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Kwang Ho Lee - One of the best experts on this subject based on the ideXlab platform.
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Analysis of a Propagating Crack tip in orthotropic functionally graded materials
Composites Part B: Engineering, 2016Co-Authors: Kwang Ho LeeAbstract:Abstract Crack tip stress and displacement fields for a Propagating Crack at constant velocity along a gradient in orthotropic functionally graded materials (OFGMs) with an exponential variation of the shear modulus and density are developed. The Crack tip fields are obtained by using wave potentials and the Airy stress function through an asymptotic analysis. Solutions are obtained for orthotropic characteristics of two kinds. Using the stress fields, the effects of material nonhomogeneity on the stress components are investigated. In addition, contours of the constant maximum shear stress at a Propagating Crack tip are generated and the effects of material nonhomogeneity on the isochromatics are discussed.
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Influence of density variation on the arbitrarily Propagating Crack tip fields in functionally graded materials
Journal of Mechanical Science and Technology, 2014Co-Authors: Kwang Ho LeeAbstract:The stress and displacement fields for an arbitrarily Propagating Crack tip in functionally graded materials (FGMs) with exponential variation of density and shear modulus are obtained. Nonhomogeneous parameters of density and shear modulus are different from each other. The solutions for higher order terms in the dynamic equilibriums are obtained by transforming the general differential equations to the scaled Laplace’s equations. Using the stress fields, the effects of the nonhomogeneous density on stress components is investigated. In addition, the contours of the constant maximum shear stress at a Propagating Crack tip are generated and the effects of the nonhomogeneous density on the isochromatics are discussed.
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Analysis of a transiently Propagating Crack in functionally graded materials under mode I and II
International Journal of Engineering Science, 2009Co-Authors: Kwang Ho LeeAbstract:Abstract Crack tip stress and displacement fields for a transiently Propagating Crack along gradient in functionally graded materials (FGMs) with a linear variation of shear modulus are developed. The higher order terms of the transient stress and displacement fields at Crack tip were obtained by transforming the general partial differential equations of the dynamic equilibrium into Laplace’s equations whose solutions have harmonic functions. Thus, the fields can be expressed very simply. Using these stress components, isochromatics and the first invariant at Crack tip are generated. The results show that the isochromatics (constant maximum shear stress) for mode I Crack tilt backward around the Crack tip with an increase of Crack tip acceleration c ˙ ( d c / d t ) , and tilt forward around the Crack tip with an increase of rate of change of dynamic mode I stress intensity factor K ˙ I ( d K I / d t ) . The isochromatics for mixed mode Crack move to upper direction with an increases of K ˙ I and K ˙ II , and lower direction with an increase of c ˙ . Contours of the first stress invariant for mode I Crack enlarge around the Crack tip with an increase of c ˙ , and decrease around the Crack tip with an increase of K ˙ I . As K ˙ I ( II ) decreases at Crack initiation, the predicted kinking angles increase. As c ˙ increases, the predicted kinking angles also increase.
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Characteristics of a transiently Propagating Crack in functionally graded materials
Journal of Mechanical Science and Technology, 2009Co-Authors: Kwang Ho Lee, Young J. Lee, Sang Bong ChoAbstract:When a Crack propagates with acceleration, deceleration and time rates of change of stress intensity factors, it is very important for us to understand the effects of acceleration, deceleration and time rates of change of stress intensity factors on the individual stresses and displacements at the Crack tip. Therefore, the Crack tip stress and displacement fields for a transiently Propagating Crack along gradient in functionally graded materials (FGMs) with an exponential variation of shear modulus and density are developed and the characteristics of a transiently Propagating Crack from the fields are analyzed. The effects of the rate of change of the stress intensity factor and the Crack tip acceleration on the individual stresses at the Crack tip are opposite each other. Specially, the isochromatics (constant maximum shear stress) of Mode I tilt backward around the Crack tip with an increase of Crack tip acceleration, and tilt forward around the Crack tip with an increase of the rate of change of the dynamic mode I stress intensity factor.
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Analysis of a Propagating Crack in functionally graded materials with property variation angled to Crack direction
Computational Materials Science, 2009Co-Authors: Kwang Ho LeeAbstract:Abstract The stress and displacement fields for a Crack Propagating in functionally graded materials (FGMs) with property variation angled to Crack direction are obtained. The FGMs have a linear variation of shear modulus with a constant density and Poisson’s ratio. The solutions for higher order terms in the dynamic equilibriums are obtained by transforming the general differential equations to Laplace’s equations. Using the stress fields, the effects of the nonhomogeneity and the angled properties on stress components are investigated. In addition to, the contours of the constant maximum shear stress around the static and Propagating Crack tip are generated. The contours of the constant maximum shear stress around the static and Propagating Crack tip tilt toward the property gradation direction.
Chukwuemeke William Isaac - One of the best experts on this subject based on the ideXlab platform.
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Crushing response of circular thin-walled tube with non-Propagating Crack subjected to dynamic oblique impact loading:
International Journal of Protective Structures, 2019Co-Authors: Chukwuemeke William IsaacAbstract:The dynamic oblique crushing of circular thin-walled tubes with the presence of non-Propagating Crack was investigated numerically. The material considered was strain rate sensitive with Crack loca...
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numerical modelling of the effect of non Propagating Crack in circular thin walled tubes under dynamic axial crushing
Thin-walled Structures, 2017Co-Authors: Chukwuemeke William Isaac, O O OluwoleAbstract:Abstract Circular thin-walled tubes have been adopted in vehicular structures to protect occupants and cargo in the events of crash. However, Crack initiation on the tubes may pose a great threat to limiting their crashworthiness performance such as the mean crushing force, energy absorption capacity, crush force efficiency and specific energy absorption. This study investigates numerically the dynamic axial crushing of a strain rate sensitive circular thin-walled tube material made from A36 steel hot rolled carbon and modeled with a Crack. Six different modeled tube geometries with non-Propagating Crack are studied and compared with the tube geometry without Crack. Results of the crashworthiness parameters, deformation modes, damage morphologies and force-displacement history were obtained. The finite element study shows and establishes the undesirable effect of Crack on the overall crashworthiness performance of circular thin-walled tubes.
Alexander L. Korzhenevskii - One of the best experts on this subject based on the ideXlab platform.
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Morphological transformation of the process zone at the tip of a Propagating Crack. I. Simulation.
Physical Review E, 2020Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:Stress concentration at a Crack tip engenders a process zone, a small domain containing a phase, different from that in the bulk of the solid. We demonstrate that this zone at the tip of a Propagating Crack exhibits a morphological transformation with an increase of the Crack velocity. The concave zone shape with an invagination in its back that is characteristic of a slow Crack transforms into a droplet-shaped convex zone upon exceeding a critical velocity value, ${v}_{\text{G}}$. In this latter case, a metastable wake follows the Propagating zone. We obtained this result by computer simulation of a Crack Propagating in a solid exhibiting a first-order phase transformation.
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Morphological transformation of the process zone at the tip of a Propagating Crack. II. Geometrical parameters of the process zone.
Physical Review E, 2020Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:The morphological transformation of the process zone at the tip of a Propagating Crack occurs with the increase of the Crack velocity. The zone configuration changes its shape from concave to convex, dropletlike form. The latter exhibits a metastable wake. We prove that the transformation takes place as soon as the Crack velocity exceeds Gordon's speed V_{G}. The latter is the velocity of motion of the interface between the stable and overheated metastable phases. We further analyze the dependence of geometrical parameters of the zone and wake on the Crack tip velocity. We show that at a constant velocity, the size of the process zone grows with the approach to the binodal. However, it decreases by over three orders of magnitude as the Crack's velocity increases. In contrast, the interval length where the zone or the wake comes in direct contact with the Crack surface increases at 0≤V
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morphological transformation of the process zone at the tip of a Propagating Crack ii geometrical parameters of the process zone
Physical Review E, 2020Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:The morphological transformation of the process zone at the tip of a Propagating Crack occurs with the increase of the Crack velocity. The zone configuration changes its shape from concave to convex, dropletlike form. The latter exhibits a metastable wake. We prove that the transformation takes place as soon as the Crack velocity exceeds Gordon's speed V_{G}. The latter is the velocity of motion of the interface between the stable and overheated metastable phases. We further analyze the dependence of geometrical parameters of the zone and wake on the Crack tip velocity. We show that at a constant velocity, the size of the process zone grows with the approach to the binodal. However, it decreases by over three orders of magnitude as the Crack's velocity increases. In contrast, the interval length where the zone or the wake comes in direct contact with the Crack surface increases at 0≤V
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Morphological transformation of the process zone at the tip of a Propagating Crack. I. Simulation.
Physical review. E, 2020Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:Stress concentration at a Crack tip engenders a process zone, a small domain containing a phase, different from that in the bulk of the solid. We demonstrate that this zone at the tip of a Propagating Crack exhibits a morphological transformation with an increase of the Crack velocity. The concave zone shape with an invagination in its back that is characteristic of a slow Crack transforms into a droplet-shaped convex zone upon exceeding a critical velocity value, v_{G}. In this latter case, a metastable wake follows the Propagating zone. We obtained this result by computer simulation of a Crack Propagating in a solid exhibiting a first-order phase transformation.
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Shape transformation of a wake following the process zone at the tip of a Propagating Crack
EPL (Europhysics Letters), 2018Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:A process zone containing a new phase often forms at the tip of a Crack in a quasi-brittle solid. We study such a zone engendered by the Propagating Crack. We show that depending on the Crack speed, V , this zone has two distinct configurations. If the Crack tip velocity is small, the zone takes a concave shape. As soon as V exceeds a critical value, , the zone becomes convex. A metastable remnant, the wake , forms in its rear part. It is stretched backward over a great distance and exhibits a triangle configuration with the vertex angle decreasing with speed. The morphological zone transition and the wake shape is explained by competition of the velocity of a free, plane phase front and the Crack tip speed.
Alexei Boulbitch - One of the best experts on this subject based on the ideXlab platform.
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Morphological transformation of the process zone at the tip of a Propagating Crack. I. Simulation.
Physical Review E, 2020Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:Stress concentration at a Crack tip engenders a process zone, a small domain containing a phase, different from that in the bulk of the solid. We demonstrate that this zone at the tip of a Propagating Crack exhibits a morphological transformation with an increase of the Crack velocity. The concave zone shape with an invagination in its back that is characteristic of a slow Crack transforms into a droplet-shaped convex zone upon exceeding a critical velocity value, ${v}_{\text{G}}$. In this latter case, a metastable wake follows the Propagating zone. We obtained this result by computer simulation of a Crack Propagating in a solid exhibiting a first-order phase transformation.
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Morphological transformation of the process zone at the tip of a Propagating Crack. II. Geometrical parameters of the process zone.
Physical Review E, 2020Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:The morphological transformation of the process zone at the tip of a Propagating Crack occurs with the increase of the Crack velocity. The zone configuration changes its shape from concave to convex, dropletlike form. The latter exhibits a metastable wake. We prove that the transformation takes place as soon as the Crack velocity exceeds Gordon's speed V_{G}. The latter is the velocity of motion of the interface between the stable and overheated metastable phases. We further analyze the dependence of geometrical parameters of the zone and wake on the Crack tip velocity. We show that at a constant velocity, the size of the process zone grows with the approach to the binodal. However, it decreases by over three orders of magnitude as the Crack's velocity increases. In contrast, the interval length where the zone or the wake comes in direct contact with the Crack surface increases at 0≤V
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morphological transformation of the process zone at the tip of a Propagating Crack ii geometrical parameters of the process zone
Physical Review E, 2020Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:The morphological transformation of the process zone at the tip of a Propagating Crack occurs with the increase of the Crack velocity. The zone configuration changes its shape from concave to convex, dropletlike form. The latter exhibits a metastable wake. We prove that the transformation takes place as soon as the Crack velocity exceeds Gordon's speed V_{G}. The latter is the velocity of motion of the interface between the stable and overheated metastable phases. We further analyze the dependence of geometrical parameters of the zone and wake on the Crack tip velocity. We show that at a constant velocity, the size of the process zone grows with the approach to the binodal. However, it decreases by over three orders of magnitude as the Crack's velocity increases. In contrast, the interval length where the zone or the wake comes in direct contact with the Crack surface increases at 0≤V
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Morphological transformation of the process zone at the tip of a Propagating Crack. I. Simulation.
Physical review. E, 2020Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:Stress concentration at a Crack tip engenders a process zone, a small domain containing a phase, different from that in the bulk of the solid. We demonstrate that this zone at the tip of a Propagating Crack exhibits a morphological transformation with an increase of the Crack velocity. The concave zone shape with an invagination in its back that is characteristic of a slow Crack transforms into a droplet-shaped convex zone upon exceeding a critical velocity value, v_{G}. In this latter case, a metastable wake follows the Propagating zone. We obtained this result by computer simulation of a Crack Propagating in a solid exhibiting a first-order phase transformation.
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Shape transformation of a wake following the process zone at the tip of a Propagating Crack
EPL (Europhysics Letters), 2018Co-Authors: Alexei Boulbitch, Alexander L. KorzhenevskiiAbstract:A process zone containing a new phase often forms at the tip of a Crack in a quasi-brittle solid. We study such a zone engendered by the Propagating Crack. We show that depending on the Crack speed, V , this zone has two distinct configurations. If the Crack tip velocity is small, the zone takes a concave shape. As soon as V exceeds a critical value, , the zone becomes convex. A metastable remnant, the wake , forms in its rear part. It is stretched backward over a great distance and exhibits a triangle configuration with the vertex angle decreasing with speed. The morphological zone transition and the wake shape is explained by competition of the velocity of a free, plane phase front and the Crack tip speed.
Zhen Qing Wang - One of the best experts on this subject based on the ideXlab platform.
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The Elastic-Viscoplastic Field Near Mode II Dynamic Propagating Crack-Tip of Interface in Double Dissimilar Materials
Advanced Materials Research, 2010Co-Authors: Wen Yan Liang, Zhen Qing WangAbstract:The existence of viscosity effect at the interface of double dissimilar materials has an important impact to the distribution of interface Crack-tip field and the properties variety of the interface itself. The singular is considered in Crack-tip, and the elastic-viscoplastic governing equations of double dissimilar materials at quasi-static Propagating interface Crack-tip field are established. The displacement potential function and boundary condition of interface Crack-tip are introduced, and the numerical analysis of rigid-elastic viscoplastic interface for mode II are worked out. The stress-strain fields are obtained at the Crack-tip and the variations of solutions are discussed according to each parameter. The numerical results show that the viscosity effect is a main factor of interface Propagating Crack-tip field, and the interface Crack-tip is a viscoplastic field that is governed by viscosity coefficient、Mach number and singular factor.
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The elastic-viscoplastic field near mode iii dynamic Propagating Crack-tip of interface in double dissimilar materials
2010 3rd International Symposium on Systems and Control in Aeronautics and Astronautics, 2010Co-Authors: Wen Yan Liang, Zhen Qing Wang, Pengcheng LinAbstract:The existence of viscosity effect at the interface of double dissimilar materials has an important impact to the distribution of interface Crack-tip field and the properties variety of the interface itself. The singular is considered in Crack-tip, and the elastic-viscoplastic quasi-static Propagating governing equations of double dissimilar materials at interface Crack-tip field are established. The displacement potential function and boundary condition of interface Crack-tip are introduced and the numerical analysis of rigid-elastic viscoplastic interface for mode III are worked out. The stress-strain fields are obtained at the Crack-tip and the variations of solutions are discussed according to each parameter. The numerical results show that the viscosity effect is a main factor of interface Propagating Crack-tip field, and the interface Crack-tip is a viscoplastic field that is governed by viscosity coefficient, Mach number and singular factor.
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Field Structure at Mode III Dynamically Propagating Crack Tip in elastic-viscoplastic Materials
Applied Mathematics and Mechanics-english Edition, 2008Co-Authors: Bin Jia, Zhen Qing WangAbstract:An elastic-viscoplastic mechanics model is used to investigate asymptotically the mode III dynamically Propagating Crack tip field in elastic-viscoplastic materials. The stress and strain fields at the Crack tip possess the same power-law singularity under a linear-hardening condition. The singularity exponent is uniquely determined by the viscosity coefficient of the material. Numerical results indicate that the motion parameter of the Crack Propagating speed has little effect on the zone structure at the Crack tip. The hardening coefficient dominates the structure of the Crack-tip field. However, the secondary plastic zone has little influence on the field. The viscosity of the material dominates the strength of stress and strain fields at the Crack tip while it does have certain influence on the Crack-tip field structure. The dynamic Crack-tip field degenerates into the relevant quasi-static solution when the Crack moving speed is zero. The corresponding perfectly-plastic solution is recovered from the linear-hardening solution when the hardening coefficient becomes zero.
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The Elastic-Viscoplastic Field at the Tip of Mode II Quasi-Static Propagating Crack in Rate-Sensitive Material
Key Engineering Materials, 2007Co-Authors: Wen Yan Liang, Zhen Qing Wang, Yong Jun WangAbstract:Under the assumption that the artificial viscosity coefficient at the Propagating Crack tip is in inverse proportion to power law of the plastic strain rate, a rate-sensitive constitutive relationship is derived for perfect elastic-plastic material. With the adoption of the rate-sensitive constitutive relationship, it is asymptotically investigated the Propagating tip fields of plane strain mode II. And the quasi-static equations are obtained separately governing the stress and strain fields at the Crack-tip by means of Airy stress function. Numerical calculations of governing equations are carried out by double parameters shooting, with selections of appropriate values of each characteristic parameter by combinations of boundary, and the fully continuous stress-strain fields are obtained at the Crack-tip. The analytical and computational results indicate that viscosity effect is an important factor in Crack-tip fields.
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The Asymptotic Elastic-Viscoplastic Field at Mode I Dynamic Propagating Crack-Tip
Key Engineering Materials, 2007Co-Authors: Zhen Qing Wang, Ji Bin Wang, Wen Yan LiangAbstract:The viscosity of material is considered at Propagating Crack-tip. Under the assumption that the artificial viscosity coefficient is in inverse proportion to the power law of the plastic strain rate, an elastic-viscoplastic asymptotic analysis is carried out for moving Crack-tip fields in power-hardening materials under plane-strain condition. A continuous solution is obtained containing no discontinuities. The variations of the numerical solution are discussed for mode I Crack according to each parameter. It is shown that stress and strain both possess exponential singularity. The elasticity, plasticity and viscosity of material at the Crack-tip only can be matched reasonably under linear-hardening condition. The tip field contains no elastic unloading zone for mode I Crack.
