检索结果-内蒙古大学图书馆

Computation of neuromagnetic fields using finite-element method and Biot-Savart law

MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING 1996年第1期34卷 21-26页

作者： vandenBroek, SP Zhou, H Peters, MJ Faculty of Applied Physics University of Twente Enschede The Netherlands

The finite-element method in combination with the Biot-Savart law is described to compute the magnetic field distribution generated by a dipolar source within a homogeneous volume conductor of an arbitrary shape. In order to calculate the three independent components of the magnetic field outside the volume conductor by means of the Biot-Savart law, the distribution of the current throughout the medium is required. A finite-element mesh is constructed using four-node tetrahedral elements. The potential in each node is computed numerically by the finite-element method using the proper continuity conditions across the boundaries. The gradient of the potential denotes the current density within an element. The components of the magnetic induction are calculated by numerical integration, applying the current density within the tetrahedrons. Simulations are carried out to assess the numerical accuracy for a homogeneous spherical volume conductor. Errors of 3% can be obtained with a locally refined spherical mesh containing about 1000 nodes, for dipoles at any depth and any orientation. A homogeneous realistically shaped model with the shape of the inside of the skull is obtained from magnetic resonance images.

关键词： Biot-Savart law finite-element method forward problem MEG volume conductor

来源：评论

学校读者我要写书评

暂无评论

Fault Analysis and Parameter Identification of Permanent-Magnet Motors by the finite-element method

引用

IEEE TRANSACTIONS ON MAGNETICS 2009年第9期45卷 3290-3295页

作者： Vaseghi, Babak Takorabet, Noureddine Meibody-Tabar, Farid Nancy Univ INPL GREEN F-54516 Vandoeuvre Les Nancy France

We performed a time-stepping finite-element-method (FEM) analysis to study a rotor surface-mounted permanent-magnet synchronous machine with insulation failure inter-turn fault. We used FEM for magnetic field study and determining the machine parameters under various fault conditions. We studied the effect of machine pole number and number of faulted turns on machine parameters. Finally, we used the FEM machine model for studying permanent-magnet machine behavior under different fault conditions.

关键词： Fault diagnosis finite-element method inter-turn fault permanent-magnet motor PMSM parameter identification

来源：评论

学校读者我要写书评

暂无评论

Free-edge effects analysis of angle-ply laminates under transverse loading using layer-wise finite-element method with semi-analytical shear stress calculation

引用

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE 2009年第2期223卷 293-306页

作者： Mohammadi, B. Hosseini-Toudeshky, H. Sadr-Lahidjani, M-H Amir Kabir Univ Technol Dept Aerosp Engn Tehran Iran Amir Kabir Univ Technol Ctr Excellence Computat Aerosp Engn Tehran Iran

Free-edge stress fields are of an utmost localized nature exhibiting steep stress gradients and they rapidly decay with increasing distance from the laminates' edges. Layer-wise theory has already been used to analyse the stress field at the free edges of the laminates. In this investigation, the layer-wise theory in finite-element method (FEM) is used to analyse the stress field of the laminates' free edges. In this study, apart from the conventional FEM in which the stresses are calculated from the constitutive laws, the shear stress components along the thickness are calculated from the equilibrium equations by employing a semi-analytical approach. It is shown that the obtained stresses from the current investigation are very close to those available from the three-dimensional elasticity solution for a square laminate under transversely double sinusoidal pressure distribution. To investigate the free edge influence on shear stress distribution of laminates under transverse loading, the analyses are performed for three angle-ply lay-ups with clustered and alternating sequences. It is shown that the free edge effects of angle-ply laminates with different stacking sequences under transverse pressure loading could be considerably different from laminates with in-plane loading conditions.

关键词： free edge layer-wise shear stress finite-element method semi-analytical transverse load

来源：评论

学校读者我要写书评

暂无评论

Sensitivity analysis of simulations for magnetic particle inspection using the finite-element method

引用

IEEE TRANSACTIONS ON MAGNETICS 2003年第6期39卷 3604-3606页

作者： Lee, JY Lee, SJ Jiles, DC Garton, M Lopez, R Brasche, L Samsung SDS IT Res Ctr Boondang 463810 South Korea Iowa State Univ Ames Lab Ames IA 50011 USA Iowa State Univ Dept Mat Sci & Engn Ames IA 50011 USA Iowa State Univ Ctr Aviat Syst Reliabil Ames IA 50011 USA

Magnetic particle inspection (MPI) is widely used for nondestructive evaluation in aerospace applications in which interpretation of inspection results is currently limited to empirical knowledge and experience-based approaches. Advances in computational magnetics, particularly the use of finite-element calcu lations, have enabled realistic numerical simulations of magnetic particle inspection to be undertaken with complicated geometries. In this paper, we report a sensitivity analysis using finite-element-method simulations of magnetic particle inspection for defects with various sizes and geometries. As a result, improved quantitative understanding of the MPI technique and factors that Affects its sensitivity and reliability has been achieved. These results can be used to optimize conditions for conducting these inspections and should lead to improvement in analysis and interpretation of experimental results.

关键词： finite-element method magnetic particle inspection nondestructive evaluation sensitivity analysis

来源：评论

学校读者我要写书评

暂无评论

Effective medium approximation of ellipsometric response from random surface roughness simulated by finite-element method

引用

THIN SOLID FILMS 2016年 617卷 20-24页

作者： Fodor, B. Kozma, P. Burger, S. Fried, M. Petrik, P. Hungarian Acad Sci Energy Res Ctr Inst Tech Phys & Mat Sci MFA Konkoly Thege Ut 29-33 H-1121 Budapest Hungary Univ Pecs Fac Sci Doctoral Sch Phys Ifjusag Utja 6 H-7624 Pecs Hungary ZIB Takustr 7 D-14195 Berlin Germany Univ Pannonia Doctoral Sch Mol & Nanotechnol Fac Informat Technol Egyet U 10 H-8200 Veszprem Hungary

We used numerical simulations based on the finite-element method (FEM) to calculate both the amplitude and phase information of the scattered electric field from random rough surfaces, which can be directly compared to ellipsometric measurements and effective medium approximation (EMA) calculations. FEM can serve as an exploration tool for the relationship between the thickness of the surface roughness evaluated by Bruggeman EMA and the morphological parameters of the surface, such as the root mean square height, the lateral auto correlation length, and the typical average slope. These investigations are of high interest in case of polycrystalline and amorphous materials. The paper focuses on the simulations of rough Si surfaces. The ellipsometric calculations from FEM and EMA simulations match for wavelengths of illumination much shorter than the typical feature size of the surface. Furthermore, for these cases, the correlation between the EMA thickness and the root mean square height of the roughness for a given auto-correlation length is quadratic, rather than linear, which is in good agreement with experimental measurements and analytical calculations presented in recent reports. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Ellipsometry Surface roughness Effective medium approximation finite-element method Root mean square height Correlation length

来源：评论

学校读者我要写书评

暂无评论

Contact force algorithm in explicit transient analysis using finite-element method

引用

finite elementS IN ANALYSIS AND DESIGN 2007年第6-7期43卷 580-587页

作者： Wang, Fu-Jun Wang, Li-Ping Cheng, Jian-Gang Yao, Zhen-Han China Agr Univ Coll Water Conservancy & Civil Engn Beijing 100083 Peoples R China Tsinghua Univ Dept Engn Mech Beijing 100084 Peoples R China

The contact force calculation has significant effect on the accuracy and efficiency of finite-element analysis for contact-impact problems. In this paper, an algorithm for contact force calculation in explicit finite-element analysis is presented. The classical penalty method and Lagrange multiplier method are combined by interpreting the impenetrability between two bodies as a control parameter in this algorithm. The constraints of no-penetration condition and sticking condition are imposed accurately without the requirement to choose a proper parameter as in the penalty method. With this algorithm, no coupled system of equations needs to be solved. The interaction of contact pairs applied on same segment is treated with iteration procedure. This algorithm is totally compatible with the explicit time integration scheme. Numerical examples demonstrate that this algorithm performs well for contact-impact problems. In contrast to the penalty method, this algorithm increases the stable time step because the effect of penalty parameter to the stability does not exist. The new algorithm provides an accurate and efficient way to study contact-impact problems with explicit finite-element method. (c) 2007 Elsevier B.V. All rights reserved.

关键词： contact force algorithm finite-element method explicit transient analysis contact-impact problem

来源：评论

学校读者我要写书评

暂无评论

Elimination of Nonphysical Solutions and Implementation of Adaptive Step Size Algorithm in Time-Stepping finite-element method for Magnetic Field-Circuit-Motion Coupled Problems

引用

IEEE TRANSACTIONS ON MAGNETICS 2010年第1期46卷 29-38页

作者： Fu, W. N. Ho, S. L. Hong Kong Polytech Univ Dept Elect Engn Kowloon Hong Kong Peoples R China

The time-stepping finite-element method (FEM) has become a powerful tool in solving transient electromagnetic fields. The formulation can include complex issues such as time harmonics and space harmonics, nonlinear magnetic property of iron materials, external circuit, and mechanical motion in the system equations. However, as the derivatives of physical quantities are usually unknown at the initial step of the time-stepping method, erroneous solutions might appear at the beginning of the transient process. To reduce the number of time steps, an adaptive step size algorithm can be used. In this paper, a method to eliminate the nonphysical or nonrealistic solutions at the start of the time-stepping finite-element analysis (FEA), when simulating the transient process of electric devices, is presented. A practical implementation of adaptive time step size algorithm for coupled problems is proposed. A matrix operation method, which can be understood clearly and implemented easily, that deals with matching boundary conditions in the study of mechanical motion, is also described.

关键词： Adaptive algorithm coupling method electric circuit electric device finite-element method initialization magnetic field mechanical motion time-stepping

来源：评论

学校读者我要写书评

暂无评论

New Algorithm for Three-Dimensional Borehole-to-Surface Apparent Resistivity Imaging Based on Unstructured Mesh finite-element method

引用

IEEE ACCESS 2020年 8卷 184-194页

作者： Xiong, Zhitao Tang, Xingong Qiu, Weizhong Zhao, Chunyan Zhang, Lianqun Yangtze Univ Key Lab Explorat Technol Oil & Gas Resources MOE Wuhan 430100 Peoples R China Hubei Cooperat Innovat Ctr Unconvent Oil & Gas Wuhan 430100 Hubei Peoples R China Shanxi Coal Geol Explorat Inst Datong 037039 Peoples R China Shanxi 131 Coal Field Geol Ltd Co Hancheng 715400 Peoples R China PetroChina Res Inst Petr Explorat & Dev Beijing 100083 Peoples R China

In this paper, a finite-element method with unstructured mesh is used to numerically simulate the line source model of three-dimensional borehole-to-surface electrical potential method. A new total field potential is synthesized using the calculated anomalous field potential and the analytic solution of the background field. In solving for the original total field potential and background potential, this method can guarantee a small near-field error in the new total field potential without the need to densely mesh the region with the source. By comparing the synthesized total field and analytic solution, the high accuracy of the numerical solution is verified. The results of model calculation show that the detection effectiveness of the borehole-to-surface electrical method depends on the length of the line source. The detection effectiveness increases substantially with increasing length of the line source within a certain range. However, when the line source is excessively long, the increase in detection effectiveness for anomalies is insignificant. For a low-resistance anomaly of a given volume, the borehole-to-surface electrical method is more sensitive to changes in the lateral area than to changes in the thickness. When the gob contains only a small amount of water (e.g., Model IV containing 50025;of water by volume), it will appear as a low-resistance anomaly. In addition, the detection of a water-logged gob by the borehole-to-surface electrical method depends on the depth and size of the gob. The borehole-to-surface method can accurately delineate the profile boundary of an anomaly, even though the side closer to the source is susceptible to the effect of source current. These results are significant for guiding the field exploration of the borehole-to-surface electrical method, improving result interpretation, and assisting the application.

关键词： Borehole-to-surface electrical potential method finite-element method vertical line source unstructured mesh

来源：评论

学校读者我要写书评

暂无评论

Wear prediction of clearance joint by integrating multi-body kinematics with finite-element method

引用

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY 2010年第J8期224卷 815-823页

作者： Su, Y. Chen, W. Tong, Y. Xie, Y. Xi An Jiao Tong Univ Sch Mech Engn Xian 710049 Peoples R China

A numerical approach of wear prediction integrating with system kinematics is proposed to investigate the interaction between wear of joint with clearance and kinematics in multi-body systems. The coupling between wear of joint and system kinematics is modelled by integrating wear prediction process with finite-element-based iterative scheme. Kinematical behaviours of a machine with a kinematical model of imperfect joint are progressively changed throughout joint wear process. The massless link model for clearance joint with the assumption of continuous contacts is used. Results from predictions and tests show that both wear zones and wear depth are different for the pin and bushing.

关键词： wear model multi-body dynamics finite-element method joint clearance

来源：评论

学校读者我要写书评

暂无评论

Numerical investigation on the static performance of aerostatic journal bearings with different pocket shapes by the finite-element method

引用

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY 2021年第9期235卷 1897-1911页

作者： Chen, Xinglong Mills, James K. Shi, Kai Bao, Gang Harbin Inst Technol Sch Mechatron Engn Nangang Peoples R China Univ Toronto Dept Mech & Ind Engn Toronto ON Canada

In this work, to improve the static behavior of aerostatic journal bearings, we examine the effect of pockets with different shapes, including the square, rectangular 1, rectangular 2, and circular, manufactured on the surface of the aerostatic journal bearing. The effects of the pocket shapes, pocket area S over bar , eccentricity ratio e, orifice diameter d(f), average gas film thickness h(0), and misalignment angles phi(x) and phi(y) on the static performance are investigated using simulations. The Reynolds equation is solved by the finite-element method in this work. Simulations reveal that the pocket area S over bar , eccentricity ratio e, gas film thickness h(0), orifice diameter d(f), and misalignment angles phi(x) and phi(y) have a significant influence on the load force F and the stiffness K. In general, rectangular 2 pocket bearings are found to perform somewhat better than bearings with other pocket shapes, with the pocket depth set to one-half of h(0), when the pocket area S over bar varies from one-twelfth to one. The pocket area S over bar should be set according to the average gas film thickness h(0) and the orifice diameter d(f) to achieve a better static performance for the bearings. For bearings operated with misalignment angles phi(x) and phi(y), different pocket areas S over bar should be set according to the pocket shapes for the optimal design.

关键词： Aerostatic journal bearing static performance pocket shapes finite-element method

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：