The Experts below are selected from a list of 3498 Experts worldwide ranked by ideXlab platform
James F Stubbins - One of the best experts on this subject based on the ideXlab platform.
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stress induced amorphization at Moving Crack tips in niti
Applied Physics Letters, 1998Co-Authors: P R Okamoto, J K Heuer, Yasuhiro Matsukawa, Kaeko Tozawa, Somei Ohnuki, James F StubbinsAbstract:In situ fracture studies have been carried out on thin films of the NiTi intermetallic compound under plane stress, tensile loading conditions in the high-voltage electron microscope. Local stress-induced amorphization of regions directly in front of Moving Crack tips has been observed. The upper cutoff temperature, TC–Amax, for the stress-induced crystalline-to-amorphous transformation was found to be 600 K, identical to that for heavy ion-induced amorphization of NiTi and for ion-beam mixing-induced amorphization of Ni and Ti multilayer specimens. 600 K is also both the lower cutoff temperature, TA–Cmin, for radiation-induced crystallization of initially-unrelaxed amorphous NiTi and the lowest isothermal annealing temperature, TXmin, at which stress-induced amorphous NiTi crystallizes. Since TXmin should be TK, the ideal glass transition temperature, the discovery that TC–Amax=TA–Cmin=TXmin=TK implies that disorder-driven crystalline-to-amorphous transformations result in the formation of the ideal glas...
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stress induced amorphization at Moving Crack tips in niti
Fall Meeting of the Materials Research Society Boston MA (US) 12 05 1997--12 05 1997, 1998Co-Authors: P R Okamoto, J K Heuer, Yasuhiro Matsukawa, Kaeko Tozawa, Somei Ohnuki, James F StubbinsAbstract:In situ fracture studies on thin-film NiTi intermetallic compounds have been carried out in the high-voltage electron microscope at Argonne National Laboratory. Local stress-induced amorphization of regions directly in front of Moving Crack tips has been observed under tensile loading conditions. The stress-induced amorphization at Crack tips exhibits a temperature dependence similar to that of ion-induced amorphization of NiTi. The upper limiting temperature for stress-induced amorphization is the same as that for ion-induced amorphization of crystalline NiTi and for amorphous phase formation during ion-beam mixing of Ni and Ti multilayer specimens. This upper limiting temperature of 600K is also the lowest temperature at which stress-induced amorphous phase crystallizes during isothermal annealing. This isothermal crystallization temperature is nearly 200K less than the kinetic crystallization temperature during heating of unrelaxed NiTi glasses formed by rapid quenching or vapor phase deposition.
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In Situ Examination of Moving Crack Tips in Ordered Intermetallics
MRS Proceedings, 1998Co-Authors: J K Heuer, P R Okamoto, Nghi Q. Lam, James F StubbinsAbstract:Recent studies have shown that high stress concentrations at Moving Crack tips in the intermetallic compound NiTi can induce a crystalline-to-amorphous (C-A) transformation of the Crack tip region. This stress-induced C-A transformation has a temperature dependence and crystallization behavior similar to those of ion irradiation-induced C-A transformation of NiTi. The present study examines if these similarities between stress- and irradiation-induced amorphization hold true for two other intermetallic compounds, CuTi and Ni{sub 3}Ti. In situ straining was performed in an intermediate-voltage transmission electron microscope. The presence or absence of an amorphous phase was determined by dark field imaging and selected area diffraction of Crack tip regions. Crack tips in both CuTi and Ni{sub 3}Ti were found to remain crystalline upon fracture. The observed absence of stress-induced amorphization in Ni{sub 3}Ti is consistent with its known absence during irradiation, but the absence in CuTi differs from its known irradiation-induced amorphization behavior. Reasons for the similarity and difference are discussed.
Jay Fineberg - One of the best experts on this subject based on the ideXlab platform.
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Acquisition of inertia by a Moving Crack.
Physical review letters, 2010Co-Authors: Tamar Goldman, Ariel Livne, Jay FinebergAbstract:We experimentally investigate the dynamics of "simple" tensile Cracks. Within an effectively infinite medium, a Crack's dynamics perfectly correspond to inertialess behavior predicted by linear elastic fracture mechanics. Once a Crack interacts with waves that it generated at earlier times, this description breaks down. Cracks then acquire inertia and sluggishly accelerate. Crack inertia increases with Crack speed v and diverges as v approaches its limiting value. We show that these dynamics are in excellent accord with an equation of motion derived in the limit of an infinite strip [M. Marder, Phys. Rev. Lett. 66, 2484 (1991)].
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Crack front waves and the dynamics of a rapidly Moving Crack
Physical Review Letters, 2002Co-Authors: Eran Sharon, Gil Cohen, Jay FinebergAbstract:Dynamic fracture is of fundamental and practical importance. We consider the behavior of a Crack interacting with a localized defect. We show that this interaction can induce fundamental changes to a Crack’s long-term dynamics. These changes imply that a necessarily 3D view of fracture must replace the basically 2D theory that is currently used to describe fracture in ideal materials. In ideal (defect-free), brittle amorphous materials, experiments [1‐3] indicate that until a Crack bifurcates, its dynamic behavior is in excellent agreement with an equation of motion [4,5] based on a linear elastic description of a Moving Crack in a 2D material. Balancing the energy flux, G, per unit length of the Crack with the fracture energy, G, defined as the energy needed to create a length of new fracture surface yields
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Crack front waves and the dynamics of a rapidly Moving Crack
Physical Review Letters, 2002Co-Authors: Eran Sharon, Gil Cohen, Jay FinebergAbstract:Crack front waves are nonlinear localized waves that propagate along the leading edge of a Crack. They are generated by both the interaction of a Crack with a localized material inhomogeneity and the intrinsic formation of microbranches. Front waves are shown to transport energy, generate surface structure, and lead to localized velocity fluctuations. Their existence locally imparts inertia, which is not incorporated in current theories of fracture, to initially "massless" Cracks. This, coupled to microbranch formation, yields both inhomogeneity and scaling behavior within the fracture surface structure.
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Propagating solitary waves along a rapidly Moving Crack front
Nature, 2001Co-Authors: Eran Sharon, Gil Cohen, Jay FinebergAbstract:A rapidly Moving Crack in a brittle material is often idealized^ 1 as a one-dimensional object with a singular tip, Moving through a two-dimensional material. However, in real three-dimensional materials, tensile Cracks form a planar surface whose edge is a rapidly Moving one-dimensional singular front. The dynamics of these fronts under repetitive interaction^ 2 , 3 , 4 with material inhomogeneities (asperities) and the morphology^ 5 , 6 , 7 , 8 , 9 , 10 , 11 of the fracture surface that they create are not yet understood. Here we show that perturbations^ 12 to a Crack front in a brittle material result in long-lived and highly localized waves, which we call ‘front waves’. These waves exhibit a unique characteristic shape and propagate along the Crack front at approximately^ 13 , 14 , 15 the Rayleigh wave speed (the speed of sound along a free surface). Following interaction, counter-propagating front waves retain both their shape and amplitude. They create characteristic traces along the fracture surface, providing Cracks with both inertia and a new mode of dissipation. Front waves are intrinsically three-dimensional, and cannot exist in conventional two-dimensional theories of fracture^ 1 . Because front waves can transport and distribute asperity-induced energy fluctuations throughout the Crack front, they may help to explain how Cracks remain a single coherent entity, despite repeated interactions with randomly dispersed asperities.
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Acoustic emissions from rapidly Moving Cracks.
Physical review letters, 1993Co-Authors: Steven P. Gross, Jay Fineberg, Michael P Marder, William D. Mccormick, Harry L. SwinneyAbstract:Linear elasticity is unable to predict completely the dynamics of a rapidly Moving Crack without the addition of a phenomenological fracture energy. Our measurements of acoustic emission, Crack velocity, and surface structure demonstrate quantitatively similar dynamical fracture behavior in two very different materials, polymethylmethacrylate and soda-lime glass. This unexpected agreement suggests that there exist universal features of the fracture energy that result from dissipation of energy in a dynamical instability.
Lu-qiao Qi - One of the best experts on this subject based on the ideXlab platform.
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effect of maxwell stress on a Moving Crack with polarization saturation region in ferroelectric solid
Meccanica, 2018Co-Authors: Lu-qiao QiAbstract:The focus of this work is on a generalized two-dimensional problem of a Crack Moving in a piezoelectric solid subjected to uniform electrical load at infinity. The novel point includes that the electric field inside the Crack is taken into account when polarization saturation region exists. Based on the extended Stroh formalism and complex function method, explicit expressions of both the stress fields in the solid and electric fields inside the Crack are derived by using semi-permeable Crack model, respectively. Effect of Maxwell stress along the Crack surface is investigated and the results are illustrated graphically. It is shown that the Moving speed of the Crack cannot exceed the lowest bulk wave speed. It is also found that the medium properties inside the Crack and surrounding the ferroelectric solid at infinity directly affect the Maxwell stress, and as a result the Maxwell stresses are remarkable and cannot be ignored under different electric load.
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effect of maxwell stress on a Moving Crack with polarization saturation region in ferroelectric solid
Meccanica, 2018Co-Authors: Lu-qiao QiAbstract:The focus of this work is on a generalized two-dimensional problem of a Crack Moving in a piezoelectric solid subjected to uniform electrical load at infinity. The novel point includes that the electric field inside the Crack is taken into account when polarization saturation region exists. Based on the extended Stroh formalism and complex function method, explicit expressions of both the stress fields in the solid and electric fields inside the Crack are derived by using semi-permeable Crack model, respectively. Effect of Maxwell stress along the Crack surface is investigated and the results are illustrated graphically. It is shown that the Moving speed of the Crack cannot exceed the lowest bulk wave speed. It is also found that the medium properties inside the Crack and surrounding the ferroelectric solid at infinity directly affect the Maxwell stress, and as a result the Maxwell stresses are remarkable and cannot be ignored under different electric load.
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The influence of Maxwell stresses on a Moving Crack in piezoelectric materials
2016 Symposium on Piezoelectricity Acoustic Waves and Device Applications (SPAWDA), 2016Co-Authors: Lu-qiao Qi, Yu-hao LiAbstract:A plane problem of a Moving Crack with constant velocity in piezoelectric materials is investigated systematically. Based on the extended Stroh formalism, the closed-form expression of electric displacement in the Moving Crack, the electrostatic fields and dynamic stress and dynamic electric intensity factors are obtained in a concise form. The influence of Maxwell stresses and the speed of the Crack is studied when the model bears combined mechanical and electrical loads at infinity. The electrically semi-permeable Crack boundary condition is adopted. The effects of mediums inside the Crack and surrounding the matrix at infinity are also analyzed theoretically. Numerical results are presented and it is found that the dynamic intensity factors are related not only to the electric field, but also to the velocity of the Moving Crack.
Peter Streitenberger - One of the best experts on this subject based on the ideXlab platform.
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The Migration of Solute Atoms in the Stress Field of a Slowly Moving Crack
Materials Science Forum, 2005Co-Authors: Peter StreitenbergerAbstract:The stress-driven diffusion of solute atoms to a slowly Moving brittle Crack is studied under the condition of pure drift. The first-order drift-diffusion equation for a slowly Moving Crack at uniform velocity is solved yielding the flow lines and the impurity segregation rate in terms of the Crack growth rate. The flow line patterns reveal important insights with respect to the solute migration kinetics near a steadily advancing subcritical Crack at stage I and stage II Crack growth.
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The stress-driven diffusion of point defects to a slowly Moving Crack
Computational Materials Science, 2004Co-Authors: Peter StreitenbergerAbstract:The stress-driven diffusion of point defects to a slowly Moving brittle Crack is studied under the condition of pure drift. In the pure-drift approximation it is assumed that the point defect flow in the vicinity of a Crack tip is dominated by the elastic interaction between the stress field of the Crack and a point defect and that concentration gradient effects can be neglected. The first-order drift-diffusion equation for a slowly Moving Crack at uniform velocity is solved. This yields the flow lines of the point defects and the impurity segregation rate directly in terms of the Crack growth rate. The flow line patterns reveal important insights with respect to the point defect migration kinetics near a steadily advancing Crack.
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The stress-driven migration of point defects to a slowly Moving Crack
Philosophical Magazine, 2004Co-Authors: Peter StreitenbergerAbstract:The migration kinetics of point defects near a slowly Moving brittle Crack are studied under the condition of pure drift. In the pure-drift approximation it is assumed that the point-defect flow in the vicinity of a Crack tip is dominated by the elastic interaction between the stress field of the Crack and a point defect and that concentration gradient effects can be neglected. While such a pure-drift approach has been shown to be useful to calculate the short-time diffusion kinetics of impurity-induced subcritical Crack growth, previous applications are based on the drift solutions for a stationary Crack. In the present paper, the first-order drift diffusion equation for a slowly Moving Crack at uniform velocity is solved. This yields the flow lines of the point defects and the impurity segregation rate directly in terms of the Crack growth rate. The flow line patterns reveal important insights with respect to the point-defect migration kinetics near a steadily advancing Crack. Although the calculation i...
P R Okamoto - One of the best experts on this subject based on the ideXlab platform.
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stress induced amorphization at Moving Crack tips in niti
Applied Physics Letters, 1998Co-Authors: P R Okamoto, J K Heuer, Yasuhiro Matsukawa, Kaeko Tozawa, Somei Ohnuki, James F StubbinsAbstract:In situ fracture studies have been carried out on thin films of the NiTi intermetallic compound under plane stress, tensile loading conditions in the high-voltage electron microscope. Local stress-induced amorphization of regions directly in front of Moving Crack tips has been observed. The upper cutoff temperature, TC–Amax, for the stress-induced crystalline-to-amorphous transformation was found to be 600 K, identical to that for heavy ion-induced amorphization of NiTi and for ion-beam mixing-induced amorphization of Ni and Ti multilayer specimens. 600 K is also both the lower cutoff temperature, TA–Cmin, for radiation-induced crystallization of initially-unrelaxed amorphous NiTi and the lowest isothermal annealing temperature, TXmin, at which stress-induced amorphous NiTi crystallizes. Since TXmin should be TK, the ideal glass transition temperature, the discovery that TC–Amax=TA–Cmin=TXmin=TK implies that disorder-driven crystalline-to-amorphous transformations result in the formation of the ideal glas...
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stress induced amorphization at Moving Crack tips in niti
Fall Meeting of the Materials Research Society Boston MA (US) 12 05 1997--12 05 1997, 1998Co-Authors: P R Okamoto, J K Heuer, Yasuhiro Matsukawa, Kaeko Tozawa, Somei Ohnuki, James F StubbinsAbstract:In situ fracture studies on thin-film NiTi intermetallic compounds have been carried out in the high-voltage electron microscope at Argonne National Laboratory. Local stress-induced amorphization of regions directly in front of Moving Crack tips has been observed under tensile loading conditions. The stress-induced amorphization at Crack tips exhibits a temperature dependence similar to that of ion-induced amorphization of NiTi. The upper limiting temperature for stress-induced amorphization is the same as that for ion-induced amorphization of crystalline NiTi and for amorphous phase formation during ion-beam mixing of Ni and Ti multilayer specimens. This upper limiting temperature of 600K is also the lowest temperature at which stress-induced amorphous phase crystallizes during isothermal annealing. This isothermal crystallization temperature is nearly 200K less than the kinetic crystallization temperature during heating of unrelaxed NiTi glasses formed by rapid quenching or vapor phase deposition.
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In Situ Examination of Moving Crack Tips in Ordered Intermetallics
MRS Proceedings, 1998Co-Authors: J K Heuer, P R Okamoto, Nghi Q. Lam, James F StubbinsAbstract:Recent studies have shown that high stress concentrations at Moving Crack tips in the intermetallic compound NiTi can induce a crystalline-to-amorphous (C-A) transformation of the Crack tip region. This stress-induced C-A transformation has a temperature dependence and crystallization behavior similar to those of ion irradiation-induced C-A transformation of NiTi. The present study examines if these similarities between stress- and irradiation-induced amorphization hold true for two other intermetallic compounds, CuTi and Ni{sub 3}Ti. In situ straining was performed in an intermediate-voltage transmission electron microscope. The presence or absence of an amorphous phase was determined by dark field imaging and selected area diffraction of Crack tip regions. Crack tips in both CuTi and Ni{sub 3}Ti were found to remain crystalline upon fracture. The observed absence of stress-induced amorphization in Ni{sub 3}Ti is consistent with its known absence during irradiation, but the absence in CuTi differs from its known irradiation-induced amorphization behavior. Reasons for the similarity and difference are discussed.