The advanced structural materials for living beings implants

The paper deals with development of bioinert and bioactive biomaterials, different application of structural materials, including metallic materials, nanomaterials, nanostructured materials, biomaterials, ceramics, polymers, hybrid materials, functional graded materials, composites. Also are discussed multi-functional engineering materials with gradient properties, engineering materials for challenging application conditions, including aggressive environment and lightweight, multi-material (hybrid) systems where advanced materials are combined with more conventional / structural materials and materials production or joining technologies. Interdisciplinary approach to biomedicine materials research and production is very promising and horizontal cooperation of different national technology platforms is discusse

Vibratory stress relieving – it’s advantages as an alternative to thermal treatment

The aim of this study was to investigate the use of vibration to reduce the residual stress resulting from the welding process. Butt weld joints were subjected to vibration immediately after welding. The existing methods for relieving residual stress from welds are: mechanical, heat and electromagnetic. The mechanical method may be performed by hammering or vibration. The heat method consists of heating the whole welded piece or each weld, one by one. The electromagnetic method uses the electromagnetic hammer technique. In the heat treatment the part is heated until the yield point is reduced to less than the residual stress, which in turn causes local plastic distortion, decrease of the residual stress intensity and reduction of hardness. The vibration method introduces energy into the part by means of vibrations. For the stressed atomic structure there is no difference between the energy introduced through heat and the energy introduced through vibrations. The applied energy reorganizes the crystalline structure, relieving stress and stabilizing the piece, without distortion [1]. The article deals with reducement of welding stresses with the help of vibration treatment and to compare it with the classical heat treatment. The experiments were performed by a welding of structural low-alloy steel 16GS plates. Therefore the result is submitted by the mechanical tests and metal magnetic memory control. Several specimens, after welding and vibrotreatment, were cut off the welded plates and submitted for tensile, impact, hardness tests and metallographic analysis. The specimens, which were treated by vibration treatment, had strength and elasticity properties changed similarly as after the heat treatment. The metal magnetic memory test shows that this control method is suitable for evaluation of residual welding stresses variations after the weldment’s treatmen

The influence of mechanical vibrations on properties of Ni-based coatings

This article reports on research work that was undertaken on Ni-based thermally- sprayed and fused coating deposited on steel substrate. Mechanical vibrations were introduced during fusing process and the impact of vibrations on the properties and microstructure of coatings was investigated. Microstructures of sprayed and sprayed–fused coatings were compared including evaluation of porosity. The microstructure of sprayed coating consists of partly melted and unmelted particles. A lot of voids are present between the splats. The assprayed coating is bonded to the substrate mechanically or by adhesion. The porosity was significantly reduced and strong metallurgical bond between the fused coating and substrate was formed after fusing operation. The hardness and microhardness of different zones of coatings as well as wear resistance were assesse

On the generation and the nonlinear dynamics of X-waves of the Schroedinger equation

The generation of finite energy packets of X-waves is analysed in normally dispersive cubic media by using an X-wave expansion. The 3D nonlinear Schroedinger model is reduced to a 1D equation with anomalous dispersion. Pulse splitting and beam replenishment as observed in experiments with water and Kerr media are explained in terms of a higher order breathing soliton. The results presented also hold in periodic media and Bose-condensed gases.Comment: 18 pages, 6 figures, corrected version to be published in Physical Review

Spontaneously generated X-shaped light bullets

We observe the formation of an intense optical wavepacket fully localized in all dimensions, i.e. both longitudinally (in time) and in the transverse plane, with an extension of a few tens of fsec and microns, respectively. Our measurements show that the self-trapped wave is a X-shaped light bullet spontaneously generated from a standard laser wavepacket via the nonlinear material response (i.e., second-harmonic generation), which extend the soliton concept to a new realm, where the main hump coexists with conical tails which reflect the symmetry of linear dispersion relationship.Comment: 5 pages, 4 figures, submitted for publicatio

Influence of vibratory stress relief on residual stresses in weldments and mechanical properties of struktural steel joint

The welding process can join two similar materials with a bond that has mechanical properties comparable to the original material. Unfortunately, this process induces residual stresses in the weldment, which, if left untreated, can cause distortion of the part, premature fatigue failure or cracking along the weld. A post-weld heat treatment is the traditional method of relieving these stresses, but is costly and a time consuming process. Heat treatment is required for weldments, which have heavy fatigue loading since the post-weld heat treatment reduces the residual stresses in the weldment and generates more uniform mechanical properties. Vibratory stress relief (VSR) techniques could be used to substitute the heat treatment for these types of weldments and save time and money. The purpose of this paper is to provide a brief overview of the generation, measurement, and reduction of residual stresses. Residual stresses in the weld bead were measured by means of X-ray diffraction, ultrasonic technique and hole drilling methods. In addition, welded specimens were subjected to mechanical testing with purpose of determination of VSR effect on weld and heat-affected zone meta

Three-Wave Modulational Stability and Dark Solitons in a Quadratic Nonlinear Waveguide with Grating

We consider continuous-wave (CW) states and dark solitons (DSs) in a system of two fundamental-frequency (FF) and one second-harmonic (SH) waves in a planar waveguide with the quadratic nonlinearity, the FF components being linearly coupled by resonant reflections on the Bragg grating. We demonstrate that, in contrast with the usual situation in quadratic spatial-domain models, CW states with the phase shift between the FF and SH components are modulationally stable in a broad parameter region in this system, provided that the CW wavenumber does not belong to the system's spectral gap. Stationary fundamental DSs are found numerically, and are also constructed by means of a specially devised analytical approximation. Bound states of two and three DSs are found too. The fundamental DSs and two-solitons bound states are stable in all the cases when the CW background is stable, which is shown by dint of calculation of the corresponding eigenvalues, and verified in direct simulations. Tilted DSs are found too. They attain a maximum contrast at a finite value of the tilt, that does not depend on the phase mismatch. At a maximum value of the tilt, which grows with the mismatch, the DS merges into the CW background. Interactions between the tilted solitons are shown to be completely elastic.Comment: 10 pages, 12 figures; Journal of Optics A, in pres