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Corrosion damage evolution and residual strength of corroded aluminum alloys

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Journal of University of Science and Technology Beijing 2008年第4期15卷 430-433页

作者： Youhong Zhang guozhi lv Hui Wang Bomei Si Yueliang Cheng The Second Artillery Engineering College Xi＇an 710025 China School of Aeronautics Northwest Polytechnical University Xi＇an 710072 China Naval Aeronautical Engineering Academy Qingdao Branch Qingdao 266041 China

The LY12CZ aluminum alloy specimens were corroded under the conditions of different test temperatures and exposure durations. After corrosion exposure, fatigue tests were performed. Scanning electron microscopy and optical microscope analyses on corrosion damage were carried out. The definition of surface corrosion damage ratio was provided to describe the extent of surface corrosion damage. On the basis of the measured data sets of the corrosion damage ratio, the probabilistic model of corrosion damage evolution was built. The corrosion damage decreased the fatigue life by a factor of about 1.25 to 2.38 and the prediction method of residual strength of the corroded structure was presented.

关键词： aluminum alloy corrosion damage fatigue statistical analysis residual strength

Microwave strengthens decomposition of mixed rare earth concentrate: Microwave absorption characteristics

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Journal of Rare Earths 2019年第5期37卷 541-546页

作者： Yukun Huang Ting'an Zhang Zhihe Dou guozhi lv Guihong Han Weijun Peng School of Chemical Engineering and Energy Zhengzhou University Laboratory of Special Metallurgy and Process Engineering School of Metallurgy Northeastern University

The potential application of microwave heating technology for processing the mixed rare earth concentrate was systematically investigated by analyzing the microwave absorption characteristics in this study. The complex permittivity was measured through resonant cavity perturbation method. The variations of permittivity, the loss factor, loss tangent and the penetration depth with the increasing temperature were investigated numerically. The results indicate that the permittivity increases as the temperature increases, and temperature has a pivotal effect on it. The mixed concentrate is high loss material at the temperature range from 600 to 800℃ according to theoretical analyses of loss tangent and penetration depth. The results of phase transition analysis prove that the variation of microwave absorption characteristics of mixed concentrate is caused by the changes of crystal and lattice *** reflectivity, loss factor and penetration depth of the mixed concentrate were also calculated, and the results indicate that processing the mixed concentrate by microwave heating is of high feasibility and industrial potential.

关键词： Microwave processing Microwave absorption characteristics Dielectric constant Loss tangent Mixed rare earth concentrate

Corrosion fatigue behavior of fastening hole structure and virtual crack propagation tests

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Journal of University of Science and Technology Beijing 2008年第5期15卷 585-589页

作者： Youhong Zhang Xinlong Chang guozhi lv Hui Wang Zhong Li Yueliang Cheng The Second Artillery Engineering College Xi＇an 710025 China School of Aeronautics Northwest Polytechnical University Xi＇an 710072 China Naval Aeronautical Engineering Academy Qingdao Branch Qingdao 266041 China

The fatigue crack propagation behavior of the LY12CZ aluminum alloy fastener involving a central hole in air or in 3.5wt% NaCl solution was investigated. The experimental results indicated that the corrosion fatigue crack growth rate decreased with the increasing loading frequency,and in a corrosive environment,the crack growth rate was slightly larger than that in air. Based on the experimental results,the virtual corrosion fatigue crack propagation tests were investigated and the stochastic process method and the AFGROW simulation method were presented. The normal process and lognormal process were considered for the stochastic process method based on the numerically fitted Paris equation. The distribution of crack size and the corresponding probabilistic model of crack length distribution for a given number of cycles can be found by integrating the stochastic process over time. Using the AFGROW software,the virtual simulation was carried out to analyze the corrosion fatigue crack growth behavior and the predicted crack growth curve was in good agreement with the experimental results.

关键词： aluminum alloy corrosion fatigue crack propagation stochastic process AFGROW

Development of Correlation Between Surface Crack Size and Corrosion Pit Size for Service Life Prediction

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Development of Correlation Between Surface Crack Size and Co...

基于有限元计算细观力学的复合材料宏观性能的一体化预测

2007国际机械工程与力学会议

作者： Keliang REN guozhi lv Majd-ud-din MUHAMMAD Youhong ZHANG Department of Aeronautical Structural Engineering Northwestern Polytechnical University Department of Physics & Electrical Information Engineering Ningxia University

In order to set up the relation between corrosion pits and equivalent initial surface crack （EISC）, for quantitative assessment of the residual strength of the aging structure in corrosive environment, a series of pre-corroded samples are prepared at different time and temperature, and subsequent fatigue experiments under uniaxial cyclic load have been performed with LY12-CZ Aluminium alloy. After pre-corrosion and fatigue test, the equivalent initial surface crack size is calculated through reverse integration of the Paris fatigue crack growth law and has solved the non-linear equation using Monte Carlo method from the experiment fatigue life. Finally life predictions are made using the pit sizes measured in experiment and EISC size calculated by reverse integration of the Paris fatigue crack growth law as the initial size of surface crack in computer package AFGROW, and compared with the experimented fatigue life. The results show that the size of equivalent initial surface crack is less than 19.7 to 22.5 percent of surface corrosion pit size which has the same life.

关键词： Corrosion pit Surface crack Equivalent initial crack Monte Carlo method Aging structure Residual strength AFGROW

来源： cnki会议评论

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西北工业大学学报 2008年第5期26卷 640-644页

作者：吕毅吕国志赵庆兰熊璇西北工业大学航空学院。陕西西安710072 西安邮电学院陕西西安710061

基于有限元计算细观力学理论,以***为平台,利用PCL实现了RVE的参数化自动建模,建立了RVE库。并根据不同的细观力学方法,通过在后台对RVE边界条件的设置及有限元计算,集成了相应的计算程序,从而实现了复合材料宏观性能的一体化预测。最后... 详细信息

基于有限元计算细观力学理论,以***为平台,利用PCL实现了RVE的参数化自动建模,建立了RVE库。并根据不同的细观力学方法,通过在后台对RVE边界条件的设置及有限元计算,集成了相应的计算程序,从而实现了复合材料宏观性能的一体化预测。最后,以单向复合材料的宏观弹性模量预测为例,展示了一体化预测系统。

关键词：细观力学有限元有限元计算细观力学(FECM) RVE 一体化预测

基于有限元计算细观力学的RVE库的建立与应用

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机械强度 2009年第5期31卷 851-856页

作者：吕毅吕国志孙龙生西北工业大学航空学院西安710072

基于有限元计算细观力学理论,以***为平台,利用PCL(PATRAN command language)实现RVE(repr-esentative volume element)的参数化自动建模,建立RVE库,集成相应的细观力学计算程序,一体化预测复合材料宏观性能。通过工程实例,调用RVE库中... 详细信息

基于有限元计算细观力学理论,以***为平台,利用PCL(PATRAN command language)实现RVE(repr-esentative volume element)的参数化自动建模,建立RVE库,集成相应的细观力学计算程序,一体化预测复合材料宏观性能。通过工程实例,调用RVE库中的平纹编织复合材料RVE,预测平纹编织C/SiC复合材料的宏观弹性模量,对空天飞机全C/SiC复合材料机身襟翼进行静力有限元计算,实现结构材料一体化设计。

关键词：有限元计算细观力学 RVE(representative volume element)库 MSC.PATRAN 空天飞机机身襟翼

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齿轮接触安定分析

机械强度 2007年第6期29卷 1017-1021页

作者：原园徐颖强吕国志西北工业大学航空学院西安710072

以Hertz理论为基础,建立齿轮的接触模型。针对齿轮接触表面层变曲率的特点,构造出局部坐标下残余应力应变场的分布状态,分析在此残余应力场分布状态下,齿轮接触的静力安定和机动安定的条件。采用应力应变释放的算法和不同啮合点局部坐... 详细信息

以Hertz理论为基础,建立齿轮的接触模型。针对齿轮接触表面层变曲率的特点,构造出局部坐标下残余应力应变场的分布状态,分析在此残余应力场分布状态下,齿轮接触的静力安定和机动安定的条件。采用应力应变释放的算法和不同啮合点局部坐标之间的转换法则,模拟齿轮在重复啮合过程中残余应力应变的累积过程,求解安定状态下残余应力的分布状况,确定齿轮接触的安定极限与摩擦因数和齿轮啮合位置之间的变化情况。

关键词：齿轮安定接触残余应力

用概率推断法确定多工况二维疲劳设计谱的载荷最大值

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应用力学学报 2006年第3期23卷 484-487页

作者：易当祥吕国志周雄伟西北工业大学 76321部队

对各工况下的二维疲劳载荷,采用权系数的方法,合成并获得了多工况下的二维载荷联合概率密度函数。并由超越概率10-6对载荷进行外推,研究了确定多工况下二维疲劳设计谱中载荷最大值的概率推断——最速下降法的计算方法和步骤。实例的分... 详细信息

对各工况下的二维疲劳载荷,采用权系数的方法,合成并获得了多工况下的二维载荷联合概率密度函数。并由超越概率10-6对载荷进行外推,研究了确定多工况下二维疲劳设计谱中载荷最大值的概率推断——最速下降法的计算方法和步骤。实例的分析与比较,说明该方法是合理的和准确的,并由载荷最大值的分级和计算,编制了多工况下的8×8的二维疲劳设计谱。

关键词：疲劳设计谱概率推断最速下降法载荷最大值多工况

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腐蚀结构损伤评估方法

机械强度 2007年第6期29卷 992-996页

作者：任克亮吕国志陈跃良西北工业大学航空学院海军航空工程学院青岛分院飞机教研室青岛266041

针对腐蚀环境下老龄化飞机结构表面存在广布随机的腐蚀坑,而使其强度降低这一问题,先采用有限元方法并结合仿真软件ANSYS的参数化分析语言APDL,得到不同形状腐蚀坑底部的有效应力集中系数,然后结合局部应力应变法求解各个腐蚀坑底部在... 详细信息

针对腐蚀环境下老龄化飞机结构表面存在广布随机的腐蚀坑,而使其强度降低这一问题,先采用有限元方法并结合仿真软件ANSYS的参数化分析语言APDL,得到不同形状腐蚀坑底部的有效应力集中系数,然后结合局部应力应变法求解各个腐蚀坑底部在疲劳载荷作用下产生初始裂纹的萌生寿命值,再通过蒙特卡罗方法求解数值积分和非线性方程,得到和腐蚀坑具有相同寿命等效裂纹的尺寸,最后采用神经网络技术建立腐蚀坑各种几何尺寸与等效裂纹深度间的多变量非线性映射关系。为工程实践中用广布裂纹方法处理含随机分布腐蚀坑的老龄化结构提供可能。

关键词：腐蚀坑局部应力应变裂纹萌生寿命等效裂纹蒙特卡罗方法神经网络