Tarefas para a Aprendizagem de Estatística no Ensino Secundário com Calculadora Gráfica

Neste trabalho pretende-se estudar a introdução de metodologias didáticas para a abordagem de conceitos estatísticos, no ensino secundário, utilizando a calculadora gráfica. Atendendo a que a maioria dos alunos hoje em dia vive rodeado de tecnologia, e dentro de uma lógica de resolução de problemas matemáticos, a generalidade das tarefas propostas têm como pressuposto a utilização da calculadora gráfica. São assim desenvolvidas e adaptadas tarefas matemáticas que têm por objetivo o estudo de estatística, recorrendo às potencialidades das calculadoras gráficas, nomeadamente fazendo uso dos módulos de estatística, de representação gráfica de funções e de geometria dinâmica, presentes, por exemplo, na TI-nspire da Texas Instruments, modelo com que se pretende trabalhar as tarefas propostas, embora algumas delas possam ser resolvidas recorrendo a outros modelos de calculadoras gráficas. Foi utilizada uma metodologia de investigação de natureza qualitativa, recorrendo essencialmente a uma técnica de análise documental. Partiu-se de uma revisão de literatura que permite contextualizar as questões relacionadas com o currículo e o desenvolvimento curricular, o uso da tecnologia e as principais características que as tarefas devem observar. Os materiais criados para a sala de aula, que incidem sobre o desenvolvimento curricular, agindo essencialmente sobre o currículo prescrito para o ensino secundário, nomeadamente no domínio de Estatística, permitem rever alguns conceitos introduzidos no ensino básico, como sejam: gráficos de barras, gráficos circulares e diagramas de extremos e quartis e as medidas de localização como a moda, média, mediana e quartis, e introduzir as medidas de dispersão e as amostras bidimensionais. As questões às quais este trabalho pretende dar resposta são: Como se carateriza o currículo prescrito com estatística? Como pode ser moldado o currículo prescrito integrando a tecnologia? Como é que se materializam modelos de ensino-aprendizagem, no domínio da estatística, recorrendo à utilização da calculadora gráfica? De que forma a utilização da calculadora gráfica pode influenciar o currículo? Sob um ponto de vista transversal à disciplina de matemática, são abordados igualmente a modelação matemática e a resolução de problemas; construção do raciocínio matemático e a utilização e exploração de tecnologia gráfica

INVESTIGATION OF DRILLABILITY OF INCONEL 718

Bu çalışmanın amacı, Inconel 718'in delinebilirliği için kuru kesme koşulları altında optimum delme şartlarını tespit etmektir. Bu amaçla, süper alaşım Inconel 718'in kaplamalı ve kaplamasız karbür matkaplarla delinmesi esnasında kesme parametrelerinin; kesme kuvvetleri, yüzey pürüzlülüğü, delik kalitesi ve talaş oluşumu üzerindeki etkisi analiz edilerek, grafik ve resimlerle açıklanmıştır. Kaplamasız, TiN ve TiAlN kaplı karbür matkaplar kullanılarak kuru kesme şartlarında CNC dik işleme merkezinde talaş kaldırılmıştır. Kesme parametreleri olarak dört farklı kesme hızı 10, 12,5, 15, 17,5 m/min ve üç farklı ilerleme 0,05, 0,075, 0,1 mm/rev kullanılmıştır. Bu kesme parametreleri kullanılarak 5 mm çapında matkaplarla 8 mm derinliğinde kör delikler delinmiştir. Kesme kuvvetleri, yüzey pürüzlülüğü, delik çap ve dairesellikleri ölçülmüş ve bu ölçümler ışığında kesici takımlar arasında mukayese yoluyla bir değerlendirme yapılmıştır. Inconel 718'in kuru kesme şartlarında delinmesinde en iyi performans kaplamasız takımlardan alınırken en kötü sonuçlar ise TiAlN kaplı takımlardan alınmıştır. Yüksek kesme hızı ve ilerleme kombinasyonlarında takım performansı ve delik kalitesinin düştüğü görülmüştür.The aim of this study is to determine optimum drilling conditions for Inconel 718 drillability under dry cutting conditions. For this purpose when drilling Inconel 718 with coated and uncoated drills cutting parameters have been explained with graphics and pictures by analizing their effects on cutting forces, surface roughness, hole quality and chip formation. Drilling operation were performed on a CNC vertical machining center using uncoated, TiN and TiAlN coated carbide drills in dry cutting conditions. As a cutting paramaters, four cutting speeds (10, 12.5, 15, 17.5 m/min) and three different feed rates (0.05, 0.075, 0.1 mm/rev) have been used. Blind holes having 8 mm depth were drilled with 5 mm drills using this cutting parameters. Cutting forces, surface roughness, hole diameter and ovalibility were measured and the evaluated. By comparing the cutting tools according to these measurement. The best performance was obtained from uncoated cutting tools when drilling Inconel 718 under dry cutting conditions. On the other hand, the worst results were reached from TiAlN coated cutting tools. It was observed that cutting tools performance and hole quality decreased in the combinations of high cutting speed and feed rate

Effects of hybrid nanofluids on machining performance in MQL-milling of Inconel X-750 superalloy

Friction and high temperatures greatly affect machining efficiency when machining superalloy materials. Nanoparticles with high thermal conductivity and lubricity are preferred for increase lubricant performance. Nanofluids prepared with nanoparticles not only reduce environmental concerns but also positively affect the machining efficiency in the sustainable manufacturing process. However, some nanoparticles added in mono form stand out with their thermal conductivity and some nanoparticles with their lubricating performance. For this reason, the lubrication performance of hybrid nanofluids prepared with nanoparticles with different superior properties is a matter of interest. In this study, the machining performance of Inconel X-750 superalloy was investigated by using hexagonal boron nitride (hBN), graphite (Grpt), and MoS2 nanoparticles with different shapes and properties. For this purpose, the milling experiments were performed under three different hybrid nanofluid (hBN/Grpt, hBN/MoS2, and Grpt/MoS2) conditions, at three different cutting speeds (30, 45, and 60 m/min), and three different feed rates (0.05, 0.10, and 0.15 mm/rev). Cutting force, cutting temperature, surface roughness/topography, tool wear, and tool life were selected as machining performance criteria. According to the results obtained from the experiments, it was understood that the hBN/Grpt hybrid nanofluid outperformed hBN/MoS2 and Grpt/MoS2 conditions in all performance criteria. hBN/Grpt hybrid nanofluid achieved 36.17% and 6.08% improvement in tool life compared to Grpt/MoS2 and hBN/MoS2 nanofluids, respectively.Duzce University (Turkey) Research FundDuzce University [2017.07.04.593]The authors wish to thank the Duzce University (Turkey) Research Fund for their financial support of this experimental study (Project Number: 2017.07.04.593).WOS:0006963269000062-s2.0-8511410550

EFFECT OF CRYOGENIC TREATMENT APPLIED TO M42 HSS DRILLS ON THE MACHINABILITY OF Ti-6Al-4V ALLOY

This study investigated the effects of deep cryogenic treatment applied to M42 HSS drills on the tool wear, the tool life and the surface roughness during the drilling of a Ti-6Al-4V alloy under dry and wet cutting conditions. Drilling tests were carried out using untreated, cryogenically treated, cryogenically treated and tempered, and multi-layered TiAlN/TiN-coated HSS drills. Four different cutting speeds ((6, 8, 10, 12) m/min) and a constant feed rate of 0.06 mm/r were used as the cutting parameters and holes with a depth of 15 mm were drilled. At the end of the drilling tests, it was seen that the use of a coolant increased the tool life and decreased the surface roughness. Among the four tools, the best results in terms of the tool life and surface roughness were obtained with the multi-layered TiAlN/TiN-coated tool. The cryogenically treated and tempered drills exhibited an increase of 87 \% in the tool life compared to the untreated drills. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses showed that by reducing the size of the carbide particles in the microstructure, cryogenic treatment resulted in a more uniform carbide distribution and in the transformation of retained austenite to martensite. This played an important role in the increase in the hardness and wear resistance of the cutting tools

Evaluation of The Effects of Cutting Parameters On The Surface Roughness During The Turning of Hadfield Steel With Response Surface Methodology

Hadfield steel (X120Mn12) is widely used in the engineering applications due to its excellent wear resistance. In this study, the effects of the cutting parameters on the surface roughness were investigated in relation to the lathe process carried out on Hadfield steel. The experiments were conducted at a cutting speed of 80, 110, 140 m/min, feed rate of 0.2, 0.3, 0.4 mm/rev and depth of cut 0.2, 0.4, 0.6 mm, using coated carbide tools. Regarding the evaluation of the machinability of Hadfield steel, a model was formed utilizing the response surface method (RSM). For the determination of the effects of the cutting parameters on the surface roughness, the central composite design (CCD) and variance analysis (ANOVA) were used. By means of the model formed as a result of the experimental study, it was demonstrated that among the cutting parameters, the feed rate is the most effective parameter on the surface roughness, with a contribution ratio of 90.28%. It was determined that the surface roughness increases with increasing feed rate. With respect to the effect on the surface roughness, the feed rate was followed by the cutting speed with a contribution ratio of 3.1% and the cutting depth with a contribution ratio of 1.7%

Effects of mono/hybrid nanofluid strategies and surfactants on machining performance in the drilling of Hastelloy X

This study examined the effects of dry, base fluid, mono and hybrid nanofluid cooling/lubrication conditions on machining performance in drilling of nickel based Hastelloy X superalloys. Nanofluids were prepared by adding 0.6 vol% graphene nanoplatelets (GNP) and/or hexagonal boron nitride (hBN) with or without addition of 0.25 wt% sodium dodecyl sulfate (SDS) and/or gum arabic (GA) as surfactants into the cutting lubricant. Drilling experiment were performed at two different cutting speeds (20 and 30 m/min), two different feed rates (0.04 and 0.06 mm/rev) and a constant drilling depth (13.5 mm). Cutting force, hole quality (surface roughness and de-viations in diameter, circularity and cylindricity), cutting temperature, burr height, tool wear and tool life were selected as the performance criteria. The best results with regard to cutting force, hole quality, burr height, and tool wear were obtained under SDS added hBN/GNP hybrid cutting, whereas the best results for cutting tem-perature were achieved under hBN/GNP hybrid cutting condition without surfactants. In terms of tool wear, after 10 holes under dry cutting, flank wear on the drill was measured as 0.281 mm, whereas after 60 holes under hBN/GNP-SDS cutting condition, it was measured as 0.135 mm. This indicated a 51.96% improvement in tool wear compared to dry cutting. Among the mono nanofluids, the hBN-SDS cutting condition delivered the best performance, whereas among the hybrid nanofluids, the hBN/GNP-SDS cutting performed the best. Finally, evaluation of the surfactants added to the nanofluids revealed that SDS surpassed GA in terms of machining performance.Erciyes University Research FundErciyes University [FBA-2019-8834]The authors would like to thank the Erciyes University Research Fund for their financial support of this study (FBA-2019-8834).WOS:0006318431000012-s2.0-8510025169