Cast iron alloys with low production cost and quite good mechanical properties are widely used in the automotive industry.To study the mechanical behavior of a typical ductile cast iron(GJS-450)with nodular graphite,u...Cast iron alloys with low production cost and quite good mechanical properties are widely used in the automotive industry.To study the mechanical behavior of a typical ductile cast iron(GJS-450)with nodular graphite,uni-axial quasi-static and dynamic tensile tests at strain rates of 10^(-4),1,10,100,and 250 s^(-1)were carried out.In order to investigate the influence of stress state on the deformation and fracture parameters,specimens with various geometries were used in the experiments.Stress strain curves and fracture strains of the GJS-450 alloy in the strain rate range of 10^(-4)to 250 s^(-1)were obtained.A strain rate-dependent plastic flow model was proposed to describe the mechanical behavior in the corresponding strain-rate range.The available damage model was extended to take the strain rate into account and calibrated based on the analysis of local fracture strains.Simulations with the proposed plastic flow model and the damage model were conducted to observe the deformation and fracture process.The results show that the strain rate has obviously nonlinear effects on the yield stress and fracture strain of GJS-450 alloys.The predictions with the proposed plastic flow and damage models at various strain rates agree well with the experimental results,which illustrates that the rate-dependent plastic flow and damage models can be used to describe the mechanical behavior of cast iron alloys at elevated strain rates.The proposed plastic flow and damage models can be used to describe the deformation and fracture analysis of materials with similar properties.展开更多
歌剧作曲家罗西尼是19世纪意大利的音乐天才,仅用十三天完成的歌剧《塞维利亚理发师》是喜歌剧最经典的代表作。这部歌剧的原型出自法国作家博马舍于1775年所写的剧本,原名《Le Barbier de Séville》。故事延续自博马舍的剧本《费...歌剧作曲家罗西尼是19世纪意大利的音乐天才,仅用十三天完成的歌剧《塞维利亚理发师》是喜歌剧最经典的代表作。这部歌剧的原型出自法国作家博马舍于1775年所写的剧本,原名《Le Barbier de Séville》。故事延续自博马舍的剧本《费加罗的婚礼》,而莫扎特于1786年作曲的同名歌剧即是基于此而写的。本文拟对《塞维利亚理发师》这部歌剧和剧中罗西娜的咏叹调《美妙的歌声随风荡漾》(Una voce poco fa{II Barbiere di Siviglia})做个简单的介绍,对罗西尼的创作特点和音乐风格进行粗浅的探究,对这首咏叹调的音乐进行较详细的分析,并谈谈本人演唱这首咏叹调的体会。展开更多
30CrMnSiA合金钢的室温成形性能差,为探究30CrMnSiA材料电流辅助成形的可行性,基于不同试验参数的电流辅助拉伸试验,研究了温度及脉冲电流参数(电流密度、脉冲占空比和频率)对30CrMnSiA流动应力的影响规律。研究表明:30CrMnSiA的强度及...30CrMnSiA合金钢的室温成形性能差,为探究30CrMnSiA材料电流辅助成形的可行性,基于不同试验参数的电流辅助拉伸试验,研究了温度及脉冲电流参数(电流密度、脉冲占空比和频率)对30CrMnSiA流动应力的影响规律。研究表明:30CrMnSiA的强度及伸长率随温度及电流密度的升高而下降,受脉冲占空比和频率影响不大;脉冲电流能抑制动态应变时效的强化作用,并促进碳化物的析出,使材料塑性下降。基于Voce模型基础,建立了考虑应变速率、温度及脉冲电流参数影响的30Cr Mn Si A电流辅助流动应力模型。利用该模型计算的结果与试验值吻合较好,说明该模型能准确预测材料在电流辅助条件下的流动应力。展开更多
Two kinds of steels （YP960 and YP690） with low carbon bainite structure were designed, and their flow stress and strain hardening exponents were studied. The results showed that, when Hollomon relation was applied t...Two kinds of steels （YP960 and YP690） with low carbon bainite structure were designed, and their flow stress and strain hardening exponents were studied. The results showed that, when Hollomon relation was applied to descrihe the flow stress, there were significanl errors between the experimental and calculated points in specimens tempered below 400 ℃, while a high precision was ohserved in samples tempered above 400℃. Whereas, the modijied Voce relation could effectively predici the flow stress as well as the strain hardening exponent at different tempe ring temperatures, which was verified by unbiased estimators such as maximum relative error （MRXE） and average ahsolute relative error （AARE）. Besides, the modified Voee relation was also applied to estimate the maximum uniform strain, and the correlation coefficients （R） between the experimental data and calculated maximum uniform strain were more than 0.91. The high correlation coefficients indicated that the modified Vote relation could effec lively predict the uniform deformation ability of high strength steels with low carbon bainite structure at different tempering temperatures.展开更多
The effect of anodic polarization on the plastic deformation behavior and formability of FeSi6.5 steel at room temperature was experimentally investigated through uniaxial tensile and drawing of wire specimen in sulfu...The effect of anodic polarization on the plastic deformation behavior and formability of FeSi6.5 steel at room temperature was experimentally investigated through uniaxial tensile and drawing of wire specimen in sulfuric acid solution with current densities of 0-40 mA/cm2.The formability of the FeSi6.5 steel was significantly improved after the anodic polarization.The plastic elongation of the specimen as an anode in the electrochemical environment was 4.4%-7%,but 2.7%in the air.The drawing force under the anodic polarization decreased by 12.5%-26%compared to that in deionized water.The softening is mainly attributed to the relief in work hardening caused by surface atomic dissolution.The work hardening mechanism of the FeSi6.5 steel wires under anodic polarization condition was analyzed using Hollomon equation and Voce relation combined with the Kocks-Mecking approach.These data support the view that the surface atom dissolution facilitates dislocation slip.FeSi6.5 steel wires were obtained using electrochemical cold drawing and presented a smooth surface and good ductility without crack after five-pass drawing with a total cross-section area reduction of 88%.The drawing with the assistance of anodic polarization is a promising technology for processing hard and brittle metal materials.展开更多
自20世纪初录音设备应用于记录演唱以来,不同时代的女高音曲目有大量的录音档案,它们是研究和分析100多年来歌手们对音乐的独特诠释的宝贵资源。同时,声乐科学为声乐教学提供了更新的应用,如功率谱和电声门图。通过主观的听觉感知对录...自20世纪初录音设备应用于记录演唱以来,不同时代的女高音曲目有大量的录音档案,它们是研究和分析100多年来歌手们对音乐的独特诠释的宝贵资源。同时,声乐科学为声乐教学提供了更新的应用,如功率谱和电声门图。通过主观的听觉感知对录音进行分析,由于个体感官的差异,结果可能不太可靠,而这些仪器都是客观和直接地来分析声乐信号,研究声乐发声原理,并帮助声乐教师处理复杂的声乐问题的方法。文章根据20世纪至今的四个录音时期,选择了四位优秀的女高音演唱的同一首咏叹调,举例说明在曲目中所包含的较低音域中她们对于胸声的运用。同时分别介绍了她们的声乐训练、重要的表演经验,以及演唱所选咏叹调的较低音域的方法。根据Voce Vista (可视语音)的功率谱的数据分析,从而获取不同的录音中收集到的客观具体数据,来确认作者对于所选女高音演唱方面的观点。展开更多
基金Supported by National Natural Science Foundation of China (Grant Nos.12202205,U1730101)the Federal Ministry of Economic Affairs and Energy (BMWi)via the German Federation of Industrial Research Associations‘Otto von Guericke’e.V. (AiF) (IGF-Nr.19567N)Forschungsvereinigung Automobiltechnik e.V. (FAT)。
文摘Cast iron alloys with low production cost and quite good mechanical properties are widely used in the automotive industry.To study the mechanical behavior of a typical ductile cast iron(GJS-450)with nodular graphite,uni-axial quasi-static and dynamic tensile tests at strain rates of 10^(-4),1,10,100,and 250 s^(-1)were carried out.In order to investigate the influence of stress state on the deformation and fracture parameters,specimens with various geometries were used in the experiments.Stress strain curves and fracture strains of the GJS-450 alloy in the strain rate range of 10^(-4)to 250 s^(-1)were obtained.A strain rate-dependent plastic flow model was proposed to describe the mechanical behavior in the corresponding strain-rate range.The available damage model was extended to take the strain rate into account and calibrated based on the analysis of local fracture strains.Simulations with the proposed plastic flow model and the damage model were conducted to observe the deformation and fracture process.The results show that the strain rate has obviously nonlinear effects on the yield stress and fracture strain of GJS-450 alloys.The predictions with the proposed plastic flow and damage models at various strain rates agree well with the experimental results,which illustrates that the rate-dependent plastic flow and damage models can be used to describe the mechanical behavior of cast iron alloys at elevated strain rates.The proposed plastic flow and damage models can be used to describe the deformation and fracture analysis of materials with similar properties.
文摘歌剧作曲家罗西尼是19世纪意大利的音乐天才,仅用十三天完成的歌剧《塞维利亚理发师》是喜歌剧最经典的代表作。这部歌剧的原型出自法国作家博马舍于1775年所写的剧本,原名《Le Barbier de Séville》。故事延续自博马舍的剧本《费加罗的婚礼》,而莫扎特于1786年作曲的同名歌剧即是基于此而写的。本文拟对《塞维利亚理发师》这部歌剧和剧中罗西娜的咏叹调《美妙的歌声随风荡漾》(Una voce poco fa{II Barbiere di Siviglia})做个简单的介绍,对罗西尼的创作特点和音乐风格进行粗浅的探究,对这首咏叹调的音乐进行较详细的分析,并谈谈本人演唱这首咏叹调的体会。
文摘30CrMnSiA合金钢的室温成形性能差,为探究30CrMnSiA材料电流辅助成形的可行性,基于不同试验参数的电流辅助拉伸试验,研究了温度及脉冲电流参数(电流密度、脉冲占空比和频率)对30CrMnSiA流动应力的影响规律。研究表明:30CrMnSiA的强度及伸长率随温度及电流密度的升高而下降,受脉冲占空比和频率影响不大;脉冲电流能抑制动态应变时效的强化作用,并促进碳化物的析出,使材料塑性下降。基于Voce模型基础,建立了考虑应变速率、温度及脉冲电流参数影响的30Cr Mn Si A电流辅助流动应力模型。利用该模型计算的结果与试验值吻合较好,说明该模型能准确预测材料在电流辅助条件下的流动应力。
基金Item Sponsored by National Natural Science Foundation of China(51274036)
文摘Two kinds of steels （YP960 and YP690） with low carbon bainite structure were designed, and their flow stress and strain hardening exponents were studied. The results showed that, when Hollomon relation was applied to descrihe the flow stress, there were significanl errors between the experimental and calculated points in specimens tempered below 400 ℃, while a high precision was ohserved in samples tempered above 400℃. Whereas, the modijied Voce relation could effectively predici the flow stress as well as the strain hardening exponent at different tempe ring temperatures, which was verified by unbiased estimators such as maximum relative error （MRXE） and average ahsolute relative error （AARE）. Besides, the modified Voee relation was also applied to estimate the maximum uniform strain, and the correlation coefficients （R） between the experimental data and calculated maximum uniform strain were more than 0.91. The high correlation coefficients indicated that the modified Vote relation could effec lively predict the uniform deformation ability of high strength steels with low carbon bainite structure at different tempering temperatures.
基金financially supported by the National Natural Science Foundation of China (Nos. 51471031 and U1660115)the State Key Laboratory for Advanced Metals and Materials, China (No. 2016Z-17)the Program of Introducing Talents of Discipline to Universities, China (No. BP0719004)
文摘The effect of anodic polarization on the plastic deformation behavior and formability of FeSi6.5 steel at room temperature was experimentally investigated through uniaxial tensile and drawing of wire specimen in sulfuric acid solution with current densities of 0-40 mA/cm2.The formability of the FeSi6.5 steel was significantly improved after the anodic polarization.The plastic elongation of the specimen as an anode in the electrochemical environment was 4.4%-7%,but 2.7%in the air.The drawing force under the anodic polarization decreased by 12.5%-26%compared to that in deionized water.The softening is mainly attributed to the relief in work hardening caused by surface atomic dissolution.The work hardening mechanism of the FeSi6.5 steel wires under anodic polarization condition was analyzed using Hollomon equation and Voce relation combined with the Kocks-Mecking approach.These data support the view that the surface atom dissolution facilitates dislocation slip.FeSi6.5 steel wires were obtained using electrochemical cold drawing and presented a smooth surface and good ductility without crack after five-pass drawing with a total cross-section area reduction of 88%.The drawing with the assistance of anodic polarization is a promising technology for processing hard and brittle metal materials.
文摘自20世纪初录音设备应用于记录演唱以来,不同时代的女高音曲目有大量的录音档案,它们是研究和分析100多年来歌手们对音乐的独特诠释的宝贵资源。同时,声乐科学为声乐教学提供了更新的应用,如功率谱和电声门图。通过主观的听觉感知对录音进行分析,由于个体感官的差异,结果可能不太可靠,而这些仪器都是客观和直接地来分析声乐信号,研究声乐发声原理,并帮助声乐教师处理复杂的声乐问题的方法。文章根据20世纪至今的四个录音时期,选择了四位优秀的女高音演唱的同一首咏叹调,举例说明在曲目中所包含的较低音域中她们对于胸声的运用。同时分别介绍了她们的声乐训练、重要的表演经验,以及演唱所选咏叹调的较低音域的方法。根据Voce Vista (可视语音)的功率谱的数据分析,从而获取不同的录音中收集到的客观具体数据,来确认作者对于所选女高音演唱方面的观点。
