Papers by Keyword: Shock Wave

Abstract: Ballistic performance has been studied by impacting a long rod projectile into a bulk glass material and a layered specimen. The shock wave interaction on the material boundaries showed that it greatly influences the fracture configuration of glass material. A high speed photographic technique was applied in the experiment to observe the shock wave interaction and damage evolution in the bulk material. Transparent BK7 glass was used as the main material to observe the dynamic fracture phenomena. The depth of penetration (DOP) was measured to assess the ballistic efficiency of the bulk specimen compared with specimens that consisted of selected inter-layer materials, specifically rubber and a steel plate. The obtained results show that the use of a lower impedance material as an inter-layer is effective to enhance the ballistic performance while reducing the shock amplitude and delaying the wave propagation. These findings are in good agreement with the results of a numerical analysis using AUTODYN.

Abstract: In the Army of the Czech Republic, the protective structure design is currently regulated by a military standard Žen 2-1/1, mainly for buried structures and against nuclear loads. As the nature of current armed conflicts suggests, it would be more appropriate to design above-ground protective structures exposed to the effects of direct or indirect fire weapons. The paper describes a search for an ideal above-ground structural shape exposed to an airblast. Several shapes were designed and their behavior under a typical airblast loading was tested using ANSYS software. As a result of the analysis, the most suitable shape of a protection structure was designed.

Abstract: The results of mathematical modeling of the dynamic interaction of a plane longitudinal shock wave with a plane interface between two isotropic nonlinear elastic materials are presented. The mechanical properties of deformable solid are given by the elastic Murnaghan model. The dynamic processes of deformations distribution are studied in the framework of the theory of singular surfaces. The numerical solutions of the corresponding self-similar problem with strong and weak deformations discontinuities in the reflected and refracted wave packages have been obtained on the basis of the developed scheme of computational experiment.

Abstract: The purpose. To work out an efficient technology and develop production of supersolid metal-ceramic powders and tools of high quality from processed raw materials.Methods. To stimulate the processes of defect formation and destruction of tungsten containing alloys under conditions of the effect of high pressure gradients and loading rate revivified by shock waves of different intensity.Results. This is the first time explosion energy has been applied to grind hard alloys in cylindrical capsules compared to the traditional methods of recycling. The material obtained in the capsules of impact compression was exposed to finely dispersed structure refinement in drum-type grinding mills with duration 20 times as short as that for the current grinding technology which allowed decreasing energy consumption for grinding process by 7.75 megawatt for one aggregate onlyScientific novelty. Shock waves generated by detonation of condensed explosives have been originally used as tools to stimulate the processes of defect formation of cemented carbide alloys at different scale level. Conditions of preserving the shocked product in axial symmetry facilities has been developed and provided.Practical implications. The use of shock waves in the technology of hard alloy revivification is the only possible method of processing large-size solids with significant reduction of energy consumption and quality-assured production.

Abstract: The three-dimensional supersonic turbulent flow in presence of symmetric transverse injection of round jet is simulated numerically. The simulation is based on the Favre-averaged Navier-Stokes equations coupled with Wilcox’s turbulence model. The numerical solution is performed using ENO scheme and is validated with the experimental data that include the pressure distribution on the wall in front of the jet in the plane symmetry. The numerical simulation is used to investigate in detail the flow physics for a range of the pressure ratio . The well-known primary shock formations are observed (a barrel shock, a bow shock, and the system of λ-shock waves), and the vortices are identified (horseshoe vortex, an upper vortex, two trailing vortices formed in the separation region and aft of the bow shock wave, two trailing vortices that merge together into one single rotational motion). During the experiment the presence of the new vortices near the wall behind the jet for the pressure ratio is revealed.

Abstract: With the development of world’s economy, energy shortage gradually appears. Resistance has a great influence on energy consumption. In other words, drag reduction means saving energy. Development of the drag reduction technology plays a very important role to improve the energy efficiency. Therefore, drag reduction technology of jet has become a hot research field. Drag reduction technology of jet is applied on the surface, so as to reduce surface friction resistance. Through analyzing the necessity of energy efficiency increase and jet drag reduction theory improvement, research progress of lateral jet flow technology and drag reduction technology of jet in the field of aircraft are reviewed. Besides, a main trend on the drag reduction technology of jet research is presented.

Abstract: The paper presents a numerical study of the interaction of a shock wave with a protective stopping. It addresses the effect of the type of setting on dangerous stresses emergences under the explosion. The types of setting are evaluated depending on the nature of the load on the sopping. Heavy concrete of B15 grade was taken as the material for evaluation.

Abstract: The construction of objects of critical infrastructures such as a new roads, utility tunnels, communication networks, underground parks and other structures is associated by the way with generation of vibrations in the vicinity of the underground structures, and not only human lives can be lost but also extensive material damage can be expected due to technological and natural hazards based on vibrations. This paper presents the general governing equations for coupled thermo-hydromechanical process in the tunnel surrounds. Modeling and analysis of laminated composite cylinder applied for the objective analysis of shock wave propagation in the soils and possibilities to estimates of the tunnel structure damage.

Abstract: According to the characteristics of mechanical response of titanium alloy, a new constitutive model for ultra-high strain rate deformation in the process of laser shock peening was established. The constitutive model parameters were obtained by the inverse optimization. The propagation characteristic and residual stress-strain distribution under the shock wave were analyzed. The relationship between residual stress and laser power density and laser impacts was indicated via sensitivity analysis of laser parameters. According the above conclusions, the laser shock peening technic on the titanium simulated blades was optimized to obtain the appropriate residual stress distribution. The fatigue test result indicated that the fatigue strength by the optimized technic was improved by 25%, compared to the anterior technic without optimization.

Abstract: Concrete mechanical properties under dynamic load such as blast and impact are very complex. Shock wave propagation law and damage effect in the concrete were studied numerically in the paper by using TNT explosive ignition and growth model, concrete dynamic damage model, and SPH method. And shock wave properties of different mass explosives in the concrete were analyzed with the similarity theory. The result shows that TNT shock wave propagation law meets the internal-blast similarity law. Peak pressure, positive pressure impulse, maximum velocity and maximum acceleration in the concrete decrease with the increase of scaled distance. And time needed for reaching peak pressure increases linearly with the increase of scaled distance. A theoretical basis of structure and protection design for constructions is achieved in the paper.