人体脊柱T12-L2活动节段三维重建及扭转特性研究

研究人体脊柱T12-L2活动节段的三维重建方法以明确脊柱该节段扭转特性对人体脊柱胸腰段诊断具有重要的意义。本文探讨了基于mimics模型,利用SolidWorks实体编辑方法,对人体脊柱T12-L2活动段进行三维实体重建,并对重建后的人体脊柱胸腰段模型,利用有限元方法进行扭转特性分析。分析结果认为:建立精确的人体脊柱三维实体模型和研究人体脊柱的扭转特性,是进行胸腰段疾病诊断和腰部手法治疗的关键因素。本文研究内容为人体脊柱胸腰段疾病诊断和腰部手法治疗提供一定借鉴作用。     

个性化三维矫形支具的设计及其生物力学研究

以个性化三维矫形支具的设计为研究目标,以AIS患者的CT断层数据为基础建立包含胸腰骶、胸廓和骨盆的三维几何模型,继而构建出一例完全基于人体解剖结构的有限元模型。在此基础上研究个性化三维矫形支具的快速设计方法,通过合理设置衬垫分布模拟临床脊柱受力,分析不同矫形力及作用位置对矫形疗效的影响与评估,并根据临床实际进行支具矫形效果的生物力学分析,确定最优支具设计方案。为个性化支具的设计提供了一种切实可行的方法,可以提高支具三维矫正效果。     

基于CT图像人体脊柱腰椎节段逆向工程研究

利用逆向工程软件Mimics,基于CT断层扫描图像,重建人体脊柱腰椎节段三维几何模型,经ANSYS转化建立脊柱腰椎L1-L3的理想三维有限元模型,然后在Mimics中对所建立的有限元模型赋材质,实现了非均匀材质的骨组织赋值问题.该腰椎节段三维有限元模型高度模拟腰椎结构与材料的特性,具有结构完整、空间结构测量准确度高、单元划分精细、重点突出等优点.该模型可进行任意旋转观察,可任意切割,并可通过调整模型的几何及材料参数、施加不同的载荷与边界条件模拟不同实验状态.该数字模型能够以不同的文件格式输出,可用于计算机辅助设计、快速成型、有限元分析等领域的研究.     

后路脊椎截骨治疗先天性脊柱侧凸合并脊髓纵裂畸形

目的:分析后路脊椎截骨治疗先天性脊柱侧凸合并脊髓纵裂畸形的效果与安全性,总结治疗体会。方法:2013年1月至2016年1月行后路脊柱截骨术的17例先天性脊柱侧凸合并脊髓纵裂畸形患者,记录其手术情况及术后并发症发生情况,于术后6月、12月随访观察影像学指标变化,于12个月进行全部患者脊柱裂神经功能评分(SBNS)、疼痛患者疼痛视觉模拟评分(VAS)。结果:17例患者手术均顺利完成,术后共2例患者发生并发症,对症处理后均痊愈。与术前比较,末次随访全部患者SBNS评分、疼痛患者VAS评分均明显下降,冠状面主弯Cobb角、矢状面后凸Cobb角、冠状位躯干偏移及矢状位躯干偏移亦明显下降,差异均有统计学意义(P<0.05)。结论:后路脊椎截骨治疗先天性脊柱侧凸合并脊髓纵裂畸形的安全性良好,在保证侧凸矫形率、促进神经功能恢复方面效果确切。     

脊柱腰骶段的机械简化及有限元分析

根据医学上人体脊柱腰骶段椎体、椎间盘、小关节、关节囊等组成部分的结构形态及连接关系,首先将腰骶段模型进行机械简化;然后,参照临床解剖数据,采用三维设计软件SolidEdge建立腰骶段三维模型,并保存为Parasolid中间格式;最后,将模型导入有限元分析软件ANSYS的Workbench模块中,分析模型在受扭矩及轴向载荷后的变形及应力分布情况。分析结果与病理学上的结论相一致。     

足三维有限元建模及鞋垫腰窝高度对足舒适性的影响研究

探讨建立足部三维有限元模型的方法,并建立一系列腰窝高度的鞋垫模型,应用模型模拟分析得出足底压力分布及骨骼受力情况,找出穿着最舒适时的腰窝高度。基于CT数据,建立包括骨骼,软骨,软组织,韧带和足底腱膜,考虑材料非线性的足部模型。截取腰窝曲面,建立5个腰窝高度的鞋垫模型。利用完整的有限元模型对行走中立期进行了静态模拟。有限元分析结果表明,满腰窝高度的鞋垫会对第二跖骨造成压迫,降低舒适感;综合舒适度函数可得出1/2-3/4腰窝高度的鞋垫具有最佳的舒适性,与实验得出的结论相同。提出从足舒适度角度设计鞋垫的腰窝高度时应综合考虑足底压力分布和跖骨应力,为设计鞋垫和研究足部各种临床状况提供了参考。     

轿车侧围B柱拐角段三维密封分析

轿车车门密封系统决定整体关门力,直接影响开合便捷性。传统改善关门轻便性的方法需要多轮试制、反复试错,效率较低、周期较长。由于侧围B柱拐角段安装轮廓特殊,压缩力方向多变,传统二维有限元仿真无法真实反映其复杂受力变形状态,进而影响整体密封系统的分析准确性。考虑密封材料的超弹性体模型,建立侧围B柱拐角段三维密封有限元模型,分析旋转关门动态过程中,B柱大曲率拐角段对密封压缩负荷的影响。对比密封系统压缩负荷实验,该侧围B柱拐角段的三维密封分析误差为10.73%,满足工程应用的精度要求。     

侧架结构的改进

在solidworks中建立某种转向架中侧架的三维模型,采用cosmosworks对该侧架的三维模型进行有限元分析;对其分析结果与实测值进行比较,对侧架的结构进行改进,改善了侧架的受h情况.     

人体脊柱腰椎节段三维有限元模型的研究与分析

该研究利用Dicom数据,结合逆向工程软件建立了人体脊柱腰椎节段(L1～L5)完整、真实的三维有限元模型,其模型高度模拟了腰椎的结构几何非线性、材料非线性与接触非线性,具有结构完整、空间结构的测量准确度高、单元划分精细、重点突出等优点,并模拟了腰椎节段前屈与后伸的生理活动.分析结果表明:椎体、小关节应力、椎弓根应力后伸位大于前屈位;椎间盘内部应力前屈位大于后伸位;且均由上至下呈逐渐增大的趋势.其结果能够反映人体腰椎节段的正常生理功能.文中研究的腰椎节段三维有限元模型可以用于模拟脊柱腰椎节段的生物力学特性研究,以应用于脊柱腰椎节段损伤、疾病的诊断与治疗.     

航空发动机带凸肩叶片的强度计算方法研究

采用商业有限元软件在柱坐标系下,建立符合实际工作情况的叶片凸肩部位三向位移协调边界条件,并在此基础 上计算叶片凸肩接触面的平均挤压应力。为建立叶身盆侧、背侧的气动压力边界条件,还提出一种三维曲面压力插值技 术,不仅较好解决了凸肩叶片强度计算中的气动压力边界条件的施加,而且使得商业有限元软件在此工程领域得以应 用。     

双圆弧弧齿锥齿轮的精确建模及其弯曲强度的有限元分析

利用切齿啮合过程中得到的实际包络的双圆弧弧齿锥齿轮齿面方程,通过三维CAD软件绘制了双圆弧弧齿锥齿轮的实际加工齿面,进而通过此曲面得到了实际加工后的双圆弧弧齿锥齿轮轮齿的三维实体模型。利用CAD软件与有限元分析软件的接口,将所建立轮齿的实体模型导入有限元分析软件,对其进行网格划分。最后对得到的有限元模型施加三组载荷,进行了双圆弧弧齿锥齿轮齿根弯曲应力的有限元分析计算。     

顶驱中心管螺纹力学行为模拟及优化研究

针对顶驱中心管螺纹粘扣、断裂等问题，基于弹塑性理论、von Mises屈服准则以及中心管材料本构模型试验研究结果,建立了扭矩作用下的二维、三维有限元模型，并通过实验结果与数值模拟结果验证有限元分析的可靠性，对比二维、三维的分析结果验证二维轴对称模型方法的可靠性，获得了中心管螺纹接头的应力分布规律和力学特性，指出紧扣扭矩对螺纹连接强度影响极大。在此基础上，结合现场失效的螺纹接头，对螺纹锥度、螺距以及有效螺纹牙长度3个参量进行敏感性分析，综合考虑连接强度以及生产成本推荐了参量最优值。     

基于ANSYS的汽车门锁机构锁紧工况的有限元分析

运用Pro/E软件对汽车门锁机构进行3D建模,然后运用ANSYS软件对得到的汽车门锁机构模型进行了有限元分析。根据工程实际简化几何模型,完成了棘轮棘爪机构的单元的选择、设置实常数和材料属性、划分网格、创建节点组元、施加边界条件等有限元建模过程,得出系统应力应变分布情况,分析结果与经验相符。     

电动铲运机桥壳的有限元分析

针对某型号电动铲运机桥壳强度计算的工程问题，利用面向特征的建模方法，建立了桥壳的三维几何模型和有限元分析模型，得出了有限元分析结果；并通过与简化的强度计算方法进行比较，说明了有限元计算方法在工程分析中的可靠性以及它具有的明显优势。     

In vitro validated finite element method model for a human skull and related craniofacial effects during rapid maxillary expansion

This paper presents the biomechanical effects on the craniofacial complex during rapid maxillary expansions (RME), by using an in vitro experiment compared with a three-dimensional (3D) finite element model of a human skull. For this purpose, a dry human skull with artificially constructed teeth was used. In addition, a 3D finite element model including the craniofacial sutures was developed based on computed tomography (CT) scans. Initially, two types of models were analysed. In the first model, the total activation of the jackscrew device was applied in one step. In the second model, more steps were applied, taking into account the phenomenon of stress relaxation during RME treatment. Afterwards, a parametric analysis of the finite element method model was performed using three more models in order to evaluate the influence of craniofacial sutures. Both in vitro and finite element results refer to the openings of four critical points (MI, UM, EM, and CN) on the left and right maxilla. Results show that the maxillae open in a pyramidal shape and that the degree of sutures ossification influences the displacement distribution on the craniofacial complex much more than the phenomenon of stress relaxation. The areas of the maximum stresses and displacements were also determined.     

自动抱夹横移机手部抱夹装置的动力学仿真分析

以自动抱夹横移机手部抱夹装置为研究对象,利用UG软件建立各零/部件的三维几何模型,在ANSYS软件中建立各零/部件的有限元模型,并采用弹簧阻尼器单元COMBIN14建立各结合部的动力学模型,从而建立手部抱夹装置整体有限元模型,进行模态分析和谐响应分析,得到手部抱夹装置前六阶模态,识别手部抱夹装置的薄弱环节,为手部抱夹装置的优化设计提供科学依据.     

Finite element modelling of skeletal muscles coupled with fatigue

In this study, Hill's muscle theory coupled with fatigue was proposed to describe mechanical behaviours of skeletal muscles. The force developed by a fatigued muscle was described by a muscle fatigue formula which was a time function of the activation α_a and the stretch λ. The modified Hill's muscle theory was hence incorporated into a three-dimensional (3D) finite element model using the PAK finite element code. In this paper, the theoretical derivation of the 3D muscle model was firstly described. After presenting the method of establishing the finite element programme, a case example of studying the mechanical response of a frog gastrocnemius muscle was used to illustrate the applicability of the proposed methodology. The effects of the muscle fatigue on the deformation as well as the stress and strain distribution of the frog muscle subject to a cyclic activation function have been determined. An experiment capturing the real-time shape change of a frog muscle was also conducted to assess the applicability of the proposed method. A comparison between the deformed shapes of the predictive model and the frog muscles was also made. It was shown that the method is capable of providing a reasonable model for describing the mechanical behaviour of skeletal muscles.     

The plastic collapse and energy absorption capacity of egg-box panels

The plastic collapse response of aluminium egg-box panels subjected to out-of-plane compression has been measured and modelled. It is observed that the collapse strength and energy absorption are sensitive to the level of in-plane constraint, with collapse dictated either by plastic buckling or by a travelling plastic knuckle mechanism. Drop weight tests have been performed at speeds of up to 6 ms⁻¹, and an elevation in strength with impact velocity is noted. A 3D finite element shell model is needed in order to reproduce the observed behaviours. Additional calculations using an axisymmetric finite element model give the correct collapse modes but are less accurate than the more sophisticated 3D model. The finite element simulations suggest that the observed velocity dependence of strength is primarily due to strain-rate sensitivity of the aluminium sheet, with material inertia playing a negligible role. Finally, it is shown that the energy absorption capacity of the egg-box material is comparable to that of metallic foams.     

3D FEM simulation of milling process for titanium alloy Ti6Al4V

Milling is used as one of the most important tools with the complex tool geometry in industry. However, the complex milling process cannot be simulated by 2D finite element method. Therefore, a more real 3D finite element model (FEM) for the complex milling process of titanium alloy Ti6Al4V is firstly developed using the finite element software ABAQUS. This model takes into account the dynamic effects, thermomechanical coupling, material damage law, and contact criterion. Firstly, the Johnson–Cook material constitutive equation was proposed, considering the effects of strain, strain rate, and temperature on material properties. Secondly, the damage constitutive law was adopted as the chip separation criterion. Then, the simulation for the milling process of Ti6Al4V was conducted through ABAQUS based on the established 3D FEM. Finally, chip formation, stress distribution, cutting force, and milling temperature were obtained. Further, a series of milling experiments of Ti6Al4V were carried out to validate the simulation results. It confirms the capability and advantage of 3D FEM simulation in the complex milling process of titanium alloy.