Effect of electropulses on the machinability of a C45E steel

This article compares the machinability of a C45E (AISI/SAE 1045) steel type under two different manufacturing processes: conventional machining and pulsed current assisted machining. The testing procedure consisted on the dry turning, using a coated carbide cutting tool (HM) and high-speed steel (HSS) cutting tools, under two different spindle speeds. In this study cutting tool life is evaluated in function of cutting speed for both machining conditions and both cutting tools. Results show variation on flank wear depending on the tool used and cutting speed, showing an increase in machinability when using the HM tool with the electropulse assisted turning at low cutting speed. Additionally, changes in chip type are found when assisting the process with electropulses. Statistically significant variations in chip dimensions and chip ratio are present, evidencing the differences in the phenomena affecting shear strain. Surface roughness, for its part, is improved when turning with the assistance of electropulses.Peer ReviewedPostprint (published version

A navigation aid for the visually impaired

The explosion of new technologies in recent times has created many as yet unexplored possibilities in the area of assistive technology. Assistive technology may be thought of as any technology that alleviates the affects of an impairment, disability or handicap. One of the greatest challenges facing designers of assistive technologies is to accurately define the user requirements. The background research chapter of this report attempts to define the user requirements for a navigation aid that can be used any person, regardless of visual ability, both through literature surveys and through dialogue with potential end users. The conclusions drawn from this research are used as a basis for an investigation into possible technological solutions, culminating in a technical summary. Subsequently, the design and implementation of a software package capable of providing environmental information and navigational suggestions is discussed in the final chapters The package is designed to be flexible enough to act as a basis for further research and eventual implementation of a fully functioning navigation aid

Detection of biomarkers using DNA biosensors in a fluorescent platform to improve current one-step point-of-care methodologies

Current methodologies for patient diagnosis require the use of skilled workers, expensive reagents, and instrumentation, and most importantly, time. As these methodologies encourage inconsequential follow-up between patients and their doctors, new methods must be developed. These methods should follow the WHO guidelines of ASSURED (Accessible to those in need, Sensitive to the clinical range of the target of interest, Specific to the target of interest with no false positives or negatives, User-friendly, Rapid, under one hour for results, Equipment free, and Delivered to those in need) to create point of care technologies available for all. To this end, my studies focus on the development of convenient calibration methods for use with fluorescent, aptamer-based biosensors (aptamer beacons). Specifically, I describe here the creation, characterization, and application of a one-tube method for the calibration of aptamer beacons using sensors for the detection of DNA, silver ions, and thrombin as my test bed.A significant hurdle in the point of care testing of biomarkers in complex solutions is that there is sample variation, requiring large volumes of the target of interest and complex and cumbersome calibration. In response, I have created a simple, three-step, one-tube method for the calibration of aptamer beacons supporting the direct quantification of specific target molecules within complex sample matrices. Specifically, I have shown that the sequential addition of two inexpensive and stable oligonucleotide-based reagents allows for the determination of the absolute minimum and maximum fluorescence produced by the sensor in each solution, providing the information to calibrate in the face of sample-to-sample variations in a simple, single-tube format. Using the three associated measurements together with the pre-determined disassociation constant of the aptamer I demonstrate the single-tube calibrated quantification of multiple targets directly in complex samples

Mecanizado por arranque de viruta asistido por electropulsos

Este artículo trata sobre una nueva técnica de mecanizado: el proceso de torneado asistido in situ con corriente eléctrica, a través de la influencia de electropulsos. Un generador ha sido fabricado para inducir intensidades de corriente de 90 A, duraciones de pulso entre los 50 y 200 μs y frecuencias de descarga de 100 a 300 Hz. Se ha estudiado para acero 1045, la influencia de las diferentes configuraciones eléctricas que asisten el proceso de mecanizado respecto a las propiedades superficiales y el consumo de potencia eléctrica. Los resultados muestran que el proceso asistido mejora la mecanibilidad reduciéndose el consumo de potencia en 104 W y la energía especifica corte en un 22%. También modifica las propiedades superficiales, reduciendo la rugosidad media en un rango del 7 al 22% comparado con el proceso de torneado convencional

Corrosion behavior of an AISI/SAE steel cut by electropulsing

The effect of electropulsing treatment (EPT) on the surface general corrosion behavior of an AISI/SAE 1045 steel under different machining regimes is studied. In the study, the following variables are alternated: high-speed steel (HSS) vs. hard metal (HM), and with and without the assistance of high-density electropulses. The corrosion rates are determined using comparative studies such as gravimetric analysis, salt spray chamber test, electrochemical polarization curve techniques (PC), and linear polarization resistance (LPR). Differences in surface microhardness were evaluated by applying optical microscopy and planimetric procedures. Specimens subjected to electropulses and turned with HM reported greater reductions of corrosion rates. Changes in corrosion behavior can be explained in terms of grain shape factor h variation. The present study demonstrates that electropulsing affects the corrosion behavior of AISI/SAE 1045 steel after the turning process.Peer ReviewedPostprint (published version

Estudio de las variables que afectan la rugosidad superficial en el torneado de piezas esbeltas bajo retemblado

El mecanizado de piezas delgadas se encuentra influenciado por un fenómeno denominado retemblado, que afecta la calidad superficial. En este trabajo se presenta un estudio de los factores que influyen sobre la rugosidad superficial en un proceso de torneado de cilindros esbeltos bajo el efecto del fenómeno de retemblado. El propósito del estudio es determinar cuales son las variables del proceso que más influyen sobre la rugosidad superficial. Para ello se utiliza un modelo que permite predecir la topografía superficial en operaciones de torneado con retemblado. El modelo se encuentra en función de los parámetros de corte y las propiedades del material a mecanizar

Electropulsing effects on mechanical and metallurgical behavior of AISI-SAE 4140 steel

The electroplasticity phenomenon (EP) produces changes in the mechanical properties of a metal, due to the simultaneous application of mechanical stresses of compression, bending, etc., and high instantaneous current pulses. The changes produced on the plastic deformation rate by the EP are due to thermal effects (such as Joule effect) and other effects associated to the electric and magnetic fields. There are only a few studies that consider, as this paper does, the effects of electropulsing effect on tensile test processes in which the electron flow is esteemed as the main reason. In this paper, the results of a research on tensile test on specimen of AISI-SAE 4140, assisted by high-current-density electric pulses are presented. The aim is to evaluate the effect of these pulses on the microstructure and mechanical properties of metallic materials. The phase transformations and microstructural changes in the metallic specimens exposed to EP were analysed using Scanning Electron Microscopy (SEM), Diffraction Ray X (DRX) and Differential Scanning Calorimetry (DSC). Preliminary results show there are some differences in the material behaviour, between the specimens tensile tested with and without EP, such as: decreases values of yield and ultimate strength and XRD analyses attests to a slight displacement and intensity reduction of diffraction. Moreover, the application of current density in the order of 2.18 A/mm² is enough to produce changes in mechanical and metallographic properties of AISI/SAE 4140.Peer ReviewedPostprint (published version

Modelos para la predicción de la rugosidad superficial en procesos de mecanizado con arranque de viruta: revisión bibliográfica

El tema de la Rugosidad Superficial ha sido ampliamente estudiado por muchos autores, en busca de intentar predecir su comportamiento, así como definir los diferentes factores que la determinan. El presente artículo presenta una revisión de los diferentes enfoques usados para su predicción