人体腰椎节段CT图像的反求建模和有限元分析

利用Mimics将人体腰椎CT断层扫描图像反求建模,导入UG并加入包含纤维环及髓核的椎间盘,模拟建立人体腰椎L4-L5节段三维模型,再通过UG与ANSYS Workbench的无缝接口将该模型导入后者,对模型赋值并进行有限元分析,得出人体直立站位时,正常腰椎的椎体位移云图及应力云图.最后将模型进行简化,利用材料力学的理论公式进行强度校核.得知最大位移发生于椎间盘上表面前部,位移值为0.161 mm;最大应力出现在L4下关节突上,应力值为15.073 MPa.有限元分析结果与理论计算结果相对误差较小,表明方法可行,计算结果可靠,为临床医学提供理论参考.     

新型可灌注骨水泥椎弓根螺钉联合普通椎弓根螺钉撑开复位治疗胸腰椎椎体爆裂骨折

目的探讨利用椎弓根螺钉短节段撑开复位联合伤椎新型可灌注骨水泥螺钉灌注骨水泥治疗胸腰椎椎体爆裂骨折的疗效。方法选择32例采用椎弓根螺钉短节段撑开复位联合伤椎新型可灌注骨水泥螺钉灌注骨水泥治疗的胸腰椎椎体爆裂骨折患者;平均随访(11.0±1.5)个月;评估手术前后椎体缘压缩比、椎管侵占率、Cobb角、视觉疼痛评分及Oswestry功能障碍评分等指标。结果平均手术时间(120±10)min,术中出血量平均(350±10)ml。与术前相比,术后椎体缘压缩比、椎管侵占率、Cobb角度、视觉疼痛评分及Oswestry功能障碍评分差异均有统计学意义(P<0.05),且随访中各项指标无显著性改变,末次随访时,影像学复查无螺钉松动、内固定物断裂发生。结论椎弓根螺钉短节段撑开复位联合伤椎新型可灌注骨水泥螺钉灌注骨水泥能够有效治疗胸腰椎椎体爆裂骨折。     

自锚式悬索桥主缆锚固区空间应力分析

目的对典型的锚固区局部节段进行分析,以解决自锚式悬索桥主缆锚固区结构复杂,平面杆系程序无法把握锚固区复杂受力状态的问题,为桥梁设计和施工提供参考依据．方法运用MIDAS／FEA建立浑河景观桥锚固区局部有限元模型,分析最不利索力设计值下的局部应力状态及不同荷载下的极限承载力．结果锚固区在主缆索力T=50000kN作用下,产生的最大位移为4．91mm;锚垫板的索孔周围的von Mises应力在110MPa左右．随着荷载的增加,锚固区von Mises应力不断增大．当索力为设计荷载的3．5倍时,锚固区各板件的应力均达到了468MPa以上,位移最大值为24mm．结论主缆锚固区各构件的刚度和强度均满足要求,锚固区的极限承载力为设计荷载的3．5倍,结构的安全系数较高．     

DN80型燃气电磁阀可靠性分析及结构优化设计

燃气电磁阀是燃气系统中重要的零件,在设计研发阶段对其进行可靠性分析和结构优化是必要的.基于Unigraphics NX软件建立了其三维模型,结合Ansys workbench的geometry几何模块和static structural静力分析模块对其进行有限元分析,得到其等效应力云图和变形最大值及其位置和可靠度数值,发现其等效应力位置和变形最大位置出现应力集中现象,对该关键位置进行结构优化,并进行有限元分析发现,通过结构优化,等效应力由65.797 MPa降低为13.575 MPa,最大的变形量为由0.11092 mm降低为0.0043326 mm,可靠度由0.942提高到0.995,优化后的电磁阀整体性能得到提高.研究方法为燃气电磁阀的设计与优化提供了依据,节省研发成本,缩短设计周期.     

基于有限元的热轧H型钢万能精轧机结构设计与优化(103)

运用PRO/E软件建立轧机三维模型,并借助于ANSYS有限元软件,分析轧机的变形参数.优化后的轧机具有一定可靠性,轧机最大位移为0.049 mm,最大应力3.181 MPa,刚度高,弹性变形小.     

110kV户外GIS设备模块化装配式混凝土工字形基础研发

根据变电站户外GIS设备的布置形式及运行特点,提出设备模块化装配式混凝土工字形基础。针对已经投建的110kV变电站户外GIS设备进行模块化装配式混凝土工字形基础设计,采用有限元方法进行了两种极限荷载工况下的分析论证。结果表明,钢筋的最大Mises应力和预制件混凝土的最大主压应力均远低于钢筋屈服强度设计值和混凝土的抗压强度设计值;预制件混凝土的最大主拉应力为2MPa,大于混凝土抗拉强度设计值,但低于混凝土抗拉强度标准值,不会开裂;基础最大竖向位移分别为7.663mm和5.391mm,远低于DL/T5457—2012中容许值200mm的要求;GIS设备装配式基础整体最大沉降差分别为2.150mm和1.896mm,满足DL/T5457—2012中容许沉降差或倾斜0.002L(L为基础对应方向长度)以内的要求。     

多腔体柔性机械手指设计与弯曲变形研究

设计一种柔性机械手指,通过3D打印机打印了柔性机械手指模具,并以硅胶为原料制备了柔性机械手指;通过拉伸试验得到了硅胶材料的应变能密度函数的模型参数C_(10)和C_(20),并用Solidworks软件建立柔性机械手指三维模型,用ABAQUS软件分析了该柔性机械手指在压力为-0.02~0.05 MPa时的应力与应变。结果表明,当压力为-0.02 MPa时,最大应力与最大应变分别为-8.866 MPa和-0.564;当压力为0.05 MPa时,最大应力与最大应变分别为2.981 MPa和0.711。建立柔性机械手指试验装置,获取了柔性机械手指在不同压力下的弯曲变形情况和手指末端的位移。结果表明,其横向最大位移为7.60 mm。     

基于ANSYS Workbench的某越野车车架有限元分析

针对越野车复杂的行驶条件对车架结构苛刻的要求,以越野车车架为研究对象,采用ANSYS软件建立了与某越野车车架结构充分近似的车架三维模型,并根据模态分析理论对其进行了有限元模态分析,获得了该车架的前六阶模态参数.理论值与实验值比较表明,车架能够在一定程度上避免共振现象,模型建立准确,为结构车架的动态设计提供了理论依据.同时对车架进行刚度和静强度分析,由位移、应力云图获得了车架发生应力集中区域.结果表明:第3根横梁和第4根横梁之间的连接处应力值远低于屈服极限,可以考虑梁变细或者钢板缩减壁厚,而在第2,第3根横梁与纵梁相接处应力值大于许用应力值,可以使横梁应加粗或连接处使用加厚焊.实验研究分析为车架的改进和优化提供了参考依据.     

位于“V”型峡谷桥址的连续刚构桥风冲击模型与抗风设计

风荷载作用效应的精确分析是对＂V＂型峡谷桥址处平衡悬臂工法施工的高墩大跨连续刚构桥的结构安全性的重要保证。以1座最高主墩153 m,跨径组合85 m＋4×160 m＋85 m的连续刚构桥为例,依据其桥址处的风环境确定了上、下部结构的风冲击模型,并在最大悬臂工况下与静风荷载进行对比分析后对桥的抗风构造进行了优化。结果表明：高墩的位移与应力,构造的动风载模型效应比静力风载的大3倍以上;增加的风撑横系梁构造可最大减小墩顶的应力与位移的73.9%;墩顶在最大悬臂阶段出现侧向最大位移11.9 cm,桥墩墩底截面拉应力1.65 MPa,虽未超过容许值,但应考虑采取适当的抗风措施。     

基于正装迭代法的三塔结合梁斜拉桥计算分析

为了使斜拉桥建成后受力合理,掌握施工过程中桥梁的内力特性,本文以武汉二七长江大桥为依托,基于正装迭代法,运用MIDAS/CIVIL有限元分析软件,通过建立三塔结合梁斜拉桥双主梁空间有限元模型,分析其各施工阶段及成桥阶段的内力、位移和索力,经过与合理成桥状态进行对比分析,最终确定各施工阶段的节段标高、索力及主梁内力.计算结果表明:合理施工索力与合理成桥索力相比,误差均在±5％范围内,主梁最大抛高40.3 cm,混凝土桥面板未出现拉应力,且最大压应力为8.8 MPa,钢主梁下翼缘最大压应力为159MPa,说明三塔结合梁斜拉桥施工受力合理,斜拉桥索力、主梁内力和位移均满足设计规范要求,计算结果可为三塔结合梁斜拉桥施工提供参考.     

Bolt support mechanism based on elastic theory

Mechanical model of anchorage surrounding rock considering tray effect was established based on elastic theory, in order to study the mechanism of bolt supporting. Elastic solutions of normal force at point in the interior of a semi-infinite solid were obtained by means of classical displacement function method in elasticity. The factors which influence stress of bolted surrounding rock, such as the length of bolt and tray effect, were analyzed. The absolute value of stress along bolt axes decreased rapidly with an increase in radical distance and the maximum appeared near ends of bolt. With increasing radical distance, the value of radical stress changed from positive to negative roughly and then increased to zero, with maximum at the middle of bolt. The evolution of hoop stress as radical distance increasing was similar with stress along bolt axes. With an increase in depth, the radical effect ranges of all normal stress components were reduced. These suggest that the effect from tray on stress along bolt axes of bolted surrounding rock could be neglected, except near surface of surrounding rock.     

Numerical simulation for sheet metal forming process of 16Mn blade of large concrete-mixer truck

A finite element analysis method was used to simulate the stamping process of the blade of a large concrete-mixer truck. The updated Lagrange method and the elasto-plastic constitutive equation were adopted to solve the large strain and displacement deformation of the blade. A modified Coulomb friction model was used to solve the sliding contact between the blade and the dies. The yon Mises stress distribution in the blade, the spatial displacement variation and the spring-back of the typical node were investigated in the simulation. The yon Mises stress in the blade where the spring-back occurs is lowered from 463.0 MPa to 150.0 MPa before and after the spring-back.A typical node in the blade has a 3.33 mm spring-back in Z direction. The results of the experiments agree well with the simulation. The analysis results are valuable for designing optimal tool dies.     

Mechanical mechanism analysis of tension type anchor based on shear displacement method

Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of anchorage segment was analyzed. Shear stress-strain relationship of soil surrounding anchorage body was simplified into three-folding-lines model consisting of elastic phase, elasto-plastic phase and residual phase considering its softening characteristic. Meanwhile, shear displacement method that has been extensively used in the analysis of pile foundation was introduced. Based on elasto-plastic theory, the distributions of displacement, shear stress and axial force along the anchorage segment of tension type anchor were obtained, and the formula for calculating the elastic limit load was also developed accordingly. Finally, an example was given to discuss the variation of stress and displacement in the anchorage segment with the loads exerted on the anchor, and a program was worked out to calculate the anchor maximum bearing capacity. The influence of some parameters on the anchor bearing capacity was discussed, and effective anchorage length was obtained simultaneously. The results show that the shear stress first increases and then decreases and finally trends to the residual strength with increase of distance from bottom of the anchorage body, the displacement increases all the time with the increase of distance from bottom of the anchorage body, and the increase of velocity gradually becomes greater.     

正畸中牙根形态对牙根应力分布的影响

对比分析正常形态和牙根弯曲的牙齿在正畸力作用下牙根及牙周膜的应力分布,为临床上不同形态牙齿的正畸方案提供参考.选用正常形态和牙根弯曲的上颌侧切牙,考虑相同的牙槽骨,基于CT扫描分别建立三维有限元模型,施加与整体移动、倾斜移动和压入移动相对应的载荷,对两个模型在相同载荷作用下牙根和牙周膜的von Mises应力进行比较.结果表明,3种载荷工况下,两种形态牙根的应力分布规律相似,整体移动和倾斜移动的载荷作用下,应力都是自根尖向牙槽骨嵴顶处逐渐增大;压入移动的载荷作用下,在远中根尖附近都出现一个应力集中区,牙根应力的最大值就在这个区域.然而,各载荷工况下,弯曲牙根模型的牙根和牙周膜的应力值都明显高于正常形态牙根模型,特别是压入移动,很可能导致牙根吸收.牙根弯曲会导致牙根及牙周膜应力的增高,正畸治_疗中应考虑牙根形态异常对某些移动方式不利的情况,以采取相应的措施.     

基于两种本构模型的堆石坝应力变形比较研究

采用邓肯E-B模型与椭圆-抛物双屈服面模型对两岔河心墙堆石坝进行有限元应力变形分析,比较两种本构模型在正常高水位的满蓄期计算得到的坝体应力应变差异。结果表明:(1)两种模型计算的坝体沉降较为接近,邓肯E-B模型计算最大沉降稍小;邓肯E-B模型计算的顺河向水平位移与双屈服面模型相比,上游位移与下游位移均偏大。(2)受心墙拱效应影响,无论邓肯E-B模型还是双屈服面模型,心墙内的主应力均比过渡层小,小主应力均为正,心墙内均未出现拉应力。相比于双屈服面模型,邓肯E-B模型计算的心墙应力受心墙拱效应更为明显。(3)满蓄期防渗墙小主应力在左右岸角部出现拉应力,两种模型计算的拉应力区分布规律基本一致,但双屈服面模型计算的拉应力的值及变化梯度均大于邓肯E-B模型。     

地下空区激光三维探测及稳定性分析

为了解决地下空区对露天矿安全生产的影响,针对洛钼集团露天开采境界下覆不明空区,利用激光三维扫描系统通过地表钻孔对空区进行精确三维探测,把激光三维探测的数据导入SURPAC建立空区三维块体模型,研究了SURPAC和FLAC~(3D)的数据转换方式,并编制相应程序把空区三维块体模型导入软件FLAC~(3D)进行稳定性数值分析.计算结果显示:该空区模型内各单元内的不平衡力趋近于0;节点(6066,4775,1430)处的Z方向位移趋近于恒定值;初始平衡状态下围岩最大位移量约为0.086 m;围岩中最大拉应力为1.52 MPa,应力集中区最大压应力为12.37 MPa,均小于岩体的抗拉、抗压强度.由此表明,该空区上方地表运动停止,空区上方围岩不会发生拉裂破坏,空区目前处于稳定状态.     

土坝防渗墙设置摩擦单元对墙体应力变形的影响

以某水库副坝混凝土防渗墙为例,采用二维非线性土石坝有限元计算程序对其典型剖面进行了有限元计算,重点分析了设置摩擦单元对墙体应力变形的影响.最后指出:设置摩擦单元后,墙体位移明显减小,大小主应力有所改变,最大应力值发生位置没有改变.     

Augmentation of pedicle screw fixation with calcium phosphate cement

To determine whether a biodegradable calcium phosphate cement (CPC) provides significant augmentation of pedide screw fixation or not, an in vitro biomechanical study was carried out to evalwate the biomechanical effea of CPC in the restoration and angmentation of pedide screw.fixation. Axial pullout and cyclic beruding resistance test were employed in the experiment, and polymethylmethacrylate (PMMA) was chosen as control. The results demonstrate that the pullout strengths following CPC restoration and augmentation are 74% greater on an average than those of the control group, but less than those of PMMA restoration group ard aygmentation group respectively ( increased by 126% versus control). In cyclic bending resistance test, the CPC augmented screws are found to withstand a greater number of cycles or greater loading with less displacement before loosening,but the augmentation effect of PMMA is greater than that of CPC.     

Static Performance and Fracture Numerical Analysis of 301L/Q235B Dissimilar Steel Resistance Spot Welded Joints

301L/Q235B异种钢电阻点焊接头静力学性能及断裂数值分析

王昌坤1,2*,刘慧玉1,范佳斐1,左银龙3,胡立国4

（1.北京交通大学 机械与电子控制工程学院,北京 100044;2.中铁上海设计院集团有限公司,上海 200070;3.中车唐山机车车辆有限公司,唐山 063000;4.中车长春轨道客车股份有限公司,长春 130062）

摘 要：对301L-DLT/Q235B异种钢2.0 mm板不同熔核尺寸的电阻点焊拉剪试样进行静拉伸试验。用有限元软件模拟出了点焊接头的力-位移曲线,分析了点焊接头拉伸断裂过程的应力应变分布和断裂演变过程。熔核硬度高于板材和热影响区。在静拉伸载荷作用下,电阻点焊接头拉伸过程的应力、应变随位移增大呈指数关系增长,301L板加载侧熔核边缘的应力值最大。点焊接头以熔核拔出断裂失效试样的静拉伸强度和塑性变形量优于以界面断裂模,由熔核界面断裂向拔出断裂转变的搭接面临界熔核直径为7.12 mm,约5 .

关键词：301L/Q235B异种电阻点焊;静力学性能;断裂模式;有限元分析