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Electric-magnetic-force characteristics of rare earth barium copper oxide superconductor high-field coils based on screening effect and strain sensitivity

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Applied Mathematics and Mechanics(English Edition) 2022年第8期43卷 1249-1268页

作者： Wenhai zhou youhe zhou Key Laboratory of Mechanics on Environment and Disaster in Western China The Ministry of Education of ChinaCollege of Civil Engineering and MechanicsLanzhou UniversityLanzhou730000China School of Petrochemical Technology Lanzhou University of TechnologyLanzhou730050China

Rare earth barium copper oxide(REBCO)is the most researched and commercialized second-generation high-temperature superconducting *** to the anisotropic structure,strong deformation sensitivity,and central field errors caused by screening current effects,it is still a challenge for commercialization *** this study,the transversely isotropic constitutive relationship is selected as the mechanical model based on the structural characteristics of REBCO tapes,and suitable microelements are selected to equate the elastic constants using their average stress-strain ***,a two-dimensional axisymmetric model for coils wound by single-layer tapes is constructed to analyze the dependence of the electric-magnetic-force distribution in the tape on the ***,the anisotropic approximation of the homogenized bulk method is used to equate large-turn high-field coils,and the electric-magnetic-force distribution characteristics of the coils with/without screening effects and mechanical strain conditions are investigated,*** results reveal that the mechanical strain has a weakening effect on the electromagnetic field distribution of superconducting tapes,but causes a significant enhancement in the force field *** the presence of 0.5% mechanical strain,the maximum weakening of the peak value of the current density and the critical current density inside the high-field coil can reach about 8% and 13%,respectively,with a nearly 5 times increase in the peak *** screening current makes the current field distribution inside the coil improve by about 10 *** screening current induced magnetic field can reach up to 0.8 T,making the relative error of the high-field coil center up to 7.8%.

关键词： screening current strain sensitivity mechanical behavior rare earth barium copper oxide(REBCO)high-field coil electromagnetic field distribution

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A new simple method of implicit time integration for dynamic problems of engineering structures

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Acta Mechanica Sinica 2007年第1期23卷 91-99页

作者： Jun zhou youhe zhou Department of Mechanics Lanzhou University Lanzhou 730000 China

This paper presents a new simple method of implicit time integration with two control parameters for solving initial-value problems of dynamics such that its accuracy is at least of order two along with the conditional and unconditional stability regions of the parameters. When the control parameters in the method are optimally taken in their regions, the accuracy may be improved to reach of order three. It is found that the new scheme can achieve lower numerical amplitude dissipation and period dispersion than some of the existing methods, e.g. the Newmark method and Zhai＇s approach, when the same time step size is used. The region of time step dependent on the parameters in the new scheme is explicitly obtained. Finally, some examples of dynamic problems are given to show the accuracy and efficiency of the proposed scheme applied in dynamic systems.

关键词： Initial-value problems Time integration Implicit method Higher accuracy Time step and stability

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MODIFICATION OF ONE-DIMENSION COUPLED HYSTERESIS MODEL FOR GMM WITH THE DOMAIN FLEXING FUNCTION

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Acta Mechanica Solida Sinica 2014年第5期27卷 461-466页

作者： Yongfei Zhang youhe zhou Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China Lanzhou University Department of Mechanics and Engineering Sciences College of Civil Engineering and Mechanics Lanzhou University

This paper focuses on eliminating the unphysical negative susceptibility which ap- pears when magnetic field is at unsaturated excitation level and reduces from extremity of the hysteresis loop in one-dimension coupled hysteresis model. The domain flexing function c （H） is used to replace the domain flexing constant c in one-dimension coupled hysteresis model. The fea- sibility and rationality of proposed modification are convinced by comparing the magnetization and magnetostriction curves with experimental data and another typical modification results. The effects of pre-stress and temperature on magnetic-elastic-thermal coupling property and hysteresis behavior are investigated.

关键词： coupled hysteresis model domain flexing function negative susceptibility innerloop

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A MAGNETO-MECHANICAL FULLY COUPLED MODEL FOR GIANT MAGNETOSTRICTION IN HIGH TEMPERATURE SUPERCONDUCTOR

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Acta Mechanica Solida Sinica 2015年第4期28卷 353-359页

作者： Zhiwen Gao youhe zhou Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China Department of Mechanics and Engineering Sciences College of Civil Engineering and Mechanics Lanzhou University

This paper presents a fully coupled model to account for the flux pinning induced giant magnetostriction in type-Ⅱ superconductors under alternating magnetic field The superconductor E-J constitutive law is characterized by power law where the critical current density is assumed to depend exponentially on the flux density. The governing equations of the two-field problem （i.e., the interactions of elastic and magnetic effects） are formulated in a two-dimensional model. The magnetostriction curves and magnetization loops are calculated over a wide range of parameters. The effects of applied magnetic field frequency f and amplitude B0 and critical current density on magnetostriction and magnetization are discussed. Results show that the critical current density of high temperature superconductor （HTS） YBCO has a significant effect on the magnetization and magnetostriction. The pinning-induced magnetostriction which has been observed in experiment can be qualitatively simulated by this model.

关键词： high temperature superconductor (HTS) giant magnetostriction magnetization,magneto-mechanical couple alternating magnetic field

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VIBRATION SUPPRESSION OF CANTILEVER LAMINATED COMPOSITE PLATE WITH NONLINEAR GIANT MAGNETOSTRICTIVE MATERIAL LAYERS

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Acta Mechanica Solida Sinica 2015年第1期28卷 50-61页

作者： Yongfei Zhang Haomiao zhou youhe zhou Key Laboratory of Mechanics on Disaster and Environment in Western China the Ministry of Education of China Lanzhou University Department of Mechanics and Engineering Sciences College of Civil Engineering and MechanicsLanzhou University College of Information Engineering China Jiliang University

In this paper, a nonlinear and coupled constitutive model for giant magnetostrictive materials （GMM） is employed to predict the active vibration suppression process of cantilever laminated composite plate with GMM layers. The nonlinear and coupled constitutive model has great advantages in demonstrating the inherent and complicated nonlinearities of GMM in re- sponse to applied magnetic field under variable bias conditions （pre-stress and bias magnetic field）. The Hamilton principle is used to derive the nonlinear and coupled governing differential equation for a cantilever laminated composite plate with GMM layers. The derived equation is handled by the finite element method （FEM） in space domain, and solved with Newmark method and an iteration process in time domain. The numerical simulation results indicate that the proposed active control system by embedding GMM layers in cantilever laminated composite plate can efficiently suppress vibrations under variable bias conditions. The effects of embedded placement of GMM layers and control gain on vibration suppression are discussed respectively in detail.

关键词： giant magnetostrictive materials nonlinear constitutive model active vibration suppression cantilever laminated composite plate

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Discrete element simulation of localized deformation in stochastic distributed granular materials

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Science China(Physics,Mechanics & Astronomy) 2008年第9期51卷 1403-1415页

作者： WANG DengMing zhou youhe Key Laboratory of Mechanics on Western Disaster and Environment Ministry of Education of ChinaDepartment of MechanicsLanzhou UniversityLanzhou 730000China

The deformation in granular material under loading conditions is a problem of great interest currently. In this paper,the micro-mechanism of the localized deformations in stochastically distributed granular materials is investigated based on the modi-fied distinct element method under the plane strain conditions,and the influences of the confining pressure,the initial void ratio and the friction coefficient on the localized deformation and the stability of granular materials are also studied. It is concluded,based on the numerical simulation testing,that two crossed shear sliding planes may occur inside the granular assembly,and deformation patterns vary with the increasing of transverse strain. These conclusions are in good agreement with the present experimental results. By tangential velocity profiles along the direction normal to the two shear sliding planes,it can be found that there are two different shear deformation patterns: one is the fluid-like shear mode and the other is the solid-like shear mode. At last,the influences of various material parameters or factors on localized deformation features and patterns of granular materials are discussed in detail.

关键词： granular material localized deformation modified discrete element method

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Wavelet multiresolution interpolation Galerkin method for nonlinear boundary value problems with localized steep gradients

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Applied Mathematics and Mechanics(English Edition) 2022年第6期43卷 863-882页

作者： Xiaojing LIU youhe zhou Jizeng WANG Key Laboratory of Mechanics on Disaster and Environment in Western China(Lanzhou University) the Ministry of EducationCollege of Civil Engineering and MechanicsLanzhou UniversityLanzhou 730000China

The wavelet multiresolution interpolation for continuous functions defined on a finite interval is developed in this study by using a simple alternative of transformation *** wavelet multiresolution interpolation Galerkin method that applies this interpolation to represent the unknown function and nonlinear terms independently is proposed to solve the boundary value problems with the mixed Dirichlet-Robin boundary conditions and various nonlinearities,including transcendental ones,in which the discretization process is as simple as that in solving linear problems,and only common two-term connection coefficients are *** matrices are independent of unknown node values and lead to high efficiency in the calculation of the residual and Jacobian matrices needed in Newton’s method,which does not require numerical integration in the resulting nonlinear discrete *** validity of the proposed method is examined through several nonlinear problems with interior or boundary *** results demonstrate that the proposed wavelet method shows excellent accuracy and stability against nonuniform grids,and high resolution of localized steep gradients can be achieved by using local refined multiresolution *** addition,Newton’s method converges rapidly in solving the nonlinear discrete system created by the proposed wavelet method,including the initial guess far from real solutions.

关键词： wavelet multiresolution interpolation transcendental nonlinearity localized steep gradient singularly perturbed boundary value problem Troesch’s problem

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Damage Analysis of Superconducting Composite Wire with Bridging Model

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Acta Mechanica Solida Sinica 2018年第1期31卷 19-31页

作者： Xubin Peng Huadong Yong youhe zhou Key Laboratory of Mechanics on Environment and Disaster in Western China The Ministry of Education of China Department of Mechanics and Engineering Sciences College of Civil Engineering and Mechanics Lanzhou University

The multi-filamentary Bi2Sr2CaCu2O8＋x （Bi-2212） round wires are made of super- conducting filaments, metal Ag and Ag alloy, which are typical composite structure. Since the filament is brittle, there are various defects and cracks in the Bi-2212 round wire after heat treat- ment. In this paper, we assume that the filaments in the wire are uniformly arranged. Adopting the bridging model which is often used in the fiber-reinforced composite, we calculate the ulti- mate strength of the round wire. The effects of the volume fraction, elastic modulus and interface shear strength are discussed in detail.

关键词： Bi-2212 composite Crack Bridging model Stress intensity factor Ultimate ten-sile strength

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A high-order accurate wavelet method for solving Schrdinger equations with general nonlinearity

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Applied Mathematics and Mechanics(English Edition) 2018年第2期39卷 275-290页

作者： Jiaqun WANG Xiaojing LIU youhe zhou Key Laboratory of Mechanics on Disaster and Environment in Western China the Ministry of EducationCollege of Civil Engineering and MechanicsLanzhou UniversityLanzhou 730000China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China

A sampling approximation for a function defined on a bounded interval is proposed by combining the Coiflet-type wavelet expansion and the boundary extension technique. Based on such a wavelet approximation scheme, a Galerkin procedure is developed for the spatial discretization of the generalized nonlinear Schr6dinger （NLS） equa- tions, and a system of ordinary differential equations for the time dependent unknowns is obtained. Then, the classical fourth-order explicit Runge-Kutta method is used to solve this semi-discretization system. To justify the present method, several widely considered problems are solved as the test examples, and the results demonstrate that the proposed wavelet algorithm has much better accuracy and a faster convergence rate in space than many existing numerical methods.

关键词： wavelet Galerkin method generalized nonlinear SchrSdinger (NLS) equation high-order convergence

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Critical current degradation in an epoxy-impregnated rare-earth Ba_(2)Cu_(3)O_(7-x)coated conductor caused by damage during a quench

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Applied Mathematics and Mechanics(English Edition) 2024年第9期45卷 1557-1572页

作者： Donghui LIU Huadong YONG youhe zhou Institute of Superconductor Mechanics Lanzhou UniversityLanzhou 730000China Department of Mechanics and Engineering Sciences College of Civil Engineering and MechanicsLanzhou UniversityLanzhou 730000China Key Laboratory of Mechanics on Disaster and Environment in Western China Ministry of Education of ChinaLanzhou UniversityLanzhou 730000China

High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field ***,owing to the weak interface strength of the laminated composite REBCO CCs,the damage induced by the thermal mismatch stress under a combination of epoxy impregnation,cooling,and quenching can cause premature degradation of the critical *** this study,a three-dimensional(3D)electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model(CZM)is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a *** temperature variation,critical current degradation of the REBCO CC,and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the *** delamination of the REBCO CC predicted by the numerical model is consistent with the experimental *** numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO *** premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO ***,the effects of the coefficient of thermal expansion(CTE)of the epoxy resin,thickness of the substrate,and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also *** results help us understand the relationship between the current-carrying degradation and damage in the HTS applications.

关键词： epoxy-impregnated rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductor(CC) quench damage critical current degradation shear stress

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