The flow behavior around a marine propeller with a counter-rotating propeller (CRP) is presented in this paper. Numerical tests were carried out on the INSEAN E779A model with a 1/9 scale rotating at different rotational speeds and advance coefficient. The turbulence phenomena have been modeled using the usual k-epsilon turbulence model, which features a fine mesh and prisms around the four blades of the 3D domain. The results of the simulations are compared with the measurements studied and available in the literature, as well as with the international standard (wake map). In order to reduce noise output, a CRP is used to reinforce the propeller structure, reduce energy waste and limit the tip vortex. It is also contrasted to a basic propeller. According to the results, CRP can increase propulsive efficiency by 50% at advance coefficient (J = 910) when compared to traditional configurations. This makes it a potential technology for contemporary marine engineering, especially in high-speed ships, submarines and naval vessels.

In this work, the structural, electronic, thermoelectric and thermodynamic behaviors of 18-valence-electron half-Heusler compounds VIrSn and VIrPb using density functional theory (DFT) with FP-LAPW approach, as implemented in WIEN2k are explored. The optimized structures confirm the stability of Type-II phase and calculated elastic constants reveal that both materials are ductile and anisotropic. To better capture relativistic and exchange-correlation effects, we have tested four levels of approximation; GGA, GGA-SOC, mBJ-GGA, and mBJ-GGA-SOC. For VIrSn, the gap remains indirect under all approximations. mBJ-GGA guides to increase it, while SOC causes a slight reduction. The modest valence band splitting at VBM (Delta soc approximate to 0.195 eV) indicates weak relativistic effects. For VIrPb, mBJ-GGA significantly enhances the gap, but SOC reduces it and under mBJ-GGA-SOC, transforms it from indirect to direct. A pronounced splitting at VBM (Delta soc approximate to 0.432 eV) reveals the stronger influence of SOC on its electronic structure. These changes modify the band curvature and increase the hole effective mass, which improves the Seebeck coefficient-especially for p-type conduction under mBJ-GGA-SOC. With ZT values close to 0.8 at 1200 K, VIrSn and VIrPb half-Heuslers demonstrate an exceptional high-temperature thermoelectric performance. SOC plays a crucial role in maximizing thermoelectric efficiency because it significantly improves electronic structure and p-type transport, while having little impact on structural and mechanical stability. These findings, along with a verified thermal robustness up to 1200 K and 25 Gpa to make VIrSn and VIrPb attractive options for high-performance thermoelectric devices of future.

ABSTRACT The structural, electrical, magnetic, and elastic characteristics of the Mn2OsSn full-Heusler compound have all been studied using the full potential linearised augmented plane (FP-LAPW) method. The study's exchange and correlation potentials are calculated using the generalised gradient approach (GGA) developed by Burke, Perdew, and Ernzerhof; the GGA with the Tran-Blaha-modified Becke–Johnson approximations; and the GGA with the correlated Hubbard parameter (GGA +U). Our calculations show that the formation energy of the compound is negative for the two-type structure, which means the crystal may persist indefinitely. Our chemical has a convex hull distance at 0 K for cubic regular and inverse-type structures, indicating that it will likely be synthesised via equilibrium processing. The electronic band structures, densities of states, and 100 spin-polarisation at the Fermi level in the typical cubic AlCu2Mn-type structure show Mn2OsSn in its complete Heusler ferromagnetic state has a half-metallic feature with an indirect band gap in the minority spin. Alternatively, in the CuHg2Ti-type ferromagnetic state, with its inverse cubic structure, this material exhibits metallic ferromagnetic behaviour with a polarisation of 96,325. The half metallicity of the AlCu2Mn-type combination is preserved at 1 GPa of hydrostatic pressure. Thus, Mn2OsSn, with the appropriate correction option for the Hubbard-Coulomb parameter U, will be a promising contender for spintronic applications.

Since their appearance, machining techniques have undergone multiple improvements. The processes of shaping materials by removing material have been constantly questioned in order to stay in step with industrial requirements, whatever economic or ecological. Today, the manufacturing engineer must therefore be able to answer a multitude of questions in order to quickly produce parts of the required quality and at low cost. Hard turning is a process that can be described as standard in a number of sectors such as the production of bearing steel 100Cr6 chrome with a hardness of 62 RC, but also turning auto parts steel chromium-manganese cemented hardened gears as 27MnCr5 a hardness of 62 RC. The technical and economic feasibility of machining parts such harshness was made possible thanks to the use of new tool materials with a very high hardness and high chemical stability at high temperatures, such as cubic boron nitride CBN, and with the arrival of new machine tools with significant stability and high precision. Hard turning allows today to produce high-quality surfaces from competing in many cases, operations traditionally reserved for rectification. High speed machining has also showed its competitiveness in applications such as turning parts for gearboxes and drivesystems in hardened materials. This article is a contribution to the study of the integrity of the machined surface in hard turning.

The rise in temperature during a machining process is due to a combined effect of the phenomena of dissipation of plastic energy in different zones of deformation and the phenomena of friction. Knowledge of the temperature in machining allows the development of new cutting tools (composition of the material of the tool, geometry, coating, etc.), the increase in tool life in order to reduce the cost of production industrial. In hard turning and by the very principles of cutting, which are quite different than for the usual turning of untreated materials, very high temperatures appear during work (between 500 degrees and 1500 degrees depending on the case) in the areas contact between cutting edge and workpiece. This leads to softening of the machined material in the areas of contact with the tool. The first factor is the thermal conductivity of the cutting material. For finishing work, a cutting material with low thermal conductivity is the first choice. The temperature during the cutting process is transferred to the shear zone, this which improves the cutting process.

The present work, constituted a theoretical study of the phenomenon of the electric conductivity of composite conducting polymers. Generally, the polymers are used as electrical insulators. The incorporation of conducting loads in an insulating polymeric matrix makes it possible to obtain materials having at the same time a high electric conductivity and a low density. These materials offer a great number of applications such as the electromagnetic shielding, the protection of metals against corrosion, the adhesives conducting, the connectors, the sensors, etc. The prediction and modelling of the electrical behaviour of these composite materials are needed for the choice of their scope and could therefore reduce the onerous experimental work and the cost of production through an optimized design. We carried out a theoretical study. To make this study, we are based on experimental results existing in the specialized literature and we build a new ideal model which describes the variation of electrical conductivity in function the voluminal fraction of the conducting loads. The comparison between our ideal model suggested and other models of McLachlan, Kirkpatrick and Landauer, shows that the model suggested is in concord with the experimental results.

Turning is one of the most widely used machining processes in the mechanical engineering industry. Thus, the choice of optimal cutting parameters (cutting speed, feed and depth of cut) is very important in order to ensure a better surface condition of the machined parts and the life of the cutting tools, which requires great relationship with the wear of the tool-part interface. The result of a good choice of cutting conditions can be seen by a reduction in this wear. During machining, the geometric shape and the physical state of the tool are modified by the combined action of the cutting forces and by the temperature reached by the cutting edge. These modifications which gradually increase with the duration of machining are commonly grouped under the term wear of the tool. They appear on the active part of the tool. In this work, we propose an optimization method allowing determining a mathematical model of the wear and tear by applying the experiment plan. This model highlights the relationship between the elements of the cutting regime (cutting speed, feed and depth of passes) and the responses studied (Wear in clearance).

First-principles calculations of structural, elastic, electronic and magnetic properties of full-Heusler Ir2HfB, Ir2HfAl and Ir2HfGa have been realized by full-potential linearized augmented plane wave (FP-LAPW) method implemented inWIEN2K code. The Perdew-Burke-Ernzerh of generalized gradient approximation (PBE-GGA) carried out the computation of different parameters to describe elastic and structural properties. The calculation of structural properties revealed that the three alloys are stable in cubic AlCu2Mn-type structure in ferromagnetic state. The elastic constants calculation shows the three alloys satisfy the stability criteria. Indeed, the calculated spin-polarized electronic band structure and density of states using generalized gradient approximation (GGA) show that Ir2HfZ (Z = B, Al, Ga) alloys have a metallic character. The influence of strong electronic correlation has been considered in GGA+Uand mBJ-GGA+U approximations that allows for improving the width of the band gap. The calculations carried out with GGA+U and mBJ-GGA+U show that Ir2HfAl and Ir2HfGa have a half -metallic behavior; however, Ir2HfB has a near half-metallic character. The calculated magnetic moments of Ir2HfB, Ir2HfAl and Ir2HfGa in a regular cubic structure with GGA+U and mBJ-GGA+U equal 1 mu B. With mBJ- GGA+U, the spin polarization values are 100% for Ir2HfAl, Ir2HfGa and 99.90% for Ir2HfBto be applicable for spintronics.

The wear of cutting tools is one of the main current problems, especially when it comes to new materials called "difficult to machine" or with high added value. Tool wear is caused by extreme thermomechanical loads applied to the contact areas of tool chips and tool parts. During milling, turning or drilling operations, for example, large deformations, high deformation rates and high temperatures can be observed near the surface of the cutting tool. The objective of our work is to respond to the problem of abrasion wear by developing a predictive tool, based on knowledge of the physical and tribological mechanisms of workpiece-tool contacts, allowing us to quantitatively estimate the wear of the tool and its service life. To achieve this, we base our approach on previous studies carried out in the field of machining and metalworking. The modeling work was first applied to the wear case, then extended to the study of the crater wear occurring on the cutting face. By taking into account the mechanical load applied and the geometry of the contacts involved (plane-plane contacts), we have developed a two-dimensional approach in orthogonal cut configuration.

An automobile brake disc brought into contact with the pads, mechanical stresses are imposed on the contact surface. These stresses can cause degradation by fatigue, rupture, wear, propagation of cracks. Modeling the numerical results makes it possible to recognize this damage in order to improve the braking system, extend its service life, reduce the cost of maintenance and make it more reliable. The aim of our study concerns modeling and numerical simulation using ANSYS 14.5 software based on the finite element method under the influence of certain essential parameters on the braking behavior of the torque as a function of geometric parameters, properties mechanical, boundary conditions, type of loading applied, type of materials chosen and type of analysis carried out in braking torques (ventilated drilled disc / pads and ventilated grooved disc / pads), upon contact with a disc in rotation with a plate which represents the friction body on the disc. The behavior of the torque during braking was analyzed in terms of stresses and deformations, and displacements, the comparison between the two types of discs was also discussed.

Full-Heuslers are a group of materials that have repeatedly attracted the curiosity of scientists and researchers, especially for their use in the field of spintronics. In this work, we undertook a study on the structural, elastic, electronic, magnetic and thermodynamic properties of the full-Heusler Mn2OsGe alloy using the calculations of the first principles. Two approximations are used: the generalized approximation of the Perdew–Burke–Ernzerhof GGA–PBE gradient for electron-correlation exchange and the new modified Tran-Blaha form of the modified Becke-Johnson mBJ–GGA-PBE potential. As important results, we found that the compound Mn2OsGe is stable in the CuHg2Ti structure; on the other hand, we could also verify its mechanical stability at zero temperature and pressure. For the calculation of the electronic properties, we were able to determine the half-metallic ferrimagnetic character of our compound, which exhibits a metallic behavior in the state of the majority spins, and a semiconductor behavior in the state of the minority spins. An integer value of 2[Formula: see text][Formula: see text] has been recorded for a magnetic moment and this conforms to the Slater–Pauling rule.

The performance and success of cemented total hip arthroplasty is related to the stress fields in the cement mantle due to the loading caused by patient activities. To do this, a three dimensional linear elastic model was developed to investigate the intensity and distribution of equivalent stress in the bone cement (PMMA) between the microvoids. This analysis is made according to several parameters such as the size of the microvoids defects, its direction of the arrangement, its location in the seat of the stress concentration and a dependency between limit stress value (in certain stress state) and the third invariant.

This paper deals with analyzes of the influence of the perpendicularity of the spindle of the milling machine on the machined surface. This is part of the geometric errors of machine tools and in a direct manner constitutes a defect on the quality of the workpiece. Therefore, the surface roughness is particularly sensitive to the cutting speed, the feed rate, round of teeth default, the tool tip radius and the cutter teeth number. This article examines the characteristics of the surface topography of steel parts, in finishing machining using milling cutters. The study is conducted by computer simulation tests and experimental part using surface condition monitoring instruments, taking into consideration the round teeth default. The variation of the inclination of the spindle of the milling machine in three positions (90° + 30′, 90°, and 90°–30′) shows a good agreement between the simulation and the experimental results for sharp and moderately worn tools. Similarly, this study showed that the presented model could thus be integrated into systems computer-aided design and computer-aided manufacturing. Finally, the physical and statistical parameters of roughness during milling at position 90° confirmed that, when the defect of the perpendicularity is eliminated to the maximum, the best surface conditions are obtained.

In this study, we use the finite element method to analyse the behaviour of cracks emanating from microcavities in the bone cement, binding the cup to the bone, according to their size and position around the cavity, the position of the patient, the cavity’s location and the inter-defects distance (cavity-crack, crack-crack). We show that the most unstable stress intensity factor, in mode I, when the crack located in the cement’s centre and propagating along this thickness. This instability is all the more important that its size increases, tends towards the cavity, the cracks are located in a vicinity one to other and that the patient is in a squatting position. The predominant fracture mode, in mode I and II, depends on the crack’s position priming site around the microcavities. This work allows the better understanding of the interconnection phenomena of the microcavities experimentally observed.

Rolling bearings are the most fragile components of rotating machines. To avoid unforeseen stoppages and expensive production, it must then continuously monitor the condition of the bearings, and "stalk" all faults signs: an unusual noise, abnormal vibration, temperature rise, and so on. For this, these are not techniques that are missing. Conventional vibration analysis methods (envelope detection, spectre analysis, crest factor, etc.) to more specific techniques such as shock wave, they can detect faults at an early stage more or less and sometimes to determine the exact origin. In this approach we try to show the influence of operating conditions of a rolling on his life, and to award the method of real service to follow for assessing the remaining duration of survival for many supply and provide the judgments of each rotating machine in advance.

The aim of this paper is the determination of a control model of involute gears with respect to θm, based on the application of neural networks. Neural networks are appropriate for the diagnosis of complex systems and control because of its ability to handle data input and output without the need for analytical details of the system. First, we must know the angle to wipe the edge of a tooth surface, with. We acquire the points entered in standard path of the tooth. Then we execute the neurons on these points to determine the weights is the step that is called learning networks. That last request 94.41s. So it becomes all models of the gear standard with the same characteristics. So, if we wanted a control gear of the same module, it will be only a few points seized by CMMs. On the other hand, is looking for the model of the wheel to control the proper starting weight calculated from previous models. His duration of control esteem 1.6 s. Moreover, we can evaluate the deformities of gear compared to model neurons and the points entered. Finally, the role of this work is the set of model control equipment; we know it contains multiple paths and multivariate parametric complex. So, it's not easy have the control. However, ours, we can know all the deformities of the gears in about 1.60s instead of 45 min at least by the test bench, accordingly, we can say that we achieve the automation of gear control.

This paper presents and describes the design, manufacturing, calibration and performance of a universal cutting dynamometer based on the principle of extensometer strain gage techniques.The device developed in this paper was designed and calibrated for measuring separately components forces developed during turning, drilling and milling operations.Its design is carried out according to the two principal criteria which are in contradictory matters such as sensitivity and rigidity.It consists principally of two circular rings, one allowing its fixation on the tables of the three type of machine tools, and the other one is machined so that the complete dynamometer can be attached to machines tables.The strain gages are then cemented on the parts of the dynamometer where the deformations (traction, compression and torsion) are maximum.The gages are connected in the form of a full wheatstone bridge, any unbalance in which would indicate the thrust force ant the torque providing maximum sensitivity and complete temperature compensation.The disposition and the connection of the strain gages in complete Wheastone bridge are carried out according to the force component to measure while taking account of the interactions between the three directions and the compensation of the effect of the temperature.The reading is indicated on standard indicator of constraints B & K 1526.Some experimental measurements of components forces and torque in the drilling process obtained with the described dynamometer are presented and compared with available data given by other research worker.

Dynamic behavior of machine-tools while cutting is influenced mainly by both dynamic properties of its mechanical structure defined by its function of transfer Tm and the nature of its solicitation characterized by the cutting process function of transfer Tu. Good working of such machine-tool is essentially based on dynamic behavior of this too functions of transfer which of the dynamic state of the structure. The aim of this work is to study the influence of the continuous variation of cutting speed on the cutting dynamic behavior. This study allows us to draw some stability lobes which show clearly the influence of the cutting speed on the amplitude of chatter vibration. The obtained results are in good agreement with those obtained experimentally in the laboratory of Metrology in the «'Ecole Nationale des Arts et Métiers ».

This paper presents a theoretical and experimental investigation into the stability of a cantilever boring bar under regenerative cutting conditions. As this cutting tool is flexible, the regenerative chatter variation often occurs and causes several problems which not only limits productivity of cutting process, but also affects surface finish, cause premature tool failure and reduce dimensional accuracy of the machined part. Its prediction is then important as a guidance to the machine tool user for an optimal selection of cutting conditions, resulting in maximum chip removal rate without this undesirable self excited vibration. While boring, the chatter vibration may occur in the through-thickness direction of workpiece. The vibration changes removal cross section of workpiece in the present cut and furthermore in the next cut. This change in cross section produces dynamic cutting force variation. When this dynamic cutting force excites the mechanical structure and grows up the previous vibration, this closed-loop instability leads to the regenerative chatter vibration. The boring bar is modeled at the tool point by a mass, spring and damper system free to move in the two mutually perpendicular directions. The solution of the non uniform equilibrium equation of motion of the cutting tool (boring bar) yielded a characteristic equation in a form of a fourth order polynomial with complex and variable coefficients. The stability of this complex polynomial is based on the Nyquist criterion. This allowed us to plot graphs of stability which indicated clearly that the cutting condition has a decisive influence on the generation of chatter vibrations leading to the instability of cutting. The developed model is verified by cutting experiments, and it is expected that the computed results are in good agreement with the experimental one, and the analytical model is useful to optimize the cutting conditions for highly efficient cutting process.