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压电层合板的B样条小波有限元半解析法 总被引:1,自引:0,他引:1
利用小波有限元法的优越性可方便地求解压电材料与复合材料混合层合板的某些静力学问题。根据层合结构的特点,将区间B样条尺度函数作为插值函数离散结构的平面域,应用压电材料修正后的H-R(Hellinger-Reissner)变分原理推导了压电材料的Hamilton正则方程的区间B样条小波(BSWI)元列式。该BSWI元的主要特点之一是厚度方向是解析解形式的。针对具体问题的求解,为了保证各层之间力学量和电学量的连续性,进一步应用了状态转移矩阵技术。数值算例表明所提出的区间B样条小波单元是成功的。采用推导压电材料BSWI元的方法可建立磁电弹性材料类似的BSWI元。 相似文献
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在结构优化过程中,精确的结构参数灵敏度分析是最主要的困难之一。该文在Hamilton体系下推导了复合材料层合板特征值响应灵敏度系数的控制方程,基于BSWI(B-spline wavelet on the interval)样条小波有限元方法,利用二分法求得了四边固支复合材料层合板前四阶特征值对材料密度的灵敏度系数,并与有限差分法所得结果相比较,证明了该文所提出方法的可靠性。另外,该方法能够方便地拓展到复杂层合板壳结构以及智能材料层合板特征值灵敏度系数的求解问题中去。 相似文献
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依据复合材料内部纤维在基体内的排布规律及层合板铺层特性,基于多尺度方法,建立单层板和层合板代表性体积单元(RVE)模型,施加相应的边界条件,预测单层板的热膨胀系数和工程常数,进而预测复合材料层合板各向异性的等效热膨胀系数。通过与实验数据对比发现,基于正六边形单层板RVE模型预测的热膨胀系数,相比理论预测值,整体更接近实验值,其中预测的单向T300/5208碳纤维增强环氧树脂基复合材料、P75/934碳纤维增强环氧树脂基复合材料和C6000/Pi碳纤维增强环氧树脂基复合材料的横向热膨胀系数与实验结果的误差分别只有3%、1%和2%;采用单层板RVE预测的单向ECR/Derakane 510C玻璃纤维增强乙烯基酯树脂基复合材料的工程常数与实验值最大相差7.5%;层合板RVE模型预测的正交AS4/8552碳纤维增强环氧树脂基复合材料厚度方向的热膨胀系数与实验结果误差可以忽略,只有0.08%。最后以大型复合结构常用的正交铺层结构为研究对象,基于给出的单层板和层合板RVE模型预测了不同铺层复合材料烟道层合板的等效热膨胀系数,环向铺层比例对厚度方向的热膨胀系数影响较小。 相似文献
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通过对缝合复合材料层板进行低速冲击和冲击后压缩实验, 研究了不同类型的缝合复合材料层板的冲击损伤特性及冲击后压缩的剩余强度。实验研究表明: 基体损伤和分层是缝合层板与未缝合层板低速冲击的主要损伤模式, 缝合层板具有更好的抗冲击性能, 更高的冲击后压缩强度。缝合密度越大的层板其抗冲击性能越好, 冲击后压缩强度越高。缝合方向为0°的缝合层板较缝合方向为90°的缝合层板具有更好的抗冲击性能和更高的冲击后压缩强度。增加0°方向铺层, 减少45°、-45°方向铺层, 可以提高缝合层板的抗冲击性能和冲击后压缩强度。 相似文献
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B. Boroomand A. A. Tabatabaei E. Oate 《International journal for numerical methods in engineering》2005,63(3):351-379
A stabilized version of the finite point method (FPM) is presented. A source of instability due to the evaluation of the base function using a least square procedure is discussed. A suitable mapping is proposed and employed to eliminate the ill‐conditioning effect due to directional arrangement of the points. A step by step algorithm is given for finding the local rotated axes and the dimensions of the cloud using local average spacing and inertia moments of the points distribution. It is shown that the conventional version of FPM may lead to wrong results when the proposed mapping algorithm is not used. It is shown that another source for instability and non‐monotonic convergence rate in collocation methods lies in the treatment of Neumann boundary conditions. Unlike the conventional FPM, in this work the Neumann boundary conditions and the equilibrium equations appear simultaneously in a weight equation similar to that of weighted residual methods. The stabilization procedure may be considered as an interpretation of the finite calculus (FIC) method. The main difference between the two stabilization procedures lies in choosing the characteristic length in FIC and the weight of the boundary residual in the proposed method. The new approach also provides a unique definition for the sign of the stabilization terms. The reasons for using stabilization terms only at the boundaries is discussed and the two methods are compared. Several numerical examples are presented to demonstrate the performance and convergence of the proposed methods. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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阐述了磁性法测定钢中残余奥氏体含量的原理和方法,并研制了一种基于磁性法的钢中残余奥氏体含量测定装置。该测定装置可以实现换向法、甩脱法和动态法等3种残余奥氏体含量测定方法,其中换向法和甩脱法以不同方式静态测定残余奥氏体含量,动态法能够在试件拉伸过程中连续、快速地动态测定残余奥氏体含量与应变的对应关系。该测定装置以LabVIEW为平台,构成了虚拟仪器系统,对数据进行采集、分析和处理,实现了可视化操作、自动测量、曲线显示和数据保存等功能。使用该装置采用3种方法分别对M50NiL轴承钢中的残余奥氏体含量进行了测定,试验结果表明该测定装置能够精确地测定钢中的残余奥氏体含量。 相似文献
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Marc S. Ingber Andrea A. Mammoli Mary J. Brown 《International journal for numerical methods in engineering》2001,52(4):417-432
In many cases, boundary integral equations contain a domain integral. This can be evaluated by discretization of the domain into domain elements. Historically, this was seen as going against the spirit of boundary element methods, and several methods were developed to avoid this discretization, notably dual and multiple reciprocity methods and particular solution methods. These involved the representation of the interior function with a set of basis functions, generally of the radial type. In this study, meshless methods (dual reciprocity and particular solution) are compared to the direct domain integration methods. The domain integrals are evaluated using traditional methods and also with multipole acceleration. It is found that the direct integration always results in better accuracy, as well as smaller computation times. In addition, the multipole method further improves on the computation times, in particular where multiple evaluations of the integral are required, as when iterative solvers are used. The additional error produced by the multipole acceleration is negligible. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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在聚合物共混体系中,界面张力对聚合物相容性有着重要影响,决定着相与相之间的粘接性,成为控制其最终相态结构的一个重要因素,是研究多相聚合物相态结构的基础。文中综述了聚合物熔体界面张力的测定方法,这些测定方法主要有热力学方法、流变学方法以及动力学方法三大类;介绍了每种方法的基本原理,并对其优缺点及适用范围进行了简单说明。其中,动力学方法是使用最多、相对准确的,对该方法进行了重点介绍,并且讨论了动力学方法中熔体粘弹性对界面张力测定的影响。 相似文献
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Based on a combination of Hellinger–Reissner principle with its dual, a mixed/hybrid method of non‐saddle point type has been presented in the previous papers. In the paper, an application of the method to two‐dimensional elasticity problems is considered in a manner of combination of mathematical analysis with numerical investigation. How to construct a combined hybrid scheme of high performance is discussed, and several four‐node quadrilateral CH‐elements are systematically verified. In brief, this paper shows that for the hybrid element scheme, the energy compatibility condition, introduced in Zhou (Combined hybrid finite element method without requirement for Babuska‐Brezzi condition, to appear) is the ultimate key to the achievement of high performance. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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田菁胶是从田菁种子胚乳中提取的一种天然多糖类高分子有机物。天然的化学结构反映出的理化性质限制了其应用和推广。化学结构式的修饰改进是扩大其应用的有效手段。修饰改进后的田菁胶无毒、无污染,在石油开采、煤开采、纺织、印刷、造纸和食品等领域得到了广泛应用。文中对羧甲基法、羟乙基法、羟丙基法、交联法、羟烷基-羧甲基法、羧甲基-羟烷基法、阳离子法、酶解法、氧化法和两性法等田菁胶化学结构式的主要修饰改进方法进行了详述。总结了修饰改进技术注意事项,并对前景进行了展望。 相似文献