深海扬矿泵内固液两相流动模型研究

为选用合理的固液两相流动模型用于深海扬矿泵内矿物浆体的计算。针对深海海底矿物具有颗粒粒级跨度大且粒径大的特点,本文分别选用粗颗粒-均质浆体计算模型和固液两相混合物浆体计算模型,开展扬矿泵数值模拟分析。研究发现,粗颗粒-均质浆体计算模型计算得到的内部流场与固液两相混合物浆体计算模型得到的内部流场是相似的,所以该模型可以用来分析扬矿泵的内部流场;该模型减少了颗粒追踪数量可以节约计算时间;将两种计算方法得到的扬矿泵外特性与试验结果进行比较,发现该模型计算得到的泵扬程与功率均更接近试验结果,说明该模型在扬矿泵性能计算是有优势的。     

固液两相流泵装置汽蚀余量计算

从液相的能量出发,推导了固液两相流泵装置汽蚀余量方程。利用具体计算实例,分析了固相对泵装置汽蚀余量的影响。结果表明,固相密度、体积浓度对泵装置汽蚀余量影响较大。固相颗粒直径的影响相对小些。     

定常固液两相流动边界层的数学模型

利用两相流动理论和边界层理论，分析了固液两相流动中的受力情况，以及边界层中的流动特征，对二维粘性定常不可压流体边界层中的层流运动进行了讨论，推导出了边界层的数学模型，为进一步全面研究固液两相流动流场奠定了基础。     

液固两相流量计的可行性

本文介绍了相关法的测量原理及其实现的可能性;同时,对国外在此方面的概况和发展趋势作了介绍。     

基于相位场模型的稀疏液固两相流场特性分析方法

针对在模具结构化表面精密加工过程中稀疏液固两相流场特性参数难以求解的问题,提出了一种基于相位场模型的稀疏液固两相流场特性分析方法。相位场模型中速度场和压力通过Navier-Stokes方程控制,两相流的分界面动力学方程由Cahn-Hilliard方程控制,从而建立了面向软性磨粒两相流流型分析的动力学模型;采用传统的二阶中心差分格式逼近粘性项和表面张力项,同时采用五阶WENO格式近似的对不可压缩两相流进行了空间离散化重构,并采用TVD Runge-Kutta方法提高了求解过程中时间的离散精度;以加工常用的长方形直流道为具体仿真实验对象,研究了稀疏液固两相流流经不同尺寸流道过程中的速度场与压力场变化。研究结果表明,两相流数值仿真结果与理论分析相符,且与国外仿真结果相吻合,从而验证了该方法的有效性,为软性磨粒流精密加工方面的研究提供了可靠的理论依据。     

液固两相流中固体的测量

讨论了液固两相流中固体量的计算问题与方法，并讨论了实用的检测仪表选用的问题，简介了部分应用实例。     

基于固相效应系数的离心式固液两相流泵浆体扬程计算方法研究

在计及固相颗粒当时角速度的基础上,导出了固相效应系数公式,继而得出了全新的浆体扬程计算公式。通过与某些文献给出的方法进行对比计算发现,利用该浆体扬程计算公式计算得到的结果不仅误差小,而且误差的分散性也很小。     

无堵塞离心泵内部三维固液两相湍流场数值模拟

针对无堵塞泵叶轮内部流场的特点,选用颗粒拟流体的κ-ε-Α_p模型模拟两相湍流,基于SIMPLEC算法建立压力修正方程来满足连续性方程和动量方程间的耦合关系,并由此建立了两相湍流的时均控制方程组,采用GEM-CHIP算法编制程序对叶轮内流进行模拟,并实现了模拟结果的可视化。模拟结果揭示了无堵塞泵叶轮内部流动的某些特征:叶轮前盖板一吸力面处存在射流—尾迹区,流体相与颗粒相之间有速度滑移,且滑移值随流道逐渐降低。     

固液两相环形隔膜泵优化设计浅析

鉴于现有的环形隔膜泵只能输送一般液体和黏稠性介质,难以输送固液两相的介质的现状。通过结构的改进与优化,设计了一种适用输送固液两相介质的环形隔膜泵。     

微通道中液氮的流动沸腾——两相流动压降分析

对液氮在直径为0.531 mm,加热长度为250mm的圆管中的流动沸腾压降和传热特性进行研究.作为第一部分,主要对微通道中液氮的两相流动压降进行试验研究与分析.结果表明:在核态沸腾起始时,质量流量迅速降低,而压降突然增大,并伴随着明显的温度滞后,幅度约为4.0～5.0 K.由于压降很大,在微通道内液氮的两相流动中会出现闪蒸,从而对质量干度产生重要影响.最后,利用均相模型和三个两相流动模型(L-M模型,Chisholm B系数模型和Friedel模型)对微通道沿程压降进行分析和比较.不同于常规通道的是,均相模型可以很好地预测压降试验结果,而三个两相流动模型的预测偏差较大,这是由于在微小通道中的高速流动情况下,汽相和液相混合比较均匀;同时液氮的液汽密度比很小,这也有利于均相模型的预测.     

进口节流式滑阀内流场的有限元计算与PIV研究

用有限元法(FEM)和粒子图像测速技术(PIV)对三种不同开口度下进口节流滑阀沿进口流道、节流口、阀腔以及出口流道的流场进行了数值计算和试验可视化研究。数值模拟的数学模型采用的是连续性方程和Navier-Stokes方程的流函数—涡量式,有限元法用于方程的离散。自行编制的有限元计算程序用来计算求解区域离散点上的流函数及涡量值,再根据流函数及涡量与速度分量之间的关系求出各结点上的速度矢量。对于粒子图像测速试验,光源采用双脉冲Nd:YAG激光器,再用柱透镜和球面镜调制得到1.0mm片光照射流场。30～50μm的聚苯乙烯小球用做示踪粒子,Kodak ES1.0 CCD照相机拍摄流场图像,所得图像用FFT相关算法进行处理,结果用Tecplot输出,数值计算和PIV试验表明,滑阀内部有三个部位产生涡旋。数值计算又表明滑阀开度对阀内部流场结构有影响。研究对于定性分析阀内能量损失、噪声以及对阀的结构和流道的设计有重要实际意义。     

铸件成形过程非稳定温度场的有限元模型

以Galerkin法建立非稳定导热问题的有限元方程。通过对守恒条件的讨论,确立了以单元边长为权因子的铸件成形过程非稳定温度场的守恒有限元模型。为了在模型中较准确地计入铸件凝固过程中特有的潜热释放现象,应用差热分析的原理实测了低碳钢的凝固潜热曲线,并建立与此相适应的潜热处理局部迭代法。因此,该模型具有可靠、简便、计算速度快和精度较高等特点。     

FINITE ELEMENT MODELING OF BURR FORMATION IN ORTHOGONAL CUTTING

A finite element model for orthogonal cutting is developed and applied to simulate burr formation. Three typical workpiece materials were investigated. The simulation results reveal the entire burr formation process. The simulation produces either positive or negative burrs depending on the material properties, which is in agreement with experimental observations from literature. Both shear and normal stress failures are presented for negative burr formation while only shear stress failure leads to positive burr formation. The FE modeling results confirm that material property is the dominant factor in controlling burr formation.     

一种轧机动力分析有限元模型

提出一种四辊轧机动态性能分析的平面有限元模型,该模型由梁单元、杆单元、刚度单元和质量单元等组成。根据该理论,可计算得到轧机容易激发的固有频率。用试验检验了所提模型的正确性。     

约束层阻尼板的有限元建模研究

粘弹性材料（VEM）的本构关系随频率和温度的变化而变化，对粘弹结构难以进行动特性分析及控制研究。基于Hamilton原理，给出了一种建立约束层阻尼（CLD）板动力学方程的新建模方法，建模时，考虑到VEM的纵向位移影响，并引入虚拟自由度，导出了标准二阶定常线性系统模型，从而避免因粘弹性材料导致的高阶非线性方程。采用GHM方法描述VEM的本构关系，它能直接与有限元法融合。算例分析了夹芯层为ZN—1型粘弹性材料的CLD悬臂板的动态特性，并与相关文献中的计算及试验结果进行比较，计算结果更加准确，表明新建模方法是准确的。     

MACHINING STUDIES OF UD-FRP COMPOSITES PART 2: FINITE ELEMENT ANALYSIS

A number of parameters and an exhaustive material development and experimental procedure to determine the response variables like cutting forces, surface damage restricts the expensive experimental research. In this context, Finite Element Method (FEM) analysis can be used as a tool for the prediction of the various machining responses. A finite element analysis of the orthogonal machining of Uni-directional Glass Fiber Reinforced Plastic (UD-GFRP) laminates is presented in this study to understand the complex relation between fiber orientation, tool geometry, depth of cut on cutting forces and sub-surface damage.     

UNDERSTANDING OF FINITE ELEMENT ANALYSIS RESULTS UNDER THE FRAMEWORK OF OXLEY'S MACHINING MODEL

We introduce an accurate coupled thermo-mechanical finite element analysis (FEA) of machining using the Arbitrary Lagrangian Eulerian (ALE) analysis capability of ABAQUS/Explicit. This analysis provides detailed information about the cutting forces, chip thickness, contact length, the extent of the primary and secondary shear zones as well as the distribution of strain, strain rate and temperature in the deformation zones. This information has to be viewed under the framework of an analytical model for it to lead to better understanding of the physics of machining. We use the best available analytical model, namely, Oxley's machining model, for this purpose and the FEA results are compared with the assumptions and predictions of Oxley's analysis. The strain rate in the primary shear zone, the hydrostatic pressure variation along the shear plane, the distribution of normal and shear stresses along the tool-chip interface and the shape of the secondary shear zone are the quantities compared. Due to the key role of temperature in the prediction of tool wear, the fraction of heat conducted away into the workpiece, the maximum temperature along the tool-chip interface and the maximum temperature along the flank face are also compared. The comparison reveals that Oxley's model captures the physics of machining quite well. However, some details such as the heat partition module and the assumptions on stress and temperature distribution at the tool-chip interface need to be revisited.     

UNDERSTANDING OF FINITE ELEMENT ANALYSIS RESULTS UNDER THE FRAMEWORK OF OXLEY'S MACHINING MODEL

ABSTRACT

We introduce an accurate coupled thermo-mechanical finite element analysis (FEA) of machining using the Arbitrary Lagrangian Eulerian (ALE) analysis capability of ABAQUS/Explicit. This analysis provides detailed information about the cutting forces, chip thickness, contact length, the extent of the primary and secondary shear zones as well as the distribution of strain, strain rate and temperature in the deformation zones. This information has to be viewed under the framework of an analytical model for it to lead to better understanding of the physics of machining. We use the best available analytical model, namely, Oxley's machining model, for this purpose and the FEA results are compared with the assumptions and predictions of Oxley's analysis. The strain rate in the primary shear zone, the hydrostatic pressure variation along the shear plane, the distribution of normal and shear stresses along the tool-chip interface and the shape of the secondary shear zone are the quantities compared. Due to the key role of temperature in the prediction of tool wear, the fraction of heat conducted away into the workpiece, the maximum temperature along the tool-chip interface and the maximum temperature along the flank face are also compared. The comparison reveals that Oxley's model captures the physics of machining quite well. However, some details such as the heat partition module and the assumptions on stress and temperature distribution at the tool-chip interface need to be revisited.     

基于试验的组合强化模型在弹塑性有限元中的应用

对ＬＹ１２ＣＺ铝合金材料的组合强化性能进行测试。提出了一种基于试验的组合强化模,编制了应用试验组合强化模型的弹塑性有限元程序,并对冷胀孔边的残余应力分布进行了计算。本文的试验组合强化模型在弹塑性有限元分析中的应用,对计算工程中的弹塑性问题有着实际的