Estimation of specific cutting energy in an S235 alloy for multi-directional ultrasonic vibration-assisted machining using the Finite Element Method

The objective of this work is to analyze the influence of the vibration-assisted turning process on the machinability of S235 carbon steel. During the experiments using this vibrational machining process, the vibrational amplitude and frequency of the cutting tool were adjusted to drive the tool tip in an elliptical or linear motion in the feed direction. Furthermore, a finite element analysis was deployed to investigate the mechanical response for different vibration-assisted cutting conditions. The results show how the specific cutting energy and the material’s machinability behave when using different operational cutting parameters, such as vibration frequency and tool tip motion in the x-axis, y-axis, and elliptical (x-y plane) motion. Then, the specific cutting energy and material’s machinability are compared with a conventional turning process, which helps to validate the finite element method (FEM) for the vibration-assisted process. As a result of the operating parameters used, the vibration-assisted machining process leads to a machinability improvement of up to 18% in S235 carbon steel. In particular, higher vibration frequencies were shown to increase the material’s machinability due to the specific cutting energy decrease. Therefore, the finite element method can be used to predict the vibration-assisted cutting and the specific cutting energy, based on predefined cutting parameters.Peer ReviewedPostprint (published version

An Experimental Investigation of Hot Machining with Induction to Improve Ti-5553 Machinability

The manufacturing of aeronautic parts with high mechanical properties requires the use of high performance materials. That’s why; new materials are used for landing gears such as the titanium alloy Ti-5553. The machining of this material leads to high cutting forces and temperatures, and poor machinability which requires the use of low cutting conditions. In order to increase the productivity rate, one solution could be to raise the workpiece initial temperature. Assisted hot machining consists in heating the workpiece material before the material removal takes place, in order to weaken the material mechanical properties, and thus reducing at least the cutting forces. First, a bibliography review has been done in order to determine all heating instruments used and the thermal alleviation that exists on conventional materials. An induction assisted hot machining was chosen and a system capable to maintain a constant temperature into the workpiece during machining (turning) was designed. Trails permit to identify the variation of cutting forces according to the initial temperature of the workpiece, with fixed cutting conditions according to the TMP (Tool-Material-Pair) methodology at ambient temperature. Tool life and deterioration mode are identified notably. The results analysis shows a low reduction of specific cutting forces for a temperature area compatible with industrial process. The reduction is more important at elevated temperature. However, it has consequences on quality of the workpiece surface and tool wear

The influence of laser assistance on the machinability of the titanium alloy Ti555-3

The Ti533-3 alloy is a new titanium alloy which is starting to see increased use in the aeronautical domain to improve the durability of components and to optimize the weight/resistance ratio. This alloy is characterized by greater resistance compared to the more commonly used titanium alloys such as Ti6Al4V. However, a disadvantage of the Ti533-3 alloy is that it is very difficult to machine. In this work, the use of laser-assisted machining has been tested to improve chip formation by a thermal softening phenomenon and to improve the machining productivity of the alloy. A parametric investigation of laser assistance on the machinability of the Ti555-3 titanium alloy shows that: (1) the cutting forces can be greatly decreased if the surface temperature is high; (2) the thermal gradient induced by laser heating modifies the surface integrity in terms of strain hardening and residual stresses in the workpiece; and (3) the chip formation mechanisms are also changed, by increasing the sawteeth frequency when using laser assistanc

Ultrasonic treatment with nickel electroplating combined with oxidation for developing γ-Al2O3 washcoat on Fe-Cr-Al substrate

Fe-Cr-Al is used as metallic support for catalytic converter due to its high thermal conductivity, lower heat capacity, high temperature and mechanical shock resistance. γ-Al2O3 is the most widely used material as washcoat which embedded on metallic support for the catalytic converter application. The problem is the coating adhesion between the metallic support and the ceramic washcoat becomes a problem in long�term high temperature oxidation. On the other hand, the gamma phase of alumina will be transformed to alpha phase at high temperature. The ultrasonic technique via cavitation bubbles and high velocity can make surface deformation and also accelerate the γ-Al2O3 powders to bombardment occurred on the Fe-Cr-Al surface. This process generates sufficiently heat and γ-Al2O3 layer can be formed on the Fe�Cr-Al surface. Subsequently, electroplating process embeds the nickel and also can strengthen the adhesion when oxidized. Therefore, this work presents the ultrasonic treatment with nickel electroplating for developing γ-Al2O3 washcoat on Fe-Cr-Al substrate and oxidation treatment for catalytic converter application. Washcoat layer on Fe-Cr-Al was prepared by using γ-Al2O3 powders through ultrasonic treatment. Catalyst material was prepared by using nickel electroplating. The oxidation kinetics was conducted at temperatures of 500, 700, 900 and 1100 oC in air for 100 hours. The surface morphology, cross section analysis, chemical composition, elemental maps and phase structure of coated Fe-Cr-Al were analyzed by Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) respectively. The results showed that the surface of Fe-Cr-Al contained γ-Al2O3 powders after ultrasonic treatment. The layer of alumina oxide has been formed on coated Fe-Cr-Al and no spallation occurred after oxidation. It is prove that γ-Al2O3 washcoat and NiO as a catalyst have successfully embedded on Fe-Cr-Al substrate by ultrasonic treatment combined with nickel electroplating at long term high temperature oxidation that enhance the adhesive properly

The relationships between nurse care, attitude of patient and nurse with cancer patient satisfaction

This study investigates the relationships between nurse care, attitude of patient and nurse with cancer patient satisfaction using the quantitative methodology. In Libya, the challenge of medical facilities and treatment is a current issue. Thus, this study was conducted to investigate the patients’ satisfaction at National Cancer Institute Misurata, Libya. The participants were 217 cancer patients of National Institute of Oncology located in Misurata, Libya. The study scale was adopted and adapted from that used by previous researchers to measure nurse care, nurse attitude, patient attitude, hospital service quality and patient satisfaction on a 5-point Likert scale. The nurse care, nurse attitude and patient attitude are independent variables and cancer patient satisfaction is the dependent variable in this study. On the other hand, hospital service quality and patient characteristic are control variables. SPSS software was used to analyses the data collected. The analyses of this study included descriptive statistic, correlation analysis and multiple regression analysis. The study found that on the overall basis, there is a significant statistical relationship between nurse care and cancer patient satisfaction, and there is a significant statistical relationship between attitude and cancer patient satisfaction. The sub-hypotheses show that there are no a relationship between interpersonal skills of nurse care and efficiency of nurse care with cancer patient satisfaction which suggest there might be interactions between these variables. Result also shows that for the sub-hypotheses, only patient attitude and cancer patient satisfaction indicated significant relationship, while there is no significant relationship between nurse attitude and patient satisfaction. This also indicates of possible interactions between the variables. On an overall basis, it can be concluded that to increase in the satisfaction level cancer patient, the management do it by focusing on improving the level of nurse care, nurse attitude and patient attitude

Elastic properties of superconducting MAX phases from first principles calculations

Using first-principles density functional calculations, a systematic study on the elastic properties for all known superconducting MAX phases (Nb2SC, Nb2SnC, Nb2AsC, Nb2InC, Mo2GaC and Ti2InC) was performed. As a result, the optimized lattice parameters, independent elastic constants, indicators of elastic anisotropy and brittle/ductile behavior as well as the so-called machinability indexis were calculated. We derived also bulk and shear moduli, Young's moduli, and Poisson's ratio for ideal polycrystalline MAX aggregates. The results obtained were discussed in comparison with available theoretical and experimental data and elastic parameters for other layered superconductors.Comment: 7 page

On the Machinability of an Al-63%SiC Metal Matrix Composite

This paper presents a preliminary study of aluminium matrix composite materials during machining, with a special focus on their behavior under conventional processes. This work will expand the knowledge of these materials, which is considered to be strategic for some industrial sectors, such as the aeronautics, electronics, and automotive sectors. Finding a machining model will allow us to define the necessary parameters when applying the materials to industry. As a previous step of the material and its machining, an experimental state-of-the-art review has been carried out, revealing a lack of studies about the composition and material properties, processes, tools, and recommended parameters. The results obtained and reflected in this paper are as follows; SiC is present in metallic matrix composite (MMC) materials in a very wide variety of sizes. A metallographic study of the material confirms the high percentage of reinforcement and very high microhardness values registered. During the machining process, tools present a very high level of wear in a very short amount of time, where chips are generated and arcs are segmented, revealing the high microhardness of the material, which is given by its high concentration of SiC. The chip shape is the same among other materials with a similar microhardness, such as Ti or its alloys. The forces registered in the machining process are quite di erent from conventional alloys and are more similar to the values of harder alloys, which is also the case for chip generation. The results coincide, in part, with previous studies and also give new insight into the behavior of this material, which does not conform to the assumptions for standard metallic materials, where the hypothesis of Sha er is not directly applicable. On the other hand, here, cutting forces do not behave in accordance with the traditional model. This paper will contribute to improve the knowledge of the Al-63%SiC MMC itself and the machining behavior

Electroplastic cutting influence on power consumption during drilling process

The aim of this study is to report the use of non-conventional material removal process technique. It was found that electropulses (EPs) assisted drilling process improves the material machinability based on the eletroplastic influence. The influence of EPs in drilling process is studied by combining different feed rates, drills diameters, and current densities in 7075 aluminium and 1045 carbon steel. The results show that the electrically assisted drilling process improves material machinability, decreases the specific cutting energy up to 27 % in aluminium and 17 % in steel.Peer ReviewedPreprin

Influence of cutting parameters and tool wear on the surface integrity of cobalt-based Stellite 6 alloy when machined under a dry cutting environment

The efficiency of a machining process can be measured by evaluating the quality of the machined surface and the tool wear rate. The research reported herein is mainly focused on the effect of cutting parameters and tool wear on the machined surface defects, surface roughness, deformation layer and residual stresses when dry milling Stellite 6, deposited by overlay on a carbon steel surface. The results showed that under the selected cutting conditions, abrasion, diffusion, peeling, chipping and breakage were the main tool wear mechanisms presented. Also the feed rate was the primary factor affecting the tool wear with an influence of 83%. With regard to the influence of cutting parameters on the surface roughness, the primary factors were feed rate and cutting speed with 57 and 38%, respectively. In addition, in general, as tool wear increased, the surface roughness increased and the deformation layer was found to be influenced more by the cutting parameters rather than the tool wear. Compressive residual stresses were observed in the un-machined surface, and when machining longer than 5 min, residual stress changed 100% from compression to tension. Finally, results showed that micro-crack initiation was the main mechanism for chip formation