Structural Analysis And Topology Optimization Design For Bandwidth Extension of Magnetoelectric Seismometer

Magnetoelectric seismometers can measure earthquake information and play an important role in earthquake monitoring. Aiming at the wider effective frequency bandwidth of magnetoelectric seismometers, a novel seismometer based on topology optimization structural pendulum is reported. The topology optimization of leaf spring structure in magnetoelectric seismometer is designed, the natural frequency and spurious frequency characteristics of the novel seismometer are analyzed. Based on variable density theory, the Solid Isotropic Material with Penalization (SIMP) model of the seismometer is established, and the Method of Moving Asymmetric (MMA) is adopted to obtain the optimal topology structure. The finite element analysis using ANSYS shows that novel seismometer after topology optimization structure is characteristic with lower natural frequency and higher spurious frequency than that of before optimization seismometer. The real vibration experimental results indicate that after topology optimization, the effective frequency bandwidth of seismometer is increased by 55.50%, improving from [1s, 51Hz] to [4s, 78Hz].

Leveraging Flow Regeneration in Individual Energy-Efficient Hydraulic Drives

The current demand for energy efficiency in hydraulics directs towards the replacement of centralized, valve-controlled actuators with individual, throttleless drives. The resulting solutions often require an undesirable sizing of the key components to expand the system’s operating region. Using flow regeneration (i.e., shortcutting the actuator’s chambers) mitigates this issue. Such an option, already stated for individual drives, lacks an in-depth analysis from the control perspective since the dynamic properties are changed (e.g., the natural frequency is decreased to about 60% of the original value). Therefore, this research paper studies a representative single-pump architecture arranged in a closed-circuit configuration. Linear control techniques are used to understand the system dynamics and design a PI-control algorithm that also adds active damping. The outcomes are validated via high-fidelity simulations referring to a single-boom crane as the study case. The results encompassing diverse scenarios indicate that flow regeneration is only interesting in those applications where the dynamic response is not demanding. In fact, the lower natural frequency reduces the system’s bandwidth to about 69% of the original value and affects the closed-loop position tracking drastically. This poor performance becomes evident when medium-to-high actuation velocity is commanded with respect to the maximum value.

Dynamic Behavior of T-beam Resonator With Repulsive Actuation

We introduce a MEMS resonator that uses a "T"-shape beam driven by repulsive force, of which the first advantage is to avoid pull-in instability; thus, high enough voltages can be applied to the MEMS system to tune the center frequency. A T-beam model is derived from the beam-paddle hypothesis, and theoretical analysis regarding both static and dynamic behaviors, including primary resonance and secondary resonance, is conducted. This study shows an electrostatic T-beam resonator's feasibility based on repulsive force and outlines its advantages over a traditional cantilever beam resonator. Additional micro-paddle to the micro-beam means larger surface for absorption of targeted analytes and lower natural frequency, but higher resonant responses. We present a thorough analysis of primary and parametric resonances, which can enhance the system signal-to noise ratio and response time. This design enables potential applications in MEMS mass-sensors, where a large area for attachment and a high resolution are often vital.

Research on the Dynamic Compensation Method of the Shock Wave's Evaluation Pressure Sensor

Due to the steep and changing fast rising edge of explosion shock wave signal, it asks for good dynamic characteristic of sensor and test system. As far as the development of the sensor level, they are difficult to achieve dynamic characteristic requirement of approximate distortionless transmission, so cause a large dynamic error in the actual test. This paper, aiming at providing theoretical support for technology guarantee and service of the shock wave testing system of national shooting range, conducts a research on the method of dynamic characteristic compensation of pressure sensor facing the power evaluation of the blast shock wave. The research proposes and studies the filter design method of dynamic compensation of pressure sensor based on PFQPSO (the progressive function quantum-behaved particle swarm optimization) algorithm, which belongs to inverse modeling. The dynamic compensation can be realized without knowing the model of sensor, so the extra error caused by dynamic modeling of sensors can be avoided. using 8510 series sensor can be used with lower natural frequency and lower measurement range from Endevco Company, this research has had experiment and modeling on the dynamic characteristics of shock tubes as well as design of dynamic compensation filter. Based on the analysis and confirmation, this study illustrates the possibility and effectiveness of this method.

Research on the Dynamic Compensation Method of the Shock Wave's Evaluation Pressure Sensor

Due to the steep and changing fast rising edge of explosion shock wave signal, it asks for good dynamic characteristic of sensor and test system. As far as the development of the sensor level, they are difficult to achieve dynamic characteristic requirement of approximate distortionless transmission, so cause a large dynamic error in the actual test. This paper, aiming at providing theoretical support for technology guarantee and service of the shock wave testing system of national shooting range, conducts a research on the method of dynamic characteristic compensation of pressure sensor facing the power evaluation of the blast shock wave. The research proposes and studies the filter design method of dynamic compensation of pressure sensor based on PFQPSO (the progressive function quantum-behaved particle swarm optimization) algorithm, which belongs to inverse modeling. The dynamic compensation can be realized without knowing the model of sensor, so the extra error caused by dynamic modeling of sensors can be avoided. using 8510 series sensor can be used with lower natural frequency and lower measurement range from Endevco Company, this research has had experiment and modeling on the dynamic characteristics of shock tubes as well as design of dynamic compensation filter. Based on the analysis and confirmation, this study illustrates the possibility and effectiveness of this method.

A Novel Full Stressed Energy Harvester with Varied Thickness

This study developed a novel full stressed energy harvester composed of a cantilever with varied thickness in the length direction to harvest energy from ambient vibrations. This harvester owns a higher efficiency of energy harvesting when compared with the harvester of a uniform cross section, since the maximum bending stress is constant in each cross section. The current available models for cantilever harvesters are inapplicable to the new improved fully stressed harvester due to its unique shape. By employing Rayleigh-Ritz method, a corresponding governing equation is hence developed to model the full stressed harvester for estimating the efficiency. The influence of the geometry on the generated electric power is also discussed for the full stressed harvester. The results show that the full stressed harvester can double the electric power generated by the uniform harvester, and the full stressed harvester has a lower natural frequency.

THE ANALYSIS OF LIQUEFACTION PHENOMENON OF THE FLEXIBLE PAVEMENT USING SEISMIC MONITORING EQUIPMENT

ABSTRACT: Liquefaction phenomenon is generally caused by high dynamic vibrations in a very fast duration. This article investigated the behavior of dynamic vibrations caused by vehicles on the road. This study employed the HVSR (Horizontal Vertical Spectral Ratio) with an accelerometer. The result of dynamic vibration generated by the passing vehicle or the micro tremor / micro seismic vibration was recorded by seismic monitoring devices. This seismic monitoring equipment converted vibration into natural frequency (f0) and amplification (A0) using Geopsy software. The result of HVSR (Horizontal Vertical Spectral Ratio) was the soil vulnerability index (Kg). The results of this study indicated that the three parameters above were then analyzed with the assumption that if the amplification value (A0) was higher and associated with a lower natural frequency value (Æ’0) with a high vulnerability index (Kg), then the area had the potential liquefaction, with laboratory research results in the form of granular gradation testing as the supporting data. Therefore, the results of the analysis and the laboratory can concluded that the three research locations have the potential liquefaction. ABSTRAK: Fenomena pececairan umumnya disebabkan oleh adanya getaran dinamik tinggi dalam tempoh yang sangat cepat. Artikel ini mengkaji fenomena getaran dinamik yang disebabkan oleh kenderaan di jalan raya. Kajian ini menggunakan HVSR (Nisbah Spektral Menegak Mendatar) dengan pecutan. Hasil getaran dinamik yang dihasilkan oleh kenderaan yang melalui atau gegaran mikro / mikro getaran seismik dicatatkan oleh alat pemantauan seismik. Peralatan pemantauan seismik ini mengubah getaran ke frekuensi semula jadi (f0) dan amplifikasi (A0) menggunakan perisian Geopsy. Hasil HVSR (Nisbah Spektral Vertikal Mendatar) adalah indeks kelemahan tanah (Kg). Keputusan kajian ini menunjukkan bahawa ketiga-tiga parameter di atas kemudian dianalisis dengan anggapan bahawa jika nilai amplifikasi (A0) lebih tinggi dan dikaitkan dengan nilai kekerapan semulajadi yang lebih rendah (Æ’0) dengan indeks kelemahan tinggi (Kg), maka kawasan mempunyai potensi pencairan, dengan hasil penyelidikan makmal berupa pengujian gradasi granular sebagai data pendukung. Oleh itu, hasil analisis dan makmal dapat menyimpulkan bahawa tiga lokasi penyelidikan mempunyai potensi adanya pececairan.

Influence of structural imperfections—twisting and distortion—on the vibrational behavior of carbon nanotubes

Several types of carbon nanotubes in their perfect and imperfect form were simulated, and their vibrational behavior was studied by performing computational examinations with fixed-free boundary conditions. Both computational and analytical results were compared in the case of perfect tubes. Afterward, three kinds of imperfections, that is, twisting angle, z-distortion along the longitudinal axis and xy-distortion along the radial axis, were introduced to the structure of perfect carbon nanotubes, and the natural frequencies of imperfect carbon nanotubes were numerically evaluated and compared with the behavior of the perfect ones. It was concluded that the existence of any type of imperfection in the structure of carbon nanotubes leads to a lower natural frequency and, as a result, lower vibrational stability. However, this trend was more visible for the carbon nanotubes with higher chirality.

The Influence of Bolt Layout Form to the Dynamic Stiffness of the Column

In the case of the column materials to determined, the lower natural frequency of column is determined by the number of coupling bolts and bolt arrangement. In this paper, by three-dimensional modeling software of Solidwork column model of hobbing is set up, then by using ANSYS finite element analysis software. The initial four order natural frequency to the different number of connection bolts and the different arrangement of bolt are respectively calculated. After the initial four order natural frequency are contrasted, we conclude that in the case of merely considering dynamic stiffness this study reach it is the most reasonable to select 8-12 bolts in the hobbing of YKQ31300, and different bolt arrangement of effects on the dynamic stiffness of the column is very small and can be ignored.

Monitoring Changes in the Soil and Foundation Characteristics of an Offshore Wind Turbine Using Automated Operational Modal Analysis

This paper will show the first results of a long term monitoring campaign on an offshore wind turbine in the Belgian North Sea. It will focus on the vibration levels and resonant frequencies of the fundamental modes of the support structure. These parameters will be crucial to minimize O&M costs and to extend the lifetime of offshore wind turbine structures. For monopile foundations for example, scouring and reduction in foundation integrity over time are especially problematic because they reduce the fundamental structural resonance of the support structure, aligning that resonance frequency more closely to the lower frequencies. Since both the broadband wave energy and the rotating frequency of the turbine are contained in this low frequency band, the lower natural frequency can create resonant behavior increasing fatigue damage. Continuous monitoring of the effect of scour on the dynamics of the wind turbine will help to optimize the maintenance activities on the scour protection system. To allow a proper continuous monitoring during operation, reliable state-of-the-art operational modal analysis techniques should be used and these are presented in this paper. The methods are also automated, so that no human-interaction is required and the system can track the natural frequencies and damping ratios in a reliable manner.