基于非线性阻尼识别的螺栓连接检测技术

Technology for detecting bolted joints based on nonlinear damping identification

螺栓连接质量是影响机械结构装配质量的关键,研究快捷、有效的检测技术具有重要意义。根据能量守恒定律,推导出螺栓连接接触面非线性阻尼识别公式。基于系统动力学特性与经验模态分解(EMD)相结合的方法,确定出用于阻尼识别的系统敏感固有频率。以L型梁为研究对象进行实验,并利用希尔伯特变换方法和建立的非线性阻尼识别公式,得到系统的黏性阻尼比以及非线性阻尼比。研究表明,螺栓扭矩的变化对系统固有频率影响较小,而对系统阻尼的影响显著,尤其是对黏性阻尼比的影响较明显;当螺栓发生松动时系统的黏性阻尼比会发生明显的非线性变化,即由0.1225跃升至0.2587,相对增加了111.18%,从而验证了基于非线性阻尼变化检测螺栓连接质量的有效性。

Bolt connection quality is the key factor to affect the mechanical structure assembly quality,so it’s important to explore a fast and effective technique for its detection.The definition of high order nonlinear damping ratio was proposed,and a formula for the identification of nonlinear damping on the bolted joints contact surfaces was provided according to the energy conservation law.The dynamic characteristics of the system were obtained through modal experiments,combined with which the empirical mode decomposition(EMD)was used to determine the frequency sensitive to the torsional vibration of the system.Impact response experiments of L-beams under different torques were carried out.The viscous damping ratio and nonlinear damping ratio of the system were identified by using the Hilbert transform and the established nonlinear damping identification formula.The results show that the change of bolt torque has a little effect on the natural frequencies of the system,but has obvious influence on the damping of the system,especially the viscous damping ratio.When the bolt is loose,the viscous damping ratio of the system will change significantly,that is,from 0.1225 to 0.2587,a relative increase of 111.18%,which verifies the effectiveness of the method proposed.