夹杂物处疲劳裂纹萌生寿命的多尺度预测方法

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.

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。

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等为研究对象，结合先进的集成化多尺度建模方法与DIC等先进实验技术相结合，首次研究碳化物处疲劳裂纹萌生的相关科学问题。针对空间多尺度问题，首先基于第一性原理从头计算，量化材料的各组分的相对强度;再依据塑性形变的能量平衡原理建立疲劳裂纹萌生准则;集中各尺度方法优势，建立基于能量的疲劳裂纹萌生的多尺度预测模型，并对材料的高温力学性质等进行预测研究。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。并开展合金材料的DIC裂纹扩展过程测试工作,建立材料的疲劳裂纹扩展模型...项目组已掌握了大体系结构的复杂力学性质的第一性原理建模计算方法,材料的高温性质预测方法,通过基于能量的疲劳裂纹萌生准则成功的将原子级模拟计算结果,与微细观模型进行跨尺度连接.并获得了一些材料的较可靠的疲劳裂纹扩展DIC数据...本研究中夹杂炭化物处的失效预测方法可用于高温合金、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，以及对航空结构的实时健康监测, 预示飞行的安全性具有重要的意义,应用前景可观。