Applied Mechanics and Materials Vol. 590

Abstract: This paper presented a magnetic pendulum to scavenge the human kinetic energy from arm motion and convert the kinetic energy to electrical energy for portable electronic devices. The harvester mainly consisted of a stator, a rotor and a control circuit. The stator was set of electric coils while the rotor is an eccentric mass made of permanent magnet. A torsion spring was also added onto the rotor such that the motions in both horizontal and vertical directions can be effectively harvested. The energy harvester could be worn on human arm. When the arm was in motion, the device would then generate power. The paper presented a detailed kinematical analysis and power conversion analysis. As a typical case, the device was 40 mm in diameter and 50 g in weight, the simulation showed that when worn on wrist, it could generate about 30 mW during normal walking.

Abstract: Boundary layers are affected by a number of different factors. Transition of the boundary layer is very sensitive to changes in geometry, velocity and turbulence levels. An understanding of the flow characteristics over a flat plate subjected to changes in geometry, velocity and turbulence is essential to try and understand boundary layer transition. Experiments were conducted in Low Turbulence wind tunnel (LTWT) at Northwestern Polytechnical University (NWPU), China to understand the effects due to changes in geometric profiles on boundary layer transition. The leading edge of the flat plate was changed and several different configurations ranging from Aspect Ratio (AR) 1 to 12 were used. Turbulence level was kept constant at 0.02% and the velocity was kept at default value of 30 m/s. The results indicated that as the AR increases, boundary layer thickness reduces at the same location along the plate. The displacement thickness shows that the fluctuations increase with an increase with AR which denotes the effect of leading edge on turbulence spot’s production. For AR≥4, an increase in AR led to an elongation of the transition zone and a delay in transition onset. Nomenclature

Abstract: Sandwich geometries, mainly panels and beams are widely used in several transportation industries, namely aerospace, aeronautic and automotive. Sandwich geometries are known for their advantages in structural applications: high specific stiffness, low weight, and possibility of design optimization prior to manufacturing. This study aims to know the influence of the number of reinforcements (ribs), and of the thickness on the mechanical behavior of sandwich panels subjected to bending and torsion loads separately. In this study, 3 geometries are compared: simple web-core beam, corrugated core, and honeycomb core. The last 2 are asymmetric, due to the use of odd number of ribs. The influence of the geometry on the results is discussed, by means of a parameter that establishes a relation between the stiffness behavior and the mass of the object. It is shown that the all relations are non-linear, despite the elastic nature of the analysis, by means of the application of loads with low intensity.

Abstract: The effect of stress wave propagation on dynamic response of square tube was investigated by the experimental and numerical simulation methods in the present paper. The square tubes were subjected to the axial impact by split Hopkinson pressure bar. And the deformation process of each square tube was recorded by a high speed camera. Typical dynamic plastic buckling phenomena were observed in the experiments. And the numerical calculation of the experimental load case was conducted to analyze the effect of the stress wave propagation on the initial buckling of the square tube. The results show that there is obvious stress wave propagation in the square tube before the buckling of the square tube. And the initial buckling starts from the rear end of the tube due to the propagation of the stress wave. The relation between the stress wave propagation and initial buckling of the square tube was also discussed.

Abstract: In this paper, the wind-induced response of the ADSS is analyzed when the high-speed trains pass by. The wind flow field of the high-speed train is simulated based on the three-dimensional Reynolds-averaged Navier–Stokes equations, combined with the k-ε turbulence model. The result is shown that the wind load acting on the ADSS is quite low and the stress of the line clamp increases a little.

Abstract: The dynamic responses of the seated body exposed to vertical vibration are investigated at the two driving-points, formed by the upper body-backrest and buttock-pan interfaces in terms of force-motion relationships. The dynamic interactions of the seated body are characterized in the laboratory in terms of apparent masses at the two driving-points under white noise and track-measured random vertical vibration in the 0.5-40 Hz frequency range. The experiments were performed with 24 adult subjects seated on an idealized rigid seat, representing an automotive seat geometry. The vertical and fore-aft forces at the body-pan and body-backrest interfaces were measured to determine the apparent mass responses at the two driving-points. The results clearly revealed significant dynamic interactions of the upper body with the back support. The results also showed considerable influences of the vibration magnitude, body mass and the subjects’ hands position on the measured biodynamic responses.

Abstract: (TiAlZrNb)N hard reactive films are prepared by multi-arc ion plating technology using the combination of Ti-18Al-11Zr (at%) and Ti-25Nb (at%) alloy targets. The high speed steel (HSS) is adopted as substrate. The surface and cross-fracture morphology, the surface compositions and the phase structures of the as-deposited (TiAlZrNb)N films are observed and measured by scan electronic microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The mechanical properties including micro-hardness, adhesion between film and substrate, friction and wear resistance and thermal shock resistance of the as-deposited (TiAlZrNb)N films are systemically investigated. The effects of deposition bias voltage and the addition of Nb element on the as-deposited (TiAlZrNb)N films are discussed. It is revealed that the comprehensive performances including micro-hardness, adhesion and friction resistance can be achieved by the (TiAlZrNb)N hard reactive film with deposition bias voltage of 150V.

Abstract: The algebraic model, one-equation model, two equation models are Analyzed in the paper. Focusing on the k-ε turbulent model contains (the standard k-εturbulence model, RNG k-εmodel, Realizable k-ε model), and the origin of the shear stress transport model, Reynolds stress equation model on mathematical and physical model is discussed.the advantages and disadvantages of each model is Pointed out ,And the future development direction of turbulent model and improvement measures are proposed on the paper.

Abstract: In this paper, we integrated use hydraulics, seepage flow mechanics, rock mechanics, and finite element simulation analysis and other methods to study the rock fragmentation mechanism of high pressure water jet. We make tensile stress - crack expansion comprehensive rock fragmentation model for the screw drilling of high pressure water jet. We make finite element simulation according to the mechanism of integrated model of high pressure water jet process, to analysis the internal rock stress distribution and external rock stress distribution of the fluid, and come to the reasonable number of high-pressure water jet nozzle hole. It is verified by the high pressure water jet breaking rock inside experiments of tensile stress - comprehensive rock fragmentation fracture expansion model, summarizes the law of high pressure water jet breaking rock, and we get to know reasonable drilling mode of the high pressure water jet is screw drilling with pitch of 120mm. At present there are two main types of the micro mechanism of the high pressure water jet. One is stress and tensile damage, because of the action produced by stress wave of the high pressure water jet impacting on rock, which mainly makes the tensile failure of rock; another one is crack expansion damage, under the effect of quasi static pressure radiation of water jet, the coupling effect between water shooting jet and rock pore skeleton, which make the rock pore, throat, and micro cracks expanding gradually, eventually the macro damage.

Abstract: Orifice plate energy dissipater, as a kind of effective energy dissipater with characteristics of economic, has become welcomed more and more by hydraulics researchers. Although many researches have been conducted on orifice plate’s hydraulic characteristics, there are many other issues, which are closely related with orifice plate’s energy loss and cavitations, needed to be solved. Some issues on orifice plate’s hydraulic characteristics have been put forward in this paper so as to strengthen research in this field.