Abstract Resistive memory has become an attractive new memory type due to its outstanding performance. Oxide-based resistive random access memory (RRAM) is one type of widely used memory whose resistance can be transformed by applying current or voltage. Memristors are widely used in various kinds of memories and neural morphological calculations. Therefore, it is of vital importance to understand the physical change mechanism of an internal memristor under stimulation to improve electrical properties of the memristor. In our studies, a device model based on Hf oxide was proposed, then completely processes of the forming, reset and set were simulated. Meantime, the generation and recombination of oxygen vacancies were considered in all the processes, making the simulation more practical. In addition, a spike electrode structure was applied, a gathering electric field can be generated in the oxide layer so that the improved device has a faster forming voltage, lower forming current and lower instantaneous power consumption in the ON state. Finally, the effects of spike electrode length on the forming process were studied, the research results reveal that a longer probe electrode can engage a lower forming voltage and accelerate the formation of conductive filaments.
{"title":"Physical model simulations of Hf oxide resistive random access memory device with a spike electrode structure","authors":"Fei Yang, Bingkun Liu, Zijian He, Shilong Lou, Wentao Wang, Bo Hu, Duogui Li, Shuo Jiang","doi":"10.1088/1361-651x/ad0315","DOIUrl":"https://doi.org/10.1088/1361-651x/ad0315","url":null,"abstract":"Abstract Resistive memory has become an attractive new memory type due to its outstanding performance. Oxide-based resistive random access memory (RRAM) is one type of widely used memory whose resistance can be transformed by applying current or voltage. Memristors are widely used in various kinds of memories and neural morphological calculations. Therefore, it is of vital importance to understand the physical change mechanism of an internal memristor under stimulation to improve electrical properties of the memristor. In our studies, a device model based on Hf oxide was proposed, then completely processes of the forming, reset and set were simulated. Meantime, the generation and recombination of oxygen vacancies were considered in all the processes, making the simulation more practical. In addition, a spike electrode structure was applied, a gathering electric field can be generated in the oxide layer so that the improved device has a faster forming voltage, lower forming current and lower instantaneous power consumption in the ON state. Finally, the effects of spike electrode length on the forming process were studied, the research results reveal that a longer probe electrode can engage a lower forming voltage and accelerate the formation of conductive filaments.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135853433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-09DOI: 10.1088/1361-651x/acfe28
Donovan Birky, Karl Garbrecht, John Emery, Coleman Alleman, Geoffrey Bomarito, Jacob Hochhalter
Abstract To generate material models with fewer limiting assumptions while maintaining closed-form, interpretable solutions, we propose using genetic programming based symbolic regression (GPSR), a machine learning (ML) approach that describes data using free-form symbolic expressions. To maximize interpretability, we start from an analytical, derived material model, the Gurson model for porous ductile metals, and systematically relax inherent assumptions made in its derivation to understand each assumption’s contribution to the GPSR model forms. We incorporate transfer learning methods into the GPSR training process to increase GPSR efficiency and generate models that abide by known mechanics of the system. The results show that regularizing the GPSR fitness function is critical for generating physically valid models and illustrate how GPSR allows a high level of interpretability compared with other ML approaches. The method of systematic assumption relaxation allows the generation of models that address limiting assumptions found in the Gurson model, and the symbolic forms allow conjecture of decreased material strength due to void interaction and non-symmetric void shapes.
{"title":"Generalizing the Gurson Model Using Symbolic Regression and Transfer Learning to Relax Inherent Assumptions","authors":"Donovan Birky, Karl Garbrecht, John Emery, Coleman Alleman, Geoffrey Bomarito, Jacob Hochhalter","doi":"10.1088/1361-651x/acfe28","DOIUrl":"https://doi.org/10.1088/1361-651x/acfe28","url":null,"abstract":"Abstract To generate material models with fewer limiting assumptions while maintaining closed-form, interpretable solutions, we propose using genetic programming based symbolic regression (GPSR), a machine learning (ML) approach that describes data using free-form symbolic expressions. To maximize interpretability, we start from an analytical, derived material model, the Gurson model for porous ductile metals, and systematically relax inherent assumptions made in its derivation to understand each assumption’s contribution to the GPSR model forms. We incorporate transfer learning methods into the GPSR training process to increase GPSR efficiency and generate models that abide by known mechanics of the system. The results show that regularizing the GPSR fitness function is critical for generating physically valid models and illustrate how GPSR allows a high level of interpretability compared with other ML approaches. The method of systematic assumption relaxation allows the generation of models that address limiting assumptions found in the Gurson model, and the symbolic forms allow conjecture of decreased material strength due to void interaction and non-symmetric void shapes.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135044198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The Gurson–Tvergaard–Needleman (GTN) model has provided a powerful description of the nucleation growth and coalescence of micro voids, but it has limitations in simulating shear fracture due to the absence of a description of shear localization behavior. A shear improvement method is proposed for simulating the ductile fracture of materials under different stress states. The modified model not only allows for strain hardening of the matrix material, but also accounts for the stress degradation caused by shear. The strength equation of the material is described by both the shear stress state function and a decay function, making it easier for materials under shear stress state to experience material softening and further inducing shear fracture. The modified GTN model is developed by incorporating the shear stress degradation factor into the yield function, while taking into account both void growth and shear failure mechanisms. By carefully calibrating the model’s parameters, the deformation and fracture processes of tensile, plane strain, notch tensile, and compression specimens in the 7A52 aluminum alloy are simulated. The damage evolution behavior of the material under different stress states is analyzed. The results indicate that the damage include void growth mechanism and void shear mechanism. The proportions of these two mechanisms vary under different levels of stress triaxiality. Upon localizing material deformation, the shear stress state intensifies, and the shear damage mechanism assumes a critical role in fracture. The modified GTN model accurately predicts the load-displacement response and fracture path of the 7A52 aluminum alloy under a wide range of stress states.
{"title":"A Shear Modified GTN Model Based on Stress Degradation Method for Predicting Ductile Fracture","authors":"Fanlei Min, Kunyuan Gao, Xiaojun Zhang, Wu Wei, Peng Qi, Xiaolan Wu, shengping wen, Hui Huang, Zuoren Nie, Deijing Zhou","doi":"10.1088/1361-651x/acf8e0","DOIUrl":"https://doi.org/10.1088/1361-651x/acf8e0","url":null,"abstract":"Abstract The Gurson–Tvergaard–Needleman (GTN) model has provided a powerful description of the nucleation growth and coalescence of micro voids, but it has limitations in simulating shear fracture due to the absence of a description of shear localization behavior. A shear improvement method is proposed for simulating the ductile fracture of materials under different stress states. The modified model not only allows for strain hardening of the matrix material, but also accounts for the stress degradation caused by shear. The strength equation of the material is described by both the shear stress state function and a decay function, making it easier for materials under shear stress state to experience material softening and further inducing shear fracture. The modified GTN model is developed by incorporating the shear stress degradation factor into the yield function, while taking into account both void growth and shear failure mechanisms. By carefully calibrating the model’s parameters, the deformation and fracture processes of tensile, plane strain, notch tensile, and compression specimens in the 7A52 aluminum alloy are simulated. The damage evolution behavior of the material under different stress states is analyzed. The results indicate that the damage include void growth mechanism and void shear mechanism. The proportions of these two mechanisms vary under different levels of stress triaxiality. Upon localizing material deformation, the shear stress state intensifies, and the shear damage mechanism assumes a critical role in fracture. The modified GTN model accurately predicts the load-displacement response and fracture path of the 7A52 aluminum alloy under a wide range of stress states.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135043600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-09DOI: 10.1088/1361-651x/acfd47
Aman Arora, Harpreet Singh, Ilaksh Adlakha, Dhiraj K. Mahajan
Abstract New insights are provided into the role of vacancy-hydrogen (VaH) complexes, compared to the hydrogen atoms alone, on hydrogen embrittlement of nickel. The effect of the concentration of hydrogen atoms and VaH complexes is investigated in different crystal orientations on dislocation emission and propagation in single crystal of nickel using atomistic simulations. At first, embrittlement is studied on the basis of unstable and stable stacking fault energies as well as fracture energy to quantify the embrittlement ratio (unstable stacking fault energy/fracture energy). It is found that VaH complexes lead to high embrittlement compared to H atoms alone. Next, dislocation emission and propagation at pre-cracked single crystal crack-tip are investigated under Mode-I loading. Depending upon the elastic interaction energy and misfit volume, high local concentrations at the crack front lead to the formation of nickel-hydride and nickel-hydride with vacancies phases. These phases are shown to cause softening due to earlier and increased dislocation emission from the interface region. On the other hand, dislocation propagation under the random distribution of hydrogen atoms and VaH complexes at the crack front or along the slip plane shows that VaH complexes lead to hardening that corroborates well with the increased shear stresses observed along the slip plane. Further, VaH complexes lead to the disintegration of partial dislocation and a decrease in dislocation travel distance with respect to time. The softening during emission and hardening during propagation and disintegration of partial dislocation loops due to VaH complexes fit the experimental observations of various dislocation structures on fractured surfaces in the presence of hydrogen, as reported in literature.
{"title":"On the role of vacancy-hydrogen complexes on dislocation nucleation and propagation in metals","authors":"Aman Arora, Harpreet Singh, Ilaksh Adlakha, Dhiraj K. Mahajan","doi":"10.1088/1361-651x/acfd47","DOIUrl":"https://doi.org/10.1088/1361-651x/acfd47","url":null,"abstract":"Abstract New insights are provided into the role of vacancy-hydrogen (VaH) complexes, compared to the hydrogen atoms alone, on hydrogen embrittlement of nickel. The effect of the concentration of hydrogen atoms and VaH complexes is investigated in different crystal orientations on dislocation emission and propagation in single crystal of nickel using atomistic simulations. At first, embrittlement is studied on the basis of unstable and stable stacking fault energies as well as fracture energy to quantify the embrittlement ratio (unstable stacking fault energy/fracture energy). It is found that VaH complexes lead to high embrittlement compared to H atoms alone. Next, dislocation emission and propagation at pre-cracked single crystal crack-tip are investigated under Mode-I loading. Depending upon the elastic interaction energy and misfit volume, high local concentrations at the crack front lead to the formation of nickel-hydride and nickel-hydride with vacancies phases. These phases are shown to cause softening due to earlier and increased dislocation emission from the interface region. On the other hand, dislocation propagation under the random distribution of hydrogen atoms and VaH complexes at the crack front or along the slip plane shows that VaH complexes lead to hardening that corroborates well with the increased shear stresses observed along the slip plane. Further, VaH complexes lead to the disintegration of partial dislocation and a decrease in dislocation travel distance with respect to time. The softening during emission and hardening during propagation and disintegration of partial dislocation loops due to VaH complexes fit the experimental observations of various dislocation structures on fractured surfaces in the presence of hydrogen, as reported in literature.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135044317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-06DOI: 10.1088/1361-651X/acf9be
M. Seiz, H. Hierl, Britta Nestler
{"title":"Erratum: An improved grand-potential phase-field model of solid-state sintering for many particles (2023 Modelling Simul. Mater. Sci. Eng. 31 055006)","authors":"M. Seiz, H. Hierl, Britta Nestler","doi":"10.1088/1361-651X/acf9be","DOIUrl":"https://doi.org/10.1088/1361-651X/acf9be","url":null,"abstract":"","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"18 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139322542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-26DOI: 10.1088/1361-651x/acfd48
Farshid Golnary, M Asghari
Abstract Spinodal topologies formed through self-assembly processes exhibit unique mechanical properties, such as smoothness and non-periodicity, making them resistant to buckling and manufacturing defects. While extensive research has focused on their mechanical behavior, limited attention has been given to understanding the impact of their complex topology. This study aims to investigate the relationship between the topological features of two-dimensional spinodal topologies, characterized using computational homology, and their elastic response by analyzing scaling laws. Sensitivity analysis was conducted to determine the influence of various topological characteristics on Young's modulus and Poisson's ratio. Computational homology techniques were used to measure Betti numbers, which represent the number of loops and disjoint regions in the spinodal topologies. Additionally, these techniques were also employed to determine the size of these loops and regions. Among all the topological characteristics studied, the number and size of loops were found to have the highest influence on the elastic properties, specifically Young's modulus and Poisson's ratio. Understanding the rules that govern the way two-dimensional spinodal topologies respond elastically is crucial for comprehending how they behave mechanically and for optimizing their performance. The research findings highlight the significant impact of certain topological features, specifically the number and size of loops, on the material properties. This knowledge provides valuable insights for designing and engineering spinodal structures.
{"title":"Investigating the influence of topology on elasticity in spinodal microstructures","authors":"Farshid Golnary, M Asghari","doi":"10.1088/1361-651x/acfd48","DOIUrl":"https://doi.org/10.1088/1361-651x/acfd48","url":null,"abstract":"Abstract Spinodal topologies formed through self-assembly processes exhibit unique mechanical properties, such as smoothness and non-periodicity, making them resistant to buckling and manufacturing defects. While extensive research has focused on their mechanical behavior, limited attention has been given to understanding the impact of their complex topology. This study aims to investigate the relationship between the topological features of two-dimensional spinodal topologies, characterized using computational homology, and their elastic response by analyzing scaling laws. Sensitivity analysis was conducted to determine the influence of various topological characteristics on Young's modulus and Poisson's ratio. Computational homology techniques were used to measure Betti numbers, which represent the number of loops and disjoint regions in the spinodal topologies. Additionally, these techniques were also employed to determine the size of these loops and regions. Among all the topological characteristics studied, the number and size of loops were found to have the highest influence on the elastic properties, specifically Young's modulus and Poisson's ratio. Understanding the rules that govern the way two-dimensional spinodal topologies respond elastically is crucial for comprehending how they behave mechanically and for optimizing their performance. The research findings highlight the significant impact of certain topological features, specifically the number and size of loops, on the material properties. This knowledge provides valuable insights for designing and engineering spinodal structures.
","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"293 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134886090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.1088/1361-651x/acf9bd
Yu-Han Wu, Rao Huang, Yu-Hua Wen
Abstract Understanding the crystallization kinetics of Cr-Co alloys and providing a quantitative characterization of the microstructure evolution during quenching are of practical significance to their industrial applications. Using molecular dynamics simulations, we investigate the solidification of Cr 30 Co 70 and Cr 70 Co 30 subjected to different cooling rates. Besides, the outcomes are examined for their mechanical responses under uniaxial tensile loading. It is disclosed that slower cooling (⩽1 K ps −1 ) is beneficial to crystallization, while faster quenching generally leads to disordered structures. In the solidified outcomes, regardless of composition ratios and cooling rates, Co-Co bonding is the most favorable compared with that of Co-Cr and Cr-Cr. As for structural order, the Co-rich alloys exhibit a hexagonal close-packed (hcp) dominant crystalline order, while face-centered cubic (fcc) becomes more advantageous in the remaining cases. Among all the samples, the Cr 30 Co 70 obtained with 0.5 K ps −1 is an exception since it abnormally adopts fcc as a major crystalline order and realizes lower energy than expected. Additionally, under uniaxial tensile loading, a phase transition from fcc or hcp to body-centered cubic (bcc) is identified in the Cr 30 Co 70 samples, while it is absent in the Cr 70 Co 30 ones. These findings can aid in the design, manufacturing, and utilization of Cr-Co alloys in the field of material industry.
摘要了解Cr-Co合金的结晶动力学，定量表征淬火过程中的组织演变，对其工业应用具有重要意义。采用分子动力学模拟方法，研究了不同冷却速率下cr30co70和cr70co30的凝固过程。此外，还对其在单轴拉伸载荷下的力学响应进行了检验。结果表明，较慢的冷却(≥1 K ps−1)有利于结晶，而较快的冷却通常会导致结构紊乱。在凝固结果中，无论成分比和冷却速率如何，Co-Co的结合效果都优于Co-Cr和Cr-Cr。在结构顺序上，富钴合金以六方密排(hcp)为主，面心立方(fcc)为主。在所有样品中，在0.5 K ps−1条件下获得的Cr 30co 70是一个例外，因为它异常地以fcc为主要晶序，并且实现了比预期更低的能量。此外，在单轴拉伸载荷下，Cr 30 Co 70样品中发现了从fcc或hcp到体心立方(bcc)的相变，而Cr 70 Co 30样品中没有这种相变。这些发现有助于材料工业领域Cr-Co合金的设计、制造和应用。
{"title":"Crystallization kinetics, microstructure evolution, and mechanical responses of Cr-Co alloys","authors":"Yu-Han Wu, Rao Huang, Yu-Hua Wen","doi":"10.1088/1361-651x/acf9bd","DOIUrl":"https://doi.org/10.1088/1361-651x/acf9bd","url":null,"abstract":"Abstract Understanding the crystallization kinetics of Cr-Co alloys and providing a quantitative characterization of the microstructure evolution during quenching are of practical significance to their industrial applications. Using molecular dynamics simulations, we investigate the solidification of Cr 30 Co 70 and Cr 70 Co 30 subjected to different cooling rates. Besides, the outcomes are examined for their mechanical responses under uniaxial tensile loading. It is disclosed that slower cooling (⩽1 K ps −1 ) is beneficial to crystallization, while faster quenching generally leads to disordered structures. In the solidified outcomes, regardless of composition ratios and cooling rates, Co-Co bonding is the most favorable compared with that of Co-Cr and Cr-Cr. As for structural order, the Co-rich alloys exhibit a hexagonal close-packed (hcp) dominant crystalline order, while face-centered cubic (fcc) becomes more advantageous in the remaining cases. Among all the samples, the Cr 30 Co 70 obtained with 0.5 K ps −1 is an exception since it abnormally adopts fcc as a major crystalline order and realizes lower energy than expected. Additionally, under uniaxial tensile loading, a phase transition from fcc or hcp to body-centered cubic (bcc) is identified in the Cr 30 Co 70 samples, while it is absent in the Cr 70 Co 30 ones. These findings can aid in the design, manufacturing, and utilization of Cr-Co alloys in the field of material industry.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"125 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135769286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.1088/1361-651x/acf8df
Mahfooz Alam, Appala Naidu Gandi
Abstract Temperature dependence of structural, mechanical, and thermodynamic properties of γ -TiAl is modeled using an extended quasi-harmonic approximation and first-principles calculations. In the first step, the volumes are estimated as a function of temperature following the quasi-harmonic approximation. The lattice parameters are further optimized at fixed volumes in the second step. Modeled mechanical properties (bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and hardness) agree with the experimentally reported mechanical properties. Similarly, the modeled thermodynamic properties (entropy, heat capacity at constant pressure, Gibbs free energy) are in good agreement with the thermodynamic properties reported from experiments and CALculation of PHAse Diagrams approaches. This study suggests that further optimization of the degree of freedom in the unit cell improves the model accuracy of properties estimated following the quasi-harmonic approximation.
{"title":"Mechanical and Thermodynamic Properties of γ-TiAl Using First-Principles Calculations","authors":"Mahfooz Alam, Appala Naidu Gandi","doi":"10.1088/1361-651x/acf8df","DOIUrl":"https://doi.org/10.1088/1361-651x/acf8df","url":null,"abstract":"Abstract Temperature dependence of structural, mechanical, and thermodynamic properties of γ -TiAl is modeled using an extended quasi-harmonic approximation and first-principles calculations. In the first step, the volumes are estimated as a function of temperature following the quasi-harmonic approximation. The lattice parameters are further optimized at fixed volumes in the second step. Modeled mechanical properties (bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and hardness) agree with the experimentally reported mechanical properties. Similarly, the modeled thermodynamic properties (entropy, heat capacity at constant pressure, Gibbs free energy) are in good agreement with the thermodynamic properties reported from experiments and CALculation of PHAse Diagrams approaches. This study suggests that further optimization of the degree of freedom in the unit cell improves the model accuracy of properties estimated following the quasi-harmonic approximation.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135769615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-30DOI: 10.1088/1361-651X/acf512
Robert Kahlenberg, G. Falkinger, B. Milkereit, E. Kozeschnik
The simulation of heat changes resulting from phase transitions can help to interpret differential scanning calorimetry (DSC) measurements, e.g. of metallic alloy systems in which multiple reactions overlap during non-isothermal heat treatments. So far, simulated DSC curves mostly exhibit sharp reaction peaks as commonly just one mean energy value for a certain type of nucleation site is assumed. This work proposes an efficient model for treating heterogeneous nucleation site energy variations within the framework of classical nucleation theory (CNT). The site energies are assumed to vary according to a Rayleigh distribution and a scaling function. The effect on the nucleation behavior of precipitates is studied. A consideration of the distribution of heterogeneous site energies has the potential to significantly smoothen the numerical treatment of precipitation processes compared to the non-distributed case. The comparison to previously published simulations of DSC curves during the cooling of an AA6005 aluminum alloy demonstrates the advantages of this extension, especially for slow cooling rates.
{"title":"Modeling of heterogeneous site energy distributions in precipitate nucleation","authors":"Robert Kahlenberg, G. Falkinger, B. Milkereit, E. Kozeschnik","doi":"10.1088/1361-651X/acf512","DOIUrl":"https://doi.org/10.1088/1361-651X/acf512","url":null,"abstract":"The simulation of heat changes resulting from phase transitions can help to interpret differential scanning calorimetry (DSC) measurements, e.g. of metallic alloy systems in which multiple reactions overlap during non-isothermal heat treatments. So far, simulated DSC curves mostly exhibit sharp reaction peaks as commonly just one mean energy value for a certain type of nucleation site is assumed. This work proposes an efficient model for treating heterogeneous nucleation site energy variations within the framework of classical nucleation theory (CNT). The site energies are assumed to vary according to a Rayleigh distribution and a scaling function. The effect on the nucleation behavior of precipitates is studied. A consideration of the distribution of heterogeneous site energies has the potential to significantly smoothen the numerical treatment of precipitation processes compared to the non-distributed case. The comparison to previously published simulations of DSC curves during the cooling of an AA6005 aluminum alloy demonstrates the advantages of this extension, especially for slow cooling rates.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":" ","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41940512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-30DOI: 10.1088/1361-651X/acf514
S. Aditya, T. Sohail, Samit Roy
A generalized framework for anchor point based concurrent coupling of finite element method (FEM) and molecular dynamics (MD) domains, incorporating previous related methods, is presented. The framework is robust and is agnostic of material crystallinity and atomistic description. The method follows an iterative approach to minimize the total energy of the coupled FEM-MD system, while maintaining displacement constraints between the domains. Two distinct forms of the coupling method are discussed in detail, differing in the nature of the constraint, both of which are able to make use of specialized MD solvers such as LAMMPS with little or no modification. Both methods make use of springs that join groups of atoms in the MD to the FEM domain. Method 1, termed ‘Direct Coupling’, couples MD anchor points directly to the FEM domain in a force-based manner and has the added advantage of being able to couple to specialized FEM solvers such as ABAQUS. Method 2 couples the MD to the FEM domain in a more ‘soft’ manner using the method of Lagrange multipliers and least squares approximation. The relative performance of these two methods are tested against each other in a uniaxial tension test using a graphene monolayer at 300 K temperature and a block of thermosetting polymer EPON862 at low temperature, showing comparable results. Convergence behaviour of the two coupling methods are studied and presented. The methods are then applied to the fracture of a centre-cracked graphene monolayer and compared with results from an identical pure MD simulation. The results corroborate the effectiveness of the developed method and potential use as a plug-and-play tool to couple pre-existing specialized FEM and MD solvers. Future work will focus on applying these methods to simulate elevated-temperature amorphous polymer models and their brittle fracture.
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