Heterogeneous Deformation Research Articles

Quantifying Heterogeneous Degradation Pathways and Deformation Fields in Solid‐State Batteries

AbstractSolid‐state batteries are compelling candidates for next‐generation energy storage devices, promising both high energy density and improved safety, by utilizing metallic Li as the negative electrode. However, they suffer from poor cyclability and rate capability, which limits their wide application. Degradation in these devices occurs through complex mechanical, chemical and electrochemical pathways, all of which produce heterogeneous deformation fields. Therefore, isolating solid‐state degradation mechanisms, and explicitly linking them to the associated deformation fields requires a multimodal characterization strategy. Here, a novel 3‐D, in situ methodology for linking degradation to deformation in solid‐state cells is presented. X‐ray imaging is used to measure the morphological degradation, and combined with X‐ray diffraction to quantify (electro)chemical aspects. Finally, the heterogeneous stress fields from these various pathways are mapped in situ. This heterogeneity is shown globally, from the interface to the bulk electrolyte, as well as locally, around features such as cracks and voids. Through these analyses, it is possible to delineate the effects of solid electrolyte processing, cell assembly, and cycling on the end‐of‐life state of the cell. Moreover, the importance of stress mitigation in these cells is highlighted, with mean stresses around the interface and some cracks comfortably exceeding the elastic limit of Li.

Thermo-hydro-mechanical modelling of the heterogeneous subsidence and swelling in the desiccation cracked clayey strata

Soil desiccation cracking as a consequence of severe environmental changes alters soil deformation mechanisms significantly. Therefore, this study aims to explore the effect of crack characteristics and environmental conditions on the heterogeneous deformation of desiccation-cracked soils using thermo-hydro-mechanical analyses. The model framework consists of balance equations, thermal, hydraulic, and mechanical constitutive equations, while the model scenarios were determined based on statistical analyses. The meteorological record of Qom city was used for three years, from 2015 to 2017, to capture long-term behaviour under wetting-drying cycles. Findings revealed that cracks extend the deformation range, potentially up to six times, with variation based on crack dimensions and spacing. Notably, narrower cracks experienced more pronounced deformation than wider ones. The cracked soil with a crack depth of 2.5 m showed 1.5 times higher swelling and subsidence than crack depth of 1 m. Furthermore, the wider cracks indicated a lower rate of increase in their dimensions compared to the initial state during drying. The investigation also highlights the mechanisms of soil surface shape due to swelling and shrinkage, resulting in concave and convex surfaces, respectively. The results provide new perspectives on the behaviour of fine-grained deposits in arid to semi-arid climates with deep groundwater levels.

Layer thickness dependent strengthening and strain delocalization mechanism in CuTa nanopillars with nanoscale amorphous/amorphous interfaces

Introducing amorphous/amorphous interfaces in metallic glasses offers an effective strategy to address the strength-plasticity trade-off by suppressing the strain localization. Elucidating the underlying size-dependent deformation mechanisms is crucial for designing strong and ductile amorphous nanolayered materials. Herein, molecular dynamics simulations are conducted to investigate the deformation behaviors of Cu70Ta30/Cu30Ta70 amorphous/amorphous nanopillars (AANPs) under compression, focusing on the intrinsic size effect of amorphous layer thickness. The results indicate a critical layer thickness of approximately 6.7 nm, below which an inverse Hall-Petch relation occurs. This transition is attributed to a shift in dominant deformation mode from the necking and localized deformation to the relatively homogeneous deformation as the layer thicknesses decreases. These A/A interfaces could be considered as a third medium phase in nanolaminates, especially when the thickness is very low, down to only a few of nm. The mechanical properties and deformation behavior of transitional interface phase lie between those of soft and hard phases, balancing heterogeneous deformation between hard and soft layers and resulting in homogeneous flow deformation of specimen with thinner amorphous layer. These findings provide insight for designing ductile amorphous materials through architecting nanoscale amorphous/amorphous interfaces.

Impact of structural characteristics on energy-absorption of 3D-printed thermoplastic polyurethane line-oriented structures

Purpose Additive manufacturing offers the ability to produce complex, flexible structures from materials like thermoplastic polyurethane (TPU) for energy-absorption applications. However, selecting optimal structural parameters to achieve desired mechanical responses remains a challenge. This study aims to investigate the influence of key structural characteristics on the energy absorption and dissipation behavior and the deformation process of 3D-printed flexible TPU line-oriented structures. Design/methodology/approach Samples with varying line orientations and infill densities were fabricated using material extrusion and subjected to quasi-static compression tests. The design of experiments methodology explored the significance of design variables and their interaction effects on energy absorption and dissipation. Findings The results revealed a statistically significant interaction between infill density and orientation, highlighting their combined influence; however, the effect was less pronounced compared to infill density alone. For low-density structures, changing the orientation from 0°/90° to 45°/−45° and increasing infill density enhanced energy absorption and dissipation, while high-density structures exhibited unique energy absorption behavior influenced by deformation patterns and heterogeneity levels. This study facilitates the prediction of mechanical responses and selection of suitable TPU line-oriented printed parts for energy absorbing applications. Originality/value To the best of the authors’ knowledge, the present work have investigated for the first time the energy-related responses of flexible line-oriented TPU structures highlighting the distinction between the low and high density structures.

Heterogeneous Deformation of As-Built Nickel Alloy 625 with Checkered Columnar Grains at Different Strain Rates (AMB2022-04)

Heterogeneous Deformation of As-Built Nickel Alloy 625 with Checkered Columnar Grains at Different Strain Rates (AMB2022-04)

Simulation of deformation and flow of pulmonary acinus using morphing compared with self-similar deformation

AbstractIn previous studies of the flow inside the pulmonary acinus, the deformation of acinus was limited because a relatively simple deformation methods, such as self-similar deformation, is used. However, acinus deformation may be complex and heterogeneous. The purpose of this study is to evaluate the influence of the difference in wall deformation between the morphed model and the self-similar deformation model on flow field. The heterogeneous deformation achieved in this study is more actual by using the morphing technology that continuously changes from one shape to another. STAR-CCM + Ver. 13.06 (Siemens PLM Software) was used for numerical calculation, and the governing equations of working fluid are continuous equations and Navier–Stokes equations (NS equations). As a result, the differences in deformation influenced the formation of streamlines at the distal end of the alveolar regions. In the self-similar deformation model, the flow does not change throughout a cycle, whereas in the morphed model, the flow changes during a cycle. Graphic abstract

Microstructure-sensitive crystal plasticity and phase-field modeling of deformation and fracture in polycrystalline ice

The formation of crevasses in Greenland and Antarctica is primarily driven by the brittle failure of ice at low strain rates. Understanding this phenomenon requires exploring the effect of microstructural heterogeneity and anisotropic elastoplastic deformation on the fracture behavior of ice. Here, we have developed a microstructure-sensitive coupled crystal plasticity and phase-field model. This model allows us to study the plastic deformation, damage initiation and propagation under various strain rates in hexagonal open-packed polycrystalline ice, the prevailing phase on Earth. By employing a Bayesian optimization method, we derived the material parameters for the micromechanical model based on experimental results. The modeling results reveal that the activation of basal dislocations results in a brittle to ductile transition in ice at a low strain rate of 10-7s-1 under tension. At higher strain rates, the intrinsic plastic anisotropy of ice leads to heterogeneous deformation among grains and stress concentration near grain boundaries, triggering crack initiation and exacerbating the brittleness of ice. Under compression, cracks usually do not propagate throughout the specimen due to a significant decrease in stress around the crack tip upon propagation. Moreover, we found that the formation of the shear-induced basal texture at the bottom of ice layers and along glacier valley sides intensifies the brittleness of ice. This study provides insights into the micromechanical deformation and fracture mechanisms of ice, elucidating the intricate process of crevasse development in polar ice sheets.

Heterogeneous Seasonal Deformation and Strain Budget in Himachal, NW Himalaya from new cGPS measurements: Hydrological and Seismic Hazard Implications

GPS measurements from 10 new permanent sites installed in Himachal, NW Himalaya are analysed with the primary objective to decipher the seasonal crustal deformation characteristics, its origins and hydrological implications. Additionally, we focus on the seismic hazard implications of the seasonal transients as well as of the long-term secular motion of GPS sites. Our findings suggest that the global hydrological loading models can relatively well explain the temporal surface displacements resulting from the monsoon rainfall in the Indo-Gangetic plains (IGP) but poorly account for the winter snowfall in Higher Himalaya. The approximately elliptical horizontal seasonal motion of GPS sites seems to be controlled by the spatio-temporal variations in the monsoonal hydrological load over the IGP. The hydrological process derived from the GPS data suggests slow and steady recovery in the water storage in Himachal Himalaya. The more intriguing phenomena is reflected in the unusually high seasonal site uplift and the yearlong (mid-2020 – mid-2021) plunge in the water storage corresponding to the time-period of COVID-19 lockdown phases, which could be speculated as its indirect impact on the crustal deformation history. The seasonal strain analysis revealed significant spatial heterogeneity. The arc-normal and arc-parallel seasonal strain resulting from differential seasonal motion between GPS sites seems to be primarily localized in the vicinity of locking transition zone, while the locked segment is being largely translated without experiencing significant strain. The localized seasonal strain showed positive correlation with the background seismicity rate suggesting possible modulation of the earthquake nucleation process. The regional seismic hazard assessment suggests susceptibility to a future great earthquake of ∼Mw8.4. The additional observed equivalency between the updated strain budget (∼9.3 m) and the previously reported co-seismic displacement (∼9.3 m) during the last great earthquake around ∼1400–1500 CE, suggests a recurrence interval of ∼600 years for great earthquake events in Himachal Himalaya with significant reliability.

The rheological structure of East Asian continental lithosphere

The rheological structure of the East Asia continent is the key to understanding its broad, heterogeneous, and intense Cenozoic deformation. Based on a refined three-dimensional thermal structure of the lithosphere in this region and the latest strain rate data, we derived a model of the rheological structure of the East Asian continental lithosphere. The strength envelopes, defined by the yield strength of frictional, fractural, and plastic creep, are constrained by the lithological stratification based on previous studies and the depth distribution of earthquakes. The results show large vertical and lateral variations of lithospheric strength in the East Asian continent. A weak lower crust with low effective viscosity is ubiquitous. The rheological structure agrees with the jelly sandwich model in cratons, where the mantle lithosphere is relatively strong. The Tibetan Plateau has the weakest lower crust, with its effective viscosity ranging from 1019 to 1020 Pa∙s. Its mantle lithosphere is weakened by relatively high temperature; hence, its rheological structure can be described by the crème brûlée model. The lithospheric scale faults and suture zones in and around the Tibetan Plateau, with low strength or viscosity, correspond to the banana split model. The strength of the lithosphere in the Tibetan Plateau and other zones of active Cenozoic tectonics mainly derive from the crust, while the strength of the cratonic lithosphere is dominated by that of the mantle lithosphere. The rheological heterogeneity controls the lateral growth of the Tibetan Plateau and the widespread and differential deformation in the East Asian continent.

In-situ Investigation of Slip System Activation, Intergranular Plasticity Transfer, and Deformation Heterogeneity of Al-Zn-Mg-Cu Alloy

In-situ Investigation of Slip System Activation, Intergranular Plasticity Transfer, and Deformation Heterogeneity of Al-Zn-Mg-Cu Alloy

Microstructure and dynamic deformation mechanism of laser powder bed fusion of 316L-containing Ti–6Al–4V with dual-phase heterostructure

In this paper, 316L-containing Ti–6Al–4V alloy was fabricated by laser powder bed fusion (LPBF) through mixing Ti–6Al–4V and 4.5 wt% 316L powders, and the dynamic compressive mechanical properties and deformation mechanism at different strain rates were studied. The results show that the volume fraction of β phase sharply increases from 1.8% (in TC4) to 61.4% (in HST), and micro- and submicron-sized grains coexist in the HST alloy, producing heterostructure in the form of bimodal grain size distribution. The presence of the heterostructure led to superior heterogeneous deformation induced stress, thus facilitating the additional strain hardening and deformation coordinating ability, thus made the HST alloy achieved ultimate compressive stress of ∼1750 MPa and fracture strain of ∼17%, showing excellent comprehensive mechanical properties. Under quasi-static load, the deformation mode of HST alloy is mainly attributed to progressive deformation-induced martensitic transformation. However, at high strain rates, the impact loading inhibited the activation of progressive DIMT, and thus the deformation mode changed to combination of dislocation slipping and deformation twinning.

Heterogeneous phase deformation in a dual-phase tungsten alloy mediated by the tungsten/matrix interface: Insights from compression experiments and crystal plasticity modeling

Tungsten heavy alloy (WHA) is a typical multiphase alloy material consisting of hard tungsten (W) and soft matrix (γ) phases. When loaded, the two phases deform quite differently due to the large difference in their mechanical properties. At present, our understanding of phase deformation and behavior in the multiphase context is relatively poor compared to the single phase case. Such insight is necessary, however, for the design of multiphase alloys having optimal phase microstructure and corresponding material behavior. By combining mechanical testing and crystal plasticity modeling, the relationship between phase microstructure and multiphase alloy deformation behavior is systematically investigated in this work. The results demonstrate that deformation in the W and γ phases is quite different and related to the contrast in material properties between the two phases. Deformation heterogeneity in the multiphase alloy is characterized by the strain gradient near/across the W/γ interface and differences in phase deformation states in relation to the contrast in phase material properties and phase volume fraction. It is found that dislocation pile-up and twinning are the main mechanisms mediating heterogeneous deformation in the region around W/γ interfaces. Based on this insight, a novel design strategy for multiphase alloys is proposed based on optimization of the contrast in phase mechanical properties and the phase volume fractions. This strategy can be employed to design new tungsten alloys and other multi-phase alloys.

Fully automated measurements of echocardiographic mechanical dispersion using deep learning: enhanced prediction of ventricular arrhythmias in a large heart failure cohort

Abstract Background Assessment of left ventricular (LV) myocardial deformation by strain echocardiography has shown improved prognostic value over LV ejection fraction (LVEF). Mechanical dispersion (MD) by strain reflects deformation heterogeneity. Also, MD is a marker of ventricular arrhythmia (VA) that improves risk prediction independently of LVEF in patients with heart failure. However, to analyze MD is time consuming and operator-dependent, and clinical use remains limited. Purpose We aimed to investigate the performance of a novel deep learning (DL) based method for fully automated measurements of MD and evaluate its prognostic utility in patients with heart failure compared to a conventional speckle tracking application. Methods In this prospective multicenter follow up study, the IMPROVE study, we consecutively included patients with recently diagnosed heart failure of all cause with LVEF ≤ 40%. Echocardiograms, ECG, blood samples and clinical data were acquired during index hospitalization. All patients were treated according to contemporary guidelines with optimal medical therapy and revascularization if necessary. Two experienced cardiologists recorded all echocardiograms using Vivid E9 or E95 scanners. We obtained data regarding sudden cardiac death, ventricular arrhythmia and appropriate shock from the ICD from medical records and ICD recordings. The primary endpoint was sudden cardiac death or ventricular arrhythmia (SCD/VA) during follow-up. The prognostic value of DL-based and reference MD measurements was assessed through survival statistics. Results We included 492 patients (mean ± SD 73 ± 13 years old, 32% females). Follow-up time was median (IQR) 5 (3) years. The incidence of SCD/VA was 9% (n=45). Patients with MD ≥70ms had increased risk of SCD/VA both by DL-based and reference measurements (both p <0.001). Furthermore, automated MD measurements using DL had higher prognostic value (HR 4.3) compared to manual reference measurements (HR 3.1) (p <0.001). Conclusion Fully automated measurements of MD using a novel DL method was fast, feasible, and improved prediction of SCD/VA in patients with heart failure and reduced LVEF. The integration of DL measurements may facilitate the clinical implementation of MD assessment and improve risk prediction in echocardiography.

Woven EndoBridge device apposition and compression using Sim&Size virtual simulation correlate with aneurysm occlusion status: a retrospective cohort study

BackgroundVirtual simulation is increasingly used for aneurysm treatment. This study aimed to explore whether mechanical behavior biomarkers of the Woven EndoBridge (WEB) device as computed by Sim&Size simulation software were...

Research on the Heterogeneous Deformation Behavior of Nickel Base Alloy Based on CPFEM

AbstractIn this paper, a crystal plasticity finite element method (CPFEM), considering the grain morphology and orientation, as well as the dislocation density, is used to research the tensile deformation behavior of GH4169 based on Electron Backscatter Diffraction (EBSD). The stress, plastic strain, and dislocation density distributions are obtained for different levels of deformation. Results show that the stress, plastic strain, and dislocation density exhibit obvious heterogeneous plastic deformation, and stress concentration and dislocation pileup mainly occurs near grain boundaries. The initial dislocation density mainly affects the stress–strain curve of the material, and it can obviously effect the yield strength but cannot influence the hardening ability of the material. The total dislocation density increases with plastic strain. However, the texture evolution has no evident change with increasing plastic strain, except for the increase of texture content in Cube (001)[100].

Anisotropy in tensile properties of a high strength metastable β titanium alloy

High strength metastable β titanium alloys are widely employed in the aircraft industry due to their outstanding strength-to-weight ratio. While components can endure complex in-service mechanical loading, the anisotropy in tensile properties has been the subject of limited attention. In this study, its origin was investigated focusing on the role played by millimeter scale β grains as they were recently identified as a source of heterogeneous deformation. Tensile properties of Ti-10V-2Fe-3Al processed via different thermomechanical routes were assessed using multiple sampling directions. In particular, elongation values were observed to vary significantly depending on the testing direction. A combination of SEM, EBSD, µ-CT and in-situ DIC during tensile tests was employed to clarify the underlying causes of this behavior. Substantial differences in strain heterogeneity and localization were found related to features of β grains, including their crystallographic and morphologic orientations. Furthermore, multiple fracture mechanisms were observed to derive from the differences in deformation behavior, and eventually compete to trigger specimen failure. Elongation values are then determined by both the degree of strain heterogeneity and the operating fracture mechanisms. These findings provide a new understanding of the role of the microstructure in the tensile behavior of high strength metastable β titanium alloys.

A model of mechanical loading of the lungs including gravity and a balancing heterogeneous pleural pressure.

Recent years have seen the development of multiple in silico lung models, notably with the aim of improving patient care for pulmonary diseases. These models vary in complexity and typically only consider the implementation of pleural pressure, a depression that keeps the lungs inflated. Gravity, often considered negligible compared to pleural pressure, has been largely overlooked, also due to the complexity of formulating physiological boundary conditions to counterbalance it. However, gravity is known to affect pulmonary functions, such as ventilation. In this study, we incorporated gravity into a recent lung poromechanical model. To do so, in addition to the gravitational body force, we proposed novel boundary conditions consisting in a heterogeneous pleural pressure field constrained to counterbalance gravity to reach global equilibrium of applied forces. We assessed the impact of gravity on the global and local behavior of the model, including the pressure-volume response and porosity field. Our findings reveal that gravity, despite being small, influences lung response. Specifically, the inclusion of gravity in our model led to the emergence of heterogeneities in deformation and stress distribution, compatible with in vivo imaging data. This could provide valuable insights for predicting the progression of certain pulmonary diseases by correlating areas subjected to higher deformation and stresses with disease evolution patterns.

Effect of martensite hardness on mechanical properties and stress/strain-partitioning behavior in ferrite + martensite dual-phase steels

Low-carbon dual-phase (DP) steels composed of ferrite and martensite are widely used in automotive industries due to their good combination of strength and ductility and remarkable strain-hardening ability. Such exceptional mechanical properties of DP steels arise from microstructural deformation heterogeneity due to the different deformation roles of soft ferrite and hard martensite. The present study investigated mechanical properties and local deformation behavior of DP steels having different martensite hardness (strength) using digital image correlation (DIC) technique and in-situ X-ray diffraction (XRD) experiment during tensile deformation. The martensite hardness was reduced by tempering treatment, and its mechanical properties were compared with the as-quenched DP specimen by tensile testing. The tempered DP specimen exhibited reduced strength but enhanced ductility, especially in post-uniform elongation, compared to the as-quenched DP specimen. DIC-strain analysis indicated that the tempering effectively inhibited strain localization, allowing a greater contribution of martensite to plastic deformation. On the other hand, the in-situ XRD analysis revealed that the tempering significantly restricted the stress-increasing potential of martensite. Our results suggest that martensite, acting as a hard domain, plays a significant role in enhancing strain-hardening ability and achieving large uniform elongation due to its high stress-increasing potential. However, the presence of hard martensite also imposes restrictions on post-uniform elongation due to the strong strain localization induced in microstructures.

A mechanism on multiscale heterogenous deformation of nickel-based single crystal superalloys unraveled by time-of-flight neutron diffraction technology

Time-of-flight (TOF) neutron diffraction technology is a powerful tool for acquiring rich diffraction information on the multiscale microstructures and stresses of nickel-based single crystal superalloys. In this study, the tensile deformation behaviors of DD426 superalloy at 760 °C were investigated by TOF neutron diffraction. Combined with electron backscatter diffraction technology, the multiscale deformation heterogeneity between γ/γ' phases and dendritic/interdendritic regions was simultaneously characterized for the first time. Our experiments revealed a significant misorientation difference and the existence of a long-range stress field in the adjacent area between the dendritic and interdendritic regions after tensile deformation at 760 °C. The misorientation angles of crystal planes along the loading direction between the dendritic and interdendritic regions in the deformed alloy was approximately 1.6 ± 0.6° This misorientation can be attributed to the geometrically necessary dislocations (GNDs) concentrated in the adjacent area between the two regions with densities of approximately 1014 m-2. In addition, the lattice strains of both γ' and γ showed a compressive–tensile transition from the dendritic to interdendritic regions, balanced with a long-range stress field. The pile-up GNDs in the adjacent area between the two regions contributed to the existence of long-range stress fields. This study highlights that TOF neutron diffraction technology may reveal well the heterogeneous deformation mechanisms via the formation of both GNDs and pile-up in the adjacent interdendritic/dendritic area of single crystal superalloys.

Coupled cellular automata-crystal plasticity modeling of microstructure-sensitive damage and fracture behaviors in deformation of α-titanium sheets affected by grain size

Concerning the micro-scale deformation of titanium metal sheets, the number of grains in the sheet thickness direction decreases, and their formability exhibits a strong grain size sensitivity. Meanwhile, the twinning-induced dynamic recrystallization (TDRX) associated with grain size significantly affects the fracture behavior in the microforming of titanium sheets. Therefore, an accurate prediction of formability to improve manufacturing reliability remains challenging in the microforming of miniaturized titanium components. To address this issue, an in-depth understanding of the grain size-dependent TDRX behavior and its role in damage and fracture development in the microforming of α-titanium sheets is critical, and a coupled cellular automata-crystal plasticity (CA-CP) modeling framework was thus developed as an approach providing efficient solutions and insightful comprehensions of the issue. For the proposed modeling framework, a kinematic model for TDRX was established and integrated into the CP model by the CA algorithm. As a result, the microstructure evolution caused by TDRX was regarded as an intrinsic part of the constitutive behavior to connect heterogeneous plastic deformation and damage evolution through data transmission between the CP model and the CA algorithm. Additionally, the coupled CA-CP modeling framework was validated with the internal defect morphologies and deformation microstructures characterized by X-ray computed tomography (X-CT) and electron backscattered diffraction (EBSD). Experiment and simulation results demonstrated that the fine recrystallized (DRXed) grains were generated after the twin fragmentation when the dislocation density at twin boundaries reached a threshold of 9.2 × 1013 /m2. After TDRX, the dislocation density and the stress concentration intensity in recrystallization regions were revealed to decrease, accounting for the ductility improvement. Nevertheless, the dislocation density at twin boundaries was determined to decrease with the increase of grain size, leading to less twin fragmentation and the absence of TDRX. The uncoordinated deformation between fine DRXed grains motivated defects to grow spherically into microvoids, thereby preventing premature intergranular cracks along twins/grain boundaries. Ultimately, the deformation microstructures resulting from TDRX with the decrease of grain size were confirmed to control the brittle to ductile fracture transition of α-titanium sheets. The presented modeling framework and simulation procedure were validated to be able to predict the material integrity affected by crystalline microstructure in the deformation of titanium metal sheets.