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关键词： 等径角挤压   循环载荷   晶体塑性   应力三轴度   晶界  

摘要： 应力三轴度是决定金属损伤演化的关键因素。为了了解应力三轴度在细晶组织中的分布情况,通过电子背散射衍射法(EBSD)获得8道次等径角挤压(ECAP)纯铜的微观组织信息;并基于晶体塑性有限元法建立代表性的体积单元,探讨8道次ECAP纯铜在循环载荷下应力三轴度的分布现象与规律。结果表明:在循环加载初期应力三轴度的分布是不均匀的,循环加载20圈后,分布不均匀程度增大;极大和极小的应力三轴度多分布在晶界处,通常是软取向、硬取向晶粒相邻的情况。

关键词： 威荣区块   页岩气   多级压裂   地应力变化   套管变形  

摘要： 近年来,页岩气水平井多级压裂过程中的套管变形问题日渐突出,导致后续压裂施工发生大量丢段、弃段,严重影响了页岩气井产量。考虑到页岩气井变形点普遍分布在套管跟端位置,因此认为多级压裂过程中的应力累积可能是导致套管变形的主要原因,针对该观点对多级压裂过程中的近井筒地应力变化规律及其对套管载荷的影响展开研究。首先,统计分析了威荣区块套管变形形状特征和分布特征;然后以威荣M井为例,建立多级压裂数值模型,计算近井地应力随压裂级数的变化规律;在此基础上,以最后一级压裂段作为研究对象,建立套管-水泥环-地层组合体模型,研究不同地应力条件下套管载荷的大小。研究结果表明:在多级水力裂缝起裂和扩展过程中,多级压裂产生的诱导应力会对后续压裂段产生影响,导致近井筒地应力发生非均匀累积;随着多级压裂过程中地应力累积的影响,研究点处的套管等效应力逐渐增加。该研究成果可为多级压裂过程中套管完整性控制提供参考。

关键词： S3D   支架流水号   Pcf   CAESAR   ACAD_VBA   载荷条件  

摘要： 本文介绍一种配管专业使用S3D进行应力条件带Pcf提出、应力专业CAESAR Ⅱ导入、完后通过MDB文件等计算书文件进行应力节点信息返回并导入S3D,最终实现支架流水号、形式、受力、位移等的精确可靠传输;通过S3D支架位置信息导出,结合应力计算书和Excel数据处理,编写ACAD数据提取和图块插入代码,实现载荷条件的自动绘制,提升配管、应力和结构专业交互的效率和质量。

关键词： 扭转   多槽型   开口   应力   载荷  

摘要： 多槽矩形开口结构是飞机上的一种特殊结构形式,在扭矩作用下的变形和应力分布状态复杂。文中推导了多槽矩型开口结构在扭转载荷下应力计算表达式,研究了其应力分布规律和特点。不需要借助有限元软件即可实现多槽型开口结构应力计算,在飞机设计初期可以加快飞机设计进程,提高计算效率;该文研究结果可用于飞机多舱体开口结构设计。

关键词： deep rock   excavation unloading   unloading confining pressure   three-dimensional high stress   strengthweakening effect   impact disturbance  

摘要： In the process of deep projects excavation,deep rock often experiences a full stress process from high stress to unloading and then to impact disturbance *** study the dynamic characteristics of three-dimensional high stressed red sandstone subjected to unloading and impact loads,impact compression tests were conducted on red sandstone under confining pressure unloading conditions using a modified split Hopkinson pressure *** disturbance tests of uniaxial pre-stressed rock were also conducted(without considering confining pressure unloading effect).The results demonstrate that the impact compression strength of red sandstone shows an obvious strain rate *** an approximately equal strain rate,the dynamic strength of red sandstone under confining unloading conditions is less than that in the uniaxial pre-stressed impact compression *** pressure unloading produces a strength-weakening effect,and the dynamic strength weakening factor(DSWF)is also *** results also indicate that the strain rate of the rock and the incident energy change in a logarithmic *** similar incident energies,unloading results in a higher strain rate in pre-stressed *** to the experimental analysis,unloading does not affect the failure mode,but reduces the dynamic strength of pre-stressed *** influence of confining pressure unloading on the shear strength parameters(cohesion and friction angle)is *** the same external energy impact compression,prestressed rock subjected to unloading is more likely to be ***,the effect of unloading on the rock mechanical characteristics should be considered in deep rock project excavation design.

关键词： elastic-plastic   spherical stress wave   linear hardening model   unloading rate  

摘要： Based on the linear hardening plastic constitutive model, the theoretical solution of the elastic-plastic spherical stress wave field under impact load is established. Firstly, the influence of the impact load unloading rate on the propagation of the spherical stress wave is analyzed, and three different types of propagation images are obtained. On this basis, the method of theoretically calculating the spherical wave equation in elastic stage, plastic loading stage and unloading stage is established separately, and the calculation scheme of particle displacement, particle velocity, stress and strain is given. Compared with the existing theoretical methods, this method takes into account the different propagation patterns of the stress waves under different unloading rates, and shows how to calculate the stress wave parameters in unloading stage, which is more applicable. This method is used to calculate the elastic-plastic spherical stress wave field under constant shock load and exponential attenuation shock load. The calculated results are in good agreement with those from the existing theoretical method and numerical simulation results in the elastic stage and also in the plastic loading stage. In the unloading stage, the existing theoretical method is no longer applicable, while the results obtained in this paper are in good agreement with the numerical simulation results, which verifies the correctness of the theoretical method.

关键词： 弹塑性   球面应力波   线性硬化模型   卸载速率  

摘要： 基于线性硬化塑性本构模型,建立了冲击载荷作用下弹塑性球面应力波场的理论求解方法.首先,分析了冲击载荷卸载速率对球面应力波传播的影响,得到了3种不同类型的应力波传播图像.在此基础上,建立了弹性阶段、塑性加载阶段以及卸载阶段球面波动方程的理论求解方法,给出了质点位移、质点速度、应力和应变等物理量的计算方案.与已有理论方法相比,该方法考虑了不同载荷卸载速率条件下应力波的不同传播情况,并且给出了卸载阶段应力波参量计算方法,具有更广的适用范围.利用上述方法计算了恒定冲击载荷和不同指数衰减冲击载荷作用下弹塑性球面应力波场参量,在弹性阶段和塑性加载阶段,理论计算得到的物理量与已有理论方法和数值模拟结果基本吻合,在卸载阶段,已有理论方法不再适用,而本文理论计算得到的物理量与数值模拟结果基本吻合,验证了该理论方法的正确性.

关键词： 涂层双管系统   有限元分析   热生长氧化物  

摘要： 采用有限元顺次耦合的方法,开展了热机载荷作用下新型涂层双管系统传热和应力分析,初步研究了关键特征参量对系统传热和应力分布的影响。结果表明:在稳态工作条件下,热障涂层为主蒸汽管道提供了足够的隔热保护,但由温度梯度产生的热应力对系统结构完整性产生了很大影响;系统中环向应力远大于径向应力,最大环向应力出现在TGO/BC界面靠近TGO侧的余弦波峰处;此外,TC层厚度、TC层热膨胀系数、冷却蒸汽的温度和压力决定了系统的温度和应力分布。

关键词： coated steam dual pipe system   finite element analysis   thermally grown oxides  

摘要： Using a sequentially coupled simulation procedure, the thermal transfer and stress analysis of a novel coated steam dual pipe system under thermo-mechanical loading were carried out. The influences of key characteristic parameters on the temperature and stress distribution of the system were investigated. The results show that under steady state working conditions, the thermal barrier coating contributes to the effective thermal insulating protection for the primary steel pipe, but the thermal stress generated due to the significant temperature gradient has a significant impact on the structural integrity of the system. The hoop stress in the system is much larger than the radial stress, and the maximum hoop stress is located at the cosine peak of the TGO/BC interface near the TGO side. In addition, the thickness of the TC, the thermal expansion coefficient of the TC, and the temperature and pressure of the cooling steam determine the temperature and stress distribution of the system.

关键词： 地铁转向架构架   应力谱   载荷谱   统计推断   最短周期  

摘要： 为了适应城市的快速发展,地铁成为城市轨道交通的主要建设目标。在地铁车辆的不断运营下,转向架构架关键疲劳控制部位出现裂纹,严重影响行车安全。根据线路实测数据建立载荷谱对结构进行评估是目前常用方法,由于测试成本等因素,不能对整个服役周期进行跟踪试验,根据有限的样本统计推断出总体的载荷谱和应力谱能够为构架的疲劳可靠性研究提供依据。本文基于某型号地铁转向架构架的长期跟踪试验,获得时间跨度十六个月的数据信息,开展了以下研究:(1)通过对实测载荷信号的预处理,把载荷信号分为主体载荷和局部载荷,从时域和频域的角度开展研究了直曲线与加减速工况下的特征。结果表明构架主体载荷同线路条件相关联,局部载荷与车辆运行速度相关联。构架在频域上以低频振动为主,在线路和运行速度的影响下会产生同构架固有频率与电机转频相关联的高频振动。(2)通过对实测应力信号的预处理,选取构架4个关键疲劳控制区域的16个测点,分析了构架在不同时段线路行驶时不同区域的应力变化。结果表明,当车辆在下行2时段行驶时,构架各关键部位等效应力较大。同时根据车辆行驶速度和角速度信号发现,当车辆以较快速度行驶在曲线线路较多的第1号站间和第11号站间时测点等效应力较大。(3)选取构架上不同区域等效应力较大的8个测点和能够通过实际测试直接得到的菱形载荷与制动载荷,通过雨流计数法获得单天实测谱样本,并通过威布尔分布拟合与拟合检验,并进行异常值剔除,得到各参数样本167～183,通过对各参数的统计推断,得到变量参数符合正态分布,并以此为基础编制了统计应力谱和载荷谱。(4)将获得的参数样本按照样本量将整个试验周期的数据分为三个组,并对每个组单独研究,通过抽样样本和区间总体的方差齐性检验和独立样本t检验,获得代表区间总体分布情况的最少样本量,进而得到代表整个试验周期数据分布情况的最短跟踪周期,结果显示,对于8个应力测点至少需要29个单天测试样本;对于菱形载荷和制动载荷至少需要13个单天测试样本。图60幅,表27个,参考文献77篇。