强热流环境下涂层屈曲失稳规律及机理研究

As one of long-standing core challenges, the thermally induced buckling instability has been limiting coating application in high temperature environment. The exploration of formation pattern and underlying mechanism of coating instability modes is of much importance for both academic and practical purposes. The driving force for the thermally induced coating instability is not only dependent upon inherent mismatch of physical and mechanical properties between the coating and substrate, but also closely related to the transient effects of thermal loads. In this proposal, the experimental investigation on coating buckling instability will be carried out under high heat flux and dominant parameters and relevant influencing laws will be identified, which dictate typical buckling modes such as blistering and wrinkling. Based on the principle of least energy and theory of interfacial fracture mechanics, a reasonable prediction model will be developed to reveal underlying physical mechanism of corresponding buckling mode formation, with an effective approach figured out to tune characteristic parameters. The cohesive zone model will be adopted to simulate the mechanical behavior of interface of coating and substrate. Also considered are coating plasticity and the transient effects of thermal loads. The similarity theory and dimensional analysis method will be used to establish the general relationship between various dimensionless parameters. A phase diagram will be finally constructed for coating buckling mode selection under high heat flux. The result will provide theoretical basis and technological support for the “strengthening and toughening” design idea and for the surface morphology tuning technique.

涂层的热致屈曲失稳问题，一直是制约其在高温环境下应用的核心难题之一。探索其热致屈曲失稳模式的规律及机理具有重要的学术意义及应用价值。涂层的热致屈曲驱动力不仅依赖于涂层与基体材料在物理、力学性能方面的本征失配，也与热载荷的瞬态效应密切相关。本项目拟通过对涂层在强热流作用下屈曲失稳行为的试验研究，深入探讨与之相关的典型屈曲模式(鼓泡和皱曲)的主控因素及其影响规律。基于最小能量原理和界面断裂力学理论，提出合适的理论预测模型，揭示相应屈曲失稳模式形成的物理机制，进而提出调控其特征参数的有效措施。研究思路上采用内聚区模型模拟涂层/基底的界面力学行为，并考虑涂层的塑性变形和热载荷的瞬态效应。基于相似理论和量纲分析方法，建立各类无量纲参数之间的普遍规律，进而确定涂层在强热流环境下屈曲失稳模式的转换相图。本项目的研究结果将为相关涂层的强韧化设计及表面形貌调控方法提供理论依据与技术支持。

涂层的热致屈曲失稳问题，是制约其在高温环境下应用的核心难题之一。探索涂层热致屈曲失稳的规律及机理具有重要的学术意义及应用价值。本项目结合实验研究、理论建模与数值模拟，建立了涂层热致皱曲和鼓泡层裂失稳模式的理论模型，得到了典型屈曲模式(鼓泡和皱曲)的主控因素及其影响规律。提出了理论预测模型，揭示相关屈曲失稳模式形成的物理机制。.研究了涂层/基体系统在不同目标温度和不同热载速率下的热致皱曲行为及皱曲波长的影响因素和影响规律。考虑涂层/基体系统的初始界面裂纹，得到了涂层在两种不同屈曲模式(皱曲和鼓泡层裂)情形下的临界应变(应力)，从而量化界面裂纹尺寸对承压涂层屈曲模式的影响。采用半解析方法确定了界面裂纹的过渡尺寸，建立并表征了基于界面裂纹尺寸和压缩应变的涂层屈曲失稳模式转换相图。主要研究结果表明:(a)初始界面裂纹尺寸和涂层/基体失配参数是影响受压涂层屈曲失效模式的主要因素;(b)在软基体及短界面裂纹情形，受压涂层倾向于产生皱曲模式；而对于硬基体和长界面裂纹情形下，受压涂层容易诱导鼓泡层裂模式;(c)给定涂层/基体系统，存在过渡界面裂纹尺寸值，使得受压涂层同时出现鼓泡层裂及皱曲两种屈曲模式。研究结果有望为相关涂层的强韧化设计及表面形貌调控方法提供理论依据与技术支持。