U形无加强波纹管平面失稳判据研究

本文采用了理论分析及非线性有限元分析的方法探讨了单纯内压载荷以及内压—轴向压缩位移载荷下U形无加强波纹管平面失稳的应力判据。与实验结果的对比表明在这两种载荷下 ,U形无加强波纹管平面失稳与否主要取决于波纹管波峰、波谷以及环板中塑性区的产生与扩展。     

碟形金属波纹管的内压稳定性研究

通过有限元软件和稳定性试验研究了碟形金属波纹管的内压稳定性，有限元分析得到的波纹管临界失稳内压值与试验值接近，失稳模态与试验结果一致，说明建立的有限元模型能够较好地分析碟形波纹管的稳定性，并利用有限元分析了波纹管几何参数对其稳定性的影响。根据EJMA标准中U形波纹管临界失稳内压的计算方法，得到了碟形波纹管平面失稳和柱失稳临界失稳内压的计算公式，公式计算结果得到了有限元的验证，具有一定的工程应用价值。     

拉伸位移下平面失稳波纹管的疲劳寿命研究

对平面失稳波纹管在内压及拉伸位移共同作用下进行疲劳寿命试验研究,结果表明,波纹管发生平面失稳后,膨胀节仍可继续使用,但寿命会有降低,其寿命与波纹管的失稳程度有一定的关系,波纹管失稳越严重,产品的寿命降低越多,研究结果可为膨胀节的设计及应用提供一定的参考。     

U型波纹管膨胀节平面稳定性研究

本文介绍了计算膨胀节波纹管平面失稳临界压力有关公式，并根据极限分析原理提出了一种平面失稳临界压力计算式。文中同时分析了压力及内压与压缩位移一齐作用时的平面稳定性试验结果。     

波纹管的失稳

在管线和压力容器装置中,波纹管的失稳是可能失效的模式,这种失效有严重的后果.本文的目的是提供一套简化的、可接收的标准设计公式,用于评价波纹管的几种失效形式.这些公式考虑了柱失稳、平面失稳和由初始的侧向偏移引起的失稳.     

膨胀节的压力试验和波纹管的失稳试验

通过对最新版本相关国外标准和有关文献的分析、提出波纹管失稳试验时波纹管应固定于自由长度状态，膨胀节水压试验时试验压力不应使波纹管产生屈服或失稳。     

波纹管在扭转载荷下的稳定性分析

采用非线性有限元分析了波纹管在扭转载荷下的失稳模态和临界失衡扭矩，讨论了各参数对失稳的影响，与线性分析得到的结果进行比较，并尝试用弧长法模拟波纹管的后屈曲过程。     

内外压平衡式波纹膨胀节稳定性分析

内外压平衡式波纹膨胀节的稳定性在管道工程领域属于关键技术指标,而且是研究难点。本文首先讨论了在内压和外压分别作用下的失稳问题,通过用未发生位移的无加强U形波纹管柱失稳和平面失稳极限设计内压的计算公式,得出发生失稳的临界极限值,从而进一步得出在内外压共同作用下平衡式波纹膨胀节有可能发生何种失稳现象的结论。     

船用承压金属软管平面失稳性能分析

在ANSYS中建立金属软管的有限元模型,对船用承压金属软管和波纹管的平面失稳性能进行了仿真分析,将其结果与试验结果进行对比,证明了有限元模型的可靠性。对船用金属软管在零位移、拉伸位移和压缩位移状态下的的平面失稳性能进行了有限元仿真分析研究。研究成果对提高金属软管的性能和船舶管路系统的质量以及金属软管结构的优化设计提供了非常有实用价值的参考。     

用非线性有限元分析波纹管的扭转稳定性

波纹管行业内较少有人从事研究波纹管的扭转稳定性问题。本文利用非线性有限元的理论，考虑了材料的非线性，几何非线性，大变形，大应变，结合有限元程序Ansys计算分析了波纹管本身的几何参数的变化以及在一些综合载荷作用下的失稳扭矩的变化规律，为波纹管生产厂商和设计者提供了参考和借鉴。     

波纹管在外压-拉伸条件下的稳定性研究

对波纹管在拉伸条件下的外压稳定性进行了试验研究和非线性有限元分析 ,结果表明拉伸位移对波纹管的外压稳定性有不利影响 ,失稳是由于某一波纹局部区域的大量塑性变形而产生的。同时指出 ,对于大口径外压波纹管 ,周向应力对波纹管强度的影响超过了子午向应力     

Dynamic instability analysis of stiffened shell panels subjected to partial edge loading along the edges

The dynamic instability characteristics of stiffened shell panels subjected to partial in-plane harmonic edge loading are investigated in this paper. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the shell panels and the stiffeners, respectively. As the usual formulation of degenerated beam element is found to overestimate the torsional rigidity, an attempt has been made to reformulate it in an efficient manner. Moreover, the new formulation for the beam element requires five degrees of freedom per node as that of shell element. The method of Hill's infinite determinant is applied to analyze the dynamic instability regions. Numerical results are presented through convergence and comparison with the published results from the literature. The effects of parameters like loading type and shell geometry are considered in the dynamic instability analysis of stiffened panels subjected to non-uniform in-plane harmonic loads along the boundaries. The tension buckling aspect of the stiffened panels are also considered and the dynamic stability behavior due to tensile in-plane edge loading is studied for the concentrated load.     

Dynamic stability of ferromagnetic plate under transverse magnetic field and in-plane periodic compression

The dynamic stability of a soft ferromagnetic rectangular and simply supported plate immersed in an applied transverse magnetic field, as well as subjected to an in-plane periodic compression is presented in this paper. The fundamental equations involving magnetoelastic interaction and magnetic damping effect for the ferromagnetic plate are developed. In the theoretical model, the expression of induced magnetic force is based on a generalized magnetoelastic variational model, and the magnetic damping is due to the Lorentz body force arising from eddy current in the ferromagnetic material. By means of a linearized magnetoelastic theory and perturbation technique, the motion equation of the ferromagnetic plate is reduced to a damped Mathieu's equation and solved. The dynamic stability of the magnetoelastic system without in-plane compression is theoretically analyzed first, to show that there exist two stable states: magnetic damped stable oscillation, and over-damped asymptotically stable motion before static divergence instability of the ferromagnetic plate occurs. The dynamic instability and stability regions for the parametric excitation of the ferromagnetic plate due to the harmonically excited in-plane compression are obtained next. The effects of magnetic damping and excitation frequency of the in-plane periodic compression on the stability regions are discussed in detail.     

Friction-induced vibration of an elastic slider on a vibrating disc

The in-plane vibration of a slider-mass which is driven around the surface of a flexible disc, and the transverse vibration of the disc, are investigated. The disc is taken to be an elastic annular plate and the slider has flexibility and damping in the circumferential (in-plane) and transverse directions. The static friction coefficient is assumed to be higher than the dynamic friction. As a result of the friction force acting between the disc and the slider system, the slider will oscillate in the stick-slip mode in the plane of the disc. The transverse vibration induced by the slider will change the normal force on the disc, which in turn will change the in-plane oscillation of the slider. A numerical method is used to solve the two coupled equations of the motion. Results indicate that normal pressure and rotating speed can drive the system into instability. The rigidity and damping of the disc and transverse stiffness and damping of the slider tend to suppress the vibrations. The in-plane stiffness and damping of the slider do not always have a stabilizing effect. The motivation of this work is the understanding of instability and squeal in physical systems such as car brake discs where there are vibrations induced by non-smooth dry-friction forces.     

Long-wave buckling of elastic square honeycombs subject to in-plane biaxial compression

In this study, long-wave and short-wave buckling of elastic square honeycombs subject to in-plane biaxial compression are analyzed using a two-scale theory of the updated Lagrangian type. By taking cell aggregates to be periodic units, the bifurcation and post-bifurcation behavior are analyzed so that the dependence of buckling stress on periodic length can be discussed. It is shown that buckling stress decreases as periodic length increases, and that very-long-wave buckling occurs just after the onset of macroscopic instability if the periodic length is sufficiently long. Then, a simple formula to evaluate the very-long-wave buckling stress under in-plane biaxial compression is derived by exploring the macroscopic instability condition in the light of the two-scale analysis. The resulting formula is verified using an energy method.     

负压或真空条件下Ω形波纹管的计算研究

Ω形波纹管通常用于高压场合,但在许多实际应用中需要Ω形波纹管按多工况设计,既要承受较高的内压,又要承受负压或真空。EJMA标准提供了Ω形波纹管承受内压时的计算方法,但该标准明确说明受负压的Ω形波纹管不包含在标准中。目前国际上的其他波纹管膨胀节的设计标准和规范也均未涉及受负压的Ω形波纹管的计算。对此进行了分析研究并对部分结果通过有限元分析进行验证,提出了受负压或真空的Ω形波纹管的推荐计算方法。     

超高压阀门波纹管的研制

目前国内超高压阀门波纹管的设计还无统一的设计方法,采用有限元法为基础对公称压力42MPa(2500LB)阀门波纹管进行初始设计能够降低研发成本和周期.通过工程试验检测证明采用有限元法对波纹管的设计研发具有实际指导意义.该波纹管的设计方法涉及材料选型到波纹管参数确定及定型的全过程,对超高压阀门波纹管的设计具有通用性.     

成型角对焊接金属波纹管性能影响的试验研究

本文通过对不同成型角波纹管的压缩变形和弹力松驰性能的测定,研究了成型角对焊接波纹管性能的影响,确定了机械密封用焊接金属波纹管成型角的最佳范围,为优化波纹管的工程设计提供了参考。     

温度影响下汽车波纹管疲劳分析

从汽车波纹管的工作环境出发,充分考虑温度影响下材料的非线性特性,对波纹管进行了疲劳特性分析。首先,根据波纹管疲劳试验要求设置模型中的边界条件;然后从考虑屈服强度变化和不考虑屈服强度变化两种情况对波纹管危险位置的应力进行研究,找出温度变化对波纹管应力影响的特点;最后,在应力分析结果的基础上,采用局部应力应变法对波纹管进行疲劳寿命分析,得到不同温度阶段下的波纹管的疲劳寿命,并从中得出温度变化对波纹管疲劳的影响特点。