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See detailAccelerating fatigue simulations of a phase-field damage model for rubber
Loew, Pascal Juergen UL; Poh, Leong Hien; Peters, Bernhard UL et al

in Computer Methods in Applied Mechanics and Engineering (2020), 370(113247),

Phase-field damage models are able to describe crack nucleation as well as crack propagation and coalescence without additional technicalities, because cracks are treated in a continuous, spatially finite ... [more ▼]

Phase-field damage models are able to describe crack nucleation as well as crack propagation and coalescence without additional technicalities, because cracks are treated in a continuous, spatially finite manner. Previously, we have developed a phase-field model to capture the rate-dependent failure of rubber, and we have further enhanced it to describe failure due to cyclic loading. Although the model accurately describes fatigue failure, the associated cyclic simulations are slow. Therefore, this contribution presents an acceleration scheme for cyclic simulations of our previously introduced phase-field damage model so that the simulation speed is increased to facilitate large-scale simulations of industrially relevant problems. We formulate an explicit and an implicit cycle jump method, which, depending on the selected jump size, reduce the calculation time up to 99.5%. To circumvent the manual tuning of the jump size, we also present an adaptive jump size selection procedure. Thanks to the implicit adaptive scheme, all material parameters are identified from experiments, which include fatigue crack nucleation and crack growth. Finally, the model and its parameters are validated with additional measurements of the fatigue crack growth rate. [less ▲]

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See detailFatigue phase-field damage modeling of rubber using viscous dissipation: Crack nucleation and propagation
Loew, Pascal Juergen UL; Peters, Bernhard UL; Beex, Lars UL

in Mechanics of Materials (2020), 142

By regularizing sharp cracks within a pure continuum setting, phase-damage models offer the ability to capture crack nucleation as well as crack propagation. Crack branching and coalescence can ... [more ▼]

By regularizing sharp cracks within a pure continuum setting, phase-damage models offer the ability to capture crack nucleation as well as crack propagation. Crack branching and coalescence can furthermore be described without any additional efforts, as geometrical descriptions of the cracks are not required. In this contribution, we extend our previous phase-field model for rate-dependent fracture of rubbers in a finite strain setting (Loew et al., 2019) to describe damage under cyclic loading. The model is derived from the balance of mechanical energy and introduces a fatigue damage source as a function of the accumulated viscous dissipation under cyclic loading. We use uniaxial cyclic tension to present the influence of the fatigue material parameters and to confirm the model’s energy balance. The parameters are subsequently identified using monotonic and cyclic experiments of a plane stress nature. Finally, the model is validated by separate experiments, which demonstrate that the model accurately predicts (fatigue) crack nucleation as well as propagation. [less ▲]

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See detailPhase field fracture model for viscoplastic materials in large deformations
Kabore, Brice Wendlassida UL; Loew, Pascal Juergen UL; Peters, Bernhard UL

Scientific Conference (2019, June 13)

Phase-field modeling approach to material fracture and damage has received a growing interest among researchers. It has proven to be an effective way to address crack related discontinuities in continuum ... [more ▼]

Phase-field modeling approach to material fracture and damage has received a growing interest among researchers. It has proven to be an effective way to address crack related discontinuities in continuum mechanics. Also, it solves the problem related to tracking the fracture surface by simply representing the fracture phase with a continuous field variable. Recently, phase-field fracture models have been extended to finite deformations, crack nucleation and applied to complex material behaviors such as plasticity and viscoplasticity. In this contribution we describe a viscoplastic model coupled with a phase-field dynamic fracture model in a large strain formulation. The model include damage, history, rate and temperature dependent behavior. A finite element implementation is presented in a staggered time integration. Moreover, we address the crack closure and crack surfaces interpenetration taking into account tension-compression strength asymmetry. Performance of the model on dynamic crack propagation are presented. [less ▲]

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See detailRate-dependent phase-field damage modeling of rubber and its experimental parameter identification
Loew, Pascal Juergen UL; Peters, Bernhard UL; Beex, Lars UL

in Journal of the Mechanics and Physics of Solids (2019)

Phase-field models have the advantage in that no geometric descriptions of cracks are required, which means that crack coalescence and branching can be treated without additional effort. Miehe and ... [more ▼]

Phase-field models have the advantage in that no geometric descriptions of cracks are required, which means that crack coalescence and branching can be treated without additional effort. Miehe and Schänzel (2014) introduced a rate-independent phase-field damage model for finite strains in which a viscous damage regularization was proposed. We extend the model to depend on the loading rate and time by incorporating rubber’s strain-rate dependency in the constitutive description of the bulk, as well as in the damage driving force. The parameters of the model are identified using experiments at different strain rates. Local strain fields near the crack tip, obtained with digital image correlation (DIC), are used to help identify the length scale parameter. Three different degradation functions are assessed for their accuracy to model the rubber’s rate-dependent fracture. An adaptive time-stepping approach with a corrector scheme is furthermore employed to increase the computational efficiency with a factor of six, whereas an active set method guarantees the irreversibility of damage. Results detailing the energy storage and dissipation of the different model constituents are included, as well as validation results that show promising capabilities of rate-dependent phase-field modeling. [less ▲]

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