Conceptual tribo-energetic analysis of cutting tool protective coating delamination in dry cutting of hard-to-cut aero engine alloys

Machining in dry mode is characterized by intense thermo-mechanical loading. The coupling between the thermal and the mechanical loads may lead to tool failure, especially when machining the so-called hard-to-cut alloys. Within such environments the efficiency of heat removal plays an important role in preserving the structural integrity of the tool. Efficient heat removal in dry machining depends solely on the intrinsic thermal properties of the tool for uncoated tools and on the effective properties of the tool-coating combinations for coated tools. Thermal loads may also accelerate wear of the tool. As such, a relationship between the wear and the intrinsic thermal properties of the tool is worthy of investigation. This paper investigates such a relationship. Here we team numerical simulations to SEM-imagery to map the thermal conductivity within the tool zone of action of a coated carbide tool. The results indicate that, depending on the temperature rise, the tool-tip might undergo a severe drop in thermal conduction. This drop may locally restrict the ability of the tool material to dissipate the applied thermal load. This may nucleate thermally congested clusters within the tool-tip where the material completely loses the ability to transport heat. Thermal congestion renders an energetically active zone where the thermal energy available may be used to activate wear through different mechanisms. It is also found that the immediate layer under the surface of the tool tip is important to enhance the ability of the tool material to dissipate the thermal loads. The results also highlight the importance of matching the temperature dependant properties of the different coating layers in order to enhance delamination resistance.     

Application of DKMQ24 shell element for twist of thin-walled beams: Comparison with Vlassov theory

This article presents the application of DKMQ24 shell element for twist of thin-walled beams. This element passed the patch tests for membrane, bending and shear problems and gave fine results for plate and shell problems analysis without shear locking. Thin-walled cantilever beams are analyzed using this element. DKMQ24 gives good results for cantilever beams with open cross-section for a very few number of element. Moreover, the comparison of the results obtained with Vlassov analytical solution enables to evaluate the accuracy of the twist rigidity, J_d, which depends on an empirical coefficient in Vlassov theory.     

2‐Aminopyridines as an α‐Bromination Shuttle in a Transition Metal‐Free One‐Pot Synthesis of Imidazo[1,2‐a]pyridines

A wide range of imidazo[1,2‐a]pyridines are accessible from cheap and readily available 2‐aminopyridines and 1,3‐dicarbonyl compounds using a unique CBrCl₃/2‐aminopyridine system for bromination at the α‐carbon. 2‐Aminopyridine is not only the substrate but also acts as a bromination shuttle, transferring the bromine atom from CBrCl₃ to the α‐carbon of the 1,3‐dicarbonyl. The reaction mechanism involves a series of reversible steps, including an addition reaction with cyclic transition state, to form a bromo‐hemiaminal intermediate. Isolated yields of up to 97% were obtained under mild conditions and at short reaction times in this transition metal‐free, one‐pot synthesis.

     

Aperiodic Fourier modal method in contrast-field formulation for simulation of scattering from finite structures

This paper extends the area of application of the Fourier modal method (FMM) from periodic structures to aperiodic ones, in particular for plane-wave illumination at arbitrary angles. This is achieved by placing perfectly matched layers at the lateral sides of the computational domain and reformulating the governing equations in terms of a contrast field that does not contain the incoming field. As a result of the reformulation, the homogeneous system of second-order ordinary differential equations from the original FMM becomes non-homogeneous. Its solution is derived analytically and used in the established FMM framework. The technique is demonstrated on a simple problem of planar scattering of TE-polarized light by a single rectangular line.     

A Posteriori Error Estimates of Discontinuous Galerkin Method for Nonmonotone Quasi-linear Elliptic Problems

In this paper, we propose and study the residual-based a posteriori error estimates of h-version of symmetric interior penalty discontinuous Galerkin method for solving a class of second order quasi-linear elliptic problems which are of nonmonotone type. Computable upper and lower bounds on the error measured in terms of a natural mesh-dependent energy norm and the broken H ¹-seminorm, respectively, are derived. Numerical experiments are also provided to illustrate the performance of the proposed estimators.     

Inclined magnetized and energy transportation aspect of infinite shear rate viscosity model of Carreau nanofluid with multiple features over wedge geometry

Heat transference in fluid mechanism has a deep influence in real-life applications like hot-mix paving, recovery of energy, concrete heating, heat spacing, refineries, distillation, autoclaves, reactors, air conditioning, and so forth. In this attempt, findings related to energy exchange with features of infinite shear rate viscosity model of Carreau nanofluid by placing inclined magnetic dipole over the wedge are made. The main role in the transportation of heat is exercised by incorporating facts of r adiation, nonuniform heat sink source, Brownian motion, thermophoresis, and chemical reaction. The mathematical system of the infinite shear rate viscosity model of Carreau nanofluid gives a system of partial differential equations and furthermore, these are moved into ordinary differential equations. A numerical procedure is applied via shooting/bvp4c to obtain numerical results. Inclined magnetic dipole gives a lower velocity of Carreau nanofluid. Due to the relaxation time factor velocity of Carreau fluid gets down. A* causes to generate the heat internally, so due to this, temperature increases rapidly. The increasing rate of temperature is found very high for the growing Hartmann number. The rate of mass transport becomes low for gradual increment in the parameter of thermophoresis, wedge angle, and Prandtl. Inclined magnetic dipole gives a lower velocity of Carreau nanofluid. Due to the relaxation time factor, the velocity of the Carreau fluid goes down. The absence and presence of magnetic numbers have no influence on velocity, temperature, and concentration files for Le, R_d, θ_f, γ, We, β, Pr, Nb, Nt, A.     

Two-Grid Discontinuous Galerkin Method for Quasi-Linear Elliptic Problems

In this paper, we consider the symmetric interior penalty discontinuous Galerkin (SIPG) method with piecewise polynomials of degree r≥1 for a class of quasi-linear elliptic problems in Ω⊂ℝ². We propose a two-grid approximation for the SIPG method which can be thought of as a type of linearization of the nonlinear system using a solution from a coarse finite element space. With this technique, solving a quasi-linear elliptic problem on the fine finite element space is reduced into solving a linear problem on the fine finite element space and solving the quasi-linear elliptic problem on a coarse space. Convergence estimates in a broken H ¹-norm are derived to justify the efficiency of the proposed two-grid algorithm. Numerical experiments are provided to confirm our theoretical findings. As a byproduct of the technique used in the analysis, we derive the optimal pointwise error estimates of the SIPG method for the quasi-linear elliptic problems in ℝ ^d ,d=2,3 and use it to establish the convergence of the two-grid method for problems in Ω⊂ℝ³.     

Spin Wave Excitation in a Mechanically Alloyed Co2MnSi Solid Solution

The spin wave excitation has been analyzed in a Co₂MnSi solid solution compound. A Co₂MnSi sample was prepared by utilizing a mechanical alloying technique in Ar atmosphere. After 72 hours of milling time, the Co₂MnSi solid solution was transformed from a multiphase to a single broadening phase, which is essential in understanding the spin wave excitation in a nanocrystalline material. The magnetization was measured from 7 K to room temperature by using a superconducting quantum interference device (SQUID) magnetometer. The thermal-magnetization curve was found to obey the Bloch law, M _S(T)=M _S(0)(1?BT ^3/2?CT ^5/2). Based on this formula, the spin wave stiffness constant was calculated from the magnetization data at low temperatures. The values were 0.264 eV?Ų and 0.325 eV?Ų for 72 and 96 hours of milling time, respectively. The spectroscopic splitting g-factor was obtained via electron spin resonance (ESR) measurements at X-band (9.45 GHz).     

A comparative study of adaptation algorithms for nonlinear system identification based on second order Volterra and bilinear polynomial filters

Nonlinear filtering techniques have recently become very popular in the field of signal processing. In this study we have considered the modeling of nonlinear systems using adaptive nonlinear Volterra filters and bilinear polynomial filters. The performance evaluation of these nonlinear filter models for the problem of nonlinear system identification has been carried out for several random input excitations and for measurement noise corrupted output signals. The coefficients of the two candidate filter models for are designed using several well known adaptive algorithms, such as least mean squares (LMS), recursive least squares (RLS), least mean p-norm (LMP), normalized LMP (NLMP), least mean absolute deviation (LMAD) and normalized LMAD (NLMAD) algorithms. Detailed simulation studies have been carried out for comparative analysis of Volterra model and bilinear polynomial filter, using these candidate adaptation algorithms, for system identification tasks and the superior solutions are determined.