Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distri...Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distributions of geometrically necessary dislocation（GND） density around the indentations within TA15 titanium alloy.The nano-indention tests were conducted on α and β phases,respectively.The residual stress strain fields surrounding the indentation were calculated through crosscorrelation method from recorded patterns.The GND density distribution around the indentation was calculated based on the strain gradient theories to reveal the micro-mechanism of plastic deformation.The results indicate that the elastic modulus and hardness for α p hase are 129.05 GPas and 6.44 GPa,while for β phase,their values are 109.80 GPa and 4.29 GPa,respectively.The residual Mises stress distribution around the indentation is relatively heterogeneous and significantly influenced by neighboring soft β phase.The region with low residual stress around the indentation is accompanied with markedly high a type and prismatic-GND density.展开更多
The stress and strain fields in self-organized growth coherent quantum dots （QD） structures are investigated in detail by two-dimension and three-dimension finite element analyses for lensed-shaped QDs. The nonobjec...The stress and strain fields in self-organized growth coherent quantum dots （QD） structures are investigated in detail by two-dimension and three-dimension finite element analyses for lensed-shaped QDs. The nonobjective isolate quantum dot system is used. The calculated results can he directly used to evaluate the conductive band and valence band confinement potential and strain introduced by the effective mass of the charge carriers in strain QD.展开更多
Based on the time series of GPS station coordinate in the international Earth reference frame （ITRF）, we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show ...Based on the time series of GPS station coordinate in the international Earth reference frame （ITRF）, we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show that the annual micro-behavior of strain field is divided into two parts by the north-south earthquake belt in the research region. The prevailing direction of compressive principal strain field is nearly consistent in the western region. From west to east, the direction varies from NS to NE. It is in accordance with the direction of the modem compressive principal strain field. This suggests that geologic deformation in western region was mainly caused by that India tectonic plate pushes the research region northward and the Siberia plate pushes it southward relatively. It is an inheritance of new tectonic motion. The prevailing direction of the compressive principal strain field does not exist in the eastern region .The annual biggest shear strain is different greatly in every grid-cell. The values varies from 4.13×10^-8 to 7.0×10^-10. By and large the annual biggest shear strain in the western region is bigger than that in the eastern region. And so is the variation between any two consecutive biggest annual shear strains in the same grid-cell. The annual surface dilatation show that in most grid-cells of the research region the surface dilatation is in compressibility, and the variation between any two consecutive annual surface dilatation in the same grid-cell is small.展开更多
On the basis of the GPS data obtained from repeated measurements carried out in 2004 and 2007,the horizontal principal strain of the Chinese mainland is calculated,which shows that the direction of principal compressi...On the basis of the GPS data obtained from repeated measurements carried out in 2004 and 2007,the horizontal principal strain of the Chinese mainland is calculated,which shows that the direction of principal compressive strain axis of each subplate is basically consistent with the P-axis of focal mechanism solution and the principal compressive stress axis acquired by geological method.It indicates that the crustal tectonic stress field is relatively stable in regions in a long time.The principal compressive stress axes of Qinghai-Tibet and Xinjiang subplates in the western part of Chinese mainland direct to NS and NNE-SSW,which are controlled by the force from the col-lision of the Eurasia Plate and India Plate.The principal compressive strain axes of Heilongjiang and North China subplates in the eastern part direct to ENE-WSW,which shows that they are subject to the force from the collision and underthrust of the Eurasia Plate to the North America and Pacific plates.At the same time,they are also af-fected by the lateral force from Qinghai-Tibet and Xinjiang subplates.The principal compressive strain axis of South China plate is WNW-ESE,which reflects that it is affected by the force from the collision of Philippine Sea Plate and Eurasia Plate and it is also subject to the lateral force from Qinghai-Tibet subplate.It is apparent from the comparison between the principal compressive strain axes in the periods of 2004～2007 and 2001～2004 that the acting directions of principal compressive stress of subplates in both periods are basically consistent.However,there is certain difference between their directional concentrations of principal compressive stress axes.The sur-face strain rates of different tectonic units in both periods indicate that the events predominating by compressive variation decrease,while the events predominating by tensile change increase.展开更多
The current crustal horizontal strain field is given in the paper based on the horizontal movement rates obtained from about 400 GPS stations located in Chinese mainland and its surrounding areas. The results show: a)...The current crustal horizontal strain field is given in the paper based on the horizontal movement rates obtained from about 400 GPS stations located in Chinese mainland and its surrounding areas. The results show: a) The horizontal strain in Chinese mainland is strong in the west and weak in the east and the shear strain is larger than the normal strain (absolute magnitude). The general strain magnitude is 10-8/a and in local regions is 10-7/a, but the strain distribution is not homogeneous; b) The regions with the most significant NS-trending strains are the Himalayas belt along the western segment of Chinese southern boundary, the segment of 36N~42N along the western boundary and the northern margin of Qaidam block; c) The EW-trending strain variation along the western margin is the maximum and it is characterized by the alternatively positive and negative variations from the west to the east; d) The regions with larger magnitudes of REN (NE-trending shear strain) and Rmax (maximum shear strain) are Himalayas belt, the segment of 36N~42N along the western boundary, the western part of Qaidam block, Sichuan-Yunnan (Chuan-Dian) rhombic block and the border area of Alxa, Qilian and Tarim blocks; e) The surrounding area of Qinghai-Xizang (Qingzang) block is mainly superfacial contraction and its interior is basically superfacial expansion. The area to its north is mainly superfacial contraction with the maximum magnitude along the western boundary and the minimum magnitude in the eastern part (except Yanshan tectonic zone); f) In the west of the western part, the principal compressive strain is in the SN direction and the principal tensile strain is in the EW direction, while in the eastern margin area of the western part, the principal compressive strain is proximate EW and the principal tensile strain is about SN. The principal strain direction of Chuan-Dian rhombic block has changed greatly. In the northern part, it is compression in the EW and tension in the SN, while in the southern part, it is just the opposite; g) The strain pattern in Chinese mainland might be the integration of block mode and successive deformation mode. In addition, the shear strain might be the small-scale dominant strain. Such a result might be resulted from the collision of Indian plate and the boundaries coupling, and it is also closely related to the motion of deep-seated matters and the physical nature of crustal medium. Therefore, it should be noted that since the GPS stations are not homogenous in spatial distribution, the obtained strain fields and the scales of the strain should be different.展开更多
Uniaxial tension tests were conducted on single-edge-notched tensile specimens of pure molybdenum with a mesh grid pattern in front of the notch. A series of images of crack initialization and propagation with a disto...Uniaxial tension tests were conducted on single-edge-notched tensile specimens of pure molybdenum with a mesh grid pattern in front of the notch. A series of images of crack initialization and propagation with a distorted mesh grid pattern were obtained by means of in situ scanning electron microscopy. Strain fields around the crack tip were mapped successively using geometric phase analysis and digital image correlation techniques, and then compared with the predictions obtained through linear elastic fracture mechanics （LEFM）. The comparison shows that the measured strain distribution ahead of the crack tip is consistent with the LEFM predictions of up to 25 μm from the crack tip.展开更多
The particle image velocimetry (PIV) method was used to investigate the full-field displacements and strains of the limestone specimen under external loads from the video images captured during the laboratory tests.Th...The particle image velocimetry (PIV) method was used to investigate the full-field displacements and strains of the limestone specimen under external loads from the video images captured during the laboratory tests.The original colorful video images and experimental data were obtained from the uniaxial compression test of a limestone.To eliminate perspective errors and lens distortion,the camera was placed normal to the rock specimen exposure.After converted into a readable format of frame images,these videos were transformed into the responding grayscale images,and the frame images were then extracted.The full-field displacement field was obtained by using the PIV technique,and interpolated in the sub-pixel locations.The displacement was measured in the plane of the image and inferred from two consecutive images.The local displacement vectors were calculated for small sub-windows of the images by means of cross-correlation.The video images were interrogated in a multi-pass way,starting off with 64×64 images,ending with 16×16 images after 6 iterations,and using 75% overlap of the sub-windows.In order to remove spurious vectors,the displacements were filtered using four filters:signal-to-noise ratio filter,peak height filter,global filter and local filter.The cubic interpolation was utilized if the displacements without a number were encountered.The full-field strain was then obtained using the local least square method from the discrete displacements.The strain change with time at different locations was also investigated.It is found that the normal strains are dependant on the locations and the crack distributions.Between 1.0 and 5.0 s prior to the specimen failure,normal strains increase rapidly at many locations,while a stable status appears at some locations.When the specimen is in a failure status,a large rotation occurs and it increases in the inverse direction.The strain concentration bands do not completely develop into the large cracks,and meso-cracks are not visible in some bands.The techniques presented here may improve the traditional measurement of the strain field,and may provide a lot of valuable information in investigating the deformation/failure mechanism of rock materials.展开更多
In order to study the damage mechanism of asphalt mixture,it is important to obtain the distribution of displacement and strain of its sample in the indirect tension mode.As a result,the digital image correlation meth...In order to study the damage mechanism of asphalt mixture,it is important to obtain the distribution of displacement and strain of its sample in the indirect tension mode.As a result,the digital image correlation method (DICM) was used to evaluate the displacement field and strain field of asphalt mixture.The results showed that the displacement fields under DICM and ABAQUS are similarly;the strain fields are different due to the different modulus of mastic and aggregate;and DICM is an practical method to study the indirect tension displacement and stain.展开更多
Surface strain fields of the designed compact tension(CT)specimens were investigated by digital image correlation(DIC)method.An integrative computer program was developed based on DIC algorithms to characterize the st...Surface strain fields of the designed compact tension(CT)specimens were investigated by digital image correlation(DIC)method.An integrative computer program was developed based on DIC algorithms to characterize the strain fields accurately and graphically.Strain distribution of the CT specimen was predicted by finite element method(FEM).Good agreement is observed between the surface strain fields measured by DIC and predicted by FEM,which reveals that the proposed method is practical and effective to determine the strain fields of CT specimens.Moreover,strain fields of the CT specimens with various compressive loads and notch diameters were studied by DIC.The experimental results can provide effective reference to usage of CT specimens in triaxial creep test by appropriately selecting specimen and experiment parameters.展开更多
Based on dislocation theory of 0kada, we adopted a finite-element fault model inverted by Gavin Hayes from seismic data for the 2011 Japan Mw9.0 earthquake, and obtained the corresponding surface displacement and stra...Based on dislocation theory of 0kada, we adopted a finite-element fault model inverted by Gavin Hayes from seismic data for the 2011 Japan Mw9.0 earthquake, and obtained the corresponding surface displacement and strain fields. The calculated displacement field is consistent with the observed GPS results in the trend of changes. Also the surface displacement and strain fields both show large variations in space.展开更多
In this paper, we analyze the crustal movements, strain field changes and large scale dynamic characteristics of horizontal deformation before the Wenchuan earthquake （ Ms = 8.0） using GPS data obtained from the Cru...In this paper, we analyze the crustal movements, strain field changes and large scale dynamic characteristics of horizontal deformation before the Wenchuan earthquake （ Ms = 8.0） using GPS data obtained from the Crustal Movement Observation Network of China. The following issues are discussed. First, the strain fields of the Longmeushan fault zone located at the epicenter show slow accumulation, because of the tectonic dynamics process subjected to the eastward movement of the Bayan Har block. Second, the different movements between the Longmenshan fault and South China block are smaller than the errors of GPS observation. Third, the high value of compressive strain （2004 - 2007） is located at the epicenter, which shows that the local squeezing action is stronger than before. Fourth, the data from GPS reference stations in the Chinese Mainland show that crustal shortening is faster than before in the north-eastern direction, which is part of the background of the local tectonic dynamics increase in the Longmenshan fault zone.展开更多
This paper presents the application of Moire interferometry in measuring the displacement and strain field at notch-tip and crack-tip before and after crack propagation.The experiment is carried out using a three poin...This paper presents the application of Moire interferometry in measuring the displacement and strain field at notch-tip and crack-tip before and after crack propagation.The experiment is carried out using a three point bending beam with a notch.The N_x and N_y fringe patterns representing displacement field,and the ΔN_x/Δx and ΔN_y/Δy fringe patterns representing the strain field are obtained.The sensitivity of the meas- ured displacement is 0.417μm per fringe order.The displacement and strain distribution along the section x=0 have been worked out according to N_x and N_y fringe patterns.展开更多
On the basis of the three-dimensional elastic inclusion model, the analytic expression of viscoelastic strain field is derived, i.e., the analytic expression of viscoelastic strain at an arbitrary point (x, y, z) in x...On the basis of the three-dimensional elastic inclusion model, the analytic expression of viscoelastic strain field is derived, i.e., the analytic expression of viscoelastic strain at an arbitrary point (x, y, z) in x-axis, y-axis and z-axis produced by three-dimension inclusion in the semi-infinite rheologic medium defined by the standard linear rheologic model, namely the normal strains exx(r, t), eyy(r, t) and ezz(r, t), the shear strains exy(r, t) and eyx(r, t), eyz(r, t) and ezy(r, t), exz(r, t) and ezx(r, t), and the bulk-strain q (r, t). By computing the spatial-temporal variation of bulk strain on the ground produced by a spherical rheologic inclusion in a semi-infinite rheologic medium, we obtained some significant results that the bulk-strain variation with time produced by a hard inclusion has three stages (a, b, g) with different characteristics, which are similar to those of most geodetic deformation curves, but not the case for those by a soft inclusion. It is meaningful that these theoretical results have been applied to explain preliminarily the characteristics of stage variation of spatial-temporal evolution, the pattern and quadrant distribution of earthquake precursors, the changeability, spontaneity and complexity of short-term and imminent-term precursors. It offers a theoretical base to found the physical model of earthquake precursors and a reference to predict physically the earthquakes.展开更多
A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for a...A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for an array of dots was used for the strain calculation. The dependence of the strain energy density distribution on the thickness of the capping layer was investigated in detail when the elastic characteristics of the matrix material were anisotropic. It is shown that the elastic anisotropic greatly influences the stress, strain, and strain energy density in the quantum dot structures. The anisotropic ratio of the matrix material and the combination with different thicknesses of the capping layer, may lead to different strain energy density minimum locations on the capping layer surface, which can result in various vertical ordering phenomena for the next layer of quantum dots, i.e. partial alignment, random alignment, and complete alignment.展开更多
The cracking of coatings and the deformation of base frustrate the application of laser cladding technology especially on surface of the ring circular orbit.In order to solve the two problems above,the stress and stra...The cracking of coatings and the deformation of base frustrate the application of laser cladding technology especially on surface of the ring circular orbit.In order to solve the two problems above,the stress and strain fields of the laser cladding process on the ring circular orbit were analyzed through the finite-element method,based on the temperature field.The wedge module of the ring circular ring was the subject investigated. The calculating results show that during the cladding process the crank point tends to generate the transversal crack;the centre point on the coating/base interface tends to generate longitudinal crack;the intersecting edge of the coating and base tends to generate toe crack.Moreover,the cracking tendency of the outer marginal point is obviously greater than that of the inner marginal point.The rather high stress appears at the border position where the constraint exists,and the stress on the point in front of molten pool under the range of laser irradiation is large as well.And the displacement becomes larger as the cladding process proceeds.展开更多
Before the major earthquake or rock damage occurs,it is often accompanied by a sudden change in the degree of non-uniformity of the strain field.In order to find a stronger non-uniformity signal before the rock failur...Before the major earthquake or rock damage occurs,it is often accompanied by a sudden change in the degree of non-uniformity of the strain field.In order to find a stronger non-uniformity signal before the rock failure,the coefficient of variation(Cv)is examined and reformed in this study.We test the Cv calculation way of the"normal-abnormal"model proposed in the previous studies.Based on the analysis of the physical process of rock failure and its relationship to the shear strain field,we construct a new way to calculate the Cv value.The variation of shear strain field on rock sample with the increase of stress is obtained by the digital speckle correlation method(DSCM).The new Cv value calculation way is used to study the non-uniformity of the spatial distribution for the shear strain field.The results show that this Cv calculation way can get more obvious abnormal signals.When the number of observation points are limited,the specific distribution of points can increase the signal strength,which may provide reference for the research on precursor detection of earthquakes.展开更多
Based on the horizontal deformation field and the strain field derived from the GPS data over the period of 1999～2001 in the Yunnan area, the characteristics of deformation and strain in the northern part of Yunnan P...Based on the horizontal deformation field and the strain field derived from the GPS data over the period of 1999～2001 in the Yunnan area, the characteristics of deformation and strain in the northern part of Yunnan Province have been studied. The results indicate that the central part of the studied area is rather stable with little crustal displacement, while the western and eastern parts are active with larger displacement. The strain field reveals that the orientations of the principal compressive strain axis of the crust and the sub blocks in the area are NW SE, while the orientations of the principal tensile strain axis is NE SW. In the studied area, the tensile strain is predominatly in the northern part and the compressive strain is predominatly in the central and southern parts. The stretching direction of the shear strain contour is basically consistent with the strike of the active fault. The strain and stress fields of the fault activity are related to the structure where the fault is located, while the activity properties of the faults are different.展开更多
The dynamic strain field under the action of blasting load is measured by means of a super-dynamic strain system and a CS2092H dynamic measuring analysis system, and the relation between the peak valwe of strain and t...The dynamic strain field under the action of blasting load is measured by means of a super-dynamic strain system and a CS2092H dynamic measuring analysis system, and the relation between the peak valwe of strain and the quantity of explosive charge is obtained. And the authors probe into the mechanism of soot descaling of soot-delivery pipe under the action of blasting, and offer an effective method to clean soot in soot-delivery pipe. The study provides a theoretical basis for a further study on blasting descaling or soot-delivery pipe.展开更多
We present a new solution for the elastic displacement and strain fields on or near Earth’s surface due to rectangular faults in an anisotropic half-space,expressed as a summation of(A)the solution in an infinite spa...We present a new solution for the elastic displacement and strain fields on or near Earth’s surface due to rectangular faults in an anisotropic half-space,expressed as a summation of(A)the solution in an infinite space which is singular,and(B)the complementary part which is regular and well-behaved.These two solutions are expressed in terms of the mathematically elegant and computationally powerful Stroh formalism and can be applied to the generally anisotropic rock half-space or a transversely isotropic rock mass with any oriented plane of isotropy.For any flat fault of polygonal shape,one needs only to carry out a simple line integral from 0 to 7 r in order to express the fault-induced response.Numerical examples are presented to demonstrate the significant effect of the rock anisotropy and layer orientation on the fault-induced displacement and strain fields in anisotropic rocks.Potential applications are wide ranging,from faults in sedimentary strata to strongly deformed metamorphic rocks with steeply dipping foliation.展开更多
The relationship between the strain cumulative rate (i.e., the crustal strain rate, or CSR in short) and seismic activity is analyzed to develop a new method to determine risky regions for strong shocks within recent ...The relationship between the strain cumulative rate (i.e., the crustal strain rate, or CSR in short) and seismic activity is analyzed to develop a new method to determine risky regions for strong shocks within recent years by the recorded crustal strain field. Seismic activity, especially the recurrence period, is different in different areas. Ding Guoyu (1984) pointed out that, for different seismic regions, the difference in the recurrence period of strong earthquakes is mainly controlled by their difference in the rate of the tectonic movement, which is controlled by the seismogenic environment and the tectonic conditions. The method of determining the risky regions for strong shocks from the gradient of vertical strain rates observed in a geodetic survey is preliminarily tested with the earthquakes in recent years; the results show that this method is effective and useful for earthquake prediction. The relationship between CSR and seismicity in a specific region is studied with strain theories,展开更多
文摘Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distributions of geometrically necessary dislocation（GND） density around the indentations within TA15 titanium alloy.The nano-indention tests were conducted on α and β phases,respectively.The residual stress strain fields surrounding the indentation were calculated through crosscorrelation method from recorded patterns.The GND density distribution around the indentation was calculated based on the strain gradient theories to reveal the micro-mechanism of plastic deformation.The results indicate that the elastic modulus and hardness for α p hase are 129.05 GPas and 6.44 GPa,while for β phase,their values are 109.80 GPa and 4.29 GPa,respectively.The residual Mises stress distribution around the indentation is relatively heterogeneous and significantly influenced by neighboring soft β phase.The region with low residual stress around the indentation is accompanied with markedly high a type and prismatic-GND density.
文摘The stress and strain fields in self-organized growth coherent quantum dots （QD） structures are investigated in detail by two-dimension and three-dimension finite element analyses for lensed-shaped QDs. The nonobjective isolate quantum dot system is used. The calculated results can he directly used to evaluate the conductive band and valence band confinement potential and strain introduced by the effective mass of the charge carriers in strain QD.
基金National Natural Science Foundation of China (40074024).
文摘Based on the time series of GPS station coordinate in the international Earth reference frame （ITRF）, we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show that the annual micro-behavior of strain field is divided into two parts by the north-south earthquake belt in the research region. The prevailing direction of compressive principal strain field is nearly consistent in the western region. From west to east, the direction varies from NS to NE. It is in accordance with the direction of the modem compressive principal strain field. This suggests that geologic deformation in western region was mainly caused by that India tectonic plate pushes the research region northward and the Siberia plate pushes it southward relatively. It is an inheritance of new tectonic motion. The prevailing direction of the compressive principal strain field does not exist in the eastern region .The annual biggest shear strain is different greatly in every grid-cell. The values varies from 4.13×10^-8 to 7.0×10^-10. By and large the annual biggest shear strain in the western region is bigger than that in the eastern region. And so is the variation between any two consecutive biggest annual shear strains in the same grid-cell. The annual surface dilatation show that in most grid-cells of the research region the surface dilatation is in compressibility, and the variation between any two consecutive annual surface dilatation in the same grid-cell is small.
基金Project of State Science and Technology in the Eleventh "Five-year Plan" (2006BAC01B02-02-03).
文摘On the basis of the GPS data obtained from repeated measurements carried out in 2004 and 2007,the horizontal principal strain of the Chinese mainland is calculated,which shows that the direction of principal compressive strain axis of each subplate is basically consistent with the P-axis of focal mechanism solution and the principal compressive stress axis acquired by geological method.It indicates that the crustal tectonic stress field is relatively stable in regions in a long time.The principal compressive stress axes of Qinghai-Tibet and Xinjiang subplates in the western part of Chinese mainland direct to NS and NNE-SSW,which are controlled by the force from the col-lision of the Eurasia Plate and India Plate.The principal compressive strain axes of Heilongjiang and North China subplates in the eastern part direct to ENE-WSW,which shows that they are subject to the force from the collision and underthrust of the Eurasia Plate to the North America and Pacific plates.At the same time,they are also af-fected by the lateral force from Qinghai-Tibet and Xinjiang subplates.The principal compressive strain axis of South China plate is WNW-ESE,which reflects that it is affected by the force from the collision of Philippine Sea Plate and Eurasia Plate and it is also subject to the lateral force from Qinghai-Tibet subplate.It is apparent from the comparison between the principal compressive strain axes in the periods of 2004～2007 and 2001～2004 that the acting directions of principal compressive stress of subplates in both periods are basically consistent.However,there is certain difference between their directional concentrations of principal compressive stress axes.The sur-face strain rates of different tectonic units in both periods indicate that the events predominating by compressive variation decrease,while the events predominating by tensile change increase.
基金State Key Basic Research Development and Programming Project (G1998040703) the Project Physical Basic Study on Short-term Prediction for Strong Earthquakes during the tenth Five-Year Plan from Scientific and Technological Ministry.
文摘The current crustal horizontal strain field is given in the paper based on the horizontal movement rates obtained from about 400 GPS stations located in Chinese mainland and its surrounding areas. The results show: a) The horizontal strain in Chinese mainland is strong in the west and weak in the east and the shear strain is larger than the normal strain (absolute magnitude). The general strain magnitude is 10-8/a and in local regions is 10-7/a, but the strain distribution is not homogeneous; b) The regions with the most significant NS-trending strains are the Himalayas belt along the western segment of Chinese southern boundary, the segment of 36N~42N along the western boundary and the northern margin of Qaidam block; c) The EW-trending strain variation along the western margin is the maximum and it is characterized by the alternatively positive and negative variations from the west to the east; d) The regions with larger magnitudes of REN (NE-trending shear strain) and Rmax (maximum shear strain) are Himalayas belt, the segment of 36N~42N along the western boundary, the western part of Qaidam block, Sichuan-Yunnan (Chuan-Dian) rhombic block and the border area of Alxa, Qilian and Tarim blocks; e) The surrounding area of Qinghai-Xizang (Qingzang) block is mainly superfacial contraction and its interior is basically superfacial expansion. The area to its north is mainly superfacial contraction with the maximum magnitude along the western boundary and the minimum magnitude in the eastern part (except Yanshan tectonic zone); f) In the west of the western part, the principal compressive strain is in the SN direction and the principal tensile strain is in the EW direction, while in the eastern margin area of the western part, the principal compressive strain is proximate EW and the principal tensile strain is about SN. The principal strain direction of Chuan-Dian rhombic block has changed greatly. In the northern part, it is compression in the EW and tension in the SN, while in the southern part, it is just the opposite; g) The strain pattern in Chinese mainland might be the integration of block mode and successive deformation mode. In addition, the shear strain might be the small-scale dominant strain. Such a result might be resulted from the collision of Indian plate and the boundaries coupling, and it is also closely related to the motion of deep-seated matters and the physical nature of crustal medium. Therefore, it should be noted that since the GPS stations are not homogenous in spatial distribution, the obtained strain fields and the scales of the strain should be different.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11562016 and 11672175)
文摘Uniaxial tension tests were conducted on single-edge-notched tensile specimens of pure molybdenum with a mesh grid pattern in front of the notch. A series of images of crack initialization and propagation with a distorted mesh grid pattern were obtained by means of in situ scanning electron microscopy. Strain fields around the crack tip were mapped successively using geometric phase analysis and digital image correlation techniques, and then compared with the predictions obtained through linear elastic fracture mechanics （LEFM）. The comparison shows that the measured strain distribution ahead of the crack tip is consistent with the LEFM predictions of up to 25 μm from the crack tip.
基金Project(40972191) supported by the National Natural Science Foundation of ChinaProject(09YZ39) supported by the Creative Issue of Shanghai Education Committee,China
文摘The particle image velocimetry (PIV) method was used to investigate the full-field displacements and strains of the limestone specimen under external loads from the video images captured during the laboratory tests.The original colorful video images and experimental data were obtained from the uniaxial compression test of a limestone.To eliminate perspective errors and lens distortion,the camera was placed normal to the rock specimen exposure.After converted into a readable format of frame images,these videos were transformed into the responding grayscale images,and the frame images were then extracted.The full-field displacement field was obtained by using the PIV technique,and interpolated in the sub-pixel locations.The displacement was measured in the plane of the image and inferred from two consecutive images.The local displacement vectors were calculated for small sub-windows of the images by means of cross-correlation.The video images were interrogated in a multi-pass way,starting off with 64×64 images,ending with 16×16 images after 6 iterations,and using 75% overlap of the sub-windows.In order to remove spurious vectors,the displacements were filtered using four filters:signal-to-noise ratio filter,peak height filter,global filter and local filter.The cubic interpolation was utilized if the displacements without a number were encountered.The full-field strain was then obtained using the local least square method from the discrete displacements.The strain change with time at different locations was also investigated.It is found that the normal strains are dependant on the locations and the crack distributions.Between 1.0 and 5.0 s prior to the specimen failure,normal strains increase rapidly at many locations,while a stable status appears at some locations.When the specimen is in a failure status,a large rotation occurs and it increases in the inverse direction.The strain concentration bands do not completely develop into the large cracks,and meso-cracks are not visible in some bands.The techniques presented here may improve the traditional measurement of the strain field,and may provide a lot of valuable information in investigating the deformation/failure mechanism of rock materials.
基金Sponsored by the National Science and Technology Infrastructure Program (Grant No. 2006BAJ18B05)the National Natural Science Foundation of China(Grant No.50778057)+1 种基金Program for New Century Excellent Talents in University (Grant No. NCET-06-0340)the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20060213002)
文摘In order to study the damage mechanism of asphalt mixture,it is important to obtain the distribution of displacement and strain of its sample in the indirect tension mode.As a result,the digital image correlation method (DICM) was used to evaluate the displacement field and strain field of asphalt mixture.The results showed that the displacement fields under DICM and ABAQUS are similarly;the strain fields are different due to the different modulus of mastic and aggregate;and DICM is an practical method to study the indirect tension displacement and stain.
基金Projects(51575347,51405297,51204107)supported by the National Natural Science Foundation of China
文摘Surface strain fields of the designed compact tension(CT)specimens were investigated by digital image correlation(DIC)method.An integrative computer program was developed based on DIC algorithms to characterize the strain fields accurately and graphically.Strain distribution of the CT specimen was predicted by finite element method(FEM).Good agreement is observed between the surface strain fields measured by DIC and predicted by FEM,which reveals that the proposed method is practical and effective to determine the strain fields of CT specimens.Moreover,strain fields of the CT specimens with various compressive loads and notch diameters were studied by DIC.The experimental results can provide effective reference to usage of CT specimens in triaxial creep test by appropriately selecting specimen and experiment parameters.
基金supported by the Director Foundation of Institute of Seismology,CEA( IS201056088)
文摘Based on dislocation theory of 0kada, we adopted a finite-element fault model inverted by Gavin Hayes from seismic data for the 2011 Japan Mw9.0 earthquake, and obtained the corresponding surface displacement and strain fields. The calculated displacement field is consistent with the observed GPS results in the trend of changes. Also the surface displacement and strain fields both show large variations in space.
基金sponsored by the National Key Science and Technology R&D Program (2006BAC01B02-02-02)and National Natural Science Foundation of China(40674010)
文摘In this paper, we analyze the crustal movements, strain field changes and large scale dynamic characteristics of horizontal deformation before the Wenchuan earthquake （ Ms = 8.0） using GPS data obtained from the Crustal Movement Observation Network of China. The following issues are discussed. First, the strain fields of the Longmeushan fault zone located at the epicenter show slow accumulation, because of the tectonic dynamics process subjected to the eastward movement of the Bayan Har block. Second, the different movements between the Longmenshan fault and South China block are smaller than the errors of GPS observation. Third, the high value of compressive strain （2004 - 2007） is located at the epicenter, which shows that the local squeezing action is stronger than before. Fourth, the data from GPS reference stations in the Chinese Mainland show that crustal shortening is faster than before in the north-eastern direction, which is part of the background of the local tectonic dynamics increase in the Longmenshan fault zone.
基金The project supported by Chinese Academy of Sciences and National Natural Science Foundation of China
文摘This paper presents the application of Moire interferometry in measuring the displacement and strain field at notch-tip and crack-tip before and after crack propagation.The experiment is carried out using a three point bending beam with a notch.The N_x and N_y fringe patterns representing displacement field,and the ΔN_x/Δx and ΔN_y/Δy fringe patterns representing the strain field are obtained.The sensitivity of the meas- ured displacement is 0.417μm per fringe order.The displacement and strain distribution along the section x=0 have been worked out according to N_x and N_y fringe patterns.
基金Chinese Joint Seismological Science Foundation (101105).
文摘On the basis of the three-dimensional elastic inclusion model, the analytic expression of viscoelastic strain field is derived, i.e., the analytic expression of viscoelastic strain at an arbitrary point (x, y, z) in x-axis, y-axis and z-axis produced by three-dimension inclusion in the semi-infinite rheologic medium defined by the standard linear rheologic model, namely the normal strains exx(r, t), eyy(r, t) and ezz(r, t), the shear strains exy(r, t) and eyx(r, t), eyz(r, t) and ezy(r, t), exz(r, t) and ezx(r, t), and the bulk-strain q (r, t). By computing the spatial-temporal variation of bulk strain on the ground produced by a spherical rheologic inclusion in a semi-infinite rheologic medium, we obtained some significant results that the bulk-strain variation with time produced by a hard inclusion has three stages (a, b, g) with different characteristics, which are similar to those of most geodetic deformation curves, but not the case for those by a soft inclusion. It is meaningful that these theoretical results have been applied to explain preliminarily the characteristics of stage variation of spatial-temporal evolution, the pattern and quadrant distribution of earthquake precursors, the changeability, spontaneity and complexity of short-term and imminent-term precursors. It offers a theoretical base to found the physical model of earthquake precursors and a reference to predict physically the earthquakes.
基金This work was financially supported by the "973" National Basic Research Program of China (No. 2003CB314901)the National "863" High Technology Project of China (No. 2003AA311070)the Open Project of State Key Laboratory on Integrated Opto-electronics.
文摘A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for an array of dots was used for the strain calculation. The dependence of the strain energy density distribution on the thickness of the capping layer was investigated in detail when the elastic characteristics of the matrix material were anisotropic. It is shown that the elastic anisotropic greatly influences the stress, strain, and strain energy density in the quantum dot structures. The anisotropic ratio of the matrix material and the combination with different thicknesses of the capping layer, may lead to different strain energy density minimum locations on the capping layer surface, which can result in various vertical ordering phenomena for the next layer of quantum dots, i.e. partial alignment, random alignment, and complete alignment.
文摘The cracking of coatings and the deformation of base frustrate the application of laser cladding technology especially on surface of the ring circular orbit.In order to solve the two problems above,the stress and strain fields of the laser cladding process on the ring circular orbit were analyzed through the finite-element method,based on the temperature field.The wedge module of the ring circular ring was the subject investigated. The calculating results show that during the cladding process the crank point tends to generate the transversal crack;the centre point on the coating/base interface tends to generate longitudinal crack;the intersecting edge of the coating and base tends to generate toe crack.Moreover,the cracking tendency of the outer marginal point is obviously greater than that of the inner marginal point.The rather high stress appears at the border position where the constraint exists,and the stress on the point in front of molten pool under the range of laser irradiation is large as well.And the displacement becomes larger as the cladding process proceeds.
基金jointly supported by the China Postdoctoral Science Foundation(No.2018M630028)the National Natural Science Foundation of China(Nos.41274094,40821062 and 40872133).
文摘Before the major earthquake or rock damage occurs,it is often accompanied by a sudden change in the degree of non-uniformity of the strain field.In order to find a stronger non-uniformity signal before the rock failure,the coefficient of variation(Cv)is examined and reformed in this study.We test the Cv calculation way of the"normal-abnormal"model proposed in the previous studies.Based on the analysis of the physical process of rock failure and its relationship to the shear strain field,we construct a new way to calculate the Cv value.The variation of shear strain field on rock sample with the increase of stress is obtained by the digital speckle correlation method(DSCM).The new Cv value calculation way is used to study the non-uniformity of the spatial distribution for the shear strain field.The results show that this Cv calculation way can get more obvious abnormal signals.When the number of observation points are limited,the specific distribution of points can increase the signal strength,which may provide reference for the research on precursor detection of earthquakes.
文摘Based on the horizontal deformation field and the strain field derived from the GPS data over the period of 1999～2001 in the Yunnan area, the characteristics of deformation and strain in the northern part of Yunnan Province have been studied. The results indicate that the central part of the studied area is rather stable with little crustal displacement, while the western and eastern parts are active with larger displacement. The strain field reveals that the orientations of the principal compressive strain axis of the crust and the sub blocks in the area are NW SE, while the orientations of the principal tensile strain axis is NE SW. In the studied area, the tensile strain is predominatly in the northern part and the compressive strain is predominatly in the central and southern parts. The stretching direction of the shear strain contour is basically consistent with the strike of the active fault. The strain and stress fields of the fault activity are related to the structure where the fault is located, while the activity properties of the faults are different.
文摘The dynamic strain field under the action of blasting load is measured by means of a super-dynamic strain system and a CS2092H dynamic measuring analysis system, and the relation between the peak valwe of strain and the quantity of explosive charge is obtained. And the authors probe into the mechanism of soot descaling of soot-delivery pipe under the action of blasting, and offer an effective method to clean soot in soot-delivery pipe. The study provides a theoretical basis for a further study on blasting descaling or soot-delivery pipe.
基金the China Scholarship Council(CSC) for supporting her visit at the University of Akron
文摘We present a new solution for the elastic displacement and strain fields on or near Earth’s surface due to rectangular faults in an anisotropic half-space,expressed as a summation of(A)the solution in an infinite space which is singular,and(B)the complementary part which is regular and well-behaved.These two solutions are expressed in terms of the mathematically elegant and computationally powerful Stroh formalism and can be applied to the generally anisotropic rock half-space or a transversely isotropic rock mass with any oriented plane of isotropy.For any flat fault of polygonal shape,one needs only to carry out a simple line integral from 0 to 7 r in order to express the fault-induced response.Numerical examples are presented to demonstrate the significant effect of the rock anisotropy and layer orientation on the fault-induced displacement and strain fields in anisotropic rocks.Potential applications are wide ranging,from faults in sedimentary strata to strongly deformed metamorphic rocks with steeply dipping foliation.
基金1998. This project was sponsored by the National Science Foundation (96-913-03-03-02), China.
文摘The relationship between the strain cumulative rate (i.e., the crustal strain rate, or CSR in short) and seismic activity is analyzed to develop a new method to determine risky regions for strong shocks within recent years by the recorded crustal strain field. Seismic activity, especially the recurrence period, is different in different areas. Ding Guoyu (1984) pointed out that, for different seismic regions, the difference in the recurrence period of strong earthquakes is mainly controlled by their difference in the rate of the tectonic movement, which is controlled by the seismogenic environment and the tectonic conditions. The method of determining the risky regions for strong shocks from the gradient of vertical strain rates observed in a geodetic survey is preliminarily tested with the earthquakes in recent years; the results show that this method is effective and useful for earthquake prediction. The relationship between CSR and seismicity in a specific region is studied with strain theories,
