大型风力发电机组机舱座极限强度计算方法与应用

针对大型风力发电机组机舱座的热点应力分布和应力值的随机变化问题,利用有限元理论和线性叠加理论,分析了大型风力发电机组机舱座在其设计寿命周期内所承受的极限应力,结合载荷遍历法逐一求解机舱座的热点处应力值,从中选出最大应力值作为机舱座的设计参考值,并与一般的极限载荷法进行比较。结果表明,采用载荷遍历法所得的应力值较一般的极限载荷工况法更接近热点的实际值,更准确地反映了热点处的应力值,为结构设计的可靠性和优化提供了理论依据。     

3MW双馈型风力发电机组主机架结构有限元分析

通过对有限元方法理论的研究,采用ANSYS Workbench对风力发电机组主机架进行强度分析,考虑主轴系统对主机架强度的影响,用杆单元模拟主轴承滚动体,提高载荷的传递效果,机架应力分析结果满足强度要求,并在此基础上提供机架设计修改意见。根据疲劳分析理论,采用应力分析方法对铸造机架进行疲劳分析。为新型机架的结构设计提供了依据。     

GH4169热辅助切削过程分析

高温合金GH4169作为典型的难加工材料具有切削力大、刀具磨损严重等特点.热辅助切削是一种利用外部热源降低工件强度、减小切削力改善切削性能的有效方法.基于有限元方法分析了不同热辅助温度对GH4169切削过程的影响规律,结果表明:热辅助温度越高,切削力越小,越容易产生带状切屑,表面残余拉应力越小,表层残余压应力越大.     

66 kV干式空心并联电抗器抗震特性仿真分析

应用ANSYS软件建立了66 kV干式空心并联电抗器的三维有限元模型,在运用Block Lances法对电抗器结构进行模态分析的基础上,采用振型分解法对8烈度等级下电抗器结构进行了地震响应分析计算.计算结果表明,地震动作用下电抗器的垂直位移要比水平位移小一个数量级,但水平应力却与垂直应力相差不大;支架部分结构是整体结构中最复杂的部分,而且从分析计算中发现该部分是结构中最薄弱的部分,应该是抗震分析中首要关注的地方,特别是绝缘子部分,其许用应力较低,是结构抗震强度验算的关键;电抗器结构在地震动作用下能满足抗震设计强度要求,应力集中处的最大应力小于材料屈服极限.     

大型水平轴风力机塔筒门洞的强度研究

为了实现某大型水平轴风力机塔筒底部门洞的抗极限与疲劳强度设计,基于热点应力法,建立塔筒门洞的有限元模型,并应用疲劳分析软件,分析计算得到门洞焊趾处的极限与疲劳强度。在此基础上,考察门洞结构参数如门框宽度、门框长度、塔筒壁厚对焊趾疲劳损伤的影响,并给出相应的结构优化方案。结果表明,所提出的方法在大型水平轴风力机塔筒门洞设计上具有可行性和有效性。     

凝汽器管板强度的矩阵位移分析法

采用力学中的矩阵位移法,将HEI标准中所提出的管板梁条力学模型进行了单元离散分析和整体解析,以矩阵位移法为内核算法,在VS2010环境中使用VB.NET语言编写了专用计算软件,并对HEI中的实例进行计算。计算表明:软件计算输出的最大弯矩、最大应力及最大挠度数据与HEI算例中给出的结果相比,相对误差在1%以内;与采用ANSYS-APDL计算的弯矩值相比,自编软件计算的弯矩结果误差在1%以内;在凝汽器管板强度分析计算中采用矩阵位移法对管板梁条力学模型进行求解是可行的。     

MW级风电机组的后机架结构计算及优化

以某2 MW风电机组后机架为分析对象,利用ANSYS和FESAFE对后机架的板和焊缝进行极限和疲劳强度计算,计算过程中充分利用了总体模型载荷路径完整和子模型结构细节较多的优点,得到了板和焊缝的极限和疲劳安全系数,并依据安全系数分布对后机架进行了结构优化,优化后的结果表明,后机架的极限和疲劳强度满足设计要求,该方法可为后机架的结构设计和优化提供一种实用的手段。     

基于高加解列的小扰动理论局限性的定量研究

首先将目前的节能分析方法定义为结合汽轮机变工况计算的大扰动法和线性化处理的小扰动法.再以国产600MW凝汽式机组为例,选取小扰动中影响较大的1号加热器解列,分别用变工况计算和小扰动矩阵法得到两类方法的热耗率相对误差仅为0.1473%,从而得出结论:在扰动较小时完全可以使用小扰动法进行分析,而不必进行繁琐的变工况计算.文章摒弃了以往研究仅限于理论分析的缺点,用定量计算验证了小扰动法的可用性,对电厂热经济性分析方法的研究具有重要意义.     

基于滑面正应力修正的极限平衡法的锚固边坡稳定性分析

为研究滑面正应力分布对极限平衡法计算边坡安全系数的影响,针对预应力锚索加固边坡,利用滑面正应力修正的极限平衡法建立了含安全系数和两个待定参数的三个方程组,通过公式推导获得了安全系数的显示解答。工程实例应用结果表明,采用该方法分析边坡的稳定性合理有效。     

轴向裂纹对U型管强度的影响

针对在高温和管道压力作用下U型管的弯管处容易产生裂纹,这些裂纹对U型管上应力的分布产生严重影响,降低的了U型管的承载能力.本文采用ABAQUS软件对存在轴向裂纹的U型管进行分析,得到不同长度、深度及多个不同位置裂纹间相互作用对U型管强度的影响.分析结果表明,裂纹的长度与深度之比越小,裂纹对U型管强度的削弱效果越小,反之越大.     

Sealing performance and mechanical behavior of PEMFCs sealing system based on thermodynamic coupling

The reliability of sealing system is closely related to the work performance of PEMFCs. The model of steel-strip PEMFCs is established in this paper, the stress-strain distribution of sealing system in single-cell and multi-cells structures under three different working temperature were investigated. Effects of compression ratio, fluid pressure, dislocation and dimension of gasket on the sealing performance and mechanical behavior of PEMFCs were studied. The results show that the sealing performances of single-cell and multi-cells structures are similar under different working temperatures. Temperature has a great influence on the von-Mises stress of sealing system and the deformation of MEA frame. The research results of single-cell can be extended to the multi-cells, but the influence of temperature can't be ignored. With the increasing of compression ratio, fluid pressure and dimension, the sealing performance also be improved. Excessive dislocation may aggravate the deformation of MEA frame. The high stress area appears inside cross section which is prone to cause seal failure and full cells collapse.     

Experimental and finite element prediction of bursting pressure in compound cylinders

Aluminium cylinders with a constant ratio of outer to inner radii, k=2.2, with different diametral interferences and various shrinkage radii were subjected to bursting and autofrettage pressures. Numerical simulations of the compound cylinders were also performed using the finite element code, NISA. The results can predict the optimum shrinkage radius to a reasonable accuracy with the use of finite element analysis. This radius corresponds to the situation when the maximum von-Mises stress at the internal radii of both the inner and outer cylinders become equal. It was shown that the maximum von-Mises stress across the wall of the cylinder is at the minimum at this shrinkage radius. The optimum diametral interference was found to be that which sufficiently brought the contact surface of the inner and outer cylinders to the point of yielding. Should the shrinkage pressure exceed the elastic limit, the pressure capacity of the cylinder will not be improved. The numerical and experimental results show that autofrettage had no effect on the bursting pressure of the thick-walled compound cylinder for the material tested.     

Theoretical and finite-element modeling of autofrettage process in strain-hardening thick-walled cylinders

The optimum autofrettage pressure and the optimum radius of the elastic–plastic boundary of strain-hardening cylinders in plane strain and plane stress have been studied theoretically and by finite-element modeling. Equivalent von-Mises stress is used as yield criterion. Comparison of the results of the two methods shows good agreement. Although there is no explicit expression for the optimum autofrettage pressure in plane stress, the equation for plane strain can be used with good accuracy. It has also been observed that the optimum autofrettage pressure is not a constant value but depends on working pressure.     

Excel在BWRS方程密度迭代中的应用

在天然气密度迭代求解中,利用Excel中单变量求解功能和函数功能,可以把各种复杂的迭代计算变成简单直观的菜单和工具栏操作,也可获得准确的计算结果,且不需要编程,通俗易懂。     

发动机缸体瞬态强度分析

针对发动机缸体结构复杂,工作过程中受到多种交变激振力作用的特点,建立了较详细的缸体瞬态强度分析有限元模型,模拟了缸体在发动机工作过程中的动态强度变化历程。得出：缸体与缸盖及变速器相连的紧固螺栓孔周围的整体应力水平较高,但随发动机工作负荷变化的波动量较小;缸体主轴承座周围动态应力和变形成分较高,且随发动机工作负荷变化的波动量较大;而缸体两侧壁的动态变形和应力与静态变形和应力水平较低。研究表明：在建模时考虑活塞和曲轴对缸体的接触作用,合理简化缸体结构,准确深入揭示工作过程中缸体的动态强度随时间的变化,为缸体动态结构强度设计提供可靠依据。     

某燃气轮机高温涡轮盘的破裂转速数值预测方法研究与试验验证

为确定某燃气轮机涡轮盘的破裂转速,设计并开展了轮盘破裂转速试验,得到了其真实破裂转速,并与多种数值预测方法预测的轮盘破裂转速进行对比。结果表明：对于某型燃气轮机高温涡轮盘而言,最大应力法对破裂转速的预测精度最高,与试验转速相比,精度误差为0.9%,可以预测裂纹的起始开裂位置以及轮盘的破裂模式;极限应变法与残余变形法预测的破裂转速的精度相当,与试验转速相比,精度误差分别为4.8%和6.2%,由于有限元方法会同时计算应变和应力,因此建议优先选用应力准则预测;平均周向应力法计算相比较简便,计算时间短,但是精度较差,精度约为12.3%,可以用于粗略估计破裂转速。     

PVA纤维对纳米水泥基复合材料单轴拉伸性能的影响

为研究PVA纤维掺量对掺纳米SiO_2水泥基复合材料抗拉性能的影响,通过单轴拉伸试验测得了试件的极限拉伸应变和极限拉伸应力,并得到了试件应力—应变关系曲线。纳米SiO_2的质量掺量为2%,PVA纤维采用五种体积掺量(0.3%、0.6%、0.9%、1.2%、1.5%)。结果表明,PVA纤维的掺加增大了纳米水泥基复合材料单轴拉伸试件的极限拉应变和极限拉应力。当PVA纤维体积掺量不大于1.5%时,随PVA纤维掺量的增大,试件极限拉应变逐渐增大,极限拉应力先增大后减小。当PVA纤维体积掺量分别为1.5%、1.2%时,试件极限拉应变和极限拉应力分别达到最大值;PVA纤维水泥基复合材料中掺加2%纳米SiO_2后,整体上提高了试件的极限拉应力,但试件极限拉应变变化不明显,纳米SiO_2使PVA纤维增强水泥基复合材料的抗拉伸性能得到了进一步提高。研究成果可为工程应用提供指导。     

Study on the degradation mechanism of the frame for membrane electrode assembly in proton exchange membrane fuel cell

The membrane electrode assembly (MEA) in the proton exchange membrane (PEM) fuel cell needs to be encapsulated by a frame to improve its assembly strength and sealing performance. However, irreversible degradation usually occurs to invalidate the frame and cause the fuel cell fail. In this study, a series of experiments are conducted to simulate operating environment in the fuel cell, and degradation mechanism of the frame is explored. Changes of tensile strength, peeling strength, shearing strength, and bending strength are adopted to evaluate the frame stability, and effects of temperature, water, and acid on these indexes are quantified. It is found that the peeling strength has the most significant decline, which is the primary failure form of the frame. Acid solution provides the main contribution to this failure. In acid solution, hydrogen ions and water molecules permeate the frame, resulting in rapid degradation and separation of the bonding interface. This study reveals the degradation process of the frame for the first time, and helps enhance our understanding of the frame failure.     

汽轮发电机组轴系扭转疲劳性能估算方法的参数灵敏度分析

采用参数灵敏度分析方法,详细讨论了各相关参数对某汽轮发电机组轴系扭转疲劳性能指标的敏感性.结果表明:拉伸强度、尺寸系数和表面加工系数对疲劳性能的灵敏度相同,其灵敏度因子均为1;随着应力集中系数的增大,其灵敏度因子线性增大,当应力集中系数约大于1.68时,其灵敏度因子大于1,成为影响构件疲劳强度的最主要因素;疲劳缺口敏感系数对疲劳强度的影响最小;由于修正参数选取时的不确定性造成的寿命损耗估算偏差最大可达约15.5倍.