scholarly journals Dynamic Response of Seismic Dangerous Rock Based on PFC and Dynamics

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Yun Tian ◽  
Linfeng Wang ◽  
Honghua Jin ◽  
Biao Zeng
Keyword(s):  
Dynamic Response ◽  
Low Frequency ◽  
Peak Stress ◽  
Slope Instability ◽  
Dynamic Responses ◽  
Distribution Model ◽  
Distribution Models ◽  
Response Characteristics ◽  
Crack Propagation Process ◽  
The Impact

Rock slope instability by earthquakes results in substantial economic and property losses. The calculation method of interlayer load and stability coefficient of horizontal complex layered rock slopes in high-intensity areas is established from material mechanics, fracture mechanics, and dynamics. The stability of horizontal layered dangerous rock is calculated after combining it with PFC simulation technology to verify the rationality of the calculation in the Wenchuan area of Sichuan Province. The dynamic response characteristics of dangerous rocks under different weathering degrees are also analyzed. The results show that both methods have an excellent early warning effect on earthquake dangerous rocks. Among the PGA amplification factors, Model 1 has a relatively uniform distribution, Model 2 has a zigzag distribution, Models 3 and 4 have a “U”-shaped distribution, and the most severe acceleration dynamic responses are 4-1 and 4-2 rock blocks. The dynamic acceleration response of mudstone is affected by the crack propagation process of the upper sandstone and exhibits a particular elevation amplification effect. The peak stress gradually decreases with the increase in weathering and elevation. The stress change of the inner chain No. 2 in the horizontal x and y directions is severe, and the stress response of the outer chain No. 1 in the vertical z-direction is severe. It recommends that earthquake disaster protection projects should pay attention to the impact of low-frequency (0–10 Hz) and high-frequency (250 Hz) earthquakes on slope stability.

scholarly journals Research on the Influence of Vibrations on the Dynamic Characteristics of AC Contactors Based on Energy Analysis

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 559
Author(s):  
Shuguang Sun ◽  
Jingrui Cui ◽  
Taihang Du
Keyword(s):  
Dynamic Response ◽  
Dynamic Characteristics ◽  
Energy Analysis ◽  
Harmonic Oscillation ◽  
Electrical Energy ◽  
Distribution Model ◽  
Iron Core ◽  
Analysis Model ◽  
Response Characteristics ◽  
The Impact

Aimed at the influence of the vibration environment on the performance degradation of AC contactors, the purpose of this study is to investigate the failure mechanism of AC contactors under vibration conditions. During the closing process of AC contactors, the impact energy of the iron core may change due to the vibration stress, which may have an uncertain effect on the parameters of the dynamic response characteristics of the contact, and affect the working performance and service life of AC contactors. In this paper, a double-E AC contactor is selected as the research object. Based on the calculation of the transient magnetic field of the electromagnetic mechanism, an energy distribution model of the AC contactor is established. Based on this, considering the influence of vibrations and the input electrical energy under different closing phase angles, the energy model of the iron core collision under simple harmonic oscillation is investigated. The steady-state vibration energy at different frequencies and accelerations is calculated, and its influence on the dynamic response parameters of the AC contactor is analyzed. Finally, the simulation model is verified by experimental data. The results show that the energy analysis model can effectively reflect and explain the uncertainty of the dynamic characteristics of AC contactors under vibrations, from the perspective of the mechanism.

In-Plane Dynamic Response Analysis of Hexagonal and Reentrant Honeycombs Under Uniaxial Impact Loading

2017 ◽  
Author(s):  
Zhen Li ◽  
Qiang Gao ◽  
Liangmo Wang ◽  
Jun Tang
Keyword(s):  
Dynamic Response ◽  
Impact Loading ◽  
Impact Resistance ◽  
Peak Stress ◽  
Nominal Stress ◽  
Response Analysis ◽  
Plateau Stress ◽  
Plateau Area ◽  
Stress Curve ◽  
The Impact

To investigate their in-plane dynamic response, a rigid plate with mass was given an initial velocity to impact (square) honeycombs in the X1 and X2 directions, respectively. Firstly, the impact model was built and validated. Then, impact resistance capacity research was conducted. Results showed that each honeycomb performed similarly in X1 and X2 directions, and the reentrant honeycomb usually used smaller displacement and time to absorb the same amount of kinetic energy. Thus, it is better for application if these factors were the main concerns. After that, the nominal stress at the proximal and distal ends were discussed under various impact velocities. It is shown that, under impact loading, the reentrant honeycomb generally showed higher initial peak stress as well as lower plateau stress at both proximal and distal ends. In addition, combining these with the deformation process of honeycombs, it was concluded that the formation of the plateau area of the nominal stress curve is related to the crushing displacement of the impact plate as well as the collapse of cells.

Dynamic Response Characteristics of Underground Powerhouse Caverns for Sandaowan Hydropower Station

2011 ◽  
Vol 382 ◽  
pp. 80-83 ◽  
Author(s):  
Zhen Zhong Shen ◽  
Hua Chun Ren
Keyword(s):  
Seismic Waves ◽  
Low Frequency ◽  
Time History ◽  
Element Model ◽  
Frequency Characteristics ◽  
Dynamic Responses ◽  
Principal Stresses ◽  
Underground Powerhouse ◽  
Response Characteristics ◽  
Set Up

According to the practical situation, the 3-D finite element model of Sandaowan underground powerhouse caverns on Taolai River is set up for analyzing the behaviors under earthquake action. Based on static stress field of the surrounding rock mass, and with the selection of appropriate seismic waves for dynamic time-history analysis method, the dynamic responses of underground powerhouse caverns are analyzed. It is shown that the time-history waveform of dynamic displacement of given points has a very similar variation regularity with that of acceleration, and the wave phases of both are almost synchronous. The dynamic displacements and principal stresses of the given points on rock walls are with the vibration of low-frequency characteristics, the acceleration response is with the vibration of high-frequency characteristics.

Hailstone-induced dynamic responses of pretensioned umbrella membrane structure

2020 ◽  
Vol 24 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Changjiang Liu ◽  
Fan Wang ◽  
Xiaowei Deng ◽  
Song Pang ◽  
Jian Liu ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Membrane Structure ◽  
Impact Analysis ◽  
Impact Load ◽  
Dynamic Responses ◽  
Flexible Structure ◽  
Membrane Material ◽  
Membrane Structures ◽  
Characteristic Points ◽  
The Impact

The membrane structure is a flexible structure, which is easy to vibrate or even relax under dynamic load. Engineering accident analysis shows that the relaxation of membrane structure is more likely to lead to structural failure. In this article, the impact load problem is combined with the flexible structure to analyze the impact of hailstone impact load on the dynamic response of membrane structure. First, the umbrella membrane stretching device was designed and manufactured, and the hailstone impact test was carried out on the umbrella membrane structure with polyvinyl chloride membrane material. Dynamic response data, tension relaxation of side cables and vibration deformation of umbrella membrane structures impacted by hailstones with different sizes and different characteristic points were obtained. In the numerical analysis, the form-finding analysis of umbrella membrane structure is carried out by finite element method, and the transient impact analysis is conducted in LS-DYNA. Finally, the reliability of the research results is verified by comparing the numerical and experimental results. The general laws and conclusions are drawn and the disaster-causing mechanism of membrane structure impacted by hailstone is revealed. On the whole, although the probability of hailstone destroying the membrane material directly is very small, it will relax the membrane structure and affect the safety of membrane structure. The conclusions of this article provide a theoretical basis for the design and maintenance of membrane structures.

scholarly journals Experimental Research on the Impact Environment of Multiplate Cabinet

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Jun Guo ◽  
Shizhang Huang ◽  
Youwei Kang ◽  
Ning Hao ◽  
Hao Xie
Keyword(s):  
Theoretical Analysis ◽  
Frequency Band ◽  
Low Frequency ◽  
Impact Testing ◽  
Central Position ◽  
Response Characteristics ◽  
Single Plate ◽  
Distribution Laws ◽  
Vibration Modal ◽  
The Impact

As an installation and protection device for electrical and electronic components, a shipboard cabinet is a typical multiplate structure. In order to study the impact environment distribution laws of such structures, impact testing was carried out on a shipboard cabinet under four working conditions in this paper. In addition, the impact response characteristics of such a multiplate structure were determined by numerical simulation and theoretical analysis. The impact environments of some pivotal points in cabinet were measured and some laws of dynamic response were found. The impact environment of central position was more severe on a single plate because of the first vibration modal. For different plates, the responses were usually similar at low-frequency band and a little different at high-frequency band. The theoretical analysis of the single degree of freedom oscillator was carried out, and the sensitivity of the response to the different characteristic frequencies was discussed based on the shock spectrum theory. A new method of calculating the response at a special frequency was proposed and verified.

scholarly journals From Remote Sensing to Species Distribution Modelling: An Integrated Workflow to Monitor Spreading Species in Key Grassland Habitats

2021 ◽  
Vol 13 (10) ◽  
pp. 1904
Author(s):  
Walter De Simone ◽  
Marina Allegrezza ◽  
Anna Rita Frattaroli ◽  
Silvia Montecchiari ◽  
Giulio Tesei ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Species Distribution ◽  
Species Distribution Model ◽  
Abiotic Factors ◽  
Natura 2000 ◽  
Distribution Model ◽  
Overlay Analysis ◽  
Distribution Models ◽  
Habitat Directive ◽  
The Impact

Remote sensing (RS) has been widely adopted as a tool to investigate several biotic and abiotic factors, directly and indirectly, related to biodiversity conservation. European grasslands are one of the most biodiverse habitats in Europe. Most of these habitats are subject to priority conservation measure, and several human-induced processes threaten them. The broad expansions of few dominant species are usually reported as drivers of biodiversity loss. In this context, using Sentinel-2 (S2) images, we investigate the distribution of one of the most spreading species in the Central Apennine: Brachypodium genuense. We performed a binary Random Forest (RF) classification of B. genuense using RS images and field-sampled presence/absence data. Then, we integrate the occurrences obtained from RS classification into species distribution models to identify the topographic drivers of B. genuense distribution in the study area. Lastly, the impact of B. genuense distribution in the Natura 2000 (N2k) habitats (Annex I of the European Habitat Directive) was assessed by overlay analysis. The RF classification process detected cover of B. genuense with an overall accuracy of 94.79%. The topographic species distribution model shows that the most relevant topographic variables that influence the distribution of B. genuense are slope, elevation, solar radiation, and topographic wet index (TWI) in order of importance. The overlay analysis shows that 74.04% of the B. genuense identified in the study area falls on the semi-natural dry grasslands. The study highlights the RS classification and the topographic species distribution model’s importance as an integrated workflow for mapping a broad-expansion species such as B. genuense. The coupled techniques presented in this work should apply to other plant communities with remotely recognizable characteristics for more effective management of N2k habitats.

scholarly journals Dynamic response characteristics of 93W alloy with a spherical structure

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 199-211
Author(s):  
Taiyong Zhao ◽  
Weizhan Wang ◽  
Zhigang Chen ◽  
Shunshan Feng ◽  
Likui Yin ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Metallographic Analysis ◽  
Radial Deformation ◽  
Transgranular Fracture ◽  
Dense Area ◽  
Response Characteristics ◽  
Spherical Component ◽  
Bright Band ◽  
Dynamic Response Characteristics ◽  
The Impact

AbstractTo study the dynamic response characteristics of 93W alloy spherical component under high overload, the deformation patterns of the 93W spherical component under different overloads are obtained by the sphereistic impact test, and the microscopic response characteristics are studied by the metallographic analysis experiments. Finally, the response characteristics are analyzed by the finite element method and the stress wave theory. The results show that with the change of impact overload, the axial direction of the 93W spherical component changes linearly with the radial deformation, and the axial strain increases with the increase of the impact overload. At the same time, along the radial direction from the center of the sphere, the micrograin distribution of 93W appears densely packed and sparsely separated, and the grain density is uniformly changed between dense area and sparse area, showing a ring-shaped “bright band” phenomenon between light and dark, and the width of the “bright band” is related to the size of the dense area of the grain; with the increase of the impact overload, the 93W alloy component first breaks at the central axis and the radial maximum position, and the fracture mode changes from the crystal fracture to the transgranular fracture tendency, and the two fracture forms eventually coexist.

scholarly journals Vibration responses characteristics of a Ginkgo biloba tree excited under harmonic excitation

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256492
Author(s):  
Huan Lin ◽  
Leihou Sun
Keyword(s):  
Frequency Spectrum ◽  
Ginkgo Biloba ◽  
Low Frequency ◽  
Harmonic Excitation ◽  
Dynamic Responses ◽  
Impact Excitation ◽  
Single Frequency ◽  
Vibration Responses ◽  
Different Characteristics ◽  
The Impact

The most effective method of the fruit harvesting is the mechanical harvest. The frequency spectrum of different testing positions on a Ginkgo biloba tree under the impact excitation was tested in the laboratory. The acceleration responses under the harmonic excitation were measured at the frequency of the peak and trough points in the frequency spectrum curves. Results of this research indicate that the frequency spectrum presented the consistency on the same branch but distinction among different branches. There was a correspondence between the frequency spectrum characteristics and the vibration responses. The vibration responses could be strengthened at the resonant frequency. Merely, the acceleration responses at low frequency were very weak. At higher frequency, the vibration responses were strong but presented different characteristics among different branches. The acceleration response on the trunk was always the weakest. On the same branch, the dynamic responses presented the similar characteristics and the acceleration amplitude increased gradually as the testing position was located away from the excitation point on the trunk. Among different branches, the strongest dynamic response appeared at different frequencies. Our results indicate that it was difficult to induce the strong vibration response of all the branches at the single frequency during the practical mechanical harvesting of fruits.

scholarly journals Contact Dynamics and Stress Field of Fluid-Conveying GRC Nanotubes

2021 ◽  
Author(s):  
Qiduo Jin ◽  
Yiru Ren
Keyword(s):  
Stress Field ◽  
Dynamic Response ◽  
Strain Gradient ◽  
Time History ◽  
Contact Dynamics ◽  
Dynamic Responses ◽  
Stress And Strain ◽  
Nonlocal Stress ◽  
Post Buckling ◽  
The Impact

Abstract Fluid-conveying nanotubes play key roles in micro-nano electromechanical systems. The contact dynamic response and stress field of the fluid-conveying graphene reinforced composite (GRC) nanotube under lateral low-velocity impact are studied. The size-dependent models considering slip flow, nonlocal stress and strain gradient effect are established. The governing equations of flow-inducing post buckling and contact vibration are derived based on a refined beam theory, in which the post-buckling equilibrium provides the initial configuration for the impact vibration analysis. A computation mode of two-step perturbation-Galerkin truncation-Runge-Kutta method is developed to study the contact dynamic responses. Through the convergence analysis, the truncation terms required to ensure the accuracy are obtained. The contact force curves and the midspan displacement time history curves are acquired, and the dynamic snap-through instability behaviors of the nanotube in the flow-inducing post-buckling state are revealed. Also, the stress field in the impact process is obtained to provide theoretical results to guide the strength design. Numerical results reveal the dual influence law of nonlocal stress and strain gradient on the contact dynamic response and stress field and provide the flow velocity range sensitive to the nano effects.

scholarly journals Study on the Dynamic Response Characteristics of Cylindrical Coal-Rock Samples under Dynamic Loads

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Hongqing Zhu ◽  
Shuhao Fang ◽  
Yilong Zhang ◽  
Yan Wu
Keyword(s):  
Dynamic Response ◽  
Linear Relationship ◽  
Rock Sample ◽  
Axial Stress ◽  
Stress And Strain ◽  
Rock Samples ◽  
Response Characteristics ◽  
Coal Rock ◽  
Dynamic Response Characteristics ◽  
The Impact

To research the dynamic response characteristics of cylindrical coal-rock samples under impact loads, the impact of rigid bars on cylindrical coal-rock samples is simulated under different speed conditions, based on LS-DYNA software, and the dynamic distribution characteristics of the stress, strain, and energy of cylindrical coal-rock samples are analyzed. The results demonstrated the following: (1) the cylindrical coal-rock sample failed at the center first, and the damage developed downward along the axial direction. (2) The critical effective stress and strain have an exponential function relationship with the velocity, and the critical time has a linear relationship with the velocity. (3) The energy change law of the cylindrical coal-rock sample is consistent with the destruction morphology. (4) The axial stress peaks in the severe damage part have a linear relationship with the speed, the axial stress attenuates rapidly after passing the stress yield point, and the axial strain does not increase continuously. (5) The peaks stress and strain on the central axis and the radial line obey the power function distribution, the axial stress produces tensile stress in the axial propagation direction, and the axial stress and strain peaks at the same position are larger than those of the radial stress and strain peaks. This research provides a reference for studying coal and rock dynamic disasters.

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