The strain effect on the critical current is one of the most important properties for polycrystalline YBa2 Cu3O7-δ （REBCO, RE： rare earth） films, in which the reversible effect is intrinsic in the range of strain ...The strain effect on the critical current is one of the most important properties for polycrystalline YBa2 Cu3O7-δ （REBCO, RE： rare earth） films, in which the reversible effect is intrinsic in the range of strain 0 and the irreversible strain εirr. By introducing the applied strain, a modified grain boundaries （GBs） in the REBCO film is developed. lattice model combining the strain and misorientation of A good agreement of the calculation on the lattice model with the experimental data shows that the lattice model is able to well describe the reversible effect of axial strain on the critical current of the REBCO film, and provides a good understanding of the mechanism of the reversible effect of the strain. Moreover, the effects of the crystallographic texture of the REBCO film and the residual strain εr on the variation of the critical current with the applied strain are extensively investigated. Furthermore by using the developed lattice model, the irreversible strain εirr of the REBCO film can be theoretically determined by comparing the calculation of the critical current-strain curve with the experimental data.展开更多
Ultra-high strain rate impact tests were conducted by Split-Hopkinson pressure bar to investigate the microstructure evolution and impact deformation mechanism of a solution treated casting AM80 Mg alloy at 25, 150 an...Ultra-high strain rate impact tests were conducted by Split-Hopkinson pressure bar to investigate the microstructure evolution and impact deformation mechanism of a solution treated casting AM80 Mg alloy at 25, 150 and 250 ℃ with a strain rate of 5000 s^(-1). The microcrack and dynamic recrystallization(DRX) preferentially nucleate at grain boundary(GB) and twin boundary(TB), especially at the intersections between GBs and TBs, and then propagate along twin direction. In contrast, the adiabatic shear bands preferentially occur at high-density twined regions. At 25 ℃, the dominated deformation mechanisms are basal slip and twinning. As deformation temperature increases to 150and 250℃, the deformation gradually shifts to be dominated by a coordinated mechanism among non-basal slip, twinning and DRX. The flow stress behavior and deformation mechanism indicate that the degree of decrease in flow stress with temperature is associated with the change of deformation mode.展开更多
An approach for estimating ground surface rupture caused by strong earthquakes is presented in this paper, where the finite element （FE） method of continuous and discontinuous coalescent displacement fields is adopt...An approach for estimating ground surface rupture caused by strong earthquakes is presented in this paper, where the finite element （FE） method of continuous and discontinuous coalescent displacement fields is adopted. The onset condition of strain localization is introduced to detect the formation of the slippage line. In the analysis, the Drucker-Prager constitutive model is used for soils and the rate- and state-dependent friction law is used on the slippage line to simulate the evolution of the sliding. A simple application to evaluate the ground surface rupture induced by a reverse fault movement is provided, and the numerical simulation shows good agreement with failure characteristics observed in the field after strong earthquakes.展开更多
The stress corrosion crack （SCC） susceptibility of ultra-high strength steel AerMet 100 was investigated by slow strain rate technique （SSRT）, tensile with polarization and surface analysis technique. The curves o...The stress corrosion crack （SCC） susceptibility of ultra-high strength steel AerMet 100 was investigated by slow strain rate technique （SSRT）, tensile with polarization and surface analysis technique. The curves of tf^Cl/tf^W -strain rate are divided into three regions： stress-dominated region, SCC-dominated region, and corrosion-dominated region, so as the curves of εf^Cl/εf^W - strain rate and tm/tf-strain rate. The results of tensile tests with polarization show that the main SCC mechanism of AerMet 100 is anodic dissolution, which controls the corrosion process. The three regions have been discussed according to the relationship between the rate of slip-step formation and the rate of dissolution. Fracture appearances in different environments were analyzed by scanning electron microscopy （SEM）. SCC fracture appears as a mixture of intergranular and dimples, while it is totally dimples in the inert environment. The εf becomes the parameter to predict tf because the relationship between εf^Cl/εf^W and tf^Cl/tf^w is a straight line for AerMet 100.展开更多
The microstructures of electroformed copper liners of shaped charges that had undergone high-strain-rate deformation were observed by optical microscopy （OM） and scanning electron microscopy （SEM）. Meanwhile, the ...The microstructures of electroformed copper liners of shaped charges that had undergone high-strain-rate deformation were observed by optical microscopy （OM） and scanning electron microscopy （SEM）. Meanwhile, the orientation distribution of the grains in the recovered jet was examined by electron backscattering Kikuchi pattern （EBSP） technique. EBSP analysis reveals that the fibrous texture observed in the as-electroformed copper liners disappeared after explosive detonation deformation. OM observation shows that the microstructure evolves system- atically from the jet center to its perimeter during cooling from high temperatures after explosive detonation deformation. This microstructural characteristic is similar to that of solidification, i.e. there exist equiaxed grains in the center of the jet and significant columnar grains around the equiaxed grains. The result reveals that there is melting-related phenomenon in the jet center. Corresponding microhardness variations from the jet center to its perimeter is also determined. All the phenomena can be explained by a strong gradient of temperature across the section of the jet during plastic deformation at high-strain-rate.展开更多
BACKGROUND Proximal humeral fractures represent the third most common observed osteoporotic fracture;the treatment in three and four-part proximal humeral fractures in patients over 65 years is still controversial.Amo...BACKGROUND Proximal humeral fractures represent the third most common observed osteoporotic fracture;the treatment in three and four-part proximal humeral fractures in patients over 65 years is still controversial.Among the treatments described in literature,open reduction and internal fixation(O.R.I.F)and reverse shoulder arthroplasty(RSA)are gaining an increasing popularity.AIM To investigate the correct treatment for three and four-part proximal humeral fractures according to psychological aspects.METHODS It was conducted a prospective study with a series of 63 patients treated with O.R.I.F.(group A)and with RSA(group B)for three and four-part proximal humeral fractures according to Neer classification system.A conservative treatment group,as control,was finally introduced.One independent observer performed clinical and a psychological evaluation at one(T0),six(T1)and twelve months(T2)postoperatively.The Constant’s score and The Disabilities of the Arm,Shoulder and Hand(DASH score)were used for clinical evaluation,while General Anxiety Disorder-7(GAD-7)and Caregiver Strain Scale(CSS)were used for psychological evaluation.RESULTS At one month follow up in group A the mean values were DASH score 50.8,Constant score 36.1,GAD-7 score 5.4,CSS 5.0.For the group B,the average values at T0 were:DASH score 54.6,Constant score 32.0;GAD-7 score 6.4,CSS 6.2.At six months in group A the average values were DASH score 42.1,Constant score 47.3,GAD-7 score 4.3,CSS 3.9.For the group B,the average values at T1 were:DASH score 39.1,Constant score 43.2,GAD-7 score 5.7,CSS 5.5.At twelve months in the group A,the mean values were DASH score 32.8,Constant score 60.0,GAD-7 score 3.2,CSS 3.1.For the group B shown these mean values:DASH score 33.6,Constant score 52.9,GAD-7 score 4.3,CSS 4.5.We demonstrated a better clinical and psychological outcome at T2 in the group treated with osteosynthesis compared to the group treated with arthroplasty(Constant P=0.049,GAD-7 P=0.012 and CSS P=0.005).A better clinical and psychological outcome emerged in control group at T2 comparing with surgical group(DASH score P=0.014,Constant score P<0.001,GAD-7 P=0.002 and CSS P=0.001).CONCLUSION Both open osteosynthesis and reverse shoulder arthroplasty are valid treatments for proximal humeral fractures.According to the best osteosynthesis results the authors suggested to perform a psychological analysis for each patient in order to choose the appropriate treatment.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11372096the Research Fund for the Doctoral Program of Higher Education of China
文摘The strain effect on the critical current is one of the most important properties for polycrystalline YBa2 Cu3O7-δ （REBCO, RE： rare earth） films, in which the reversible effect is intrinsic in the range of strain 0 and the irreversible strain εirr. By introducing the applied strain, a modified grain boundaries （GBs） in the REBCO film is developed. lattice model combining the strain and misorientation of A good agreement of the calculation on the lattice model with the experimental data shows that the lattice model is able to well describe the reversible effect of axial strain on the critical current of the REBCO film, and provides a good understanding of the mechanism of the reversible effect of the strain. Moreover, the effects of the crystallographic texture of the REBCO film and the residual strain εr on the variation of the critical current with the applied strain are extensively investigated. Furthermore by using the developed lattice model, the irreversible strain εirr of the REBCO film can be theoretically determined by comparing the calculation of the critical current-strain curve with the experimental data.
基金supported by the National Natural Science Foundation of China (Nos. 51975201 and 52071139)the Natural Science Foundation of Hunan Province (No.2019JJ50586)。
文摘Ultra-high strain rate impact tests were conducted by Split-Hopkinson pressure bar to investigate the microstructure evolution and impact deformation mechanism of a solution treated casting AM80 Mg alloy at 25, 150 and 250 ℃ with a strain rate of 5000 s^(-1). The microcrack and dynamic recrystallization(DRX) preferentially nucleate at grain boundary(GB) and twin boundary(TB), especially at the intersections between GBs and TBs, and then propagate along twin direction. In contrast, the adiabatic shear bands preferentially occur at high-density twined regions. At 25 ℃, the dominated deformation mechanisms are basal slip and twinning. As deformation temperature increases to 150and 250℃, the deformation gradually shifts to be dominated by a coordinated mechanism among non-basal slip, twinning and DRX. The flow stress behavior and deformation mechanism indicate that the degree of decrease in flow stress with temperature is associated with the change of deformation mode.
基金National Science Foundation Council State KeyLaboratory of Frozen Soil Engineering (SKLFSE200504)State Commonweal Research Project (2002DIB30076)
文摘An approach for estimating ground surface rupture caused by strong earthquakes is presented in this paper, where the finite element （FE） method of continuous and discontinuous coalescent displacement fields is adopted. The onset condition of strain localization is introduced to detect the formation of the slippage line. In the analysis, the Drucker-Prager constitutive model is used for soils and the rate- and state-dependent friction law is used on the slippage line to simulate the evolution of the sliding. A simple application to evaluate the ground surface rupture induced by a reverse fault movement is provided, and the numerical simulation shows good agreement with failure characteristics observed in the field after strong earthquakes.
基金Project(51171011) supported by the National Natural Science Foundation of China
文摘The stress corrosion crack （SCC） susceptibility of ultra-high strength steel AerMet 100 was investigated by slow strain rate technique （SSRT）, tensile with polarization and surface analysis technique. The curves of tf^Cl/tf^W -strain rate are divided into three regions： stress-dominated region, SCC-dominated region, and corrosion-dominated region, so as the curves of εf^Cl/εf^W - strain rate and tm/tf-strain rate. The results of tensile tests with polarization show that the main SCC mechanism of AerMet 100 is anodic dissolution, which controls the corrosion process. The three regions have been discussed according to the relationship between the rate of slip-step formation and the rate of dissolution. Fracture appearances in different environments were analyzed by scanning electron microscopy （SEM）. SCC fracture appears as a mixture of intergranular and dimples, while it is totally dimples in the inert environment. The εf becomes the parameter to predict tf because the relationship between εf^Cl/εf^W and tf^Cl/tf^w is a straight line for AerMet 100.
文摘The microstructures of electroformed copper liners of shaped charges that had undergone high-strain-rate deformation were observed by optical microscopy （OM） and scanning electron microscopy （SEM）. Meanwhile, the orientation distribution of the grains in the recovered jet was examined by electron backscattering Kikuchi pattern （EBSP） technique. EBSP analysis reveals that the fibrous texture observed in the as-electroformed copper liners disappeared after explosive detonation deformation. OM observation shows that the microstructure evolves system- atically from the jet center to its perimeter during cooling from high temperatures after explosive detonation deformation. This microstructural characteristic is similar to that of solidification, i.e. there exist equiaxed grains in the center of the jet and significant columnar grains around the equiaxed grains. The result reveals that there is melting-related phenomenon in the jet center. Corresponding microhardness variations from the jet center to its perimeter is also determined. All the phenomena can be explained by a strong gradient of temperature across the section of the jet during plastic deformation at high-strain-rate.
文摘BACKGROUND Proximal humeral fractures represent the third most common observed osteoporotic fracture;the treatment in three and four-part proximal humeral fractures in patients over 65 years is still controversial.Among the treatments described in literature,open reduction and internal fixation(O.R.I.F)and reverse shoulder arthroplasty(RSA)are gaining an increasing popularity.AIM To investigate the correct treatment for three and four-part proximal humeral fractures according to psychological aspects.METHODS It was conducted a prospective study with a series of 63 patients treated with O.R.I.F.(group A)and with RSA(group B)for three and four-part proximal humeral fractures according to Neer classification system.A conservative treatment group,as control,was finally introduced.One independent observer performed clinical and a psychological evaluation at one(T0),six(T1)and twelve months(T2)postoperatively.The Constant’s score and The Disabilities of the Arm,Shoulder and Hand(DASH score)were used for clinical evaluation,while General Anxiety Disorder-7(GAD-7)and Caregiver Strain Scale(CSS)were used for psychological evaluation.RESULTS At one month follow up in group A the mean values were DASH score 50.8,Constant score 36.1,GAD-7 score 5.4,CSS 5.0.For the group B,the average values at T0 were:DASH score 54.6,Constant score 32.0;GAD-7 score 6.4,CSS 6.2.At six months in group A the average values were DASH score 42.1,Constant score 47.3,GAD-7 score 4.3,CSS 3.9.For the group B,the average values at T1 were:DASH score 39.1,Constant score 43.2,GAD-7 score 5.7,CSS 5.5.At twelve months in the group A,the mean values were DASH score 32.8,Constant score 60.0,GAD-7 score 3.2,CSS 3.1.For the group B shown these mean values:DASH score 33.6,Constant score 52.9,GAD-7 score 4.3,CSS 4.5.We demonstrated a better clinical and psychological outcome at T2 in the group treated with osteosynthesis compared to the group treated with arthroplasty(Constant P=0.049,GAD-7 P=0.012 and CSS P=0.005).A better clinical and psychological outcome emerged in control group at T2 comparing with surgical group(DASH score P=0.014,Constant score P<0.001,GAD-7 P=0.002 and CSS P=0.001).CONCLUSION Both open osteosynthesis and reverse shoulder arthroplasty are valid treatments for proximal humeral fractures.According to the best osteosynthesis results the authors suggested to perform a psychological analysis for each patient in order to choose the appropriate treatment.
