The Experts below are selected from a list of 33033 Experts worldwide ranked by ideXlab platform
Gustau Catalan - One of the best experts on this subject based on the ideXlab platform.
-
large flexoelectric anisotropy in paraelectric barium titanate
Physical Review Letters, 2015Co-Authors: Jackeline Narvaez, Sahar Saremi, Jiawang Hong, Massimiliano Stengel, Gustau CatalanAbstract:The bending-induced polarization of barium titanate single crystals has been measured with an aim to elucidate the origin of the large difference between theoretically predicted and experimentally measured flexoelectricity in this Material. The results indicate that part of the difference is due to polar regions (short-range order) that exist above T(C) and up to T*≈200-225 °C. Above T*, however, the flexovoltage coefficient still shows an unexpectedly large anisotropy for a Cubic Material, with (001)-oriented crystals displaying 10 times more flexoelectricity than (111)-oriented crystals. Theoretical analysis shows that this anisotropy cannot be a bulk property, and we therefore interpret it as indirect evidence for the theoretically predicted but experimentally elusive contribution of surface piezoelectricity to macroscopic bending-induced polarization.
Yanzheng Wang - One of the best experts on this subject based on the ideXlab platform.
-
reflection of ultrasound from a region of Cubic Material nonlinearity due to harmonic generation
Acta Mechanica, 2018Co-Authors: Yanzheng Wang, Jan Drewes AchenbachAbstract:Two models are proposed to obtain information on the Material nonlinearity of an inclusion in a solid body. Material nonlinearity is usually generated by the development of Material microscale damage. When the region of nonlinear Material is large, incidence of ultrasound on the interface between the perfectly joined regions of linear and nonlinear Material behavior produces very useful information. Using the continuity condition of stress and displacement at the interface, the harmonics in the nonlinear region, together with the compensatory waves, yield a reflected wave whose amplitude contains the defining constant of the Material nonlinearity near the interface. The compensatory waves are introduced to ensure the continuity conditions at the interface. When the nonlinear region is an inclusion, the equivalent body force induced by the Material nonlinearity generates a backscattered wave. The backscattered wave is determined in a simple manner by the use of the reciprocity theorem of elastodynamics. The backscattered wave obtained in this manner yields information on the nonlinear Material properties and the size of the inclusion. In addition, a model based on the superposition of back-propagated compensatory waves from the two interfaces of the nonlinear region reveals the physical mechanism of wave scattering from the nonlinear inclusion.
-
the effect of Cubic Material nonlinearity on the propagation of torsional wave modes in a pipe
Journal of the Acoustical Society of America, 2016Co-Authors: Yanzheng Wang, Jan Drewes AchenbachAbstract:The effect of Cubic Material nonlinearity on the propagation in a pipe of the lowest axially symmetric torsional wave mode has been investigated in this paper. Two cases, one that the Material of the whole pipe is nonlinear, and the second that a small segment of the pipe is nonlinear, have been considered. For the first case, a first and a third harmonic have been obtained by the perturbation method. Analytical expressions for the two cumulative harmonics have been derived. The second case leads to a scattering problem. The segment produces nonlinear terms in the equation of motion, which can be regarded as a distribution of body forces. The problem is then reduced to a linear scattering problem. An analytical expression for the backscattered wave can be easily obtained by using the elastodynamic reciprocity theorem. Due to the low amplitude of the backscattered wave, the authors propose to add another higher frequency wave to the primary wave, to increase the total magnitude of the scattered wave. An example that the originally scattered wave is amplified 50 times by selecting proper frequencies is presented. Both cases considered here have a potential application to determine the Material properties in a region of nonlinear Material behavior.The effect of Cubic Material nonlinearity on the propagation in a pipe of the lowest axially symmetric torsional wave mode has been investigated in this paper. Two cases, one that the Material of the whole pipe is nonlinear, and the second that a small segment of the pipe is nonlinear, have been considered. For the first case, a first and a third harmonic have been obtained by the perturbation method. Analytical expressions for the two cumulative harmonics have been derived. The second case leads to a scattering problem. The segment produces nonlinear terms in the equation of motion, which can be regarded as a distribution of body forces. The problem is then reduced to a linear scattering problem. An analytical expression for the backscattered wave can be easily obtained by using the elastodynamic reciprocity theorem. Due to the low amplitude of the backscattered wave, the authors propose to add another higher frequency wave to the primary wave, to increase the total magnitude of the scattered wave. An ex...
-
the effect of Cubic Material nonlinearity on the propagation of torsional wave modes in a pipe
Journal of the Acoustical Society of America, 2016Co-Authors: Yanzheng Wang, J D AchenbachAbstract:The effect of Cubic Material nonlinearity on the propagation in a pipe of the lowest axially symmetric torsional wave mode has been investigated in this paper. Two cases, one that the Material of the whole pipe is nonlinear, and the second that a small segment of the pipe is nonlinear, have been considered. For the first case, a first and a third harmonic have been obtained by the perturbation method. Analytical expressions for the two cumulative harmonics have been derived. The second case leads to a scattering problem. The segment produces nonlinear terms in the equation of motion, which can be regarded as a distribution of body forces. The problem is then reduced to a linear scattering problem. An analytical expression for the backscattered wave can be easily obtained by using the elastodynamic reciprocity theorem. Due to the low amplitude of the backscattered wave, the authors propose to add another higher frequency wave to the primary wave, to increase the total magnitude of the scattered wave. An example that the originally scattered wave is amplified 50 times by selecting proper frequencies is presented. Both cases considered here have a potential application to determine the Material properties in a region of nonlinear Material behavior.
Jackeline Narvaez - One of the best experts on this subject based on the ideXlab platform.
-
large flexoelectric anisotropy in paraelectric barium titanate
Physical Review Letters, 2015Co-Authors: Jackeline Narvaez, Sahar Saremi, Jiawang Hong, Massimiliano Stengel, Gustau CatalanAbstract:The bending-induced polarization of barium titanate single crystals has been measured with an aim to elucidate the origin of the large difference between theoretically predicted and experimentally measured flexoelectricity in this Material. The results indicate that part of the difference is due to polar regions (short-range order) that exist above T(C) and up to T*≈200-225 °C. Above T*, however, the flexovoltage coefficient still shows an unexpectedly large anisotropy for a Cubic Material, with (001)-oriented crystals displaying 10 times more flexoelectricity than (111)-oriented crystals. Theoretical analysis shows that this anisotropy cannot be a bulk property, and we therefore interpret it as indirect evidence for the theoretically predicted but experimentally elusive contribution of surface piezoelectricity to macroscopic bending-induced polarization.
Jan Drewes Achenbach - One of the best experts on this subject based on the ideXlab platform.
-
reflection of ultrasound from a region of Cubic Material nonlinearity due to harmonic generation
Acta Mechanica, 2018Co-Authors: Yanzheng Wang, Jan Drewes AchenbachAbstract:Two models are proposed to obtain information on the Material nonlinearity of an inclusion in a solid body. Material nonlinearity is usually generated by the development of Material microscale damage. When the region of nonlinear Material is large, incidence of ultrasound on the interface between the perfectly joined regions of linear and nonlinear Material behavior produces very useful information. Using the continuity condition of stress and displacement at the interface, the harmonics in the nonlinear region, together with the compensatory waves, yield a reflected wave whose amplitude contains the defining constant of the Material nonlinearity near the interface. The compensatory waves are introduced to ensure the continuity conditions at the interface. When the nonlinear region is an inclusion, the equivalent body force induced by the Material nonlinearity generates a backscattered wave. The backscattered wave is determined in a simple manner by the use of the reciprocity theorem of elastodynamics. The backscattered wave obtained in this manner yields information on the nonlinear Material properties and the size of the inclusion. In addition, a model based on the superposition of back-propagated compensatory waves from the two interfaces of the nonlinear region reveals the physical mechanism of wave scattering from the nonlinear inclusion.
-
the effect of Cubic Material nonlinearity on the propagation of torsional wave modes in a pipe
Journal of the Acoustical Society of America, 2016Co-Authors: Yanzheng Wang, Jan Drewes AchenbachAbstract:The effect of Cubic Material nonlinearity on the propagation in a pipe of the lowest axially symmetric torsional wave mode has been investigated in this paper. Two cases, one that the Material of the whole pipe is nonlinear, and the second that a small segment of the pipe is nonlinear, have been considered. For the first case, a first and a third harmonic have been obtained by the perturbation method. Analytical expressions for the two cumulative harmonics have been derived. The second case leads to a scattering problem. The segment produces nonlinear terms in the equation of motion, which can be regarded as a distribution of body forces. The problem is then reduced to a linear scattering problem. An analytical expression for the backscattered wave can be easily obtained by using the elastodynamic reciprocity theorem. Due to the low amplitude of the backscattered wave, the authors propose to add another higher frequency wave to the primary wave, to increase the total magnitude of the scattered wave. An example that the originally scattered wave is amplified 50 times by selecting proper frequencies is presented. Both cases considered here have a potential application to determine the Material properties in a region of nonlinear Material behavior.The effect of Cubic Material nonlinearity on the propagation in a pipe of the lowest axially symmetric torsional wave mode has been investigated in this paper. Two cases, one that the Material of the whole pipe is nonlinear, and the second that a small segment of the pipe is nonlinear, have been considered. For the first case, a first and a third harmonic have been obtained by the perturbation method. Analytical expressions for the two cumulative harmonics have been derived. The second case leads to a scattering problem. The segment produces nonlinear terms in the equation of motion, which can be regarded as a distribution of body forces. The problem is then reduced to a linear scattering problem. An analytical expression for the backscattered wave can be easily obtained by using the elastodynamic reciprocity theorem. Due to the low amplitude of the backscattered wave, the authors propose to add another higher frequency wave to the primary wave, to increase the total magnitude of the scattered wave. An ex...
Janusz Nowotny - One of the best experts on this subject based on the ideXlab platform.
-
effect of particle size on the room temperature crystal structure of barium titanate
Journal of the American Ceramic Society, 1994Co-Authors: B D Begg, E R Vance, Janusz NowotnyAbstract:The room-temperature tetragonal-to-Cubic transformation in BaTiO3 powders with decreasing particle size has been carefully studied, using Materials prepared mainly by hydrothermal methods. Hydrothermal BaTiO3 powders exhibited a more uniform particle size distribution than oxalate-route powders, with X-ray diffraction and electron microscopy indicating that powders 0.19 μm in size were fully Cubic while powders 0.27 μ were completely tetragonal (within a 5% detection limit for Cubic Material) at room temperature. The tetragonal-to-Cubic transformation temperature was also found to lie in the range of 121°± 3°C for BaTiO3 powders with room-temperature (c/a) values > 1.008. No transformation could be detected using differential scanning calorimetry for BaTiO3 particles with a (c/a) > 1.008 at room temperature. BaTiO3 powder with a particle size just too small (0.19 μm) to be tetragonal at room temperature remained Cubic down to 80 K. Different models for the Cubic-to-tetragonal room-temperature transformation are discussed. Hydroxyl ions do not appear to greatly affect the Cubic-to-tetragonal transformation, which appears to be essentially dependent on particle size. It is concluded that a model based on surface free energy, as previously discussed for the monoclinic-to-tetragonal transformation at room temperature of fine ZrO2 particles, is consistent with the experimental data.