpiece diameter at 3.0, 7.0 and 11.0 mm from the tap entrance. Measurements were replicated twice for each condition tested. An analytical theoretical heat conduction model was used to evaluate the temperature at the tool-workpiece interface and determine the heat flow and convection coefficient. The smallest temperature increase and heat flow were observed when using the flooded system, followed by the MQF, compared to the dry condition. The effect was directly proportional to the amount of lubricant applied, as well as with the MQF system, when compared to dry cutting.Trabajar los aceros endurecidos siempre ha sido un desafío para el corte de metales, particularmente en las operaciones de roscado. En el presente trabajo se mide la temperatura del acero AISI H13 endurecido, realizándose ensayos sin lubricación (seco) y dos sistemas con lubricación: aceite lubricante en grandes cantidades y mínima cantidad de líquido (minimum quantity of fluid MQF) a 20 ml/h, en ambos casos se utilizó aceite integral mineral. El roscado se realiza sobre probetas de prueba de 100 x 40 mm con 14mm de espesor y dureza de 55 HRc. Para medir la temperatura se utiliza la técnica de termocuplas situadas muy próximas al diámetro mayor del hilo de rosca (a 0.1, 2.5 y 5 mm de distancia). Se utiliza tres termocuplas a lo largo del espesor de la probeta de prueba a 3.0, 7.0 y 11.0 mm desde la entrada del roscado. Se hacen dos réplicas del registro de la temperatura para cada condición de corte ensayada. Se utilizan un modelo teórico-analítico de conducción de calor para evaluar la temperatura en la interfase de la probeta de prueba, determinar el flujo de calor y el coeficiente de convección. El menor incremento de la temperatura y del calor se observa al utilizar el método lubricante en grandes cantidades, seguido por el de MQF, al comparar con la condición en seco. El efecto es directamente proporcional a la cantidad de lubricante aplicado, siendo también significativo con el sistema MQF al compararlo con el corte en seco

An inverse method to estimate the moving heat source in machining process

The present work propounds an inverse method to estimate the heat sources in the transient two-dimensional heat conduction problem in a rectangular domain with convective bounders. The non homogeneous partial differential equation (PDE) is solved using the Integral Transform Method. The test function for the heat generation term is obtained by the chip geometry and thermomechanical cutting. Then the heat generation term is estimated by the conjugated gradient method (CGM) with adjoint problem for parameter estimation. The experimental trials were organized to perform six different conditions to provide heat sources of different intensities. This method was compared with others in the literature and advantages are discussed. (C) 2012 Elsevier Ltd. All rights reserved.FAPESPFAPES

Experimental investigations of heat transfer coefficients of cutting fluids in metal cutting processes: analysis of workpiece phenomena in a given case study

This paper reports an experimental method to estimate the convective heat transfer of cutting fluids in a laminar flow regime applied on a thin steel plate. The heat source provided by the metal cutting was simulated by electrical heating of the plate. Three different cooling conditions were evaluated: a dry cooling system, a flooded cooling system and a minimum quantity of lubrication cooling system, as well as two different cutting fluids for the last two systems. The results showed considerable enhancement of convective heat transfer using the flooded system. For the dry and minimum quantity of lubrication systems, the heat conduction inside the body was much faster than the heat convection away from its surface. In addition, using the Biot number, the possible models were analyzed for conduction heat problems for each experimental condition tested.FAPESPFAPESP [2007/00338-0

Desgaste de ferramentas no torneamento com alta velocidade de corte da superliga waspaloy

Nesse trabalho, procurou-se estudar os mecanismos de desgaste de diversas geometrias de ferramentas cerâmicas (Al2O3 + SiCw e Al2O3 + TiC) e ferramentas de PCBN. Para isto foram realizados ensaios de torneamento com alta velocidade de corte em uma superliga à base de níquel (Waspaloy) com dureza de aproximadamente 40 HRC sob condição de corte a seco. As superligas são conhecidas como materiais de difícil usinabilidade devido à alta dureza, alta resistência mecânica em alta temperatura, afinidade para reagir com materiais da ferramenta e baixa condutividade térmica. Os resultados mostraram que o material da ferramenta e a geometria influenciaram o comportamento dos mecanismos de desgaste. de uma maneira geral, o tipo de desgaste dominante foi o de entalhe e os mecanismos foram abrasão, attrition (aderência com arrastamento) e provável difusão na maioria das ferramentas utilizadas.The purpose of this work is to study the wear mechanisms in several geometries of ceramic tools (Al2O3 + SiCw and Al2O3 + TiC) and PCBN tools. Several high speed turning experiments were accomplished in nickel-base superalloy (Waspaloy) with hardness of approximately 40 HRC under dry cutting condition. The nickel based superalloys are known as difficult to cut materials due to their high hardness, high mechanical straight at high temperature, chemical affinity to tool materials and lower thermal conductivity. The results showed that the material of the tool and geometry influence the behavior of wear mechanisms. In general, the dominant type of wear was notching and the mechanisms were abrasion, attrition and probable diffusion in most of the used tools