【作者】 林祥宇；

【导师】 荆洪阳；

【作者基本信息】 天津大学 ， 材料加工工程， 2008， 硕士

【摘要】 目前,在航天、航空等许多工业领域,各种热涂层技术已经广泛用于提高机械构件的性能,延长其使用寿命。而涂层与母材基体的完整性是构件安全的关键,涂层的结合强度成为评价涂层适用性的重要标准之一。本文从探讨涂层/基体系统界面结构完整性评定的方法出发,对传统断裂参量J积分在界面断裂问题中应用,以及基于局部法评定FeCrAl /Q345涂层系统的界面断裂行为等问题进行了研究。本文介绍了脆性材料断裂的统计学原理,而后阐述介绍了局部法分析界面脆性断裂裂纹扩展问题的理论。分别采用三点弯曲法和四点弯曲法,测量带预制疲劳裂纹试样和带缺口试样的FeCrAl/Q345涂层系统的界面结合强度(界面临界断裂载荷Pc),为断裂力学实验分析提供实验数据。利用ABAQUS有限元分析软件,计算了八个带预制疲劳裂纹的试样发生界面断裂时的J积分值,发现八个弯曲试样发生界面断裂时的J积分值分散很大。表明使用传统单一断裂参量J积分来评价界面断裂是不适合的。利用两种形式弯曲试样的界面结合强度的实验数据,将局部法用于分析FeCrAl /Q345涂层系统的界面断裂行为对试样几何形式和加载方式的依赖性。并且基于局部法预测了界面的断裂行为。研究发现不同几何形式的试样在发生界面断裂时,在相同断裂概率下其威布尔应力基本上相同,并且基于预制裂纹试样的试验结果成功的预测了一种缺口试样断裂数据的分布。总之,基于局部法可以显著地减小断裂数据对几何形式和加载方式的依赖性,说明局部法可以用来描述双材料界面的断裂行为,并应用于对界面的完整性评定中。在基体Q345钢成分相同情况下,对比FeCrAl/Q345涂层系统的断裂失效概率与LX88A/Q345涂层系统断裂失效概率,发现FeCrAl/Q345涂层系统的断裂失效概率要比LX88A/Q345涂层系统断裂失效概率高。更多还原

【Abstract】 At present, in astronautics, aviation and so many industry domains, each kind of thermal spraying coating technology has already been widely used in enhancing the performance of the mechanical components and lengthened their service life. The integrity of coating/substrate system is critical for the components’security, and the union intensity of coatings has become one of many important standards in the applicability of coatings. For the purpose of seeking a method to evaluate the integrity of coating/substrate system interface, the applicability of traditional fracture parameter J integral in interface fracture problem and evaluation of interface fracture behavior of FeCrAl coating/Q345 steel substrate based on the local approach have been studied in this paper.In this paper, the statistics theory of brittle material fracture is presented. And the local approach of interface crack is shown.The 3-point bend test has been used to measure interface bond intensity(critical fracture load Pc) of FeCrAl coating/Q345 steel substrate system with prefabricated fatigue crack, and the 4-point bend test had been used to measure interface bond intensity(critical fracture load Pc) of FeCrAl coating/Q345 steel substrate system with prefabricated notch. These experiments provide experiment data for fracture mechanics analysis.ABAQUS software is used in finite element analysis. The JC values of the eight C3PB specimens when the interface fracture occurs are Calculation, and it’s seen that the JC values of the eight specimens with prefabricated fatigue crack are very dispersive. It’s shown that JC can not be used as the single fracture parameter to evaluate the interface fracture behavior.With experiment data of interface bond intensity of two bend form specimens, the local approach is used to analyze geometry and load dependence of FeCrAl coating/Q345 steel substrate system for interface fracture behavior. In addition, the local approach is used to predict the interface fracture behavior. It is found that the Weibull stress(σW) for all specimen geometries almost are identical under the same fracture probability when the interface fracture initiation occurs for different specimen geometries. Moreover, the interface fracture behavior of one type of specimens with notch has been predicted from the test results of pre-crack specimens based on the local approach for interface brittle fracture, and the predicted distribution of the critical load for the notched specimens gives a good agreement with the test results. In a word, the geometry dependence of the interface brittle fracture toughness data can be reduced through the local approach’s application. It showed that the local approach not only can be used to describe the interface fracture behavior, but also can be used in the integrity evaluation for interface between different materials.In the case of the same constitution of Q345 steel substrate, the fracture failure probability of FeCrAl/Q345 coating system is compared with that of LX88A/Q345 coating system. It’s found that the fracture failure probability of FeCrAl/Q345 coating system is higher than that of LX88A/Q345 coating system.更多还原