The Experts below are selected from a list of 39924 Experts worldwide ranked by ideXlab platform
Th Jeggy - One of the best experts on this subject based on the ideXlab platform.
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influence of transverse cracking on ply behavior introduction of a characteristic Damage Variable
Composites Science and Technology, 1993Co-Authors: Jacques Renard, J P Favre, Th JeggyAbstract:Abstract The most critical types of Damage in composite materials are transverse cracking, delamination and fiber breakage. We have studied transverse cracking in a specimen submitted to axial and shear loading. The proposed model, based on Damage mechanics, analyses the consequences of this degradation by a decrease of the anisotropic stiffnesses of the Damaged layers of a composite structure. A Damage Variable is introduced to formulate a Damage onset criterion and a Damage development law. The development of cracks is simulated by a homogenization method and a macroscopic continuum Damage mechanics (CDM) approach. The influence of the orientation of adjacent plies, the thickness and the position of the cracked ply in the stacking sequence have been studied. An iterative process is used to introduce the non-linearity of this Damage development in a finite element program. The results obtained for beams submitted to axial loading are compared with experimental curves. Some practical applications are presented for laminated plates containing an open hole subjected to axial and biaxial loading.
Peter I. Kattan - One of the best experts on this subject based on the ideXlab platform.
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On the decomposition of the Damage Variable in continuum Damage mechanics
Acta Mechanica, 2017Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:Refinements and generalizations of the decomposition of the Damage Variable are presented within the framework of continuum Damage mechanics. It is assumed that Damage in a solid is due mainly to cracks and voids. The classical decomposition of the Damage Variable into a Damage part due to cracks and another Damage part due to voids is examined and extended consistently and mathematically. This is further elaborated upon by considering a solid with three types of defects: cracks, voids, and a third defect that is unspecified. Initially, the decomposition issues are carried out in one dimension using scalars. But this is generalized subsequently for the general case of three-dimensional deformation and Damage using tensors. Finally, the special case of plane stress is illustrated as an example. It is shown that in the case of plane stress, two explicit decomposition equations are obtained along with a third implicit coupling equation that relates the various “crack” and “void” Damage tensor components.
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Linearized Damage mechanics for states of small Damage
Acta Mechanica, 2015Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:In this work, the concept of a linearized Damage Variable is introduced within the framework of continuum Damage mechanics. Instead of considering one single fictitious unDamaged configuration, a number n of smaller fictitious unDamaged configurations are utilized. Thus, a smaller and linearized Damage Variable can be defined for each individual fictitious unDamaged configuration. Additionally, the equations of Damage evolution are formulated with respect to each individual fictitious unDamaged configuration. Some interesting and surprising results are obtained. In this regard, a new result is obtained for the strain energies with respect to the n fictitious unDamaged configurations. The linearized Damage Variable can be used for states of Damage where the Damage is small. The formulation is linear elastic based on linear superposition and should be applicable to many high-cycle fatigue problems.
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Investigation of the Damage Variable basic issues in continuum Damage and healing mechanics
Mechanics Research Communications, 2015Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:Abstract Consistent mathematics and mechanics are used here to properly interpret the Damage Variable within the confines of the concept of reduced area due to Damage. In this work basic issues are investigated for the Damage Variable in conjunction with continuum Damage and healing mechanics. First, the issue of the additive decomposition of the Damage Variable into Damage due to voids and Damage due to cracks in continuum Damage mechanics is discussed. The accurate decomposition is shown to be non-additive and involves a term due to the interaction of cracks and voids. It is shown also that the additive decomposition can only be used for the special case of small Damage. Furthermore, a new decomposition is derived for the evolution of the Damage Variable. The second issue to be discussed is the new concept of independent and dependent Damage processes. For this purpose, exact expressions for the two types of Damage processes are presented. The third issue addressed is the concept of healing processes occurring in series and in parallel. In this regard, systematically and consistently, the equations of healing processes occurring either consecutively or simultaneously are discussed. This is followed by introducing the new concept of small healing in Damaged materials. Simplified equations that apply when healing effects are small are shown. Finally, some interesting and special Damage processes using a systematic and original formulation are presented.
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Damage Mechanics in a Uniaxially - Loaded Elastic Tapered Bar
Jordan Journal of Civil Engineering, 2014Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:The principles of Damage mechanics are used to predict the displacements and stresses in a uniaxially-loaded one-dimensional elastic tapered bar. The variation of the Damage Variable along the length of the bar is studied. A random distribution of the Damage Variable along the length of the bar is also considered. It is shown how the displacements and stresses are obtained in closed-form solutions whenever possible. Otherwise, finite element analysis is employed to solve the resulting problem. The computer algebra system MAPLE is used to write a symbolic finite element program specifically for this problem with the random distribution of the Damage Variable for which there is no closed form solution.
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Mechanics of small Damage in fiber-reinforced composite materials
Composite Structures, 2010Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:Abstract In this work the new concept of small Damage is examined within the framework of continuum Damage mechanics. In particular, special emphasis is given to a new Damage Variable that is defined in terms of the elastic stiffness of the material. Only the scalar case is studied in this work. The scalar definition of the new Damage Variable was used recently by many researchers. The investigation of the new scalar Damage Variable and the new concept of small Damage is carried out on fiber-reinforced composite materials. Furthermore, the two approaches to Damage analysis in composite materials are re-examined in this work using the new Damage Variable. These are the well known overall and local approaches established in the literature of Damage mechanics. It is noted that the examination of these two approaches that is presented here applies to both small and large Damage mechanics. Finally, the two approaches are compared mathematically and are shown to be equivalent.
H J Chen - One of the best experts on this subject based on the ideXlab platform.
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effects of high temperatures and loading rates on the splitting tensile strength of jointed rock mass
Geotechnical and Geological Engineering, 2020Co-Authors: L X Xiong, H J ChenAbstract:The splitting tensile tests on the artificial jointed rock mass specimens were carried out using cylindrical samples after being exposed to high temperatures. The effects of the dip angle of joint plane, the radial elastic modulus, the radial peak strain, the Damage Variable D, the loading rate and the high temperature on the tensile strength of the jointed rock mass were investigated. Test results show that: (1) when the past-exposed high temperature is the same and the dip angle β (the angle between the joint plane and the horizontal plane) of joint plane increases from 0° to 90°, both the tensile strength and the radial elastic modulus first decrease and then increase. However, the Damage Variable D increases with the dip angle β rising from 0° to 60°, and decreases with the dip angle β elevating from 60° to 90°. (2) When both the dip angle β and the loading rate are the same, as the exposed high temperature increases from room temperature 25 to 400 °C, the tensile strength, the radial elastic modulus decreases and the radial peak strain all gradually decrease, whereas the Damage Variable D increases gradually. (3) When both the dip angle β and the past-exposed temperature are the same, as the loading rate increases from 0.05 to 5.0 mm/min, the tensile strength and the radial elastic modulus both increase gradually, whereas the Damage Variable D decreases gradually.
Jacques Renard - One of the best experts on this subject based on the ideXlab platform.
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influence of transverse cracking on ply behavior introduction of a characteristic Damage Variable
Composites Science and Technology, 1993Co-Authors: Jacques Renard, J P Favre, Th JeggyAbstract:Abstract The most critical types of Damage in composite materials are transverse cracking, delamination and fiber breakage. We have studied transverse cracking in a specimen submitted to axial and shear loading. The proposed model, based on Damage mechanics, analyses the consequences of this degradation by a decrease of the anisotropic stiffnesses of the Damaged layers of a composite structure. A Damage Variable is introduced to formulate a Damage onset criterion and a Damage development law. The development of cracks is simulated by a homogenization method and a macroscopic continuum Damage mechanics (CDM) approach. The influence of the orientation of adjacent plies, the thickness and the position of the cracked ply in the stacking sequence have been studied. An iterative process is used to introduce the non-linearity of this Damage development in a finite element program. The results obtained for beams submitted to axial loading are compared with experimental curves. Some practical applications are presented for laminated plates containing an open hole subjected to axial and biaxial loading.
George Z. Voyiadjis - One of the best experts on this subject based on the ideXlab platform.
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On the decomposition of the Damage Variable in continuum Damage mechanics
Acta Mechanica, 2017Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:Refinements and generalizations of the decomposition of the Damage Variable are presented within the framework of continuum Damage mechanics. It is assumed that Damage in a solid is due mainly to cracks and voids. The classical decomposition of the Damage Variable into a Damage part due to cracks and another Damage part due to voids is examined and extended consistently and mathematically. This is further elaborated upon by considering a solid with three types of defects: cracks, voids, and a third defect that is unspecified. Initially, the decomposition issues are carried out in one dimension using scalars. But this is generalized subsequently for the general case of three-dimensional deformation and Damage using tensors. Finally, the special case of plane stress is illustrated as an example. It is shown that in the case of plane stress, two explicit decomposition equations are obtained along with a third implicit coupling equation that relates the various “crack” and “void” Damage tensor components.
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Linearized Damage mechanics for states of small Damage
Acta Mechanica, 2015Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:In this work, the concept of a linearized Damage Variable is introduced within the framework of continuum Damage mechanics. Instead of considering one single fictitious unDamaged configuration, a number n of smaller fictitious unDamaged configurations are utilized. Thus, a smaller and linearized Damage Variable can be defined for each individual fictitious unDamaged configuration. Additionally, the equations of Damage evolution are formulated with respect to each individual fictitious unDamaged configuration. Some interesting and surprising results are obtained. In this regard, a new result is obtained for the strain energies with respect to the n fictitious unDamaged configurations. The linearized Damage Variable can be used for states of Damage where the Damage is small. The formulation is linear elastic based on linear superposition and should be applicable to many high-cycle fatigue problems.
-
Investigation of the Damage Variable basic issues in continuum Damage and healing mechanics
Mechanics Research Communications, 2015Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:Abstract Consistent mathematics and mechanics are used here to properly interpret the Damage Variable within the confines of the concept of reduced area due to Damage. In this work basic issues are investigated for the Damage Variable in conjunction with continuum Damage and healing mechanics. First, the issue of the additive decomposition of the Damage Variable into Damage due to voids and Damage due to cracks in continuum Damage mechanics is discussed. The accurate decomposition is shown to be non-additive and involves a term due to the interaction of cracks and voids. It is shown also that the additive decomposition can only be used for the special case of small Damage. Furthermore, a new decomposition is derived for the evolution of the Damage Variable. The second issue to be discussed is the new concept of independent and dependent Damage processes. For this purpose, exact expressions for the two types of Damage processes are presented. The third issue addressed is the concept of healing processes occurring in series and in parallel. In this regard, systematically and consistently, the equations of healing processes occurring either consecutively or simultaneously are discussed. This is followed by introducing the new concept of small healing in Damaged materials. Simplified equations that apply when healing effects are small are shown. Finally, some interesting and special Damage processes using a systematic and original formulation are presented.
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Damage Mechanics in a Uniaxially - Loaded Elastic Tapered Bar
Jordan Journal of Civil Engineering, 2014Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:The principles of Damage mechanics are used to predict the displacements and stresses in a uniaxially-loaded one-dimensional elastic tapered bar. The variation of the Damage Variable along the length of the bar is studied. A random distribution of the Damage Variable along the length of the bar is also considered. It is shown how the displacements and stresses are obtained in closed-form solutions whenever possible. Otherwise, finite element analysis is employed to solve the resulting problem. The computer algebra system MAPLE is used to write a symbolic finite element program specifically for this problem with the random distribution of the Damage Variable for which there is no closed form solution.
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Mechanics of small Damage in fiber-reinforced composite materials
Composite Structures, 2010Co-Authors: George Z. Voyiadjis, Peter I. KattanAbstract:Abstract In this work the new concept of small Damage is examined within the framework of continuum Damage mechanics. In particular, special emphasis is given to a new Damage Variable that is defined in terms of the elastic stiffness of the material. Only the scalar case is studied in this work. The scalar definition of the new Damage Variable was used recently by many researchers. The investigation of the new scalar Damage Variable and the new concept of small Damage is carried out on fiber-reinforced composite materials. Furthermore, the two approaches to Damage analysis in composite materials are re-examined in this work using the new Damage Variable. These are the well known overall and local approaches established in the literature of Damage mechanics. It is noted that the examination of these two approaches that is presented here applies to both small and large Damage mechanics. Finally, the two approaches are compared mathematically and are shown to be equivalent.
