Modelling Multi-Cracking in Thin Films during Constrained Sintering Using Anisotropic Constitutive Law and Material Point Method

The sintering of thin films is widely used for surface coatings and because of its technological importance has generated extensive research interest. During the sintering process, the thin film is constrained by the substrate, which generates considerably high levels of stresses. Crackings are often observed and are considered as one of the major problems of the surface coating technique. This paper has proposed a new numerical method in order to tackle the traditional difficulties in simulating multi-crackings during constrained sintering. Main features of the present method include: (i) the material data is represented by an anisotropic constitutive law, (ii) a new numerical scheme is developed for the crack initialization and growth based on the material point method, (iii) the 3D viscous film shrinkage model is solved by using a dynamic FE scheme, and (iv) the random nature of the initial green body density is represented by statistical variabilities. It is shown that the model proposed by the present paper is capable for the nucleation and propagation of multi-cracks in a straightforward manner. Cracking patterns are shown to be consistent with experimental understandings. The focus of the paper is on the numerical issues and demonstrating the capacity of the model.

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A Material Point Method for Alpine Mass Movements

10.5194/egusphere-egu21-5258 ◽

2021 ◽

Author(s):

Alessandro Cicoira ◽

Lars Blatny ◽

Xingyue Li ◽

Fabrizio Troilo ◽

Robert Kenner ◽

...

Keyword(s):

Climate Change ◽

Initial Conditions ◽

Quantitative Description ◽

Material Point Method ◽

Material Point ◽

Phase Changes ◽

Point Method ◽

Constitutive Law ◽

Gravitational Mass ◽

Mass Movements

Gravitational mass movements pose a threat to the population of numerous mountainous regions around the globe. Climate change affects these processes and their related hazards by influencing their triggering, flow and deposition mechanisms, overall increasing the number of natural catastrophes. Numerical modelling is an essential tool for the analysis and the management of such hazards: it allows the quantitative description of the runout and pressure of rapid mass movements and may contribute to better understand the effects of climate change on their size, frequency, and dynamics. Several depth-averaged models are already operational and commonly applied by practitioners and scientists. Yet, a unified model able to simulate multi-phase cascading events, including their initiation, propagation, entrainment and finally impact on structures is still missing. Hence, more detailed models are &#160;required to advance our understanding of the physics behind gravitational mass movements and ultimately to contribute improving hazard assessment and risk management.Here, we present some preliminary results of the development of a hybrid Eulerian-Lagrangian Material Point Method (MPM) with finite strain elasto-plasticity to simulate in a unified manner: i) permafrost instabilities and failure initiation; ii) rock and ice avalanche dynamics; iii) solid-fluid interaction and phase transition from rock avalanches to debris-flows. In order to simulate the mechanical behaviour of rock and ice, we propose a Drucker-Prager softening constitutive law accounting for cohesion, internal and residual friction. We calibrate this constitutive law on the basis of state of the art laboratory experiments. The model is applied to synthetic slope geometries to evaluate their stability and investigate subsequent rock fragmentation processes. At a larger scale, dynamics simulations are compared against observations of full-scale process chains. In particular, we implement the two real-scale cases of the rock-avalanche from the Piz Cengalo (CH) and ice- and snow-avalanche from the Grandes Jorasses (IT). The 3D implementation of the model allows to accurately reproduce the initial conditions of an event and complex phenomena such as reported ballistic trajectories non adherent to the ground. Secondary releases due to the mass flow (such as snow or glacier-ice entertainment) and phase changes can be simulated realistically. We test the potential of the model in a broad range of settings and highlight the major gaps to be filled in the near future.

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The material point method for simulating dense snow avalanches over complex real terrain

10.5194/egusphere-egu21-6045 ◽

2021 ◽

Author(s):

Xingyue Li ◽

Betty Sovilla ◽

Chenfanfu Jiang ◽

Johan Gaume

Keyword(s):

Material Point Method ◽

Granular Flows ◽

Material Point ◽

Full Scale ◽

Point Method ◽

Constitutive Law ◽

Snow Avalanches ◽

Failure Patterns ◽

Snow Properties ◽

Modified Cam Clay

Various dynamics models can reproduce the motion of avalanches from release to deposition. These models often simulate a conceptual avalanche, adopt depth-averaged approaches and do not resolve variations along flow depth direction, and thus have clear limitations. This study presents three-dimensional, full-scale modeling of dense snow avalanches performed using the complex real terrain of the Vall&#233;e de la Sionne avalanche test site in Switzerland. We use the material point method (MPM) and a large-strain elastoplastic constitutive law for snow based on a Modified Cam Clay model. In our simulations, various and transient avalanche flow regimes are simulated by setting distinct snow properties. Snow avalanches are investigated from release to deposition. Detailed simulation results include the initial failure patterns, the mechanical behavior during the flow, and the characteristics of the final avalanche deposits. More specifically in the release zone, we can observe brittle and ductile fractures depending on the defined snow properties. During the flow phase, we monitor the temporal and spatial variations of snow density in the avalanche. In particular, cohesionless granular flows, cohesive granular flows, and plug flows are associated with snow fracture, compaction, and expansion. Finally, we can observe the structure of the avalanche deposit surfaces which show distinguishable differences in terms of smoothness, granulation, and compacting shear planes. This new model can offer a quantitative analysis for studying avalanches in different regimes and provide a powerful tool for exploring the dynamics of full-scale avalanches on complex real terrain, with high physical detail.

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A Hybrid Material Point Method for Frictional Contact with Diverse Materials

Proceedings of the ACM on Computer Graphics and Interactive Techniques ◽

10.1145/3340258 ◽

2019 ◽

Vol 2 (2) ◽

pp. 1-24 ◽

Cited By ~ 7

Author(s):

Xuchen Han ◽

Theodore F. Gast ◽

Qi Guo ◽

Stephanie Wang ◽

Chenfanfu Jiang ◽

...

Keyword(s):

Hybrid Material ◽

Frictional Contact ◽

Material Point Method ◽

Material Point ◽

Point Method

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Three-dimensional face stability analysis of shallow tunnels using numerical limit analysis and material point method

Tunnelling and Underground Space Technology ◽

10.1016/j.tust.2021.103904 ◽

2021 ◽

Vol 112 ◽

pp. 103904

Author(s):

Fabricio Fernández ◽

Jhonatan E.G. Rojas ◽

Eurípedes A. Vargas ◽

Raquel Q. Velloso ◽

Daniel Dias

Keyword(s):

Stability Analysis ◽

Limit Analysis ◽

Three Dimensional ◽

Material Point Method ◽

Material Point ◽

Point Method ◽

Face Stability ◽

Shallow Tunnels ◽

Dimensional Face

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A moving least squares material point method with displacement discontinuity and two-way rigid body coupling

ACM Transactions on Graphics ◽

10.1145/3197517.3201293 ◽

2018 ◽

Vol 37 (4) ◽

pp. 1-14 ◽

Cited By ~ 31

Author(s):

Yuanming Hu ◽

Yu Fang ◽

Ziheng Ge ◽

Ziyin Qu ◽

Yixin Zhu ◽

...

Keyword(s):

Rigid Body ◽

Least Squares ◽

Material Point Method ◽

Material Point ◽

Point Method ◽

Displacement Discontinuity ◽

Moving Least Squares

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Dam Breach Simulation with the Material Point Method

Computation ◽

10.3390/computation9020008 ◽

2021 ◽

Vol 9 (2) ◽

pp. 8

Author(s):

Chendi Cao ◽

Mitchell Neilsen

Keyword(s):

Material Point Method ◽

Mixture Theory ◽

Material Point ◽

Point Method ◽

Internal Erosion ◽

Dam Breach ◽

New Model ◽

Hencky Strain ◽

The Impact ◽

Soil And Water

Dam embankment breaches caused by overtopping or internal erosion can impact both life and property downstream. It is important to accurately predict the amount of erosion, peak discharge, and the resulting downstream flow. This paper presents a new model based on the material point method to simulate soil and water interaction and predict failure rate parameters. The model assumes that the dam consists of a homogeneous embankment constructed with cohesive soil, and water inflow is defined by a hydrograph using other readily available reach routing software. The model uses continuum mixture theory to describe each phase where each species individually obeys the conservation of mass and momentum. A two-grid material point method is used to discretize the governing equations. The Drucker–Prager plastic flow model, combined with a Hencky strain-based hyperelasticity model, is used to compute soil stress. Water is modeled as a weakly compressible fluid. Analysis of the model demonstrates the efficacy of our approach for existing examples of overtopping dam breach, dam failures, and collisions. Simulation results from our model are compared with a physical-based breach model, WinDAM C. The new model can capture water and soil interaction at a finer granularity than WinDAM C. The new model gradually removes the granular material during the breach process. The impact of material properties on the dam breach process is also analyzed.

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