A Three-Dimensional Finite Element Analysis of Heat Transfer in the Forearm

Abstract

The finite element method was used to analyze heat transfer within a section of the forearm while exposed to different ambient conditions and with different metabolic states. The three-dimensional model accounts for the different material properties of bone, muscle and blood and incorporates a single artery-vein pair for counter-current heat exchange. The geometry of the model was developed from anatomical cross-sectional images of the forearm. The model was used to determine the effects or rest vs. exercise, free vs. forced surface convection and 0°C vs. — 20 °C external temperatures. The results of the model were compared to experimental data and the model exhibits qualitatively correct behaviour. This model can be used to study hyperthermia, burns and cryogenic freezing of tissue.     

LISS-DF近端螺钉不同固定方式的有限元分析

目的研究LISS-DF治疗股骨远端骨折近端螺钉不同固定方式对应力分布规律的影响,寻找符合生物力学原理的固定方式,为临床应用提供理论依据。方法在ANSYS9.0软件中建立LISS-DF钢板固定股骨远端骨折（AO/OTA33-A3型）的实体模型和有限元模型。在近端螺钉不同单、双皮质固定方式下,通过模拟生理应力做轴向加载实验并进行有限元计算和分析。结果1、3孔单2、4孔双皮质固定时,近端螺钉最大应力值在不同固定方式中最小为24.21975Mpa,位移值为0.131424um与其它固定方式相当且均较小,说明该固定方式可以取得较好的力学效果。结论近端螺钉靠近骨折端处双皮质固定,其余螺钉间隔单双皮质固定时,可以减少应力集中现象,得到更好的把持力,使固定更牢固,从而降低固定失败的风险性。     

正常乳腺温度分布的有限元分析

基于正常乳腺的解剖学结构和生理学特征,建立了一个乳腺组织多维热传递模型。该模型考虑了代谢产热、血液灌注和动静脉血管与组织间热的相互作用,采用有限元分析方法求解热传导方程,数值模拟正常乳腺的稳态温度分布,着重研究血液灌注和代谢产热对正常乳腺组织温度分布的影响。研究结果可为乳腺疾病的热图像分析提供重要参考。     

Finite Element Analysis of the Contact Mechanics of Ceramic-on-Ceramic Hip Resurfacing Prostheses

<正> Ceramics are good alternative to metal as bearing couple materials because of their better wear resistance. A Finite Element(FE) study was performed to investigate the contact mechanics and stress distribution of Ceramic-on-Ceramic (COC) hip resurfacingprostheses. It was focused in particular on a parametric study to examine the effects of radial clearance, loading,alumina coating on the implants, bone quality, and fixation of cup-bone interface. It was found that a reduction in the radialclearance had the most significant effect on the predicted contact pressure distribution among all of the parameters considered inthis study. It was determined that there was a significant influence of non-metallic materials, such as the bone underneath thebearing components, on the predicted contact mechanics. Stress shielding within the bone tissue was found to be a major concernwhen regarding the use of ceramic as an alternative to metallic resurfacing prostheses. Therefore, using alumina implantswith a metal backing was found to be the best design for ceramic resurfacing prostheses in this study. The loading, bone quality,and acetabular cup fixation conditions were found to have only minor effects on the predicted contact pressure distribution alongthe bearing surfaces.     

应用三维有限元分析髋臼骨结核软骨下骨塌陷的风险

目的建立人体髋臼骨结核三维有限元模型,探讨不同部位髋臼骨结核软骨下骨塌陷的风险。方法通过正常髋关节CT数据,利用Mimics软件和ANSYS有限元软件,建立正常髋关节三维有限元模型（模型A）、髋臼顶部骨结核（模型B）、髋臼中心部骨结核（模型C）、髋臼前部骨结核（模型D）、髋臼后部骨结核（模型E）三维有限元模型,模拟人体单脚站立进行加载,分析髋臼软骨下骨峰值Von Mises应力和初始微动值。结果建立了正常髋关节和不同部位髋臼骨结核三维有限元模型,各模型含节点269284,三维四面体单元184786个。通过加载分析结果显示：与正常髋关节相比,峰值Von Mises应力,依次增加84%、3%、21%、67%;髋臼软骨下骨初始微动值依次增加66%、11%、17%、29%。结论髋臼顶部结核软骨下骨峰值Von Mises应力和初始微动值最大,塌陷的风险最大。     

带有迁移的疟疾病与疟蚊数学模型的交替方向有限元法及其数值分析

对带有扩散问题的Ross-Macdonald模型提出两种交替方向有限元格式,并得到最优的L^2和H^1模估计。     

半月板三维有限元模型的建立

目的：建立膝关节半月板三维有限元模型。方法：拍摄健康成人膝关节CT图像,使用Materialise Interactive Medical ImageControl System 10.0（Mimics10.0）、Freeform Modeling System 10（FMS10）、ANSYS12.0等软件建立半月板三维有限元模型并进行初步生物力学分析验证模型的有效性。结果：建立的半月板三维有限元模型几何形态与实体解剖标本相似性高。初步生物力学分析结果显示模型能准确反映半月板的生物力学特性。结论：采用CT扫描图像建立膝关节半月板三维有限元模型是切实可行的。     

不同材料充填修复下颌第一前磨牙楔状缺损的应力分析

目的研究三种材料对两种角度下颌第一前磨牙楔状缺损的修复效果。方法在下颌第一前磨牙颊颈部深度为1mm,夹角分别为30°、90°的楔状缺损有限元模型上用银汞合金、复合树脂和玻璃离子粘固粉三种材料进行缺损修复,以未修复的楔模型为对照,加载100N轴向力后,利用三维有限元方法进行牙颈部应力分析。结果三种材料修复均改善了缺损牙体的应力集中。银汞合金修复体较其他两种材料承受了更大的应力,使缺损局部牙体应力集中状况得以更多缓解,在角度增加时作用更明显。复合树脂最有效降低牙体内部区域的应力集中。结论楔状缺损充填修复可缓解缺损区牙体硬组织的应力集中,复合树脂相对理想。     

Microstructure-based Finite Element Modelling and Characterisation of Bovine Trabecular Bone

1 Introduction The mechanical behaviour of trabecular bone is dependent on both the properties of individual trabeculae as well as the three-dimensional architecture into which they are arranged. Hence, a comprehensive study of trabecular bone requires the consideration of microscopic as well as macroscopic length scales. Nanoindentation is a technique particularly suited to the mechanical characterisation of single trabecula[1?3] owing to the impracticalities of isolating individual tra- becu…     

过盈植入对种植体-骨界面应力分布影响的三维有限元分析

目的:应用三维有限元分析法研究牙种植体过盈植入对种植体-骨界面接触压力的影响.方法:选择直径为3.3mm的ITI种植体和成人离体下颌骨,模拟种植体植入下颌骨内,过盈量为0.5mm,建立三维有限元模型,应用ANSYS软件分析种植体-骨界面的应力分布情况.结果:种植体周围骨最大应力为48.796 MPa,应力分布均匀.种植体所受应力主要集中于颈部,最大应力值为87.832 MPa.结论:过盈量为0.5mm时,种植体-骨界面所产生的应力值在骨组织所能承受的最大应力值范围内,种植体所受到的应力值远远小于钛的屈服强度,从生物力学角度,周围骨所受应力在骨组织能够承受范围,种植体也不会断裂,过盈联结在临床种植时有其可行性.     

Total Hourglass Control - A Robust Finite Element Formulation for the Calculation of Organ Deformations

For use in a virtual reality based laparoscopic surgery simulator methods have been developed to model the mechanical behavior of soft tissue. Explicit Finite Element analysis turned out to be a robust basis when the approximation of hyperelastic materials is used. To reduce calculation times reduced volume integration schemes were applied, where classical hourglass control leads to drastic errors which make a simulation expanding over a long period of time impossible. Therefore, the total hourglass control scheme was developed and is presented here for several material laws. This new formulation takes the existence of the elastic potential of a hyperelastic material into account and leads to robust simulations without loss of accuracy. This is demonstrated with the off-line simulation of a model of an uterus and its adnexe.     

LISS钢板治疗股骨远端骨折有限元建模及分析

目的建立LISS-DF治疗股骨远端骨折近端螺钉不同单双皮质固定的三维有限元模型,并进行初步生物力学分析。方法提取CT图片相关数据,利用自行编写程序生成命令流文件,建立完整股骨以及16个不同LISS-DF治疗股骨远端AO分型33-A3型骨折的实体模型（钢板和股骨不接触、螺钉分别固定于钢板和股骨）,进行网格划分。分析不同载荷作用下完整股骨和LISS钢板近端螺钉全双皮质固定治疗骨折的模型受力状况。结果建立了相关的有限元模型。不同载荷作用下,LISS钢板近端螺钉全双皮质固定模型和完整股骨的应力集中均位于股骨颈内侧和股骨干外侧中下1/3处。相同载荷作用下,LISS钢板近端螺钉全双皮质固定模型的股骨颈部最大等效应力值略减小,股骨干最大等效应力值明显减小。结论研究建立的三维有限元模型,为应用LISS治疗股骨骨折的生物力学分析提供了良好的实验平台和基础。从生物力学角度而言,LISS-DF近端螺钉全双皮质固定为治疗股骨远端复杂骨折的有效方法。     

下颌第一前磨牙不同角度楔状缺损的三维有限元应力分析

目的探讨不同角度的楔状缺损载荷后应力分布状况。方法建立下颌第一前磨牙颊颈部深度为1mm,夹角分别为30°、60°、90°、120°的楔状缺损有限元模型,以未发生楔缺的完整牙体作为对照,加载100N轴向力后,分析楔状缺损局部、楔缺顶部及楔缺尖端所在横断平面的应力分布状况。结果建立了下颌第一前磨牙不同角度楔状缺损的三维有限元模型;载荷后各楔缺模型颈部缺损区域应力分布趋势均为自牙体外表面向髓腔侧递增;不同角度的楔缺模型在楔缺尖端所在平面上的应力集中于颊侧偏近中区域,接近楔缺顶部直线,完整牙体模型在楔缺尖端所在平面上的应力亦集中于近中颊区域,但应力值明显小于各楔缺模型;在楔状缺损顶部直线,各模型应力的分布规律相类似,最大值均为接近近中边缘的节点,范围分布在20.0～26.4MPa;最小值均为最远中的节点,范围分布在6.4～7.9MPa。所有的缺损模型其应力接近,均明显高于完整牙体的应力分布。结论1 mm深度的缺损情况下,不同角度的模型应力的分布情况接近,均较完整牙体有明显的颈部应力集中,其中最明显的集中点位于缺损内的近中颊侧牙体中。     

Finite elements/Taguchi method based procedure for the identification of the geometrical parameters significantly affecting the biomechanical behavior of a lumbar disc

The aim of this work is to show a quick and simple procedure able to identify the geometrical parameters of the intervertebral disc that strongly affect the behavior of the FEM model. First, we allocated a selection criterion for the minimum number of geometrical parameters that describe, with a good degree of approximation, a healthy human vertebra. Next, we carried out a sensitivity analysis using the ‘Taguchi orthogonal array’ to arrive at a quick identification of the parameters that strongly affect the behavior of the Fem model.     

结合薄层CT技术建立下颌第一前磨牙三维有限元模型

目的结合薄层CT技术建立下颌第一前磨牙三维有限元模型。方法对正常人下颌第一前磨牙进行薄层CT扫描及图像处理,通过Matlab和ANSYS软件建立三维有限元模型,并加载验证模型力学分析的可行性。结果建立了包含髓腔的下颌第一前磨牙的三维有限元模型,得到101564个单元,144053个节点。载荷后的应力分布主要集中在颊尖部位和根尖部位,牙颈部受力较小。结论薄层CT技术与Matlab和ANSYS软件相结合,建立包含髓腔的下颌第一前磨牙的三维有限元模型,精度高、速度快,使用灵活,为后期的楔缺模型建立和分析奠定了基础。     

Three-dimensional Orthotropic Viscoelastic Finite Element Model of a Human Ligament

Ligaments undergo finite strain displaying hyperelastic behaviour as the initially tangled fibrils present straighten out, combined with viscoelastic behaviour (strain rate sensitivity). In the present study the anterior cruciate ligament of the human knee joint is modelled in three dimensions to gain an understanding of the stress distribution over the ligament due to motion imposed on the ends, determined from experimental studies. A three dimensional, finite strain material model of ligaments has recently been proposed by Pioletti in Ref. [2]. It is attractive as it separates out elastic stress from that due to the present strain rate and that due to the past history of deformation. However, it treats the ligament as isotropic and incompressible. While the second assumption is reasonable, the first is clearly untrue. In the present study an alternative model of the elastic behaviour due to Bonet and Burton (Ref. [4]) is generalized. Bonet and Burton consider finite strain with constant modulii for the fibres and for the matrix of a transversely isotropic composite. In the present work, the fibre modulus is first made to increase exponentially from zero with an invariant that provides a measure of the stretch in the fibre direction. At 12% strain in the fibre direction, a new reference state is then adopted, after which the material modulus is made constant, as in Bonet and Burton's model. The strain rate dependence can be added, either using Pioletti's isotropic approximation, or by making the effect depend on the strain rate in the fibre direction only.

A solid model of a ligament is constructed, based on experimentally measured sections, and the deformation predicted using explicit integration in time. This approach simplifies the coding of the material model, but has a limitation due to the detrimental effect on stability of integration of the substantial damping implied by the nonlinear dependence of stress on strain rate. At present, an artificially high density is being used to provide stability, while the dynamics are being removed from the solution using artificial viscosity. The result is a quasi-static solution incorporating the effect of strain rate. Alternate approaches to material modelling and integration are discussed, that may result in a better model.     

基于有限元仿真定量探究贵金属纳米探针自组装诱导的非线性光声效应增强机制

构建高转化效率的功能纳米探针是推动光声分子成像发展的关键。随着光声分子成像技术的发展,具有非线性增强光声转换效率的自组装纳米探针逐渐成为研究热点,然而有关其非线性增强的定量研究尚未见报道。本文以纳米金球为例,利用有限元仿真定量探究金属纳米探针自组装诱导的非线性光热及光声效应,揭示自组装纳米探针光声效应增强规律,为构建具备高转换效率的光声自组装纳米探针奠定了理论基础。     

Finite element analysis of aortic root dilation: a new procedure to reproduce pathology based on experimental data

Sinotubular junction dilation is one of the most frequent pathologies associated with aortic root incompetence. Hence, we create a finite element model considering the whole root geometry; then, starting from healthy valve models and referring to measures of pathological valves reported in the literature, we reproduce the pathology of the aortic root by imposing appropriate boundary conditions. After evaluating the virtual pathological process, we are able to correlate dimensions of non-functional valves with dimensions of competent valves. Such a relation could be helpful in recreating a competent aortic root and, in particular, it could provide useful information in advance in aortic valve sparing surgery.     

Dynamic Modelling of Tooth Deformation Using Occlusal Kinematics and Finite Element Analysis

Background

Dental biomechanics based on finite element (FE) analysis is attracting enormous interest in dentistry, biology, anthropology and palaeontology. Nonetheless, several shortcomings in FE modeling exist, mainly due to unrealistic loading conditions. In this contribution we used kinematics information recorded in a virtual environment derived from occlusal contact detection between high resolution models of an upper and lower human first molar pair (M¹ and M₁, respectively) to run a non-linear dynamic FE crash colliding test.

Methodology

MicroCT image data of a modern human skull were segmented to reconstruct digital models of the antagonistic right M¹ and M₁ and the dental supporting structures. We used the Occlusal Fingerprint Analyser software to reconstruct the individual occlusal pathway trajectory during the power stroke of the chewing cycle, which was applied in a FE simulation to guide the M₁ 3D-path for the crash colliding test.

Results

FE analysis results showed that the stress pattern changes considerably during the power stroke, demonstrating that knowledge about chewing kinematics in conjunction with a morphologically detailed FE model is crucial for understanding tooth form and function under physiological conditions.

Conclusions/Significance

Results from such advanced dynamic approaches will be applicable to evaluate and avoid mechanical failure in prosthodontics/endodontic treatments, and to test material behavior for modern tooth restoration in dentistry. This approach will also allow us to improve our knowledge in chewing-related biomechanics for functional diagnosis and therapy, and it will help paleoanthropologists to illuminate dental adaptive processes and morphological modifications in human evolution.