The effects of strain rates on the hot working characteristics and nucleation mechanisms of dynamic recrystallization (DRX) were studied by optical microscopy and electron backscatter diffraction (EBSD) technique. Hot...The effects of strain rates on the hot working characteristics and nucleation mechanisms of dynamic recrystallization (DRX) were studied by optical microscopy and electron backscatter diffraction (EBSD) technique. Hot compression tests were conducted using a Gleeble-1500 simulator at a true strain of 0.7 in the temperature range of 1000 to 1150 °C and strain rate range of 0.01 to 10.00 s?1. It is found that the size and volume fraction of the DRX grains in hot-deformed Inconel 625 superalloy firstly decrease and then increase with increasing strain rate. Meanwhile, the nucleation mechanism of DRX is closely related to the deformation strain rate due to the deformation thermal effect. The discontinuous DRX (DDRX) with bulging of original grain boundaries is the primary nucleation mechanism of DRX, while the continuous DRX (CDRX) with progressive subgrain rotation acts as a secondary nucleation mechanism. The twinning formation can activate the nucleation of DRX. The effects of bulging of original grain boundaries and twinning formation are firstly gradually weakened and then strengthened with the increasing strain rate due to the deformation thermal effect. On the contrary, the effect of subgrain rotation is firstly gradually strengthened and then weakened with the increasing strain rate.展开更多
Static recrystallization of a high strain rate compressed Mg-1 Zn(wt.%)alloy was investigated using electron backscattered diffraction(EBSD).A novel 53°1010 structure was observed in the as-deformed alloy,which s...Static recrystallization of a high strain rate compressed Mg-1 Zn(wt.%)alloy was investigated using electron backscattered diffraction(EBSD).A novel 53°1010 structure was observed in the as-deformed alloy,which showed a{1012}-{1012}double twin relationship with the matrix.When the as-deformed alloy was annealed at 200°C,the{1011}compression twins and{1011}-{1012}double twins showed a higher priority to recrystallize.In addition,the coarse{1012}tension twins and their inner double twins were preferentially to recrystallize,while the lenticular tension twins had little impact on the recrystallization.Therefore,obtaining more compression twins or coarse twins instead of lenticular tension twins can be an effective approach to manipulate recrystallization process in deformed Mg alloys.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
Fine grained Mg-7Gd-5Y-1.2Nd-0.5Zr alloy was investigated by dynamic compression tests using a Split Hopkinson Pressure Bar under the strain rates in the range 1000-2000 s^(-1) and the temperature range 293-573 K alon...Fine grained Mg-7Gd-5Y-1.2Nd-0.5Zr alloy was investigated by dynamic compression tests using a Split Hopkinson Pressure Bar under the strain rates in the range 1000-2000 s^(-1) and the temperature range 293-573 K along the normal direction.The microstructure was measured by optical microscopy,electron back-scattering diffraction,transmission electron microscopy and X-ray diffractometry.The results showed that Mg-7Gd-5Y-1.2Nd-0.5Zr alloy had the positive strain rate strengthening effect and thermal softening effect at high temperature.The solid solution of Gd and Y atoms in Mg-7Gd-5Y-1.2Nd-0.5Zr alloy reduced the asymmetry of α-Mg crystals and changed the critical shear stress of various deformation mechanisms.The main deformation mechanisms were prismatic slip and pyramidal(a)slip,{102}tension twinning,and dynamic recrystallization caused by local deformation such as particle-stimulated nucleation.c 2020 Published by Elsevier B.V.on behalf of Chongqing University.展开更多
Radar interferograms are usually influenced by factors such as atmospheric artifacts,orbital errors,and terrain errors.It is difficult to reduce the influence by using the conventional small baseline subset(SBAS)metho...Radar interferograms are usually influenced by factors such as atmospheric artifacts,orbital errors,and terrain errors.It is difficult to reduce the influence by using the conventional small baseline subset(SBAS)method when determining the deformation rate.This study uses the adjustment model with systematic parameters to improve the conventional SBAS method and employs it to determine the interseismic deformation rate of the Haiyuan fault system,providing a data reference for exploring the locking depth,strain accumulation state,and potential seismic risk assessment of different segments of the Haiyuan fault system.The results are as follows:(1)the simulation experiment verifies the feasibility and robustness of the modified SBAS method.This method can effectively reduce the influence of residual signals such as atmospheric artifacts,orbital errors and terrain errors in the interferograms.The deformation rate map can be significantly improved;(2)the deformation rate field in the radar’s Line of Sight(LOS)direction shows that there are obvious differences between the north and south sides of Haiyuan fault system,which is consistent with the characteristics of the left-lateral strike-slip movement of the Haiyuan fault system.The deformation rate field and profiles reflect the complex trends among different segments of Haiyuan fault system in detail.(3)the deformation rate of the Jingtai pull-apart basin is higher than that of the surrounding areas,possibly indicating strong regional activity,which provides a reference for studying the seismic risk of the Jingtai pull-apart basin;and(4)the interseismic deformation rate and profiles across the fault show that the middle section of the Lao Hu Shan(LHS)segment and the western and middle sections of the Haiyuan segment are locked.展开更多
Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fr...Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fracturing methods.The tangent modulus method(TMM)is one such technique that can be applied to oriented cored rocks to measure in-situ stresses.Like the deformation rate analysis(DRA),the rock specimen is subjected to two cycles of uniaxial compression and the stress-tangent modulus curve for the two cycles is obtained from the stress-strain curve.A bending point in the tangent modulus curve of the first cycle is observed,separating it from the tangent modulus curve of the second cycle.The point of separation between the two curves is assumed to be the previously applied maximum stress.A number of experiments were conducted on coal and coal measured rocks(sandstone and limestone)to understand the effect of loading conditions and the time delay.The specimens were preloaded,and cyclic compressions were applied under three different modes of loading,four different strain rates,and time delays of up to one week.The bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes,and no effect of loading rate was observed on the bending points in TMM.However,a clear effect of time delay was observed on the TMM,contradicting the DRA results.This could be due to the sensitivity of TMM and the range of its applicability,all of which need further investigation for the in-situ stress measurement.展开更多
It is pointed out that crystals are discrete but not continuous materials. Hence the rotation R in decomposition F = RU and spin TY in (F) over dot F-1 ore not correct. Errors will arise in plastic deformation rare if...It is pointed out that crystals are discrete but not continuous materials. Hence the rotation R in decomposition F = RU and spin TY in (F) over dot F-1 ore not correct. Errors will arise in plastic deformation rare if it is directly expressed with amounts of velocity of slips in glide systems such as (gamma) over dot upsilon circle times n. The geometrical figure of crystal lattices does nor change after slips and based on this idea a simple way in mechanics of continuous media to get the plastic deformations rare induced by slips is proposed. Constitutive equations are recommended.展开更多
The shear responses of β-SiC are investigated using molecular dynamics simulation with the Tersoff interatomic potential. Results show a clear decreasing trend in critical stress,fracture strain and shear modulus as ...The shear responses of β-SiC are investigated using molecular dynamics simulation with the Tersoff interatomic potential. Results show a clear decreasing trend in critical stress,fracture strain and shear modulus as temperature increases. Above a critical temperature, β-SiC bulk just fractures after the elastic deformation. However, below the critical temperature, an interesting pattern in β-SiC bulk emerges due to the elongation of Si-C bonds before fracture. Additionally, the shear deformation of β-SiC at room temperature is found to be dependent on the strain rate. This study may shed light on the deformation mechanism dependent on temperature and strain rate.展开更多
The computer simulation of Al three-dimensional crystallite containing grain boundary of special type was carried out and its behaviour under high rate loading was investigated. The molecular dynamics method was used ...The computer simulation of Al three-dimensional crystallite containing grain boundary of special type was carried out and its behaviour under high rate loading was investigated. The molecular dynamics method was used and interaction betwen atoms was described based on pseudopotential method. Vortical character of the atom movements in the grain boundary region is realized under shear loading in certain directions. Back and forth movements of atoms in the direction which is perpendicular to the shear also arise. Amplitude of such movements is approximately equal to an interplanar distance in this direction.展开更多
[ Objective] The study aimed to explore the effects of magnetic treatment on the quality of chicken semen stored at low temperature. [ Method] 5 ml fresh chicken semen was divided into five groups equally, each of whi...[ Objective] The study aimed to explore the effects of magnetic treatment on the quality of chicken semen stored at low temperature. [ Method] 5 ml fresh chicken semen was divided into five groups equally, each of which was diluted at the volume ratio 1：4. With the group without magnetic treatment as the control, the other four groups were magnetized for 6, 12, 24 and 48 min in the self-made magnetizer, respectively. Subsequently, all the five groups were stored at 2 -4 ℃, and the sperm motility, survival time, survival index and deformity rate were observed regularly. [ Result] Comparing with the control group, the magnetic groups showed higher sperm motilities and effective survival indices as well as lower deformity rates. The effective survival index of the group magnetized for 24 min was the highest and increased by 7.75% in con- trast to the control. [ Conclusion] Magnetic treatment can effectively enhance the quality of chicken semen stored at low temperature.展开更多
[ Objective] To study the effects of clindamycin on germ cells of male mice. [Method] A total of 48 healthy adult male mice were randomly divided into group A, group B, group C and control group, 12 mice in each group...[ Objective] To study the effects of clindamycin on germ cells of male mice. [Method] A total of 48 healthy adult male mice were randomly divided into group A, group B, group C and control group, 12 mice in each group. The mice in the group A, group B and group C were respectively administrated with clindamycin at doses of 15, 30 and 60 mg/kg.d via intraperitoneai injection, and those in the control group were trea- ted with normal saline. On Day 29 after administration, the mice were killed by dislocation, and the sperm motility rate, sperm deformity rate and the percentage of sperm having swollen tail membrane were determined, respectively. [ Result] The sperm motility rate and the percentage of sperm having swollen tail membrane of the group B and group C were lower than those of the control group; and the sperm deformity rate of the group B and group C was higher than that of the control group. The sperm motility rate, sperm deformity rate and percentage of sperm having swollen tail membrane had no significant difference between the group A and control group. [ Conclusion] The clindamycin at a dose equal to or more than that used for severe infection affects the normal function of sperm in mice.展开更多
[Objective]To improve the artificial propagation technique of Misgurnus anguillicaudatus,and to provide technical support for the industrialization development of M.anguillicaudatus in future.[Methods] The hatching ra...[Objective]To improve the artificial propagation technique of Misgurnus anguillicaudatus,and to provide technical support for the industrialization development of M.anguillicaudatus in future.[Methods] The hatching rates,survival rates,deformity rates and parent morality rates of M.anguillicaudatus were compared by ecological hatching method and traditional hatching method.[Results]The hatching rate by ecological hatching method was 32.60% higher than that by traditional hatching method,showing extremely significant differences.The survival rate of M.anguillicaudatus fingerlings by ecological hatching method was2.32% higher than that by traditional hatching method.And the deformity rates of M.anguillicaudatus fingerlings by traditional hatching method and ecological hatching method were 26.50% and 24.14%,respectively,indicating no significant differences.The morality rates of female parents of M.anguillicaudatus were89.72% and 5.91% by traditional hatching method and ecological hatching method,respectively.[Conclusions]Ecological hatching method effectively improved the hatching rate and fingerling survival rate of M.anguillicaudatus,and reduced the morality rate of female parents,which was helpful to save the production cost,met the requirements for large-scale production of M.anguillicaudatus,and had good application prospect.展开更多
The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types o...The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types of rocks, the coarse-grained sandstone and Aue granite. Each type of rocks had two shapes, the Brazilian disk and a square shape. The mechanical behaviors of the numerical model had already been verified to be in agreement with those of the physical specimens in previous research. Three loading protocols with different loading cycles in two orthogonal directions were specially designed in the numerical tests. The results show that no memory effect is observed in the second loading in the orthogonal direction. However, both the cumulative crack number of the second loading and the differential strain value at the inflection point are influenced by the first loading in the orthogonal direction.展开更多
SBAS-InSAR technology is characterized by the advantages of reducing the influence of terrain-simulation error,time-space decorrelation,atmospheric error,thereby improving the reliability of surface-deformation monito...SBAS-InSAR technology is characterized by the advantages of reducing the influence of terrain-simulation error,time-space decorrelation,atmospheric error,thereby improving the reliability of surface-deformation monitoring.This paper studies the early landslide identification method based on SBAS-InSAR technology.Selecting the Jiangdingya landslide area in Zhouqu County,Gansu Province as the research area,84 ascendingorbit Sentinel-1A SAR images from 2015 to 2019 are collected.In addition,using SBAS-InSAR technology,the rate and time-series results of surface deformation of the landslide area in Jiangdingya during this period are extracted,and potential landslides are identified.The results show that the early landslide identification method based on SBAS-InSAR technology is highly feasible and is a better tool for identifying potential landslides in large areas.展开更多
An investigation has been made into the microstructural characterization of the shear bands generated under high-strain rate （≈10^4 s^-1） deformation in Fe-15%Cr-15%Ni single crystal by EBSD-SEM （electron backscat...An investigation has been made into the microstructural characterization of the shear bands generated under high-strain rate （≈10^4 s^-1） deformation in Fe-15%Cr-15%Ni single crystal by EBSD-SEM （electron backscatter diffraction-scanning electron microscopy）, TEM （transmission electron in microscopy） and HREM （high- resolution electron microscopy）. The results reveal that the propagation of the shear band exhibits an asymmetrical behavior arising from inhomogenous distribution in plasticity in the bands because of different resistance to the collapse in different crystallographic directions; The γ-ε-α′phase transformations may take place inside and outside the bands, and these martensitic phases currently nucleate at intersections either between the twins and deformation bands or between the twins and ε-sheet. Investigation by EBSD shows that recrystallization can occur in the bands with a grain size of an average of 0.2μm in diameter. These nano-grains are proposed to attribute to the results of either dynamic or static recrystallization, which can be described by the rotational recrystallization mechanism. Calculation and analysis indicate that the strain rate inside the shear band can reach 2.50×10^6 s^-1, which is higher, by two or three orders of magnitude, than that exerted dynamically on the specimen tested.展开更多
Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentat...Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentation techniques and the Sakai＇s series elastic and plastic deformation model to extract the resistance to plastic deformation from the plane strain modulus and the contact hardness for presintered zirconia. The modulus and the resistance to plasticity were used to calculate the relative amount of elasticity and plasticity. The fracture energy and the normalized indentation absorbed energy were used to deconvolute the resistance to machining-induced cracking based on the Sakai-Nowak model. All properties were extracted at a 10 mN peak load and loading rates of 0.1-2 mN/s to determine the loading rate effects on these properties. We found that the resistance to plasticity and the resistance to machining-induced cracking were independent of the loading rate （ANOVA, p 〉 0.05）. The elastic and plastic displacements depended on the loading rate through power laws. This loading rate-dependent deformation behaviour was explained by the maximum shear stress generated underneath the indenter and the indentation energy. The plastic deformation components and the indentation absorbed energy at all loading rates were higher than the elastic deformation components and the elastic strain energy, respectively. Finally, we established the linkage among the pore structure, indentation behaviour and machinability of pre-sintered zirconia.展开更多
We have collected GPS data in the period of 1999-2007 from the Crustal Motion Observation Network of China along the Zhangjiakou-Bohai fault and its adjacent regions to study the characteristics of present-day crustal...We have collected GPS data in the period of 1999-2007 from the Crustal Motion Observation Network of China along the Zhangjiakou-Bohai fault and its adjacent regions to study the characteristics of present-day crustal horizontal motion velocities in the research zone.Strain rate components are computed in the spheric coordinate system by the least square collocation method.According to the spatial distribution of the principal strain rate,dilation rate and maximum shear strain rate derived from GPS measurements,this paper analyses the deformation of the subordinary faults of the Zhangjiakou-Bohai fault.The principal compression strain rates are apparently greater than the principal extension strain rates.The larger shear strain rate is mainly in and around the Xianghe,Wenan and Tangshan areas in Hebei Province.According to the profiles across different segments of the Zhangjiakou-Bohai fault,the three segments glong the Zhangjiakou-Bohai fault show an obviously left-lateal strike-slip and compression characteristics.By analysis of the motion characteristics of the blocks,e.g.the Yanshan block,North China Plain block,Ordos block,and Ludong-Huanghai block in and around the North China region,this paper speculates that the dynamics of the motion styles of Zhangjiakou-Bohai fault may directly come from the relative movement between the Yanshan block and the North China plain block,and the ultimate dynamics may be the results of the collison between Indian plate and Eurasian plate,and the persistent northeastward extrusion of the Indian plate.展开更多
Atmospheric phase delay,primarily caused by water vapor in the troposphere,is a major source of error in InSAR measurements,especially for land subsidence monitoring.This study integrates GNSS and GACOS data to correc...Atmospheric phase delay,primarily caused by water vapor in the troposphere,is a major source of error in InSAR measurements,especially for land subsidence monitoring.This study integrates GNSS and GACOS data to correct tropospheric delay and enhance InSAR accuracy in Banting,Selangor.A total of 27 Sentinel-1A images,14GNSS stations,and 27 corresponding GACOS ZTD mapswere used tomonitor subsidence between 2023 and 2025.The InSAR data were processed using SNAP,StaMPS,and the TRAIN toolbox,incorporating both GNSS-and GACOS-derived ZTD corrections.The results show that applying atmospheric correction improved the estimated deformation range from−14.9 mm/year(min)and 9.1 mm/year(max)to−14.7 and 9.2 mm/year usingGACOS ZTD.Further enhancement was achieved by integrating GNSS and GACOS ZTD,resulting in deformation estimates ranging from−15.4 to 9.3 mm/year.Validation against reference GNSS data from the MERU MyRTKnet station revealed that the integrated correction yielded the lowest RMSE of 0.025,compared to 0.029 with GACOS-only correction and 0.03 without any correction.Overall,the integration of GNSS-and GACOS-derived atmospheric corrections significantly improved the accuracy of InSAR-based subsidence measurements,offering a promising approach for precise ground deformation monitoring in humid,tropical environments.展开更多
The paper of Shen et al., entitled "Surveying of the deformed terraces and crust shortening rate in the northwest Tarim Basin", was published in Chinese Science Bulletin (Vol. 46, No. 12). Shen et al. found ...The paper of Shen et al., entitled "Surveying of the deformed terraces and crust shortening rate in the northwest Tarim Basin", was published in Chinese Science Bulletin (Vol. 46, No. 12). Shen et al. found the deformation of Late Pleistocene to Holocene terraces of the Boguzi River across the Artushi Anticline in the northwest Tarim Basin close to the Pamir, and made level survey and differential GPS measurement, which is of great importance to geodynamics for research on the coupling of Tianshan Mountains uplifting and Tarim Basin depression. But their understanding to the deformation mechanics of terraces and the calculation methods of crustal shortening are open to discussion. Therefore, we discuss it with Shen Jun et al.展开更多
To reduce data variance caused by individual differences of different samples,a new experimental method is proposed by loading and unloading the axial forces with different frequencies and different waves of a certain...To reduce data variance caused by individual differences of different samples,a new experimental method is proposed by loading and unloading the axial forces with different frequencies and different waves of a certain load amplitude to the same rock sample without damaging it.Lag time segments are defined and fractionized into segments I andⅡ.Criterions for seg-mentation,definitions of relevant parameters and empirical analysis are also offered afterwards.In the course of sinusoidal loading,the serious peak value dislocation of the displacement variation rate and the loading rate is defined as peak dislocation.Meanwhile,the definition of the apparent tangent modulus is put forward and the linear relation between it and the vertical force in the frequency of 0.1,0.2,0.5 Hz sinusoidal loading segment is confirmed to be ever-present on the basis of the test data.Then the calculating formula of the deformation rate in non-lag time is deduced.It is thus suggested that the deformation rate should be codetermined by the loading rate df/dt and instant load f(t),which well explains the peak dislocation of the time-variable curve peak value of dl/dt and deformation rate of df/dt.Finally the lag time derivation model is established and by comparing the calculated values with the measured ones,it is demonstrated that the above formula offers a better simulation of the sandstone deformation rate in the sinusoidal loading segment,with the load amplitude being 96 kN and the frequency ranging from 0.1 Hz to 0.5 Hz.展开更多
基金co-funded by the National Natural Science Foundation of China and Baoshan Iron & Steel Co., Ltd. (No. 50834008)
文摘The effects of strain rates on the hot working characteristics and nucleation mechanisms of dynamic recrystallization (DRX) were studied by optical microscopy and electron backscatter diffraction (EBSD) technique. Hot compression tests were conducted using a Gleeble-1500 simulator at a true strain of 0.7 in the temperature range of 1000 to 1150 °C and strain rate range of 0.01 to 10.00 s?1. It is found that the size and volume fraction of the DRX grains in hot-deformed Inconel 625 superalloy firstly decrease and then increase with increasing strain rate. Meanwhile, the nucleation mechanism of DRX is closely related to the deformation strain rate due to the deformation thermal effect. The discontinuous DRX (DDRX) with bulging of original grain boundaries is the primary nucleation mechanism of DRX, while the continuous DRX (CDRX) with progressive subgrain rotation acts as a secondary nucleation mechanism. The twinning formation can activate the nucleation of DRX. The effects of bulging of original grain boundaries and twinning formation are firstly gradually weakened and then strengthened with the increasing strain rate due to the deformation thermal effect. On the contrary, the effect of subgrain rotation is firstly gradually strengthened and then weakened with the increasing strain rate.
基金financially supported by National Natural Science Foundation of China(No.51701121,No.51825101)Shanghai Sailing Program(17YF1408800)+2 种基金Science and Technology Commission of Shanghai Municipality(No.18511109302)Qinghai Provincial Science and Technology Key Program(No.2018-GX-A1)Startup Fund for Youngman Research at SJTU(No.18X100040022)
文摘Static recrystallization of a high strain rate compressed Mg-1 Zn(wt.%)alloy was investigated using electron backscattered diffraction(EBSD).A novel 53°1010 structure was observed in the as-deformed alloy,which showed a{1012}-{1012}double twin relationship with the matrix.When the as-deformed alloy was annealed at 200°C,the{1011}compression twins and{1011}-{1012}double twins showed a higher priority to recrystallize.In addition,the coarse{1012}tension twins and their inner double twins were preferentially to recrystallize,while the lenticular tension twins had little impact on the recrystallization.Therefore,obtaining more compression twins or coarse twins instead of lenticular tension twins can be an effective approach to manipulate recrystallization process in deformed Mg alloys.
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.
基金National Natural Science Foundation of China(Nos.51571145,51404137)City of Ningbo"science and technology innovation 2025"major special project(new energy vehicle lightweight magnesium alloy material precision forming technology)(No.2018B10045).
文摘Fine grained Mg-7Gd-5Y-1.2Nd-0.5Zr alloy was investigated by dynamic compression tests using a Split Hopkinson Pressure Bar under the strain rates in the range 1000-2000 s^(-1) and the temperature range 293-573 K along the normal direction.The microstructure was measured by optical microscopy,electron back-scattering diffraction,transmission electron microscopy and X-ray diffractometry.The results showed that Mg-7Gd-5Y-1.2Nd-0.5Zr alloy had the positive strain rate strengthening effect and thermal softening effect at high temperature.The solid solution of Gd and Y atoms in Mg-7Gd-5Y-1.2Nd-0.5Zr alloy reduced the asymmetry of α-Mg crystals and changed the critical shear stress of various deformation mechanisms.The main deformation mechanisms were prismatic slip and pyramidal(a)slip,{102}tension twinning,and dynamic recrystallization caused by local deformation such as particle-stimulated nucleation.c 2020 Published by Elsevier B.V.on behalf of Chongqing University.
基金supported by the National Natural Science Foundation of China(41874011,41861134009)the National Key Research and Development Program of China(2018YFC1503603)
文摘Radar interferograms are usually influenced by factors such as atmospheric artifacts,orbital errors,and terrain errors.It is difficult to reduce the influence by using the conventional small baseline subset(SBAS)method when determining the deformation rate.This study uses the adjustment model with systematic parameters to improve the conventional SBAS method and employs it to determine the interseismic deformation rate of the Haiyuan fault system,providing a data reference for exploring the locking depth,strain accumulation state,and potential seismic risk assessment of different segments of the Haiyuan fault system.The results are as follows:(1)the simulation experiment verifies the feasibility and robustness of the modified SBAS method.This method can effectively reduce the influence of residual signals such as atmospheric artifacts,orbital errors and terrain errors in the interferograms.The deformation rate map can be significantly improved;(2)the deformation rate field in the radar’s Line of Sight(LOS)direction shows that there are obvious differences between the north and south sides of Haiyuan fault system,which is consistent with the characteristics of the left-lateral strike-slip movement of the Haiyuan fault system.The deformation rate field and profiles reflect the complex trends among different segments of Haiyuan fault system in detail.(3)the deformation rate of the Jingtai pull-apart basin is higher than that of the surrounding areas,possibly indicating strong regional activity,which provides a reference for studying the seismic risk of the Jingtai pull-apart basin;and(4)the interseismic deformation rate and profiles across the fault show that the middle section of the Lao Hu Shan(LHS)segment and the western and middle sections of the Haiyuan segment are locked.
基金financially supported by the Australian Coal Association Research Program(ACARP)under project C29010.
文摘Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fracturing methods.The tangent modulus method(TMM)is one such technique that can be applied to oriented cored rocks to measure in-situ stresses.Like the deformation rate analysis(DRA),the rock specimen is subjected to two cycles of uniaxial compression and the stress-tangent modulus curve for the two cycles is obtained from the stress-strain curve.A bending point in the tangent modulus curve of the first cycle is observed,separating it from the tangent modulus curve of the second cycle.The point of separation between the two curves is assumed to be the previously applied maximum stress.A number of experiments were conducted on coal and coal measured rocks(sandstone and limestone)to understand the effect of loading conditions and the time delay.The specimens were preloaded,and cyclic compressions were applied under three different modes of loading,four different strain rates,and time delays of up to one week.The bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes,and no effect of loading rate was observed on the bending points in TMM.However,a clear effect of time delay was observed on the TMM,contradicting the DRA results.This could be due to the sensitivity of TMM and the range of its applicability,all of which need further investigation for the in-situ stress measurement.
文摘It is pointed out that crystals are discrete but not continuous materials. Hence the rotation R in decomposition F = RU and spin TY in (F) over dot F-1 ore not correct. Errors will arise in plastic deformation rare if it is directly expressed with amounts of velocity of slips in glide systems such as (gamma) over dot upsilon circle times n. The geometrical figure of crystal lattices does nor change after slips and based on this idea a simple way in mechanics of continuous media to get the plastic deformations rare induced by slips is proposed. Constitutive equations are recommended.
基金supported by the National Natural Science Foundation of China(NSFC Grants No.11632014,11302161 and11302162)China Postdoctoral Science Foundation(Grant No.2013M542339)the Chang Jiang Scholar program
文摘The shear responses of β-SiC are investigated using molecular dynamics simulation with the Tersoff interatomic potential. Results show a clear decreasing trend in critical stress,fracture strain and shear modulus as temperature increases. Above a critical temperature, β-SiC bulk just fractures after the elastic deformation. However, below the critical temperature, an interesting pattern in β-SiC bulk emerges due to the elongation of Si-C bonds before fracture. Additionally, the shear deformation of β-SiC at room temperature is found to be dependent on the strain rate. This study may shed light on the deformation mechanism dependent on temperature and strain rate.
文摘The computer simulation of Al three-dimensional crystallite containing grain boundary of special type was carried out and its behaviour under high rate loading was investigated. The molecular dynamics method was used and interaction betwen atoms was described based on pseudopotential method. Vortical character of the atom movements in the grain boundary region is realized under shear loading in certain directions. Back and forth movements of atoms in the direction which is perpendicular to the shear also arise. Amplitude of such movements is approximately equal to an interplanar distance in this direction.
文摘[ Objective] The study aimed to explore the effects of magnetic treatment on the quality of chicken semen stored at low temperature. [ Method] 5 ml fresh chicken semen was divided into five groups equally, each of which was diluted at the volume ratio 1：4. With the group without magnetic treatment as the control, the other four groups were magnetized for 6, 12, 24 and 48 min in the self-made magnetizer, respectively. Subsequently, all the five groups were stored at 2 -4 ℃, and the sperm motility, survival time, survival index and deformity rate were observed regularly. [ Result] Comparing with the control group, the magnetic groups showed higher sperm motilities and effective survival indices as well as lower deformity rates. The effective survival index of the group magnetized for 24 min was the highest and increased by 7.75% in con- trast to the control. [ Conclusion] Magnetic treatment can effectively enhance the quality of chicken semen stored at low temperature.
基金supported by the grants from the University Scientific Research Project of Inner Mongolia Autonomous Region (NJzc08159)
文摘[ Objective] To study the effects of clindamycin on germ cells of male mice. [Method] A total of 48 healthy adult male mice were randomly divided into group A, group B, group C and control group, 12 mice in each group. The mice in the group A, group B and group C were respectively administrated with clindamycin at doses of 15, 30 and 60 mg/kg.d via intraperitoneai injection, and those in the control group were trea- ted with normal saline. On Day 29 after administration, the mice were killed by dislocation, and the sperm motility rate, sperm deformity rate and the percentage of sperm having swollen tail membrane were determined, respectively. [ Result] The sperm motility rate and the percentage of sperm having swollen tail membrane of the group B and group C were lower than those of the control group; and the sperm deformity rate of the group B and group C was higher than that of the control group. The sperm motility rate, sperm deformity rate and percentage of sperm having swollen tail membrane had no significant difference between the group A and control group. [ Conclusion] The clindamycin at a dose equal to or more than that used for severe infection affects the normal function of sperm in mice.
基金Supported by the Basic Scientific Research Project of Henan Province
文摘[Objective]To improve the artificial propagation technique of Misgurnus anguillicaudatus,and to provide technical support for the industrialization development of M.anguillicaudatus in future.[Methods] The hatching rates,survival rates,deformity rates and parent morality rates of M.anguillicaudatus were compared by ecological hatching method and traditional hatching method.[Results]The hatching rate by ecological hatching method was 32.60% higher than that by traditional hatching method,showing extremely significant differences.The survival rate of M.anguillicaudatus fingerlings by ecological hatching method was2.32% higher than that by traditional hatching method.And the deformity rates of M.anguillicaudatus fingerlings by traditional hatching method and ecological hatching method were 26.50% and 24.14%,respectively,indicating no significant differences.The morality rates of female parents of M.anguillicaudatus were89.72% and 5.91% by traditional hatching method and ecological hatching method,respectively.[Conclusions]Ecological hatching method effectively improved the hatching rate and fingerling survival rate of M.anguillicaudatus,and reduced the morality rate of female parents,which was helpful to save the production cost,met the requirements for large-scale production of M.anguillicaudatus,and had good application prospect.
基金supported by the National Natural Science Foundation of China (Grant No. 50978083)the Fundamental Research Funds for the Central Universities (Grants No. 2009B07714 and 2010B13914) in Chinathe Innovation Project for Graduate Students of Jiangsu Province (Grant No. CX10B_215Z)
文摘The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types of rocks, the coarse-grained sandstone and Aue granite. Each type of rocks had two shapes, the Brazilian disk and a square shape. The mechanical behaviors of the numerical model had already been verified to be in agreement with those of the physical specimens in previous research. Three loading protocols with different loading cycles in two orthogonal directions were specially designed in the numerical tests. The results show that no memory effect is observed in the second loading in the orthogonal direction. However, both the cumulative crack number of the second loading and the differential strain value at the inflection point are influenced by the first loading in the orthogonal direction.
基金Received on May 7th,2020revised on September 27th,2020.This project is sponsored by the Research on Early Identification of Landslide Hazards based on High-resolution SAR Image(KJ-2018-13).
文摘SBAS-InSAR technology is characterized by the advantages of reducing the influence of terrain-simulation error,time-space decorrelation,atmospheric error,thereby improving the reliability of surface-deformation monitoring.This paper studies the early landslide identification method based on SBAS-InSAR technology.Selecting the Jiangdingya landslide area in Zhouqu County,Gansu Province as the research area,84 ascendingorbit Sentinel-1A SAR images from 2015 to 2019 are collected.In addition,using SBAS-InSAR technology,the rate and time-series results of surface deformation of the landslide area in Jiangdingya during this period are extracted,and potential landslides are identified.The results show that the early landslide identification method based on SBAS-InSAR technology is highly feasible and is a better tool for identifying potential landslides in large areas.
文摘An investigation has been made into the microstructural characterization of the shear bands generated under high-strain rate （≈10^4 s^-1） deformation in Fe-15%Cr-15%Ni single crystal by EBSD-SEM （electron backscatter diffraction-scanning electron microscopy）, TEM （transmission electron in microscopy） and HREM （high- resolution electron microscopy）. The results reveal that the propagation of the shear band exhibits an asymmetrical behavior arising from inhomogenous distribution in plasticity in the bands because of different resistance to the collapse in different crystallographic directions; The γ-ε-α′phase transformations may take place inside and outside the bands, and these martensitic phases currently nucleate at intersections either between the twins and deformation bands or between the twins and ε-sheet. Investigation by EBSD shows that recrystallization can occur in the bands with a grain size of an average of 0.2μm in diameter. These nano-grains are proposed to attribute to the results of either dynamic or static recrystallization, which can be described by the rotational recrystallization mechanism. Calculation and analysis indicate that the strain rate inside the shear band can reach 2.50×10^6 s^-1, which is higher, by two or three orders of magnitude, than that exerted dynamically on the specimen tested.
基金supported by the JCU Collaboration Grants Scheme awarded to L.Yin
文摘Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentation techniques and the Sakai＇s series elastic and plastic deformation model to extract the resistance to plastic deformation from the plane strain modulus and the contact hardness for presintered zirconia. The modulus and the resistance to plasticity were used to calculate the relative amount of elasticity and plasticity. The fracture energy and the normalized indentation absorbed energy were used to deconvolute the resistance to machining-induced cracking based on the Sakai-Nowak model. All properties were extracted at a 10 mN peak load and loading rates of 0.1-2 mN/s to determine the loading rate effects on these properties. We found that the resistance to plasticity and the resistance to machining-induced cracking were independent of the loading rate （ANOVA, p 〉 0.05）. The elastic and plastic displacements depended on the loading rate through power laws. This loading rate-dependent deformation behaviour was explained by the maximum shear stress generated underneath the indenter and the indentation energy. The plastic deformation components and the indentation absorbed energy at all loading rates were higher than the elastic deformation components and the elastic strain energy, respectively. Finally, we established the linkage among the pore structure, indentation behaviour and machinability of pre-sintered zirconia.
基金funded by the Technology and Innovation Foundation of the First Monitoring Center of China Earthquake Administration (FMC2014018)Science for Earthquake Resilience Project of China Earthquake Administration (XH15062)+1 种基金 National Natural Science Foundation Item of China (4137221541272233)
文摘We have collected GPS data in the period of 1999-2007 from the Crustal Motion Observation Network of China along the Zhangjiakou-Bohai fault and its adjacent regions to study the characteristics of present-day crustal horizontal motion velocities in the research zone.Strain rate components are computed in the spheric coordinate system by the least square collocation method.According to the spatial distribution of the principal strain rate,dilation rate and maximum shear strain rate derived from GPS measurements,this paper analyses the deformation of the subordinary faults of the Zhangjiakou-Bohai fault.The principal compression strain rates are apparently greater than the principal extension strain rates.The larger shear strain rate is mainly in and around the Xianghe,Wenan and Tangshan areas in Hebei Province.According to the profiles across different segments of the Zhangjiakou-Bohai fault,the three segments glong the Zhangjiakou-Bohai fault show an obviously left-lateal strike-slip and compression characteristics.By analysis of the motion characteristics of the blocks,e.g.the Yanshan block,North China Plain block,Ordos block,and Ludong-Huanghai block in and around the North China region,this paper speculates that the dynamics of the motion styles of Zhangjiakou-Bohai fault may directly come from the relative movement between the Yanshan block and the North China plain block,and the ultimate dynamics may be the results of the collison between Indian plate and Eurasian plate,and the persistent northeastward extrusion of the Indian plate.
文摘Atmospheric phase delay,primarily caused by water vapor in the troposphere,is a major source of error in InSAR measurements,especially for land subsidence monitoring.This study integrates GNSS and GACOS data to correct tropospheric delay and enhance InSAR accuracy in Banting,Selangor.A total of 27 Sentinel-1A images,14GNSS stations,and 27 corresponding GACOS ZTD mapswere used tomonitor subsidence between 2023 and 2025.The InSAR data were processed using SNAP,StaMPS,and the TRAIN toolbox,incorporating both GNSS-and GACOS-derived ZTD corrections.The results show that applying atmospheric correction improved the estimated deformation range from−14.9 mm/year(min)and 9.1 mm/year(max)to−14.7 and 9.2 mm/year usingGACOS ZTD.Further enhancement was achieved by integrating GNSS and GACOS ZTD,resulting in deformation estimates ranging from−15.4 to 9.3 mm/year.Validation against reference GNSS data from the MERU MyRTKnet station revealed that the integrated correction yielded the lowest RMSE of 0.025,compared to 0.029 with GACOS-only correction and 0.03 without any correction.Overall,the integration of GNSS-and GACOS-derived atmospheric corrections significantly improved the accuracy of InSAR-based subsidence measurements,offering a promising approach for precise ground deformation monitoring in humid,tropical environments.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 49832040).
文摘The paper of Shen et al., entitled "Surveying of the deformed terraces and crust shortening rate in the northwest Tarim Basin", was published in Chinese Science Bulletin (Vol. 46, No. 12). Shen et al. found the deformation of Late Pleistocene to Holocene terraces of the Boguzi River across the Artushi Anticline in the northwest Tarim Basin close to the Pamir, and made level survey and differential GPS measurement, which is of great importance to geodynamics for research on the coupling of Tianshan Mountains uplifting and Tarim Basin depression. But their understanding to the deformation mechanics of terraces and the calculation methods of crustal shortening are open to discussion. Therefore, we discuss it with Shen Jun et al.
基金supported by the National Natural Science Foundation of China(Grant No.90610029)the Foundation of China Three Gorges University(Grant Nos.KJ2009B061,KJ2009A033,2008ZRJ05,00956)
文摘To reduce data variance caused by individual differences of different samples,a new experimental method is proposed by loading and unloading the axial forces with different frequencies and different waves of a certain load amplitude to the same rock sample without damaging it.Lag time segments are defined and fractionized into segments I andⅡ.Criterions for seg-mentation,definitions of relevant parameters and empirical analysis are also offered afterwards.In the course of sinusoidal loading,the serious peak value dislocation of the displacement variation rate and the loading rate is defined as peak dislocation.Meanwhile,the definition of the apparent tangent modulus is put forward and the linear relation between it and the vertical force in the frequency of 0.1,0.2,0.5 Hz sinusoidal loading segment is confirmed to be ever-present on the basis of the test data.Then the calculating formula of the deformation rate in non-lag time is deduced.It is thus suggested that the deformation rate should be codetermined by the loading rate df/dt and instant load f(t),which well explains the peak dislocation of the time-variable curve peak value of dl/dt and deformation rate of df/dt.Finally the lag time derivation model is established and by comparing the calculated values with the measured ones,it is demonstrated that the above formula offers a better simulation of the sandstone deformation rate in the sinusoidal loading segment,with the load amplitude being 96 kN and the frequency ranging from 0.1 Hz to 0.5 Hz.
