激光冲击诱导690高强钢动态响应、微观结构与应力调控多尺度演变机制及其性能相关性研究

To extend service life of offshore platforms, residual Stresses of 690 High-strength Steel were adjusted by improving the bonding strength of anticorrosion coatings on pile legs. As to the problem of residual stress modulation， Multi-scale Evolving Mechanism and Its Properties of Dynamic Respond, Microstructures and Residual Stress Control on 690 High-strength Steel Induced by Laser Shock Processing was brought about as a new study. Based on elastic-plastic mechanics, dislocation theory, phase change dynamics theory, et al, in this study the Dynamic mechanical properties of 690 high-strength steel at super-high strain rates were measured and analyzed，the spreading mechanism of laser shock wave were studied, then dynamic stress-strain constitutive models of 690 high-strength steel were built. Through residual stress measurement and combined microstructure with its phase transition, the corresponding relationships and evolving rules between the distribution of residual stress and phase transition of microstructure were explored, and multi-scale mechanical model on microstructures with macroscopic stress of 690 high-strength steel were built. In the study, quantitative relationships on parameters of laser shock wave, dynamic mechanical properties, phase transition, microstructure and distribution of residual stress were analyzed and researched. Constitutive models on multi-scale analysis mechanism and property relativity studies on dynamic respond，microstructures and residual stress modulation of 690 high-strength Steel were built. Combining theoretical model with engineering practice, the problem of quantitatively controlling bonding strength of coatings interface with stress matching characteristics of 690 high-strength steel was effectively solved.

为提升海工平台使用寿命，增强桩腿防腐涂层的结合强度，对690高强钢进行应力调控。针对应力调控问题，提出激光冲击诱导高强钢动态响应、微观结构与应力调控多尺度演变机制及其性能相关性研究的新理念。课题依据弹塑性力学、位错理论、相变理论等，对超高应变率下690高强钢的动态力学性能进行测试和分析，研究激光冲击波在690高强钢中的传播机制，建立“690高强钢动态应力-应变的本构模型”；通过残余应力测试，结合690高强钢微观组织结构，探究残余应力分布与微观组织结构内在的对应关系及演变规律，建立“690高强钢微观组织与宏观应力多尺度力学模型”；对激光冲击波参数、动态力学性能、微观组织结构，残余应力之间的定量关系进行分析研究，构建“690高强钢激光冲击动态响应、微观结构与应力调控多尺度性能相关性本构模型”。将理论模型结合工程实践，有效解决690高强钢涂层界面应力匹配特性与结合强度定量调控。

为提升海工平台使用寿命，增强桩腿防腐涂层的结合强度，对690高强钢进行应力调控。开展了激光冲击诱导高强钢动态响应、微观结构与应力调控多尺度演变机制及其性能相关性研究的工作，其主要进展如下：首先，改进了激光冲击波特性测试方法与装置，探索了冲击波在690高强钢中的传播机制，建立了激光冲击加载690高强钢薄板的数值模型，研究了不同时刻应力波的状态、传播规律及残余应力分布，并通过实验验证了模型的有效性。其次，建立了激光冲击加载690高强钢表面动态应变模型，开展了表面动态应变特性的实验研究，得到了690高强钢在高应变率下的动态应力-应变关系曲线，验证了模型的准确性与可靠性；同时建立了690高强钢激光冲击波传播模型，阐明了690高强钢表面残余应力的形成机制。接着，开展了激光冲击690高强钢表面马氏体相变的实验研究和激光冲击690高强钢表面X射线衍射与微结构响应的相关性研究，在690高强钢表面的微观组织形貌像中观察到Ostwald熟化现象，并研究了激光冲击强化690高强钢薄板表面微观组织特征及诱导纳米化形成机理；同时开展了基于Ostwald熟化的激光冲击690高强钢表面位错组态分析，获得了激光冲击诱导位错的生长方式及其对纳米晶形核的影响。最后，探究了微观结构和残余应力的相关性，利用X射线衍射仪测量激光冲击微凹坑的残余应力并获得FWHM值，利用透射电镜观察冲击区域的微观组织形貌，研究了冲击次数对690高强钢表面激光冲击微造型、残余应力与表面微观组织的影响；同时将激光冲击微织构与激光冲击强化相结合，探究了复合优化工艺对690高强钢表面残余应力场的影响。