Crystal Model Research Articles

A monolithically implicit time-integration approach for a dislocation-density-based b.c.c. single crystal plasticity model

A monolithically implicit time-integration approach for a dislocation-density-based b.c.c. single crystal plasticity model

Effect of wire diameter compression ratio on drawing deformation of micro copper wire

A crystal plasticity finite element model was developed for the drawing deformation of pure copper micro wire, based on rate-dependent crystal plasticity theory. The impact of wire diameter compression ratio on the micro-mechanical deformation behavior during the wire drawing process was investigated. Results indicate that the internal deformation and slip of the drawn wire are unevenly distributed, forming distinct slip and non-slip zones. Additionally, horizontal strain concentration bands develop within the drawn wire. As the wire diameter compression ratio increases, the strength of the slip systems and the extent of slip zones inside the deformation zone also increase. However, the fluctuating stress state, induced by contact pressure and frictional stress, results in a rough and uneven wire surface and diminishes the stability of the drawing process.

Effect of pre-straining direction on the microstructure, mechanical properties and microstructural response of AA2099-T83 Al-Li alloy

Understanding the microstructural evolution and anisotropic behavior of Al-Li alloys after pre-deformation in different directions is crucial for optimizing their forming performance. This study investigates the microstructural evolution in AA2099 Al-Li alloy rolled sheets after pre-deformation in the extrusion direction (ED) and transverse direction (TD), and the resulting changes in mechanical properties during subsequent tensile deformation. A crystal plasticity finite element model (CPFEM) was established to quantitatively analyze the link between pre-deformation direction and the microstructural response during the hardening stages of tensile deformation. The results showed that the differences in mechanical properties due to pre-deformation direction are mainly attributed to the variations in volume fraction and diameter of the T1 precipitates. The contributions of T1 phase to yield strength are estimated to be 239 MPa (ED) and 223 MPa (TD), respectively. An increase in T1 (Al2CuLi) phase volume fraction and a decrease in phase diameter lead to higher average von Mises stress and average maximum principal strain values during the hardening stages.

Regularity for a Fractional Liquid Crystal Model with Anomalous Dissipation and Thermal Effects

Regularity for a Fractional Liquid Crystal Model with Anomalous Dissipation and Thermal Effects

Determining plastic slips in rate-independent crystal plasticity models through machine learning algorithms

Dislocation slip-based crystal plasticity models have been a great success in connecting the fundamental physics with the macroscopic deformation of crystalline materials. Pioneered by Taylor in his work on “plastic strain in metals” (Taylor, 1938), and further advanced by Bishop and Hill (1951a, 1951b), the Taylor–Bishop–Hill theory laid the foundation of today’s constitutive models on crystal plasticity. An intriguing part of those modeling is to determine the active slip systems—which system to be involved in and how much it contributes to the deformation. In this paper, we developed a machine learning-based algorithm to determine accurately and efficiently the active slip systems in crystal plasticity constitutive models. Applications to the common three polycrystalline metals, face-centered cubic (FCC) copper, body-centered cubic (BCC) α-iron, and hexagonal close-packed (HCP) AZ31B, demonstrate that even a simple neural network could give rise to accurate and efficient results in comparing with traditional routines. There seems to be plenty of space for further reducing the computation time and hence scaling up the simulating samples.

An informatics method for inferring the hardening exponent of plasticity in polycrystalline metals from surface strain measurements

The investigation of strain hardening in metals is complex, with the outcome depending on experimental conditions, that may involve microstructural history, temperature and loading rate. Hardening is commonly measured, after mechanical processing, through controlled mechanical testing, in ways that either distinguish elastic (stress) from total deformation measurements, or by identifying plastic slip contributions. In this paper, we conjecture that hardening effects can be unraveled through statistical analysis of total strain fluctuations during the evolution sequence of profiles, measured in-situ, through digital image correlation. In particular, we hypothesize that the work hardening exponent is related, through a power-law relationship, to a particular exponent arising from principal component analysis. We demonstrate a scaling analysis for synthetic data produced by widely applicable crystal plasticity models for polycrystalline solids.Graphical

A class of efficient high-order time-stepping methods for the anisotropic phase-field dendritic crystal growth model

In this paper, we develop and analyze a novel class of arbitrarily high-order and unconditionally energy stable schemes for the anisotropic phase-field dendritic crystal growth model, which is a highly nonlinear system that combines the anisotropic Allen–Cahn equation with the thermal equation. The proposed schemes are based on an extrapolated and linearized Runge–Kutta method for an auxiliary variable reformulation of the crystal growth model. A delicate implementation demonstrates that the proposed method can be realized in a very efficient way, requiring only the solution of a coupled linear elliptic system at each time step. We prove that the constructed schemes satisfy the energy dissipation property and demonstrate the convergence order through a consistency error analysis. To the best of our knowledge, this is the first unconditionally stable scheme of arbitrarily high-order for the anisotropic phase-field dendritic crystal growth model. Numerical experiments for two and three dimensional dendritic crystal growth are simulated to verify our theoretical accuracy as well as the efficiency of the proposed method. Furthermore, to emphasize the superiority of the high-order schemes, we present a numerical comparison that directly contrasts its performance with the lower-order schemes.

Comprehensive Investigation of the Crystal Structure of Cation-Disordered Li3VO4 as a High-Rate Anode Material: Unveiling the Dichotomy between Order and Disorder.

This study investigates mechanochemical synthesis and cation-disordering mechanism of wurtzite-type Li3VO4 (LVO), highlighting its promise as a high-performance anode material for lithium-ion batteries and hybrid supercapacitors. Mechanochemical treatment of pristine LVO using a high-energy ball mill results in a "pure cation-disordered" LVO phase, allowing for meticulous analysis of cation arrangement. The X-ray and neutron diffraction study demonstrates progressive loss of order in LVO crystal with increasing milling duration. High-resolution transmission electron microscopy reveals disrupted lattice fringes, indicating cationic misalignment. Pair-distribution function analysis confirms loss of cation arrangements and the presence of short-range order. Combination of these multiple analytical techniques achieves a comprehensive understanding of cation regularity and clearly demonstrates order/disorder dichotomy in cation-disordered materials, ranging from short (<8 Å) to middle-long range (8-30 Å), using an integrated superstructure model of the cation-disordered LVO crystals. Electrochemical testing reveals that mechanochemically treated LVO exhibits superior rate capability, with a 70% capacity retention at a high current density of 50C-rate. Lithium diffusion coefficient measurements demonstrate enhanced lithium-ion mobility in the mechanochemically treated LVO, attributed to cation-disordering effect. These findings provide valuable insights into mechanochemical cation-disordering in LVO, presenting its potential as an efficient anode material for lithium-ion-based electrochemical energy storage.

Isogeometric collocation method to simulate phase-field crystal model

PurposeThe purpose of this study is to develop a new numerical algorithm to simulate the phase-field model.Design/methodology/approachFirst, the derivative of the temporal direction is discretized by a second-order linearized finite difference scheme where it conserves the energy stability of the mathematical model. Then, the isogeometric collocation (IGC) method is used to approximate the derivative of spacial direction. The IGC procedure can be applied on irregular physical domains. The IGC method is constructed based upon the nonuniform rational B-splines (NURBS). Each curve and surface can be approximated by the NURBS. Also, a map will be defined to project the physical domain to a simple computational domain. In this procedure, the partial derivatives will be transformed to the new domain by the Jacobian and Hessian matrices. According to the mentioned procedure, the first- and second-order differential matrices are built. Furthermore, the pseudo-spectral algorithm is used to derive the first- and second-order nodal differential matrices. In the end, the Greville Abscissae points are used to the collocation method.FindingsIn the numerical experiments, the efficiency and accuracy of the proposed method are assessed through two examples, demonstrating its performance on both rectangular and nonrectangular domains.Originality/valueThis research work introduces the IGC method as a simulation technique for the phase-field crystal model.

Microstructural analysis and densification of ordinary Portland cement mortars incorporated with minimal nano-TiO2: intermixing and surface coating on both fresh and hardened surfaces

The present study investigated the microstructural properties of ordinary Portland cement (OPC)-modified with minimum dosage of nano TiO2 on fresh and hardened cement mortar surfaces and intermixed samples. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were used to analyze the morphology and hydration products of the OPC specimens doped with nanotitanium (NT).Additionally, XRD coupled with Rietveld refinement was employed to quantify the crystal phases and refine the crystal structure model through the comparison of the calculated diffraction pattern to the measured pattern. Subsequently, crystallographic analysis was conducted to evaluate the crystallographic structure and to confirm the existence of specific atoms and bonds within the crystal structure altered with NT. The findings revealed that the addition of minimal NT resulted in a more compact and denser microstructure, characterized by increased formation of calcium silicate hydrate (CSH) gel and a reduction in calcium hydroxide (CH) crystals.This led to a reduction in the porosity of the hardened coating surface, with similar improvements observed for the fresh coating and intermixed samples compared to those of the control mortar. A decrease in the lattice parameters, accompanied by an increase in the number of atoms, bonds and polyhedra in the crystal structure, led to alterations in the interatomic spacing and contributed to the densification of the cementitious matrix.The findings also showed that NT integration led to a more compact structure with shorter bond distances and smaller polyhedral volumes for the Ti samples than for the control sample. Moreover, compared with the freshly cast and hardened coating samples, the NT-intermixed samples exhibited the shortest Ti–O bond distances and the smallest polyhedral volume. Overall, the analysis presented in this study significantly contributes to the development of novel and environmentally friendly photocatalytic cementitious materials at minimal dosages.

Passive and active field theories for disease spreading

The worldwide COVID-19 pandemic has led to a significant growth of interest in the development of mathematical models that allow to describe effects such as social distancing measures, the development of vaccines, and mutations. Several of these models are based on concepts from soft matter theory. Considerably less well investigated is the reverse direction, i.e. how results from epidemiological research can be of interest for the physics of colloids and polymers. In this work, we consider the susceptible-infected-recovered (SIR)-dynamical density functional theory (DDFT) model, a combination of the SIR model from epidemiology with DDFT from nonequilibrium soft matter physics, which allows for an explicit modeling of social distancing. We extend the SIR-DDFT model both from an epidemiological perspective by incorporating vaccines, asymptomaticity, reinfections, and mutations, and from a soft matter perspective by incorporating noise and self-propulsion and by deriving a phase field crystal (PFC) model that allows for a simplified description. On this basis, we investigate via computer simulations how epidemiological models are affected by the presence of non-reciprocal interactions. This is done in a numerical study of a zombie outbreak.

A dislocation-based crystal plasticity model for single-crystal micropillars based on strain burst with stochastic characteristics

A dislocation-based crystal plasticity model for single-crystal micropillars based on strain burst with stochastic characteristics

The development of grain resolved stress fields around notch tips in soft-textured zirconium polycrystals: A three-dimensional synchrotron X-ray diffraction study

Texture, microstructure, and local grain neighbourhood contribute to the development of localized stresses in polycrystals. For hexagonal close-packed materials, crystal's elastic and plastic anisotropy can also be a major contributing factor, yet there is a paucity of experimental studies focusing on the extent of contribution of such parameters on the magnitude of localized stresses at microscales. This study focuses on addressing this knowledge gap by deforming double-edge-notched soft-textured α-zirconium specimens in-situ, while measuring grain scale tensorial stresses using high energy synchrotron X-ray diffraction. The specimens were subjected to cyclic loads to study the evolution of stresses in the vicinity of both shallow and deep notches. The soft-texture of the specimens is such that there are no c-axes of grains aligned along the macroscopic loading direction thereby inhibiting deformation twinning. The “as-measured” microstructures and notch geometries were imported into a crystal plasticity finite element model for further analysis. Results show that despite the absence of c-axes of grains aligned along loading direction, the developed stresses were substantially influenced by crystallographic orientations. Stress drop was observed near the onset of plasticity with further loading and the orientation and position effects were highlighted. A plastic deformation mechanism was revealed where, upon specimen loading, the mechanical constraints enforced during grain-grain interactions led to hardening. Accordingly, a parameter was devised to quantify the grain level hardening arising from this mechanism. It was shown that grain-scale stress concentration factors vary significantly before the onset of plasticity, but they settle in the plastic zone and with the progression of cycles.

Biomimetic Synthesis of Calcium Carbonate in Bile in the presence of Amino Acids

Thermodynamic and experimental modeling of calcium carbonate crystallization in a model solution of human bile has been carried out. The process of calcium carbonate (calcite and vaterite) crystallization from solutions containing bile has been studied. It is shown that differences in the phase and group composition of the samples arise depending on the synthesis parameters. It has been established that in the presence of 1 wt. % bile, calcite is formed, and an increase in the concentration of bile in the initial solution from 5 to 100 wt. % contributes to the crystallization of vaterite. It is shown that the mass of the solid phase increases with an increase in the concentration of bile in the initial solution. The dissolution of the synthesized samples was performed in 0.9 wt. % NaCl solution and 0.05 M EDTA solution. It was found that the presence of bile components in the composition of solid samples reduces the rate of their dissolutions.

The Effect of Lidan Huashi Pills on the Glutathione Peroxidase Activity and Growth of Calcium Oxalate Crystals in the Kidneys of Rats

Objective: To explore the effects of Lidan Huashi Pills on the glutathione peroxidase (GSH-Px) activity and growth of calcium oxalate crystals in the kidneys of rats. Methods: 30 rats were randomly divided into a blank group, a model group, and an experimental group, with 10 rats in each group. The blank group was free to eat and drink water for 8 weeks; the ethylene glycol method was used for the standard calcium oxalate crystal modeling in the control group and experimental group for 4 weeks. The model group was given free feeding and physiological saline (2 ml/d) by continuous gavage for 4 weeks; the experimental group was given free feeding and Lidan Huashi Pills (450 mg/kg, 2 ml/d) by continuous gavage for 4 weeks. After 4 weeks, all rats were euthanized, and the left kidney was taken for GSH-Px level detection. The right kidney was stained with hematoxylin and eosin (H&amp;E) to observe the formation of calcium oxalate crystals. Results: After 4 weeks of modeling, the urinary calcium levels in the model group and experimental group significantly increased compared to the blank group (868.00 ± 39.29 vs 929.40 ± 33.61, P &lt; 0.05), indicating successful modeling. The urine calcium ion concentration in the experimental group after modeling was significantly lower than that in the model group (929.40 ± 33.61 vs 888.60 ± 25.92, P &lt; 0.05). The grading score of calcium oxalate crystals in the model group was significantly higher than that in the blank group (P &lt; 0.05); the grading score of calcium oxalate crystals in the experimental group was lower than that in the model group, and the difference was not statistically significant (P &gt; 0.05). The GSH-Px activity in the left kidney of the model group was significantly lower than that of the blank group [203.49 (208.21, 144.22) vs 494.91 (431.32, 538.18), P &lt; 0.05); the GSH-Px activity in the left kidney of the experimental group was significantly higher than that of the model group [433.60 (383.86, 504.49) vs 203.49 (208.21, 144.22), P &lt; 0.05). Morphological observation and H&amp;E staining suggest that the formation of right kidney crystals and inflammation in the experimental group are between the blank group and the model group. Conclusion: Lidan Huashi Pills can enhance the serum GSH-Px activity in rats and inhibit the growth of calcium oxalate crystals and inflammatory response in the kidneys, thus playing a role in preventing and treating urinary tract stones.

Linking Grain Size to Microscopic Hardening Laws in a Phenomenological Crystal Plasticity Model: A Finite Element Simulation Approach for 316L Stainless Steel

Linking Grain Size to Microscopic Hardening Laws in a Phenomenological Crystal Plasticity Model: A Finite Element Simulation Approach for 316L Stainless Steel

Simulation of time-crystal-like behavior for a few-boson chiral soliton model in a ring

We present numerical simulations for a chiral soliton model with N=2,3 bosons in a ring, which is a few-particle version of our previous mean-field model for a quantum time crystal. Following Syrwid, Kosior, and Sacha (SKS), the notion is that a precise position measurement of one particle can lead to spontaneous formation of a bright soliton that in a time crystal should rotate intact for at least a few revolutions around the ring. In their work SKS found spontaneous formation of a soliton due to the position measurement, but quantum fluctuations cause the soliton to subsequently decay before it has a chance to perform even one revolution of the ring. Based on this, they concluded that time-crystal dynamics are impossible for Wilczek's model of a bright soliton in a ring. In contrast, for our few-boson chiral soliton model, allowing for imprecise (weak) measurements of the particle position, we show that time-crystal-like behavior is possible, allowing for several revolutions of the spontaneously formed soliton around the ring. Published by the American Physical Society 2024

Analysis of vibrational modes and weak interactions in terahertz spectra of γ-aminobutyric acid and its isomer L-2-aminobutyric acid

Aminobutyric acid, a non-proteinogenic amino acid, is present in the human body and influences physiological functions, exhibiting promising pharmaceutical prospects. γ-Aminobutyric Acid (GABA) and its isomer, L-2-Aminobutyric Acid (L-AABA), exhibit unique characteristic absorption peaks in the 0.6 to 2.5 THz range. To elucidate the mechanisms behind these absorption peaks, this study employed Density Functional Theory (DFT) for theoretical simulations of the crystal cell models of L-AABA and GABA, achieving terahertz spectra consistent with experimental results. Additionally, the study utilized Vibrational Mode Automatic Relevance Determination (VMARD) and Interaction Region Indicator (IRI) methodologies to interpret the vibrational modes corresponding to different absorption peaks and to detail the locations and types of intermolecular interactions within the crystals. Research indicates that the combination of terahertz time-domain spectroscopy (THz-TDS) and theoretical calculations can serve as an effective method for identifying isomers of Aminobutyric Acid and detecting intermolecular weak interactions such as hydrogen bonds within these crystals.

Dual-phase polycrystalline crystal plasticity model revealing the relationship between microstructural characteristics and mechanical properties in additively manufactured maraging steel

To elucidate the relationship between microstructural characteristics and mechanical properties in additively manufactured (AM) maraging steel, this study introduces a computational approach that addresses two fundamental challenges. Firstly, it addresses the creation of representative volume elements (RVEs) that mimic the observed microstructural complexities, such as meltpool boundaries, prior austenite grains, packets and blocks of lath martensite. This is accomplished through the application of Potts Monte-Carlo methods and grain segmentation techniques in accordance with the Kurdjumov–Sachs orientation relationship. Secondly, this study develops a comprehensive crystal plasticity (CP) model encompassing both bcc and fcc plasticity. Inspired by atomistic and discrete dislocation dynamics studies, the proposed CP model incorporates characteristics intrinsic to bcc plasticity, including non-Schmid effects, dislocation and precipitate strengthening, and Hall–Petch type strengthening of elongated martensitic blocks. Utilizing the created RVEs and the proposed CP framework, finite element simulations are conducted based on an update-Lagrangian formulation. The purpose of this study is to investigate the deformation behavior, texture evolution, tension–compression asymmetry, and evolution in dislocation density in RVEs representative of as-built and heat-treated samples of maraging steel. This computational approach and its findings deepen our understanding of the intricate interplay between microstructural characteristics and mechanical properties in maraging steel and also provide valuable guidelines for refining its additive manufacturing and heat treatment processes.

Odd-even trends in the series of new bis(α,ω-alkanediamine)dibromocadmium(II) coordination polymers: Crystal structure and thermal decomposition

In this paper, organic-inorganic coordination polymers of the CdBr2(H2N-(CH2)n-NH2) general formula, where n = 4 – 10 and 12, were studied. All the materials were synthesized as very fine powders from metal salt and diamine solutions following an analogous simple procedure. Scanning electron microscopy (SEM) images and recorded powder X-ray diffraction patterns (PXRD) allowed for the assessment of the purity and crystallinity of the products. Based on the collected diffraction data, lattice parameters and symmetry were determined. For five of the synthesized compounds (n = 4, 6, 7, 8, and 12) that were of relatively high purity and sufficient crystallinity, crystal structure models were determined and refined. It was found that the structure symmetry depends on the parity of the number of carbon atoms in the diamine molecules. Structures of the investigated compounds belonging to the even series are centrosymmetric while the ones from the odd series are not (P21 space group). Structures’ symmetry of compounds based on even diamines decreases from P2/m to P1¯ with increasing length of the organic molecules. Diamine molecules are aligned parallel to the diagonals of the (010) faces of the unit cell and there is an almost perfectly linear correlation between the value of a lattice parameter and the number of C atoms. There are, however, separate trends for even or odd series. Differential scanning calorimetry (DSC) and non-ambient PXRD measurements provided information about the thermal decomposition of the materials. The temperature of decomposition decreases with the growing length of diamine molecules and achieves the lowest value (176 °C, 449 K) for the compound with 1,12-diaminododecane (the longest diamine among the studied ones) while the sample with 1,4-diaminobutane is the most stable one (up to around 284 °C, 557 K). The studied compounds also show odd-even separate trends concerning the decomposition temperature. The compounds with even diamines start to decompose at relatively higher temperatures than the ones belonging to the odd series.