abaqus的非线性屈曲计算真的用的是切线刚度么

kosoa

abaqus里非线性屈曲计算除了用弧长法外，好像用static+buckle计算的结果不太理想，与弧长法计算的结果区别较大。
而同样的问题在marc里，用static+buckle计算的结果可以很接近弧长法计算的结果（见图片）。

于是有一个疑问：abaqus里用static+buckle计算时，buckle步所用的刚度真的是上一步static结束时的切线刚度么？
悬赏问题：static+buckle计算与弧长法（Riks）计算能得到相近结果的方法。

liukunbendan

这个...我不懂

kosoa

请大家各抒己见阿

iambadman

非线性屈曲不是用切线刚度，因为当切线水平的时候会无法迭代。所以才有弧长法来代替（其实可以看作是一种改进）。

另外就是ABAQUS的实际所用的N-R法也是有改进的，比如并不是迭代一次调整一次刚度，而且迭代几次再做调整。

kosoa

6.2.3 Eigenvalue buckling prediction
Order of calculation and formation of the stiffness matrices

In an eigenvalue buckling prediction step Abaqus/Standard first does a static perturbation analysis to determine the incremental stresses, , due to . If the base state did not include geometric nonlinearity, the stiffness matrix used in this static perturbation analysis is the tangent elastic stiffness. If the base state did include geometric nonlinearity, initial stress and load stiffness terms (due to the preload, ) are included. The stiffness matrix corresponding to and is then formed.

In the eigenvalue extraction portion of the buckling step, the stiffness matrix corresponding to the base state geometry is formed. Initial stress and the load stiffness terms due to the preload, , are always included regardless of whether or not geometric nonlinearity is included and are calculated based on the geometry of the base state.

kosoa

继续悬赏。。。

kosoa

继续悬赏。。。

kosoa

继续悬赏。。。

kosoa

用static+buckle计算的悬赏继续

kosoa

用static+buckle计算的悬赏继续..

littlestudent

哥们，你用的是marc吧？

dabbie

我只知道非线性屈曲计算只能用弧长法