Material properties of blank have a great effect on power spinning process of aluminum alloy parts with transverse inner rib.By using finite element(FE) and Taguchi method,the effects and significance of five key mate...Material properties of blank have a great effect on power spinning process of aluminum alloy parts with transverse inner rib.By using finite element(FE) and Taguchi method,the effects and significance of five key material parameters,namely,anisotropic index in thickness direction,yield strength,hardening exponent,strengthening factor and elastic modulus on the formability of inner rib,tendency of wall fracture and degree of inhomogeneous deformation of finished spun parts were obtained.The achievements provide an important guide for selecting reasonable spinning material,and are very significant for the optimum design and precision control of power spinning process of parts with transverse inner rib.展开更多
Currently,most rock physics models,used for evaluating the elastic properties of cracked or fractured media,take into account the crack properties,but not the background anisotropy.This creats the errors of in the ani...Currently,most rock physics models,used for evaluating the elastic properties of cracked or fractured media,take into account the crack properties,but not the background anisotropy.This creats the errors of in the anisotropy estimates by using fi eld logging data.In this work,based on the scattered wavefi eld theory,a sphere-equivalency method of elastic wave scattering was developed to accurately calculate the elastic properties of a vertical transversely isotropic solid containing aligned cracks.By setting the scattered wavefi eld due to a crack equal to that due to an equivalent sphere,an eff ective elastic stiff ness tensor was derived for the cracked medium.The stability and accuracy of the approach were determined for varying background anisotropy values.The results show that the anisotropy of the eff ective media is aff ected by cracks and background anisotropy for transversely isotropic background permeated by horizontally aligned cracks,especially for the elastic wave propagating along the horizontal direction.Meanwhile,the crack orientation has a signifi cant infl uence on the elastic wave velocity anisotropy.The theory was subsequently applied to model laboratory ultrasonic experimental data for artifi cially cracked samples and to model borehole acoustic anisotropy measurements.After considering the background anisotropy,the model shows an improvement in the agreement between theoretical predictions and measurement data,demonstrating that the present theory can adequately explain the anisotropic characteristics of cracked media.展开更多
A new method to reduce the numerical dispersion of the three-dimensional Alternating Di-rection Implicit Finite-Difference Time-Domain (3-D ADI-FDTD) method is proposed. Firstly,the numerical formulations of the 3-D A...A new method to reduce the numerical dispersion of the three-dimensional Alternating Di-rection Implicit Finite-Difference Time-Domain (3-D ADI-FDTD) method is proposed. Firstly,the numerical formulations of the 3-D ADI-FDTD method are modified with the artificial anisotropy,and the new numerical dispersion relation is derived. Secondly,the relative permittivity tensor of the artificial anisotropy can be obtained by the Adaptive Genetic Algorithm (AGA). In order to demon-strate the accuracy and efficiency of this new method,a monopole antenna is simulated as an exam-ple. And the numerical results and the computational requirements of the proposed method are com-pared with those of the conventional ADI-FDTD method and the measured data. In addition the re-duction of the numerical dispersion is investigated as the objective function of the AGA. It is found that this new method is accurate and efficient by choosing proper objective function.展开更多
The permeability and porosity of coal seams are anisotropic, and the variation of confining stress may induce deformation in coal samples. In order to study these characteristics, experiments and model analyses were c...The permeability and porosity of coal seams are anisotropic, and the variation of confining stress may induce deformation in coal samples. In order to study these characteristics, experiments and model analyses were conducted to understand the behaviors of anisotropic stress sensitivity of lean coal samples. The results showed as the closure of cleats and the generation of micro-cracks, the strong stress sensitivity of coal samples and the discrete changes in porosity were caused by confining pressure changes. In the compression period, the anisotropy trend first increased, and then decreased. In the direction perpendicular to the bedding plane, the permeability decrease rate and the irreversible damage rate were the highest. In the direction parallel to the cleats, permeability recovery rate was higher and the irreversible damage rate was lower along butt cleats. Compared to the cube root of permeability to porosity, a 1/6 power relationship was proved to be closer to the experiment results, the new relationship had the highest fit level in the face cleat direction, and the lowest fit level in the vertical direction展开更多
Residual stress continues to be important issues in shipbuilding. This paper demonstrates how the heat affected zone that results from welding could be identified nondestructively using MBN （magnetic Barkhausen noise...Residual stress continues to be important issues in shipbuilding. This paper demonstrates how the heat affected zone that results from welding could be identified nondestructively using MBN （magnetic Barkhausen noise） technique. A stress concentration region was created by placing a weld bead on a marine steel plate used in ship construction. MBN measurements were made on the back surface of the welded plate along the weld direction and perpendicular to it in a line that crosses the weld bead. The stress distribution as deduced from the MBN measurements was found to be anisotropic in the material of the heat affected zone. The heat induced anisotropy was completely eliminated by shot peening the HAZ material as revealed by MBN intensity. It was concluded that the directional MBN measurements could be used to characterize the induced anisotropy and hence assess the thermal residual stresses distribution near a localized stresses concentration regions imposed by welding.展开更多
During the seismic wave propagation process,as for the anisotropic lower medium,the speed is a function of the propagating direction.This article focuses on solving the problem how to get the transmittance angle and s...During the seismic wave propagation process,as for the anisotropic lower medium,the speed is a function of the propagating direction.This article focuses on solving the problem how to get the transmittance angle and speed,knowing the upper seismic wave propagation velocity and the angle of incidence conditions.The main theories used Snell law,Christoffel equation and speed characteristics.Taking the HTI medium as an example,the authors give the detailed solving process and draw the space velocity characteristic curve.展开更多
文摘针对传统边缘检测方法极易受高斯噪声和椒盐噪声影响导致的伪边缘问题,提出一种各向异性双窗非线性滤波的边缘检测算法。首先,构建各向异性高斯双窗滤波器,并结合灰度分层技术计算每个像素的非线性方向导数向量和边缘强度图(Edge Strength Map,ESM)。然后,根据导数向量最大值估计边缘方向图(Edge Direction Map,EDM)。最后,通过非极大值抑制和双阈值决策获得最终的边缘检测图。对比实验结果表明,所提算法在无噪声、高斯噪声、椒盐噪声和混合噪声干扰的环境下表现优异,尤其在混合噪声下的边缘检测结果明显优于其他算法,具有较强的混合噪声鲁棒性。
基金Projects(50405039,50575186) supported by the National Natural Science Foundation of ChinaProject(50225518) supported by the National Natural Science Foundation of China for Distinguished Young ScholarsProject(2008AA04Z122) supported by the National High-tech Research and Development Program of China
文摘Material properties of blank have a great effect on power spinning process of aluminum alloy parts with transverse inner rib.By using finite element(FE) and Taguchi method,the effects and significance of five key material parameters,namely,anisotropic index in thickness direction,yield strength,hardening exponent,strengthening factor and elastic modulus on the formability of inner rib,tendency of wall fracture and degree of inhomogeneous deformation of finished spun parts were obtained.The achievements provide an important guide for selecting reasonable spinning material,and are very significant for the optimum design and precision control of power spinning process of parts with transverse inner rib.
基金supported by the National Natural Science Foundation of China (No. 41821002)the Fundamental Research Funds for the Central Universities (Nos. 18CX02065A,20CX06046A)+3 种基金the Young Elite Scientist Sponsorship Program by the China Association for Science and TechnologyMajor Scientifi c and Technological Projects of CNPC (No. ZD2019-183-004)Qingdao Postdoctoral Applied Research Project (No. qdyy20190079)China Postdoctoral Science Foundation (No. 2020M672171)。
文摘Currently,most rock physics models,used for evaluating the elastic properties of cracked or fractured media,take into account the crack properties,but not the background anisotropy.This creats the errors of in the anisotropy estimates by using fi eld logging data.In this work,based on the scattered wavefi eld theory,a sphere-equivalency method of elastic wave scattering was developed to accurately calculate the elastic properties of a vertical transversely isotropic solid containing aligned cracks.By setting the scattered wavefi eld due to a crack equal to that due to an equivalent sphere,an eff ective elastic stiff ness tensor was derived for the cracked medium.The stability and accuracy of the approach were determined for varying background anisotropy values.The results show that the anisotropy of the eff ective media is aff ected by cracks and background anisotropy for transversely isotropic background permeated by horizontally aligned cracks,especially for the elastic wave propagating along the horizontal direction.Meanwhile,the crack orientation has a signifi cant infl uence on the elastic wave velocity anisotropy.The theory was subsequently applied to model laboratory ultrasonic experimental data for artifi cially cracked samples and to model borehole acoustic anisotropy measurements.After considering the background anisotropy,the model shows an improvement in the agreement between theoretical predictions and measurement data,demonstrating that the present theory can adequately explain the anisotropic characteristics of cracked media.
基金the National Natural Science Foundation of China (No. 60271012)Research Foundation of ZTE Corporation.
文摘A new method to reduce the numerical dispersion of the three-dimensional Alternating Di-rection Implicit Finite-Difference Time-Domain (3-D ADI-FDTD) method is proposed. Firstly,the numerical formulations of the 3-D ADI-FDTD method are modified with the artificial anisotropy,and the new numerical dispersion relation is derived. Secondly,the relative permittivity tensor of the artificial anisotropy can be obtained by the Adaptive Genetic Algorithm (AGA). In order to demon-strate the accuracy and efficiency of this new method,a monopole antenna is simulated as an exam-ple. And the numerical results and the computational requirements of the proposed method are com-pared with those of the conventional ADI-FDTD method and the measured data. In addition the re-duction of the numerical dispersion is investigated as the objective function of the AGA. It is found that this new method is accurate and efficient by choosing proper objective function.
基金＊ Supported by the National Science ＆ Technology Major Project of China （2011ZX05038-001） the National Natural Science Foundation of China （2009CB219604）
文摘The permeability and porosity of coal seams are anisotropic, and the variation of confining stress may induce deformation in coal samples. In order to study these characteristics, experiments and model analyses were conducted to understand the behaviors of anisotropic stress sensitivity of lean coal samples. The results showed as the closure of cleats and the generation of micro-cracks, the strong stress sensitivity of coal samples and the discrete changes in porosity were caused by confining pressure changes. In the compression period, the anisotropy trend first increased, and then decreased. In the direction perpendicular to the bedding plane, the permeability decrease rate and the irreversible damage rate were the highest. In the direction parallel to the cleats, permeability recovery rate was higher and the irreversible damage rate was lower along butt cleats. Compared to the cube root of permeability to porosity, a 1/6 power relationship was proved to be closer to the experiment results, the new relationship had the highest fit level in the face cleat direction, and the lowest fit level in the vertical direction
文摘Residual stress continues to be important issues in shipbuilding. This paper demonstrates how the heat affected zone that results from welding could be identified nondestructively using MBN （magnetic Barkhausen noise） technique. A stress concentration region was created by placing a weld bead on a marine steel plate used in ship construction. MBN measurements were made on the back surface of the welded plate along the weld direction and perpendicular to it in a line that crosses the weld bead. The stress distribution as deduced from the MBN measurements was found to be anisotropic in the material of the heat affected zone. The heat induced anisotropy was completely eliminated by shot peening the HAZ material as revealed by MBN intensity. It was concluded that the directional MBN measurements could be used to characterize the induced anisotropy and hence assess the thermal residual stresses distribution near a localized stresses concentration regions imposed by welding.
文摘During the seismic wave propagation process,as for the anisotropic lower medium,the speed is a function of the propagating direction.This article focuses on solving the problem how to get the transmittance angle and speed,knowing the upper seismic wave propagation velocity and the angle of incidence conditions.The main theories used Snell law,Christoffel equation and speed characteristics.Taking the HTI medium as an example,the authors give the detailed solving process and draw the space velocity characteristic curve.
