基于非线性本构关系的软管编织增强层等效刚度修正方法研究

Equivalent Stiffness Modification for Metal Wire Braid Reinforced Hose Based on Nonlinear Constitutive Relation

基于Hachemi提出的金属编织层本构理论以及拉伸实验的研究方法,进行了不同尺寸金属编织软管的拉伸实验.发现金属编织层在拉伸时会出现强烈的结构非线性,而该理论不能在非线性段与实验结果相吻合.提出了对理论中编织层刚度矩阵修正方法,将金属纤维间交叠产生的接触等效地转化为"修正基体",独立于金属纤维自身产生的刚度.同时,结合编织角在实验中呈现的变化趋势,提出管状金属编织层在等位移拉伸荷载下编织角呈线性变化的假设.这与Hachemi的假设恰好相反.Hachemi认为编织层受拉时,编织角减小到一定程度则会发生锁定现象.而实验证明了编织角并不会发生锁定.且直到编织层破坏为止,编织角变化的趋势基本呈线性.还提出了修正编织角变化的加速系数k,通过金属纤维间的侧向接触解释了实验与数值仿真结果中,力位移曲线与编织角变化曲线不能同时吻合的力学机理.

An experiment was conducted and several modifications were put forward, based on the method proposed in Hachemi＇s research of metal wire braid reinforced hose. Theoretical results based on the constitutive theory were found not to agree with the experimental results, while the experiment demonstrated appreciably nonlinear mechanical behaviors. A ＂modified matrix＂ was introduced. Detaching inter-wire contacts from wire elongation was seldom considered before. A hypothesis that is opposite to Hachemi＇s was proposed： the hose＇s braid angle decreases linearly, instead of being locked at a certain degree, while being applied displacement load with constant loading rate. Consequently a modified accelerating coefficient k was introduced such that the linearity in force-displacement curve could be matched by accelerating the decrease of braid angle. Lateral contact was considered to be the factor of excessively decreased braid angle when the calculated curve perfectly meets the experimental one, with suitable k.