An experimental study was carried out on the strain cyclic characteristics and ratcheting of U71Mn rail steel subjected to non-proportional multiaxial cyclic loading. The strain cyclic characteristics were researched ...An experimental study was carried out on the strain cyclic characteristics and ratcheting of U71Mn rail steel subjected to non-proportional multiaxial cyclic loading. The strain cyclic characteristics were researched under the strain-controlled circular load path. The ratcheting was investigated for the stress-controlled multiaxial circular, elliptical and rhombic load paths with different mean stresses, stress amplitudes and their histories. The experiment shows that U71Mn rail steel features the cyclic non-hardening/softening, and its strain cyclic characteristics depend greatly on the strain amplitude but slightly on its history. However, the ratcheting of U71Mn rail steel depends greatly not only on the values of mean stress and stress amplitude, but also on their histories. In the meantime, the shape of load path and its history also apparently influence the ratcheting. The ratcheting changes with the different loading paths.展开更多
Based on the low-cycle fatigue tests of carbon and alloy steels,the cyclic properties of hysteresis energy and its changing rules have been analysed.The mathematical formula of cyclic hysteresis energy of the material...Based on the low-cycle fatigue tests of carbon and alloy steels,the cyclic properties of hysteresis energy and its changing rules have been analysed.The mathematical formula of cyclic hysteresis energy of the materials with different cyclic properties have been presented. The total absorbed energy to failure is associated with the variation of cyclic hysteresis energy.展开更多
In chloroplast, there were two pathways involved in the cyclic electron flow around photosystem 1 （PS 1）. One was the NADH dehydrogenase （NDH）-dependent flow and the other was the ferredoxin quinone reductase-depe...In chloroplast, there were two pathways involved in the cyclic electron flow around photosystem 1 （PS 1）. One was the NADH dehydrogenase （NDH）-dependent flow and the other was the ferredoxin quinone reductase-dependent flow. It was proposed that the NDH-dependent cyclic electron flow around PSI was related to the xanthophyll cycle-dependent non-photochemical quenching （NPQ） at chilling temperature under low irradiance （CL）. The function of the chloroplastic cyclic electron flow around PS 1 was examined by comparing sweet pepper （Capsicum annuum L.） control with its antimycin A （AA）-fed leaves upon exposure to CL stress. During CL stress, the maximum photochemical efficiency of PS2 （Fv/Fm） decreased markedly in both controls and AA-fed leaves, and P700＋ was also lower in AA-fed leaves than in controls. These results implied that cyclic electron flow around PS 1 functioned to protect the photosynthetic apparatus from CL stress. Under such stress, NPQ and PS2-driven electron transport rate were different between AA-fed leaves and controls. The lower NPQ in AA-fed leaves might be related to an inefficient proton gradient across thylakoid membranes （ApH） because of inhibiting cyclic electron flow around PS 1 under CL stress.展开更多
基金Financially supported by the National Natural Science Foundation of China(197T2041)the Excellent Youth Fund of Sichuan Province.
文摘An experimental study was carried out on the strain cyclic characteristics and ratcheting of U71Mn rail steel subjected to non-proportional multiaxial cyclic loading. The strain cyclic characteristics were researched under the strain-controlled circular load path. The ratcheting was investigated for the stress-controlled multiaxial circular, elliptical and rhombic load paths with different mean stresses, stress amplitudes and their histories. The experiment shows that U71Mn rail steel features the cyclic non-hardening/softening, and its strain cyclic characteristics depend greatly on the strain amplitude but slightly on its history. However, the ratcheting of U71Mn rail steel depends greatly not only on the values of mean stress and stress amplitude, but also on their histories. In the meantime, the shape of load path and its history also apparently influence the ratcheting. The ratcheting changes with the different loading paths.
文摘Based on the low-cycle fatigue tests of carbon and alloy steels,the cyclic properties of hysteresis energy and its changing rules have been analysed.The mathematical formula of cyclic hysteresis energy of the materials with different cyclic properties have been presented. The total absorbed energy to failure is associated with the variation of cyclic hysteresis energy.
基金supported by the National Natural Science Foundation of China(30571126)the Scientific Research Encouragement Foundation for 0utstanding Young and Middle Scientist of Shandong Province(2005BS06003)the open project from Key Laboratory of Crop Biology of Shandong Province,China.
文摘In chloroplast, there were two pathways involved in the cyclic electron flow around photosystem 1 （PS 1）. One was the NADH dehydrogenase （NDH）-dependent flow and the other was the ferredoxin quinone reductase-dependent flow. It was proposed that the NDH-dependent cyclic electron flow around PSI was related to the xanthophyll cycle-dependent non-photochemical quenching （NPQ） at chilling temperature under low irradiance （CL）. The function of the chloroplastic cyclic electron flow around PS 1 was examined by comparing sweet pepper （Capsicum annuum L.） control with its antimycin A （AA）-fed leaves upon exposure to CL stress. During CL stress, the maximum photochemical efficiency of PS2 （Fv/Fm） decreased markedly in both controls and AA-fed leaves, and P700＋ was also lower in AA-fed leaves than in controls. These results implied that cyclic electron flow around PS 1 functioned to protect the photosynthetic apparatus from CL stress. Under such stress, NPQ and PS2-driven electron transport rate were different between AA-fed leaves and controls. The lower NPQ in AA-fed leaves might be related to an inefficient proton gradient across thylakoid membranes （ApH） because of inhibiting cyclic electron flow around PS 1 under CL stress.
文摘为了研究使用矩形钢管连接的新型全预制冷弯薄壁型钢复合墙体的抗侧性能,设计了6个足尺试件,并进行了水平低周往复加载试验,分析了龙骨间距、覆面板类型、单面或双面覆板等因素对新型复合墙体试件抗侧性能的影响.新型墙体的覆面板为OSB板与硅晶钙板.试验结果表明:使用矩形钢管连接的新型复合墙体具有良好的整体抗震性能;单面或双面覆板对墙体抗侧性能影响显著,双面覆板的新型复合墙体的屈服荷载约为单面覆板新型复合墙体的2倍;龙骨间距和覆面板材料对墙体抗侧性能的影响相对较小.在试验基础上,使用OpenSEES软件建立了试验墙体的有限元分析模型,并针对矩形钢管壁厚、周边螺钉间距取值进行了参数分析.参数分析结果表明,矩形钢管连接件壁厚取值推荐为2.5 mm,周边螺钉间距推荐取50~100 mm.
