分区混合有限元法计算反平面复合材料切口应力强度因子

本文先推导反平面复合材料切口尖端位移多应力场,然后用分区混合有限元法计算切口应力强度因子。     

极坐标有限条法解扁球壳问题

本文用有限条法解扁球壳问题,对于轴对称问题与位移和内力沿环向按cosnθ或sinnθ分布的非轴对称问题,分别推导了三类壳元(圆底壳元,圆孔外无限壳元,圆环底壳元)刚度矩阵的精确解。对于沿环向按cosnθ或sinnθ分布的环形面荷载和环形线荷载推导了单元等价节线荷载的表达式。编制了相应的计算程序,计算了典型例题。结果表明,此法具有计算工作量少而计算精度高的优点。     

一个不闭锁和抗畸变的四边形厚板元

构造一个彻底消除剪切闭锁现象并且对网格畸变不敏感的四边形厚薄板通用单元RPAQ。在方法上有三个特点：第一,在厚板挠度和转角的试函数中,采用了合理匹配方案,从而在源头上彻底消除了剪切闭锁现象;第二,采用四边形面积坐标,以代替通常的等参坐标,从而使网格畸变时仍然保持高精度;第三,采用广义协调元做法,使协调条件的采用灵活多样,并保证单元的收敛性。进行了一系列数值例题测试,表明单元RPAQ能自动消除闭锁现象,在由薄板到厚板的不同情况下,在各种网格畸变的情况下,都能体现出良好的精度和数值稳定性。     

三维切口尖端应力应变场

本文利用双重幂级数展开法分析三维切口尖端应力应变奇异性，通过切口边界条件导出切口特征方程，进而求得不同切口内角下特征值序列解答，最后推得切口尖端应力应变场。     

GENERALIZED VARIATIONAL PRINCIPLES WITH SEVERAL ARBITRARY PARAMETERS AND THE VARIABLE SUBSTITUTION AND MULTIPLIER METHOD

The functional transformations of variational principles in elasticity are classified asthree patterns:Ⅰ relaxation pattern,Ⅱ augmented pattern and Ⅲ equivalent pattern.On the basis of pattern Ⅲ,the generalized variational principles with several arbitraryparameters are formulated and their functionals are defined They are:the generalizedprinciple of single variable u with several parameters,the generalized principle of twovariables u,σ with several parameters,the generalized principle of two variables u,εwith several parameters,and the generalized principle of three veriables u,ε.σ withseveral parameters.From these principles,a series of new forms of equivalent functionalscan be obtained.When the values of these parameters are properly chosen.a series of finiteelement models can be formulated.In this paper,the question of losing effectiveness for Lagrange multiplier method isalso discussed.In order to“recover”effectiveness for multiplier method,a modifiedmethod,namely,the variable substitutio     

分区混合有限元法计算应力强度因子

本文应用分区混合能量原理,提出分区混合有限元法,用以计算应力强度因子,方法的特点是:在裂纹尖端附近采用应力型奇异单元,在外部采用位移型常规单元。由于针对问题的受力特点,合理地把应力型与位移型、奇异元与常规元、解析解与数值解加以结合,各自发挥所长,从而能以较疏的网格取得较高的精度。 本文不仅为计算应力强度因子提供了一种有特点的有效解法,而且为分区混合有限元法的广泛应用提供了最初的例证。     

利用Ferguson曲面构造广义协调板单元

根据广义协调原理，首先利用Ｆｅｒｇｕｓｏｎ曲面构造出薄板弯曲单元，将中厚度板视为双向深梁，由Ｔｉｍｏｓｈｅｎｋｏ理论拟合单元边界，利用Ｆｅｒｇｕｓｏｎ曲面的张量积性质，将薄板单元推广到中厚度板。数值结果表明此单元精度高，适应性强，且不出现剪切闭锁现象。     

The expression of stress and strain at the tip of notch in reissner plate

In this paper, the eigenequation of notch in Reissner plate is derived by the eigenfunction method. Eigenvalues of different notches with different angles are calculated by Muller iteration method.The expression of stress and strain at the tip of notch in Reissner plate is obtained.     

圆底扁球壳在偏心集中载荷下的计算

本文讨论圆底扁球壳在非对称载荷下的计算.给出了六种偏心集中载荷下的解,它们是:1.法向集中力,2.经线切向集中力,3.纬线切向集中力,4.切面内集中力偶.5.经线法面内集中力偶,6.纬线法面内集中力偶.此外,由偏心集中载荷的解还导出了按cosnθ分布的环形线载荷的解.