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You searched for +publisher:"Texas A&M University" +contributor:("Darabi, Masoud"). Showing records 1 – 3 of 3 total matches.

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Texas A&M University

1. Arastoo, Mahsa. Modeling Micro-Damage Healing Mechanism at Micro-Scale.

Degree: 2013, Texas A&M University

This thesis demonstrates the effect of micro-damage healing on stress and displacement fields in the vicinity of a crack tip in the material that tend to self-heal. The micro-damage healing model is modeled by incorporating time-dependent traction within the crack faces. This time-dependent traction occurs in a small zone referred to as healing process zone. The effect of the micro-damage healing on crack propagation in elastic media is investigated by deriving analytical relations for Stress Intensity Factor (SIF) when micro-damage healing mechanism is in effect. It is shown that the larger values of both healing process zone and bonding strength decrease the value of SIF near the crack tip. In order to clearly capture this phenomenon, a novel technique based on complex variables is used to derive the equations to calculate the stress and displacement fields in elastic media. Using the third correspondence principle, which is suitable in analyzing the crack shortening (healing phenomenon), the corresponding results of stress and displacement fields in elastic media are converted into viscoelastic media. Since asphalt has time-dependent material properties, the viscoelastic result is more accurate than the elastic. It is shown that an increase in the value of both healing process zone and bonding strength results in a decrease in the stress and displacement fields near the crack tip. Finally, the effect of using different coefficients in defining the bonding strength and relaxation time is evaluated. Asphalt concrete pavements are concurrently subjected to mechanical and environmental loading conditions during their service life. Applied mechanical and environmental loadings gradually degrade properties of asphalt concrete pavements. However, under specific conditions, asphalt concrete has the potential to heal and regain part of its strength. Identifying a model for the healing process is crucial. This proposed model is not dependent on the test methods that empower its usage in computational modeling. Moreover, this research considers both effects of instantaneous healing (a result of wetting) and time-dependent bond strength (a result of molecular diffusion between the crack faces), using the complex-variable method. Schapery (1989) considered only instantaneous healing and regarded it as the total bond strength. Therefore, considering both effects of instantaneous and time-dependent bond-strength makes this model superior with respect to the analogous model. It is hoped that this research provides insight on the healing mechanism at micro-scale. Advisors/Committee Members: Little, Dallas N. (advisor), Hueste, Mary Beth (committee member), Boas, Harold P. (committee member), Karaman, Ibrahim (committee member), Darabi, Masoud (committee member).

Subjects/Keywords: Micro damage healing

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Arastoo, M. (2013). Modeling Micro-Damage Healing Mechanism at Micro-Scale. (Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/151281

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Arastoo, Mahsa. “Modeling Micro-Damage Healing Mechanism at Micro-Scale.” 2013. Thesis, Texas A&M University. Accessed May 27, 2019. http://hdl.handle.net/1969.1/151281.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Arastoo, Mahsa. “Modeling Micro-Damage Healing Mechanism at Micro-Scale.” 2013. Web. 27 May 2019.

Vancouver:

Arastoo M. Modeling Micro-Damage Healing Mechanism at Micro-Scale. [Internet] [Thesis]. Texas A&M University; 2013. [cited 2019 May 27]. Available from: http://hdl.handle.net/1969.1/151281.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Arastoo M. Modeling Micro-Damage Healing Mechanism at Micro-Scale. [Thesis]. Texas A&M University; 2013. Available from: http://hdl.handle.net/1969.1/151281

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Texas A&M University

2. Shakiba, Maryam. A Continuum Coupled Moisture-mechanical Constitutive Model for Asphalt Concrete.

Degree: 2013, Texas A&M University

The presence and flow of moisture degrade engineering properties of asphalt concrete as part of thermodynamic, chemical, physical, and mechanical processes. This detrimental effect is referred to as moisture damage. The aim of this dissertation is the development of physically based constitutive relationships along with a computational tool for the fundamental analysis of combined mechanical and moisture induced damage of asphalt concrete. Such a tool can greatly contribute to an improved material selection procedure and give insight into the various damage inducing mechanisms in asphalt concrete. In this dissertation, thermo-hygro-mechanical constitutive relationships are developed based on the principle of virtual power and laws of thermodynamics in order to simulate moisture-induced damage of asphalt concrete. An evolution function is proposed to consider the detrimental effect of moisture diffusion and presence inside the material. The effect of pore water pressure is incorporated using Biot?s coefficient. The Continuum Damage Mechanics (CDM) theory is extended to Continuum Moisture-Mechanical Damage Mechanics (CMMDM) to incorporate the moisture degradation effect and couple it to the mechanical response of asphalt concrete. The proposed moisture damage constitutive relationships are implemented in the Pavement Analysis using Nonlinear Damage Approach (PANDA) finite element (FE) package to model the moisture damage effect on the complex environmental-mechanical response of asphalt concrete. The developed constitutive relationship and framework are validated over different loading scenarios and a range of experimental measurements. The developed constitutive relationship and framework are applied to simulate pavement performance. The focus is on investigating the effects of various moisture conditioning periods on permanent deformation (rutting) and fatigue damage of asphalt pavements. The constitutive and computational models are used to develop a framework for the simulation of the effect of moisture on the microstructural response of asphalt concrete. This framework explicitly incorporates the material microstructural distribution and properties. The developed framework is used to perform two-dimensional (2D) and three-dimensional (3D) micromechanical simulations in order to study and investigate the capability of the proposed constitutive relationships to predict the microstructural response of asphalt concrete under combined effect of moisture diffusion and mechanical loading. Advisors/Committee Members: Little, Dallas (advisor), Masad, Eyad (advisor), Reddy, Junuthula (committee member), Muliana, Anastasia (committee member), Hueste, Mary (committee member), Darabi, Masoud (committee member).

Subjects/Keywords: Moisture Damage; Asphalt Concrete Pavements; Continuum Moisture-Mechanical Coupling

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Shakiba, M. (2013). A Continuum Coupled Moisture-mechanical Constitutive Model for Asphalt Concrete. (Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/151963

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Shakiba, Maryam. “A Continuum Coupled Moisture-mechanical Constitutive Model for Asphalt Concrete.” 2013. Thesis, Texas A&M University. Accessed May 27, 2019. http://hdl.handle.net/1969.1/151963.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Shakiba, Maryam. “A Continuum Coupled Moisture-mechanical Constitutive Model for Asphalt Concrete.” 2013. Web. 27 May 2019.

Vancouver:

Shakiba M. A Continuum Coupled Moisture-mechanical Constitutive Model for Asphalt Concrete. [Internet] [Thesis]. Texas A&M University; 2013. [cited 2019 May 27]. Available from: http://hdl.handle.net/1969.1/151963.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Shakiba M. A Continuum Coupled Moisture-mechanical Constitutive Model for Asphalt Concrete. [Thesis]. Texas A&M University; 2013. Available from: http://hdl.handle.net/1969.1/151963

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Texas A&M University

3. Rahmani, Eisa. Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete.

Degree: 2015, Texas A&M University

Oxidative aging is known to be one of the main contributors to reducing the service life of asphalt pavements. Asphalt concrete becomes stiffer and more brittle when it reacts with oxygen. The aged asphalt pavement is more susceptible to crack development and damages when subjected to repeated traffic loading. The aim of this dissertation is to develop and validate a mechanistic-based aging constitutive relationship based on an aging state variable. Oxidative aging of asphalt concrete involves a thermodynamic process between reactive molecules of asphalt and oxygen. The repercussion of such a process is a change in mechanical, macroscopic properties of the material. This phenomenon is accounted for in this study by formulating an aging constitutive equation, based on continuum theory, in which the aging state variable is correlated with oxygen content via an evolution function. In this aging constitutive equation, the rate of change of the aging variable and oxygen content are formulated as conjugate variables. In other words, oxygen content is considered as the driving force for the rate of change of the aging variable. The rate of change of the aging state variable is expressed as a function of oxygen content, temperature, and level of aging at any given time. The behavior of asphalt concrete is modeled using the PANDA (Pavement Analysis Using a Nonlinear Damage Approach) framework, which accounts for the viscoelastic, viscodamage, and viscoplastic behavior of the materials. The time-dependent response of aged asphalt concrete is investigated by introducing the aging state variable to Schapery?s viscoelastic model. The aging state variable causes an increase in the stiffness and viscosity of the aged material by decreasing the compliance terms and the retardation times. Because the viscoelastic, viscodamage, and viscoplastic components of PANDA are coupled or interrelated, the change in the viscoelastic properties, because of aging, affects the overall mechanical behavior of asphalt concrete. The aging constitutive equation is calibrated using data obtained from laboratory experiments, and then its predictions are validated against independent experimental data. It is shown that the proposed model is capable of predicting mechanical response of aged asphalt concrete specimens subjected to different loading conditions. Advisors/Committee Members: Little, Dallas N (advisor), Masad, Eyad A (advisor), Hueste, Mary Beth D (committee member), Glover, Charles J (committee member), Allen, David H (committee member), Darabi, Masoud K (committee member).

Subjects/Keywords: Oxidative aging; Asphalt concrete; Continuum Damage Mechanics; Constitutive modeling; Viscoelasticity; Viscoplasticity; Viscodamage; Fatigue damage

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Rahmani, E. (2015). Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete. (Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/155201

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Rahmani, Eisa. “Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete.” 2015. Thesis, Texas A&M University. Accessed May 27, 2019. http://hdl.handle.net/1969.1/155201.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Rahmani, Eisa. “Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete.” 2015. Web. 27 May 2019.

Vancouver:

Rahmani E. Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete. [Internet] [Thesis]. Texas A&M University; 2015. [cited 2019 May 27]. Available from: http://hdl.handle.net/1969.1/155201.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Rahmani E. Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete. [Thesis]. Texas A&M University; 2015. Available from: http://hdl.handle.net/1969.1/155201

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.