Low-cycle fatigue behavior of Ni-based superalloy GH586 with laser shock processing（LSP） was investigated. The residual stress of the specimens treated with LSP was assessed by X-ray diffraction method. The microstr...Low-cycle fatigue behavior of Ni-based superalloy GH586 with laser shock processing（LSP） was investigated. The residual stress of the specimens treated with LSP was assessed by X-ray diffraction method. The microstructure and fracture morphology were characterized by using an optical microscope（OM）, a scanning electron microscope（SEM）, and a transmission electron microscope（TEM）. The results indicated that the maximum residual compressive stress was at about 1 mm from the shocking spot center, where the residual compressive stress was slightly lower. High density tangling dislocations, dislocation walls, and dislocation cells in the microstructure of the specimens treated with LSP effectively prevented fatigue cracks propagation. The fatigue life was roughly twice as long as that of the specimens without LSP. The fatigue crack initiation（FCI） in specimens treated with LSP was observed in the lateral section and the subsurface simultaneously. The fatigue striation in the fracture treated with LSP was narrower than that in the untreated specimens. Moreover, dimples with tear ridges were found in the fatigued zones of the LSP treated specimens, which would be caused by severe plastic deformation.展开更多
Thermal shock resistant properties of reaction sintered bauxite-based β-Sialon bonded corundum have been investigated, and the results are compared with those of Al_ 2O_ 3 based counterpart. It is found they all ha...Thermal shock resistant properties of reaction sintered bauxite-based β-Sialon bonded corundum have been investigated, and the results are compared with those of Al_ 2O_ 3 based counterpart. It is found they all have very good thermal shock resistance. Their residual strength ratios after one thermal shock cycle at ΔT=1200℃ and ΔT=1350℃ are 61%~73% and 53%~65% respectively. Their critical temperature difference (TSR) is 600℃~800℃. TSR parameters are calculated based on thermal expansion, modulus of elasticity, and fracture toughness determined. The reasons for improving TSR of these composite materials are discussed.展开更多
An austenitic stainless steel 1Cr18Ni9Ti and a solid solution-strengthened Ni-base superalloy GH30 were shock processed using a Q-switched pulsed Nd-glass laser. Microstructure, hardness and residual stress of the las...An austenitic stainless steel 1Cr18Ni9Ti and a solid solution-strengthened Ni-base superalloy GH30 were shock processed using a Q-switched pulsed Nd-glass laser. Microstructure, hardness and residual stress of the laser shock processed surface were investigated as functions of laser processing parameters. Results show that high density of dislocations and fine deformation twins are produced in the laser shock processed surface layers in both the austenitic stainless steel and the nickel-base superalloy. Extensive strain-induced martensite was also observed in the laser shock processed zone of the austenitic steel. The hardness of the laser shock processed surface was significantly enhanced and compressive stress as high as 400 MPa was produced in the laser shock processed surface.展开更多
AIM: To characterize differences of arterial(ABG) and venous(VBG) blood gas analysis in a rabbit model of hemorrhagic shock. METHODS: Following baseline arterial and venous blood gas analysis, fifty anesthetized, vent...AIM: To characterize differences of arterial(ABG) and venous(VBG) blood gas analysis in a rabbit model of hemorrhagic shock. METHODS: Following baseline arterial and venous blood gas analysis, fifty anesthetized, ventilated New Zealand white rabbits were hemorrhaged to and maintained at a mean arterial pressure of 40 mm Hg until a state of shock was obtained, as defined by arterial p H ≤ 7.2 and base deficit ≤-15 mmol/L. Simultaneous ABG and VBG were obtained at 3 minute intervals. Comparisons of p H, base deficit, p CO2, and arteriovenous(a-v) differences were then made between ABG and VBG at baseline and shock states. Statistical analysis was applied where appropriate with a significance of P < 0.05. RESULTS: All 50 animals were hemorrhaged to shockstatus and euthanized; no unexpected loss occurred. Significant differences were noted between baseline and shock states in blood gases for the following parameters: p H was significantly decreased in both arterial(7.39 ± 0.12 to 7.14 ± 0.18) and venous blood gases(7.35 ± 0.15 to 6.98 ± 0.26, P < 0.05), base deficit was significantly increased for arterial(-0.9 ± 3.9 m Eq/L vs-17.8 ± 2.2 m Eq/L) and venous blood gasses(-0.8 ± 3.8 m Eq/L vs-15.3 ± 4.1 m Eq/L, P < 0.05). p CO2 trends(baseline to shock) demonstrated a decrease in arterial blood(40.0 ± 9.1 mm Hg vs 28.9 ± 7.1 mm Hg) but an increase in venous blood(46.0 ± 10.1 mm Hg vs 62.8 ± 15.3 mm Hg), although these trends were non-significant. For calculated arteriovenous differences between baseline and shock states, only the p CO2 difference was shown to be significant during shock.CONCLUSION: In this rabbit model, significant differences exist in blood gas measurements for arterial and venous blood after hemorrhagic shock. A widened p CO2 a-v difference during hemorrhage, reflective of poor tissue oxygenation, may be a better indicator of impending shock.展开更多
基金Funded by the Key Program Project of National Natural Science Foundation of China(NSFC)(No.51641102)Natural Science Foundation of Jiangsu Province(No.16KJB430035)+1 种基金Qing Lan Project of Jiangsu Province in ChinaNational Key Laboratory of Science and Technology on Power Beam Processes of Beijing Aeronautical Manufacturing Technology Research Institute
文摘Low-cycle fatigue behavior of Ni-based superalloy GH586 with laser shock processing（LSP） was investigated. The residual stress of the specimens treated with LSP was assessed by X-ray diffraction method. The microstructure and fracture morphology were characterized by using an optical microscope（OM）, a scanning electron microscope（SEM）, and a transmission electron microscope（TEM）. The results indicated that the maximum residual compressive stress was at about 1 mm from the shocking spot center, where the residual compressive stress was slightly lower. High density tangling dislocations, dislocation walls, and dislocation cells in the microstructure of the specimens treated with LSP effectively prevented fatigue cracks propagation. The fatigue life was roughly twice as long as that of the specimens without LSP. The fatigue crack initiation（FCI） in specimens treated with LSP was observed in the lateral section and the subsurface simultaneously. The fatigue striation in the fracture treated with LSP was narrower than that in the untreated specimens. Moreover, dimples with tear ridges were found in the fatigued zones of the LSP treated specimens, which would be caused by severe plastic deformation.
文摘Thermal shock resistant properties of reaction sintered bauxite-based β-Sialon bonded corundum have been investigated, and the results are compared with those of Al_ 2O_ 3 based counterpart. It is found they all have very good thermal shock resistance. Their residual strength ratios after one thermal shock cycle at ΔT=1200℃ and ΔT=1350℃ are 61%~73% and 53%~65% respectively. Their critical temperature difference (TSR) is 600℃~800℃. TSR parameters are calculated based on thermal expansion, modulus of elasticity, and fracture toughness determined. The reasons for improving TSR of these composite materials are discussed.
文摘An austenitic stainless steel 1Cr18Ni9Ti and a solid solution-strengthened Ni-base superalloy GH30 were shock processed using a Q-switched pulsed Nd-glass laser. Microstructure, hardness and residual stress of the laser shock processed surface were investigated as functions of laser processing parameters. Results show that high density of dislocations and fine deformation twins are produced in the laser shock processed surface layers in both the austenitic stainless steel and the nickel-base superalloy. Extensive strain-induced martensite was also observed in the laser shock processed zone of the austenitic steel. The hardness of the laser shock processed surface was significantly enhanced and compressive stress as high as 400 MPa was produced in the laser shock processed surface.
基金Carolinas Health Care System,Department of Surgery,Charlotte,North Carolina,United States
文摘AIM: To characterize differences of arterial(ABG) and venous(VBG) blood gas analysis in a rabbit model of hemorrhagic shock. METHODS: Following baseline arterial and venous blood gas analysis, fifty anesthetized, ventilated New Zealand white rabbits were hemorrhaged to and maintained at a mean arterial pressure of 40 mm Hg until a state of shock was obtained, as defined by arterial p H ≤ 7.2 and base deficit ≤-15 mmol/L. Simultaneous ABG and VBG were obtained at 3 minute intervals. Comparisons of p H, base deficit, p CO2, and arteriovenous(a-v) differences were then made between ABG and VBG at baseline and shock states. Statistical analysis was applied where appropriate with a significance of P < 0.05. RESULTS: All 50 animals were hemorrhaged to shockstatus and euthanized; no unexpected loss occurred. Significant differences were noted between baseline and shock states in blood gases for the following parameters: p H was significantly decreased in both arterial(7.39 ± 0.12 to 7.14 ± 0.18) and venous blood gases(7.35 ± 0.15 to 6.98 ± 0.26, P < 0.05), base deficit was significantly increased for arterial(-0.9 ± 3.9 m Eq/L vs-17.8 ± 2.2 m Eq/L) and venous blood gasses(-0.8 ± 3.8 m Eq/L vs-15.3 ± 4.1 m Eq/L, P < 0.05). p CO2 trends(baseline to shock) demonstrated a decrease in arterial blood(40.0 ± 9.1 mm Hg vs 28.9 ± 7.1 mm Hg) but an increase in venous blood(46.0 ± 10.1 mm Hg vs 62.8 ± 15.3 mm Hg), although these trends were non-significant. For calculated arteriovenous differences between baseline and shock states, only the p CO2 difference was shown to be significant during shock.CONCLUSION: In this rabbit model, significant differences exist in blood gas measurements for arterial and venous blood after hemorrhagic shock. A widened p CO2 a-v difference during hemorrhage, reflective of poor tissue oxygenation, may be a better indicator of impending shock.
