In the framework of the finite deformation theory, the plastic collapse analysis of thin-walled pipes subjected to the internal pressure is conducted on the basis of the unified strength criterion （USC）. An analytic...In the framework of the finite deformation theory, the plastic collapse analysis of thin-walled pipes subjected to the internal pressure is conducted on the basis of the unified strength criterion （USC）. An analytical solution of the burst pressure for pipes with capped ends is derived, which includes the strength differential effect and takes the influence of strength criterion on the burst pressure into account. In addition, a USC- based analytical solution of the burst pressure for end-opened pipes under the internal pressure is obtained. By discussion, it is found that for the end-capped pipes, the influence of different yield criteria and the strength differential effect on the burst pressure are significant, while for the end-opened pipes, the burst pressure is independent of the specific form of the strength criterion and strength difference in tension and compression.展开更多
The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-...The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.展开更多
According to the reliability of material strength,the optimal design for the cross sectional size of thin walled box beam was studied.Firstly the cross sectional size as design random variable was determined,then its...According to the reliability of material strength,the optimal design for the cross sectional size of thin walled box beam was studied.Firstly the cross sectional size as design random variable was determined,then its stochastic nature was researched,with which the objective function is to seek the maximum reliability of the beam under given constraint conditions.This way is not the same as the conventional optimal design for the minimum weight of the material.With establishing the optimal objective,the reliability of the material under conditions of static and fatigue was considered.The corresponding calculated expressions are given.Normally the cross section sizes are fitted to the normal distribution,for the simplification of the design variable,the variation of the section size is assumed as a dependent variable proportional to the mean of the size.The way is different not only with the conventional optimal design but also with the common reliability design.The maximum reliability of material is obtained,meanwhile the area of the cross section is reduced,i.e.,the weight of the material is decreased.展开更多
目的 基于高分辨率磁共振血管壁成像和计算流体动力学技术,探讨大脑中动脉(MCA)粥样硬化性狭窄处斑块陡度与血流动力学的关系。方法收集80例缺血性脑卒中、短暂性脑缺血发作且单侧动脉粥样硬化性MCA狭窄的患者(50%~99%)进行进行常规磁...目的 基于高分辨率磁共振血管壁成像和计算流体动力学技术,探讨大脑中动脉(MCA)粥样硬化性狭窄处斑块陡度与血流动力学的关系。方法收集80例缺血性脑卒中、短暂性脑缺血发作且单侧动脉粥样硬化性MCA狭窄的患者(50%~99%)进行进行常规磁共振扫描及大脑中动脉狭窄处血管壁扫描。获得斑块、血管壁、血管壁剪切力比(WSSR)、狭窄处血管壁剪切力(WSS)的数值。根据有无缺血性脑卒中将患者分为有症状组和无症状组。比较两组在斑块、血管壁和血流动力学方面的差异。计算斑块陡度与血流动力学之间的相关性。结果80例患者中症状组31例,无症状组49例。症状组较无症状组狭窄处管腔面积(LA)较小(2.33±1.12 VS 2.94±1.06,P=0.024),斑块面积(PA)较大(4.36.±2.13 VS 2.87±1.38,P=0.001),重构指数较大(1.13±0.21 VS 0.92±0.19,P=0.001),WSSR(9.93,8.42 VS 5.75,3.68,P=0.009)和WSS(52.41±16.92 VS 38.37±17.26,P=0.018)较高,斑块陡度(1.24,1.17 VS 0.94,0.91,P=0.014)较大。与无症状组相比,症状组有更多的强化斑块(24vs 13,P=0.03),正性重构(23vs20,P=0.001)。斑块陡度与WSSR呈正相关(r=0.879,P<0.001)。结论斑块陡度是MCA粥样硬化斑块的一个重要特征,在以往的研究中未引起足够的重视。大的斑块陡度更容易引起脑卒中。展开更多
为合理调节或优化传统钢板剪力墙(steel plate shear wall,SPSW)的抗震性能,本文提出了一种新型的带圆形压痕的钢板剪力墙结构(steel plate shear wall with circle dents,SPSW-CD)。基于有限元方法系统研究了压痕孔径、压痕孔距、压痕...为合理调节或优化传统钢板剪力墙(steel plate shear wall,SPSW)的抗震性能,本文提出了一种新型的带圆形压痕的钢板剪力墙结构(steel plate shear wall with circle dents,SPSW-CD)。基于有限元方法系统研究了压痕孔径、压痕孔距、压痕深度、钢板厚度和钢材强度等参数对SPSW-CD抗侧性能的影响,提出了四边连接SPSW-CD抗侧刚度及水平承载力的简化计算公式。分析结果表明随着压痕孔径增加,SPSW-CD的初始抗侧刚度及水平承载力均呈降低趋势;压痕孔距及钢板厚度越大,SPSW-CD抗侧性能越优。随着钢材强度增加,SPSW-CD水平承载力呈明显的增大趋势,但对其抗侧刚度影响不明显。压痕深度对SPSW-CD抗侧性能的影响可忽略。SPSW-CD抗侧刚度及水平承载力计算公式计算误差均小于10%,研究成果可用于此类结构的工程设计。展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 51079128 and11172265)the Natural Science Foundation of Zhejiang Province of China (No. Y1101107)
文摘In the framework of the finite deformation theory, the plastic collapse analysis of thin-walled pipes subjected to the internal pressure is conducted on the basis of the unified strength criterion （USC）. An analytical solution of the burst pressure for pipes with capped ends is derived, which includes the strength differential effect and takes the influence of strength criterion on the burst pressure into account. In addition, a USC- based analytical solution of the burst pressure for end-opened pipes under the internal pressure is obtained. By discussion, it is found that for the end-capped pipes, the influence of different yield criteria and the strength differential effect on the burst pressure are significant, while for the end-opened pipes, the burst pressure is independent of the specific form of the strength criterion and strength difference in tension and compression.
基金Funded by the "11th Five" National Science and Technology Support Project(No.2006BAE03A13)
文摘The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.
文摘According to the reliability of material strength,the optimal design for the cross sectional size of thin walled box beam was studied.Firstly the cross sectional size as design random variable was determined,then its stochastic nature was researched,with which the objective function is to seek the maximum reliability of the beam under given constraint conditions.This way is not the same as the conventional optimal design for the minimum weight of the material.With establishing the optimal objective,the reliability of the material under conditions of static and fatigue was considered.The corresponding calculated expressions are given.Normally the cross section sizes are fitted to the normal distribution,for the simplification of the design variable,the variation of the section size is assumed as a dependent variable proportional to the mean of the size.The way is different not only with the conventional optimal design but also with the common reliability design.The maximum reliability of material is obtained,meanwhile the area of the cross section is reduced,i.e.,the weight of the material is decreased.
文摘目的 基于高分辨率磁共振血管壁成像和计算流体动力学技术,探讨大脑中动脉(MCA)粥样硬化性狭窄处斑块陡度与血流动力学的关系。方法收集80例缺血性脑卒中、短暂性脑缺血发作且单侧动脉粥样硬化性MCA狭窄的患者(50%~99%)进行进行常规磁共振扫描及大脑中动脉狭窄处血管壁扫描。获得斑块、血管壁、血管壁剪切力比(WSSR)、狭窄处血管壁剪切力(WSS)的数值。根据有无缺血性脑卒中将患者分为有症状组和无症状组。比较两组在斑块、血管壁和血流动力学方面的差异。计算斑块陡度与血流动力学之间的相关性。结果80例患者中症状组31例,无症状组49例。症状组较无症状组狭窄处管腔面积(LA)较小(2.33±1.12 VS 2.94±1.06,P=0.024),斑块面积(PA)较大(4.36.±2.13 VS 2.87±1.38,P=0.001),重构指数较大(1.13±0.21 VS 0.92±0.19,P=0.001),WSSR(9.93,8.42 VS 5.75,3.68,P=0.009)和WSS(52.41±16.92 VS 38.37±17.26,P=0.018)较高,斑块陡度(1.24,1.17 VS 0.94,0.91,P=0.014)较大。与无症状组相比,症状组有更多的强化斑块(24vs 13,P=0.03),正性重构(23vs20,P=0.001)。斑块陡度与WSSR呈正相关(r=0.879,P<0.001)。结论斑块陡度是MCA粥样硬化斑块的一个重要特征,在以往的研究中未引起足够的重视。大的斑块陡度更容易引起脑卒中。
文摘为合理调节或优化传统钢板剪力墙(steel plate shear wall,SPSW)的抗震性能,本文提出了一种新型的带圆形压痕的钢板剪力墙结构(steel plate shear wall with circle dents,SPSW-CD)。基于有限元方法系统研究了压痕孔径、压痕孔距、压痕深度、钢板厚度和钢材强度等参数对SPSW-CD抗侧性能的影响,提出了四边连接SPSW-CD抗侧刚度及水平承载力的简化计算公式。分析结果表明随着压痕孔径增加,SPSW-CD的初始抗侧刚度及水平承载力均呈降低趋势;压痕孔距及钢板厚度越大,SPSW-CD抗侧性能越优。随着钢材强度增加,SPSW-CD水平承载力呈明显的增大趋势,但对其抗侧刚度影响不明显。压痕深度对SPSW-CD抗侧性能的影响可忽略。SPSW-CD抗侧刚度及水平承载力计算公式计算误差均小于10%,研究成果可用于此类结构的工程设计。
