Discussion On Failure Behavior of Piping Systems Under Extremely Large Seismic Loads in BDBE

To investigate the failure behavior of piping systems under severe seismic loads considering beyond design basis event (BDBE), an experimental approach to use pipes made of simulation materials was applied. "Simulation material" means the substitute material for steel to realize the structural experiment by the existing testing facilities. The simulation materials adopted in this study were pure lead (Pb) or lead-antimony (Pb-Sb) alloy. Using pipe elbows made of simulation materials, static loading tests on elbows and shaking table tests on simple piping system models composed of one or two elbows and an additional mass were conducted. From the static loading tests, the load-deflection relationship of an elbow under monotonic loading was obtained as well as the fatigue failure modes under cyclic loading depending on the several cyclic displacement levels. From the shaking table tests, several failure modes were obtained, namely, "Collapse by self-weight", "Collapse by a few cycles of input", "Ratchet and subsequent collapse", "Overall deformation", and "No failure". It was considered that the occurrence of these failure modes was affected by the ratio of the input frequency to the specimen's natural frequency, the ratio of additional mass weight to the limit mass weight, the configuration of the specimen, and the input acceleration level. The experimental results indicated that it was crucial to understand the structure's ultimate behavior when treating BDBE, and that the research approach using simulation material is effective to investigate the ultimate behavior of piping systems.

In Situ Formation of Super-Earth/Sub-Neptune Driven by the Planetary Rotation

Kepler’s observation shows that many of the detected planets are super-Earths. They are inside a range of critical masses overlapping the core masses (2–20 M ⊕), which would trigger the runaway accretion and develop the gas giants. Thus, super-Earths/sub-Neptunes can be formed by restraining runaway growth of gaseous envelopes. We assess the effect of planetary rotation in delaying the mass growth. The centrifugal force, induced by spin, will offset a part of the gravitational force and deform the planet. Tracking the change in structure, we find that the temperature at the radiative–convective boundary (RCB) is approximate to the boundary temperature. Since rotation reduces the radiation energy densities in the convective and radiative layers, RCB will penetrate deeper. The cooling luminosity would decrease. Under this condition, the evolutionary timescale can exceed the disk lifetime (10 Myr), and a super-Earth/sub-Neptune could be formed after undergoing additional mass-loss processes. In the dusty atmosphere, even a lower angular velocity can also promote a super-Earth/sub-Neptune forming. Therefore, we conclude that rotation can slow down the planet’s cooling and then promote a super-Earth/sub-Neptune forming.

Analysis of Sound Absorption Characteristics of Acoustic Ducts with Periodic Additional Multi-Local Resonant Cavities

With the aim of applying various Helmholtz resonant cavities to achieve low-frequency sound absorption structures, a pipe structure with periodic, additional, symmetrical, multi-local resonant cavities is proposed. A thin plate with additional mass is placed in the cylindrical Helmholtz resonant cavity structure to form a symmetric resonant cavity structure and achieve multi-local resonance. The simulation results show that the periodic structure proposed in this paper can produce multiple, high acoustic transmission loss peaks and multiple lower broadband sound absorption frequency bands in the low-frequency range. In this paper, this idea is also extended to the Helmholtz resonant cavity embedded with multiple additional mass plates. The results show that the periodic arrangement of the multi-local resonant symmetric cavity inserted into multiple plates with mass can significantly increase its transmission loss and show a better performance on low-frequency sound absorption characteristics.

Modeling and Optimization Analysis for Base-Excited Magnetostrictive Vibration Harvester

Due to the low vibration frequency and weak vibration energy in natural environment, the vibration energy harvester is faced with the problem of low power and low adaptability and becoming particularly difficult in actual conditions. It is necessary to improve the harvesting capacity and efficiency by optimizing the parameters of the harvester, making full use of the energy of low and unstable atmospheric vibrations. In this paper, a mathematical model is established for the cantilever magnetostrictive vibration harvester under the base excitation, including the mechanical deformation of the composite beam, and the electromagnetic results produced thereof. The mechanical-magneticelectric energy conversion relationship is duly taken into account. The additional weight, coil parameters, external resistance and other parameters of the harvester are optimized and analyzed through numerical simulation. In addition, the theoretical results are analyzed and discussed via comparison with experiments. Finally, the effects of the above factors are assessed, which allows us to obtain the optimal winding length, number of turns of the coil, and optimal tip additional mass. The experiment result shows that the optimized magnetostrictive harvester can output 12.07[Formula: see text]mW power to the external resistor under the condition of 1[Formula: see text]g acceleration mechanical vibration, with normalized power density reaching 40.2[Formula: see text]mW/cm3/g. Moreover, the optimized magnetostrictive harvester can successfully supply power for the LED display screen of the temperature sensor and a low-power thermometer.

Analysis of the usability of rolling resistance measurement methods to study the mechanisms of some wheelchairs

Reducing the driving force when propelling a wheelchair, e.g. through mechanical gears, is beneficial for people using wheelchairs. This makes it possible to overcome terrain obstacles that would be otherwise impassable with a classic drive system. However, the disadvantage of additional mechanisms supporting the propulsion of the wheelchair is usually the additional mass, ultimately increasing the rolling resistance. The article presents methods of measuring the rolling resistance – widely developed in the automotive industry – in terms of measuring the rolling resistance of wheelchairs. Innovative methods have been demonstrated to measure the rolling resistance on various surfaces and with the use of various drive mechanisms. The developed methods also enable the determination of the rolling resistance coefficient. The methods used are innovative and are subject to patent protection prepared by the authors in recent years. The results of the respondents allow to compare the measurement accuracy of the developed methods and show that the second method (being a simplification of the first method) is characterized by better accuracy.

Nonlinear Suppression of a Dual-Tube Coriolis Mass Flowmeter Based on Synchronization Effect

Nonlinear interference components exist in the output signals of dual-tube Coriolis mass flowmeters (CMFs) which affect the sensitivity and accuracy of the devices. This nonlinearity still appears under zero flow, which is manifested when the output signal contains a frequency doubling signal. This study (1) investigated an additional-mass method to suppress the nonlinear frequency doubling phenomenon, (2) established a coupling system vibration model with additional mass, built a dynamic differential equation for the vibration of the double-beam coupling system from the Lagrange equation, (3) obtained amplitude frequency information using a fourth-order Runge–Kutta method, (4) determined the suppression effect of the additional mass on the nonlinear frequency doubling phenomenon, and (5) experimentally verified the CMF. The results showed that the base coupled the vibrations of two beams, and the symmetric additional mass suppressed the nonlinear frequency doubling phenomenon, thus suppressing low or high frequencies. Also, the effect of pipeline defects simulated under asymmetric additional mass was obtained through numerical analysis and experimental data. Flowmeters with a required measuring frequency range had the optimal suppression effect on nonlinear frequency doubling and provided theoretical guidance for the nondestructive testing of measuring tubes.

Modeling of Dielectric Electroactive Polymer Actuators with Elliptical Shapes

Dielectric electroactive polymers have been widely used in recent applications based on smart materials. The many advantages of dielectric membranes, such as softness and responsiveness to electric stimuli, have lead to their application in actuators. Recently, researchers have aimed to improve the design of dielectric electroactive polymer actuators. The modifications of DEAP actuators are designed to change the bias mechanism, such as spring, pneumatic, and additional mass, or to provide a double cone configuration. In this work, the modification of the shape of the actuator was analyzed. In the standard approach, a circular shape is often used, while this research uses an elliptical shape for the actuator. In this study, it was shown that this construction allows a wider range of movement. The paper describes a new design of the device and its model. Further, the device is verified by the measurements.

Моделювання течії в співвісному гвинтовентиляторі з управлінням примежовим шаром

The development and improvement of turboprop engines are one of the important tasks of modern aircraft engine building. Propeller performance significantly affects the overall efficiency of turboprop engines. An important issue is to increase the trust of the propeller or propfan. In this matter, promising energy methods for increasing lift deserve special attention. Energy methods for increasing the lift force are based on the use of additional energy from the power plant to improve the flow around the blade and increase its bearing properties. The purpose of this work is to assess the influence of the boundary layer control on the blades of a coaxial propfan on the thrust. A coaxial propfan was chosen as the object of research. The rotor fan consists of two rows of blades, the first row has eight blades, the second - six. The peripheral diameter of the blades of the propfan is the same and amounts to 4.5 m. The cruise mode of operation was selected for the study. Modeling the flow in a coaxial propfan was based on the solution of the Navier-Stokes system of equations, which was closed by the SST Gamma Theta Transition model of turbulent viscosity. The computational grid consisted of 20 million cells, type-block, structured and unstructured with an adaptation of the boundary layer. In this study, an active boundary layer control method was chosen. The boundary layer was controlled only on the blades of the first row of the propfan. In the peripheral region of the blade, an additional mass of air was blown out through the slot, at a distance of 70 % of the profile chord. Blowing out a thin jet near the blade wall to increase the flow energy serves as an effective means of controlling the flow separation and increasing the bearing capacity of the propfan blade. Analysis of the simulation of the flow in a propfan with control of the boundary layer showed that the addition of energy to the boundary layer contributes to the filling of the velocity profile in the boundary layer, leads to a decrease in resistance and an increase in the thrust of the propfan. The results of the study showed that for the studied scheme of blowing out an additional mass of air on the propeller blades, it is possible to increase the thrust force up to 100 N. In the future, it is planned to investigate other schemes for controlling the boundary layer to increase the thrust of the coaxial propfan.