Communications in Numerical Methods in Engineering最新文献

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An innovative prone positioning system for advanced deformity and frailty in complex spine surgery. 创新的俯卧定位系统，用于复杂脊柱手术中的晚期畸形和虚弱。

IF 2.9

Communications in Numerical Methods in Engineering

Pub Date : 2019-10-25 Print Date: 2020-02-01 DOI: 10.3171/2019.7.SPINE19161

Benjamin Kolb, John Large, Stuart Watson, Glyn Smurthwaite

The authors present a technical note for a prone positioning system developed to facilitate cervical extension osteotomy for ankylosing spondylitis in the presence of severe deformity and frailty. Chin-on-chest deformity represents one of the most debilitating changes of ankylosing spondylitis. Where the chin-brow angle approaches or exceeds 90°, prone positioning becomes problematic due to the fixed position of the head. Furthermore, the challenge is compounded where physiological deconditioning leads to frailty, and the side effects of medical therapies decrease muscle mass and skin quality. Conventional prone positioning equipment is not able to cater to all patients. A versatile system was developed using a 3D reconstruction to enable a positioning simulation and verification tool. The tool was used to comprehensively plan the perioperative episode, including spatial orientation and associated equipment. Three-dimensional printing was used to manufacture a bespoke positioning device that precisely matched the contours of the patient, reducing contact pressure and risk of skin injury. The authors were able to safely facilitate surgery for a patient whose deformity and frailty may otherwise have precluded this possibility. The system has potential safety and economic implications that may be of significant utility to other institutions engaging in complex spinal surgery.

作者介绍了一种俯卧定位系统的技术说明，该系统的开发目的是在存在严重畸形和虚弱的情况下促进强直性脊柱炎的颈椎伸展截骨术。颏胸畸形是强直性脊柱炎最令人衰弱的病变之一。如果颏眉角接近或超过 90°，由于头部位置固定，俯卧位就会变得很困难。此外，当生理机能减退导致身体虚弱，以及药物治疗的副作用导致肌肉质量和皮肤质量下降时，问题就更加复杂了。传统的俯卧定位设备无法满足所有患者的需求。我们利用三维重建技术开发了一套多功能系统，用于定位模拟和验证工具。该工具用于全面规划围手术期，包括空间定位和相关设备。三维打印技术用于制造定制的定位设备，该设备能精确匹配患者的轮廓，减少接触压力和皮肤损伤风险。作者能够安全地为一名因畸形和虚弱而无法进行手术的患者提供手术便利。该系统具有潜在的安全和经济意义，可能对其他从事复杂脊柱手术的机构大有裨益。

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引用次数: 0

Optimization of anastomotic configuration in CABG surgery 冠脉搭桥手术吻合口构型的优化

Communications in Numerical Methods in Engineering

Pub Date : 2009-11-01 DOI: 10.1007/978-3-540-79039-6_29

Y. Sui, Baosheng Ma, B. Chu, A. Qiao

引用次数: 6

Comparative study between two numerical methods for oxygen diffusion problem 氧扩散问题两种数值方法的比较研究

Communications in Numerical Methods in Engineering

Pub Date : 2009-08-01 DOI: 10.1002/CNM.1127

Vildan Gülkaç

Two approximate numerical solutions of the oxygen diffusion problem are defined using three time-level of Crank–Nicolson equation and Gauss–Seidel iteration for three time-level of implicit method. Oxygen diffusion in a sike cell with simultaneous absorption is an important problem and has a wide range of medical applications. The problem is mathematically formulated through two different stages. At the first stage, the stable case having no oxygen transition in the isolated cell is searched, whereas at the second stage the moving boundary problem of oxygen absorbed by the tissues in the cell is searched. The results obtained by three time-level of implicit method and Gauss–Seidel iteration for three time-level of implicit method and the results gave a good agreement with the previous methods (J. Inst. Appl. Math. 1972; 10:19–33; 1974; 13:385–398; 1978; 22:467–477). Copyright © 2008 John Wiley & Sons, Ltd.

利用三时间水平的Crank-Nicolson方程和三时间水平的隐式方法的Gauss-Seidel迭代定义了氧扩散问题的两个近似数值解。氧在细胞中的同步吸收扩散是一个重要的问题，具有广泛的医学应用。这个问题是通过两个不同的阶段用数学公式表述出来的。在第一阶段，搜索孤立细胞中没有氧跃迁的稳定情况，在第二阶段，搜索细胞内组织吸收氧的移动边界问题。采用三时间级隐式方法和三时间级隐式方法的Gauss-Seidel迭代得到的结果与以往的方法吻合较好(J. Inst. Appl.)。数学。1972;10:19-33;1974;13:385 - 398;1978;22:467 - 477)。版权所有©2008 John Wiley & Sons, Ltd

引用次数: 9

Optimal stress recovery points for higher-order bar elements by Prathap's best-fit method 用Prathap最佳拟合方法求高阶杆件的最优应力恢复点

Communications in Numerical Methods in Engineering

Pub Date : 2009-08-01 DOI: 10.1002/CNM.1129

S. Rajendran

Barlow was the first to propose a method to predict optimal stress recovery points in finite elements (FEs). Prathap proposed an alternative method that is based on the variational principle. The optimal points predicted by Prathap, called Prathap points in this paper, have been reported in the literature for linear, quadratic and cubic elements. Prathap points turn out to be the same as Barlow points for linear and quadratic bar elements but different for cubic bar element. Nevertheless, for all the three elements, Prathap points coincide with the reduced Gaussian integration points. In this paper, an alternative implementation of Prathap's best-fit method is used to compute Prathap points for higher-order (viz., 4–10th order) bar elements. The effectiveness of Prathap points as points of accurate stress recovery is verified by actual FE analysis for typical bar problems. Copyright © 2008 John Wiley & Sons, Ltd.

Barlow首先提出了一种方法来预测有限元(FEs)的最佳应力恢复点。Prathap提出了一种基于变分原理的替代方法。Prathap预测的最优点(本文称为Prathap点)已在线性、二次元和三次元的文献中得到报道。对于线性和二次杆单元，Prathap点与Barlow点相同，但对于三次杆单元，Prathap点不同。然而，对于所有这三个元素，Prathap点与简化的高斯积分点一致。在本文中，使用Prathap的最佳拟合方法的另一种实现来计算高阶(即4 - 10阶)杆元素的Prathap点。通过对典型杆件的有限元分析，验证了Prathap点作为精确应力恢复点的有效性。版权所有©2008 John Wiley & Sons, Ltd

引用次数: 3

Free vibration and bending analysis of circular Mindlin plates using singular convolution method 用奇异卷积法分析圆形Mindlin板的自由振动和弯曲

Communications in Numerical Methods in Engineering

Pub Date : 2009-08-01 DOI: 10.1002/CNM.1138

Ö. Civalek, H. Ersoy

Circular plates are important structural elements in modern engineering structures. In this paper a computationally efficient and accurate numerical model is presented for the study of free vibration and bending behavior of thick circular plates based on Mindlin plate theory. The approach developed is based on the discrete singular convolution method and the use of regularized Shannon's delta kernel. Frequency parameters, deflections and bending moments are obtained for different geometric parameters of the circular plate. Comparisons are made with existing numerical and analytical solutions in the literature. It is found that the DSC method yields accurate results for the free vibration and bending problems of thick circular plates. Copyright © 2008 John Wiley & Sons, Ltd.

引用次数: 21

A stabilized smoothed finite element method for free vibration analysis of Mindlin–Reissner plates Mindlin-Reissner板自由振动分析的稳定光滑有限元法

Communications in Numerical Methods in Engineering

Pub Date : 2009-08-01 DOI: 10.1002/CNM.1137

H. Nguyen-Xuan, T. Nguyen-Thoi

A free vibration analysis of Mindlin–Reissner plates using the stabilized smoothed finite element method is studied. The bending strains of the MITC4 and STAB elements are incorporated with a cell-wise smoothing operation to give new proposed elements, the mixed interpolation and smoothed curvatures (MISCk) and SMISCk elements. The corresponding bending stiffness matrix is computed along the boundaries of the smoothing elements (smoothing cells). Note that shearing strains and the shearing stiffness matrix of the proposed elements are unchanged from the original elements, the MITC4 and STAB elements. It is confirmed by numerical tests that the present method is free of shear locking and has the marginal improvements compared with the original elements. Copyright © 2008 John Wiley & Sons, Ltd.

采用稳定光滑有限元法对Mindlin-Reissner板的自由振动进行了分析。将MITC4和STAB单元的弯曲应变与单元平滑运算相结合，得到新的拟合单元，即混合插值和平滑曲率(MISCk)和SMISCk单元。沿光滑单元(平滑单元)的边界计算相应的弯曲刚度矩阵。请注意，所提出单元的剪切应变和剪切刚度矩阵与原始单元、MITC4和STAB单元没有变化。数值试验结果表明，该方法不存在剪切锁紧现象，且与原方法相比有较大改进。版权所有©2008 John Wiley & Sons, Ltd

引用次数: 78

Call for Papers: ‘Fluid-Structure Interaction in Biomedical Applications’ 论文征集:“流体-结构相互作用在生物医学应用中的应用”

Communications in Numerical Methods in Engineering

Pub Date : 2008-12-10 DOI: 10.1002/cnm.1151

R. Loon, F. Vosse

引用次数: 0

Non‐stationary plane problem of the successive origination of stress concentrators in a loaded body. Finite deformations and their superposition 承载体应力集中点连续起源的非定常平面问题。有限变形及其叠加

Communications in Numerical Methods in Engineering

Pub Date : 2008-12-01 DOI: 10.1002/CNM.1092

V. Levin, A. Vershinin

The first (for the given class of problems) results of solving non-stationary plane problems of non-simultaneous origination of holes and inclusions in a preliminary loaded solid with initial finite strains are presented and discussed. It is taken into account that the origination of a hole or an inclusion produces additional finite deformations (at least, at the vicinity of the hole) superimposed 'physically' on the finite initial ones. The problem is solved using the theory of repeated superposition of large deformations. It is supposed that the shape of stress concentrators is given at the moment of their origination. Calculations were made with the use of the specialized computer package 'Superposition' based on finite-element method. Stress fields are presented at different times. The change of maximal stresses in time is also presented.

给出并讨论了具有初始有限应变的初始加载固体中孔洞和夹杂非同时产生的非定常平面问题的第一个结果(对于给定的一类问题)。考虑到孔洞或夹杂物的起源会产生额外的有限变形(至少在孔洞附近)，这些变形在“物理上”叠加在有限的初始变形上。利用大变形重复叠加理论解决了这一问题。假定应力集中器的形状是在其产生的时刻给定的。利用基于有限元法的专业计算机软件包“叠加”进行了计算。在不同时间呈现应力场。给出了最大应力随时间的变化规律。

引用次数: 12

Dynamic numerical simulations of void growth and coalescence with stress triaxiality maintained constant : Application to ductile solids with secondary voids 三轴应力保持恒定时孔洞生长和合并的动态数值模拟:应用于具有次生孔洞的延性固体

Communications in Numerical Methods in Engineering

Pub Date : 2008-12-01 DOI: 10.1002/CNM.1093

L. Siad

Dynamic explicit finite element analysis is used to investigate void growth and plastic collapse of an axisymmetric unit cell model with a primary spherical void imbedded in a porous matrix material. The Gurson–Tvergaard–Needleman homogenized model is used to describe the plastic behaviour of the matrix material. The simulations are performed under large strain conditions for varying secondary void volume fractions and quasi-static loading controlled by constant stress triaxiality. The proposed accomplishment of constant stress triaxiality associated with dynamic explicit computations provides a method allowing to trace the collapse of the unit cell from the onset of coalescence to practically its final failure. Consistent with experimental and theoretical results available in the literature, the obtained results substantiate the sensitivity of coalescence to the presence of secondary voids. Copyright © 2008 John Wiley & Sons, Ltd.

采用动态显式有限元分析方法，研究了含原生球形孔洞的轴对称单胞模型的孔洞生长和塑性破坏问题。采用Gurson-Tvergaard-Needleman均匀化模型来描述基体材料的塑性行为。在变二次孔隙体积分数和恒应力三轴控制的准静态加载大应变条件下进行了模拟。与动态显式计算相关的恒应力三轴性的提出提供了一种方法，可以跟踪从合并开始到实际最终破坏的单元胞的崩溃。与文献中可用的实验和理论结果一致，获得的结果证实了聚结对次级空洞存在的敏感性。版权所有©2008 John Wiley & Sons, Ltd

引用次数: 0

A hybrid‐Trefftz finite element model for Helmholtz problem Helmholtz问题的混合- Trefftz有限元模型

Communications in Numerical Methods in Engineering

Pub Date : 2008-12-01 DOI: 10.1002/CNM.1094

K. Sze, Y. Cheung

In this paper, a hybrid-Trefftz four-node quadrilateral element model is formulated for Helmholtz problem. In this model, two Helmholtz approximations are defined. The first approximation is obtained by nodal interpolation, and the second approximation is truncated from a Trefftz solution set. A hybrid variational functional is employed to enforce the equality of and other necessary conditions on the two approximations. From the numerical tests, it can be seen that the hybrid model is markedly more accurate than the conventional finite element model. Copyright © 2008 John Wiley & Sons, Ltd.

引用次数: 15

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