This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the pre...This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%,the bonding between layers is established.In this research,the roll bonding process was done at room temperature,without the use of lubricants and with a 70%thickness reduction.Then,the final thickness of the Ag/Al bilayer sheet reached 350μm by several stages of cold rolling.Before cold rolling,it should be noted that to decrease the hardness created due to plastic deformation,the roll-bonded samples were subjected to annealing heat treatment at 400℃for 90 min.Thus,the final samples were annealed at 200,300 and 400℃for 90 min and cooled in a furnace to examine the annealing temperature effects.The uniaxial tensile and microhardness tests measured mechanical properties.Also,to investigate the fracture mechanism,the fractography of the cross-section was examined by scanning electron microscope(SEM).To evaluate the formability of Ag/Al bilayer sheets,forming limit curves were obtained experimentally through the Nakazima test.The resistance of composites to failure due to cracking was also investigated by fracture toughness.The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness.However,the changing trend is not the same at different temperatures,and according to the results,the most significant effect is obtained at 300℃and aluminum layers.It was also determined that by increasing annealing temperature,the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.展开更多
Porous materials can be found in a variety of geophysical and engineering applications.The existence of thermal contact resistance at the interface between bilayered saturated porous strata would result in a significa...Porous materials can be found in a variety of geophysical and engineering applications.The existence of thermal contact resistance at the interface between bilayered saturated porous strata would result in a significant temperature difference at the interface.An attempt is made to study the thermo-hydro-mechanical coupling dynamic response of bilayered saturated porous strata with thermal contact resistance and elastic wave impedance.The corresponding analytical solutions for the dynamic response of bilayered saturated porous strata under a harmonic thermal load are derived by the operator decomposition method,and their rationality is verified by comparing them with existing solutions.The influences of thermal contact resistance,thermal conductivity ratio,and porosity ratio on the dynamic response of bilayered saturated porous strata are systematically investigated.Outcomes disclose that with the increase of thermal contact resistance,the displacement,pore water pressure and stress decrease gradually,and the temperature jump at the interface between two saturated porous strata increases.展开更多
针对区域配网变压器(简称“配变”)数量多,大量新型负荷、分布式光伏等接入,配变电压随机性波动增强,台区用户电压质量面临挑战。为更好地对区域配变电压进行越限特征分析及预测,提出了基于关联特征筛选的双层聚类区域配变电压预测方法...针对区域配网变压器(简称“配变”)数量多,大量新型负荷、分布式光伏等接入,配变电压随机性波动增强,台区用户电压质量面临挑战。为更好地对区域配变电压进行越限特征分析及预测,提出了基于关联特征筛选的双层聚类区域配变电压预测方法。首先,将区域配变的越限天数作为第一层聚类特征,获得电压性质正常以及越上限的配变。其次,针对电压越限配变提出结合Pearson相关系数和欧氏距离(Euclidean distance)的最优度量矩阵,提取原有数据的内含信息,作为K均值聚类(K-means)的输入,实现对区域配变双层聚类。在此基础上,选取该集群中代表配变表征该类配变,利用卷积双向长短期记忆网络-注意力机制(convolutional neural network-bidirectional long and short-term memory-attention,CNN-BiLSTM-Attention)模型对配变电压进行预测,该模型能够提取输入数据的双向信息特征,并对重要特征加权,从多时间尺度上获得双向特征信息用于预测。最后,在上海市某区域配变验证了该方法的有效性。展开更多
基金Project(4013311)supported by the National Science Foundation of Iran(INSF)。
文摘This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%,the bonding between layers is established.In this research,the roll bonding process was done at room temperature,without the use of lubricants and with a 70%thickness reduction.Then,the final thickness of the Ag/Al bilayer sheet reached 350μm by several stages of cold rolling.Before cold rolling,it should be noted that to decrease the hardness created due to plastic deformation,the roll-bonded samples were subjected to annealing heat treatment at 400℃for 90 min.Thus,the final samples were annealed at 200,300 and 400℃for 90 min and cooled in a furnace to examine the annealing temperature effects.The uniaxial tensile and microhardness tests measured mechanical properties.Also,to investigate the fracture mechanism,the fractography of the cross-section was examined by scanning electron microscope(SEM).To evaluate the formability of Ag/Al bilayer sheets,forming limit curves were obtained experimentally through the Nakazima test.The resistance of composites to failure due to cracking was also investigated by fracture toughness.The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness.However,the changing trend is not the same at different temperatures,and according to the results,the most significant effect is obtained at 300℃and aluminum layers.It was also determined that by increasing annealing temperature,the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.
基金Projects(52108347,52178371)supported by the National Natural Science Foundation of ChinaProject(LQ22E080010)supported by the Exploring Youth Project of Zhejiang Natural Science Foundation,China。
文摘Porous materials can be found in a variety of geophysical and engineering applications.The existence of thermal contact resistance at the interface between bilayered saturated porous strata would result in a significant temperature difference at the interface.An attempt is made to study the thermo-hydro-mechanical coupling dynamic response of bilayered saturated porous strata with thermal contact resistance and elastic wave impedance.The corresponding analytical solutions for the dynamic response of bilayered saturated porous strata under a harmonic thermal load are derived by the operator decomposition method,and their rationality is verified by comparing them with existing solutions.The influences of thermal contact resistance,thermal conductivity ratio,and porosity ratio on the dynamic response of bilayered saturated porous strata are systematically investigated.Outcomes disclose that with the increase of thermal contact resistance,the displacement,pore water pressure and stress decrease gradually,and the temperature jump at the interface between two saturated porous strata increases.
文摘针对区域配网变压器(简称“配变”)数量多,大量新型负荷、分布式光伏等接入,配变电压随机性波动增强,台区用户电压质量面临挑战。为更好地对区域配变电压进行越限特征分析及预测,提出了基于关联特征筛选的双层聚类区域配变电压预测方法。首先,将区域配变的越限天数作为第一层聚类特征,获得电压性质正常以及越上限的配变。其次,针对电压越限配变提出结合Pearson相关系数和欧氏距离(Euclidean distance)的最优度量矩阵,提取原有数据的内含信息,作为K均值聚类(K-means)的输入,实现对区域配变双层聚类。在此基础上,选取该集群中代表配变表征该类配变,利用卷积双向长短期记忆网络-注意力机制(convolutional neural network-bidirectional long and short-term memory-attention,CNN-BiLSTM-Attention)模型对配变电压进行预测,该模型能够提取输入数据的双向信息特征,并对重要特征加权,从多时间尺度上获得双向特征信息用于预测。最后,在上海市某区域配变验证了该方法的有效性。
