The present paper considers the scattering of the time harmonic stress wave by a single crack and two collinear cracks in functionally graded piezoelectric material （FGPM）. It is assumed that the properties of the F...The present paper considers the scattering of the time harmonic stress wave by a single crack and two collinear cracks in functionally graded piezoelectric material （FGPM）. It is assumed that the properties of the FGPM vary continuously as an exponential function. By using the Fourier transform and defining the jumps of displacements and electric potential components across the crack surface as the unknown functions, two pairs of dual integral equations are derived. To solve the dual integral equations, the jumps of the displacement and electric potential components across the crack surface are expanded in a series of Jacobi polynomials. Numerical examples are provided to show the influences of material properties on the dynamic stress and the electric displacement intensity factors.展开更多
The dynamic behavior of two parallel symmetric cracks in a piezoelectricstrip under harmonic anti-plane shear waves is studied using the Schmidt method for permeable cracksuface conditions. The cracks are parallel to ...The dynamic behavior of two parallel symmetric cracks in a piezoelectricstrip under harmonic anti-plane shear waves is studied using the Schmidt method for permeable cracksuface conditions. The cracks are parallel to the edge of the strip. By means of the Fouriertransform, the problem can be solved with the help of two pairs of dual integral equations. Theseequations are solved using the schmidt method. The results show that the stress and the electricdisplacement intensity factors depend on the geometry of the cracks, the frequency of incidentwaves, the distance between cracks and the thickness of the strip. It is also found that theelectric displacement intensity factors for the permeable crack surface conditions are much smallerthan those for the impermeable crack surface conditions.展开更多
In this paper, the interaction between two collinear cracks inpiezoelectric materials under anti-plane shear loading wasinvestigated for the impermeable crack face conditions. By using theFourier transform, the proble...In this paper, the interaction between two collinear cracks inpiezoelectric materials under anti-plane shear loading wasinvestigated for the impermeable crack face conditions. By using theFourier transform, the problem can be solved with two pairs of tripleintegral equations. These equations are solved using Schmidt'smethod. This process is quite different from that adopted previously.This makes it possible to understand the two collinear cracksinteraction in piezoelectric materials.展开更多
In this paper, the scattering of harmonic anti-plane shear wavesby a finite crack in infinitely long strip is studied using thenon-local theory. The Fourier transform is applied and a mixedboundary value problem is fo...In this paper, the scattering of harmonic anti-plane shear wavesby a finite crack in infinitely long strip is studied using thenon-local theory. The Fourier transform is applied and a mixedboundary value problem is formulated. Then a set of dual integralequations is solved using the Schmidt method instead of the first orthe second integral equation method. A one-dimensional non-localkernel is used instead of a two-di- mensional one for the anti-planedynamic problem to obtain the stress occurring at the crack tips.Contrary to the classical elasticity solution, it is found that nostress singularity is present at the crack tip. The non-local dynamicelastic solutions yield a finite hoop stress at the crack tip, thusallowing for a fracture criterion based on the maximum dynamic stresshypothesis. The finite hoop stress at the crack tip depends on thecrack length, the width of the strip and the lattice parameters.展开更多
A series of compression tests were conducted to investigate the mechanical properties and failure mechanisms of carbon fiber composite sandwich panels using pyramidal truss cores subjected to temperatures ranging from...A series of compression tests were conducted to investigate the mechanical properties and failure mechanisms of carbon fiber composite sandwich panels using pyramidal truss cores subjected to temperatures ranging from 100℃ to 350℃.The compressive strength and stiffness of sandwich panels decreased as temperature increased.Cryogenic temperatures caused an increase in strength and stiffness,while elevated temperatures resulted in a reduction of strength and stiffness.The effect of temperature on the failure mode of the sandwich panel was revealed as well.The interface between the fiber and matrix was examined by a scanning electron microscope(SEM) in order to study the effect of temperature on strengthening the mechanism and good bonding conditions within the fiber-matrix interface was observed at cryogenic temperatures.The comparison of the predicted and experimental data indicated that the stiffness and strength of the composite sandwich panels for temperature variation was consistent.展开更多
In this paper, the dynamic stress field near crack tips in the functionally graded materials subjected to the harmonic anti-plane shear stress waves was investi- gated by means of the non-local theory. The traditional...In this paper, the dynamic stress field near crack tips in the functionally graded materials subjected to the harmonic anti-plane shear stress waves was investi- gated by means of the non-local theory. The traditional concepts of the non-local theory were extended to solve the fracture problem of functionally graded materials. To make the analysis tractable, it was assumed that the material properties vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of a pair of dual integral equations, in which the unknown variable was the displacement on the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces was expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solutions yield a finite hoop stress at crack tips, thus allowing us to use the maximum stress as a fracture criterion. The magnitude of the finite dynamic stress field depends on the crack length, the parameter describing the functionally graded materials, the circular frequency of the incident waves and the lattice parameter of materials.展开更多
The non-local theory solution to two collinear limited-permeable mode-I cracks in a piezoelectric/piezomagnetic medium was investigated by using the generalized Almansi's theorem and the Schmidt method in the pres...The non-local theory solution to two collinear limited-permeable mode-I cracks in a piezoelectric/piezomagnetic medium was investigated by using the generalized Almansi's theorem and the Schmidt method in the present paper. The problem was formulated through Fourier transformation into two pairs of dual integral equations, in which the unknown variables are the displacement jumps across the crack surfaces. For solving the dual integral equations, the displacement jumps across the crack surfaces were directly expanded as a series of Jacobi polynomials. Numerical examples were provided to show the effects of the crack length, the distance between the two collinear cracks, the lattice parameter, the electric permittivity and the magnetic permeability of the air inside the crack on the stress fields, the electric displacement fields and the magnetic flux fields near the crack tips in a piezoelectric/piezomagnetic medium. Different from the classical solutions, the present solution exhibits no stress, electric displacement and magnetic flux singularities at the crack tips in a piezoelectric/piezomagnetic medium.展开更多
基金Project supported by the National Natural Science Foundation for Distinguished Young Scholars (No. 10325208),the National Natural Science Foundation of China (No.10430230)the China Postdoctral Science Foundation (No.2005037640).
文摘The present paper considers the scattering of the time harmonic stress wave by a single crack and two collinear cracks in functionally graded piezoelectric material （FGPM）. It is assumed that the properties of the FGPM vary continuously as an exponential function. By using the Fourier transform and defining the jumps of displacements and electric potential components across the crack surface as the unknown functions, two pairs of dual integral equations are derived. To solve the dual integral equations, the jumps of the displacement and electric potential components across the crack surface are expanded in a series of Jacobi polynomials. Numerical examples are provided to show the influences of material properties on the dynamic stress and the electric displacement intensity factors.
基金the Post Doctoral Science Foundation of Heilongjiang Provincethe Natural Science Foundation of Heilongjiang Province+1 种基金the National Science Foundation with the Excellent Young Investigator Award (No.19725209)the Scientific Research Foundation of Harbin Institute of Technology (HIT.2000.30)
文摘The dynamic behavior of two parallel symmetric cracks in a piezoelectricstrip under harmonic anti-plane shear waves is studied using the Schmidt method for permeable cracksuface conditions. The cracks are parallel to the edge of the strip. By means of the Fouriertransform, the problem can be solved with the help of two pairs of dual integral equations. Theseequations are solved using the schmidt method. The results show that the stress and the electricdisplacement intensity factors depend on the geometry of the cracks, the frequency of incidentwaves, the distance between cracks and the thickness of the strip. It is also found that theelectric displacement intensity factors for the permeable crack surface conditions are much smallerthan those for the impermeable crack surface conditions.
基金the Post-Doctoral Science Foundationthe Natural Science Foundation of Heilongjiang Province
文摘In this paper, the interaction between two collinear cracks inpiezoelectric materials under anti-plane shear loading wasinvestigated for the impermeable crack face conditions. By using theFourier transform, the problem can be solved with two pairs of tripleintegral equations. These equations are solved using Schmidt'smethod. This process is quite different from that adopted previously.This makes it possible to understand the two collinear cracksinteraction in piezoelectric materials.
基金the Post Doctoral Science Foundation of Heilongjiang Provincethe Natural Science Foundation of Heilongjiang Provincethe National Foundation for Excellent Young Investigators.
文摘In this paper, the scattering of harmonic anti-plane shear wavesby a finite crack in infinitely long strip is studied using thenon-local theory. The Fourier transform is applied and a mixedboundary value problem is formulated. Then a set of dual integralequations is solved using the Schmidt method instead of the first orthe second integral equation method. A one-dimensional non-localkernel is used instead of a two-di- mensional one for the anti-planedynamic problem to obtain the stress occurring at the crack tips.Contrary to the classical elasticity solution, it is found that nostress singularity is present at the crack tip. The non-local dynamicelastic solutions yield a finite hoop stress at the crack tip, thusallowing for a fracture criterion based on the maximum dynamic stresshypothesis. The finite hoop stress at the crack tip depends on thecrack length, the width of the strip and the lattice parameters.
基金supported by the National Natural Science Foundation of China (Grant Nos. 90816024 and 11272105)the Major State Basic Research Development Program of China (Grant No. 2011CB610303)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20092302110006)
文摘A series of compression tests were conducted to investigate the mechanical properties and failure mechanisms of carbon fiber composite sandwich panels using pyramidal truss cores subjected to temperatures ranging from 100℃ to 350℃.The compressive strength and stiffness of sandwich panels decreased as temperature increased.Cryogenic temperatures caused an increase in strength and stiffness,while elevated temperatures resulted in a reduction of strength and stiffness.The effect of temperature on the failure mode of the sandwich panel was revealed as well.The interface between the fiber and matrix was examined by a scanning electron microscope(SEM) in order to study the effect of temperature on strengthening the mechanism and good bonding conditions within the fiber-matrix interface was observed at cryogenic temperatures.The comparison of the predicted and experimental data indicated that the stiffness and strength of the composite sandwich panels for temperature variation was consistent.
基金Supported by the Natural Science Foundation with Excellent Young Investigators of Heilongjiang Province (Grant No. JC04-08)the National Science Foundation with Excellent Young Investigators (Grant No. 10325208)+1 种基金the National Natural Science Foundation of China (Grant No. 10572043)the National Natural Science Key Item Foundation of China (Grant No. 10432030)
文摘In this paper, the dynamic stress field near crack tips in the functionally graded materials subjected to the harmonic anti-plane shear stress waves was investi- gated by means of the non-local theory. The traditional concepts of the non-local theory were extended to solve the fracture problem of functionally graded materials. To make the analysis tractable, it was assumed that the material properties vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of a pair of dual integral equations, in which the unknown variable was the displacement on the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces was expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solutions yield a finite hoop stress at crack tips, thus allowing us to use the maximum stress as a fracture criterion. The magnitude of the finite dynamic stress field depends on the crack length, the parameter describing the functionally graded materials, the circular frequency of the incident waves and the lattice parameter of materials.
基金supported by the National Natural Science Foundation of China (Grant No. 10872057)the Research Fund for the Doctoral Program of Higher Education of China (Grant No.20092302110006)the Natural Science Foundation of Heilongjiang Province (Grant No. A2007-05)
文摘The non-local theory solution to two collinear limited-permeable mode-I cracks in a piezoelectric/piezomagnetic medium was investigated by using the generalized Almansi's theorem and the Schmidt method in the present paper. The problem was formulated through Fourier transformation into two pairs of dual integral equations, in which the unknown variables are the displacement jumps across the crack surfaces. For solving the dual integral equations, the displacement jumps across the crack surfaces were directly expanded as a series of Jacobi polynomials. Numerical examples were provided to show the effects of the crack length, the distance between the two collinear cracks, the lattice parameter, the electric permittivity and the magnetic permeability of the air inside the crack on the stress fields, the electric displacement fields and the magnetic flux fields near the crack tips in a piezoelectric/piezomagnetic medium. Different from the classical solutions, the present solution exhibits no stress, electric displacement and magnetic flux singularities at the crack tips in a piezoelectric/piezomagnetic medium.
