虚拟功能梯度材料表征栓接结合部动态特性

为提高结合部的建模精度,提出虚拟功能梯度材料法表征栓接结合部的动态特性。首先,利用有限元法仿真栓接结合部在不同预紧力和不同接触区域的受力情况,采用多项式函数拟合出栓接结合部的接触压力分布模型,并根据压力分布规律,提出虚拟材料层的划分准则。然后,探索虚拟功能梯度材料属性(弹性模量、剪切模量、泊松比、密度以及虚拟层厚度)与有效接触区域内接触半径的关联关系,建立栓接结合部虚拟功能梯度材料模型。最终,通过具体算例将栓接结合部划分为2层、3层和4层,并依次确定各层虚拟材料的属性,利用ANSYS有限元中的APDL语言将虚拟功能梯度材料模型与连接结构耦合,建立考虑栓接结合部动态特性的整体结构有限元模型,并进行动态响应分析,将获得整体结构的频响函数与模态试验数据对比分析,发现4层虚拟材料明显与试验结果最为接近,最大误差出现在第2阶固有频率处,误差仅为2.4%。

An Analytical Approach for Assessing the Collapse Strength of an Unbonded Flexible Pipe

This paper presents an analytical scheme for predicting the collapse strength of a flexible pipe, which considers the structural interaction between relevant layers. The analytical results were compared with a FEA model and a number of test data, and showed reasonably good agreement. The theoretical analysis showed that the pressure armor layer enhanced the strength of the carcass against buckling, though the barrier weakened this effect. The collapse strength of pipe was influenced by many factors such as the inner radius of the pipe, the thickness of the layers and the mechanical properties of the materials. For example, an increase in the thickness of the barrier will increase contact pressure and in turn reduce the critical pressure.

Effects of Temperature and Centrifugal Force on Fretting Wear of Contact Interface of Face Gear

Taking the typical face gear connection structure of the combined rotor as the research object,this paper studies the distribution rules of the contact state,contact stress and slip distance of the contact tooth surface of face gear under different centrifugal force and temperature conditions by using the finite element method,in order to improve the reliability of face gear connection structure.And the influence of centrifugal force and temperature on the maximum wear depth of the tooth surface is studied based on the fretting wear model proposed by McColl.Results show that:(1)The external diameter has an opening phenomenon on the contact surface of the face gear under the centrifugal effect,which reduces the load-bearing area;(2)The contact stress at the inner root of the face gear is the largest and the wear is the most serious;(3)The temperature field causes the contact surface to be thermally expanded,resulting in the large uneven deformation,and the tooth surface appears drum-shape;(4)The maximum contact stress and the maximum wear depth occur in the middle of the tooth root;(5)As the temperature increases,the maximum wear depth of the tooth surface increases significantly.Consequently,reducing temperature of the combined rotor plays an important role in effectively reducing the wear of the face gear and improving the connection life of face gear connection structure.

压裂用封隔器高压胶筒的密封理论研究

针对当前封隔器胶筒密封设计基于模拟仿真和试验研究,没有一套切实可行的理论方法指导的现状,提出了高压压裂用封隔器胶筒的密封理论框架和体系。在深入探索胶筒的密封机理和失效机理的基础上,建立了封隔器胶筒密封处的接触应力分布理论模型,并确立了封隔器胶筒的接触应力准则、强度准则和变形准则,并通过实例的模拟试验验证了该理论的有效性。该理论可为高压封隔器胶筒的设计提供理论依据和方法指导,使胶筒密封的设计成为一个可操作的过程,对提高封隔器胶筒的工作性能和可靠性具有重要的意义。