磁场对铁磁结构动态特性的影响

研究了两种铁磁材料结构(板梁和圆柱壳)在不同的磁场下固有频率的变化。频谱分析仪产生的扫频正弦信号通过压电陶瓷片对试件进行激励;压电薄膜作为感知元件再把感知信号送回频谱分析仪。根据共振原理,从频谱分析仪的频率响应曲线可以得到试件的各阶固有频率。通过改变外加磁场的大小,用同样的方法可以得到不同磁场下的固有频率。实验结果表明,铁磁板梁固有频率的变化很大程度上依赖于所施加磁场的方向:当磁场顺着板梁的长度方向时,板梁的固有频率会随着外加磁场的增大而增大;然而当磁场施加在板梁的厚度方向时,固有频率是先降低然后再升高。对铁磁材料圆柱壳,当磁场顺着圆柱壳的轴线方向增大时固有频率是逐渐增大然后达到一个饱和值。     

铁磁梁式板磁弹性初始后屈曲及缺陷敏感性分析

从铁磁板的磁弹性广义变分原理出发，通过对铁磁板内外的磁场和板变形 场的摄动技术以及采用经典Koiter理论，对横向磁场中铁磁悬臂、简支、固支梁式薄 板磁弹性稳定性的初始后屈曲行为及缺陷敏感性进行了定性研究. 解析地给出了悬臂板对初 始缺陷敏感，简支和固支板对初始缺陷不敏感等结果，对悬臂梁式板理论预测的临界磁场值 往往大于实验观测结果的现象从定性上给予了合理解释.     

斜磁场作用下铁磁梁式板的磁场摄动分析

基于磁场摄动技术和广义变分原理得到的磁力公式,对铁磁梁式板在斜磁场作用下的磁场和磁力摄动展开研究.给出了考虑磁场端部效应情形时铁磁梁式板的摄动磁场及其磁力摄动表达式,使得解析分析斜磁场作用下铁磁梁式板磁弹性耦合问题成为可能.研究表明:只有考虑了磁场端部效应的斜磁场磁力摄动公式才能模拟铁磁结构的弯曲模式且能够定性揭示铁磁简支梁式板弯曲构形为双半波形.     

Nonlinear vibration of beamplates with a delamination

The problem of beam-plates with a delamination located at an arbitrary site undergoing non-linear free vibration without damp is investigated. For this problem, nonlinear governing equations as well as the continuity, equilibrium and compatibility conditions are established. The Galerkin method and harmonic balance method are employed to find solutions. Finally, in some examples amplitude-frequency curves of the delaminated structure are presented in order to reveal some special dynamic features. Supported by the National Natural Science Foundation of China (No. 19872024).     

PERTURBATION ANALYSIS FOR MAGNETO-PLASTIC INSTABILITY OF FERROMAGNETIC BEAM-PLATES WITH GEOMETRIC IMPERFECTION

The magneto-plastic instability of a ferromagnetic beam-type plate with simple supports and small initial imperfection is analytically investigated in this paper for that the plastic deformation of the plate with a linear-strain hardening relation is co…