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A discrete-continuous model of coupled plasticity and fracture

JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2025年 197卷

作者： Li, Zhangtao Zhuang, Zhuo Li, Zhijie Wang, Tao Liu, Zhanli Cui, Yinan Tsinghua Univ Sch Aerosp Engn Appl Mech Lab Beijing 100084 Peoples R China Beijing Inst Technol State Key Lab Explos Sci & Technol Beijing 100081 Peoples R China

Understanding the interplay between plasticity and fracture is the basis for the prediction and design of materials and structures, which is controlled by the concurrent dynamics of discrete dislocations and cracks. However, till now, how to directly capture the co-evolution of a threedimensional (3D) discrete dislocation network and arbitrary crack remains challenging due to their intrinsic complex interactions and different modeling frameworks. To overcome these issues, we proposed a discrete-continuous coupled plasticity-fracture model in a thermodynamic consistent framework, which can not only reproduce the discrete crack-dislocation interdependence dynamics, but also demonstrate capability and flexibility in handling complex boundary value problems by simultaneously considering the co-evolution of continuous plasticity and fracture field. This model offers many advantages, including accurately capturing the image force of the crack surface on dislocation, the shielding and anti-shielding effect of 3D dislocation on crack propagation, as well as reproducing arbitrary crack propagation without reliance on a predefined crack path. As a representative example, a notched microbeam bending problem is studied and compared with experiments, yielding new insights regarding the 3D co-evolution of collective defects and their influence on mechanical response.

关键词： Plasticity Fracture discrete-continuous model Dislocation dynamics

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Identifying the relationship between intention to use flat-rate public transport and trip frequency by a discrete-continuous model

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PUBLIC TRANSPORT 2023年第2期16卷 485-504页

作者： Nishiuchi, Hiroaki Nishimura, Kohei Ngoc, An Minh Dias, Charitha Kochi Univ Technol Sch Syst Engn 185 Tosayamadacho Miyanokuchi Kami City Kochi 7828502 Japan Chiyoda Engn Consultants Co Ltd 2-6 KandasudachoChiyoda Ku Tokyo Japan Qatar Transportat & Traff Safety Ctr Coll Engn Dept Civil & Architectural Engn POB 2713 Doha Qatar

Public transport fare is a central feature of transit operations and is a key indicator to reflect transport demand. Yet, relatively little is known about how fare influences on ridership dynamics, including for which types of fare incentives, who accepts it, and how passengers' travel patterns are changed. This information is particularly important considering concerns about a decline of public transport ridership due to the aging population and pandemic. In this paper, we employ a flat-rate public transport fare as an urgent measure to revive the demand for public transport in rural areas of Japan. A discrete-continuous model is applied to describe the relationship between the intention to use flat-rate public transport and trip frequency. A stated preference survey was conducted with citizens living near the station and bus stops in Kochi Prefecture. This study contributes to the literature by providing firsthand insights about how demand for flat-rate public transport fares is formed and how different policy implications can be made accordingly. The results indicate that a flat-rate fare has proven effective in increasing the frequency of use of public transportation, which will lead to the revitalization of the public transport system. The outcome of this study is anticipated to inform and equip city authorities and operators with advanced knowledge about the benefits of flat-rate fares which can help to change fare policies in the near future.

关键词： Public transport Flat-rate public transport fare discrete-continuous model Trip frequency

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Time Discretization in Pedestrian Dynamics Simulations by discrete-continuous model 14th

Time Discretization in Pedestrian Dynamics Simulations by Di...

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14th International Conference on Cellular Automata for Research and Industry (ACRI)

作者： Kirik, Ekaterina Vitova, Tat'yana Malyshev, Andrey Russian Acad Sci Inst Computat Modelling Siberian Branch Akademgorodok 50-44 Krasnoyarsk 660036 Russia

ISBN: (纸本)9783030694791;9783030694807

A discretization of time in computer simulation of pedestrian movement is considered. Time step is very influencing on computational performance. But not only quick calculations is a criterion. The other one is a confidence to a simulation result. From both aspects, the discrete-continuous model SigmaEva is considered in the paper. It is shown that low and high time steps are not reasonable.

关键词： Pedestrian simulation discrete-continuous model Fundamental diagram Flow rate Time discretization

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An extended 3D discrete-continuous model and its application on single- and bi-crystal micropillars

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modelLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING 2017年第3期25卷 035001-035001页

作者： Huang, Minsheng Liang, Shuang Li, Zhenhuan Huazhong Univ Sci & Technol Dept Mech Wuhan 430074 Peoples R China Hubei Key Lab Engn Struct Anal & Safety Assessmen Luoyu Rd 1037 Wuhan 430074 Peoples R China

A 3D discrete-continuous model (3D DCM), which couples the 3D discrete dislocation dynamics (3D DDD) and finite element method (FEM), is extended in this study. New schemes for two key information transfers between DDD and FEM, i.e. plastic-strain distribution from DDD to FEM and stress transfer from FEM to DDD, are suggested. The plastic strain induced by moving dislocation segments is distributed to an elementary spheroid (ellipsoid or sphere) via a specific new distribution function. The influence of various interfaces (such as free surfaces and grain boundaries (GBs)) on the plastic-strain distribution is specially considered. By these treatments, the deformation fields can be solved accurately even for dislocations on slip planes severely inclined to the FE mesh, with no spurious stress concentration points produced. In addition, a stress correction by singular and non-singular theoretical solutions within a cut-off sphere is introduced to calculate the stress on the dislocations accurately. By these schemes, the present DCM becomes less sensitive to the FE mesh and more numerically efficient, which can also consider the interaction between neighboring dislocations appropriately even though they reside in the same FE mesh. Furthermore, the present DCM has been employed to model the compression of single-crystal and bi-crystal micropillars with rigid and dislocation-absorbed GBs. The influence of internal GB on the jerky stress-strain response and deformation mode is studied in detail to shed more light on these important micro-plastic problems.

关键词： discrete-continuous model micropillar discrete dislocation dynamics finite element method grain boundary

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Investigations of annealing hardening in Au micropillar based on a modified discrete-continuous model

Investigations of annealing hardening in Au micropillar base...

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北京力学会第二十三届学术年会

作者： Fengxian Liu Zhan-li Liu Peng Lin Zhuo Zhuang Applied Mechanics Lab. School of Aerospace Engineering Tsinghua University

In contrast to the typical behavior at macro level, recent studies at sub-micro scale have shown that metals may harden rather than soften during high temperature annealing. In the present work, a modified three-dimensional discrete-continuous mode(DCM) is proposed to address the limitations of the local model, in which the vacancy diffusion equation is solved by the FEM. Based on this DCM model, the intrinsic mechanism of annealing hardening at sub micro scale and detailed evolution of defects during the annealing are investigated. Numerical simulation results shows that the hardening is caused by the decrease of dislocation density, which can be ascribed to two main aspects:(i) The climb of dislocation during the high temperature annealing promotes the annihilation of the dislocations, leading to a decrease in dislocation density.(ii) The jogs, nucleated during annealing due to the high temperature climb, have very weak mobility and act as obstacles to the dislocation glide motion, leading to mobile dislocation starvation and resulting in a higher flow strength level.

关键词： annealing hardening dislocation climb discrete-continuous model jogs

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An analysis on travel party composition and expenditure: a discrete-continuous model

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ANNALS OF TOURISM RESEARCH 2016年 56卷 48-64页

作者： Rashidi, Taha H. Koo, Tay T. R. Univ New S Wales Sydney NSW 2052 Australia

While the interrelated nature of tourism decisions is well recognised, there is a significant gap between conceptual understanding and modelling practice. Empirically, the interrelations between tourism decisions are often not tested and quantified because the research technique does not embody the capacity to test for the correlations between these decisions. This research aims to empirically investigate these interrelationships by using a multinomial discrete-continuous model estimated with trip expenditure hazard-based function. In the context of domestic tourism in Australia, this study adds to the emerging body of research by finding quantifiable evidence that travel party choices, travel mode choices, and expenditure decisions are interrelated, contributing towards developing a more nuanced understanding of these decisions. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： discrete-continuous model Hazard function Survival analysis Trip expenditure Travel party composition

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Quantitative investigations on dislocation based discrete-continuous model of crystal plasticity at submicron scale

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INTERNATIONAL JOURNAL OF PLASTICITY 2015年 69卷 54-72页

作者： Cui, Yinan Liu, Zhanli Zhuang, Zhuo Tsinghua Univ Sch Aerosp Dept Engn Mech Appl Mech Lab Beijing 100084 Peoples R China

Although the multi-scale discrete-continuous model (DCM) which couples discrete dislocation dynamics (DDD) and finite element method (FEM) to study crystal plasticity at submicron scale has been proposed for many years, some key issues are still not well addressed yet. First, a new regularization method with slip plane dependent regularization parameter is proposed in this paper to localize the discrete plastic strain to continuum material points and shows excellent accuracy compared with previous studies. Second, it is often thought of that DCM cannot accurately calculate the so called 'image force' acting on the dislocation near free surface. This study argues that the image force can be calculated accurately in the hybrid DCM in which the interpolated stress is used in the computation. The reproduction of deformed crystal configuration during finite deformation is another critical issue in DCM, especially for considering the rotation of slip system. The deformation field transfer between DDD and FEM, and the corresponding treatment of surface dislocations and slip system rotation are proposed to well capture the localized deformation. As an application, the dislocation behavior and stress field in heteroepitaxial films with thin/thick substrates are successfully investigated by the improved DCM. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Dislocation Image force Finite deformation Submicron crystal plasticity discrete-continuous model

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modelling crystal plasticity by 3D dislocation dynamics and the finite element method: The discrete-continuous model revisited

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2014年第1期63卷 491-505页

作者： Vattre, A. Devincre, B. Feyel, F. Gatti, R. Groh, S. Jamond, O. Roos, A. ONERA French Aerosp Lab F-92322 Chatillon France CNRS ONERA LEM F-92322 Chatillon France

A unified model coupling 3D dislocation dynamics (DD) simulations with the finite element (FE) method is revisited. The so-called discrete-continuous model (DCM) aims to predict plastic flow at the (sub-)micron length scale of materials with complex boundary conditions. The evolution of the dislocation microstructure and the short-range dislocation-dislocation interactions are calculated with a DD code. The long-range mechanical fields due to the dislocations are calculated by a FE code, taking into account the boundary conditions. The coupling procedure is based on eigenstrain theory, and the precise manner in which the plastic slip, i.e. the dislocation glide as calculated by the DD code, is transferred to the integration points of the FE mesh is described in full detail. Several test cases are presented, and the DCM is applied to plastic flow in a single-crystal Nickel-based superalloy. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Dislocation dynamics Finite element Dislocation theory Crystal plasticity discrete-continuous model

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Location choice of residential housing supply: An application of the multiple discrete-continuous extreme value (MDCEV) model

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JOURNAL OF CHOICE modelLING 2025年 54卷

作者： Zhang, Yu Miller, Eric J. Univ Toronto Dept Civil & Mineral Engn Toronto ON Canada

The supply location of residential housing is the result of multiple, simultaneous decisions by housing developers. This choice situation can be characterized by the discretionary choice of locations for the housing projects and the amount of housing units to be built at the given locations. Within this context, the modelling of residential housing supply locations, or the allocation of predicted housing supply over space, is a discrete-continuous process. In this paper, we apply a multiple discrete continuous extreme value (MDCEV) model to simultaneously model the location choice and amount of housing supply. The empirical study is conducted in the city of Toronto with a pooled model, and four separated models for each structure type. The prediction results indicate reasonable fits. The developed model can be used to generate housing supply at a given period over space in an urban microsimulation system and serves as a valuable tool for policymakers, urban planners, and researchers in the field of housing supply and urban systems.

关键词： Location choice modelling discrete-continuous model Housing supply Residential development

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Time discretization in the time-continuous pedestrian dynamics model SigmaEva

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NATURAL COMPUTING 2022年第3期21卷 407-415页

作者： Kirik, Ekaterina Vitova, Tat'yana Russian Acad Sci Inst Computat Modelling Siberian Branch Akademgorodok 50-44 Akademgorodok 660036 Russia

Time-continuous models need to set a value of time-step to simulate a process using a computer. The assumed size of a time-step influences the computational performance. But not only a quick calculations is a criterion. The other one is the reliability of the simulation results. The discretization of time in computer simulation of pedestrian movement is considered in the paper. We consider a discrete-continuous approach which is becoming popular nowadays. Both aspects are investigated for the time-continuous SigmaEva pedestrian dynamics model. We use fundamental diagrams as a measure to estimate the simulation quality. It is shown that short and long time-steps are not reasonable.

关键词： Pedestrian simulation discrete-continuous model Fundamental diagram Flow rate Time discretization Time-step Person's size

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