This study experimentally and numerically investigated the effect of pulsatile flow of different frequencies and outflow resistance on wall deformation in a lateral aneurysm.A method for constructing a flexible aneury...This study experimentally and numerically investigated the effect of pulsatile flow of different frequencies and outflow resistance on wall deformation in a lateral aneurysm.A method for constructing a flexible aneurysm model was developed,and a self-designed piston pump was used to provide the pulsatile flow conditions.A fluid-structure interaction simulation was applied for comparison with and analysis of experimental findings.The maximum wall displacement oscillation increased as the pulsation frequency and outflow resistance increased,especially at the aneurysm dome.There is an obvious circular motion of the vortex center accompanying the periodic inflow fluctuation,and the pressure at the aneurysm dome at peak flow increased as the pulsatile flow frequency and terminal flow resistance increased.These results could explain why abnormal blood flow with high frequency and high outflow resistance is one of the risk factors for aneurysm rupture.展开更多
Welded joint is a mechanical heterogeneous body, and mechanical heterogeneity has great effect on dynamic fracture behaviour of welded joints. In the present investigation, dynamic response curve and dynamic J-integra...Welded joint is a mechanical heterogeneous body, and mechanical heterogeneity has great effect on dynamic fracture behaviour of welded joints. In the present investigation, dynamic response curve and dynamic J-integral of practical undermatched welded joint and whole base and whole weld three-point-bend (TPB) models containing longitudinal crack are com- puted. Dynamic J-integral is evaluated using virtual crack extension (VCE) method and the computation is performed using MARC finite element code. Because of the effect of inertia, dynamic load response curve of computed model waves periodically. Dynamic J-integral evaluated by VCE method is path independent. The effect of inertia has little influence on dynamic J-integral curve. The value of dynamic J-integral of undermatched welded joint is lower than that of whole base metal and higher than that of whole weld metal. The results establish the foundation of safety evaluation for dynamic loaded welded structures.展开更多
Intentional solute segregation at grain boundary(GB)can effectively stabilize the nanograined alloys by reducing the excess energy and mobility of GB,but it usually works for binary alloys with sufficient GB segregati...Intentional solute segregation at grain boundary(GB)can effectively stabilize the nanograined alloys by reducing the excess energy and mobility of GB,but it usually works for binary alloys with sufficient GB segregation tendency.Here,we found that the segregation of Cr can be enhanced in a nanostruc-tured Fe-8Cr alloy with insufficient GB segregation tendency through the interaction of another solute Si(1.0 wt.%).After surface mechanical grinding treatment and subsequent annealing,the nanograined Fe-8Cr-1Si is more thermally stable than the nanograined Fe-8Cr,which is mainly attributed to the Si-enhanced Cr segregation as observed by Super-X energy-dispersive X-ray spectroscopy(EDS)mapping system.With the grain refinement to nanoscale,the thermal stability is further improved due to the in-crease of Cr content at GBs and the precipitates formed at appropriate high temperatures.The present finding provides guidance for the development of advanced nanostructured ternary alloys.展开更多
The effect of compressive stress on the stability of reversed austenite in gNi steel was investigated by uni- axial and hydrostatic compression. It was found that the uniaxial compressive pressure promoted the Υ-α t...The effect of compressive stress on the stability of reversed austenite in gNi steel was investigated by uni- axial and hydrostatic compression. It was found that the uniaxial compressive pressure promoted the Υ-α transformation, while the hydrostatic pressure suppressed the -Υ-α transformation. The pressure dependent transformation behavior can be explained according to thermodynamic analysis.展开更多
Tensile tests were carried out on gradient nanograined copper samples to investigate the grain orientation dependence of mechanically induced grain boundary migration(GBM) process. The relationship between GBM and the...Tensile tests were carried out on gradient nanograined copper samples to investigate the grain orientation dependence of mechanically induced grain boundary migration(GBM) process. The relationship between GBM and the orientations of nanograins relative to loading direction was established by using electron backscatter diffraction. GBM is found to be more pronounced in the grains with higher Schmid factors where dislocations are easier to slip. As a result, the fraction of high angle grain boundaries decreases and that of low angle grain boundaries increases after GBM.展开更多
Deformation mechanisms of nanograined and submicron-grained pure cobalt processed by means of high strain rate shear deformation at cryogenic temperatures were studied.Microstructural analysis revealed a transition of...Deformation mechanisms of nanograined and submicron-grained pure cobalt processed by means of high strain rate shear deformation at cryogenic temperatures were studied.Microstructural analysis revealed a transition of governing deformation mechanism from deformation twinning and dislocation slip in submicron-grains to and dislocations slip in nanograins.Microhardness tests illustrated that the Hall-Petch relation slope changes consequently with the transition of deformation mechanism.展开更多
基金This study was supported by the National Natural Science Foundation of China(Grants 11602053 and 51576033)the Fundamental Research Funds for the Central Universities(Grant DUT18JC23).
文摘This study experimentally and numerically investigated the effect of pulsatile flow of different frequencies and outflow resistance on wall deformation in a lateral aneurysm.A method for constructing a flexible aneurysm model was developed,and a self-designed piston pump was used to provide the pulsatile flow conditions.A fluid-structure interaction simulation was applied for comparison with and analysis of experimental findings.The maximum wall displacement oscillation increased as the pulsation frequency and outflow resistance increased,especially at the aneurysm dome.There is an obvious circular motion of the vortex center accompanying the periodic inflow fluctuation,and the pressure at the aneurysm dome at peak flow increased as the pulsatile flow frequency and terminal flow resistance increased.These results could explain why abnormal blood flow with high frequency and high outflow resistance is one of the risk factors for aneurysm rupture.
基金National Natural Science Foundation of China(No.59501011)Science and Technology New Star Project of Beijing.
文摘Welded joint is a mechanical heterogeneous body, and mechanical heterogeneity has great effect on dynamic fracture behaviour of welded joints. In the present investigation, dynamic response curve and dynamic J-integral of practical undermatched welded joint and whole base and whole weld three-point-bend (TPB) models containing longitudinal crack are com- puted. Dynamic J-integral is evaluated using virtual crack extension (VCE) method and the computation is performed using MARC finite element code. Because of the effect of inertia, dynamic load response curve of computed model waves periodically. Dynamic J-integral evaluated by VCE method is path independent. The effect of inertia has little influence on dynamic J-integral curve. The value of dynamic J-integral of undermatched welded joint is lower than that of whole base metal and higher than that of whole weld metal. The results establish the foundation of safety evaluation for dynamic loaded welded structures.
基金supported by the Ministry of Science and Technology of the People’s Republic of China(Nos.2017YFA0204401,2017YFA0700700).
文摘Intentional solute segregation at grain boundary(GB)can effectively stabilize the nanograined alloys by reducing the excess energy and mobility of GB,but it usually works for binary alloys with sufficient GB segregation tendency.Here,we found that the segregation of Cr can be enhanced in a nanostruc-tured Fe-8Cr alloy with insufficient GB segregation tendency through the interaction of another solute Si(1.0 wt.%).After surface mechanical grinding treatment and subsequent annealing,the nanograined Fe-8Cr-1Si is more thermally stable than the nanograined Fe-8Cr,which is mainly attributed to the Si-enhanced Cr segregation as observed by Super-X energy-dispersive X-ray spectroscopy(EDS)mapping system.With the grain refinement to nanoscale,the thermal stability is further improved due to the in-crease of Cr content at GBs and the precipitates formed at appropriate high temperatures.The present finding provides guidance for the development of advanced nanostructured ternary alloys.
基金supported by the National Natural Science Foundation of China under Grant No.50871110
文摘The effect of compressive stress on the stability of reversed austenite in gNi steel was investigated by uni- axial and hydrostatic compression. It was found that the uniaxial compressive pressure promoted the Υ-α transformation, while the hydrostatic pressure suppressed the -Υ-α transformation. The pressure dependent transformation behavior can be explained according to thermodynamic analysis.
基金financially supported by the Chinese Ministry of Science and Technology (Nos. 2017YFA0204401 and 2017YFA0700700)the Chinese Academy of Sciences (No.zdyz201701)。
文摘Tensile tests were carried out on gradient nanograined copper samples to investigate the grain orientation dependence of mechanically induced grain boundary migration(GBM) process. The relationship between GBM and the orientations of nanograins relative to loading direction was established by using electron backscatter diffraction. GBM is found to be more pronounced in the grains with higher Schmid factors where dislocations are easier to slip. As a result, the fraction of high angle grain boundaries decreases and that of low angle grain boundaries increases after GBM.
基金the Ministry of Science&Technology of China(Nos.2017YFA0204401 and 2017YFA0700700)the Chinese Academy of Sciences(No.zdyz201701)Science and Technology on Surface Physics and Chemistry Laboratory(No.6142A020303)。
文摘Deformation mechanisms of nanograined and submicron-grained pure cobalt processed by means of high strain rate shear deformation at cryogenic temperatures were studied.Microstructural analysis revealed a transition of governing deformation mechanism from deformation twinning and dislocation slip in submicron-grains to and dislocations slip in nanograins.Microhardness tests illustrated that the Hall-Petch relation slope changes consequently with the transition of deformation mechanism.
