The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedint...The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedinterlayer with a crack perpendicular to the boundaries. The impact load is applied on the face of the crack. Fourier transform and Laplace transform methods are used to formulate the present problem in terms of a singular integral equation in Laplace transform domain. Considering variations of parameters such as the nonhomogeneity constant, the thickness ratio and the crack length, the dynamic stress intensity factors （DSIFs） in time domain are studied and some meaningful conclusions are obtained.展开更多
The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of ene...The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of energy stability is solved with the method of descending exponentials. The disturbance energy is found to be able to grow to 11.62 times as large as the initial disturbance energy for Pr = 0.72 when the Grashof number is between the critical Grashof numbers of the energy stability and the linear stability. We prove that, with a weighted energy method, the basic flow of the vertical buoyancy boundary layer is stable to finite-amplitude streamwise-independent disturbances.展开更多
In recent years, the anisotropic study has become a hot topic in the field of electromagnetics. Currently, inversion technologies of transient electromagnetic sounding data are mainly based on the case of an isotropic...In recent years, the anisotropic study has become a hot topic in the field of electromagnetics. Currently, inversion technologies of transient electromagnetic sounding data are mainly based on the case of an isotropic medium. However, the actual underground electrical structure tends to be complicated and anisotropic. It is often found that the isotropic inversion technologies do not lead to good results for field transient electromagnetic sounding data. We have developed an algorithm for calculating the transient electromagnetic response in a layered medium with azimuthal anisotropy. An occam inversion algorithm has also been implemented to invert the transient electromagnetic data induced by a grounded horizontal electric dipole in a layered medium with azimuthal anisotropy. Synthetic examples demonstrate the stability and validity of the inversion algorithm. Experimental results show different data for inverting have great influence on the inversion results.展开更多
Non-metallic inclusion distribution in the surface layer of IF steel slabs during unsteady casting was investigated using the original position statistic distribution analysis（OPA）method.It was found that most non-m...Non-metallic inclusion distribution in the surface layer of IF steel slabs during unsteady casting was investigated using the original position statistic distribution analysis（OPA）method.It was found that most non-metallic inclusions larger than 10 μm existed in the subsurface layers of 0.5-3.5 mm from the slab surfaces and very few large non-metallic inclusions were found in the inner regions（≥4.5 mm from slab surfaces）.In addition,it was found that at high casting speed level（1.4 m/min）,even a slight change of casting speed could result in a remarkable increase of the non-metallic inclusions.Thus,at high casting speed,changing the casting speed should be avoided or considerably lower speed changing rate must be used.展开更多
In the investigation of debris flow, the detection of the source area of the post-disaster debris flow is an important basis for evaluating the distribution of the debris flow accumulation layer and the subsequent con...In the investigation of debris flow, the detection of the source area of the post-disaster debris flow is an important basis for evaluating the distribution of the debris flow accumulation layer and the subsequent control. In this paper, a shallow high-resolution TEM is used to detect the debris flow source area in Dashigou village, Yongji County, Jilin Province. The purpose of this investigation is to determine the depth range of debris flow damage. The detection results show that there is an obvious low resistance zone at about 10 m depth along the survey line, which is in good agreement with the drilling data and the high density electrical detection. It is proved that the depth is the maximum impact depth of the debris flow. The practical engineering proves that the method has high resolution in shallow layer detection, high efficiency and convenience in field acquisition. The maximum detection depth range of this method is 30--40 m, which meets the requirements of high efficiency and accurate detection for regional debris flow source area, and has high practical application value.展开更多
Novel exact solutions of one-dimensional transient dynamic piezoelectric problems for thickness polarized layers and disks, or length polarized rods, are obtained. The solutions are derived using a time-domain Green’...Novel exact solutions of one-dimensional transient dynamic piezoelectric problems for thickness polarized layers and disks, or length polarized rods, are obtained. The solutions are derived using a time-domain Green’s function method that leads to an exact analytical recursive procedure which is applicable for a wide variety of boundary conditions including nonlinear cases. A nonlinear damper boundary condition is considered in more detail. The corresponding nonlinear relationship between stresses and velocities at a current time moment is used in the recursive procedure. In addition to the exact recursive procedure that is effective for calculations, some new practically important explicit exact solutions are presented. Several examples of the time behavior of the output electric potential difference are given to illustrate the effectiveness of the proposed exact approach.展开更多
Dynamics in partial transient liquid phase bonding (PTLP bonding) of Si_3N_4 ceramic with Ti/Cu/Ti multi-interlayer was systematically studied through micro-analysis of joint interfaces. The results show that growth o...Dynamics in partial transient liquid phase bonding (PTLP bonding) of Si_3N_4 ceramic with Ti/Cu/Ti multi-interlayer was systematically studied through micro-analysis of joint interfaces. The results show that growth of reaction layer and isothermal solidification procession do at the same time. Growth of reaction layer and moving of isothermal solidification interface obey the parabolic law governed by the diffusion of participating elements during the PTLP bonding. Coordination of the above two dynamics process is done through time and temperature. When reaction layer thickness is suitable and isothermal solidification process is finished, the high bonding strength at room temperature and high temperature are obtained.展开更多
基金the National Science Foundation for Excellent Young Investigators(10325208)the National Natural Science Foundation of China(10432030)the China Postdoctoral Science Foundation(2004036018)
文摘The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedinterlayer with a crack perpendicular to the boundaries. The impact load is applied on the face of the crack. Fourier transform and Laplace transform methods are used to formulate the present problem in terms of a singular integral equation in Laplace transform domain. Considering variations of parameters such as the nonhomogeneity constant, the thickness ratio and the crack length, the dynamic stress intensity factors （DSIFs） in time domain are studied and some meaningful conclusions are obtained.
基金Project supported by the National Natural Science Foundation of China(Nos.11225209,11490553,and 11521091)
文摘The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of energy stability is solved with the method of descending exponentials. The disturbance energy is found to be able to grow to 11.62 times as large as the initial disturbance energy for Pr = 0.72 when the Grashof number is between the critical Grashof numbers of the energy stability and the linear stability. We prove that, with a weighted energy method, the basic flow of the vertical buoyancy boundary layer is stable to finite-amplitude streamwise-independent disturbances.
文摘In recent years, the anisotropic study has become a hot topic in the field of electromagnetics. Currently, inversion technologies of transient electromagnetic sounding data are mainly based on the case of an isotropic medium. However, the actual underground electrical structure tends to be complicated and anisotropic. It is often found that the isotropic inversion technologies do not lead to good results for field transient electromagnetic sounding data. We have developed an algorithm for calculating the transient electromagnetic response in a layered medium with azimuthal anisotropy. An occam inversion algorithm has also been implemented to invert the transient electromagnetic data induced by a grounded horizontal electric dipole in a layered medium with azimuthal anisotropy. Synthetic examples demonstrate the stability and validity of the inversion algorithm. Experimental results show different data for inverting have great influence on the inversion results.
文摘Non-metallic inclusion distribution in the surface layer of IF steel slabs during unsteady casting was investigated using the original position statistic distribution analysis（OPA）method.It was found that most non-metallic inclusions larger than 10 μm existed in the subsurface layers of 0.5-3.5 mm from the slab surfaces and very few large non-metallic inclusions were found in the inner regions（≥4.5 mm from slab surfaces）.In addition,it was found that at high casting speed level（1.4 m/min）,even a slight change of casting speed could result in a remarkable increase of the non-metallic inclusions.Thus,at high casting speed,changing the casting speed should be avoided or considerably lower speed changing rate must be used.
文摘In the investigation of debris flow, the detection of the source area of the post-disaster debris flow is an important basis for evaluating the distribution of the debris flow accumulation layer and the subsequent control. In this paper, a shallow high-resolution TEM is used to detect the debris flow source area in Dashigou village, Yongji County, Jilin Province. The purpose of this investigation is to determine the depth range of debris flow damage. The detection results show that there is an obvious low resistance zone at about 10 m depth along the survey line, which is in good agreement with the drilling data and the high density electrical detection. It is proved that the depth is the maximum impact depth of the debris flow. The practical engineering proves that the method has high resolution in shallow layer detection, high efficiency and convenience in field acquisition. The maximum detection depth range of this method is 30--40 m, which meets the requirements of high efficiency and accurate detection for regional debris flow source area, and has high practical application value.
文摘Novel exact solutions of one-dimensional transient dynamic piezoelectric problems for thickness polarized layers and disks, or length polarized rods, are obtained. The solutions are derived using a time-domain Green’s function method that leads to an exact analytical recursive procedure which is applicable for a wide variety of boundary conditions including nonlinear cases. A nonlinear damper boundary condition is considered in more detail. The corresponding nonlinear relationship between stresses and velocities at a current time moment is used in the recursive procedure. In addition to the exact recursive procedure that is effective for calculations, some new practically important explicit exact solutions are presented. Several examples of the time behavior of the output electric potential difference are given to illustrate the effectiveness of the proposed exact approach.
文摘Dynamics in partial transient liquid phase bonding (PTLP bonding) of Si_3N_4 ceramic with Ti/Cu/Ti multi-interlayer was systematically studied through micro-analysis of joint interfaces. The results show that growth of reaction layer and isothermal solidification procession do at the same time. Growth of reaction layer and moving of isothermal solidification interface obey the parabolic law governed by the diffusion of participating elements during the PTLP bonding. Coordination of the above two dynamics process is done through time and temperature. When reaction layer thickness is suitable and isothermal solidification process is finished, the high bonding strength at room temperature and high temperature are obtained.
