A reliability assessment method of fatigue life based on the long-term monitoring data is developed for welded details in steel box girder,and the application research is presented with examples of welded rib-to-deck ...A reliability assessment method of fatigue life based on the long-term monitoring data is developed for welded details in steel box girder,and the application research is presented with examples of welded rib-to-deck details in Runyang Bridges. Firstly the fatigue damage limit-state function is established based on S-N curves and Miner's rule,and the probability distribution characteristics of the coefficients in the function are discussed in detail. The uncertainties in fatigue loading effects are mainly studied based on long-term monitoring data. In the traditional studies,only the uncertainty of equivalent stress range is considered in fatigue reliability assessment. However,stress cycle number is also treated as a random variable in this paper because we know traffic flow every day differs in a thousand ways. Then the optimization method is employed to calculate the fatigue reliability. After studying the changing law of the reliability indices with time and the effect of the randomness of stress cycle number on reliability,the effect of the traffic growth on the reliability is studied. This study shows that the uncertainty in the fatigue life of the welded details can be well studied based on structural health monitoring,so it is necessary to carry out long-term strain monitoring of the welded details for accurate fatigue reliability assessment during the whole service period.展开更多
This paper focuses on the laminar flame instability of three high molecular weight n-alkanes,namely n-hexane,n-octane,and n-decane.The experiment was carried out in a constant volume combustion bomb to get the flame i...This paper focuses on the laminar flame instability of three high molecular weight n-alkanes,namely n-hexane,n-octane,and n-decane.The experiment was carried out in a constant volume combustion bomb to get the flame images.The critical radius under different conditions was extracted using the image processing program.Combined with the existing critical Peclet number theory,the dominant factors of flame instability under current conditions for three n-alkanes can be figured out.Moreover,the average cell size(equivalent cell radius,R_(cell))was extracted to provide quantitative analysis of the flame cellular structure,based on the method developed in this work.The theoretical R_(cell)were also calculated and compared with the experimental results to validate the proposed method.展开更多
There are many types of cyclone dust collectors for separating the fine solid and dust particles from gases in the various industries and also in the home used purposes. For estimating the power loss and the collectio...There are many types of cyclone dust collectors for separating the fine solid and dust particles from gases in the various industries and also in the home used purposes. For estimating the power loss and the collection efficiency, one of the most important factors is the maximum tangential velocity V0m in the vortex core region in the cyclone body. In order to determine V0~ by the simple method, it is useful to apply the mechanical balance of the angular momentum fluxes under the assumption of Ogawa combined vortex model which is composed of the quasi-forced vortex in the vortex core region and also the quasi-free vortex surrounded the vortex core region and also under the assumption of the introduction of equivalent length Heq corresponding to the cone spaces of the cyclone body and the dust bunker. On the other hand, the mean rotational velocity Voi near the concave wall surface is also estimated by the mechanical balance of angular momentum fluxes with the moment of viscous friction force. For confirming the general applications of the obtained equations, the returned flow types cyclones changed the throat diameter D3 are designed. The material of the cyclone is the transparent acrylic resin. Therefore the inner surface of the cyclone body can be regarded as smooth surface. The comparisons of the measured velocities V~ and Voi by a cylindrical Pitot tube are shown in good agreement with those of the proposed equations. The above stated results are described in detail.展开更多
针对电动车辆的复杂行驶工况,提出一种基于雨流计数原理的实时预估钴酸锂电池健康状态(state of health,SOH)的建模方法。首先,开发了一种改进的实时雨流计数法,实现对不同放电深度(depth of discharge,DOD)下循环次数的统计分析;在此...针对电动车辆的复杂行驶工况,提出一种基于雨流计数原理的实时预估钴酸锂电池健康状态(state of health,SOH)的建模方法。首先,开发了一种改进的实时雨流计数法,实现对不同放电深度(depth of discharge,DOD)下循环次数的统计分析;在此基础上,提出一种利用等效充放电电流–荷电状态(state of charge,SOC)的包络面积,来评估每次循环中衰减因子的计算方法,并以不同循环次数下衰减因子的累加和来刻画电池的寿命衰减;最后,设计电池循环老化实验,验证了所提出方法可实现对随机充放电电流、DOD和循环次数下的电池SOH实时估计。展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.50725828,50808041)Scientific Research Foundation of Graduate School of Southeast University (Grant No. YBJJ0923)Teaching and Research Foundation for Excellent Young Teacher of Southeast University
文摘A reliability assessment method of fatigue life based on the long-term monitoring data is developed for welded details in steel box girder,and the application research is presented with examples of welded rib-to-deck details in Runyang Bridges. Firstly the fatigue damage limit-state function is established based on S-N curves and Miner's rule,and the probability distribution characteristics of the coefficients in the function are discussed in detail. The uncertainties in fatigue loading effects are mainly studied based on long-term monitoring data. In the traditional studies,only the uncertainty of equivalent stress range is considered in fatigue reliability assessment. However,stress cycle number is also treated as a random variable in this paper because we know traffic flow every day differs in a thousand ways. Then the optimization method is employed to calculate the fatigue reliability. After studying the changing law of the reliability indices with time and the effect of the randomness of stress cycle number on reliability,the effect of the traffic growth on the reliability is studied. This study shows that the uncertainty in the fatigue life of the welded details can be well studied based on structural health monitoring,so it is necessary to carry out long-term strain monitoring of the welded details for accurate fatigue reliability assessment during the whole service period.
基金supported by the National Natural Science Foundation of China(52106182,51888103)the National Science and Technology Major Project(2019-Ⅲ-0018-0062)+1 种基金supported by the State Key Laboratory of Clean Energy Utilization(Open Fund Project No.ZJUCEU2021016)Shaanxi Nature Science Foundation(No.2021JQ-265)。
文摘This paper focuses on the laminar flame instability of three high molecular weight n-alkanes,namely n-hexane,n-octane,and n-decane.The experiment was carried out in a constant volume combustion bomb to get the flame images.The critical radius under different conditions was extracted using the image processing program.Combined with the existing critical Peclet number theory,the dominant factors of flame instability under current conditions for three n-alkanes can be figured out.Moreover,the average cell size(equivalent cell radius,R_(cell))was extracted to provide quantitative analysis of the flame cellular structure,based on the method developed in this work.The theoretical R_(cell)were also calculated and compared with the experimental results to validate the proposed method.
文摘There are many types of cyclone dust collectors for separating the fine solid and dust particles from gases in the various industries and also in the home used purposes. For estimating the power loss and the collection efficiency, one of the most important factors is the maximum tangential velocity V0m in the vortex core region in the cyclone body. In order to determine V0~ by the simple method, it is useful to apply the mechanical balance of the angular momentum fluxes under the assumption of Ogawa combined vortex model which is composed of the quasi-forced vortex in the vortex core region and also the quasi-free vortex surrounded the vortex core region and also under the assumption of the introduction of equivalent length Heq corresponding to the cone spaces of the cyclone body and the dust bunker. On the other hand, the mean rotational velocity Voi near the concave wall surface is also estimated by the mechanical balance of angular momentum fluxes with the moment of viscous friction force. For confirming the general applications of the obtained equations, the returned flow types cyclones changed the throat diameter D3 are designed. The material of the cyclone is the transparent acrylic resin. Therefore the inner surface of the cyclone body can be regarded as smooth surface. The comparisons of the measured velocities V~ and Voi by a cylindrical Pitot tube are shown in good agreement with those of the proposed equations. The above stated results are described in detail.
文摘针对电动车辆的复杂行驶工况,提出一种基于雨流计数原理的实时预估钴酸锂电池健康状态(state of health,SOH)的建模方法。首先,开发了一种改进的实时雨流计数法,实现对不同放电深度(depth of discharge,DOD)下循环次数的统计分析;在此基础上,提出一种利用等效充放电电流–荷电状态(state of charge,SOC)的包络面积,来评估每次循环中衰减因子的计算方法,并以不同循环次数下衰减因子的累加和来刻画电池的寿命衰减;最后,设计电池循环老化实验,验证了所提出方法可实现对随机充放电电流、DOD和循环次数下的电池SOH实时估计。
