【作者】 张威；

【导师】 刘震涛；

【作者基本信息】 浙江大学 ， 动力工程及工程热物理， 2025， 博士

【副题名】海水泵多轴疲劳问题研究

【摘要】 船舶辅机柴油机发电机组包含水泵、油泵、启动电机等关键辅件,该类辅件的可靠性直接影响船舶动力系统的持续稳定运行能力。对于水泵类辅件,在以往研究中常针对泵轴、叶轮等关键运动部件开展强度考核,而在实际试验测试中却发现泵壳及端面法兰同样存在疲劳失效隐患:其在陆上考核通过,安装上船运行不久却发生疲劳失效。其原因主要是陆上试验台架未综合施加振动、摇荡载荷,试验应力与水泵实际工作应力、故障激发因素不一致。因此,本研究选取悬臂式海水泵作为典型研究对象,其在复杂服役环境中长期承受高频振动、低频摇荡的耦合载荷作用,其动态响应特性、疲劳寿命显著区别于只承受振动或只承受摇荡的单一载荷工况。目前技术不具备复现这种高低频耦合载荷的模拟试验能力,现有疲劳寿命预测模型处理振动、摇荡耦合载荷引发的多轴疲劳问题时存在一定误差。因此,亟需发展新的模拟试验技术、修正现有寿命预测模型,以解决船载柴油机辅件在复杂服役环境中的可靠性验证问题。为解决上述问题,本论文从耦合载荷下海水泵的简化及动态响应分析、模拟试验系统关键技术研究及应用、现有寿命预测模型在耦合载荷下的适用性评价和修正三个方面展开,针对悬臂式海水泵泵壳及连接端面法兰的疲劳失效问题,结合理论分析、数值仿真、试验研究与模型构建等方法,系统地开展了研究,提出了新的试验技术与修正的寿命预测方法,主要内容如下:(1)海水泵-悬臂结构的等效简化以及高低频耦合载荷下结构动态响应研究。通过保持结构关键区域应力场分布的一致性,建立海水泵等效简化结构——悬臂结构,结合模态动力学分析,研究了高低频耦合载荷对结构应力分布和时域变化规律的影响。研究表明,高频振动与低频摇荡载荷的耦合会引发显著的非比例载荷特性,使得结构在振动基频的基础上形成低频包络,应变极值显著增大。研究为复杂载荷条件下的疲劳行为分析提供了数据支持,奠定了寿命预测的基础。(2)振动摇荡一体化模拟试验技术研究及应用。为真实复现高低频耦合载荷,自主开发并搭建了可以模拟柴油机振动环境和海洋摇荡环境的振动摇荡一体化试验台,实现了高频振动与低频摇荡的精准解耦与叠加。该试验台基于船载环境实测数据与GJB4000-2000标准,各轴采取独立控制策略,通过无迹卡尔曼滤波结合PID闭环控制算法,确保激励信号的准确性与稳定性。开展试验系统的应用,通过悬臂结构样件的模拟试验发现,结构的应变分布状态和时域变化规律与数值分析结果吻合度较高,进一步证明了试验台对耦合载荷的重现能力与数值计算模型的准确性。此外,通过模拟试验获取了高周疲劳数据,为模型验证与寿命预测优化奠定了基础。(3)现有多轴疲劳寿命预测模型在振动、摇荡耦合载荷下的适用性研究与模型修正。首先,对经典等效应力应变法和临界平面法在耦合载荷下的适用性进行了综合评价。然后,针对现有疲劳寿命模型在高低频耦合载荷条件下的局限性,本文基于临界平面法提出了时域平均修正与临界距离分布修正的改进寿命预测模型。修正后的模型通过引入时域修正因子,考虑了高低频载荷叠加效应,并结合临界距离理论优化了危险点的损伤参数提取方法。试验验证结果表明,修正后的寿命模型预测相对误差更接近零值,误差中位数(绝对值)从0.155降低至0.0035,预测精度得到了显著提升。修正的模型为复杂工况下船载柴油机辅件的疲劳寿命分析提供了理论依据,展现了极强的工程实践潜力。本研究为以悬臂式海水泵为代表的柴油机典型辅件的可靠性考核与设计优化提供了科学支撑,并为振动、摇荡耦合载荷条件下的多轴疲劳分析提供了理论依据与技术路径。未来,该研究成果在船载柴油机辅件设计与寿命评估中具有重要的工程应用价值。更多还原

【Abstract】 The auxiliary diesel generator sets on ships include critical accessories such as water pumps,oil pumps,and starter motors,whose reliability directly affects the sustained and stable operation of the marine power system.For water pump-type accessories,previous research has primarily focused on strength assessment of key moving components such as the pump shaft and impeller.However,experimental tests have revealed that the pump housing and end-face flange are also susceptible to fatigue failure.These components may pass land-based qualification tests but fail shortly after being installed onboard.The primary reason lies in the limitations of land-based test benches,which do not account for the combined effects of vibration and shipborne rocking loads.As a result,the applied test stresses differ significantly from the actual operating stresses and failure-inducing conditions experienced at sea.Therefore,this study selects a cantilever-type seawater pump as a representative object,which,in its complex service environment,is subjected to coupled high-frequency vibration and low-frequency rocking loads over extended periods.Its dynamic response characteristics and fatigue life are significantly different from those under single-loading conditions involving only vibration or only rocking.Currently,test technologies lack the capability to accurately reproduce such coupled high–low frequency loading scenarios,and existing fatigue life prediction models exhibit noticeable deviations when addressing multi-axial fatigue induced by the interaction of vibration and rocking loads.Therefore,it is imperative to develop new experimental simulation technologies and improve existing life prediction models to effectively address the reliability verification challenges of shipborne diesel engine accessories operating in complex marine environments.To address the aforementioned issues,this dissertation conducts a systematic investigation from three key perspectives:the simplification and dynamic response analysis of the seawater pump under coupled loads,the research and application of critical technologies for a simulation testing system,and the evaluation and modification of existing fatigue life prediction models under coupled loading conditions.Focusing on the fatigue failure issues of the pump housing and end-face flange of a cantilever-type seawater pump,this study integrates theoretical analysis,numerical simulation,experimental research,and model development.New experimental techniques and modified life prediction methods are proposed.The main contents are as follows:(1)Equivalent Simplification of the Seawater Pump-Cantilever Structure and Dynamic Response Analysis Under Coupled High-and Low-Frequency Loads.A finite element model of an equivalent simplified seawater pump structure(cantilever structure)was developed to investigate the effects of coupled high-and low-frequency loads on structural stress distribution and time-domain response patterns through modal dynamic analysis.The study reveals that the coupling of high-frequency vibration and low-frequency rocking loads induces significant non-proportional loading characteristics,forming a low-frequency envelope superimposed on the fundamental vibration frequency,which significantly amplifies peak strain values.These findings provide crucial data for fatigue behavior analysis under complex loading conditions and lay the foundation for fatigue life prediction.(2)Development and Application of an Integrated Vibration-Rocking Simulation Testing Technique.To accurately reproduce coupled high-and low-frequency loads,this study independently developed and constructed an integrated vibration-rocking test platform capable of simulating both diesel engine vibration environments and marine rocking environments.This platform enables precise decoupling and superposition of high-frequency vibration and low-frequency rocking loads.Designed based on real-world shipborne environmental measurements and the GJB4000-2000 standard,the platform adopts independent control strategies for each axis.By combining an Unscented Kalman Filter with a PID closed-loop control algorithm,the accuracy and stability of excitation signals are ensured.The application of the testing system demonstrated that the strain distribution and time-domain response patterns obtained from cantilever structure specimens closely matched the numerical analysis results,further verifying the platform’s ability to replicate coupled loads and the accuracy of numerical computational models.Additionally,high-cycle fatigue data obtained from the simulation tests provide a critical foundation for model validation and fatigue life prediction optimization.(3)Evaluation and Correction of Existing Multi-Axial Fatigue Life Prediction Models Under Coupled Vibration-Rocking Loads.First,the applicability of classical equivalent stress-strain methods and the critical plane approach under coupled loads was comprehensively evaluated.Then,addressing the limitations of existing fatigue life models under coupled high-and low-frequency loads,this study proposed an improved fatigue life prediction model based on the critical plane approach.The refined model incorporates time-domain averaging correction and critical distance distribution correction.By introducing a time-domain correction factor,the model accounts for the superposition effects of high-and low-frequency loads,while critical distance theory is employed to optimize the extraction of damage parameters at critical points.Experimental validation results indicate that the revised model significantly improves prediction accuracy,with the absolute value of median error reduced from 0.155 to 0.0035,achieving a higher level of precision.The refined model provides a theoretical foundation for fatigue life analysis of shipborne diesel auxiliary components under complex service conditions and demonstrates strong potential for extensive engineering applications.This study provides scientific support for the reliability assessment and design optimization of typical diesel auxiliary components,using the cantilever-type seawater pump as an example.Additionally,it establishes a theoretical foundation and technical framework for multi-axial fatigue analysis under coupled vibration-rocking loads.In the future,the research outcomes are expected to have significant engineering applications in the design and lifespan evaluation of shipborne diesel auxiliary components.更多还原