夹杂物处疲劳裂纹萌生寿命的多尺度预测方法

项目名称： 夹杂物处疲劳裂纹萌生寿命的多尺度预测方法

项目编号： No.51475396

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 机械、仪表工业

项目作者： 陈立杰

作者单位： 厦门大学

项目金额： 84万元

中文摘要： 高温合金等材料中不可避免地存在夹杂物，它是疲劳裂纹萌生的择优位置，对夹杂物处疲劳裂纹萌生的预测是一个极富挑战的问题。本项目以多晶镍基高温合金如GH4145为研究对象，结合先进的集成化多尺度建模方法与电子背散射衍射等实验技术，首次研究碳化物处疲劳裂纹萌生的寿命。 　　针对空间多尺度问题，首先基于第一性原理从头计算，依据塑性形变的能量平衡原理建立疲劳裂纹萌生准则，再集中各尺度方法优势，建立基于能量的疲劳裂纹萌生寿命的多尺度预测模型，并进行高温疲劳试验验证。通过该模型研究，将阐明碳化物夹杂的各种开裂机制对疲劳裂纹萌生的影响，量化材料各组分形变能垒与相对强度，明确夹杂物在非均匀变形和应变局部化中的作用，更准确预测疲劳裂纹萌生寿命。 　　本研究中夹杂物失效预测方法亦可用于钛合金、铝合金等失效研究中，将为预测损伤演化、疲劳裂纹萌生、可靠寿命设计提供集成化基础，对新材料设计与开发提供新的设计思想。

中文关键词： 多尺度模拟；疲劳裂纹萌生；寿命预测；碳化物夹杂；相对强度

英文摘要： Inclusions are present in structural alloys, including steel, aluminum, titanium, nickel-based superalloys, etc. These inclusions are a principal site for crack initiation in engineering alloys. Hence, solving prediction of fatigue crack initiation life in alloys remains a pressing issue to the material science and engineering. In this proposal, we select polycrystalline Ni-based superalloy GH4145 containing relatively stable carbides M23C6 as the research object. With the combination of up-to-date modeling method, integrated multi-scale modeling, and advanced experimental technique (electron back-scatter diffraction analysis), we perform detailed study for the fatigue crack initiation life prediction. 　 For spacial multi-scale simulations, we plan to establish an energy-based integrated multi-scale life prediction method for crack initiation, which starts from first principles based on density functional theory (ab inito calculation). According to energy balance method of plastic deformation, criterion for fatigue crack initiation can be established.Then based on the atomistic scale results, connections with upper scale models are made to integrate the advantages of different scale methods and predict fatigue crack initiation life. Finally we perform fatigue tests at elevated temperature to confirm the capability of the integrated multi-scale analysis for fatigue life prediction based on crack initiated from inclusions. On theretical understanding, based on our model, we will clarify the influence of different cracking mechanisms of carbides on fatigue crack initiation, quantify the energy barriers to deformation and relative strength of each constituent of the material, and understand the role of inclusions on heterogeneous deformation and strain localization so as to predict fatigue crack initiation life more precisely. The techniques used in this project are common to inclusion failures across alloys and can be used to characterize inclusion failures of Al alloys, Ti alloys, powder metals, etc. So relevant techniques are with hopeful application prospect. This spacial multi-scale method serves as an integrated foundation to predict damage evolution, fatigue crack initiation, and the minimal reliable safe life, and therefore provides a design idea for new material design and development.

英文关键词： multi-scale simulation;fatigue crack initiation;life prediction;carbide inclusions;relative strength