N-type Si-based type-Ⅰ clathrates with different Ga content were synthesized by combining the solid-state reaction method,melting method and spark plasma sintering （SPS） method.The effects of Ga composition on high...N-type Si-based type-Ⅰ clathrates with different Ga content were synthesized by combining the solid-state reaction method,melting method and spark plasma sintering （SPS） method.The effects of Ga composition on high temperature thermoelectric transport properties were investigated.The results show that at room temperature,the carrier concentration decreases, while the carrier mobility increases slightly with increasing Ga content.The Seebeck coefficient increases with increasing Ga content. Among all the samples,Ba7.93Ga17.13Si28.72exhibits higher Seebeck coefficient than the others and reaches -135μV·K^-1 at 1000 K.The sample prepared by this method exhibits very high electrical conductivity,and reaches 1.95x 10^5 S·m^-1 for Ba8.01Ga16.61Si28.93 at room temperature.The thermal conductivity of all samples is almost temperature independent in the temperature range of 300-1000 K,indicating the behaviour of a typical metal.The maximum ZT value of 0.75 is obtained at 1000 K for the compound Ba7.93Ga17.13Si28.72.展开更多
In order to simultaneously measure the initiation toughness of pure mode Ⅰ and mode Ⅱ cracks in one specimen,a large-size double-cracked concave-convex plate(DCCP)specimen configuration was proposed.Impacting tests ...In order to simultaneously measure the initiation toughness of pure mode Ⅰ and mode Ⅱ cracks in one specimen,a large-size double-cracked concave-convex plate(DCCP)specimen configuration was proposed.Impacting tests were implemented in the drop plate impact device.Strain gauges were employed to measure impact loads and crack initiation time.The corresponding numerical model was established by using the dynamic finite difference program AUTODYN,and the experimental-numerical method and ABAQUS code were utilized to obtain the initial fracture toughness of the crack.Using experiments and numerical research,we concluded that the DCCP specimen is suitable for measuring the initial fracture toughness of pure mode Ⅰ and mode Ⅱ cracks at the same time;the dynamic initiation toughness increases with the increase of loading rate and the crack initiation time decreases with increasing loading rate;the initiation toughness of mode Ⅱ crack is 0.5 times that of mode Ⅰ crack when subjected to the same loading rate.For the pre-crack in the vicinity of the bottom of a sample,when its length increases from 20 to 100 mm,the dynamic initiation toughness of the pure mode Ⅰ crack gradually decreases,and the longer the lower crack length is,the easier the crack would initiate,but the dynamic initiation toughness of pure mode Ⅱ crack varies little.展开更多
Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution...Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution,the material behaved hydrogen embrittlement in all the cases studied.The threshold K_(ⅡH)/K_(ⅡX) of HIC under mode Ⅱ load- ing was 0.27,which was nearly the same as that K(ⅠH)/K_(ⅠX)=0.29 under mode Ⅰ loading. While the thresholds of-HIC under(Ⅰ+Ⅱ)mixed mode loading were 0.36,0.41 and 0.37 cor- responding to the K_Ⅱ/K_Ⅰ ratio of 0.27,0.4 and O.81.The results show that simple mode Ⅰ or mode Ⅱ loading is more susceptible to hydrogen embrittlement than(Ⅰ+Ⅱ)mixed mode. For explaining the experimental results,the effects of triaxial stress as well as plastic deformation ahead of crack tip has been discussed.展开更多
Detailed investigations on the filamentary structures associated with the type-I edge-localized modes（ELMs） should be helpful for protecting the materials of a plasma-facing wall on a future large device.Related exp...Detailed investigations on the filamentary structures associated with the type-I edge-localized modes（ELMs） should be helpful for protecting the materials of a plasma-facing wall on a future large device.Related experiments have been carefully conducted in the Experimental Advanced Superconducting Tokamak（EAST） using combined Langmuir-magnetic probes.The experimental results indicate that the radially outward velocity of type-I ELMy filaments can be up to 1.7 kms^（-1） in the far scrape-off layer（SOL） region.It is remarkable that the electron temperature of these filaments is detected to be ~50eV,corresponding to a fraction of 1/6 to the temperature near the pedestal top,while the density ~3×10^（19）m^（-3） of these filaments could be approximate to the line-averaged density.In addition,associated magnetic fluctuations have been clearly observed at the same time,which show good agreement with the density perturbations.A localized current on the order of ~100kA could be estimated within the filaments.展开更多
文摘工程结构在制造工艺过程中或使用期间会产生裂纹,对结构断裂路径的预测和研究是防治工程安全问题发生的重要手段。在考虑裂纹尖端应力场常数项T应力的基础上对传统的最大周向应力准则(Maximum tangential stress criterion,MTS)和最小应变能密度因子准则(Minimum strain energy density criterion,SED)进行修正,采用Python语言对ABAQUS的前、后处理和有限元计算模块进行二次开发,通过计算最优解的粒子群算法(Particle swarm optimization,PSO)将修正后的准则编入裂纹自动扩展程序脚本中。利用上述二次开发程序对初始纯Ⅰ型裂纹的扩展路径进行模拟,结果表明:采用ABAQUS脚本程序模拟结果与相关文献实验结果吻合,表明了程序的有效性,进而实现考虑T应力的多种断裂准则对裂纹扩展路径的预测;当T应力值处于一定范围内时,修正的MTS准则无法预测裂纹发生的偏转现象,扩展路径呈直线,此时可采用修正的SED准则进行预测。
基金Project supported by the National Basic Research Program of China (Grant Nos 2007CB607501 and 2007CB607503)Yunnan Natural Science Fund (Grant No 2008CD114)
文摘N-type Si-based type-Ⅰ clathrates with different Ga content were synthesized by combining the solid-state reaction method,melting method and spark plasma sintering （SPS） method.The effects of Ga composition on high temperature thermoelectric transport properties were investigated.The results show that at room temperature,the carrier concentration decreases, while the carrier mobility increases slightly with increasing Ga content.The Seebeck coefficient increases with increasing Ga content. Among all the samples,Ba7.93Ga17.13Si28.72exhibits higher Seebeck coefficient than the others and reaches -135μV·K^-1 at 1000 K.The sample prepared by this method exhibits very high electrical conductivity,and reaches 1.95x 10^5 S·m^-1 for Ba8.01Ga16.61Si28.93 at room temperature.The thermal conductivity of all samples is almost temperature independent in the temperature range of 300-1000 K,indicating the behaviour of a typical metal.The maximum ZT value of 0.75 is obtained at 1000 K for the compound Ba7.93Ga17.13Si28.72.
基金Projects(U19A2098,1210021843)supported by the National Natural Science Foundation of ChinaProject(2021SCU12130)supported by Fundamental Research Funds for the Central Universities,China+1 种基金Project(2021YJ0511)supported by the Sichuan Science and Technology Program,ChinaProjects(DESEYU202205,DESE202005)supported by the Open Fund of Key Laboratory of Deep Earth Science and Engineering,China。
文摘In order to simultaneously measure the initiation toughness of pure mode Ⅰ and mode Ⅱ cracks in one specimen,a large-size double-cracked concave-convex plate(DCCP)specimen configuration was proposed.Impacting tests were implemented in the drop plate impact device.Strain gauges were employed to measure impact loads and crack initiation time.The corresponding numerical model was established by using the dynamic finite difference program AUTODYN,and the experimental-numerical method and ABAQUS code were utilized to obtain the initial fracture toughness of the crack.Using experiments and numerical research,we concluded that the DCCP specimen is suitable for measuring the initial fracture toughness of pure mode Ⅰ and mode Ⅱ cracks at the same time;the dynamic initiation toughness increases with the increase of loading rate and the crack initiation time decreases with increasing loading rate;the initiation toughness of mode Ⅱ crack is 0.5 times that of mode Ⅰ crack when subjected to the same loading rate.For the pre-crack in the vicinity of the bottom of a sample,when its length increases from 20 to 100 mm,the dynamic initiation toughness of the pure mode Ⅰ crack gradually decreases,and the longer the lower crack length is,the easier the crack would initiate,but the dynamic initiation toughness of pure mode Ⅱ crack varies little.
文摘Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution,the material behaved hydrogen embrittlement in all the cases studied.The threshold K_(ⅡH)/K_(ⅡX) of HIC under mode Ⅱ load- ing was 0.27,which was nearly the same as that K(ⅠH)/K_(ⅠX)=0.29 under mode Ⅰ loading. While the thresholds of-HIC under(Ⅰ+Ⅱ)mixed mode loading were 0.36,0.41 and 0.37 cor- responding to the K_Ⅱ/K_Ⅰ ratio of 0.27,0.4 and O.81.The results show that simple mode Ⅰ or mode Ⅱ loading is more susceptible to hydrogen embrittlement than(Ⅰ+Ⅱ)mixed mode. For explaining the experimental results,the effects of triaxial stress as well as plastic deformation ahead of crack tip has been discussed.
基金supported by National Natural Science Foundation of China under Contracts Nos.11275047,11705128,11422546,11575235,11575236 and 11505222Key Research Program of Frontier Sciences,CAS,Grant No.QYZDB-SSWSLH001National Magnetic Confinement Fusion Science Program of China under Contract Nos.2015GB101000 and 2013GB107003
文摘Detailed investigations on the filamentary structures associated with the type-I edge-localized modes（ELMs） should be helpful for protecting the materials of a plasma-facing wall on a future large device.Related experiments have been carefully conducted in the Experimental Advanced Superconducting Tokamak（EAST） using combined Langmuir-magnetic probes.The experimental results indicate that the radially outward velocity of type-I ELMy filaments can be up to 1.7 kms^（-1） in the far scrape-off layer（SOL） region.It is remarkable that the electron temperature of these filaments is detected to be ~50eV,corresponding to a fraction of 1/6 to the temperature near the pedestal top,while the density ~3×10^（19）m^（-3） of these filaments could be approximate to the line-averaged density.In addition,associated magnetic fluctuations have been clearly observed at the same time,which show good agreement with the density perturbations.A localized current on the order of ~100kA could be estimated within the filaments.
