封隔器压缩式胶筒剪切流变特性探讨

Discussion on Shear Rheological Properties of Compressed Packing Rubber during Axial Compressing

根据流变力学理论,建立了井壁约束条件下封隔器胶筒的剪切应力松弛和蠕变预测方程,通过外推法反演得到呈指数分布的材料参数方程,指出积分导数-指数在时间上具有等效性;提出了基于最小二乘法原理的封隔器胶筒应力松弛试验数据的拟合作法;计算了封隔器胶筒应力松弛模拟试验预加的初始剪应力及剪应变。分析结果表明:封隔器胶筒的应力松弛现象和蠕变效应直接影响封隔器胶筒元件的尺寸稳定性及密封性能;封隔器胶筒的剪应力随时间的增加而衰减,直至达到稳态水平而不再衰减;封隔器胶筒的剪应变随时间的增加而增大,出现快速上升和缓慢平稳2个阶段。较好地描述了井壁约束条件下封隔器胶筒的流变特性。

According to the rheological mechanical theory, shear stress relaxation and creep prediction equation of packer rubber under constraint condition of borehole wall were established, material parameter equation with exponential distribution was obtained by extrapolation method, and equivalence of the integral derivative-exponent with time was pointed out. Based on the least squares principle, simulating method of stress relaxation experimental data of packer rubber was put forward. Additive initial shear stress and shear strain of stress relaxation simulation experiment of packer rubber were calculated. Analysis results show that stress relaxation phenomenon and creep effect of packer rubber directly influence size stability and sealing performance of packer rubber element;shear stress of packer rubber attenuates as the time increases, until it reaches the level of steady state and no longer decays;shear strain of packer rubber increases as the time increases,two stages of rapidly rising and slow balance were present. Rheological properties of packer rubber under constraint condition of borehole wall can be described accurately with exponential distribution