The Experts below are selected from a list of 39654 Experts worldwide ranked by ideXlab platform

Christian Hesch - One of the best experts on this subject based on the ideXlab platform.

  • variational modeling of thermomechanical Fracture and anisotropic frictional mortar contact problems with adhesion
    Computational Mechanics, 2019
    Co-Authors: M Dittmann, Melanie Kruger, F Schmidt, S Schus, Christian Hesch
    Abstract:

    Phase-field formulations to Fracture and sophisticated mortar contact formulations are well established techniques nowadays. For a wide range of applications, these two variationally consistent approaches could already demonstrate their superiority compared with more traditional methods in terms of generality, performance and accuracy. In the present contribution we combine both methodologies in a unified computational framework to deal with large deformation thermo-Fracture mechanical contact problems. In particular, a temperature dependent model for the Critical Fracture energy density as well as a phase-field dependent model for the heat conduction are taken into account along with a temperature dependent contact model. To be specific, an adhesive anisotropic friction model is considered for the contact in tangential direction, whereas an exponential adhesion model is applied for the normal contact definition. These models are incorporated within the thermal phase-field approach in a thermodynamically consistent formulation. Eventually, a variety of representative numerical examples demonstrates the capabilities of this novel framework.

  • variational phase field formulation of non linear ductile Fracture
    Computer Methods in Applied Mechanics and Engineering, 2018
    Co-Authors: M Dittmann, Fadi Aldakheel, J Schulte, Peter Wriggers, Christian Hesch
    Abstract:

    Abstract Variationally consistent phase-field methods have been well established in the recent decade. A wide range of applications to brittle and ductile Fracture problems could already demonstrate the ability to predict complex crack patterns in three-dimensional geometries. However, current phase-field models to ductile Fracture are not formulated for both, material and geometrical non-linearities. In this contribution we present a computational framework to account for three-dimensional Fracture in ductile solids undergoing large elastic and plastic deformations. The proposed model is based on a triple multiplicative decomposition of the deformation gradient and an exponential update scheme for the return map in the time discrete setting. This increases the accuracy on the entire range of the ductile material behavior encompassing elastoplasticity, hardening, necking, crack initiation and propagation. The accuracy and convergence properties are further improved by the application of a higher order phase-field regularization and a gradient enhanced plasticity model. To account for the ductile behavior at Fracture, a model of the Critical Fracture energy density depending on the equivalent plastic strain is proposed and validated by experimental data.

Hoki Ban - One of the best experts on this subject based on the ideXlab platform.

  • moisture damage characterization of warm mix asphalt mixtures based on laboratory field evaluation
    Construction and Building Materials, 2012
    Co-Authors: Yongrak Kim, Jun Zhang, Hoki Ban
    Abstract:

    Abstract This study presents laboratory evaluation integrated with field performance to examine two widely used warm-mix asphalt (WMA) approaches—foaming and emulsion technology. For a more realistic evaluation of the WMA approaches, trial pavement sections of the WMA mixtures and their counterpart hot-mix asphalt (HMA) mixtures were implemented in Antelope County, Nebraska. Field-mixed loose mixtures collected at the time of paving were transported to the laboratories to conduct various experimental evaluations of the individual mixtures. Among the laboratory tests, three (two conventional and one newly attempted) were performed to characterize moisture damage potential which is the primary focus of this study. From the laboratory test results, WMA mixtures showed greater susceptibility to moisture conditioning than the HMA mixtures, and this trend was identical from multiple moisture damage parameters including the strength ratio and the Critical Fracture energy ratio. Early-stage field performance data collected for three years after placement presented satisfactory rutting–cracking performance from both the WMA and HMA sections, which generally agrees with laboratory evaluations. Although the field performance data indicated that both the WMA and HMA show similar good performance, careful observation of field performance over a period of years is necessary since moisture damage can be accelerated after rutting or cracking as a later-stage pavement distress.

  • moisture damage characterization of warm mix asphalt mixtures based on laboratory field evaluation
    Transportation Research Board 91st Annual MeetingTransportation Research Board, 2012
    Co-Authors: Yongrak Kim, Jun Zhang, Hoki Ban
    Abstract:

    This study presents laboratory evaluation integrated with field performance to examine two widely used warm-mix asphalt (WMA) approaches—forming and emulsion technology. For a more realistic evaluation of the WMA approaches, trial pavement sections of the WMA mixtures and their counterpart hot-mix asphalt (HMA) mixtures are implemented in Antelope County, Nebraska. Field-mixed loose mixtures collected at the time of paving are transported to the laboratories to conduct various experimental evaluations of the individual mixtures. Among the laboratory tests, three (two conventional and one newly attempted) are performed to characterize moisture damage potential which is the primary focus of this study. From the laboratory test results, WMA mixtures show greater susceptibility to moisture conditioning than the HMA mixtures, and this trend is demonstrated by multiple moisture damage parameters including the strength ratio and the Critical Fracture energy ratio. Early-stage field performance data collected for three years after placement present satisfactory rutting-cracking performance from both the WMA and HMA sections, which agrees with laboratory evaluations. Although the field performance data indicate that both the WMA and HMA show similar good performance, careful observation of field performance over a period of years is necessary, since moisture damage is a later-stage pavement distress typically accelerated by rutting and cracking.

Waiching Sun - One of the best experts on this subject based on the ideXlab platform.

  • a mixed mode phase field Fracture model in anisotropic rocks with consistent kinematics
    Computer Methods in Applied Mechanics and Engineering, 2018
    Co-Authors: Eric Cushman Bryant, Waiching Sun
    Abstract:

    Abstract Under a pure tensile loading, cracks in brittle, isotropic, and homogeneous materials often propagate such that pure mode I kinematics are maintained at the crack tip. However, experiments performed on geo-materials, such as sedimentary rock, shale, mudstone, concrete and gypsum, often lead to the conclusion that the mode I and mode II Critical Fracture energies/surface energy release rates are distinctive. This distinction has great influence on the formation and propagation of wing cracks and secondary cracks from pre-existing flaws under a combination of shear and tensile or shear and compressive loadings. To capture the mixed-mode Fracture propagation, a mixed-mode I/II Fracture model that employs multiple Critical energy release rates based on Shen and Stephansson, IJRMMS, 1993 is reformulated in a regularized phase field Fracture framework. We obtain the mixed-mode driving force of the damage phase field by balancing the microforce. Meanwhile, the crack propagation direction and the corresponding kinematics modes are determined via a local Fracture dissipation maximization problem. Several numerical examples that demonstrate mode II and mixed-mode crack propagation in brittle materials are presented. Possible extensions of the model capturing degradation related to shear/compressive damage, as commonly observed in sub-surface applications and triaxial compression tests, are also discussed.

M Dittmann - One of the best experts on this subject based on the ideXlab platform.

  • variational modeling of thermomechanical Fracture and anisotropic frictional mortar contact problems with adhesion
    Computational Mechanics, 2019
    Co-Authors: M Dittmann, Melanie Kruger, F Schmidt, S Schus, Christian Hesch
    Abstract:

    Phase-field formulations to Fracture and sophisticated mortar contact formulations are well established techniques nowadays. For a wide range of applications, these two variationally consistent approaches could already demonstrate their superiority compared with more traditional methods in terms of generality, performance and accuracy. In the present contribution we combine both methodologies in a unified computational framework to deal with large deformation thermo-Fracture mechanical contact problems. In particular, a temperature dependent model for the Critical Fracture energy density as well as a phase-field dependent model for the heat conduction are taken into account along with a temperature dependent contact model. To be specific, an adhesive anisotropic friction model is considered for the contact in tangential direction, whereas an exponential adhesion model is applied for the normal contact definition. These models are incorporated within the thermal phase-field approach in a thermodynamically consistent formulation. Eventually, a variety of representative numerical examples demonstrates the capabilities of this novel framework.

  • variational phase field formulation of non linear ductile Fracture
    Computer Methods in Applied Mechanics and Engineering, 2018
    Co-Authors: M Dittmann, Fadi Aldakheel, J Schulte, Peter Wriggers, Christian Hesch
    Abstract:

    Abstract Variationally consistent phase-field methods have been well established in the recent decade. A wide range of applications to brittle and ductile Fracture problems could already demonstrate the ability to predict complex crack patterns in three-dimensional geometries. However, current phase-field models to ductile Fracture are not formulated for both, material and geometrical non-linearities. In this contribution we present a computational framework to account for three-dimensional Fracture in ductile solids undergoing large elastic and plastic deformations. The proposed model is based on a triple multiplicative decomposition of the deformation gradient and an exponential update scheme for the return map in the time discrete setting. This increases the accuracy on the entire range of the ductile material behavior encompassing elastoplasticity, hardening, necking, crack initiation and propagation. The accuracy and convergence properties are further improved by the application of a higher order phase-field regularization and a gradient enhanced plasticity model. To account for the ductile behavior at Fracture, a model of the Critical Fracture energy density depending on the equivalent plastic strain is proposed and validated by experimental data.

Yongrak Kim - One of the best experts on this subject based on the ideXlab platform.

  • moisture damage characterization of warm mix asphalt mixtures based on laboratory field evaluation
    Construction and Building Materials, 2012
    Co-Authors: Yongrak Kim, Jun Zhang, Hoki Ban
    Abstract:

    Abstract This study presents laboratory evaluation integrated with field performance to examine two widely used warm-mix asphalt (WMA) approaches—foaming and emulsion technology. For a more realistic evaluation of the WMA approaches, trial pavement sections of the WMA mixtures and their counterpart hot-mix asphalt (HMA) mixtures were implemented in Antelope County, Nebraska. Field-mixed loose mixtures collected at the time of paving were transported to the laboratories to conduct various experimental evaluations of the individual mixtures. Among the laboratory tests, three (two conventional and one newly attempted) were performed to characterize moisture damage potential which is the primary focus of this study. From the laboratory test results, WMA mixtures showed greater susceptibility to moisture conditioning than the HMA mixtures, and this trend was identical from multiple moisture damage parameters including the strength ratio and the Critical Fracture energy ratio. Early-stage field performance data collected for three years after placement presented satisfactory rutting–cracking performance from both the WMA and HMA sections, which generally agrees with laboratory evaluations. Although the field performance data indicated that both the WMA and HMA show similar good performance, careful observation of field performance over a period of years is necessary since moisture damage can be accelerated after rutting or cracking as a later-stage pavement distress.

  • moisture damage characterization of warm mix asphalt mixtures based on laboratory field evaluation
    Transportation Research Board 91st Annual MeetingTransportation Research Board, 2012
    Co-Authors: Yongrak Kim, Jun Zhang, Hoki Ban
    Abstract:

    This study presents laboratory evaluation integrated with field performance to examine two widely used warm-mix asphalt (WMA) approaches—forming and emulsion technology. For a more realistic evaluation of the WMA approaches, trial pavement sections of the WMA mixtures and their counterpart hot-mix asphalt (HMA) mixtures are implemented in Antelope County, Nebraska. Field-mixed loose mixtures collected at the time of paving are transported to the laboratories to conduct various experimental evaluations of the individual mixtures. Among the laboratory tests, three (two conventional and one newly attempted) are performed to characterize moisture damage potential which is the primary focus of this study. From the laboratory test results, WMA mixtures show greater susceptibility to moisture conditioning than the HMA mixtures, and this trend is demonstrated by multiple moisture damage parameters including the strength ratio and the Critical Fracture energy ratio. Early-stage field performance data collected for three years after placement present satisfactory rutting-cracking performance from both the WMA and HMA sections, which agrees with laboratory evaluations. Although the field performance data indicate that both the WMA and HMA show similar good performance, careful observation of field performance over a period of years is necessary, since moisture damage is a later-stage pavement distress typically accelerated by rutting and cracking.