黏接结构在扭转循环载荷下力学行为的试验与理论研究

Testing and Theoretical Investigation of the Mechanical Behavior of Adhesively Bonded Butt Joints Under Cyclic Torsional Loading

在应变控制的试验条件下,对圆柱形中空对接试件进行了扭转循环加载的试验,分析了平均剪应变和剪应变幅值对黏接结构的扭转循环应力松弛和软化的影响.试验结果表明:在扭转循环载荷作用下,黏接结构的应力-应变响应曲线形状为下凹形,说明该黏接结构在扭转循环载荷下黏接界面的变形较小,且黏接结构出现了扭转循环应力松弛和循环软化情况.松弛应力在初始阶段下降较快,但随着循环次数的增加逐渐稳定.循环软化在循环加载的初始几圈较为严重,随着循环圈数的增加而减弱.平均剪应变与剪应变幅值的增大都会导致黏接结构的扭转应力松弛与循环软化加剧.此外,通过此黏接结构在扭转循环载荷作用下的力学行为试验分析,本文提出了一个可描述黏接结构在扭转循环载荷下力学响应的非线性黏-弹性循环模型,考虑了扭转循环应力松弛及循环软化的变化规律,以及平均剪应变与剪应变幅值对其力学响应的影响.通过模型计算结果与试验曲线对比,可以看出模型计算的应力-应变响应循环曲线与试验曲线重合度较好,证明该模型可以较好地描述黏接结构在不同循环载荷条件下的力学行为.此研究结果可为黏接结构及相关复合材料疲劳损伤的预测与评价提供试验和理论支持.

Cyclic torsional loading tests were conducted on adhesively bonded tubular butt joints in a strain-controlled mode,and the effects of shear strain amplitude and mean shear strain on their cyclic torsional stress relaxation and cyclic softening were investigated.The stress-strain curves of the butt joints exhibited a concave shape under cyclic loading,indicating a small deformation of the bonding interface and the occurrence of cyclic stress relaxation and cyclic softening.Cyclic relaxation stress decreased rapidly at the initial stage but became stable when the number of cycles increased.Cyclic softening was also more pronounced in the initial few cycles of cyclic loading and decreased with an increase in the number of cycles.Moreover,the increase in the mean shear strain and shear strain amplitude intensified cyclic stress relaxation and cyclic softening.According to the test observations,a nonlinear viscoelastic model was established to predict the mechanical behavior of bonded butt joints under cyclic torsional loading.This model can consider not only the cyclic stress relaxation and cyclic softening of the joints,but also the effects of mean shear strain and shear strain amplitude on its mechanical response.The stress-strain curves calculated by the model exhibited a good coincidence degree with the test results,demonstrating that the proposed model can well describe the mechanical behavior of bonded butt joints under different cyclic loading conditions.The research results can provide experimental and theoretical support for the prediction and evaluation of fatigue damage in adhesively bonded butt joints and related composites.