超声辅助钛合金切削的表面残余应力数值仿真北大核心CSCD

针对钛合金加工后表面残余应力严重影响其使用性能的问题,采用Johnson-Cook失效准则,通过施加边界条件,以非线性有限元技术Abaqus/Explicit建立了钛合金TC4二维正交切削热力耦合切削仿真模型,分析了超声切削和普通切削在不同切削速度下钛合金的切削过程,获得了不同工况下的表面残余应力分布规律。结论表明:钛合金TC4已加工表面层的残余应力是拉应力,沿深度方向由拉应力逐渐过渡到压应力;在相同的切削参数下,超声切削后工件表面的残余拉应力较普通切削时小,最大残余压应力较普通切削时大,且最大残余压应力出现的位置相对较浅。     

表面滚压强化工艺的数值仿真

针对圆棒工件表面进行多圈连续进给滚压强化工艺,提出了Mare有限元的三维数值仿真模型.通过边界条件施加、滚动的实现、接触设置等有限元建模的建屯和修正,取得了与实际十分吻合的滚压成形的仿真结果;在分析残余应力形成过程的基础上,提出了改进的滚压过程模型;比较了不同进给量、网格划分及边界条件对残余应力分布的影响规律.结果表明,与以往的单圈或者不足一圈的滚压、滑动滚压,或者轧辊不转动的静止压入等简化条件下的仿真模型相比,仿真模型更接近实际的滚压过程,因而也获得了比较理想的变形和残余应力的仿真效果.     

ALGOR在温度计套管设计中的应用

本文主要介绍了有限元分析软件ALGOR在温度计套管应力分析和自振频率分析领域中的应用。并根据ALGOR分析结果,结合材料许用应力以及ASME PTC19.3等诸多因素论述了如何对温度计套管的强度进行具体核算。     

材料塑性应变对某钢制车轮残余应力测试的影响

针对车轮轮辋与轮辐组合焊缝附近结构的残余应力测试通常采用盲孔法,孔边由于应力集中易产生塑性变形的问题,采用有限元仿真与测试相结合的方法分析在钢制车轮加工的不同阶段,轮辋焊缝区残余应力测试时材料塑性变形对应变释放因数和残余应力测试结果的影响,并分析由Kirsch解析解确定的应变释放因数A和B计算车轮焊缝区残余应力测试所带来的误差.发现当孔边塑性变形较大时,用Kirsch解析解确定的应变释放因数计算残余应力会产生很大误差.     

射孔套管应力强度及影响因素仿真分析

压裂过程中,套管温降产生附加热应力,将改变套管受力状态,影响套管安全。应用Solid Works和Workbench软件,建立射孔段套管-水泥环-围岩三维导热有限元模型,井底温度从125℃降至60℃,考虑温度与热应力场耦合,分析射孔套管的热应力分布和强度安全性。研究表明,存在一个水泥环临界厚度,超过临界值,套管热应力增加明显,于套管强度安全不利;针对建立模型,水泥环弹性模量增加15.3%,其应力增加6.3%,套管应力减小2.9%,水泥环泊松比增加50%,其应力增加15.8%,套管应力增加5.9%;据上述算法,可确定任意套管-水泥环-围岩组合水泥环最优弹性模量范围。     

模压强化工艺及其数值仿真

对模压强化工艺过程进行有限元数值仿真过程中,利用普通的有限元模型无法真实地模拟压模对先模压端面凸起部分的挤压过程,从而无法真实地再现模压强化的过程,也就无法可靠地模拟强化后的残余应力、应变场,并且该部分节点由于与接触体脱离往往会造成计算收敛困难.文中基于对实际模压工艺过程的观察,利用相对运动原理,在后端面模压工序前加了一个上工作台压向压模和工件的工况,解决了这个问题,且有限元计算结果和实测数值一致.     

冲压成形残余效应对刚度分析的影响

针对冲压产生的板料厚度变化和残余应力等对有限元分析产生较大影响的问题,将冲压成形分析的网格节点厚度和塑性应变量等信息映射到车门总成刚度分析模型中,用MD Nastran分析车门刚度,并比较映射前、后车门刚度分析结果.结果表明在车门、内外板冲压成形残余效应影响下,车门总成刚度变化基本与料厚变化相吻合.     

火车车轮淬火过程数值模拟

为分析车轮淬火过程中的车轮各场量变化情况,利用MSC Marc商用有限元软件结合用户子程序开发对车轮淬火过程进行模拟计算. 通过模拟值和实测值的对比,模拟结果与实测结果吻合较好.     

轮腹式压力传感器的力学分析

本文对轮腹式压力传感器进行了三维有限元力学分析,找出了该传感器的位移及应力的变化规律.     

油田固井质量对套管损坏影响的数值仿真

在油田固井质量优化的研究中,由于地质条件和施工工艺等因素对固井水泥环的影响,套管外壁所受载荷的非均匀性增强,处于复杂的应力状态下,容易发生损坏现象.以N80套管为例,根据岩石力学和弹塑性力学理论,运用ABAQUS有限元分析软件建立地层-水泥环-套管机理研究的有限元模型,针对水泥环性能、居中情况、缺失情况等不同固井质量下,进行了仿真分析.研究结果表明,高强度、大刚度、无缺失、居中良好的固井水泥环是保护套管防止损坏的最佳固井质量.上述方法的研究成果为固井质量差导致套管失效提供了理论依据.     

Computation of eddy-current density on ESP motor and well casings under different operating conditions

This paper presents a 2D finite-element analysis of the induced eddy currents on motor and oil well casings of an electrical submersible pump (ESP) oil lifting system. Simulation results revealed that the increase in motor-casing conductivity and/or permeability decreases the eddy-current density on the well casing, contrary to that on the motor casing. Further increase in one or both of these parameters leads to a decrease in both current densities as a result of the skin effect phenomenon. However, the increase of well casing conductivity and/or permeability increases the eddy-current density on the well casing, while that on the motor casing remains unchanged. Increasing the fluid-mixture conductivity does not have any effect on the eddy-current density on the well casing, and for further increase in the fluid conductivity it decreases drastically, contrary to that on the motor casing which remains constant. The higher the current imbalance (including single phasing) and/or motor eccentricity, the higher is the maximum eddy-current density. Consequently, the increase of eddy-current density leads to an increase of the motor and well casings’ temperature, where the latter is known to accelerate the corrosion rate. It can be concluded that the design parameters and the construction of the motor and well casings play an important role in their corrosion.     

基于石油套管壁厚检测的多聚焦探头研究

为了实现对石油套管的全覆盖壁厚自动化检测,提出由阵列式多聚焦探头围绕石油套管旋转组成自动化壁厚检测系统。根据超声聚焦探头的测厚原理,分析聚焦探头的焦距和晶片尺寸与聚焦声束的关系,选择合适的聚焦探头组成阵列式多探头自动化壁厚检测系统,进一步研究探头与石油套管之间的最佳距离和阵列式多探头与扫描速度之间的关系。实验结果表明：自动化壁厚检测系统可以准确、可靠、快速地实现对石油套管的检测,检测系统满足实际生产的API标准。     

A new technique for producing large-area as-deposited zero-stressLPCVD polysilicon films: the MultiPoly process

Polysilicon films deposited by low-pressure chemical vapor deposition (LPCVD) exhibit tensile or compressive residual stresses, depending on the deposition temperature. Polysilicon films composed of alternating tensile and compressive layers can display any overall stress value between those of the individual layers, including a state of zero overall residual stress, depending on the relative thickness of each layer. The residual stress gradient can be similarly controlled by the layer thicknesses and distribution. This has been demonstrated with a ten-layer near-zero stress (<10 MPa), near-zero stress gradient (⩽0.2 MPa/μm) polysilicon film, containing flat cantilever beams whose length-thickness ratios exceed 150. Using multilayer deposition to control the stresses and stress gradients of polysilicon films is termed the MultiPoly process     

基于CAN总线的智能型井下压力传感器监测系统设计

套管阀是实施主过程欠平衡钻井的关键工具。结合胜利油田井下压力监测系统进行研究,设计并实现了一种基于CAN总线技术以超低功耗单片机MSP430为核心的具有温度补偿的智能型压力传感器监测系统,对井下的实时压力及温度信号进行实时采集,为井下套管阀开启提供保证。采用硬件补偿以及曲线拟合和牛顿插值法进行软件温度补偿,有效解决了由于温度变化对压力测量带来的影响;采用CAN总线及光电隔离等技术,抗干扰能力比较强,传输距离长,可达10km。通过实验证明,本系统实时性好,精度误差达0.75%,足以满足套管阀阀底压力监测系统研制要求。     

复合量程加速度计阳极键合残余应力研究

复合量程加速度计阳极键合过程中产生的残余热应力会引起加速度计的零位失调,也是导致加速度计失效的原因之一。对键合过程中产生的残余热应力进行了研究,仿真并分析了残余热应力与键合温度、玻璃基底厚度和框架键合宽度的影响,确定了适合复合量程加速度计的最佳键合宽度和玻璃基底厚度。     

金属波纹管焊接过程的应力及变形特性

针对焊接引起的变形及其所产生的残余应力和应变会影响金属波纹管正常使用的问题,用有限元法分析波纹管的焊接过程,研究焊接过程中金属波纹管的变形和应力.基于单元生死技术,考虑材料的性能随温度变化而非线性变化的影响,通过提取焊缝周边参考点和参考路径的应力和变形,重点研究热源移动对金属波纹管应力和变形分布、类型以及大小的影响.     

Characterization of Polycrystalline Silicon-Germanium Film Deposition for Modularly Integrated MEMS Applications

The deposition of in situ boron-doped polycrystalline silicon-germanium (poly-SiGe) films in a conventional low-pressure chemical-vapor deposition reactor has been characterized using the design of experiments method. The dependencies of deposition rate, resistivity, average residual stress, strain gradient, and wet etch rate in hydrogen peroxide solution are presented. Structural layer requirements for general microelectromechanical system applications can be met within the process temperature constraint imposed by complementary metal-oxide-semiconductor (CMOS) electronics. However, residual stress and strain gradient requirements for inertial sensor applications will be difficult to meet with a single homogeneous layer of poly-SiGe that is about 2 mum thick. By correlating stress depth profile measurements with cross-sectional transmission electron microscopy images, we conclude that the large strain gradient is due to highly compressive stress in the lower (initially deposited) region of the film. For films deposited at very low temperature (near the range of amorphous film deposition), in situ boron doping enhances film crystallinity and reduces the strain gradient     

大型塑料模具钢模块淬火工艺的有限元分析

采用有限元软件MSC Marc模拟大型P20钢模块在复杂淬火工艺下的冷却过程,通过分析淬火过程中的温度变化历程及最终组织分布,为厂方生产的P20钢模块制定合理的淬火工艺.     

A sticking model of suspended polysilicon microstructure includingresidual stress gradient and postrelease temperature

A sticking (stiction) model for a cantilevered beam is derived. This model includes the effect of the bending moment, which stems from stress gradient along the vertical direction of structural polysilicon, and the temperature during the release process. The bending moment due to the stress gradient will play an important role in evaluating antisticking efficiency since liquid tension and surface energy of microstructures tend to become smaller by newly developed antisticking techniques. The effects of stress gradient and temperature were analyzed and verified with surface-micromachined polysilicon cantilevers. By modifying the substrate polysilicon with grain-hole formation technique, the effects of residual stress gradient in polysilicon on stiction could be observed in the condition of low work of adhesion