针对温度变化引起超声衍射时差技术(time of flight diffraction,TOFD)测量结果误差的现象,以含不同预置缺陷Q235A试块为测试样品,采用TOFD超声检测技术,并结合A扫结果,研究不同温度对缺陷检测结果的影响。研究发现,当试块表面温度超过4...针对温度变化引起超声衍射时差技术(time of flight diffraction,TOFD)测量结果误差的现象,以含不同预置缺陷Q235A试块为测试样品,采用TOFD超声检测技术,并结合A扫结果,研究不同温度对缺陷检测结果的影响。研究发现,当试块表面温度超过40℃时,底面小缺陷的检测难度会提高,检测结果的不稳定性提升;随着试块表面温度继续升高,TOFD测量缺陷的最小分辨率会降低到3 mm,同时小缺陷波的A扫波形已经无法从背景噪声中识别。通过比较不同温度下纵波在固体介质中传播速度,发现温度升高导致纵波速度衰减,进而导致仪器分辨力的下降和实际测量误差的增大。展开更多
Concrete creep under both static and cyclic loading conditions was investigated. Four groups of high-strength high-performance concrete(HSHPC) prism specimens were fabricated, and three of these specimens were loaded ...Concrete creep under both static and cyclic loading conditions was investigated. Four groups of high-strength high-performance concrete(HSHPC) prism specimens were fabricated, and three of these specimens were loaded periodically by the MTS Landmark Fatigue Testing Machine System. Creep characteristics and creep coefficients of HSHPC under static loading and cyclic loading, respectively, were obtained and compared. The experimental results show that the creep strains under cyclic loading with a mean stress of 0.4 fcp and an amplitude of 0.2 fcp increase significantly compared with the creep strains under static loading, and the maximum value was 1.2-2.3 times at early stages. In addition, the creep coefficient increases nonlinearly with the number of cyclic loading repetitions. The influence coefficient for cyclic loading γcyc=1.088×(N/N0)0.078 was introduced based on the previous HSHPC creep model, and then the modified creep model under cyclic loading was established. Finally, the residual method, the CEB coefficient of variation method and the B3 coefficient of variation method were applied to evaluate the modified creep model. The statistical results demonstrate that the modified creep model agrees well with the experimental measurements. Hence, it has important theoretical and practical values for accurately predicting the deflection of concrete bridges under cyclic traffic loading.展开更多
Due to the impact of globalization,more and more universities in China dedicate to improve the quality of undergraduate education.The particular emphasis was given on the universities in Mid-west university of China,w...Due to the impact of globalization,more and more universities in China dedicate to improve the quality of undergraduate education.The particular emphasis was given on the universities in Mid-west university of China,where the economics and transportation facility are relatively less developed comparing to other regions.In contrast of the traditional methodologies of social science,this research was conducted using an engineering design methodology,called Environment-Based Design(EBD).The EBD procedure allows to derive the solutions step-by-step based on a holistic environment analysis and thus an identification of major challenges.展开更多
文摘针对温度变化引起超声衍射时差技术(time of flight diffraction,TOFD)测量结果误差的现象,以含不同预置缺陷Q235A试块为测试样品,采用TOFD超声检测技术,并结合A扫结果,研究不同温度对缺陷检测结果的影响。研究发现,当试块表面温度超过40℃时,底面小缺陷的检测难度会提高,检测结果的不稳定性提升;随着试块表面温度继续升高,TOFD测量缺陷的最小分辨率会降低到3 mm,同时小缺陷波的A扫波形已经无法从背景噪声中识别。通过比较不同温度下纵波在固体介质中传播速度,发现温度升高导致纵波速度衰减,进而导致仪器分辨力的下降和实际测量误差的增大。
基金Supported by Key Project of Chinese National Programs for Fundamental Research and Development(No.2017YFB 0310105-03)Key Foundation Projects of Hubei Province(No.2016CFA074)Technology Innovation Major Project of Hubei Province(No.2018AAA001-04)
文摘Concrete creep under both static and cyclic loading conditions was investigated. Four groups of high-strength high-performance concrete(HSHPC) prism specimens were fabricated, and three of these specimens were loaded periodically by the MTS Landmark Fatigue Testing Machine System. Creep characteristics and creep coefficients of HSHPC under static loading and cyclic loading, respectively, were obtained and compared. The experimental results show that the creep strains under cyclic loading with a mean stress of 0.4 fcp and an amplitude of 0.2 fcp increase significantly compared with the creep strains under static loading, and the maximum value was 1.2-2.3 times at early stages. In addition, the creep coefficient increases nonlinearly with the number of cyclic loading repetitions. The influence coefficient for cyclic loading γcyc=1.088×(N/N0)0.078 was introduced based on the previous HSHPC creep model, and then the modified creep model under cyclic loading was established. Finally, the residual method, the CEB coefficient of variation method and the B3 coefficient of variation method were applied to evaluate the modified creep model. The statistical results demonstrate that the modified creep model agrees well with the experimental measurements. Hence, it has important theoretical and practical values for accurately predicting the deflection of concrete bridges under cyclic traffic loading.
基金one of outcomes of a research program numbered KYJY201605
文摘Due to the impact of globalization,more and more universities in China dedicate to improve the quality of undergraduate education.The particular emphasis was given on the universities in Mid-west university of China,where the economics and transportation facility are relatively less developed comparing to other regions.In contrast of the traditional methodologies of social science,this research was conducted using an engineering design methodology,called Environment-Based Design(EBD).The EBD procedure allows to derive the solutions step-by-step based on a holistic environment analysis and thus an identification of major challenges.
