A new  effective rate  dependent damage model for dynamic tensile failure of concrete

Pereira, L.F. Magalhaes; Weerheijm, J.; Sluys, L.J.

doi:10.1016/j.engfracmech.2017.03.048

Cited by 36 publications

(20 citation statements)

References 35 publications

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“…A natural regularization technique is to account for the rate dependent nature of damage (Geers et al, 1994 ). Although we do not explicitly investigate regularization here, the inherent rate dependence of our axonal damage model potentially regularizes the simulation at no additional cost (Pereira et al, 2017 ).…”

Section: Discussionmentioning

confidence: 99%

Physical Biology of Axonal Damage

Rooij

Kuhl

2018

Front. Cell. Neurosci.

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Excessive physical impacts to the head have direct implications on the structural integrity at the axonal level. Increasing evidence suggests that tau, an intrinsically disordered protein that stabilizes axonal microtubules, plays a critical role in the physical biology of axonal injury. However, the precise mechanisms of axonal damage remain incompletely understood. Here we propose a biophysical model of the axon to correlate the dynamic behavior of individual tau proteins under external physical forces to the evolution of axonal damage. To propagate damage across the scales, we adopt a consistent three-step strategy: First, we characterize the axonal response to external stretches and stretch rates for varying tau crosslink bond strengths using a discrete axonal damage model. Then, for each combination of stretch rates and bond strengths, we average the axonal force-stretch response of n = 10 discrete simulations, from which we derive and calibrate a homogenized constitutive model. Finally, we embed this homogenized model into a continuum axonal damage model of [1-d]-type in which d is a scalar damage parameter that is driven by the axonal stretch and stretch rate. We demonstrate that axonal damage emerges naturally from the interplay of physical forces and biological crosslinking. Our study reveals an emergent feature of the crosslink dynamics: With increasing loading rate, the axonal failure stretch increases, but axonal damage evolves earlier in time. For a wide range of physical stretch rates, from 0.1 to 10 /s, and biological bond strengths, from 1 to 100 pN, our model predicts a relatively narrow window of critical damage stretch thresholds, from 1.01 to 1.30, which agrees well with experimental observations. Our biophysical damage model can help explain the development and progression of axonal damage across the scales and will provide useful guidelines to identify critical damage level thresholds in response to excessive physical forces.

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Section: Discussionmentioning

confidence: 99%

Physical Biology of Axonal Damage

Rooij

Kuhl

2018

Front. Cell. Neurosci.

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“…In addition, the existence of a maximum damage evolution rate results in an increase in both the maximum attainable stress and toughness as the loading rate increases. This loading rate dependency of strength and toughness is experimentally verified; see for example [24,34]. Finally, the damage evolution law is an Ordinary Differential Equation in time.…”

Section: Introductionmentioning

confidence: 56%

“…In gradient-based models, this is achieved by adding higher order derivatives of the damage or strain fields to the damage evolution equation [21,22]. In nonlocal approaches, strain or damage field employed in a local damage formulation, is in turn computed over a neighborhood of finite size [23,24]. Finally, time-relaxed damage formulations possess an internal time parameter which through its interaction with elastic wave speeds introduce a finite length scale for the damage model in transient settings [25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

A Stochastic Bulk Damage Model Based on Mohr-Coulomb Failure Criterion for Dynamic Rock Fracture

2019

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We present a stochastic bulk damage model for rock fracture. The decomposition of strain or stress tensor to its negative and positive parts is often used to drive damage and evaluate the effective stress tensor. However, they typically fail to correctly model rock fracture in compression. We propose a damage force model based on the Mohr-Coulomb failure criterion and an effective stress relation that remedy this problem. An evolution equation specifies the rate at which damage tends to its quasi-static limit. The relaxation time of the model introduces an intrinsic length scale for dynamic fracture and addresses the mesh sensitivity problem of earlier damage models. The ordinary differential form of the damage equation makes this remedy quite simple and enables capturing the loading rate sensitivity of strain-stress response. The asynchronous Spacetime Discontinuous Galerkin (aSDG) method is used for macroscopic simulations. To study the effect of rock inhomogeneity, the Karhunen-Loeve method is used to realize random fields for rock cohesion. It is shown that inhomogeneity greatly differentiates fracture patterns from those of a homogeneous rock, including the location of zones with maximum damage. Moreover, as the correlation length of the random field decreases, fracture patterns resemble angled-cracks observed in compressive rock fracture.

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“…The rate of enhancement of the strength in compression can be quantitatively addressed in dynamics using rate dependent functions. They are usually implemented into numerical models to simulate cementitious materials subjected to highly dynamic loadings [12,15]. The most widely used reference to design the compressive strength of normal concrete (f b ≤ 50 MPa) in dynamics is the CEB-FIB model [14].…”

Section: Analysis Of Data In Strengthmentioning

confidence: 99%

Dynamic characterization of adobe in compression: the effect of fibre fraction in soil matrix

Piani¹,

Weerheijm²,

Peroni³

et al. 2019

Proceedings of the 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures

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Adobe is one of the most ancient forms of masonry. Adobe bricks are sundried mixtures of clay, silt, sand and natural fibres locally available joined together using mud mortar. Adobe structures are largely spread in areas of the world prone to earthquakes or involved in military conflicts. Unfortunately, almost no literature concerns the dynamic assessment of soil-based masonry components. From earlier research, it was derived that the mechanical behaviour of adobe in statics fits in the class of quasi brittle materials. Its resemblance with cementitious materials concerns the main failure modes and the constitutive models in compression. This study deals with the experimental characterization of adobe components response in dynamics. It is aimed to study and quantify the rate sensitivity of adobe material from bricks at a wide range of strain rates, from statics up to impact conditions. In particular, the influence of fiber reinforcement in the mixture on the mechanical behaviour of the material has been addressed. Adobe bricks are commonly mixed using organic content locally available in the field, from straw to chopped wood. Fibres are added to prevent shrinkage cracks during the air drying process. In modern materials such as concrete, inclusion of artificial fibres is originally meant to enhance the mechanical performance of the material, benefiting from the selective properties of reinforcement and binder. An experimental campaign was carried out in a collaboration between Delft University of Technology, Dutch Ministry of Defence, TNO and the Joint Research Centre (JRC) of the European Commission. Two types of bricks were tested. They both had the same soil composition in terms of mineralogical family and soil elements proportions but only one was mixed using straw and wood. Cylindrical samples were subjected to compression tests at different rates of loadings in compression: low (˙ 1 = 3 10 −4 s −1), intermediate (˙ 2 = 3 s −1) and high (˙ 3 = 120 s −1). High strain rate tests were performed using the split Hopkinson bar of the Elsa-HopLab (JRC). For each test, high resolution videos registered the failure process and force-displacement plots were

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A new effective rate dependent damage model for dynamic tensile failure of concrete

Cited by 36 publications

References 35 publications

Physical Biology of Axonal Damage

Physical Biology of Axonal Damage

A Stochastic Bulk Damage Model Based on Mohr-Coulomb Failure Criterion for Dynamic Rock Fracture

Dynamic characterization of adobe in compression: the effect of fibre fraction in soil matrix

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