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  • 1
    Online Resource
    Online Resource
    Ductile failure with gradient plasticity coupled to the phase‐field fracture at finite strains
    Wiley ; 2015
    In:  PAMM Vol. 15, No. 1 ( 2015-10), p. 271-272
    Details
    In: PAMM, Wiley, Vol. 15, No. 1 ( 2015-10), p. 271-272
    Abstract: Most metals fail in a ductile fashion, i.e, fracture is preceded by significant plastic deformation. The modeling of failure in ductile metals must account for complex phenomena at micro‐scale, such as nucleation, growth and coalescence of micro‐voids. In this work, we start with von‐Mises plasticity model without considering void generation. The modeling of macroscopic cracks can be achieved in a convenient way by the continuum phase field approaches to fracture, which are based on the regularization of sharp crack discontinuities [1]. This avoids the use of complex discretization methods for crack discontinuities and can account for complex crack patterns. The key aspect of this work is the extension of the energetic and the stress‐based phase field driving force function in brittle fracture to account for a coupled elasto‐plastic response in line with our recent work [3] . We develop a new theoretical and computational framework for the phase field modeling of ductile fracture in elastic‐plastic solids. To account for large strains, the constitutive model is constructed in the logarithmic strain space, which simplify the model equations and results in a formulation similar to small strains. We demonstrate the modeling capabilities and algorithmic performance of the proposed formulation by representative simulations of ductile failure mechanisms in metals. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
    Type of Medium: Online Resource
    ISSN: 1617-7061 , 1617-7061
    URL: Issue
    URL: Article
    DOI: 10.1002/pamm.v15.1
    DOI: 10.1002/pamm.201510126
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2078931-2
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  • 2
    Online Resource
    Online Resource
    A Phase‐Field Model of Ductile Fracture at Finite Strains
    Wiley ; 2016
    In:  PAMM Vol. 16, No. 1 ( 2016-10), p. 181-182
    Details
    In: PAMM, Wiley, Vol. 16, No. 1 ( 2016-10), p. 181-182
    Abstract: This work outlines a variational‐based framework for the phase field modeling of ductile fracture in elastic‐plastic solids at large strains. The phase field approach regularizes sharp crack discontinuities within a pure continuum setting by a specific gradient damage model with geometric features rooted in fracture mechanics. Based on the recent works [1, 2], the phase field model of ductile fracture is linked to a formulation of gradient plasticity at finite strains in order to ensure the crack to evolve inside the plastic zones. The thermodynamic formulation is based on the definition of a constitutive work density function including the stored elastic energy and the dissipated work due to plasticity and fracture. The proposed canonical theory is shown to be governed by a rate‐type minimization principle, which determines the coupled multi‐field evolution problem. Another aspect is the regularization towards a micromorphic gradient plasticity‐damage setting which enhances the robustness of the finite element formulation. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
    Type of Medium: Online Resource
    ISSN: 1617-7061 , 1617-7061
    URL: Issue
    URL: Article
    DOI: 10.1002/pamm.v16.1
    DOI: 10.1002/pamm.201610079
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 2078931-2
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  • 3
    Online Resource
    Online Resource
    Towards Phase Field Modeling of Ductile Fracture in Gradient‐Extended Elastic‐Plastic Solids
    Wiley ; 2014
    In:  PAMM Vol. 14, No. 1 ( 2014-12), p. 411-412
    Details
    In: PAMM, Wiley, Vol. 14, No. 1 ( 2014-12), p. 411-412
    Abstract: The modeling of failure in ductile metals must account for complex phenomena at a micro‐scale as well as the final rupture at the macro‐scale. Within a top‐down viewpoint, this can be achieved by the combination of a micro‐structure‐informed elastic‐plastic model with a concept for the modeling of macroscopic crack discontinuities. In this context, it is important to account for material length scales and thermo‐mechanical coupling effects due to dissipative heating. This can be achieved by the construction of non‐standard, gradient‐enhanced models of plasticity with a full embedding into continuum thermodynamics [1,2]. The modeling of macroscopic cracks can be achieved in a convenient way by recently developed continuum phase field approaches to fracture based on regularized crack discontinuities. This avoids the use of complex discretization methods for crack discontinuities, and can account for complex crack patterns within a pure continuum formulation. Moreover, the phase field modeling of fracture is related to gradient theories of continuum damage mechanics, and fits nicely the structure of constitutive models for gradient plasticity. The main focus of this work is the extensions to gradient thermoplasticity and phase field formulation of ductile fracture, conceptually in line with the work [3] . (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
    Type of Medium: Online Resource
    ISSN: 1617-7061 , 1617-7061
    URL: Issue
    URL: Article
    DOI: 10.1002/pamm.v14.1
    DOI: 10.1002/pamm.201410193
    Language: English
    Publisher: Wiley
    Publication Date: 2014
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  • 4
    Online Resource
    Online Resource
    3D Virtual Elements for Elastodynamic Problems
    Wiley ; 2021
    In:  PAMM Vol. 20, No. 1 ( 2021-01)
    Details
    In: PAMM, Wiley, Vol. 20, No. 1 ( 2021-01)
    Abstract: A virtual element framework for nonlinear elastodynamics is outlined within this work. The virtual element method (VEM) can be considered as an extension of the classical finite element method. While the finite element method (FEM) is restricted to the usage of regular shaped elements, VEM allows to use non‐convex shaped elements for the spatial discretization [1]. It has been applied to various engineering problems in elasticity and other areas, such as plasticity or fracture mechanics as outlined in [3, 4] . This work deals with the extension of VEM to dynamic problems. Low‐order ansatz functions in two and three dimensions, with elements being arbitrary shaped, are used in this contribution. The formulations considered in this framework are based on minimization of energy, where a pseudo potential is used for the dynamic behavior. While the stiffness‐matrix needs a suitable stabilization, the mass‐matrix can be calculated fully through the projection part. For the implicit time integration, Newmark‐Method is used. To show the performance of the method, various numerical examples in 2D and 3D are presented.
    Type of Medium: Online Resource
    ISSN: 1617-7061 , 1617-7061
    URL: Issue
    URL: Article
    DOI: 10.1002/pamm.v20.1
    DOI: 10.1002/pamm.202000175
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2078931-2
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  • 5
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    Online Resource
    A design concept of active cooling for tailored forming workpieces during induction heating
    Springer Science and Business Media LLC ; 2021
    In:  Production Engineering Vol. 15, No. 2 ( 2021-04), p. 177-186
    Details
    In: Production Engineering, Springer Science and Business Media LLC, Vol. 15, No. 2 ( 2021-04), p. 177-186
    Abstract: The demand for lightweight construction is constantly increasing. One approach to meet this challenge is the development of hybrid components made of dissimilar materials. The use of the hybrid construction method for bulk components has a high potential for weight reduction and increased functionality. However, forming workpieces consisting of dissimilar materials requires specific temperature profiles for achieving sufficient formability. This paper deals with the development of a specific heating and cooling strategy to generate an inhomogeneous temperature distribution in hybrid workpieces. Firstly, the heating process boundaries with regard to temperature parameters required for a successful forming are experimentally defined. Secondly, a design based on the obtained cooling strategy is developed. Next a modelling embedded within an electro-thermal framework provides the basis for a numerical determination of admissible cooling rates to fulfil the temperature constraint. Here, the authors illustrate an algorithmic approach for the optimisation of cooling parameters towards an effective minimum, required for applicable forming processes of tailored forming.
    Type of Medium: Online Resource
    ISSN: 0944-6524 , 1863-7353
    URL: Article
    DOI: 10.1007/s11740-021-01027-5
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2376946-4
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  • 6
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    Online Resource
    Influence of Moisture Content and Wet Environment on the Fatigue Behaviour of High-Strength Concrete
    MDPI AG ; 2022
    In:  Materials Vol. 15, No. 3 ( 2022-01-28), p. 1025-
    Details
    In: Materials, MDPI AG, Vol. 15, No. 3 ( 2022-01-28), p. 1025-
    Abstract: The influence of a wet environment on the fatigue behaviour of high-strength concrete has become more important in recent years with the expansion of offshore wind energy systems. According to the few investigations documented in the literature, the fatigue resistance of specimens submerged in water is significantly lower compared to that of specimens in dry conditions. However, it is still not clear how the wet environment and the moisture content in concrete influence its fatigue behaviour and which damage mechanisms are involved in the deterioration process. Here the results of a joint project are reported, in which the impact of moisture content in concrete on fatigue deterioration are investigated experimentally and numerically. Aside from the number of cycles to failure, the development of stiffness and acoustic emission (AE) hits are analysed as damage inductors and discussed along with results of microstructural investigations to provide insights into the degradation mechanisms. Subsequently, an efficient numeric modelling approach to water-induced fatigue damage is presented. The results of the fatigue tests show an accelerated degradation behaviour with increasing moisture content of the concrete. Further, it was found that the AE hits of specimens submerged in water occur exclusively close to the minimum stress level in contrast to specimens subjected to dry conditions, which means that additional damage mechanisms are acting with increasing moisture content in the concrete.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma15031025
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2487261-1
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  • 7
    Online Resource
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    A microscale model for concrete failure in poro-elasto-plastic media
    Elsevier BV ; 2020
    In:  Theoretical and Applied Fracture Mechanics Vol. 107 ( 2020-06), p. 102517-
    Details
    In: Theoretical and Applied Fracture Mechanics, Elsevier BV, Vol. 107 ( 2020-06), p. 102517-
    Type of Medium: Online Resource
    ISSN: 0167-8442
    URL: Article
    DOI: 10.1016/j.tafmec.2020.102517
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2020
    detail.hit.zdb_id: 2013739-4
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  • 8
    Online Resource
    Online Resource
    A modified Gurson-type plasticity model at finite strains: formulation, numerical analysis and phase-field coupling
    Springer Science and Business Media LLC ; 2018
    In:  Computational Mechanics Vol. 62, No. 4 ( 2018-10), p. 815-833
    Details
    In: Computational Mechanics, Springer Science and Business Media LLC, Vol. 62, No. 4 ( 2018-10), p. 815-833
    Type of Medium: Online Resource
    ISSN: 0178-7675 , 1432-0924
    URL: Article
    DOI: 10.1007/s00466-017-1530-0
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 1458937-0
    detail.hit.zdb_id: 799787-5
    SSG: 11
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  • 9
    Online Resource
    Online Resource
    3D mixed virtual element formulation for dynamic elasto-plastic analysis
    Springer Science and Business Media LLC ; 2021
    In:  Computational Mechanics Vol. 68, No. 3 ( 2021-09), p. 1-18
    Details
    In: Computational Mechanics, Springer Science and Business Media LLC, Vol. 68, No. 3 ( 2021-09), p. 1-18
    Abstract: The virtual element method (VEM) for dynamic analyses of nonlinear elasto-plastic problems undergoing large deformations is outlined within this work. VEM has been applied to various problems in engineering, considering elasto-plasticity, multiphysics, damage, elastodynamics, contact- and fracture mechanics. This work focuses on the extension of VEM formulations towards dynamic elasto-plastic applications. Hereby low-order ansatz functions are employed in three dimensions with elements having arbitrary convex or concave polygonal shapes. The formulations presented in this study are based on minimization of potential function for both the static as well as the dynamic behavior. Additionally, to overcome the volumetric locking phenomena due to elastic and plastic incompressibility conditions, a mixed formulation based on a Hu-Washizu functional is adopted. For the implicit time integration scheme, Newmark method is used. To show the model performance, various numerical examples in 3D are presented.
    Type of Medium: Online Resource
    ISSN: 0178-7675 , 1432-0924
    URL: Article
    DOI: 10.1007/s00466-021-02010-8
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 1458937-0
    detail.hit.zdb_id: 799787-5
    SSG: 11
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  • 10
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    Online Resource
    A general phase-field model for fatigue failure in brittle and ductile solids
    Springer Science and Business Media LLC ; 2021
    In:  Computational Mechanics Vol. 67, No. 5 ( 2021-05), p. 1431-1452
    Details
    In: Computational Mechanics, Springer Science and Business Media LLC, Vol. 67, No. 5 ( 2021-05), p. 1431-1452
    Abstract: In this work, the phase-field approach to fracture is extended to model fatigue failure in high- and low-cycle regime. The fracture energy degradation due to the repeated externally applied loads is introduced as a function of a local energy accumulation variable, which takes the structural loading history into account. To this end, a novel definition of the energy accumulation variable is proposed, allowing the fracture analysis at monotonic loading without the interference of the fatigue extension, thus making the framework generalised. Moreover, this definition includes the mean load influence of implicitly. The elastoplastic material model with the combined nonlinear isotropic and nonlinear kinematic hardening is introduced to account for cyclic plasticity. The ability of the proposed phenomenological approach to naturally recover main features of fatigue, including Paris law and Wöhler curve under different load ratios is presented through numerical examples and compared with experimental data from the author’s previous work. Physical interpretation of additional fatigue material parameter is explored through the parametric study.
    Type of Medium: Online Resource
    ISSN: 0178-7675 , 1432-0924
    URL: Article
    DOI: 10.1007/s00466-021-01996-5
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 1458937-0
    detail.hit.zdb_id: 799787-5
    SSG: 11
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