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Hans J. Herrmann - One of the best experts on this subject based on the ideXlab platform.

  • Modelling snow failure with a Fibre Bundle Model
    Journal of Glaciology, 2009
    Co-Authors: Ingrid Reiweger, Jürg Schweizer, Jürg Dual, Hans J. Herrmann
    Abstract:

    Dry-snow slab avalanches initiate from a failure in a weak snow layer below a cohesive slab. Snow is considered as a porous ice structure, and the strength distribution of the single elements of this structure, i.e. grains and bonds between grains, shows a high degree of disorder. On the bond or microstructural level, the failure process is believed to start if the fracturing of bonds between snow grains is not balanced by the formation of new bonds. We use a statistical fracture Model - a Fibre Bundle Model - to study the failure process in a weak snow layer. The Model consists of Fibres of various strengths representing single snow grains between two rigid plates which represent the slab above and the substratum below the weak layer. The Fibres deform in a linear elastic manner and break instantly at their rupture strength. Broken Fibres may sinter (re-bond) and regain strength after a finite sintering time. We show that the different characteristic times for breaking and sintering lead to the rate dependence of snow strength. This is, to our knowledge, the first statistical Model to reproduce the ductile-to-brittle transition which snow exhibits with increasing strain rate. When the Model is applied to simulate experimental stress-strain curves for different strain rates, the Model and experimental results are in fair agreement.

  • Fatigue failure of disordered materials
    Journal of Statistical Mechanics: Theory and Experiment, 2007
    Co-Authors: Ferenc Kun, M. H. A. S. Costa, R. N. Costa Filho, José S. Andrade, Jorge Barbosa Soares, Stefano Zapperi, Hans J. Herrmann
    Abstract:

    We present an experimental and theoretical study of the fatigue failure of heterogeneous materials under cyclic compression considering asphalt as a specific example. Varying the load amplitude, experiments reveal a finite fatigue limit below which the specimen does not break, while approaching the tensile strength of the material a rapid failure occurs. In the intermediate load range, the lifetime decreases with the load as a power law. We introduce two novel theoretical approaches, namely, a Fibre Bundle Model and a fuse Model, and show that both capture the major microscopic mechanisms of the fatigue failure of heterogeneous materials, providing an excellent agreement with the experimental findings.

  • extension of Fibre Bundle Models for creep rupture and interface failure
    International Journal of Fracture, 2006
    Co-Authors: R C Hidalgo, Frank Raischel, Hans J. Herrmann
    Abstract:

    We present two extensions of the classical Fibre Bundle Model to study the creep rupture of heterogeneous materials and the shear failure of glued interfaces of solid blocks. To Model creep rupture, we assume that the Fibres of a parallel Bundle present time dependent behaviour under an external load and fail when the deformation exceeds their local breaking threshold. Assuming global load sharing among Fibres, analytical and numerical calculations showed that there exists a critical load below which only partial failure occurs while above which the system fails globally after a finite time. Approaching the critical point from both sides the system exhibits scaling behaviour which implies that creep rupture is analogous to continuous phase transitions. To describe interfacial failure, we Model the interface as an array of elastic beams which experience stretching and bending under shear load and break if the two deformation modes exceed randomly distributed breaking thresholds. The two breaking modes can be independent or combined in the form of a von Mises type breaking criterion. In the framework of global load sharing, we obtain analytically the macroscopic constitutive behaviour of the system and describe the microscopic process of the progressive failure of the interface.

  • Extensions of Fibre Bundle Models
    Modelling Critical and Catastrophic Phenomena in Geoscience, 2006
    Co-Authors: Feri Kun, Frank Raischel, R C Hidalgo, Hans J. Herrmann
    Abstract:

    The Fibre Bundle Model is one of the most important theoretical approaches to investigate the fracture and breakdown of disordered media extensively used both by the engineering and physics community. We present the basic construction of the Model and provide a brief overview of recent results focusing mainly on the physics literature. We discuss the limitations of the Model to describe the failure of composite materials and present recent extensions of the Model which overcome these problems making the Model more realistic: we gradually enhance the Fibre Bundle Model by generalizing the failure law, constitutive behavior, deformation state and way of interaction of Fibres. We show that beyond the understanding of the fracture of Fibre reinforced composites, these extensions of the Fibre Bundle Model also address interesting problems for the statistical physics of fracture.

Enrico A. Chiaradia - One of the best experts on this subject based on the ideXlab platform.

  • Root Characteristics of Herbaceous Species for Topsoil Stabilization in Restoration Projects
    Land Degradation & Development, 2017
    Co-Authors: Gilardelli Federica, Vergani Chiara, Gentili Rodolfo, Bonis Anne, Chanteloup Pierre, Citterio Sandra, Enrico A. Chiaradia
    Abstract:

    Quarries are highly heterogeneous and constraining environments because of man-induced disturbances associated with soil erosion and shallow mass movements. Recognizing the importance of plant root systems to overcome stability problems, we investigated the contributions of three different herbaceous species typical of calcareous grasslands, that is, Anthyllis vulneraria, Bromus erectus and Stachys recta, to the stability of the superficial layers of dump deposits at limestone quarries in the Botticino extractive basin (Lombardy, Italy). We analysed (i) the root mechanical properties and root diameter distributions of the selected species and estimated (ii) the lateral root reinforcement they can provide through the Fibre Bundle Model. To assess the effective contribution of a species to the topsoil stabilization, we implemented the results obtained in a stability Model based on the ordinary method of slices. Our results showed that using species such as B. erectus and S. recta with a density of 100 plants per square metre guarantees a better stability of the superficial layers. Copyright © 2017 John Wiley & Sons, Ltd.

  • Root Characteristics of Herbaceous Species for Topsoil Stabilization in Restoration Projects
    Land Degradation and Development, 2017
    Co-Authors: Federica Gilardelli, Chiara Vergani, Rodolfo Gentili, Anne Bonis, Pierre Chanteloup, Sandra Citterio, Enrico A. Chiaradia
    Abstract:

    Quarries are highly heterogeneous and constraining environments because of man-induced disturbances associated with soil erosion and shallow mass movements. Recognizing the importance of plant root systems to overcome stability problems, we investigated the contributions of three different herbaceous species typical of calcareous grasslands, that is, Anthyllis vulneraria, Bromus erectus and Stachys recta, to the stability of the superficial layers of dump deposits at limestone quarries in the Botticino extractive basin (Lombardy, Italy). We analysed (i) the root mechanical properties and root diameter distributions of the selected species and estimated (ii) the lateral root reinforcement they can provide through the Fibre Bundle Model. To assess the effective contribution of a species to the topsoil stabilization, we implemented the results obtained in a stability Model based on the ordinary method of slices. Our results showed that using species such as B.erectus and S.recta with a density of 100 plants per square metre guarantees a better stability of the superficial layers.

N Atsushi - One of the best experts on this subject based on the ideXlab platform.

  • a new surface Model based on a Fibre Bundle of 1 parameter groups
    International Conference on Multimedia and Expo, 2004
    Co-Authors: Jinhui Chao, Jongdae Kim, N Atsushi
    Abstract:

    A new Fibre Bundle surface Model is proposed for 3D object Modeling. This Fibre Bundle Model, consisting of local direct product of a base curve and a Fibre curve, is able to represent arbitrary surfaces. In particular, the Fibre Bundle of 1-parameter groups, i.e. with Fibres as 1-parameter groups are efficient in both synthesis and recognition. Indeed, the 1-parameter groups can be uniquely determined by finite, e.g. six invariants of their Lie algebras. Besides, the surfaces can be quickly generated by elementary functions without numerical integration errors. This Model is also expected to be useful in object-based 3D image coding.

  • ICME - A new surface Model based on a Fibre Bundle of 1-parameter groups
    2004 IEEE International Conference on Multimedia and Expo (ICME) (IEEE Cat. No.04TH8763), 1
    Co-Authors: Jinhui Chao, Jongdae Kim, N Atsushi
    Abstract:

    A new Fibre Bundle surface Model is proposed for 3D object Modeling. This Fibre Bundle Model, consisting of local direct product of a base curve and a Fibre curve, is able to represent arbitrary surfaces. In particular, the Fibre Bundle of 1-parameter groups, i.e. with Fibres as 1-parameter groups are efficient in both synthesis and recognition. Indeed, the 1-parameter groups can be uniquely determined by finite, e.g. six invariants of their Lie algebras. Besides, the surfaces can be quickly generated by elementary functions without numerical integration errors. This Model is also expected to be useful in object-based 3D image coding.

Yang Wang - One of the best experts on this subject based on the ideXlab platform.

  • a modified constitutive equation for unidirectional composites under tensile impact and the dynamic tensile properties of kfrp
    Composites Science and Technology, 2000
    Co-Authors: Yang Wang
    Abstract:

    On the basis of the integral stress/strain curves of unidirectional GRP at a strain rate 300/s and the coated-Fibre-Bundle Model, a modified one-dimensional elastic brittle damage constitutive equation for GRP is proposed by adopting the double Weibull distribution function to describe the strength distribution of the coated glass Fibre instead of a single Weibull function. The modified constitutive equation can characterize integrally the macroscopic tensile mechanical behaviour of GRP under tensile impact. Furthermore, The tensile impact experiments on unidirectional KFRP are performed at strain rates 150/s, 400/s and 1500/s. Experimental results show that the mechanical properties of KFRP are rate dependent. The coated-Fibre-Bundle Model and the modified constitutive equation are extended to KFRP. Consistency between the simulated results and the experimental data confirms that the coated Fibre Bundle Model and the modified constitutive equation are valid.

D. L. Turcotte - One of the best experts on this subject based on the ideXlab platform.

  • Damage and rheology in a Fibre‐Bundle Model
    Geophysical Journal International, 2005
    Co-Authors: Kazuyoshi Nanjo, D. L. Turcotte
    Abstract:

    SUMMARY In this paper, we consider the continuum deformation of the brittle upper continental lithosphere, utilizing the Fibre-Bundle Model. Fibre failure is assumed to be a thermally activated process. We further assume that a failed Fibre is replaced by a new unstressed Fibre. This replacement is analogous to a migration of a dislocation, an earthquake rupture or a microcrack. We derive a non-Newtonian power-law viscous rheology. This is the rheology that has been used to explain the lithospheric deformation in Tibet. We also constrain the parameters in our Model using aftershocks. A major advantage of our upper continental rheology is that it has a strong temperature dependence. We then use this Model to define the strength envelope of the continental lithosphere. Our results suggest that a damage Model is appropriate for the continuum rheology of the upper continental lithosphere.

  • damage and rheology in a Fibre Bundle Model
    Geophysical Journal International, 2005
    Co-Authors: K Z Nanjo, D. L. Turcotte
    Abstract:

    SUMMARY In this paper, we consider the continuum deformation of the brittle upper continental lithosphere, utilizing the Fibre-Bundle Model. Fibre failure is assumed to be a thermally activated process. We further assume that a failed Fibre is replaced by a new unstressed Fibre. This replacement is analogous to a migration of a dislocation, an earthquake rupture or a microcrack. We derive a non-Newtonian power-law viscous rheology. This is the rheology that has been used to explain the lithospheric deformation in Tibet. We also constrain the parameters in our Model using aftershocks. A major advantage of our upper continental rheology is that it has a strong temperature dependence. We then use this Model to define the strength envelope of the continental lithosphere. Our results suggest that a damage Model is appropriate for the continuum rheology of the upper continental lithosphere.