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The paper studies the structure, chemical and phase compositions, hardness and strength of welded joints obtained in AISI 321 steel and Grade 2 titanium alloy sheets by CO2 continuous laser with the use of intermediate Cu, Ni and Ag-Cu-Zn alloy inserts. It is demonstrated that the maximum strength of welded joints is achieved by the welding conditions enabling one to form multiphase structures with intermetallics in the material of a weld, rather than only those based on solid solutions. [ABSTRACT FROM AUTHOR]

The paper presents research results on the properties of polymer composite materials based on ultrahigh molecular weight polyethylene and polytetrafluoroethylene modified with carbon fibers. It has been established that an increase in CF concentration is accompanied by a decrease in the stress-strain properties of a PCM based on PTFE, as well as by a change in the behavior of tensile strain curves of the PCM. It has been found that the decrease in stress-strain properties and the change in the failure mode of PTFE-based composites containing CF of the LO-1-12N/40 grade occur at a concentration of 5 wt%, and with the introduction of fibers of the Belum brand, 10 wt% concentration is required. This is probably due to the different values of the critical volume content (φm) of CF in PTFE. It has been detected that the strength is increased by 80% at 5% compression of PCM, and it is doubled at 10% compression in comparison with unfilled PTFE. The rate of mass wear of the PCM based on PTFE containing discrete carbon fibers decreases with an increase in filler concentration. The prospects of using carbon fibers as a reinforcing element of UHMWPE with the aim of obtaining new composites with high tribotechnical characteristics intended for operation under conditions of limited lubrication or dry friction are shown. It has been established that, to improve the stress-strain properties and wear resistance of the PCM based on UHMWPE, it is efficient to use carbon fiber of the Belum brand as a filler, since the interphase interaction of UHMWPE with the fiber is strong due to a hydrophobic fluoroorganic coating on the surface of these carbon fibers. [ABSTRACT FROM AUTHOR]

Residual stress in layered composites significantly affects their mechanical properties. One of the most important tasks in the sphere of experimental mechanics is the development of effective methods for the accurate determination of residual stress values. This paper describes a modified destructive testing method implemented through layer-by-layer stitching. It differs from previous analogous methods by the use of electronic speckle pattern interferometry to measure the deformation response of a given sample. The interpretation of the initial experimental data in “stress terms” was carried out based on modeling through the use of the finite element method (FEM). [ABSTRACT FROM AUTHOR]

In contrast with neat polymers, filled polymeric composites of ultrahigh molecular weight polyethylene (UHMWPE) are certainly more efficient in manufacturing industrial products (for instance, when reinforcing fibers are loaded). An experimental-theoretical technique for designing a polymer composite with specified properties is discussed in the paper. An approach to determine control parameters (phase composition, physical and mechanical properties, etc.) in order to design a composite with prescribed effective properties or providing them within a predetermined range is proposed. With the use of the approach based on the experimental data analysis in concern of effective characteristics versus the values of the control parameters, corresponding response surfaces of the physical-mechanical characteristics are constructed in the space of states. This allows one to determine the correct and reachable values of the control parameters. The calculated response surfaces make it possible to reveal the range of values of control parameters for specified characteristics of multicomponent reinforced extrudable UHMWPE polymer composites. [ABSTRACT FROM AUTHOR]

The paper reports the simulation results of mechanical behavior of porous ceramics based on aluminum oxide. A mechanical response of porous ceramic materials is described using the mathematical model of an elastic-brittle-plastic medium and various fracture criteria. Depending on the chosen fracture criterion, the width of fracture zones and the averaged loading diagram form are shown to change. With the maximum inelastic strain fracture criterion, the loading diagram most closely corresponds to brittle material; with the accumulated damage criterion, it corresponds to ductile material. The fracture zones are maximum for the strain criterion and narrowest for the damage criterion. [ABSTRACT FROM AUTHOR]

The paper studies heart deregulation by high-resolution rhythmocardiography (RCG) and analyzes heart rate variability (HRV) in patients with stable angina pectoris (SAP) before and after of percutaneous transluminal coronary angioplasty (PTCA). HRV deregulations were defined in 57 patients (pts) in special form of small lengthening of 3-5 RR intervals (Fig. 2). They had a period of 2.07±0.41 s and a spectral power of 0.218±0.016 Hz in the high-frequency range in the wave HRV structure. Such waves were recorded in pts with chronic intoxication in different somatic diseases during inflammation. The comparison of HRV in pts with SAP and healthy control pts (Fig. 1), and also before and after PTCA, showed that HRV indices were the worst under endogenous intoxication. The most expressive regulative HRV breaches were detected after PTCA. This intoxication may be a predictor of inflammation during and after PTCA. The RCG diagnosis of the HRV waves was not defined by standard methods. Such HRV wave structure shows supplementary intoxication complications after PTCA in the pts, and it can deteriorate the PTCA results. [ABSTRACT FROM AUTHOR]

The paper presents the results of magnetoelastic cyclic testing of cylindrical high-chromium 30Kh13 steel (0.3% C, 13% Cr) samples after quenching and tempering. Before each series of 100-cycle tensile loading, the samples were magnetized to saturation. The load amplitude was gradually increased by 50 MPa from one series to another. At the same time, the remanence field strength of the sample was recorded, which was proportional to magnetization. The range of tempering temperatures was determined to make memory force gauges. At amplitude loads or no-loads, as the cycle number increases, the field strength values decrease (relax) according to the power dependence, as in [1]. This suggests that magnetoelastic power relaxation is a universal property of steels. Depending on the load amplitude, complex relaxation parameters showed a practically uniform behavior for tempering temperatures of up to 500 0C inclusive. At higher tempering temperatures, qualitative changes of these dependences take place, due to a structural transformation of the material, namely, martensite decomposition. [ABSTRACT FROM AUTHOR]

The paper describes the features of heart rate variability in COPD. 58 male patients with COPD and 38 participants without COPD, aged 45 to 74, were enrolled in the study. Rhythmocardiography was performed in order to assess heart rate variability in all the participants enrolled in the study. We analyzed the following parameters of heart rate variability: RR, SDNN, ARA, σm, σs, σl, VLF%, LF%, and HF% in patients with and without COPD. Reduction of heart rate variability (SDNN), predominance of humoral-metabolic regulation of pacemaker activity of the sinus node (this regulation factor makes a minimum contribution in healthy individuals) were found in COPD compared to participants without COPD. We detected very low frequency waves with upward deviation from the main RCG waves corresponding to the bronchial obstructive syndrome in patients with COPD. We also analyzed the heart rate variability parameters of patients with COPD within the group. Heart rate variability changes were more severe in patients with pulmonary hypertension. Segments of the rhythmocardiogram with identical R-R intervals can be detected in patients with pulmonary hypertension. [ABSTRACT FROM AUTHOR]

This paper analyses the progressive failure of a variable-stiffness composite structure (VSCS). The composite structure is simulated by means of a design method developed earlier. The design method allows curvilinear fibers to be adapted to various geometric discontinuities (holes, notches, etc.) or non-uniform loading. The fiber orientation and fiber volume fraction are heterogeneous in the VSCS. To model progressive failure, a material property degradation method (MPDM) is used. The properties of the composite structure are locally changed due to the nonuniformity in the fiber volume fraction, and the change of the properties is taken into account in the MPDM. A rectangular plate with a hole under tensile loading is modeled, and it is shown that use of the VSCS is more effective than the use of a composite structure with rectilinear reinforcement (orthotropic material) under identical conditions. [ABSTRACT FROM AUTHOR]

In the present paper, the investigation results on the strain dependence of the Rayleigh wave velocity are presented. Plane dog-bone metal specimens were deformed by tension at a constant strain rate. The specimens were made of low-carbon steel with a carbon content of 0.1% (C10) and 0.2% (C22), martensitic stainless steel X40Cr13, and commercially pure titanium (CP Ti). Discontinuity points in the stress dependences of ultrasonic velocity and damping were found. These points are considered to be ultrasonic criteria for the stage change in the deformation process. [ABSTRACT FROM AUTHOR]

The results of ultrasonic wave velocity and acoustic nonlinearity measurement in carbon steels are presented in this paper. Samples were tested by fatigue loading in the range from 0 to 100 thousand cycles with the step of 10,000 cycles to obtain the dependence of the acoustic properties on fatigue wear. It was found that the dependences of the Rayleigh wave velocity on the number of loading cycles have three stages. In the first stage, the velocity decreases. This stage corresponds to the burn-in period in the lifetime of metalworks. During the longest, second stage, the Rayleigh wave velocity remains constant, and this corresponds to the operating life. During the final, third stage, corresponding to the catastrophic wear of the metal, the ultrasonic velocity decreases again. The acoustic nonlinearity grows with the number of cycles exponentially, and it does not depend on the carbon content in the steel. Whereas an open fatigue crack leads to a decrease in the acoustic nonlinearity. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental verification of a numerical solution to the problem of fracture of a cast-iron plate with a central hole, obtained by finite element modeling and an original author's technique. Experimental verification is performed by real-time laser dynamic speckle interferometry using a software-hardware complex developed by the authors. The moments of transition from the stage of fatigue crack initiation to the stage of stable growth and subsequent brittle fracture of the plate are defined. [ABSTRACT FROM AUTHOR]

Titanium alloys have found wide application in the aircraft industry. They are in use as materials for products for which the period of safe operation is very significant. The internal structure and service life of components heavily depends on their manufacture and operation processes. Besides, it is important to take into account damage accumulation processes and the evolution of material properties during deformation. The purpose of the present research is to develop a direct multilevel mathematical model based on crystal plasticity. This model must be able to allow the analysis of the behavior of titanium alloy materials and to describe the processes of damage accumulation. Crystal plasticity is a promising framework for solving such problems since it is able to describe the evolution of the internal material structure and the accumulation of defects of various nature. In this paper, the structure of the mathematical constitutive model, its evolutionary equations for dislocation densities and dislocation-based submodels of crack nucleation are given. [ABSTRACT FROM AUTHOR]

This paper deals with an ultrasonic technique based on the measurement of acoustic birefringence of shear elastic waves for the evaluation of plasticity margin of an aluminum alloy operating in the conditions of Far North and the Arctic. We tested flat samples under uniaxial static tension at room and subzero temperatures. Besides, we performed ultrasonic measurements. We have found that acoustic birefringence monotonically changes during plastic deformation. The effect of plastic strain on the acoustic birefringence is associated with damage accumulation and texture change. As a result of the study, we have obtained a correlation equation allowing us to estimate the plasticity margin of the aluminum alloy at a subzero temperature, as well as at room temperature, using the measurement results of acoustic birefringence. [ABSTRACT FROM AUTHOR]

The paper presents first results of obtaining metal-matrix composites based on severe plastic deformation by shear under pressure of layered Al and Cu components. Three-layer composites with different alternation of layers, i.e. Al-Cu-Al and Cu-Al-Cu, were processed by constrained high pressure torsion to produce monolithic disk-shaped samples without pores. Analysis of the macroscopic homogeneity showed that different alternation of layers led to varying degrees of mixing of the starting components. [ABSTRACT FROM AUTHOR]

The paper is devoted to the analysis of the structural features, which determine an increase in the strength and fracture energy of the surface layers of a NiCr-TiC metal-ceramic composite modified by a pulsed electron beam, from the standpoint of bionic design of composite structures. The analogy of the structure and ratio of the mechanical parameters of the components in the surface layers of this composite and the biological one (mollusc shells) is discussed. Using computer simulation, we show that the key factors determining the increase in the mechanical properties of the modified surface layers of a cermet composite are the geometric and mechanical parameters of ceramic inclusions. We have estimated the ranges of the values of these parameters, which provide the optimal ratio of strength, stiffness and fracture energy. [ABSTRACT FROM AUTHOR]

This paper studies the applicability of magnetic parameters for testing residual stresses in ferromagnetic structural steels. A unique correlation of the coercive force, initial magnetic permeability, reversible magnetic permeability in the remanent state, and the ratio of initial to reversible permeability with the level of microstresses for Armco iron is established. Thus, the prospects of using these parameters for the evaluation of residual stresses in ferromagnetic structural materials are demonstrated. It is shown that the ratio of reversible magnetic permeability in the remanent state to initial magnetic permeability is the most sensitive to the variation of microstresses. [ABSTRACT FROM AUTHOR]

The paper presents an automated system for monitoring the deformation state of a building complex. The measurement unit of the system records the vertical displacements of a number of bearing columns using the hydroleveling method. In the analytical block, numerical modeling of deformation processes in the subsoil–foundation– building system is performed. The information on the foundation settling obtained during monitoring is used to specify the boundary conditions for modeling the stress-strain state of the structure. Thus, the deformation response of all structural elements to uneven vertical settling of supporting columns is evaluated. The monitoring system has been working since 2010 and it has demonstrated high efficiency. [ABSTRACT FROM AUTHOR]

The present work focuses on methods for investigating the strength of the material of the weld produced by the currently most widely used methods of welding polymer pipes – butt welding with a heated tool, welding with an embedded heating element, and fusion welding with a heated tool. The methods under consideration have been developed due to the absence of simple methods of the quantitative evaluation of the strength of the weld material in the normative documents and scientific papers devoted to the investigation of welded joints of polymer pipes, which are necessary for studying the efficiency of the developed technologies for welding polymer pipes at low temperatures in open areas. The proposed methods for determining the strength of the weld can be used to assess the influence of changing welding parameters on the strength of the joint, as well as to assess the strength of the perimeter of welding and the strength in zones of welded joints in case of fusion welding. The same methods can be used for qualification tests of welders. [ABSTRACT FROM AUTHOR]

The paper considers the elastic properties of epoxy composites reinforced by 6 types of silica nanoparticles with different average diameter at the same weight concentration of 1.1%. The addition of silicon nanopowders increases the modulus of elasticity. For powders of the same origin, with an increase of the modulus of elasticity, a decrease in the characteristic diameter of the filler particles at a constant concentration is observed. It is shown that the characteristic average particle size is not the only factor determining the growth of the elastic modulus, since the growth of the modulus is significantly different for powders of different producers. [ABSTRACT FROM AUTHOR]

This paper studies a new way of cladding particles by preliminary mechanical mixing of particles of a refractory material (TiN) with particles of a binding metal (Ti) followed by forming granules containing 20 mass fractions of initial particles of titanium nitride and their further processing in an argon-helium plasma jet in a controlled atmosphere. As a result of experimental studies, a composition powder consisting of spherical particles sized from 0.1 to 40 μm is obtained. The refractory nanoparticles of titanium nitride in it are evenly distributed over the volume of the binding metal (titanium) and completely plated by it. The surface morphology and the internal structure of the particles are studied, the results of X-ray phase analysis are presented, and a map of element distribution over both the surface and volume of the composition particle is obtained. This method of producing nanomodifying compositions helps to improve homogeneity of the distribution of refractory elements in the melt volume, as well as their wettability, which increases the effectiveness of modifying the material properties. [ABSTRACT FROM AUTHOR]

In the paper, the influence of heat treatment on the mechanical characteristics of welds obtained by laser welding is investigated. Changes in the microstructure and strength properties depending on various modes of heat treatment of the welds are investigated. As a result, full heat treatment provides a 1.5 times increase in the tensile strength of the weld in comparison with the strength of the alloy as delivered from the factory. [ABSTRACT FROM AUTHOR]

In this paper, an approach to solving the problem of the determination of effective stress-strain, thermophysical and electrophysical properties of filled composite materials on the basis of the variational principles is developed. In the numerical implementation, it might be reduced to the use of the finite element method (FEM). An approach, possessing a certain generality, to finding effective physical-mechanical, thermophysical and electrophysical properties of filled polymer composites is proposed and described. Firstly, a general concept based on obtaining detailed parameters of the composite state under external impact taking into account the actual structure of the material is developed. Then, the averaging procedure aimed at obtaining effective properties of the composites is employed. Secondly, the realization of boundary problems is reduced, for all cases (physical-mechanical, thermophysical and electrophysical), to the formulation of the corresponding variable principles and their realization by the methods of computational mechanics, in particular, by the finite element method. [ABSTRACT FROM AUTHOR]

In this paper, a method of mechanical impact on an element of a ring frame of a U-shaped cross-section with the aim of opening a closed delamination to a minimum size is considered, which will allow this defect to be detected by the nondestructive X-ray diffraction method, in condition that the loading will not lead to the formation of new defects and further growth of the existing ones. [ABSTRACT FROM AUTHOR]

The paper studies the structure, chemical and phase compositions and hardness of Fe-Ni-Ti-C-B composites produced by self-propagating high-temperature synthesis (SHS). It is demonstrated that, when Fe, Ni, Ti, C and B4C are used as initial materials in the form of a powder mixture poured into a steel pipe, a one-piece multilayer plate is formed under SHS, inside which there is a composite with a matrix of a solid solution of Fe in a γ-Ni lattice and reinforcing TiC, TiB2, and Fe2B particles with a hardness of 62 HRC. The inner surface of the steel shell is firmly joined to the composite due to the synthesis products diffusing into the steel. [ABSTRACT FROM AUTHOR]

The paper presents an experimental investigation of the mechanical behavior of specimens made of alumina ceramics prior to catastrophic fracture and the transition to the blow-up mode. Ceramic specimens are tested in three point bending and uniaxial compression tests. The surface velocity of the loaded specimens is registered using a laser Doppler vibrometer. The duration of the stage of a catastrophic increase in the lateral surface velocity prior to fracture is approximately half a millisecond in three-point bending tests and about 0.1 ms in compression tests. [ABSTRACT FROM AUTHOR]

Analysis of design methods for composite beams with curvilinear fiber trajectories is considered in this paper. The novelty of this approach is determined by the fact that traditional composite materials are typically formed using prepregs with rectilinear fibers only. The applications of the results are associated with designing shaped members with a composite structure by using of biomechanical principles [1,2]. One of the problems is evaluation of the effect of fiber misorientation on the stiffness and load carry capacity of a shaped composite element with curvilinear fiber trajectories. An equistrong beam with a constant cross-section area is considered as an example, and it can be produced by forming of a unidirectional fiber bunch impregnated by a polymer matrix. Methods for evaluating the effective elastic modulus for structures with curvilinear fiber trajectories are validated. The misorientation angle range (up to 5 degrees), when a material with required accuracy can be considered as homogeneous, is determined, fiber misorientation being neglected. It is shown that, for beams with a fairly small height-to-width ratio, it is possible to consider only 2D misorientation. [ABSTRACT FROM AUTHOR]

The paper is concerned with the skin effect of plastic deformation, which was discovered circa ninety years ago. The study is carried out with the help of the hydrogen diagnostics. Accumulation of hydrogen is shown to occur due to the dissociation of atmospheric moisture under the process of plastic deformation of metals in a thin surface layer comparable to the grain size. Hydrogen is accumulated in pores and microcracks, whose volume in the surface layer increases hundred-fold. The zones of localization of plastic deformation coincide with the local surface zones of hydrogen storage. The obtained experimental data lead to the conclusion that the surface layer cannot be considered as a continuous medium. [ABSTRACT FROM AUTHOR]

This paper studies the influence of martensite content in the 09Cr17Ni5Al two-phase austenitic chromium-nickel steel on acoustic, magnetic and electrical properties. The non-contact electromagnetic-acoustic (EMA) method of excitation and reception of acoustic waves by means of a through-type transducer and the method of magnetic saturation and electrical resistance were used for the research. Acoustic wave velocities, the efficiency of EMA transformation and magnetic saturation intensity were considered as informative parameters. [ABSTRACT FROM AUTHOR]

With two structural steels (the steels 50 and 09G2S) as examples, the paper studies the effectiveness of a new method of ultrasonic impact-frictional treatment (UIFT) for the hardening and nanostructuring of the surface layer with the variation of the tilt angle of the vibrating indenter and the treatment environment. It is demonstrated that treatment with tool tilt angles different from 90° and with the absence of a contact liquid results in the formation of a nanostructured surface layer with increased microhardness. [ABSTRACT FROM AUTHOR]

The paper consists of two parts united by the central idea of the random field of the microstructure of the material. The first part addresses a discrete static approach to describing the localization effect of plastic deformation known with the help of finite-element analysis under the assumption that the deformation of each of the grains obeys a bilinear law with a normal distribution of the yield stress over the grains. The result is a surface relief in the form of diagonally directed strips, which allows one to treat the deformed surface as Panin’s "chessboard". The second part is concerned with a dynamic continuum approach to the description of the random microstructure of materials. The problem of the propagation of stochastic waves modeled by waves in media with random elastic and mass properties is solved by means of the integral decomposition of the wave amplitude over the wave numbers. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) have received copious interests due to their unique properties such as small in size, reactive, high surface area and can be potentially applied in myriad fields including physics, chemistry, medicine and material sciences. However, the nanosized of gold particles makes them very reactive and undergo aggregation without protection. For that reason, supporting materials are introduced to prevent the aggregation of the AuNPs. In particular, metal oxide for example, titanium dioxide or titania nanotubes (TNTs) has been used as a support material because of its inertness, high porosity and great surface areas. Nevertheless, achieving precise control of attachment AuNPs on the TNTs substrate by conventional methods such as thermal evaporation and conservative heating are far from satisfactory. Herein, in this work, a new approach has been developed to synthesize controlled and uniformed attachment of AuNPs onto fabricated electrochemically-anodized TNTs by a spin coating technique. This preliminary work used different spin rate of 500, 1000 and 2000 revolutions per minute (rpm), following by heat treatment at 250 °C for 2 hours. The FESEM micrograph showed the anodized TNTs with good morphological structures were successfully fabricated at a voltage of 50 V in a mixture of ethylene glycol containing 0.5 wt. % ammonium fluoride solution, with an average nanotubes diameter of 150 nm. Meanwhile, the attachment of AuNPs on the fabricated TNTs has been effectively achieved at a higher spin rate of 2000 rpm and the EDX analysis confirmed the deposition of AuNPs over the TNTs. The AuNPs-TNTs also were tested for the catalytic reduction of p-nitrophenol (p-NP), in which is discussed shortly in this paper. [ABSTRACT FROM AUTHOR]

This paper presents an application of the probabilistic analysis of structural resistance of the reactor building of VVER 440/213. The present work analyses the impact of combination of pressure load with thermal load and the extremal climatic situation. The evaluation is based on an extension of the smeared crack model developed on base of Kupfer's bidimensional failure criterion, rotated crack, CEB-FIP model of failure energy and implemented into the ANSYS system. The non-linear analysis was considered for the median values of the input data and the probabilistic analysis models the uncertainties of loads, material resistance and other modeling issues [ABSTRACT FROM AUTHOR]

Additive-manufacturing technologies have been gaining tremendously in popularity for some years in the production of single-part series with complex, close-to-final-contour geometries and the processing of special or hybrid materials. In principle, the processes can be subdivided into wire-based and powder-based processes in accordance with the Association of German Engineers (VDI) Guideline 3405. A further subdivision is made with respect to the smelting technology. In all of the processes, the base material is applied in layers at the points where it is needed in accordance with the final contour. The process that was investigated was wire-based, multi-pass welding by means of gas–metal arc welding. This was accomplished in the present study by determining the material parameters (thermo-mechanical and thermo-physical characteristics) of the welding filler G3Si1 (material number: 1.5125) that were necessary for the numerical simulation and implementing them in a commercial FE program (MSC Marc Mentat). The focus of this paper was on simulation and validation with respect to geometry and microstructural development in the welding passes. The resulting minimal deviation between reality and simulation was a result of the measurement inertia of the thermocouples. In general, however, the FE model can be used to make a very good predetermination of the cooling behaviour, which affects the microstructural development and thus the mechanical properties of the joining zone, as well as the geometric design of the component (distortion, etc.). [ABSTRACT FROM AUTHOR]

In this paper we propose two formulations of Cahn-Hilliard equations, which have several applications in cancer growth modeling and material science phase-field simulations. The first formulation uses one C4 partial differential equations (PDEs) the second one uses two C2 PDEs. Finally, we compare the computational costs of direct solvers for both formulations, using the refined isogeometric analysis (rIGA) approach. [ABSTRACT FROM AUTHOR]

In the last few decades the alkali halides emerged as crystals with useful applications and their high-pressure behaviour is the most intensively studied subject in high-pressure physics/chemistry, material science, and geosciences. Most alkali halides follow the B1 (NaCl-type)→B2 (CsCl-type) phase-transition route under pressure. In the present paper, we have investigated the characteristics of structural phase transition that occurred in Lithium Florid compound under high pressure. The transition pressure of B1-B2 was calculated using an effective interionic interaction potential (EIOP). The changes of the characteristics of crystals like, Gibbs free energy, cohesive energy, volume collapse, and lattice constant are calculated for the B1 and B2 structures. These data were compared with the available experimental and theoretical data. [ABSTRACT FROM AUTHOR]

The continuous search for safe and powerful energetic materials is an exciting research challenge that attracts experts in material science, chemistry, physics, and engineering. Elucidation of meaningful relationships between sensitivity and structures of explosives is a fundamental problem, which needs to be addressed to ensure successful design of new materials and improvements of existing energetics. In this paper, quantum-chemical DFT study of thermal decomposition of a series of recently synthesized oxadiazole-based explosives, BNFF (3,4-bis(4-Nitro-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole-N-oxide), BNFF-1 (3,4-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole) and ANFF-1 (3-(4-amino-1,2,5-oxadiazol-3-yl)-4-(4-nitro-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole) is presented. We also show how the knowledge of discovered interplay between the structures and thermal stability of these compounds is used to design several novel candidate heterocyclic energetic molecules, including DNBTT (2,7-dinitro-4H,9H-bis([1,2,4]triazolo)[1,5-b:1',5'-e][1,2,4,5]tetrazine), the compound with high thermal stability, which is on predicted to be par or better than that of TATB. [ABSTRACT FROM AUTHOR]

Additive manufacturing, based on layer-by-layer deposition of a feedstock material from a 3D data, can be mechanistically associated to welding. With feedstock fusion based processes, both additive manufacturing and welding implement similar heat sources, feedstock materials and translation mechanisms. From material science perspectives, additive manufacturing can take clue from lessons learned by millennium old welding technology to rapidly advance in its quest to generate fit for service metallic parts. This paper illustrates material science highlights extracted from the fabrication of a 316 L air vent and the functional repair of a Monel K500 (UNS N0500) with Inconel 625. [ABSTRACT FROM AUTHOR]

An integrated computational materials engineering method is proposed in this paper for analyzing the design and preforming process of woven carbon fiber composites. The goal is to reduce the cost and time needed for the mass production of structural composites. It integrates the simulation methods from the micro-scale to the macro-scale to capture the behavior of the composite material in the preforming process. In this way, the time consuming and high cost physical experiments and prototypes in the development of the manufacturing process can be circumvented. This method contains three parts: the micro-scale representative volume element (RVE) simulation to characterize the material; the metamodeling algorithm to generate the constitutive equations; and the macro-scale preforming simulation to predict the behavior of the composite material during forming. The results show the potential of this approach as a guidance to the design of composite materials and its manufacturing process. [ABSTRACT FROM AUTHOR]

An experimental study on superplastic forming behaviors and microstructure characters of commercial magnesium alloy sheet AZ31B is presented in this paper. The main experimental results show that the commercial magnesoium alloy AZ31B sheet has superplastic capability. For the received sheet without any pre-processing, the maximum elongation is 295%. The dynamic recrystallization and grain refinement can be found, In the case of temperature <350°C, and the grain growth appears if temperature >= 350°C. The superplastic behaviors can be improved by controlling the dynamic recrystallization and grain refinement. Some experimental results of free superplastic bulging are presented in this paper. The results show that influence of temperature on forming capability is much less than the influences of temperature on elongation. In addition, the maximum principle strain. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

It is always a curiosity and interest among researchers working in the field of material science to know the impact of high temperature on the physical and transport properties of the materials. In this paper, we report on the design and working of a system for the measurements of electrical resistivity with high temperature. It was designed at our place and successively used for these measurements in the temperature range from room temperature to 500 ˚C. [ABSTRACT FROM AUTHOR]

The paper is devoted to theoretical investigation of the influence of gas pore pressure on the characteristics of mechanical response of gas-filled permeable materials and media. Investigation was based on computer-aided simulation by hybrid cellular automaton method. Mechanical response of the model gas-filled samples of young brown coal under unconfined (in absence of constraint) and constrained conditions was investigated. The simulation results showed that increase of the pore pressure of the gas acting on the solid skeleton leads to decrease in materials strength. This is due to the fact that the gas pressure makes an additional contribution to integral pressure acting in volume of the loaded medium. Consequences of this are earlier beginning of plastic deformation and fracture of the material. It should be noted that in the constrained conditions decreasing of material strength with increasing gas pore pressure has more pronounced nonlinear character' in comparison with similar tests for unconfined samples. This is due to the fact that loading of constrained material is accompanied by its massive cracking and' consequently' by a grater decrease of the strength characteristics of the medium. [ABSTRACT FROM AUTHOR]

The composite materials with different structure find a variety of applications. However, the peculiarities of the propagation of chemical reactions between structural elements during composite material synthesis are poorly studied. This paper suggests a model describing the conjugation of structure composite elements using a solid phase reaction at the ignition from a free surface. It was established that depending on the relation between layer sizes, various conversion regimes between inert materials are observed. The regimes differ in temperature values in the reaction zone, heterogeneities of temperature field and reaction zone thickness. Relation between thermophysical properties and thicknesses of layers can both promote reaction and retard it. [ABSTRACT FROM AUTHOR]

X-ray lithography is an ideal technique by which high aspect ratio and high spatial resolution micro/nano structures are fabricated using X-rays from synchrotron radiation source. The technique has been used for fabricating optics (X-ray, visible and infrared), sensors and actuators, fluidics and photonics. A beamline for X-ray lithography is operational on Indus-2. The beamline offers wide lithographic window from 1-40keV photon energy and wide beam for producing microstructures in polymers upto size ~100mm x 100mm. X-ray exposures are possible in air, vacuum and He gas environment. The air based exposures enables the X-ray irradiation of resist for lithography and also irradiation of biological and liquid samples. This paper gives a brief introduction of X-ray lithography beamline, complimentary processing steps to realize micro structures, and various high aspect ratio structures fabricated for different applications. Using X-ray lithography beamline various refractive and diffractive synchrotron optics for micro/nano focusing are being developed for second and third generation synchrotron sources. X-ray refractive lenses are produced in X-ray sensitive resist PMMA (poly methylmethaacrylate) and high radiation and temperature resistance material SU-8. The performances of these lenses at various photon energies are evaluated at Indus-2 and Diamond Light Source. Few 3D structures are also produced using this beamline. [ABSTRACT FROM AUTHOR]

In the present paper the influence of the reference system with regard to the characterization of the surface finishing is analyzed. The effect of the reference system's choice on the most representative surface finishing parameters (e.g. roughness average Ra and root mean square values Rq) is studied. The study can also be applied to their equivalent parameters in waviness and primary profiles. Based on ISO and ASME standards, three different types of regression lines (central, mean and orthogonal) are theoretically and experimentally analyzed, identifying the validity and applicability fields of each one depending on profile's geometry. [ABSTRACT FROM AUTHOR]

This paper presents an overview of alternative methods of production of enhanced performance Al-based alloys components for critical areas. In particular, a new rheocasting system, suitable for the manufacturing of high performance industrial components has been considered. The aforementioned method allows obtaining component quickly and results a more convenient process, from economical point of view than other innovative processes. Two series of components have been produced with A356 and A357 alloys, then have been heat treated using T5 and T6 treatments. On polished transverse sections of samples the microstructure of the alloy has been observed. Their soundness has been previously certified by non destructive tests. Samples for tensile and three point bending tests have been machined directly from the produced components. On the fractured samples, fracture surface analysis has been performed in order to analyze and evaluate the influence of the process and of the alloy on the fracture behaviour. [ABSTRACT FROM AUTHOR]

In this review paper the challenges that face doping optimization in 3-dimensional (3D) thin-body silicon devices will be discussed, within the context of material science studies, metrology methodologies, process modeling insight, ultimately leading to optimized device performance. The focus will be on ion implantation at the method to introduce the dopants to the target material. [ABSTRACT FROM AUTHOR]

In the context of the European Project on Material Science we have developed a Teaching Learning Sequence (TLS), which is composed by units for teaching thermal conductivity in depth to students. The scientific content has been adapted to students’ conceptions taking into account research results. Units follow the Predict-Observe-Explain strategy and students conduct guided investigations using an enriched learning environment, which consists of extensive use of ICT based tools. Didactically transformed microscopic models depict thermal interactions in iconic, graphic and symbolic forms. Students working in groups, solve problems, explore models and are engaged in classroom discussion on the problem under study, constructing links between evidence and explanations. In this paper the structure of such innovative units is presented and results showing students’ development in scientific understanding are reported. [ABSTRACT FROM AUTHOR]

In this paper, we present the design of a low cost Q-switched Nd: YAG laser micro-machining system for photo masks fabrication. It consists of: Nd:YAG laser source, beam delivery system, X-Y table, PC, The CCD camera and TV monitor. The synchronization between the laser source and the X-Y table is realised by NI PCI-7342, the two axis MID-7602 and LabVIEW based program. The first step of this work consists of engraving continuous and discontinuous lines on a thin film metal with a 100 μm resolution by using the YG 980 Quantel Q-switched Nd:YAG laser. [ABSTRACT FROM AUTHOR]

In this paper, we present a 1D Particle in Cell with Monte Carlo Collisions model, developed in order to calculate the energy balance in a micro-discharge, under conditions similar to those of a Plasma Display Panel (PDP) cell. The discharge takes place in a xenon-neon (10%–;90%) mixture at 560 torr and for a gap length of 100 μm. The model is used to analyze in details the energy deposition during the discharge pulse. The results show the amount of energy dissipated by ions (collisions in the gas and on the cathode), by electrons (excitation of the different electronic states, ionization), and their variations with the applied voltage. This model will be used in the future to test the approximations of the fluid models which are generally used to optimize PDP operating conditions, and to check whether or not fluid models can correctly predict the trends in the variations of the energy balance with parameters such as voltage, pressure, gas mixture. [ABSTRACT FROM AUTHOR]