ANSYS二次开发在火炮身管温度场计算中的应用

为了简化ANSYS中火炮身管温度场的计算过程,利用APDL语言编写了火炮身管温度场计算的命令流文件。应用APDL命令实现了有限元模型建立、网格划分、载荷施加、求解计算等步骤的自动完成。在计算时只需用户输入参数,即可完成不同口径火炮身管温度场的计算。     

扫描电子束表面改性过程温度场的有限元分析

根据热传导理论和扫描电子束焊机的实际工作状态,模拟了扫描电子束表面改性过程的温度分布。采用六面体划分网格和四面体划分网格两种模式,来模拟改性过程的温度变化,并比较了两种模式下的温度分布。结果表明:六面体划分网格和四面体划分网格两种模式下的温度分布基本相似,而采用六面体划分网格的模型的计算效率较高。     

点接触弹流润滑问题的高效直接算法

在复合直接迭代法的基础上,运用分块迭代的思想将方程组降维,通过研究弹性变形影响因子对弹性变形的影响,将压力迭代矩阵由满元阵变为稀疏的带状阵,提出一种新的求解点接触弹流问题的高效直接迭代算法.与复合直接迭代法相比,该算法大大减少了计算量,计算效率至少提高20倍,并且可适用重载工况.将新算法计算结果与Hamrock-Dowson公式计算结果进行比较,并讨论迭代矩阵半带宽与收敛速度、载荷范围、计算精度以及数值稳定性的关系.结果表明,当压力迭代矩阵密度为满阵的22％～25％时,新算法具有最高的计算精度.     

局部多孔质气体静压圆盘止推轴承压力分布的有限元计算

直接在Cartesian Coordinates中对气体静压圆盘止推轴承的Reynolds气体润滑方程进行有限元计算,针对局部多孔质直径大小的不同,采用两种不同的网格划分方法,并通过Matlab编程实现了网格的自动细分,在此基础上,通过利用Galerkin加权残差原理对气膜内压力分布进行了求解.分析表明,网格的自动细分减少了网格划分的时间,便于获得合适的网格数量,使轴承压力分布的计算得到进一步简化.     

温度场计算中差分法的应用

在温度场计算中,对变步距划分网格的差分法进行了分析,通过使用等步距和变步距划分网格的方法进行对比计算,得出了变步距划分网格的方法。该法既减轻了计算工作量又可获得较好的计算精度,在生产实践中具有较高的实用价值。     

基于FLUENT动网格的动压轴承特性改进算法

针对基于FLUENT软件计算滑动轴承存在需要调整偏位角而多次划分网格,导致计算效率低的问题,提出了一种改进算法,通过采用C++和动网格技术并编写UDF程序,实现了轴承静平衡位置偏位角的自动迭代。采用提出的计算方法对轴承油膜压力分布及静特性参数求解,并与理论数值计算结果进行对比,验证了计算模型的正确性,提高了计算效率。     

一种快速求解点接触弹流问题的直接迭代算法

在复合直接迭代法基础上,通过将整个二维求解区域化为若干部分、降低方程组维数、分条求解,提出一种新的求解点接触弹流润滑问题的直接迭代算法。该算法保留了复合直接迭代法所有优点,但计算效率提高了10倍以上,同时具有更宽的载荷适用范围。     

三维真实粗糙表面弹性接触的全域数值解

本文提出了三维真实粗糙表面弹性接触问题的全域数值求解方法。这种方法采用网格规则划分和局部柔度矩阵存储解决了计算机存储问题;采用求解域收缩和逐次低松弛迭代解决了接触方程求解问题。运用这种方法可以获得真实粗糙表面弹性接触时全接触域内的压力分布与总载荷、接触图象及其实接触面积、接触变形与接触刚度等参数。计算结果与实测结果符合得较好。     

内燃机活塞温度场分析

建立了二分之一活塞模型,应用HyperMesh软件对模型进行了网格划分,计算了活塞的温度场,为活塞的结构改进和优化提供了理论依据。     

汽车通风盘式制动器的流固热多物理场耦合建模与分析

基于两相耦合的通风盘式制动器热力学研究方法与实际边界条件存在一定偏差。为提升制动器温度场和应力场的计算精度,综合运用紧耦合和松耦合算法,通过MPCCI数据交换平台实现ABAQUS(固体模型)与FLUENT(流体模型)求解器的同步迭代及耦合参数的实时共享,即温度场、应力场和空气流场的完全耦合运算,采用Link3900 NVH台架试验校验温度场计算结果。流体模型动区域采用滑移网格技术处理,湍流模型选择RNG k-ε模型,边界层内的求解选用非平衡壁面函数法,确保第一层网格节点的y+值在30～60。根据通风盘端面和肋片结构设置不同方向的节点路径,得出耦合面温度、应力以及对流换热系数沿不同方向的变化规律。结果表明,对应节点的瞬态温度计算值与试验值表现出良好的匹配性,平均偏差低于4%。该研究方案可有效地保证整体模型的计算精度和效率,为通风盘式制动器的优化设计提供重要的依据。     

A method for obtaining the temperature distribution at the interface of sliding bodies

The friction-induced temperature rise at the interface of two sliding bodies can cause a number of effects, including yield strength reduction, accelerated oxidation wear and thermoelastic instability, all of which may lead to degradation of performance or even the failure of the associated components. It is of interest, therefore, to accurately determine the temperature field resulting from sliding contact. In this study, the authors present a method for obtaining the temperature rise at the interface of two sliding semi-infinite bodies by partitioning the heat between them in such a way that the temperature at every grid point in the interface is same for both the bodies. A polynomial form is assumed for the unknown heat partition function and then a linear regression is performed to find the coefficients that optimize the temperature matching at the interface. The results of the analysis, when compared to the predictions of Blok and Jaeger, who each calculated a constant heat partition factor based on a single temperature match, indicate that their more simple analyses provide good estimates of either the maximum temperature rise (Blok) or the average temperature rise (Jaeger). The method of the current study, which yields the complete temperature and heat partition distributions within the interface, may be used in conducting a detailed thermal analysis of sliding bodies.     

不同有限元建模方法对工程机械举升系统强度分析影响研究

工程机械的举升系统是其最主要的部件,其中有较多的转动连接部分,用有限元法计算其强度时,不同的建模方法对其强度仿真结果的准确性有较大影响。以某型号叉车的举升系统为研究对象,在相同工况下,对举升系统的主要部件和转动连接部位分别采用实体网格单元与梁单元约束、实体网格单元与耦合单元约束、壳单元与梁单元约束三种方案建立有限元模型。通过Ansys软件进行强度仿真分析,得到不同的强度计算结果,并与第四强度理论理论计算值进行比较。结果表明,在同一个工况下,采用四节点实体网格单元与耦合单元约束建立的有限元模型更加贴近实际工况,相对误差较小,提高了实际仿真工作的效率。     

Simple technique for high‐throughput marking of distinguishable micro‐areas for microscopy

Today's (nano)‐functional materials, usually exhibiting complex physical properties require local investigation with different microscopy techniques covering different physical aspects such as dipolar and magnetic structure. However, often these must be employed on the very same sample position to be able to truly correlate those different information and corresponding properties. This can be very challenging if not impossible especially when samples lack prominent features for orientation. Here, we present a simple but effective method to mark hundreds of approximately 15×15 μm sample areas at one time by using a commercial transmission electron microscopy grid as shadow mask in combination with thin‐film deposition. Areas can be easily distinguished when using a reference or finder grid structure as shadow mask. We show that the method is suitable to combine many techniques such as light microscopy, scanning probe microscopy and scanning electron microscopy. Furthermore, we find that best results are achieved when depositing aluminium on a flat sample surface using electron‐beam evaporation which ensures good line‐of‐sight deposition. This inexpensive high‐throughput method has several advantageous over other marking techniques such as focused ion‐beam processing especially when batch processing or marking of many areas is required. Nevertheless, the technique could be particularly valuable, when used in junction with, for example focused ion‐beam sectioning to obtain a thin lamellar of a particular pre‐selected area.     

基于SYSWELD软件的TC4电子束焊接过程的数值模拟

基于有限元软件SYSWELD对14mm厚TC4钛合金平板电子束焊接过程进行三维实时动态模拟的研究。通过对温度场、应力场以及变形的模拟计算，并结合相应的试验验证，提出了一种焊接过程数值模拟的分析方法，这种方法为掌握实际电子束焊接过程中温度和应力的变化规律提供了方便，也更有助于优化结构设计，指导焊接工艺。     

SiC_p/101Al复合材料电子束焊接接头温度场对其显微组织的影响

采用ANSYS有限元分析软件对SiCp/101Al复合材料电子束焊接时接头的温度场进行了数值模拟,在此基础上对接头显微组织中Al4C3脆性相生成数量进行了分析.结果表明:采用双椭球热源模型可准确地模拟出电子束焊接接头的温度场;焊接时表面熔池近似为圆形,内部呈上宽下窄的锥形;在保证接头焊透的前提下,适当提高焊接速度或减小电子束输入功率,可在一定程度上减少接头组织中Al4C3脆性相的数量.     

基于蒙特卡罗模拟的快速剂量计算方法研究

本文应用蒙特卡罗算法建立了一个光子虚拟源模型，用于模拟计算任意形状和强度的外照射放射治疗的射束分布。建立的源模型包含一个由方形网格元素组成的光子通量矩阵，定位于距离加速器靶下方20cm处。通过使用蒙特卡罗模拟代码包BEAMnre，模拟粒子加速器治疗头各部件中的传输过程，获得源模型所在平面的光子通量和能谱分布，并进行重构，以反映物理射束经过加速器射束成形部件后所引起的形状改变。通过比较6MV光子柬3个标准方野的深度剂量和离轴比分布的计算结果和测量结果，取得了较好的吻合。通过对不规则野剂量分布的计算和测量结果的等剂量线进行比较，在90％和50％等剂量区吻合较好，在10％低剂量区稍有差异。本文提出的光子虚拟源模型能够较为精确地模拟计算任意形状和强度的外照射放射治疗射束分布。     

焊接烟尘流体流动规律数值模拟

用gambit建立了不同的车间模型网格，然后利用流体计算软件Fluent模拟研究了封闭式焊接车间在具有不同送风口、排风口位置时的温度场、速度场。结果显示有两种模型比较满足要求。在这两种模型基础上进行改动，模拟比较改动后模型的温度场、速度场，研究得到混合通风和置换通风两者结合的通风方案对焊接车间烟尘的排放效果更好。     

Measurement and estimation of temperature rise in TEM sample during ion milling

The actual temperature rise was measured during ion-milling process used in the transmission electron microscopy (TEM) sample preparation. Special probes were fabricated for the measurements, one with shielded, floating thermocouple mounted onto a 3mm grid to compute the thermal load at the sample, and the other, a bare probe with a polymer coating to measure the maximum temperature attained. The temperature measured in the most commonly used ion-milling system reached up to 295 degrees C when the typical milling conditions, 6keV ion-energy and an incident angle of 80 degrees, were used. Based on the temperature profiles that were obtained by the shielded probe, two unknown parameters, the amount of heat deposited by the energetic ions/neutrals to the sample and the thermal conductivities between the materials, were estimated and used to compute the temperature rise in commonly adopted materials. The calculation showed that the temperature of the glass sample reached more than 300 degrees C under typical ion-milling conditions. The calculated value was confirmed with the experimental result of the crystallization of an amorphous Si on the glass under the typical ion-milling condition, which gave the same extent as annealing at 350 degrees C.     

Numerical calculation and experimental research on crack arrest by detour effect and joule heating of high pulsed current in remanufacturing

The remanufacturing blanks with cracks were considered as irreparable. With utilization of detour effect and Joule heating of pulsed current, a technique to arrest the crack in martensitic stainless steel FV520B is developed. According to finite element theory, the finite element（FE） model of the cracked rectangular specimen is established firstly. Then, based on electro-thermo-structure coupled theory, the distributions of current density, temperature field, and stress field are calculated for the instant of energizing. Furthermore, the simulation results are verified by some corresponding experiments performed on high pulsed current discharge device of type HCPD-I. Morphology and microstructure around the crack tip before and after electro pulsing treatment are observed by optical microscope（OM） and scanning electron microscope（SEM）, and then the diameters of fusion zone and heat affected zone（HAZ） are measured in order to contrast with numerical calculation results. Element distribution, nano-indentation hardness and residual stress in the vicinity of the crack tip are surveyed by energy dispersive spectrometer（EDS）, scanning probe microscopy（SPM） and X-ray stress gauge, respectively. The results show that the obvious partition and refined grain around the crack tip can be observed due to the violent temperature change. The contents of carbon and oxygen in fusion zone and HAZ are higher than those in matrix, and however the hardness around the crack tip decreases. Large residual compressive stress is induced in the vicinity of the crack tip and it has the same order of magnitude for measured results and numerical calculation results that is 100 MPa. The relational curves between discharge energies and diameters of the fusion zone and HAZ are obtained by experiments. The difference of diameter of fusion zone between measured and calculated results is less than 18.3%. Numerical calculation is very useful to define the experimental parameters. An effective method to prevent further extensi     

基于矩阵摄动的谱聚类算法确定电网最优分区数的研究

针对电压控制的电网分区数量难以确定和分区易发生改变的问题,提出了一种基于矩阵摄动的谱聚类方法。该方法在谱聚类算法上,通过电气距离构造网络的Lapiacian矩阵,利用其特征根变化量确定分区数量,最后使用K-means聚类算法对电网进行分区。在IEEE14节点的仿真系统下,该方法与原有分区的分区数和分区结果相同。在IEEE39节点的测试系统下,该方法的空间电气距离和节点联系紧密度具有一定的鲁棒性;通过蒙特卡洛随机模拟,在扰动较小的情况下,该方法的分区数保持不变,而在较大扰动下,分区数可能会发生改变,但变化的概率很小。