Influence of the tool edge geometry on specific cutting energy at high-speed cutting

This paper presents specific cutting energy measurements as a function of the cutting speed and tool cutting edge geometry. The experimental work was carried out on a vertical CNC machining center with 7,500 rpm spindle rotation and 7.5 kW power. Hardened steels ASTM H13 (50 HRC) were machined at conventional cutting speed and high-speed cutting (HSC). TiN coated carbides with seven different geometries of chip breaker were applied on dry tests. A special milling tool holder with only one cutting edge was developed and the machining forces needed to calculate the specific cutting energy were recorded using a piezoelectric 4-component dynamometer. Workpiece roughness and chip formation process were also evaluated. The results showed that the specific cutting energy decreased 15.5% when cutting speed was increased up to 700%. An increase of 1 °in tool chip breaker chamfer angle lead to a reduction in the specific cutting energy about 13.7% and 28.6% when machining at HSC and conventional cutting speed respectively. Furthermore the workpiece roughness values evaluated in all test conditions were very low, closer to those of typical grinding operations (∼0.20 μm). Probable adiabatic shear occurred on chip segmentation at HSC Copyright © 2007 by ABCM.

Scanning electron microscope assessment of several resharpening techniques on the cutting edges of gracey curettes

Aim: Treatment of periodontal diseases is based on efficient scaling and root planing (SRP) and adequate maintenance of the patient. The effectiveness of SRP is influenced by operator skill, access to the subgingival area, root anatomy, and the quality and type of instrument used for SRP. The aim of this study was to evaluate the cutting edges of Gracey curettes after manufacturing and after resharpening using several techniques. Methods and Material: The cutting edges of a total of 41 new #5-6 stainless steel Gracey curettes were evaluated blindly using scanning electron microscopy (SEM). The quality of the cutting edges was evaluated blindly by a calibrated examiner using micrographs. Data were analyzed using a Kruskal Wallis test and nonparametric two-way multiple comparisons. Results and Conclusions: Different sharpening techniques had significantly different effects on the sharpeness of cutting edges (p<0.05). Sharpening by passing the lateral face of curettes over a sharpening stone and then a #299 Arkansas stone produced a high frequency of smooth, sharp edges or slightly irregular edges between the lateral and coronal faces of the curettes. Sharpening by passing a blunt stone over the curette's lateral face produced the poorest quality cutting edge (a bevel). Sharpening of the coronal curette face produced extremely irregular cutting edges and non-functional wire edges. Sharpening with rotary devices produced extremely irregular cutting edges.

Study of cutting forces on machinability properties of gray cast iron using new ceramics cutting tools

During gray cast iron cutting, the great rate of mechanical energy from cutting forces is converted into heat. Considerable heat is generated, principally in three areas: the shear zone, rake face and at the clearance side of the cutting edge. Excessive heat will cause undesirable high temperature in the tool which leads to softening of the tool and its accelerated wear and breakage. Nowadays the advanced ceramics are widely used in cutting tools. In this paper a composition special of Si3N4 was sintering, characterized, cut and ground to make SNGN120408 and applyed in machining gray cast iron with hardness equal 205 HB in dry cutting conditions by using digital controlled computer lathe. The tool performance was analysed in function of cutting forces, flank wear, temperature and roughness. Therefore metal removing process is carried out for three different cutting speeds (300 m/min, 600 m/min, and 800 m/min), while a cutting depth of 1 mm and a feed rate of 0.33 mm/rev are kept constant. As a result of the experiments, the lowest main cutting force, which depends on cutting speed, is obtained as 264 N at 600 m/min while the highest main cutting force is recorded as 294 N at 300 m/min.

Energia específica de corte e integridade superficial no microfresamento do ABNT 1045

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo dos mecanismos governantes do efeito de escala na microusinagem

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Artificial neural networks for machining processes surface roughness modeling

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Evaluation of the performance of α-SiAlON tool when turning Ti-6Al-4V alloy without coolant

Due to their high hardness and wear resistance, Si3N4 based ceramics are one of the most suitable cutting tool materials for machining cast iron, nickel alloys and hardened steels. However, their high degree of brittleness usually leads to inconsistent results and sudden catastrophic failures. This necessitates a process optimization when machining superalloys with Si3N4 based ceramic cutting tools. The tools are expected to withstand the heat and pressure developed when machining at higher cutting conditions because of their high hardness and melting point. This paper evaluates the performance of α-SiAlON tool in turning Ti-6Al-4V alloy at high cutting conditions, up to 250 m min-1, without coolant. Tool wear, failure modes and temperature were monitored to access the performance of the cutting tool. Test results showed that the performance of α-SiAl0N tool, in terms of tool life, at the cutting conditions investigated is relatively poor due probably to rapid notching and excessive chipping of the cutting edge. These facts are associated with adhesion and diffusion wear rate that tends to weaken the bond strength of the cutting tool.

Analysis on turning Ti-6Al-4V with different cooling methods

The aim of this paper is to optimize the machining of Ti-6Al-4V alloy, by studying the chip formation, roughness and tool wear for different cooling conditions. The results were compared between cooling methods, minimal quantity of fluid (MQF) and flooding, and also without fluid for the tool H13A. The turning of Ti-6Al-4V has shown good results on roughness (0, 8μm) and tool life, which was 11% lower with MQF than with the flooding method. The tool wear causes variation of the shear angle, which promotes strength hardening of the chip. As a result, the machined surface could be damaged. The use of the cutting fluid helps to save the cutting edge and could reduce the strength hardening. Nevertheless, it could also facilitate the formation of built-up edge. The nucleation of alpha lamellar colonies can occur due to a combination of deformation rates and temperature, mainly when the flooding is used, but it's not conclusive. The lamellar colonies were also found with the MQF in some regions, however, this structure did not show hardness variation compared to equiaxial. For all this reasons, the machining parameters might be carefully chosen.

Diálogos entre literatura e cinema: um estudo sobre The Dead de James Joyce

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo do uso de ferramentas cerâmicas na usinagem de inconel 718

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação do efeito da afiação com diferentes técnicas sobre o ângulo de corte de curetas de Gracey

Pós-graduação em Odontologia - FOAR

Ensaios não destrutivos: metrologia e calibração

To perform the quality control of various industries like: petrochemical, nuclear, aerospace, steel, shipbuilding, pulp and paper, and inspection of welded products, castings, forgings, rolled products, among others, used the method of Non-Destructive Testing (NDT). The method is based on the physical properties of the material, so selecting a procedure more appropriate. The company Inter-Metro Serviços Especiais Ltda., with its cutting-edge laboratory, dedicated to the implementation of calibration services and measurement equipment for industrial, medical, occupational safety and Non-Destructive Testing (NDT). It has a trained team, providing guidance and providing support for improving procedures for testing and measuring

XSOFT: estudo de reconhecimento, exploração e prevenção de vulnerabilidades de software através de uma distribuição LINUX

This work aims to give greater visibility to the issue of software security, due to people talk a lot in security conferences, that much of both IT (Information Technology) staff and, more specifically, IS (Information Security) staff does not know this, and, thanks to the spread of the mobile computing and of the cloud computing, this lack of deeper knowledge on this subject is increasingly becoming worrisome. It aims too, make applications to be developed in a security manner, priorizing the security of the information processed. It attempts to demonstrate the secure coding techniques, the principles of software security, the means to identify software vulnerabilities, the cutting-edge software exploitation techniques and the mechanisms of mitigation. Nowadays, the security guys are in charge of the most of the security tests in applications, audits and pentests, and it is undeniable that the so-called security experts, most often come from computer network field, having few experience in software development and programming. Therefore, the development process does not consider the security issue, thanks to the lack of knowledge on the subject by the developer, and the security tests could be improved whether security experts had a greater know-how on application development. Given this problem, the goal here is to integrate information security with software development, spreading out the process of secure software development. To achieve this, a Linux distribution with proof of concept applicati... (Complete abstract click electronic access below)

Usinagem da liga de níquel inconel 718 com pastilhas de cerâmica

The machining of super alloys resistant to high temperatures such as nickel alloys, inconel 718 specifically, is a very difficult job to obtain improvements in the process, due to the difficulty of machining at high cutting speeds, the use of these alloys in industries showed great developments in recent years, its application in aeronautical industry spread being used in vane turbo, compressor parts, props and set elements. The automotive, chemical, medical and others also took advantage of the great features of inconel 718 and has used the material. The high temperature resistant alloys have high machining difficulty, a fact that is associated with high cutting forces generated during machining which result in high temperatures. High levels of temperatures can cause deterioration of the cutting edge, with subsequent deformation or breakage, wear most common obtained in machining such materials are flank wear the formation of built-up edge for cutting and notch wear. The experimental part of the work consists in machining of nickel-based alloy Inconel 718 heat treated for hardness, using a tool based ceramic silicon nitride Sandvik (Si3N4) in order to compare the best results obtained in the master's thesis of SANTOS (2010) who used a tool ceramics also the basis of silicon nitride which was developed in the doctoral thesis of SOUZA (2005). Assays were performed on a CNC lathe and was noted for each cutting edge results obtained. Tests were made starting from an initial condition of the tool with cutting speed of 200 m/min, feed 0.5 mm and 0.5 mm depth of cut was reduced cutting speed for the subsequent tests with the same conditions of feed and depth of cut. The tool presented wear instant under two 200 m/min and 100 m/min, premature rupture of 50 m/min and finally cut provided with difficulty... (Complete abstract click electronic access below)

VT Preparado: AC/JC : a videoarte de Walter Silveira

Pós-graduação em Artes - IA