Efficient and robust numerical treatment of a gradient‐enhanced damage model at large deformations

Junker, Philipp; Riesselmann, Johannes; Balzani, Daniel

doi:10.1002/nme.6876

Cited by 13 publications

(5 citation statements)

References 37 publications

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“…The SED is a commonly used measure for predicting failure. [45][46][47] Particularly high local gradients in SED indicate the possibility of a crack initiation which may lead to a failure of the membrane. It is important to ensure that the SED does not exceed the calculated values obtained from the tensile test simulation at the point of failure, as it would increase the likelihood of failure.…”

Section: Simulation Of the Pemwe Cell Setup And Its Resultsmentioning

confidence: 99%

Structural Mechanics Analysis of Woven Web Reinforced Membranes in Proton Exchange Membrane Water Electrolysis

Kink,

Ise,

Bensmann

et al. 2023

J. Electrochem. Soc.

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Membranes are a key component of proton exchange membrane water electrolysis (PEMWE) cells and are exposed to various stressors during operation, which can significantly reduce cell lifetime. PEMWE membranes incorporating woven web layers within the membrane structure for mechanical reinforcement are a promising, commonly-used industrial strategy to mitigate the formation of membrane defects. Here, the structural mechanics of a PEMWE cell were investigated, specifically the woven web reinforced membrane. Experimental tensile tests were conducted on the membrane to obtain stress-strain data. These measurements were utilized to parameterize a geometrically simplified model of the woven web reinforced membrane through a tensile test simulation. The validated model was applied in a 2D-cell simulation to identify resulting stresses and strains in the membrane during various electrolysis operation modes. The results herein allow the used PEMWE cell geometry to be systematically evaluated and optimized with respect to mechanical membrane stability. For the applied PEMWE cell setup, no failure is expected during normal operation, including varied temperatures and differential pressure. Increasing the gap size at the edge of the electrochemically active cell area, however, leads to large deformations when the gap becomes larger than 0.2 mm.

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Section: Simulation Of the Pemwe Cell Setup And Its Resultsmentioning

confidence: 99%

Structural Mechanics Analysis of Woven Web Reinforced Membranes in Proton Exchange Membrane Water Electrolysis

Kink,

Ise,

Bensmann

et al. 2023

J. Electrochem. Soc.

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“…The strain energy density is a possible indicator of failure. [42][43][44] Comparison of the simulation results with experimental failure stress and strain show a maximum energy density of 7.41 MJ m −3 for dry membranes at room temperature, while wet membranes at 60 °C display a maximum energy density of 12.20 MJ m −3 . These values are useful in order to evaluate the likelihood of failure in cell simulations with mechanical loads applied as under assembly and operation conditions.…”

Section: Operational Step Duration In Smentioning

confidence: 94%

“…Moreover, an evaluation of the strain energy density is undertaken, as it is also a common measure for potential failure. [42][43][44] This paper is structured as follows: First, the model setup for an electrolyzer simulation is described. Next, the membrane material model and its parametrization are illustrated in detail.…”

Section: List Of Symbolsmentioning

confidence: 99%

Modeling Mechanical Behavior of Membranes in Proton Exchange Membrane Water Electrolyzers

Kink

Ise

Bensmann

et al. 2023

J. Electrochem. Soc.

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Membranes in proton exchange membrane water electrolysis (PEMWE) stacks are exposed to severe mechanical stress due to mechanical compression. Particularly critical is the gap between cell frame and porous transport layers (PTL). In this work mechanical stresses and strains on the membrane occurring during assembly and operation are quantified using a finite-element analysis applied to a simplified single cell sandwich. Within the simulation a Nafion® 117 membrane and the elastic-viscoplastic Silberstein material model is used. The material model parameters are based on and validated by experimental data from tensile tests to ensure matching with real PEMWE systems. The validated material model is used in cell simulations to identify resulting stresses and strains acting on the membrane. In accordance with experimental data, no critical states were identified. Furthermore, differential pressure up to 10 bar could not cause any significant change compared to deformations resulting during balanced pressure operation. Varying the gap size between cell frame and PTL resulted in a buckling in the simulated membrane for sizes of 0.3 mm and more during the membrane swelling. Such simulations can improve future cell designs while using an appropriate gap size with a given membrane thickness to avoid buckling and therefore possible failures.

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“…Although the use of strain gradient models is not new [15,12,20], and special Ąnite element schemes have been developed [28,29,30], one of the main challenges associated with these models is the difficulty in determining the constitutive coefficients [19]. Strain gradient models [23,24,14], incorporate additional terms in the constitutive equations which depend on the materialŠs microstructure and the speciĄc deformation modes that occur during loading [4], which can make them difficult to be determined experimentally [2]. Gedanken experiment have been proposed for isotropic [25] and anisotropic [26] pantographic cases but the use of external double forces has limited the applicability of these methods for real experimental identiĄcation.…”

Section: Introductionmentioning

confidence: 99%

A procedure for the experimental identification of the strain gradient characteristic length

Rezaei,

Riesselmann,

Misra

et al. 2024

Z. Angew. Math. Phys.

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The aim of this paper is to propose an experimental procedure for determining the characteristic length of a strain gradient model. The identification problem is studied through a virtual pull-out test of a rigid bar along the symmetry axis of a cylindrical strain gradient elastic domain. To allow an accurate parameter identification based on measured data, we investigate the effect of the characteristic length on the mechanical fields for this problem. We see a significant sensitivity of the inflection point of the displacement profile evaluated on the cross-section of the cylinder, with respect to the characteristic length. By adjusting the characteristic length of strain gradient such that the theoretical models match best with experimental measurements of the surface displacement fields, the characteristic length of strain gradient can be estimated. In order to allow for more efficient analysis and an almost real-time parameter identification the initial three-dimensional (3D) problem is reduced to a one-dimensional (1D) problem by exploiting the cylindrical symmetry of the problem. As will be shown, an accurate 1D finite element method (FEM) strain gradient solution can be obtained for this simplified problem. Since the cylindrical symmetry is only true in an infinitely long cylinder, specific boundary conditions are constructed on a cylinder of finite length, which are then used for the comparison of the 1D and 3D problem. Results show, however, that the structural response at the inflection point is insensitive to whether the specific boundary conditions are considered or not, which is why the 1D model can be used for parameter identification.Since the proposed approach is methodological, it can be applied to any material. As a prototype problem in this paper, we consider the case of bar embedded in portland cement concrete.

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Efficient and robust numerical treatment of a gradient‐enhanced damage model at large deformations

Cited by 13 publications

References 37 publications

Structural Mechanics Analysis of Woven Web Reinforced Membranes in Proton Exchange Membrane Water Electrolysis

Structural Mechanics Analysis of Woven Web Reinforced Membranes in Proton Exchange Membrane Water Electrolysis

Modeling Mechanical Behavior of Membranes in Proton Exchange Membrane Water Electrolyzers

A procedure for the experimental identification of the strain gradient characteristic length

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