关键词： DH780+Z增强成形性双相钢   液压胀形试验   大应变   硬化模型   有限元  

摘要： 采用单向拉伸试验得到的真实应力-应变数据标定了Hollomon、LIAN、Swift、Hockett-Sherby、Voce及EI-Mgad等硬化模型。进行了液压胀形试验,获取了大应变范围下的等效应力-应变数据,对比分析了各硬化模型的预测精度。进行了弯曲试验并采用标定的硬化模型进行了弯曲过程有限元模拟。结果显示,对于DH780+Z材料,在均匀变形阶段,各硬化模型的表征精度较高,但外推的大应变范围下各模型预测结果差别较大,等效应变为1时,预测的最大、最小应力差达745.5 MPa。液压胀形获取的等效应力-应变数据显示,大应变范围下硬化趋势与各硬化模型预测均不同。对于弯曲变形,在不考虑包申格效应的情况下,EI-Mgad及Swift/Hockett-Sherby(权重系数a=0.695)模型预测的DH780+Z弯曲方向外表面塑性应变精度最高,偏差分别为-0.35%及0.003%。

关键词： 压力性尿失禁   TVT   TVT-O   有限元分析   生物力学  

摘要： 目的用有限元分析的方法模拟老年女性压力性尿失禁(Stress urinary incontience,SUI)常见吊带手术:经耻骨后无张力尿道吊带(Tension-free vaginal tape,TVT)和经闭孔无张力尿道吊带(Tension-free vaginal tape-obturator,TVT-O),评估它们在尿道不同位置的治疗效果。方法根据一名无盆底疾病女性的磁共振(MRI)图像构建盆腔几何模型。将老年阴道组织薄弱认定为组织刚度降低,施加腹压模拟valsalva运动并分别在尿道近端、中远端、远端放置TVT与TVT-O,得出力学数据。结果尿道近端的吊带会导致α角与膀胱颈位移小于正常值。“漏斗”现象在吊带位于尿道近端与中远端时消失,位于尿道远端时依然存在;不同位置吊带与尿道之间的压强大小关系为:近端>中远端>远端。结论尿道近端(30%)的吊带容易导致尿道过紧,引起术后并发症;尿道远端(80%)的吊带治疗效果不佳;尿道中远端(60%)的吊带治疗效果好、术后并发症发生率低。尿道中远端放置TVT应该作为老年女性SUI手术的首选方法。

关键词： 微引擎   燃烧压   活塞动态响应   理论计算   有限元分析  

摘要： 针对微引擎燃烧效率低和扫气短路损失大的问题,对微引擎燃烧压和活塞动态响应进行了理论计算与分析,通过应用理想空气奥托循环模型,对微型往复式引擎的燃烧压进行了理论推导,并计算得出最大燃烧压约为250 kPa。使用ANSYS软件进行有限元法(FEM)分析确定了弹簧宽度为200μm、长度为12 mm、折回次数为10的活塞结构,以确保活塞在最大燃烧压下能够实现预期的动态响应。活塞的时程响应分析表明,活塞能够准确跟随燃烧压的周期性变化,其最大行程长度达到2.03 mm。模态分析结果进一步验证了活塞的高响应特性,能够适应燃烧压的不断变化。活塞的高响应特性不仅有助于提高燃烧效率,还有助于提升整个微引擎的性能和效率。此外,利用ANSYS/FLOTRAN软件对气缸和活塞分流器尺寸进行了FEM流体分析,优化了形状参数以消除燃料气体的短路现象,从而有效提升扫气效率。验证了所提出设计方案的有效性,并且为微引擎在微型系统中的应用提供了参考。

关键词： Runoff   Groundwater seepage   Local factor of safety   Indirectly coupled model   Rainfall  

摘要： An indirectly coupled model, integrating the Richards' equation, the diffusion wave approximation equation, and the Green-Ampt infiltration model, has been developed to efficiently analyze surface flow and groundwater seepage under heavy rainfall conditions. Model effectiveness was validated through rigorous soil column and slope model experiments. Using this model, the sensitivity of slope stability to rainfall intensity and soil permeability heterogeneity was investigated utilizing local factor of safety (LFS) analysis. Increased rainfall intensity was found to notably impact slope stability, while the influence of permeability anisotropy on stability varies with slope steepness. This method was subsequently applied to analyze the slope stability of a soil heritage site impacted by extreme precipitation during Typhoon Lekima. Preliminary comparisons revealed that the steady-state average infiltration rate, when surface runoff was considered, was higher than the rate computed without it. Additionally, potential hazard zones were identified near areas with maximal water accumulation and runoff velocity when surface runoff was considered. Building on these findings, LFS changes were evaluated at various locations during and after 20 h of rainfall. The study indicated decreased stability in the shallow layer during rainfall, with slight improvement in the deeper layer. Post-rainfall, the shallow layer stability recovered, whereas the deeper layer stability declined due to increased depth of rainwater infiltration. The results suggest that the indirectly coupled model, combined with LFS analysis, is a robust method for effectively evaluating shallow layer stability of slopes in extreme rainfall conditions.

关键词： Shear flow  

摘要： Objective Small incision lenticule extraction (SMILE) has garnered significant attention due to its advantages of small incisions, absence of corneal flaps, and preservation of cornea integrity. During SMILE, a laser is used to cut the corneal stromal layer, and the refractive lenticule is obtained and removed to correct myopia. The corneal incision alters the corneal structure, reducing its biomechanical strength and resistance to deformation. Latrogenic keratectasia occurs when the biomechanical strength is below the threshold required to maintain corneal shape. Thus, investigating the biomechanical changes in the cornea after SMILE surgery has become a key research area in the field of refractive surgery. Elastic modulus is a primary factor affecting the biomechanical changes of the cornea. Some studies have indicated changes in corneal elastic modulus after SMILE. However, there are notable variations among patients. The refractive lenticule and corneal cap thickness differ considerably in clinical practice. Consequently, the quantitative analysis of the corneal elastic modulus after SMILE remains controversial. This study aimed to quantitatively examine the influence of corrected refraction and corneal cap thickness on the corneal elastic modulus using the finite element method (FEM) after SMILE. Methods This study used Corvis ST technology and corneal topographic maps. A parametric modeling approach was applied to reconstruct a preoperative three-dimensional geometric model of rabbit eyes, including the lens, ciliary body, and aqueous humor. Additionally, the cutting surface and incision were fitted using point cloud data. Seven postoperative SMILE models with different corrected refractions were created while maintaining the same corneal cap thickness. Furthermore, four models with different corneal cap thicknesses were reconstructed with corrected refraction being maintained in the range of the −3 D and −6 D. The finite element software COMSOL Multiphysics 5

关键词： Impellers  

摘要： A single-passage fluid-thermal and full-passage thermo-structural coupling modeling method was established， and three-dimensional fluid-thermal-structural coupling analysis of a turbojet engine was carried out. Compared with the method without coupling， there were great differences in temperature， stress， and deformation. The temperature of the compressor impeller of the fluid-thermal coupling method was 15 K lower than that of the uncoupled，and the temperature of the three-stage diffuser was 10—20 K lower than that of the uncoupled. The maximum equivalent stress of the compressor impeller of the thermal-structural coupling method was 31 MPa (4.7%) smaller than that of the uncoupled，and the radial deformation of the compressor impeller was 0.02 mm (11.1%) larger than that of the uncoupled. The tip clearance variation of the turbine at the design point predicted by the fluid-thermal-structural coupling analysis was 0.54 mm. This method realized the analysis of the temperature field，stress field，and deformation field of the whole engine，comprehensively evaluated the strength and deformation of components，and provided data support for component optimization. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： 行星齿轮   多动力耦合   数学图谱   定量分析  

摘要： 【目的】为了对行星齿轮多动力耦合系统各元件的运行参数及相互关系进行直观地定量分析，提出了一种数学图谱分析方法。【方法】以某型载货车用行星齿轮混合动力系统为研究对象，对该方法进行了论述，推导了该系统各元件的运动学和力学关系；采用Matlab软件建立了数学图谱；对起步加速工况中的模式切换秩序和路径规划进行了定量分析；对不同坡度和车速条件下巡航工况的最优巡航油耗的获取进行了定量分析；基于上述分析提出了系统架构优化措施，并进行了性能仿真对比。【结果】本方法可直观且定量地获得模式切换秩序、工况点间的路径规划和巡航工况下的最佳油耗点。提出的优化措施经仿真验证具有一定的性能提升效果，有助于系统控制策略改善和标定开发。

关键词： 矿用电缆   感应电压   磁耦合谐振   井下检测   感应电场-磁耦合谐振  

摘要： 高瓦斯矿井下供电电缆发生故障导致采煤机等设备停工，严重影响生产效率和经济效益。当前，地面电缆故障检测常用的高压脉冲闪络法、行波反射测距法等均不适用于井下检测环境，因此本文提出了一种感应电场-磁耦合谐振式矿用电缆故障井下综合检测新方法。在低频正弦激励源条件下，建立感应电场-磁耦合谐振式电缆故障综合检测方法数学模型，采用多物理场仿真软件COMSOL对电缆开路短路故障情况下的电磁场量求解，得到电场强度、磁场强度的二维分布以及探测线圈感应电压的一维曲线，仿真及实验测定了所使用线圈开路和短路时的感应电压随提离高度的变化曲线。研究结果表明，基于低频感应电场-磁耦合谐振式综合方法进行矿用电缆故障井下检测具有可行性，在幅值1～20 V、频率范围1 kHz～20 MHz的激励下，在同一提离高度下对电缆沿线检测，可以检测长度在激励波长十分之一内电缆的开路和短路故障。为煤矿电缆故障井下检测以及产品研发提供了一种行之有效的方法。

关键词： 隐形矫治器   无托槽隐形矫治   磨牙远移   膜片厚度   边缘设计   切割线设计   边缘伸展   三维有限元分析   工程化口腔材料  

摘要： 背景：无托槽隐形矫治的优势之一是推磨牙远移，但在矫治过程中会出现牙齿倾斜移动、前牙支抗丧失等现象，是否可通过选择不同厚度与边缘的无托槽隐形矫治器来改善这些问题，以提高临床治疗效果，相关研究较少。目的：通过三维有限元分析不同厚度与边缘的无托槽隐形矫治器在推上颌第二磨牙远中移动时对中切牙、侧切牙和第二磨牙的控制能力。方法：利用Mimics、Geomagic Wrap、3-matic和SolidWorks软件分别建立不同厚度与边缘的上颌双侧第二磨牙远中移动的无托槽隐形矫治器-上颌牙列-牙周膜-牙槽骨的三维有限元分析模型，包括4种厚度(0.4,0.5,0.625,0.75 mm)和4种边缘(扇贝形、直线型、直线延长2 mm和直线延长4 mm)的组合，共16组。分别导入Ansys Workbench软件中设计并求解，分析第二磨牙牙周膜等效应力均值、峰值及分布情况，第二磨牙等效应力及最大初始位移，以及各组矫治器对第二磨牙、中切牙、侧切牙的控制能力。结果与结论：(1)16组模型中第二磨牙牙周膜等效应力均值、第二磨牙等效应力和第二磨牙最大初始位移都是随矫治器边缘的延长而增大，随矫治器厚度的增加而增大。(2)当矫治器厚度相同时，直线型矫治器组第二磨牙牙周膜等效应力峰值最大，直线延长型矫治器组第二磨牙牙周膜等效应力峰值大于扇贝形矫治器组；当矫治器边缘相同时，第二磨牙牙周膜等效应力峰值随矫治器厚度的增加而增大。直线延长型矫治器组第二磨牙牙周膜等效应力分布较扇贝形矫治器组、直线型矫治器组更均匀。(3)当矫治器厚度相同时，扇贝形矫治器对第二磨牙的控制最差；当矫治器边缘相同时，随矫治器厚度的增加，直线延长型矫治器对第二磨牙的控制逐渐强于直线型矫治器。直线延长2 mm矫治器对中切牙的控制较强且稳定，直线型矫治器对侧切牙的控制较强且稳定。(4)结果表明，使用无托槽隐形矫治器推磨牙远中移动时，延长矫治器边缘可增强对磨牙的控制，减少牙齿倾斜移动；对中切牙设计直线延长2 mm边缘、侧切牙设计直线型边缘，可增强对支抗切牙的控制，减少前牙唇倾。