弯管中性线与内外拱间的面积压力差及其经向等效弯矩

对于内压作用下的任何弯管,因为弯管中线上径向向外的管壁表面积均要比中线上径向向内的管壁表面积大,两者面积之差在同一内压作用下产生面积压力差。整体环壳存在的面积压力差能整体自平衡,但是局部环壳的面积压力差能产生开弯效应,与相连工程管线之间为了平衡而引起经向等效弯矩,等效弯矩的计算模型与其两端面的边界条件有关。弯管的内壁表面积压力差的大小与管截面内径及内压有关。经向等效弯矩只与管截面圆内半径、弯曲半径、经向弯角及内压有关。     

异径弯管的无力矩环向应力解析解

提出以异径管单位高度（长度）的直径变化程度作为反映异径管结构特征的无因次量，并定义为异径系数。根据异径弯管横截面管径随经向弯角而变化及其锥形结构的两个特点，推导了内压作用下异径弯管无力矩环向应力武，最大环向应力位于大端内侧。该武可以作为工程中常见回转壳无力矩环向应力式的任意条件式，等径弯管、直管及异径直管的环向应力公式均是异径弯管环向应力武的一个特定条件的特例，本质上这些公式均是环向应力的薄膜解。计算环向薄膜应力时，一般来说．工程中各种鼻径管与连接直管之间的边缘应力可以忽略。     

相变对管道环焊缝残余应力的影响

利用ADINA程序计算了管道环焊缝接头未考虑相变和考虑相变两种情况下的残余应力,有限元分析中考虑了材料热物理性能参数和力学性能参数的温度相关性.结果表明,考虑相变应力比未考虑相变应力,其外表面的轴向压应力值增加,内表面的拉应力值降低;外表面的环向应力出现压应力,内表面的拉应力值降低,最大拉应力的峰值区偏向近缝区.这说明相变应力对管道接头焊缝和近缝区有较大的影响.计算结果与实测结果基本一致,对焊接接头的金相组织分析也验证了计算结果.     

交接环形耐压壳屈曲特性试验与数值研究

研究了不锈钢交接环形耐压壳在均匀外压作用下的屈曲性能。使用的交接环形耐压壳的截面半径为70.5 mm,壁厚为1.319 mm,圆周旋转半径为134 mm。制作了6个交接壳模型,并对其进行几何测量、静水外力试验和数值计算,在此基础上对交接环形耐压壳屈曲行为进行分析,研究了交接角度和环肋参数对屈曲的影响规律。结果表明,交接角度对交接环壳屈曲载荷没有影响,环肋的宽度和厚度达到一定阈值时,临界屈曲载荷值保持不变且接近于交接单元的屈曲载荷。     

流固耦合下核电一回路弯管内表面裂纹分析

为了了解压水堆一回路弯管内表面裂纹在流固耦合作用下的扩展状况,利用ANSYS Workbench建立了含环向内表面裂纹弯管的流固耦合模型,在不同约束条件下对不同位置的裂纹前缘应力和应力强度因子K进行了分析。分析结果表明:只有内压作用时,流固耦合会增大裂纹前缘K与应力,而且对外弯处裂纹影响大。只有闭合弯矩时,流固耦合会减小外弯处裂纹前缘K与应力。内弯处裂纹受压应力,流固耦合会减小压应力。只有张开弯矩时,流固耦合会增大内弯处裂纹前缘K与应力。外弯处裂纹受压应力,流固耦合会增大压应力。分析结果为核电一回路含缺陷弯管的安全性评价提供一定的依据。     

EJMA 第9版（含2011增补）无加强型波纹管环向膜应力公式的进一步推导和修订

在结合2013年第8期《压力容器》杂志刊登的《关于EJMA第9版（含2011增补）环向膜应力公式的修订探讨》一文的基础上,仅对U形波纹管环向膜应力公式进行了深入的推导,发现部分计算考虑不全面或有误,且未考虑外压对计算公式的影响。逐一对原标准公式及前文修订的公式进行了进一步的修订。后续将对加强型与Ω形波纹管进一步推导和修订。     

内压及扭矩载荷下无缺陷弯管的应力分析

分析在内压或扭矩载荷作用下非均匀壁厚椭圆弯管的应力分布，结果表明内压引起的最大应力随着弯管的截面不均匀度而变化，由此解释了工程实际中弯管失效的原因，同时也为求解弯管的塑性极限载荷奠定了基础。     

内压作用下弯管环向穿透裂纹应力强度因子分析

应力强度因子是缺陷结构安全评定的必需参数。利用有限元分析软件ANSYS建立了内压作用下弯管环向穿透裂纹模型,以管道外径、管道厚度、纵向裂纹角、裂纹半角、环向裂纹角为参数,对不同参数下的应力强度因子进行了计算。结果表明:应力强度因子与纵向裂纹角θ1无关;应力强度因子随裂纹半角θ的增大而增大;应力强度因子随环向裂纹角θ2的增大先减后增。依据计算结果对参数进行了无量纲化,继而拟合了内压作用下弯管环向穿透裂纹应力强度因子计算关系式。     

基于ANSYS的球壳开孔接管区应力分析

球壳开孔接管区的应力高且分布状况复杂。利用ANSYS软件,通过获取应力分布云图及线性化处理提取的各类应力,探讨了过渡圆角半径对球壳开孔接管区应力的影响。结果表明,球壳与接管连接处存在明显的应力集中。采用圆角过渡可以降低应力集中系数。只有圆角半径较大时,应力集中系数才会显著降低,并且主要是降低了其中的弯曲应力和峰值应力。当圆角半径增加到一定程度,应力集中系数降低极其缓慢。结果为工程实际中球壳开孔接管区圆角半径的选取提供借鉴。     

弯曲载荷下管道环焊缝裂纹应力强度因子评价模型及试验验证

裂纹缺陷是众多环焊缝缺陷中危险性最大的缺陷之一。油气管道在经过地质条件较差的区域时，当遭遇自然灾害，管道除内压作用外，还会承受额外的弯曲载荷，由此引起的大跨度管道弯曲变形容易引起环焊缝裂纹扩展，导致管道破裂。基于大量环焊缝裂纹有限元数据，拟合出了裂纹尖端应力强度因子的工程评估公式。按照子模型分析方法可以快速获得有限元结果数据且能保证精度，是一种高效获取全尺寸弯曲管道中裂纹应力强度因子拟合数据的方法。结合API 579中提供的环向裂纹应力强度因子理论公式，对应力强度因子计算公式进行了拟合，裂纹尺寸范围为0.03   

内压弯管在面内循环弯曲载荷作用下棘轮效应的研究

利用多轴试验机研究了内压及面内循环弯曲载荷作用下低碳钢弯管的棘轮效应。试验研究表明最大棘轮应变发生在顶线位置的环向。对于个别试件,内缘线位置也发现了环向棘轮应变,但所有试件的外缘线位置均未发现棘轮应变。内压不变时棘轮应变速率随面内循环弯曲载荷的增大而增大;面内循环弯曲载荷不变时,棘轮应变速率随内压的增大而增大。通过用户编程,采用Chen—Jiao—Kim随动强化模型,利用弹塑性有限元法对弯管进行了循环塑性分析。与试验结果相比,Chen—Jiao—Kim随动强化模型能给出较好的预测。采用C—TDF提出的等效塑性应变增量控制法确定了结构的棘轮边界。     

内压作用下异径管的应力分析及验证

利用有限元方法分析了内压作用下异径管的应力分布，结果表明：同心异径管大端向外的弯曲应力与薄膜应力叠加后使外壁组合应力下降、内壁组合应力上升，小端连接处直管内外壁均为轴向压应力；内压在非轴对称结构的偏心异径管的偏心侧大端和中部引起的环向应力最大，且偏心侧外壁的环向应力较内壁的环向应力大。实验结果与有限元分析结果一致，但存在一定误差，主要是与工程管件不均匀的力学性能及壁厚有关，因此，将直管的应力理论直接套用到异径管是不恰当的。     

内压载荷作用下含纵向穿透裂纹弯头的塑性极限载荷

弯头是管道系统中最薄弱、最容易失效的管件。研究含缺陷弯头的塑性承载能力在整个压力管道系统安全评定中占有重要地位。利用求取直管极限载荷的鼓胀系数法建立不考虑直管影响的含缺陷弯头的塑性极限载荷估算式。采用三维弹塑性有限元技术,对内压载荷作用下含纵向穿透裂纹弯头的塑性极限载荷进行系统分析。结果表明,裂纹削弱系数（PL／P LO）与厚径比（t／rm）无关,在实际工程应用中可忽略厚径比对裂纹削弱系数的影响。裂纹对长半径弯头的塑性极限承载能力影响程度明显大于对短半径弯头的。     

3D FE limit analysis model for multi-layer masonry structures reinforced with FRP strips

A heterogeneous full 3D limit analysis model for the evaluation of collapse loads of FRP-reinforced multi-layer masonry structures loaded in- and out-of-plane is presented. Four-noded rigid infinitely resistant tetrahedrons are used to model bricks, stones and filler. Three-noded rigid infinitely resistant triangles are used to model FRP strips. Plastic dissipation is allowed only at the interfaces between adjoining elements, i.e. on mortar joints reduced to interfaces, on brick-brick interfaces and on filler. A possible dissipation at the interfaces between FRP triangles and masonry wedges is also considered in order to take into account, in an approximate but effective way, the possible delamination of the strips from the supports. Italian code CNR-DT200 formulas are used as a reference to evaluate peak interface tangential strength. While the delamination from the support can be modeled only in an approximate way within limit analysis, the aim of the paper is to accurately reproduce the change in the failure mechanism observed in experiments due to the introduction of strengthening elements.A 3D approach to model masonry is used in order to take into account both the real texture of the panels along the thickness (i.e. multi-layer regular and irregular texture, presence of internal filler, etc.) and the presence of FRP strips either at the extrados or at the intrados of the structural elements.Two numerical examples are critically analyzed, consisting of a two leaf thick masonry wall simply supported at three edges, reinforced at the extrados and subjected to uniform lateral pressure and a complex three-layer tuff masonry shear wall with cavities filled with mortar and reinforced with horizontal and diagonal FRP strips at both faces. For the first example analyzed, full sensitivity analyses varying both FRP-brick peak strength and filler mechanical properties have been conducted in order to evaluate the capabilities of the model proposed when varying constituent materials mechanical properties. An additional FE simulation conducted with a standard code is also discussed to validate the model. When dealing with the second example, full comparisons with experimental data available are reported. Comparisons with experimental evidence and alternative FE procedures confirm that the limit analysis approach proposed may represent a valuable tool for predicting failure mechanisms and collapse loads of complex 3D multi-layer masonry structures reinforced with FRP strips.     

Limit moment for a smooth pipe bend under in-plane bending

A lower bound for the limit moment of a smooth circular pipe bend of uniform thickness is calculated with no restrictions on the geometry except those of thin shell theory, though the bend angle and the effect of any straight length attachments are not considered. Results of the analyses suggest that the (bend radius)/(pipe radius) ratio is of importance as well as the pipe factor (bend radius x thickness)/(pipe radius)², which is usually assumed to be the only important geometric parameter.     

Optimally reinforced cutouts in laminated circular cylindrical shells

The problem of designing a cutout in a load bearing structural member in the form of a shell, such that the cut structure maintains its stress state with a minimal departure from the stress state of the uncut structure is addressed herein. Symmetrically laminated composite circular cylindrical shells under hydrostatic compression and axial pressure are considered. Shallow thin shell (Donnell shell theory) lamination theory is utilized. The original (uncut) stiffness of the shell structures is recovered considerably by appropriately designing an edge reinforcement around the cutout. The buckling load of the designed shells are analyzed via the finite element method. An experimental investigation has been carried out to verify some of the results obtained from the finite element analysis. In the work presented, the reinforcement is modeled as a one-dimensional rod/beam type structural element.     

基于MEMS技术的金属应变式压力传感器优化设计

文中从金属应变式压力传感器的基本理论出发,以硅弹性膜铂应变电阻压力传感器为原型,推导了圆形和方形弹性膜片上电阻的变化率(dR/R)公式。通过比较,选用方形弹性膜为压力承压膜,以优化承压膜的宽厚比为出发点,用有限元方法对不同厚度方形膜片(宽度为2 mm)进行应力分析。由硅材料的屈服应力与最大位移的限制,确定了最优的膜厚范围;根据有限元仿真的结果对压力传感器进行优化设计,对所做压力传感器芯片进行测试,在6.00×104~1.06×105Pa的范围内,其精度优于50 Pa.