Analysis of Secondary Adhesion Wear Mechanism on Hard Machining of Titanium Aerospace Alloy

Titanium alloys are widely used in important manufacturing sectors such as the aerospace industry, internal components of motor or biomechanical components, for the development of functional prostheses. The relationship between mechanical properties and weight and its excellent biocompatibility have positioned this material among the most demanded for specific applications. However, it is necessary to consider the low machinability as a disadvantage in the titanium alloys features. This fact is especially due to the low thermal conductivity, producing significant increases in the temperature of the contact area during the machining process. In this aspect, one of the main objectives of strategic industries is focused on the improvement of the efficiency and the increase of the service life of the elements involved in the machining of this alloy. With the aim to understand the most relevant effects in the machinability of the Ti6Al4V alloy, an analysis is required of different variables of the machining process like tool wear evolution, based on secondary adhesion mechanisms, and the relation between surface roughness of the work-pieces with the cutting parameters. In this research work, a study on the machinability of Ti6Al4V titanium alloy has been performed. For that purpose, in a horizontal turning process, the influence of cutting tool wear effects has been evaluated on the surface finish of the machined element. As a result, parametric behavior models for average roughness (Ra) have been determined as a function of the machining parameters used

Machining of Al-Cu and Al-Zn Alloys for Aeronautical Components

Machining operations are chosen by aircraft manufacturers worldwide to process light aluminum alloys. This type of materials presents good characteristics in terms of weight and physicochemical properties, which combined with a low cost ratio making them irreplaceable in aircraft elements with a high structural commitment. Conventional machining processes such as drilling, milling and turning are widely used for aeronautical parts manufacturing. High quality requirements are usually demanded for these kinds of components but aluminum alloys may present some machinability issues, basically associated to the heat generated during the process. Among others, surface quality and geometrical deviations are highly influenced by the condition of the cutting-tool, its wear and the cutting parameters. Consequently, the understanding of the relationship among the process parameters, the quality features and the main wear mechanism is a key factor for the improvement in the productivity. In this chapter, the fundamental issues of drilling, milling and turning are addressed, dealing with the relationship between cutting parameters, wear phenomena and micro and macro geometrical deviations

Detection mutations in the DNA mismatch repair genes of hMLH1 and hMSH2 genes in Colombian families with suspicion of hereditary non-polyposis colorectal carcinoma (Lynch syndrome)

Introducción. El cáncer colorrectal es la segunda causa de morbilidad y mortalidad por cáncer en los países desarrollados. En Colombia es la quinta causa de muerte entre los diferentes cánceres. Cerca del 75% de éstos corresponde a cánceres esporádicos, alrededor del 25% son familiares, y son claramente hereditarios el 5%. De éstos, el más importantes es el cáncer colorrectal no polipósico hereditario o síndrome de Lynch. Objetivo. Analizar los dos genes más importantes involucrados en el síndrome de Lynch, el hMLH1 y el hMSH2. Materiales y métodos. En 17 familias colombianas que cumplían con los criterios de Ámsterdam II o las pautas de Bethesda, se analizaron por SSCP los 35 exones de estos dos genes y las variantes electroforéticas se secuenciaron. Resultados. Se detectaron 8 mutaciones de línea germinal en las familias analizadas, 7 en el gen hMLH1 y 1 en hMSH2, y se encontró una tasa de detección de mutaciones del 47%. Seis de las 8 mutaciones encontradas en este estudio han sido previamente reportadas en la literatura. Un cambio de una base en el sitio donador de empalme en el exón 9 del gen hMLH1 (G>A) (dos familias), un cambio A>G en el codón 755 del exón 17, y un cambio G>A en el exón 18. Se detectaron dos nuevas mutaciones, una en el exón 17, un cambio C>T en el codón 640, y una deleción de TG en el codón 184 del exón 3 del gen hMSH2. También se detectó en dos familias un polimorfismo del intrón 13 del hMLH1. Conclusión. Este es el primer estudio realizado en Colombia que detecta mutaciones en el síndrome de Lynch y pretende establecer un programa integral de manejo y prevención.Introduction: Colorectal cancer (CRC) is the second highest cause of cancer mortality in developed countries. In Colombia, CRC ranks fifth as a cause of cancer death. Approximately 75% of CRC appear to be spontaneous and 25% are familial, with 5% of the latter clearly hereditary. Of these, hereditary non-polyposis colorectal carcinoma (HNPCC)-or Lynch syndrome is the most important.OBJECTIVE: Herein, the two most important genes involved in Lynch syndrome, the hMLH1 and hMSH2 were analyzed for presence of mutations.MATERIALS AND METHODS: Seventeen Colombian families that fulfilled the Amsterdam II criteria or Bethesda guidelines for Lynch syndrome were selected. The of 35 exons of hMLH1 and hMSH2 genes were screened by SSCP and those with electrophoretic variants were sequenced.RESULTS: Eight germinal mutations were detected, corresponding to a 47% detection mutation rate. Six of the eight mutations have previously been reported. These consisted of the following mutations: a single base substitution at the donor splicing site of exon 9, a single base substitution (A>G) at codon 755 of the exon 17, and another single base substitution (G>A) at codon 681 of exon 18. The two novel mutations consisted of a single base substitution (C>T) at codon 640 of exon 17 of the hMLH1 gene and a two-nucleotide deletion (TG) at codon 184 of exon 3 of hMSH2 gene. In addition, two families were observed with a polymorphism in the intron 13 (G>A) nt 1558+14, of hMLH1 gene.CONCLUSIONS: This study represented the first survey for detecting mutations associated with Lynch syndrome in Colombia, and is intended to lead to the establishment of a management and prevention program

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

Study of the Tool Wear Process in the Dry Turning of Al–Cu Alloy

Light alloy machining is a widely implemented process that is usually used in the presence of cutting fluids to reduce wear and increase tool life. The use of coolants during machining presents negative environmental impacts, which has increased interest in reducing and even eliminating their use. In order to obtain ecofriendly machining processes, it will be necessary to suppress the use of cutting fluids, in a trend called “dry machining”. This fact forces machines to work under aggressive cutting conditions, producing adhesion wear that affects the integrity of the parts’ surfaces. This study describes cutting tool wear mechanisms in machining of UNS A92024 samples under dry cutting conditions. Energy dispersive spectroscopy (EDS) analysis shows the different compositions of the adhered layers. Roughness is also positively affected by the change of the cutting geometry produced in the tool

Experimental Parametric Model for Adhesion Wear Measurements in the Dry Turning of an AA2024 Alloy

Adhesion wear is the main wear mechanism in the dry turning of aluminium alloys. This type of wear produces an adhesion of the machining material on the cutting tool, decreasing the final surface quality of the machining parts and making it more difficult to maintain industrial tolerances. This work studies the influence of the cutting parameters on the volume of material adhered to the cutting tool surface for dry machining of AA2024 (Al-Cu). For that purpose, a specific methodology based on the automatic image processing method that can obtain the area and the thickness of the adhered material has been designed. This methodology has been verified with the results obtained through 3D analysis techniques and compared with the adhered volume. The results provided experimental parametric models for this wear mechanism. These models are analytic approximations of experimental data. The feed rate mainly results in low cutting speed, while low depths of cut presents a different behaviour due to the low contact pressure. The unstable behaviour of aluminium adhesion on the cutting tool produces a high variability of results. This continuous change introduces variation in the process caused by the continuous change of the cutting tool geometry

Sliding Wear Behavior of UNS R56400 Titanium Alloy Samples Thermally Oxidized by Laser

Wear of elements subjected to friction and sliding is among the main causes of low tribological performance and short lifetime of strategic materials such as titanium alloys. These types of alloys are widely used in different areas such as aerospace and the biomechanics industry. In this sense, surface modification treatments allow for the overcoming of limitations and improvement of features and properties. In the case of titanium alloys, improvements in the main weaknesses of these materials can be obtained. Laser texturing of UNS R56400 (Ti6Al4V) alloy, according to Unified Numbering System designation, surface layers in a non-protective atmosphere produces an increase of the oxides, especially of titanium dioxide (TiO2) species. The presence of oxides in the alloy results in color tonality variations as well as hardness increases. In addition, specific roughness topographies may be produced by the track of laser beam irradiation. In this research, thermochemical oxidation of UNS R56400 alloy has been developed through laser texturing, using scan speed of the beam (Vs) as the process control variable, and its influence on the sliding wear behavior was analyzed. For this purpose, using pin on disc tribological tests, wear was evaluated from the friction coefficient, and wear mechanisms involved in the process were analyzed. Combined studies of wear mechanisms and the friction coefficient verified that by means of specific surface treatments, an increase in the wear resistance of this type of alloys is generated. The most advantageous results for the improvement of tribological behavior have been detected in textured surfaces using a Vs of 150 mm/s, resulting in a decrease in the friction coefficient values by approximately 20%

Effects of Laser Microtexturing on the Wetting Behavior of Ti6Al4V Alloy

Surface modification procedures by laser techniques allow the generation of specific topographies and microstructures that enable the adaptation of the external layers of materials for specific applications. In laser texturing processes, it is possible to maintain control over the microgeometry and dimensions of the surface pattern through varying the processing parameters. One of the main areas of interest in the field of surface modification treatments is the ability to generate topographies that are associated with specific surface finishes, in terms of roughness, that can improve the manufactured part’s functional capabilities. In this aspect, several types of phenomena have been detected, such as the friction and sliding wear behavior or wetting capacity, which maintain a high dependence on surface roughness. In this research, surface texturing treatments have been developed by laser techniques through using the scanning speed of the beam (Vs) as a control parameter in order to generate samples that have topographies with different natures. Through assessments of surface finish using specialized techniques, the dimensional and geometrical features of the texturized tracks have been characterized, analyzing their influence on the wetting behavior of the irradiated layer. In this way, more defined texturing grooves has been developed by increasing the Vs, which also improves the hydrophobic characteristics of the treated surface. However, due to the lack of uniformity in the solidification process of the irradiated area, some deviations from the expected trends and singular points can be observed. Using the contact angle method to evaluate the wetting behavior of the applied treatments found increases in the contact angle values for high texturing speeds, finding a maximum value of 65.59° for Vs = 200 mm/s

Detection mutations in the DNA mismatch repair genes of hMLH1 and hMSH2 genes in Colombian families with suspicion of hereditary non-polyposis colorectal carcinoma (Lynch syndrome)

Introducción. El cáncer colorrectal es la segunda causa de morbilidad y mortalidad por cáncer en los países desarrollados. En Colombia es la quinta causa de muerte entre los diferentes cánceres. Cerca del 75% de éstos corresponde a cánceres esporádicos, alrededor del 25% son familiares, y son claramente hereditarios el 5%. De éstos, el más importantes es el cáncer colorrectal no polipósico hereditario o síndrome de Lynch. Objetivo. Analizar los dos genes más importantes involucrados en el síndrome de Lynch, el hMLH1 y el hMSH2. Materiales y métodos. En 17 familias colombianas que cumplían con los criterios de Ámsterdam II o las pautas de Bethesda, se analizaron por SSCP los 35 exones de estos dos genes y las variantes electroforéticas se secuenciaron. Resultados. Se detectaron 8 mutaciones de línea germinal en las familias analizadas, 7 en el gen hMLH1 y 1 en hMSH2, y se encontró una tasa de detección de mutaciones del 47%. Seis de las 8 mutaciones encontradas en este estudio han sido previamente reportadas en la literatura. Un cambio de una base en el sitio donador de empalme en el exón 9 del gen hMLH1 (G>A) (dos familias), un cambio A>G en el codón 755 del exón 17, y un cambio G>A en el exón 18. Se detectaron dos nuevas mutaciones, una en el exón 17, un cambio C>T en el codón 640, y una deleción de TG en el codón 184 del exón 3 del gen hMSH2. También se detectó en dos familias un polimorfismo del intrón 13 del hMLH1. Conclusión. Este es el primer estudio realizado en Colombia que detecta mutaciones en el síndrome de Lynch y pretende establecer un programa integral de manejo y prevención.Introduction: Colorectal cancer (CRC) is the second highest cause of cancer mortality in developed countries. In Colombia, CRC ranks fifth as a cause of cancer death. Approximately 75% of CRC appear to be spontaneous and 25% are familial, with 5% of the latter clearly hereditary. Of these, hereditary non-polyposis colorectal carcinoma (HNPCC)-or Lynch syndrome is the most important.OBJECTIVE: Herein, the two most important genes involved in Lynch syndrome, the hMLH1 and hMSH2 were analyzed for presence of mutations.MATERIALS AND METHODS: Seventeen Colombian families that fulfilled the Amsterdam II criteria or Bethesda guidelines for Lynch syndrome were selected. The of 35 exons of hMLH1 and hMSH2 genes were screened by SSCP and those with electrophoretic variants were sequenced.RESULTS: Eight germinal mutations were detected, corresponding to a 47% detection mutation rate. Six of the eight mutations have previously been reported. These consisted of the following mutations: a single base substitution at the donor splicing site of exon 9, a single base substitution (A>G) at codon 755 of the exon 17, and another single base substitution (G>A) at codon 681 of exon 18. The two novel mutations consisted of a single base substitution (C>T) at codon 640 of exon 17 of the hMLH1 gene and a two-nucleotide deletion (TG) at codon 184 of exon 3 of hMSH2 gene. In addition, two families were observed with a polymorphism in the intron 13 (G>A) nt 1558+14, of hMLH1 gene.CONCLUSIONS: This study represented the first survey for detecting mutations associated with Lynch syndrome in Colombia, and is intended to lead to the establishment of a management and prevention program