The exploration of material failure behavior not only involves defining its limits and underlying mechanisms but also entails devising strategies for improvement and protection in extreme conditions.We've pioneere...The exploration of material failure behavior not only involves defining its limits and underlying mechanisms but also entails devising strategies for improvement and protection in extreme conditions.We've pioneered an advanced multi-scale,high-speed ascending thermal shock testing platform capable of inducing unprecedented heat shocks at rates surpassing 105℃/s.Through meticulous examination of the thermal shock responses of carbon nanotube(CNT)films,we've achieved remarkable breakthroughs.By employing an innovative macro-scale synchronous tightening and relaxing approach,we've attained a critical temperature differential in CNT films that exceeds an exceptional 2500℃—surpassing any previously reported metric for highperformance,thermal-shock-resistant materials.Notably,these samples have demonstrated exceptional resilience,retaining virtually unchanged strength even after enduring 10,000 thermal shock cycles at temperatures exceeding 1000℃.Furthermore,our research has revealed a novel thermal shock/fatigue failure mechanism that fundamentally diverges from conventional theories centered on thermal stress.展开更多
在大规模风电基地通过电网换相高压直流输电(LCCHVDC)远距离送出的背景下,直流系统换相失败故障会在送端产生暂态电压扰动。已有研究缺乏对风电机组呈现出的电压“先低后高”连续变化且磁链不断累积特性的探讨,亟须从磁链累积的角度分...在大规模风电基地通过电网换相高压直流输电(LCCHVDC)远距离送出的背景下,直流系统换相失败故障会在送端产生暂态电压扰动。已有研究缺乏对风电机组呈现出的电压“先低后高”连续变化且磁链不断累积特性的探讨,亟须从磁链累积的角度分析风电机组在换相失败期间的电压特性,提出一种具有暂态电压抑制作用的风机故障穿越(fault ride through,FRT)策略。首先,采用曲线拟合的方法,推导了双馈风电机组(doubly fed induction generator,DFIG)在直流系统换相失败期间的电压与磁链方程,分析了直流系统定电流环节(constant current amplifier,CCA)控制对暂态过电压的影响;其次,提出一种基于灭磁控制的故障穿越策略,通过全定子磁链观测并引入灭磁系数,在转子侧变流器(rotor side converter,RSC)有功、无功电流参考值中分别计及灭磁电流,拓宽了RSC无功输出的能力。最后,MATLAB/Simulink平台验证了所提策略在实现DFIG故障穿越的基础上还能够进一步抑制暂态过电压,提高了系统稳定性与安全性。展开更多
退役零件的失效程度是判断其可再制造性的关键因素之一,为克服失效程度难以快速精确量化的问题,提出一种基于图像三维重建的退役零件失效特征表征方法。针对失效特征重建精度要求高的特点,在由运动恢复形状(Shape from motion,SFM)算法...退役零件的失效程度是判断其可再制造性的关键因素之一,为克服失效程度难以快速精确量化的问题,提出一种基于图像三维重建的退役零件失效特征表征方法。针对失效特征重建精度要求高的特点,在由运动恢复形状(Shape from motion,SFM)算法的基础上提出一种自标定全局SFM三维点云重建算法,利用光束平差法优化相机焦距、径向畸变参数,实现了相机自标定,增加了全局SFM算法的鲁棒性;以重建有效三维点数量占比、点云完整度和相机位姿准确度为评价指标,构建了重建精度评价模型,实现了图像三维重建精度的量化评价;提出了退役零件表面失效特征量化方法和实施流程,并定义了失效特征信息计算公式;最后,以电梯导靴为例,对其表面磨损失效特征进行了量化表征。试验结果表明,该方法可以有效地用于毫米级及以上的退役零件表面失效特征的快速量化表征。展开更多
The rapid evolution of flexible electronic devices promises to revolutionize numerous fields by expanding the applications of smart devices.Nevertheless,despite this vast potential,the reliability of these innovative ...The rapid evolution of flexible electronic devices promises to revolutionize numerous fields by expanding the applications of smart devices.Nevertheless,despite this vast potential,the reliability of these innovative devices currently falls short,especially in light of demanding operation environment and the intrinsic challenges associated with their fabrication techniques.The heterogeneity in these processes and environments gives rise to unique failure modes throughout the devices'lifespan.To significantly enhance the reliability of these devices and assure long-term performance,it is paramount to comprehend the underpinning failure mechanisms thoroughly,thereby,enabling,optimal design solutions.A myriad of investigative efforts have been dedicated to unravel these failure mechanisms,utilizing a spectrum of tools from analytical models,numerical methods,to advanced characterization methods.This review delves into the root causes of device failure,scrutinizing both the fabrication process and the operation environment.Next,We subsequently address the failure mechanisms across four commonly observed modes:strength failure,fatigue failure,interfacial failure,and electrical failure,followed by an overview of targeted characterization methods associated with each mechanism.Concluding with an outlook,we spotlight ongoing challenges and promising directions for future research in our pursuit of highly resilient flexible electronic devices.展开更多
Tensile deformation and fracture characteristics of polyimide/montmorillonite nanocomposite films are investigated to enhance the particular mechanical properties and understand the effective factors in dominating the...Tensile deformation and fracture characteristics of polyimide/montmorillonite nanocomposite films are investigated to enhance the particular mechanical properties and understand the effective factors in dominating the mechanical properties of nanocomposites, such as the nanolayer, matrix and nanolayer/matrix interface. How to contribute to the mechanical properties of nanocomposite film is a very complex problem. In this paper, these factors are analyzed based on the addition amount and fracture mechanics. The results indicate that the specimen at 20 wt% MMT breaks prematurely with a fracture strength （σb = 78 MPa） much lower than that （σb = 128 MPa） at the 1 wt% MMT. However, the Young＇s modulus （3.2 GPa） of the former is higher than that （1.9 GPa） of the latter. Fractography also indicates that the brittle cracking formed in high content addition is the main cause of failure but microscopically ductile fracture morphology still exists locally. And for the trace element addition, the smaller threading slipping veins are evenly distributed on the entire fracture section of these films. Therefore, these characteristics would presumably be associated with both the concentration effects of size of nanocomposite sheets and the increasing deformation harmony in nanolayers.展开更多
基金supported by the National Key Basic Research Program of China(No.2022YFA1205400)the National Natural Science Foundation of China(Nos.11832010,11890682,and 21721002)+3 种基金the Chinese Postdoctoral Science Foundation(Nos.E1I41IR1 and E2911IR1)Special Research Assistant Program of Chinese Academy of Sciences(No.E37551R1)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36010200)the Austrian-Chinese Cooperative Research and Development Projects(No.GJHZ2043).
文摘The exploration of material failure behavior not only involves defining its limits and underlying mechanisms but also entails devising strategies for improvement and protection in extreme conditions.We've pioneered an advanced multi-scale,high-speed ascending thermal shock testing platform capable of inducing unprecedented heat shocks at rates surpassing 105℃/s.Through meticulous examination of the thermal shock responses of carbon nanotube(CNT)films,we've achieved remarkable breakthroughs.By employing an innovative macro-scale synchronous tightening and relaxing approach,we've attained a critical temperature differential in CNT films that exceeds an exceptional 2500℃—surpassing any previously reported metric for highperformance,thermal-shock-resistant materials.Notably,these samples have demonstrated exceptional resilience,retaining virtually unchanged strength even after enduring 10,000 thermal shock cycles at temperatures exceeding 1000℃.Furthermore,our research has revealed a novel thermal shock/fatigue failure mechanism that fundamentally diverges from conventional theories centered on thermal stress.
文摘在大规模风电基地通过电网换相高压直流输电(LCCHVDC)远距离送出的背景下,直流系统换相失败故障会在送端产生暂态电压扰动。已有研究缺乏对风电机组呈现出的电压“先低后高”连续变化且磁链不断累积特性的探讨,亟须从磁链累积的角度分析风电机组在换相失败期间的电压特性,提出一种具有暂态电压抑制作用的风机故障穿越(fault ride through,FRT)策略。首先,采用曲线拟合的方法,推导了双馈风电机组(doubly fed induction generator,DFIG)在直流系统换相失败期间的电压与磁链方程,分析了直流系统定电流环节(constant current amplifier,CCA)控制对暂态过电压的影响;其次,提出一种基于灭磁控制的故障穿越策略,通过全定子磁链观测并引入灭磁系数,在转子侧变流器(rotor side converter,RSC)有功、无功电流参考值中分别计及灭磁电流,拓宽了RSC无功输出的能力。最后,MATLAB/Simulink平台验证了所提策略在实现DFIG故障穿越的基础上还能够进一步抑制暂态过电压,提高了系统稳定性与安全性。
文摘退役零件的失效程度是判断其可再制造性的关键因素之一,为克服失效程度难以快速精确量化的问题,提出一种基于图像三维重建的退役零件失效特征表征方法。针对失效特征重建精度要求高的特点,在由运动恢复形状(Shape from motion,SFM)算法的基础上提出一种自标定全局SFM三维点云重建算法,利用光束平差法优化相机焦距、径向畸变参数,实现了相机自标定,增加了全局SFM算法的鲁棒性;以重建有效三维点数量占比、点云完整度和相机位姿准确度为评价指标,构建了重建精度评价模型,实现了图像三维重建精度的量化评价;提出了退役零件表面失效特征量化方法和实施流程,并定义了失效特征信息计算公式;最后,以电梯导靴为例,对其表面磨损失效特征进行了量化表征。试验结果表明,该方法可以有效地用于毫米级及以上的退役零件表面失效特征的快速量化表征。
基金support by the National Natural Science Foundation of China(NSFC)[Grant No.11972325,12272342,12202398]the Natural Science Foundation of Zhejiang Province(LGF20A020001).
文摘The rapid evolution of flexible electronic devices promises to revolutionize numerous fields by expanding the applications of smart devices.Nevertheless,despite this vast potential,the reliability of these innovative devices currently falls short,especially in light of demanding operation environment and the intrinsic challenges associated with their fabrication techniques.The heterogeneity in these processes and environments gives rise to unique failure modes throughout the devices'lifespan.To significantly enhance the reliability of these devices and assure long-term performance,it is paramount to comprehend the underpinning failure mechanisms thoroughly,thereby,enabling,optimal design solutions.A myriad of investigative efforts have been dedicated to unravel these failure mechanisms,utilizing a spectrum of tools from analytical models,numerical methods,to advanced characterization methods.This review delves into the root causes of device failure,scrutinizing both the fabrication process and the operation environment.Next,We subsequently address the failure mechanisms across four commonly observed modes:strength failure,fatigue failure,interfacial failure,and electrical failure,followed by an overview of targeted characterization methods associated with each mechanism.Concluding with an outlook,we spotlight ongoing challenges and promising directions for future research in our pursuit of highly resilient flexible electronic devices.
基金Project supported by the National Basic Research Program of China (No.2004CB619304)the Hundred TalentsProgram of Chinese Academy of Sciences, Key Research Programme of Beijing City Science and Technology Committee(No.H020420020230).
文摘Tensile deformation and fracture characteristics of polyimide/montmorillonite nanocomposite films are investigated to enhance the particular mechanical properties and understand the effective factors in dominating the mechanical properties of nanocomposites, such as the nanolayer, matrix and nanolayer/matrix interface. How to contribute to the mechanical properties of nanocomposite film is a very complex problem. In this paper, these factors are analyzed based on the addition amount and fracture mechanics. The results indicate that the specimen at 20 wt% MMT breaks prematurely with a fracture strength （σb = 78 MPa） much lower than that （σb = 128 MPa） at the 1 wt% MMT. However, the Young＇s modulus （3.2 GPa） of the former is higher than that （1.9 GPa） of the latter. Fractography also indicates that the brittle cracking formed in high content addition is the main cause of failure but microscopically ductile fracture morphology still exists locally. And for the trace element addition, the smaller threading slipping veins are evenly distributed on the entire fracture section of these films. Therefore, these characteristics would presumably be associated with both the concentration effects of size of nanocomposite sheets and the increasing deformation harmony in nanolayers.
