C51嵌套汇编子程序在阻抗测试仪研制中的应用

C51嵌套汇编子程序，充分发挥了两种语言自的优势，介绍了C51调用汇编子程序的接品规则，并通过阻抗测试仪程序开发的例子予以详细说明。     

拉压异性纤维增强树脂基复合材料弹塑性问题的有限元分析

为了对复杂的非线性问题进行便捷求解,首先提出了考虑拉压异性的纤维增强树脂基复合材料统一非线性本构模型;然后,在此基础上进一步导出了本构模型的三维表现形式,以适用于非线性有限元分析工具的开发;随后,利用有限元软件ABAQUS提供的用户自定义子程序UMAT,自编了在二维和三维情况下的弹塑性应力分析程序;最后,应用程序对复合材料单向板和复合材料斜交板在偏轴拉伸/压缩下应力-应变曲线的预测与测试结果进行了比较,探讨了复合材料悬臂梁的弹塑性问题,并分析和比较了有无考虑拉压异性情况下应力分布和挠度响应的差异。结果表明:运用所提出的本构模型对考虑拉压不对称问题的弹塑性变形分析十分有效,这一本构模型有望成为实用数值分析工具,进而指导工程实践。     

Application of Gurson Model for Evaluation of Density‐Dependent Mechanical Behavior of Polyurethane Foam: Comparative Study on Explicit and Implicit Method

Recently, liquefied natural gas (LNG) is a focus of interest around the world for several reasons, and LNG cargo containment systems (CCS) increase in quality to prevent loss of LNG during shipping. For insulation of CCS, polyurethane foam (PUF), an outstanding insulation material, is commonly used. However, until now, although its mechanical properties are relatively good, the material is not considered as a structural member under compressive loading, principal load direction in CCS. Moreover, as PUF is a porous material by mixing and foaming, its mechanical properties depend on voids, which is a dominant parameter for density. Therefore, in the present study, nonlinear behavior of PUF is described using Gurson model with a novel technique, i.e., an acceleration factor. The model expresses the behavior through the volume fraction of voids with consideration of the density effect to evaluate structural performance using user‐defined material subroutine with explicit and implicit methods.

     

三角平衡轮廓轮胎滚动阻力的仿真研究

三角平衡轮廓轮胎是一种新型的轮胎结构,以低扁平率的传统轮廓轮胎255/30R22为基础,在其胎肩处和胎侧处增加高强度的支撑块来提高轮胎的性能。支撑块起到支撑胎面的作用,提高了胎侧的刚度。本文以滚动阻力计算公式和材料内耗机理为基础,用ABAQUS软件分别模拟2种轮胎的滚动阻力来验证三角平衡轮廓轮胎是否具有较低的滚动阻力。首先建立三角平衡轮廓轮胎和255/30R22轮胎的三维模型,施加相同载荷,对其进行以60km/h滚动工况的力学分析,算出单元积分点的生热率,提取每个单元的体积,最后计算每一种胶料的滚动阻力及轮胎总滚动阻力。通过两者的对比,三角平衡轮廓轮胎的滚动阻力仅18.7N,低于255/30R22轮胎滚动阻力的二分之一。     

冲击载荷下TC18钛合金力学性能模拟研究

TC18钛合金在退火状态下的屈服强度非常高,进行动态力学性能测试存在一定困难,可优先考虑采用数值模拟方法对其动态力学性能进行研究,而数值模拟结果的精确性主要取决于合金本构方程的精确性。为了减少数值模拟与实验结果之间的差异,在Johnson-Cook模型的基础上做了调整,利用ABAQUS软件的子程序接口自定义了材料本构子程序UMAT,以代码的形式来扩展ABAQUS程序的功能。通过与ABAQUS/Standard软件分析结果以及实验结果的对比,验证了自定义材料本构子程序UMAT计算结果的精确性与可靠性。该研究可为TC18钛合金的结构设计提供参考。     

板料成形过程有限元模拟中的接触处理

对板料成形过程进行有限元模拟时，为了取得可靠的计算结果，需要准确地描述模具与板料之间的动态接触状态．在全面分析成形中板料与模具接触边界动态变化的基础上，结合ABAQUS有限元分析软件给出了模型的几何描述、接触算法选择及应用VFRIC用户子程序进行接触摩擦模型的建立等具体方法．通过具体实例，证明了这些方法应用于板料成形过程的接触分析的可行性．     

Modeling strategies for unsteady turbulent flows in the lower plenum of the VHTR

Validation simulations are presented for turbulent flow in a staggered tube bank, geometry similar to the lower plenum of a gas-cooled high temperature reactor. Steady 2D RANS results are compared to unsteady 2D RANS results and experiment. The unsteady calculations account for the fact that nonturbulent fluctuations (due to vortex-shedding) are present in the flow. The unsteady computations are shown to predict the mean variables and the total shear stress quite well. Previous workers’ results indicate that 3D simulations are needed to obtain reasonable agreement; present results indicate 2D is sufficient. Best practices are based on requirements for the ASME Journal of Fluids Engineering.     

Three‐dimensional Structural Analysis Approach for Aging Composite Solid Propellant Grains

The viscoelastic aging behavior of composite solid propellant grains is studied by a three‐dimensional thermoviscoelastic constitutive model with aging evolution, in which the crosslinking degree is taken as an aging variable. The resulting viscoelastic constitutive equations are numerically discretized into incremental form by integration algorithms, and the stress‐updating method is presented according to incremental law. Subsequently, the Abaqus‐based user material subroutine and its structural analysis module are constructed and validated through typical examples. Studies show that the results of structural analysis have high accuracy and are in well agreement with each other. The designed analysis module presents an effective aging‐mechanical analysis platform for further lifespan estimation of solid rocket motors.     

基于单片机液晶显示模块的接口设计

介绍了GJ12864点阵式液晶显示模块和单片机MSP430F149的功能特点及两者之间的接口设计.通过适当的电路设计解决了电平不兼容的问题.详细阐述了硬件电路的设计和图形、字符及汉字属性显示方式的软件设计思想,给出了硬件接口电路图和显示程序流程图.该设计具有硬件电路设计简单可靠,程序编写简单实用的优点.成功完成了LCD显示驱动及系统控制的双重任务,实现了良好的人机对话,实践中取得良好的效果,并已成功应用于γ-个人辐射剂量仪中.     

结合改进单胞模型的单钉双剪层合板螺栓连接结构挤压性能的多尺度表征分析

为提高螺栓连接层合板结构的可靠性和承载能力,基于ABAQUS软件及用户子程序(USDFLD),结合改进的单胞模型,建立了考虑组分材料失效的多尺度数值模型。利用该模型表征分析了单钉双剪层合板螺栓连接结构的力学性能,研究了铺层形式及几何尺寸对连接结构性能的影响。该模型的预报结果与试验结果吻合较好。结果表明:准各向同性层合板螺栓连接结构的挤压强度高于正交各向异性层合板连接结构的挤压强度,前者的失效模式为挤压失效,后者为剪出失效,该模式导致结构承载能力降低,设计中应避免。层合板边径比大于3时,不同宽径比连接结构的挤压强度趋近稳定值;但相同边径比的连接结构,其挤压强度随宽径比的增大而增大,连接结构设计时应给予考虑。