基于混沌理论的船用中速柴油机主轴承磨合质量在线定量评价方法

Aiming at the current situation that the running-in quality assessment of main bearings in marine middle-speed diesel is time consuming, complex and qualitative, this project will employ chaos theory to develop a method for online and quantitative assessment of running-in quality of main bearings. In this project, the method for extracting nonlinear contents of friction signals is proposed to obtain the information that reflects chaotic behavior of friction and wear; the characterization parameters of the nonlinear features and corresponding algorithms are investigated; the evolvement of characterization parameters and phase trajectory are studied to reveal the forming law of chaotic attractor during running-in process, and further recognize running-in state; the relationship between characterization parameters and running-in quality is studied to develop an online and quantitative assessment model of running-in quality of main bearings, further, experiments are performed to validate the model. This project will achieve quantitative characterization of running-in quality, simplify the technology of running-in quality assessment, guarantee the running-in quality, and instruct the establishment of running-in standard.

针对船用中速柴油机主轴承磨合质量评价工艺周期长、操作复杂和缺乏定量表征的现状，本项目拟运用混沌理论开展主轴承磨合质量在线定量评价方法研究。主要研究内容包括：研究摩擦信号非线性成分的提取方法，获得能反映主轴承摩擦磨损混沌行为的有效信息；提出摩擦信号非线性特征定量表征参数并研究参数的算法；通过研究主轴承磨合过程中摩擦信号表征参数和相轨迹的演化，揭示主轴承磨合过程中混沌吸引子的形成规律，进而识别磨合状态；通过研究表征参数与磨合质量的关系，提出磨合质量在线定量评价模型，并进行模型的验证试验。研究成果对磨合质量的量化表征，简化主轴承磨合质量评价工艺，保证磨合质量，以及指导磨合规范的制定具有重要意义。

当前船用柴油机主轴承的磨合质量难以实时定量评价、磨合规范制定缺乏理论依据。针对这一问题，本项目开展了如下研究：（1）研究了摩擦系统非线性成分提取时的采样长度的确定方法，发现当采样长度较小时，无标度区间长度小，分形维数计算结果不准确，区间长度随着采样长度的增大而增大，最终饱和，进而提出了采样长度的合理确定方法。（2）研究了主轴承材料的磨合条件，发现不同载荷、速度下所获得的摩擦信号的稳定性和表面质量均有显著差异，即磨合质量与磨合工况密切相关，揭示了主轴承完成磨合的条件，发现了轴承衬的磨损形式以磨粒磨损和黏着磨损为主，高速高载时出现氧化磨损。（3）研究了磨合过程中的递归演化规律，发现主轴承的磨合过程经历了突变、渐变和稳定阶段，可以描述为递归图由突变模式经漂移模式达到稳态模式的过程，实现了磨合过程的非线性描述。（4）研究了基于相轨迹和分形维数的磨合质量评价方法。发现三级磨合过程中，相轨迹呈现逐级收敛的规律，相轨迹的收敛程度越高则磨合质量越高。轴瓦表面分形维数和摩擦系数相轨迹的分形维数可用于定量评价磨合质量，两种维数越大则磨合质量越好。由于磨损表面无法在线监测，可综合使用相轨迹收敛程度、信号分形维数建立磨合质量在线定量评价系统。项目成果对指导磨合规范制定，提升船用柴油机主轴承磨合质量和可靠性，延长服役寿命具有科学意义和实际应用价值。