Search

During the machining of Ti-6Al-4V the changing deformation mechanisms produce a complex microstructure of segmented chips, which directly influenced tool-wear and process stability. Numerical simulation could give an insight into the physical phenomena involved in chip segmentation, but its accuracy is directly related to the reliability of the input parameters. In this work, therefore, three different flow stress law were evaluated coupled with a physical based ductile failure criterion, which depends on stress triaxiality and temperature. To this end, the flow stress laws were implemented in the finite element software AdvantEdge by programming user-defined subroutines. The resulting FEM models were compared with orthogonal cutting experimental tests (tubular/linear), analyzing different fundamental outputs (machining forces, temperatures in the workpiece and chip morphology). All the FEM models showed good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

The ploughing force related with action of edge radius is an important factor which influences flow stress, chip formation or surface integrity. Some fraction of the cutting forces are called parasitic (additional) forces and they do not contribute on chip formation process. These forces are usually assumed to be the cutting force (constant value) for zero feed. However, this effect is related with the edge radius. To improve force modelling prediction, a new mechanistic model to predict cutting force considering edge radius is presented. The model was developed for two cutting speeds and in a wide range of feeds for three edge radii. The model was validated with additional experimental tests, achieving relative errors lower than 3%. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to study by Finite Element Method (FEM) the hard turning of 42CrMoS4 steel. A numerical and experimental study was carried out to analyze the effect that cutting parameters have on cutting and feed forces, temperatures on the cutting zone, contact length and chip morphology. A flow stress model for the FEM model was developed by dynamic compression tests. Experimental tests were done to establish the accuracy of the FEM model, developed in DEFORM. The tendencies of both frameworks agreed in forces and temperatures. Greater differences were found for contact length and chip thickness predictions. [ABSTRACT FROM AUTHOR]

A new flow stress model is proposed to describe the behaviour of ferrite–pearlite steels based on microstructure properties, including the effect of high strains, strain rates and temperatures. The model introduces strain hardening as a function of the pearlite ratio, interlamellar spacing and ferrite grain size. A non-linear thermal softening, and the coupling between strain rate and temperature are also introduced. Tested on a 2D ALE model, predicted cutting forces, tool temperatures, chip thickness and tool wear results obtained good agreement when compared to orthogonal cutting tests of four ferrite–pearlite steels, covering a wide range of microstructure variants. [ABSTRACT FROM AUTHOR]

Describe las ansiedades de una niña de cinco años, a la hora de enfrentarse a la operación de corazón a la que iba a ser sometida y las dificultades para asumir la información acerca de lo que le iba a suceder. Se comentan los mecanismos de defensa que más utiliza, y su evolución psicológica hasta dos años después de la operación. Los autores son partidarios de una metodología individualizada, adaptada al funcionamiento mental del niño, en la práctica de la psicoprofilaxis quirúrgica.

Abstract A material database for JETHETE-M152 was developed applying a novel methodology for improving the precision of cutting forces. This approach defines a variable specific edge force depending on the feed rate and cutting edge geometry. Applying this methodology, accurate predictions could be obtained when using complex shape inserts with different micro-geometries or with feed rates lower than the cutting edge radius. These predictions showed an improvement compared to those of the strategy of keeping constant the specific edge coefficient. Furthermore, an orthogonal to oblique transformation technique was applied to predict the cutting forces in face and side milling. The results showed good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Abstract The machining of difficult-to-cut materials involves limitations leading to low productivity in conventional machining processes due to high cutting forces and tool wear rates. The ultrasonic assisted machining techniques have been reported to reduce these drawbacks significantly, enabling the increase of productivity when machining this kind of materials. In the case of the reductions on cutting forces and their control, they can lead to important improvements concerning achievable Material Removal Rates (MRR) on processes where the maximum cutting forces are limited due to part-tool deflections or the appearance of chatter vibrations. The present study analyses the cutting force reductions generated when ultrasonically assisted turning of Ti6Al4V. The obtained results were analyzed for identifying the most relevant parameters generating such force reductions. Finally, an empirical model was developed allowing the calculation of the cutting forces to be generated during ultrasonic assisted turning operations of Ti6Al4V. [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The guarantee of surface integrity has become a primary objective for researchers when analysing the reliability of machined aircraft aluminium alloy structural parts in high-speed machining. This work studies the effect of cutting speed on the surface integrity of face milled 7050-T7451 aluminium workpieces. First, 7050-T7451 aluminium workpieces were face milled under dry conditions using three cutting speeds (200, 800, 1400 m/min) at constant feed (0.20 mm/tooth) and depth of cut (1 mm). An indexable face milling cutter with a diameter of 50 mm with five uncoated inserts was used in the face milling tests. During the machining process, cutting forces were acquired employing a Kistler dynamometer in order to understand the influence of the mechanical load on the final surface quality. The surface roughness produced by the milling process was measured using a portable rugosimeter. The residual stresses generated by the cutting process were measured by the hole-drilling technique. In addition, small specimens were cut out from the workpieces and microstructural alterations of the surface layer were analysed employing optical microscopy techniques. The results demonstrate that the magnitude of residual stresses and the thickness of the affected layer is sensitive to the cutting speed, while surface roughness and microstructural defects do not show significant variations for the tested conditions. [ABSTRACT FROM AUTHOR]

The performance of aeronautic critical components is strongly dependent on its fatigue behavior, which is directly linked to their surface integrity condition. Broaching operation is a machining operation extensively used for the manufacturing of some features due to the good dimensional quality and surface integrity condition obtained. Thus, the characteristics of surface integrity obtained in broaching is a key aspect to be considered for the improvement of the fatigue life. This work proposes a Finite Element Method (FEM) model for the prediction of the surface integrity (material damage and residual stresses) of the workpiece obtained after the broaching process using the commercial finite element software DEFORM 2D. The model includes a self-characterized Johnson-Cook flow stress constitutive law for the titanium alloy Ti64. Experimental tests were carried out in an EKIN RAS 10x160x320 hydraulic broaching machine at different cutting conditions for the validation of the predictive model. Apart from the fundamental output variables, such as, forces and chip morphology, a comprehensive study of the surface integrity of the machined piece was done. The residual stresses generated by the cutting process were measured by the hole-drilling technique. Microstructural alterations (material damage) of the workpiece was analyzed by optical microscopy and Scanning Electron Microscope. Finally, the surface topography was examined by contact and optical profilometers. The results of the predictions showed significant good agreement with the experimental tests. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study was to use individual-level data to examine the relationship between e-cigarette minimum legal sale age (MLSA) laws and cigarette smoking among U.S. adolescents, adjusting for e-cigarette use. Methods In 2016 and 2017, we regressed (logistic) current (past 30-day) cigarette smoking (from 2009–2014 National Youth Tobacco Surveys [NYTS]) on lagged (laws enacted each year counted for the following year) and unlagged (laws enacted January–June counted for that year) state e-cigarette MLSA laws prohibiting sales to youth aged <18 or <19 years (depending on the state). Models were adjusted for year and individual- (e-cigarette and other tobacco use, sex, race/ethnicity, and age) and state-level (smoke-free laws, cigarette taxes, medical marijuana legalization, income, and unemployment) covariates. Results Cigarette smoking was not significantly associated with lagged MLSA laws after adjusting for year (odds ratio [OR] = .87, 95% confidence interval [CI]: .73–1.03; p  = .10) and covariates (OR = .85, .69–1.03; p  = .10). Unlagged laws were significantly and negatively associated with cigarette smoking (OR = .84, .71–.98, p  = .02), but not after adjusting for covariates (OR = .84, .70–1.01, p  = .07). E-cigarette and other tobacco use, sex, race/ethnicity, age, and smoke-free laws were associated with cigarette smoking ( p  <   .05). Results unadjusted for e-cigarette use and other tobacco use yielded a significant negative association between e-cigarette MLSA laws and cigarette smoking (lagged: OR = .78, .64–.93, p  = .01; unlagged: OR = .80, .68–.95, p  = .01). Conclusions After adjusting for covariates, state e-cigarette MLSA laws did not affect youth cigarette smoking. Unadjusted for e-cigarette and other tobacco use, these laws were associated with lower cigarette smoking. [ABSTRACT FROM AUTHOR]

With the increase in performance of machining operations, noise levels have become an occupational health and safety problems. Identification of the main sources of noise emission when milling an aluminium component was analyzed. A machining centre, equipped with microphones, was installed in an anechoic chamber. Testing demonstrated that the part's stiffness is the most critical parameter. Cutting speed, feed and axial depth of cut tend to increase sound pressure level by increasing the impact energy, whereas radial depth of cut is not a sensitive parameter. Moreover the diameter of mills, as well as their unbalance, should be limited. [ABSTRACT FROM AUTHOR]

Copyright of InfoDesign: Revista Brasileira de Design da Informação is the property of Infodesign: Revista Brasileira de Design da Informacao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper reviews recent advances in constitutive and friction data and models for simulation of metal machining. Phenomenological and physically-based constitutive models commonly used in machining simulations are presented and discussed. Other topics include experimental techniques for acquiring data necessary to identify the constitutive model parameters, and recent advances in modelling of tool-workpiece friction and experimental techniques to acquire friction data under machining conditions. Additionally, thermo-physical properties for thermal modelling of the machining process, and microstructure data for the chip and workpiece together with relevant experimental methods are discussed. Future research needs in each of the focused areas are highlighted. [ABSTRACT FROM AUTHOR]

Purpose To analyse the variations of the renal arteries in two samples, cadaveric and computerized tomographic (CT) images, as well as to propose a simple classification of such variations based on the obtained results and an extensive review of the literature on the topic. Material and methods Sixty human dissected kidneys and their vessels, and 583 abdominal CT were studied. Results A total of 86 arteries were described in the cadaveric sample, whereas 1223 were analysed in the radiological one. Five types (a–e) and patterns (I–V) have been stablished in the classification. Type a, aortic hilar artery, incidences were 79% in cadavers and 95% in CT; Type b, hilar upper polar artery, incidences were 10% in cadavers and 2% in CT; Type c, aortic upper polar artery, incidences were 5% in cadavers and 2% in CT; Type d, aortic lower polar artery, incidences were 3% in cadavers and 1% in CT; Type e, hilar lower polar artery, incidences were 2% in cadaver and less than 0.1% in CT. The pattern represents the number of arteries reaching one kidney. Patterns I–IV were found in cadavers (I: 78%; II: 19%; III and IV: 2%); in CT sample only patterns I (88%) and II (12%). Pattern V was added because it has been described in the reviewed literature. Conclusions Type a and pattern I are the most prevalent, both in the cadaveric and the CT samples. Also in the consulted literature. There are no differences in the types and pattern incidences by side or sex. A simple, comprehensive and useful classification is proposed. [ABSTRACT FROM AUTHOR]

Broaching is a specific process characterized by relatively low cutting speeds and uncut chip thicknesses. The latter is in the range of 0.1 to 0.25 mm in the roughing section of the tool but can decrease down to 0.0015 mm in the finishing one. This induces drastically different cutting behaviours compared to macroscale processes such as turning. The question of the scale effects in such conditions is thus clearly raising and especially the size and distribution of the microstructure. This paper proposes an investigation to assess the importance of the material heterogeneities on chip formation when broaching ferritic-pearlitic steels. [ABSTRACT FROM AUTHOR]

A coupled Eulerian-Lagrangian Finite Element model of the orthogonal cutting process was developed to predict the influence that ferrite-pearlite steel variants have on fundamental process variables and tool wear. As a case study, this paper is focused on two different ferrite-pearlite inclusion free alloys, where mainly the influence of ferrite-pearlite ratio was tested. Flow stress behavior based on dynamic compression tests and thermal properties function of temperature were characterized for model input parameters. The numerical model is compared with orthogonal cutting tests where the cutting and feed forces, tool temperature, chip morphology and tool wear related variables were measured. Globally, predicted tendencies match with experiments in forces and temperatures. Widest differences on predictions were found for chip thickness and tool-chip contact length. Predicted wear rates are in accordance to experimentally measured values. [ABSTRACT FROM AUTHOR]

The finite element approach is often adopted to study the machining process. The Lagrangian and Eulerian formulations or even Arbitrary Eulerian-Lagrangian (ALE), one of their combinations, are the most employed in the current literature; each having their pros and cons. One of the most challenging issue in finite element modelling is the large strains during the cutting process that induce high deformation levels in the elements of the mesh. Remeshing contributes to decreasing mesh deformation but the criterion adopted to control it influences the results. The Coupled Eulerian-Lagrangian (CEL) method proposes to combine the Lagrangian and Eulerian formalisms without any element deformation problem. This paper studies its implementation in Ti6Al4 V orthogonal cutting. The results are then compared to an experimental reference, as well as more standard models: an ALE model developed with Abaqus, an implicit Lagrangian model developed with Deform and an explicit Lagrangian model developed with AdvantEdge. The comparison is mainly based on the cutting forces and the chip morphology. It shows that the CEL formulation is a competitive alternative to the more standard models. [ABSTRACT FROM AUTHOR]

Endocrine disrupting chemicals (EDC’s) disturb the endocrine system functionality causing negative effects on health in an organism and its progeny. Many studies have reported presence of potential EDC’s in wastewater and groundwater, indoor and outdoor air, agricultural soils and food. Epidemiological studies suggest that endocrine disruptors are associated to many worldwide increasing human diseases such as obesity, reproductive abnormalities, cancer, metabolic disorders, cardiovascular risk, autism, and epigenetic alterations. Effective technological advances for removal of endocrine disruptors in aqueous systems, food matrixes and airborne systems include aeration, ultraviolet irradiation, oxidation, chlorination, coagulation, filtration, biodegradation and membrane technology. However, they still require high investments and operational costs. On the other hand, low-cost cellulose-based materials can be designed for the removal of EDC’s via adsorption. Cellulose is the most abundant natural biopolymer, and it can be obtained directly from agricultural wastes, chemically modified and blended with other polymers or manufactured at nano-scale. This review aims to summarize the most relevant cases where cellulose-based materials have successfully removed EDC’s from its environmental matrixes, including technological opportunities foreseen within two categories: native and modified cellulose materials. [ABSTRACT FROM AUTHOR]

This paper analyzes the effect of tool wear on residual stresses when turning. Inconel 718 discs were machined for prolonged periods at several cutting speeds, feed-rates and depth of cut. Tests were interrupted to measure and relate tool wear with the subsequent residual stress measurements. The discussion of experimental results is supported by orthogonal cutting simulations. It was found a critical tool wear where tensile surface residual stresses were maximum, decreasing for lower and higher values of tool wear. Nevertheless, it was observed that the compressive residual stress layer increased with increasing tool wear. [ABSTRACT FROM AUTHOR]

Cryogenic machining together with minimum quantity lubrication (MQL), is claimed to be a promising alternative to flood cooling in industrial applications since it avoids the use of large amounts of cutting fluids and it improves the functional performance of machined components through its superior surface integrity characteristics. In this paper, the suitability of replacing conventional cutting fluids by liquid nitrogen cooling + MQL for finishing operations in industry will be discussed. Turning operations have been carried out on Inconel 718, in finishing conditions similar to those utilized in industry for the machining of nickel-based superalloys. With both cooling/lubricating approaches, the coolant has been applied to the rake face of the tool. Tool wear and surface integrity in terms of surface roughness, microstructural damage and microhardness profile have been analysed. The results show that conventional cooling is the best option from both the machinability and the surface integrity point of view. [ABSTRACT FROM AUTHOR]

In [25] Priest developed the da Costa logic ( daC ); this is a paraconsistent logic which is also a co-intuitionistic logic that contains the logic C ω . Due to its interesting properties it has been studied by Castiglioni, Ertola and Ferguson, and some remarkable results about it and its extensions are shown in [8,11] . In the present article we continue the study of daC , we prove that a restricted Hilbert system for daC , named DC , satisfies certain properties that help us show that this logic is not a maximal paraconsistent system. We also study an extension of daC called P H 1 and we give different characterizations of it. Finally we compare daC and P H 1 with several paraconsistent logics. [ABSTRACT FROM AUTHOR]

Copyright of Ingenium is the property of Facultad de Ciencias Basicas e Ingenieria de Universidad de San Buenaventura, Revista Ingenium and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Electrónica Interuniversitaria De Formación del Profesorado is the property of Asociacion Universitaria de Formacion del Profesorado (AUFOP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tool life is usually measured by end tool life tests, however, such experiments are costly and time consuming. Establishing correlation between these tests and shorter and cheaper tests is consequently of great interest. Experimental results from dry orthogonal cutting tests are reported and a good correlation between temperature reached at the tool and tool life test is shown. [ABSTRACT FROM AUTHOR]

Background: The early detection of Alzheimer disease is currently one of the main worldwide scientific goals. Estructural biomarkers, such as cortical deterioration and medial temporal lobe atrophy (MTLa), are well known and deeply studied. The relation of these structural changes with brain connectivity could help to understand the consequences of neurodegeneration in brain functioning, with the ultimate goal of explaining cognitive impairment. Magnetoencephalogram (MEG) quantitative analysis is a precise, non‐invasive tool to evaluate changes in bioelectrical activity of the brain. Therefore, it brings us the opportunity to study disruption of functional brain networks associated with changes in MTLa volume, as assessed with structural MRI. Method: We recruited 376 healthy elders and 130 mild cognitive impairment patients (MCI) (aged from 61 to 85) from the “Hospital Universitario San Carlos” and the Center for elders at the Chamartín District, all located in Madrid, Spain. All of them underwent a neuropsychological evaluation, MRI assessment, and MEG recordings. The MCI diagnosis was established according to the NIA‐AA criteria. None of the participants exhibited a history of psychiatric or neurological disorders (other than MCI). We used a completely data‐driven approach to evaluate the relationship between functional connectivity (FC) and the hippocampal volume. Result: Our main finding was an augmented theta band functional connectivity (FC) in right temporal (RTemp) areas associated with lower hippocampal volume, and we found this FC signature to correlate negatively with memory performance. Furthermore, the average theta FC of this area differed significantly between groups, although the original relationship remained significant for each group independently. Finally, we performed a seed‐based analysis targeting the original right temporal region and found that the modulation of the theta FC was driven by connections to 1) superior frontal and 2) contralateral temporal areas. Conclusion: The results depict a clear FC pattern that seems to be associated with both healthy and pathological aging. This MEG signature may be useful as a non‐invasive biomarker for the progressive subcortical degeneration that occurs along aging, both healthy and pathological. Furthermore, it is also related with cognitive performance, especially with memory functioning. [ABSTRACT FROM AUTHOR]

Copyright of Biomédica: Revista del Instituto Nacional de Salud is the property of Instituto Nacional de Salud of Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Resumen Antecedentes La tiña de la cabeza (tinea capitis) es la tiña más común en niños. El diagnóstico clínico se confirma con el estudio micológico, que incluye examen directo con hidróxido de potasio o negro de clorazol, así como el cultivo. Mediante dermatoscopia se ha descrito la presencia de pelos «en coma», «en sacacorchos» («tirabuzón»), además de pelos cortos y puntos negros. Objetivos Describir los patrones dermatoscópicos que se encuentran en la exploración tricoscópica en pacientes con diagnóstico de tiña de la cabeza. Métodos Estudio descriptivo, observacional y transversal. Se incluyeron 37 pacientes con diagnóstico de tiña de la cabeza, atendidos en el mes de mayo de 2012 en el Departamento de Dermatología del Hospital General Dr. Manuel Gea González, de México, y el Instituto Dermatológico y Cirugía de Piel Dr. Huberto Bogaert Díaz, de República Dominicana. Se llevó a cabo la evaluación clínica, micológica y dermatoscópica. Resultados Se evaluaron 37 pacientes, 28 mulatos de República Dominicana y 9 mestizos de México, con un 76% de varones y un 24% de mujeres. El 94% de los casos fueron niños. Se corroboró la presencia de los patrones dermatoscópicos ya descritos: pelos «en coma» (41%), «en sacacorchos» (22%), cortos (49%) y puntos negros (33%); además, se constató la presencia de escamas (89%), vainas peripilares (46%), alopecia (65%), pústulas (8%) y costras melicéricas (16%). Conclusiones El estudio dermatoscópico puede confirmar el diagnóstico de tiña de la cabeza, y complementa el estudio micológico, al encontrar pelos «en coma» y «en sacacorchos»; además, se observó la presencia de escamas, vainas peripilares y alopecia. Es deseable instaurar este método diagnóstico en lugares en los que no se cuente con un microscopio óptico o un laboratorio de micología de referencia. Background Tinea capitis is a common fungal infection in children. Diagnosis is confirmed by mycological study, including direct examination of the samples with potassium hydroxide/chlorazol black and culture. Previous studies have reported the presence of “comma hairs” and “corkscrew hairs”, as well as short hairs and black dots. Aims To describe the dermoscopic patterns in the trichoscopic examination in patients with tinea capitis. Methods A descriptive, observational and cross-sectional study was conducted on 37 patients with tinea capitis, studied during May, 2012, at Dr. Manuel Gea González General Hospital in Mexico, and the Instituto Dermatológico y Cirugía de Piel Dr. Huberto Bogaert Díaz, in the Dominican Republic. Clinical, mycological and dermoscopic evaluations were performed. Results Of the 37 patients included, 28 were of mixed race from Dominican Republic and 9 mixed race cases from Mexico. Seventy six percent were male and 24% female, and 94% were children. The following dermoscopic patterns were confirmed: “comma hairs” (41%), “corkscrew hairs” (22%), short hairs (49%), and black dots (33%). The presence of scales (89%), peripilar casts (46%), alopecia (65%), pustules (8%), and meliceric crusts (16%), were also observed. Conclusions Dermoscopy in tinea capitis showed the presence of “comma hairs”, and “corkscrew hairs”. Scales, peripilar casts and alopecia were also found. It would be desirable to establish this diagnostic tool, particularly when an optical microscope or a mycology reference laboratory are not available. [ABSTRACT FROM AUTHOR]

Ti6Al4 V is a titanium alloy widely used in the aeronautical industry and machining is often adopted to manufacture it. These parts must satisfy requirements specified by the customer. A crucial characteristic of aircraft machined parts is their reliability and, therefore, their fatigue life has to be mastered. In this context, the corresponding requirement concerns the surface integrity. This should be achieved by selecting adequate cutting parameters, which is actually not an immediate operation. The geometry of the tool will afterwards change during its life, what is more as Ti6Al4 V is known to be a hard-to-machine material. In this context, a finite element model is developed to highlight the influence of tool wear on fundamental variables like forces, temperatures, stresses,... and surface integrity (through plastic strains). The results should help to decide when it is time to replace the tool before altering the part and therefore not meet the specifications anymore. [ABSTRACT FROM AUTHOR]