scholarly journals Capturing the two-way hydromechanical coupling effect on fluid-driven fracture in a dual-graph lattice beam model

2017 ◽  
Vol 42 (5) ◽  
pp. 736-767 ◽  
Author(s):  
Ole Ivar Ulven ◽  
WaiChing Sun
Keyword(s):  
Coupling Effect ◽  
Dual Graph ◽  
Beam Model ◽  
Hydromechanical Coupling ◽  
Lattice Beam ◽  
Graph Lattice

Developing an in situ, hydromechanical coupling, true triaxial rock compression tester and investigating the deformation patterns of reservoir bank slopes

2021 ◽  
pp. qjegh2021-043
Author(s):  
Lei Fan ◽  
Meiwan Yu ◽  
Aiqing Wu ◽  
Yihu Zhang
Keyword(s):  
Coupling Effect ◽  
Water Pressure ◽  
Pressure Coefficient ◽  
Hydromechanical Coupling ◽  
Rock Interaction ◽  
True Triaxial ◽  
Rock Structure ◽  
Deformation Patterns

Interactions between water and rocks are the main factors affecting the deformation of rock masses on sloped banks by reservoir impoundment. The technology used in laboratory tests of water-rock interaction mechanisms cannot simulate the coupling of water, the rock structure and the initial stress environment. In this work, we develop an in situ hydromechanical true triaxial rock compression tester and apply it to investigate the coupling response of reservoir bank rocks to changing groundwater levels. The tester is composed of a sealed chamber, loader, reactor, and device for measuring deformation, which are all capable of withstanding high water pressures, and a high-precision servo controller. The maximum axial load, lateral load and water pressure are 12 000 kN, 3 000 kN and 3 MPa, respectively. The dimensions of the test specimens are 310 mm×310 mm×620 mm. The test specimens are grey-black basalts with well-developed cracks from the Xiluodu reservoir area. The results show that increasing water pressure promotes axial compression and lateral expansion, while decreasing water pressure causes axial expansion and lateral compression. A water pressure coefficient, K, is introduced as a measure of the hydromechanical coupling effect (expansion or compression) with changing groundwater level. A mechanical tester can be used to perform accurate field tests of the response of wet rocks to hydromechanical coupling. The test results provide new information about the deformation patterns of rock slopes in areas surrounding high dams and reservoirs.Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

scholarly journals Stochastic analysis of lattice, nonlocal continuous beams in vibration

2021 ◽  
Vol 43 (2) ◽  
pp. 139-170
Author(s):  
Yuchen Li ◽  
Noël Challamel ◽  
Isaac Elishakoff
Keyword(s):  
Scale Effect ◽  
Lattice Model ◽  
Stochastic Analysis ◽  
Excitation Frequency ◽  
Random Variable ◽  
Chain Model ◽  
Beam Model ◽  
Elastic Links ◽  
Lattice Beam ◽  
Nonlocal Beam

In this paper, we study the stochastic behavior of some lattice beams, called Hencky bar-chain model and their non-local continuous beam approximations. Hencky bar-chain model is a beam lattice composed of rigid segments, connected by some homogeneous rotational elastic links. In the present stochastic analysis, the stiffness of these elastic links is treated as a continuous random variable, with given probability density function. The fundamental eigenfrequency of the linear difference eigenvalue problem is also a random variable in this context. The reliability is defined as the probability that this fundamental frequency is less than an excitation frequency. This reliability function is exactly calculated for the lattice beam in conjunction with various boundary conditions. An exponential distribution is considered for the random stiffness of the elastic links. The stochastic lattice model is then compared to a stochastic nonlocal beam model, based on the continualization of the difference equation of the lattice model. The efficiency of the nonlocal beam model to approximate the lattice beam model is shown in presence of rotational elastic link randomness. We also compare such stochastic function with the one of a continuous local Euler-Bernoulli beam, with a special emphasis on scale effect in presence of randomness. Scale effect is captured both in deterministic and non-deterministic frameworks.

Spectral Element Approach for the Homogeneous Continuum Representation of a Periodic Lattice Structure

1997 ◽  
Vol 12 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Usik Lee
Keyword(s):  
Structural Properties ◽  
Transfer Matrix ◽  
Dynamic Stiffness ◽  
Spectral Element ◽  
Periodic Lattice ◽  
Beam Model ◽  
Lattice Cell ◽  
Lattice Beam ◽  
Equivalent Continuum ◽  
The Continuum

Motivated by the apparent accuracy of the spectral element in comparison with the conventional finite element, a new dynamic continuum modeling method is developed by using the spectral element to represent a large periodic lattice beam as an equivalent continuum beam model. As the first step, the transfer matrix for a representative lattice cell of the periodic lattice beam is numerically derived in terms of the continuum degrees of freedom introduced in this paper. The global dynamic stiffness matrix is then obtained by assembling the spectrally formulated dynamic stiffness matrices for the structural elements within the lattice cell. As the second step, the transfer matrix for an equivalent continuum beam element is analytically derived in terms of the unknown equivalent continuum structural properties. Lastly, the two transfer matrices are forced to be equal to each other to determine the equivalent continuum structural properties of the continuum beam model. In this paper, the equivalent continuum structural properties and vibration characteristics of an equivalent continuum beam model by the present method are compared with those by the other existing continuum methods to show that the present continuum model gives vary reliable bending vibration characteristics of the original lattice structures compared to others.

scholarly journals Nonlocal Effect on the Pull-in Instability Analysis of Graphene Sheet Nanobeam Actuator

2019 ◽  
Vol 35 (5) ◽  
pp. 767-778 ◽  
Author(s):  
M. X. Lin ◽  
S. Y. Lee ◽  
C. K. Chen
Keyword(s):  
Residual Stresses ◽  
Graphene Sheet ◽  
Scale Effects ◽  
Coupling Effect ◽  
Small Scale ◽  
Beam Model ◽  
Viscous Damping ◽  
Euler Beam ◽  
Nonlocal Effects ◽  
Electrostatically Actuated

ABSTRACTIn this study, the pull-in phenomenon of a Nano-actuator is investigated employing a nonlocal Bernoulli-Euler beam model with clamped-clamped conditions. The model accounts for viscous damping, residual stresses, the van der Waals (vdW) force and electrostatic forces with nonlocal effects. The hybrid differential transformation/finite difference method (HDTFDM) is used to analyze the nonlocal effects on a graphene sheet nanobeam, which is electrostatically actuated under the influence of the coupling effect, the von Kármán nonlinear strains and the fringing field effect. The pull-in voltage as calculated by the presented model deviates by no more than 0.29% from previous literature, verifying the validity of the HDTFDM. Furthermore, the nonlocal nonlinear behavior of the electrostatically actuated nanobeam is investigated, and the effects of viscous damping, residual stresses, and length-gap ratio are examined in detail. Overall, the results reveal that small scale effects significantly influence the characteristics of the graphene sheet nanobeam actuator.

Static Wind Load and Gravity Coupling Effect of Tall Structure

2011 ◽  
Vol 94-96 ◽  
pp. 1556-1559 ◽  
Author(s):  
Zhen Yu Zhong
Keyword(s):  
Finite Difference ◽  
Cantilever Beam ◽  
Coupling Effect ◽  
Tall Buildings ◽  
Order Effect ◽  
Wind Load ◽  
Beam Model ◽  
Building Structure ◽  
Vertical Gravity ◽  
Tall Structure

The cantilever beam model of tall building structure which includes lateral wind load and vertical gravity coupling has been established in the paper. The form of finite difference has been concluded from equations of the model acted on static wind load. Amplified coefficients of bottom moment and top displacement are calculated and analyzed. The result shows that gravity second order effect of tall buildings will be enhanced when ratio of gravity rigidity or ratio of bending and shearing rigidity increase.

An hourglass-type electromagnetic isolator with negative resistance electromagnetic shunt circuit

2020 ◽  
Vol 64 (1-4) ◽  
pp. 549-556
Author(s):  
Yajun Luo ◽  
Linwei Ji ◽  
Yahong Zhang ◽  
Minglong Xu ◽  
Xinong Zhang
Keyword(s):  
Vibration Isolation ◽  
Electromechanical Coupling ◽  
Coupling Effect ◽  
Negative Resistance ◽  
Isolation System ◽  
Amplitude Vibration ◽  
Vibration Responses ◽  
The Stability ◽  
Isolation Performance ◽  
Shunt Circuit

The present work proposed an hourglass-type electromagnetic isolator with negative resistance (NR) shunt circuit to achieve the effective suppression of the micro-amplitude vibration response in various advanced instruments and equipment. By innovatively design of combining the displacement amplifier and the NR electromagnetic shunt circuit, the current new type of vibration isolator not only can effectively solve the problem of micro-amplitude vibration control, but also has significant electromechanical coupling effect, to obtain excellent vibration isolation performance. The design of the isolator and motion relationship is presented firstly. The electromechanical coupling dynamic model of the isolator is also given. Moreover, the optimal design of the NR electromagnetic shunt circuit and the stability analysis of the vibration isolation system are carried out. Finally, the simulation results about the transfer function and vibration responses demonstrated that the isolator has a significant isolation performance.

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