Probabilistic approach in modelling dynamic fracture problems

2020 ◽  
pp. 095440622093911
Author(s):  
Sergey V Pashkov ◽  
Sergey A Zelepugin
Keyword(s):  
Dynamic Fracture ◽  
Probabilistic Approach ◽  
Multilevel Modelling ◽  
Quantitative Agreement ◽  
Numerical Results ◽  
Structural Defects ◽  
Material Structure ◽  
Additional Parameter ◽  
Distribution Law ◽  
Computational Mesh

The paper represents a probabilistic approach to the finite element modelling of dynamic fracture problems. It is proposed to model internal structural defects and inhomogeneities using the spatial distribution of strength characteristics according to the normal distribution law. The probabilistic approach to modelling dynamic fracture is provided by the introduction of one additional parameter – the dispersion in the distribution of strength material properties. This approach provides the probabilistic nature to the initiation and development of cracks in the material at any scale level: macro, meso and micro level. There are no restrictions on the size of computational mesh and elements, the fracture criterion and the material models to apply this approach. The probabilistic approach is also applicable to multilevel modelling using the appropriate distribution of inhomogeneities. This approach does not require a detailed study of the material structure, which enhances the predictive nature of computations. The numerical results of exploding cylinder tests and the penetration of thin targets by a projectile are presented. Numerical results are in good qualitative and quantitative agreement with experimental data.

scholarly journals A probabilistic approach to modeling collisions with thin barriers

2019 ◽  
Vol 221 ◽  
pp. 01039 ◽  
Author(s):  
Sergey Pashkov
Keyword(s):  
Experimental Data ◽  
Probabilistic Approach ◽  
Material Model ◽  
Strength Properties ◽  
Strength Characteristics ◽  
Additional Parameter ◽  
Computational Domain ◽  
Distribution Law ◽  
Theoretical Concepts ◽  
Probabilistic Character

In many fracture problems, fragmentation is essentially a probabilistic process, which is determined by the stochastic nature of the distribution of inhomogeneities of the internal structure of material. The probabilistic approach is described, which allows us to model structural heterogeneities of the material in a simple form, practically without any complication of the model and additional experiments. Using experimental data and numerical simulation results, it is shown that the introduction of only one additional parameter (dispersion of the strength properties distribution) into the material model makes it possible to give a probabilistic character to the crack formation process at any scale level, which corresponds to theoretical concepts and experimental data. Distribution of materials strength characteristics (according to the selected distribution law) in the cells of the computational domain is used for initial heterogeneities and materials structure defects modeling. It is shown that the number and size of the “petals” at the penetration of thin barriers depend of the speed of the projectile and the strength characteristics of the barrier.

Controlled experiments and finite element simulations with the Swiss plate geophone bedload monitoring system: particle size identification and transport mode

2021 ◽  
Author(s):  
Zheng Chen ◽  
Siming He ◽  
Tobias Nicollier ◽  
Lorenz Ammann ◽  
Alexandre Badoux ◽  
...  
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Finite Element ◽  
Quantitative Agreement ◽  
Bedload Transport ◽  
Material Structure ◽  
Flume Experiments ◽  
Fem Simulations ◽  
Transport Mode ◽  
Signal Response

<p>The Swiss plate geophone (SPG) system is an indirect bedload transport monitoring device that records the acoustic signals generated by bedload particle impacts, with the goal to derive the bedload flux and grain size distribution. Particle drop experiments with quartz spheres in quiescent water in a flume setting were performed to investigate the dynamic signal response of the SPG system impacted by particle-like objects varying in size and impact location. Systematic flume experiments with natural bedload particles in flowing water were conducted to study the effects of impact angle and transport mode (saltating, rolling and sliding) on the SPG signals. For each impact caused by a single particle, the number of signal impulses, the amplitude, the positive area surrounded by the signal envelope, and the centroid frequency were extracted from the raw geophone monitoring data. The finite element method (FEM) was used to construct a virtual model of the SPG system and to determine the propagation characteristics of the numerical stress wave in the material structure. The experimental and numerical results showed a qualitative and partially quantitative agreement in the changes of the signal impulses, the amplitude, and the envelope area with increasing colliding sphere size. The centroid frequencies of the SPG vibrations showed qualitatively similar dependencies with increasing particle size as some field measurements for the coarser part of the investigated range of impact sizes. The effects of variable particle impact velocities and impact locations on the geophone plate were also investigated by drop experiments and compared to FEM simulations. In addition, the signal response for different bedload transport modes and varying impact angles were explored. In summary, the FEM simulations contribute to the understanding of the signal response of the SPG system and the findings in this study may eventually result in improving the bedload grain size classification and transport mode recognition.</p>

Selection of a Constitutive Model Used for Prediction of Behaviour of Ring Material Expanded by Pulse Electromagnetic Field

2009 ◽  
Vol 147-149 ◽  
pp. 444-449
Author(s):  
Robert Panowicz ◽  
Jacek Janiszewski
Keyword(s):  
Constitutive Model ◽  
Dynamic Behaviour ◽  
Constitutive Models ◽  
Quantitative Agreement ◽  
Numerical Results ◽  
Ring Test ◽  
Pulse Electromagnetic Field ◽  
Analogous Data ◽  
Ring Material ◽  
Selection Of

Selection of a constitutive model from commonly used ones, which in the best way describes dynamic behaviour of material during electromagnetic expanding ring test, is our primary goal in this work. Five more popular constitutive models are examined, i.e., Johnson-Cook, Steinberg-Guinan, Zerilli-Armstrong, MTS, and Preston-Tonks-Wallace model. As a criterion of the selection, qualitative/quantitative agreement of the numerical results with analogous data obtained from experiment presented in the work was taken [1]. It was found that the numerical results obtained by using Steinberg-Guinan or Preston-Tonks-Wallace model gave the best agreement with experimental data.

scholarly journals A note on the propagation of plane waves in elastic and plastic solids

1968 ◽  
Vol 8 (2) ◽  
pp. 231-237 ◽  
Author(s):  
G. J. Cooper ◽  
J. W. Craggs
Keyword(s):  
Plane Waves ◽  
Quantitative Agreement ◽  
Numerical Results ◽  
Experimental Results ◽  
Strain Effects

AbstractSome further numerical results are obtained for plane waves propagated into elastic and plastic solids. Quantitative agreement with experimental results indicates that rate of strain effects are not significant.

scholarly journals Capillary bridges between a plane and a cylindrical wall

2015 ◽  
Vol 773 ◽  
Author(s):  
Etienne Reyssat
Keyword(s):  
Numerical Solution ◽  
Quantitative Agreement ◽  
Horizontal Cylinder ◽  
Numerical Results ◽  
Planar Boundary ◽  
Cylindrical Wall ◽  
Good Quantitative Agreement ◽  
Capillary Bridges

We report experimental, theoretical and numerical results on the shapes of liquid menisci connecting a planar boundary and the surface of a horizontal cylinder placed above. The gradient of confinement traps the wetting drops in the most confined regions, which promotes their elongation along the line of smallest gap between the walls. The experimental shapes of these stretched capillary bridges are shown to be in good quantitative agreement with the numerical solution of the equation describing their contour. In particular, we show that the measured shapes are better described when taking into account the correction resulting from the coupling of in-plane and transverse interfacial curvatures calculated by Park & Homsy (J. Fluid Mech., vol. 139, 1984, pp. 291–308) over thirty years ago.

Hybrid Finite-Discrete Element Modelling of Dynamic Fracture of Rocks with Various Geometries

2012 ◽  
Vol 256-259 ◽  
pp. 183-186 ◽  
Author(s):  
Hong Yuan Liu
Keyword(s):  
Discrete Element Method ◽  
Dynamic Fracture ◽  
Discrete Element ◽  
Numerical Results ◽  
Discrete Element Modelling ◽  
Rigid Surface ◽  
Element Modelling ◽  
Impact Area ◽  
The Impact ◽  
Rock Specimens

The hybrid finite-discrete element method Y-2D/3D IDE is applied to model the dynamic fracture of rock specimens with various geometries during impacting a fixed rigid surface. It is found that the modelled primary fractures are highly dependent on the rock geometry determining the weakest plane for a given impact, which agrees well with others' experimental and SPH numerical results. Compared with others' SPH results, Y-2D/3D IDE better simulates the actinomorphic pattern of primary fractures around the impact area and the secondary & tertiary fractures observed in the dynamic fracture experiments. It is concluded that the proposed Y-2D/3D IDE is a valuable tool to model rock dynamic fracture compared with FEM and DEM.

Shelfbreak upwelling induced by alongshore currents: analytical and numerical results

2011 ◽  
Vol 686 ◽  
pp. 239-249 ◽  
Author(s):  
Robert N. Miller ◽  
Ricardo P. Matano ◽  
Elbio D. Palma
Keyword(s):  
Shallow Water Equations ◽  
Numerical Experiments ◽  
Coastal Upwelling ◽  
Quantitative Agreement ◽  
Numerical Results ◽  
Ekman Transport ◽  
Ecological Features ◽  
Coastal Trapped Waves ◽  
Steady Solutions ◽  
Arrested Topographic Wave

AbstractAlongshore flow in the direction of propagation of coastal trapped waves can result in upwelling at the shelfbreak. The intensity of this upwelling can be comparable in magnitude to wind-driven coastal upwelling, with its associated ecological features. Recent numerical experiments by Matano & Palma indicate that this upwelling results from convergence of Ekman transport at the shelfbreak. The mechanism for this phenomenon can be understood in terms of steady solutions to the shallow water equations in the presence of Coriolis force and bottom drag. Matano & Palma interpreted their numerical results in terms of the arrested topographic wave, but did not present direct comparisons. Here we present a family of analytical solutions to the equations of the arrested topographic wave that shows striking quantitative agreement with earlier numerical results.

Numerical Study of the Unsteady Blade Row Interaction in a Three-Stage Low Pressure Turbine

2003 ◽  
Author(s):  
Christian Nayeri ◽  
Wolfgang Ho¨hn
Keyword(s):  
Numerical Study ◽  
Time Integration ◽  
Quantitative Agreement ◽  
Navier Stokes ◽  
Implicit Time ◽  
Surface Pressure Distribution ◽  
Computational Mesh ◽  
Transition Models ◽  
Underlying Mechanisms ◽  
Turbulence Parameters

The focus of this paper is on the one hand the quantitative optimization of the unsteady numerical simulations compared to experiments, and on the other hand to gain a better insight into the underlying mechanisms when an upstream wake of a stator interacts with the flow-field of the next stator. This was achieved by optimizing the numerical turbulence parameters used in the turbulence and transition models. Using steady calculations an optimal initial solution for the unsteady calculation was found. Also, the computational mesh was refined. For the numerical computations a time accurate Reynolds averaged Navier-Stokes solver is applied. Turbulence is modeled using the Spalart-Allmaras one equation turbulence model. The integration of the governing equations in time is performed by an implicit time integration for the steady calculations, and by an implicit dual time stepping scheme for the unsteady calculations. At the inlet and outlet reflecting or non-reflecting boundary conditions are used. The quasi 3D calculations are conducted on a stream surface around midspan allowing a varying stream tube thickness. The results show that by adjusting the turbulence parameters in the turbulence and transition models, a better qualitative and quantitative agreement between experiments and numerical results can be achieved. Steady and unsteady quantities are shown, e.g. the surface pressure distribution and the wall shear stress. The unsteady simulations of two different azimuthal positions of the first and third stator reveal different evolutions of the boundary layers of the second and third stators due to the influence of the wake of the upstream stators. These differences are better captured through the above mentioned improvements, i.e. reduction of sheared cells in the computational mesh and optimization of turbulence and transition parameters in the allowable range of the models.

scholarly journals Effects of Ion Beam Etching on the Nanoscale Damage Precursor Evolution of Fused Silica

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1294
Author(s):  
Yaoyu Zhong ◽  
Yifan Dai ◽  
Feng Shi ◽  
Ci Song ◽  
Ye Tian ◽  
...  
Keyword(s):  
Silica Surface ◽  
Ion Beam ◽  
Damage Threshold ◽  
Fused Silica ◽  
Structural Defects ◽  
Laser Damage ◽  
Material Structure ◽  
Ion Beam Etching ◽  
Damage Resistance ◽  
Laser Induced Damage

Nanoscale laser damage precursors generated from fabrication have emerged as a new bottleneck that limits the laser damage resistance improvement of fused silica optics. In this paper, ion beam etching (IBE) technology is performed to investigate the evolutions of some nanoscale damage precursors (such as contamination and chemical structural defects) in different ion beam etched depths. Surface material structure analyses and laser damage resistance measurements are conducted. The results reveal that IBE has an evident cleaning effect on surfaces. Impurity contamination beneath the polishing redeposition layer can be mitigated through IBE. Chemical structural defects can be significantly reduced, and surface densification is weakened after IBE without damaging the precision of the fused silica surface. The photothermal absorption on the fused silica surface can be decreased by 41.2%, and the laser-induced damage threshold can be raised by 15.2% after IBE at 250 nm. This work serves as an important reference for characterizing nanoscale damage precursors and using IBE technology to increase the laser damage resistance of fused silica optics.

scholarly journals NUMERICAL ANALYSIS OF THE WAVE PROPAGATION IN A COMPOSITE MEDIUM

2006 ◽  
Vol 11 (2) ◽  
pp. 162-172 ◽  
Author(s):  
P. Katauskis ◽  
V. Skakauskas
Keyword(s):  
Wave Propagation ◽  
Numerical Analysis ◽  
Free Boundary ◽  
Diffraction Problem ◽  
Numerical Results ◽  
Composite Medium ◽  
Material Structure ◽  
Propagation Process ◽  
Waves Interaction

We consider the wave propagation process in a 2‐dimensional material structure composed of random oriented orthotropic crystals and analyse numerical results for the diffraction problem and the problem of waves interaction with a free boundary.

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