Simulation of ultrasonic-vibration drawing using the finite element method (FEM)

In ultrasonic-vibration drawing, wires are drawn while ultrasonic vibration is applied to a drawing die. Prior studies provide experimental proof that ultrasonic-vibration drawing reduces drawing resistance, improves lubrication and prevents wire breakage. In the future, ultrasonic-vibration drawing is expected to contribute to the drawing of difficult-to-draw materials and operations, such as shaped wires, ultrafine wires, and the wire drawing operation in semidry or dry condition. However, a detailed analysis and understanding of the mechanism of improvement is not possible on the basis of conventional experimental observations because the ultrasonic-vibration processing phenomenon occurs at high speed. Therefore, we attempted to understand the processing mechanism of ultrasonic-vibration drawing using the finite element method (FEM). ABAQUS was used for the FEM. Drawing force and stress–strain distributions in drawn wires were analyzed. From these studies, we quantitatively clarified the mechanism of improved drawing characteristics, such as decreased drawing force.     

石人水库边坡开挖卸荷有限元模拟分析

水利水电工程建设是我国新能源战略的重要组成,在水利工程建设中经常会遇到岩体开挖后边坡失稳现象。岩体开挖是一种物理卸荷作用,研究卸荷理论和其数值计算方法对水利工程设计意义重大。基于国内外研究进展,首先利用Mohr-Coulomb强度准则对岩体卸荷强度参数进行分析。随后利用ANSYS软件建立了边坡开挖有限元模型,并计算了边坡开挖卸荷过程中的应力分布和塑性区分布。最后对边坡位移和描杆轴力进行分析,对比了考虑卸荷效应和未考虑卸荷效应的区别。     

琼中抽水蓄能电站高压引水系统布置与设计

琼中抽水蓄能电站采用一洞三机的布置形式,岔管段最小覆盖层厚度与最小主应力条件满足规范要求,且运行期衬砌结构整体裂缝宽度处于可控范围内,检修期间,在外水压力作用下结构出现整体受压破坏的可能性较小,具备采用钢筋混凝土衬砌的条件。另外通过对不同钢岔管方案的比较,认为钢板衬砌需要的高强钢材用量较大,考虑到直接投资和工期方面的明显优势,最终推荐采用衬砌厚度为1.0 m的钢筋混凝土衬砌方案。     

斜拉桥肋板式主梁剪力滞效应研究

大跨度斜拉桥剪力滞效应十分突出,在设计和施工过程中应考虑剪力滞效应的影响。根据能量变分原理,推导出肋板式主梁截面的剪力滞系数简易计算公式。以某460米主跨预应力混凝土斜拉桥为研究对象,采用大型空间有限元分析程序MIDAS FEA 3.3进行三维实体有限元数值分析,并与通过能量变分法计算得到的剪力滞系数比较发现,宽度较大的肋板式主梁剪力滞效应突出,且跨中处截面剪力滞系数小,而塔根处的截面剪力滞系数大,在设计和施工过程中应采取必要的措施保证结构安全。     

某泵站前池三维有限元分析

结合某泵站的工程实例,采用三维有限元分析软件对泵站前池建立三维实体模型,分析了设计工况下结构应力,为工程设计提供了依据,对类似工程具有一定的借鉴意义。     

工业厂房加层改造施工过程的模拟分析

房屋在加层改造过程中具有显著的结构时变特性。为保障某工业厂房室内加层改造施工的安全顺利进行,基于实际情况制定了合理的施工顺序,以结构拆除时间为分界点将施工过程进行划分,用有限元分析软件MIDAS的生死单元技术对结构进行施工模拟,得出了施工过程中结构内力变化规律和施工危险点,并提出相应的安全控制措施。     

埋地管道开挖边坡有限元法优化设计

在埋地管道输水方案中,沟槽开挖坡比的大小直接影响施工安全、管材安装质量及工程投资与经济效益,因此,合理设计开挖坡比具有重大意义。以阜城—景县输水管道工程为工程背景,根据给定工程地质,基于有限元强度折减法,以ANSYS软件为计算工具,对沟槽开挖边坡进行安全稳定性计算。通过计算假定开挖坡比的边坡稳定性,获得不同开挖坡比下的沟槽边坡达到破坏时的安全系数,再根据选取的最优安全系数,确定最优开挖边坡。同时,基于上述方法,计算分析了开挖坡比与边坡安全系数的非线性关系,根据计算结果得出了有益结论与意见。     

五元系数法-改进熵权法在水质评价中的应用

为了使水质监测值和水体划类标准值之间关系更紧密,利用五元联系数方法建立了各水质评价指标与评价标准的五元联系数;同时在传统熵权计算的基础上,采用秩比法设定偏好校正系数,得到改进的熵权重;最后将五元联系数ui和改进的熵权重WRi相结合获得五元综合联系度,据此对水质进行评价,这是一种主客观结合的、符合实际情况的水质评价新方法。以贵州贵阳市河流断面监测数据为例,评定样本点所在河段水质等级,分析了该河流水质变化趋势,验证了五元系数法-改进熵权法水质评价方法的实用性。     

Development of a noise prediction software NASEFA and its application in medium-to-high frequency ranges

For the analysis of noise problems in medium-to-high frequency ranges, the energy flow boundary element method (EFBEM) has been studied. EFBEM is numerical analysis method of energy flow analysis (EFA), and solves energy governing equations using a boundary element method in complex structures. Based on EFBEM, a noise prediction software, “noise analysis system by energy flow analysis” (NASEFA), was developed. For effective maintenance, NASEFA is composed of three main modules: the translator, the model converter, and the main solver. The translator changes the FE model to the NASEFA BE model, and the model converter changes the BE model to an EFBE model, including various data, such as structural materials, medium properties, sources, and boundary conditions. NASEFA then solves the acoustic energy density and intensity on boundary and in the field. Moreover, it analyzes interior and exterior noise problems for single and multiple domains in two and three dimensions. Finally, for the validation of the software developed, interior and exterior noise predictions of various structures were performed. The results obtained with NASEFA were compared with those of the commercial SEA program and experiment. From these comparative studies, the usefulness of NASEFA was established.