The effects of second phases on the fracture behavior of Mg-10Gd-3Y-0.6Zr alloy were investigated.The results show that the fracture mode can be generally described as ductile transgranular fracture in as-extruded con...The effects of second phases on the fracture behavior of Mg-10Gd-3Y-0.6Zr alloy were investigated.The results show that the fracture mode can be generally described as ductile transgranular fracture in as-extruded condition and intergranular fracture in peak-aged condition.In as-extruded condition,the ductile transgranular fracture occurs by the formation and transgranular propagation of the microcrack from the broken primary phases.However,as the collaboration effects of precipitates inside grains and on the grain boundaries have the tendency to reduce the cohesive strength of the grain boundary,and make the grain boundaries the favorable path for crack propagation,the intergranular fracture occurs in peak-aged condition.展开更多
To investigate the influence of loading rate and high temperature on the dynamic fracture toughness of rock,dynamic fracture tests were carried out on notched semi-circular bend specimens under four temperature condit...To investigate the influence of loading rate and high temperature on the dynamic fracture toughness of rock,dynamic fracture tests were carried out on notched semi-circular bend specimens under four temperature conditions based on the split Hopkinson pressure bar system.Experimental and analytical methods were applied to investigating the effect of temperature gradient on the stress waves.A high-speed camera was used to check the fracture characteristics of the specimens.The results demonstrate that the temperature gradient on the bars will not significantly distort the shape of the stress wave.The dynamic force balance is achieved even when the specimens are at a temperature of 400°C.The dynamic fracture toughness linearly develops with the increase of loading rate within the temperature range of 25-400°C,and high temperature has a strengthening effect on the dynamic fracture toughness.展开更多
Here, we present the case of a 53-year-old man with a hepatothorax due to a right diaphragmatic rupture related to duodenal ulcer perforation. On admission, the patient complained of severe acute abdominal pain, with ...Here, we present the case of a 53-year-old man with a hepatothorax due to a right diaphragmatic rupture related to duodenal ulcer perforation. On admission, the patient complained of severe acute abdominal pain, with physical examination findings suspicious for a perforated peptic ulcer. Of note, the patient had no history of other medical conditions or recent trauma, and the initial chest radiography and laboratory findings were not specific. A subsequent abdominal computed tomography revealed intrathoracic displacement of the liver, gallbladder, transverse colon and omentum through a right diaphragmatic defect. The patient then underwent an explorative laparotomy that confirmed duodenal ulcer perforation. A primary repair of the duodenal perforation was performed, and the diaphrag-matic defect was repaired using a polytetrafluoroeth-ylene patch after the organs were reduced and the cavity irrigated. This particular case proves interesting as right-sided spontaneous diaphragmatic ruptures are very rare and difficult to diagnose. Additionally, the best treatment for such large diaphragmatic defects is still controversial, especially in cases of intrathoracic or intra-abdominal contamination.展开更多
Two hours after the 2010 Yushu Earthquake, the shaking intensity distribution was obtained using the ShakeMap Rapid Generation System Based on Site Effects, developed by the author, which integrates the information of...Two hours after the 2010 Yushu Earthquake, the shaking intensity distribution was obtained using the ShakeMap Rapid Generation System Based on Site Effects, developed by the author, which integrates the information of tectonic settings, the strike and scale of causative faults, focal mechanism solutions, fault rupture process and attenuation relationship in Western China, as well as local site effects. The results are as follows： （1） The major axis of shaking intensity distribution is directed NW-SE, parallel to the Yushu fault; （2） The meizoseismal area reaches an intensity IX and covers 300km^2; （3） The intensity IX area is mainly distributed in the area 40km southeast and 15km northwest of the epicenter along the causative fault; （4） Due to local soil conditions, the northwestern part of the area with intensity IX on bedrock shows an intensity Ⅷ when converting from the bedrock to the soil; （5） Areas with intensity Ⅷ, VII, VI measure 3,000km^2, 8,000km^2, and 24,000km^2, respectively.展开更多
Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bend...Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.展开更多
Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture beha...Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.展开更多
基金Project(IRT0713)supported by the Program for Changjiang Scholars and Innovative Research Team in Chinese UniversityProjects(2007CB613701,2007CB613702)supported by National Basic Research Program of China
文摘The effects of second phases on the fracture behavior of Mg-10Gd-3Y-0.6Zr alloy were investigated.The results show that the fracture mode can be generally described as ductile transgranular fracture in as-extruded condition and intergranular fracture in peak-aged condition.In as-extruded condition,the ductile transgranular fracture occurs by the formation and transgranular propagation of the microcrack from the broken primary phases.However,as the collaboration effects of precipitates inside grains and on the grain boundaries have the tendency to reduce the cohesive strength of the grain boundary,and make the grain boundaries the favorable path for crack propagation,the intergranular fracture occurs in peak-aged condition.
基金support from the National Natural Science Foundation of China(No.41972283)。
文摘To investigate the influence of loading rate and high temperature on the dynamic fracture toughness of rock,dynamic fracture tests were carried out on notched semi-circular bend specimens under four temperature conditions based on the split Hopkinson pressure bar system.Experimental and analytical methods were applied to investigating the effect of temperature gradient on the stress waves.A high-speed camera was used to check the fracture characteristics of the specimens.The results demonstrate that the temperature gradient on the bars will not significantly distort the shape of the stress wave.The dynamic force balance is achieved even when the specimens are at a temperature of 400°C.The dynamic fracture toughness linearly develops with the increase of loading rate within the temperature range of 25-400°C,and high temperature has a strengthening effect on the dynamic fracture toughness.
文摘Here, we present the case of a 53-year-old man with a hepatothorax due to a right diaphragmatic rupture related to duodenal ulcer perforation. On admission, the patient complained of severe acute abdominal pain, with physical examination findings suspicious for a perforated peptic ulcer. Of note, the patient had no history of other medical conditions or recent trauma, and the initial chest radiography and laboratory findings were not specific. A subsequent abdominal computed tomography revealed intrathoracic displacement of the liver, gallbladder, transverse colon and omentum through a right diaphragmatic defect. The patient then underwent an explorative laparotomy that confirmed duodenal ulcer perforation. A primary repair of the duodenal perforation was performed, and the diaphrag-matic defect was repaired using a polytetrafluoroeth-ylene patch after the organs were reduced and the cavity irrigated. This particular case proves interesting as right-sided spontaneous diaphragmatic ruptures are very rare and difficult to diagnose. Additionally, the best treatment for such large diaphragmatic defects is still controversial, especially in cases of intrathoracic or intra-abdominal contamination.
文摘Two hours after the 2010 Yushu Earthquake, the shaking intensity distribution was obtained using the ShakeMap Rapid Generation System Based on Site Effects, developed by the author, which integrates the information of tectonic settings, the strike and scale of causative faults, focal mechanism solutions, fault rupture process and attenuation relationship in Western China, as well as local site effects. The results are as follows： （1） The major axis of shaking intensity distribution is directed NW-SE, parallel to the Yushu fault; （2） The meizoseismal area reaches an intensity IX and covers 300km^2; （3） The intensity IX area is mainly distributed in the area 40km southeast and 15km northwest of the epicenter along the causative fault; （4） Due to local soil conditions, the northwestern part of the area with intensity IX on bedrock shows an intensity Ⅷ when converting from the bedrock to the soil; （5） Areas with intensity Ⅷ, VII, VI measure 3,000km^2, 8,000km^2, and 24,000km^2, respectively.
基金financially supported by the National Natural Science Foundation of China (No.51374139)the Natural Science Foundation of Shandong Province (No.ZR2013EEM018)the Scientific Research Innovation Team Support Plan of Shandong University of Science and Technology
文摘Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.
文摘Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.
