Local Deformation Research Articles

Dynamic response of axle box bearing for high-speed train considering wheelset flexibility and polygonal wear

In this study, a flexible wheelset was added to a rigid-flexible coupled vehicle dynamics model, in which the axle box bearings are accurately modeled. The measured wheel’s polygon wear profile and Wuhan-Guangzhou track spectrum are used in the model to define the wheel tread and track irregularity, respectively. We conducted a field test on the Wuhan-Guangzhou railway line to validate the model. Then, we investigate how the dynamic properties of the axle box bearing are impacted by the wheelset flexibility and polygonal wear of wheel. We found that the polygonal wheel with a rigid wheelset causes high-frequency vibration in wheelset and axle box, and increases the axle box bearing’s internal contact force. Additionally, the flexible wheelset with a normal wheel tread can alleviate the wheel/rail impact and reduce the axle box’s vertical vibration as well as the axle box bearing’s internal contact force. When the vehicle is running at v = 300 km/h, the excitation frequency caused by the wheel's 20th-order polygon is 576.5 Hz, and the flexible wheelset's 20th-order modal frequency is 577 Hz. The two frequencies are similar, when considering the polygonal wheel and flexible wheelset simultaneously, the wheelset will resonate. And the resonate of wheelset will increase the local deformation of the axle end and deteriorate the bearing operating environment, causing a significant increase in the bearing contact force. Finally, the axle box bearing’s dynamic characteristics are summarized when vehicle velocity varies from 50 to 350 km/h and wheel polygon wear amplitude ranges from 0.01 to 0.05 mm.

Global and Local Deformation Analysis of Mg-SiC Nanocomposites: Digital Image Correlation (DIC) and Representative Volume Element (RVE) Techniques

Improving the ductile deformation behavior of Mg-SiC nanocomposites without compromising strength is critical to enhancing their mechanical properties. Mg-SiC nanocomposites are produced through mechanical milling, cold isostatic pressing, sintering, and hot extrusion processes. This study investigates the uniaxial stress–strain response and deformation behavior of the Mg-SiC nanocomposite compared to pure Mg samples with and without the milling process. The deformation behavior was investigated by two-dimensional (2D) digital image correlation (DIC) at two macroscopic and microscopic scales, employing light micrographs and in situ loading samples, respectively, in the scanning electron microscope. Compared to the pure Mg samples, the mechanical test results demonstrated a significant improvement in strength (80 MPa) and fracture strain (23.5%) of the Mg-SiC nanocomposite. The three-dimensional (3D) representative volume element (RVE) model revealed the particle dispersion effect on the mechanical properties of the nanocomposite. The RVE results demonstrate ductile deformation behavior in the sample with homogenous dispersion of SiC particles compared with the heterogeneous dispersion of SiC particles in Mg-SiC nanocomposite. The results demonstrated a good agreement between DIC and RVE predictions for Mg-SiC nanocomposites across macro- and microscales.

Ballistic perforation of aramid laminates: Projectile nose shape sensitivity

The influence of projectile shape on the ballistic properties and mechanism of aramid laminates is investigated through experiments and simulations. Three types of projectiles (blunt, hemispherical, and ogival) are used to obtain ballistic curves. The dynamic penetration process, deformation and damage characteristics of the targets are analyzed. A three-dimensional finite element model is established, and good agreement is observed between the simulation and test results. The findings demonstrate that projectile shape significantly impacts the ballistic response of aramid laminates. As the projectile transitions from blunt and hemispherical to ogival, the ballistic limiting velocity decreases continuously, the area of target plate deformation and damage decreases, and the occurrence of delamination becomes less pronounced. And the energy dissipation through local damage, elastic deformation and overall motion of the aramid material is decreasing and the energy dissipation through friction is increasing.

Integral thermo-mechanical performance analysis of helium-cooled T-tube divertor

To verify the mechanical properties of the helium-cooled T-tube divertor, based on the thermal hydraulic optimization of the T-tube divertor, a preliminary analysis was conducted through a combination of elastic and elasto-plastic analysis.The results show that for the M-type damage mode, the T-tube divertor exhibits a small-scale plastic yielding phenomenon, but this has no effect on the overall divertor. The T-tube divertor has local necking deformation but does not fail due to immediate local fracture, and the T-tube divertor has no creep rupture. For the C-type damage mode, the plastic strain of the T-tube divertor is not accumulated under cyclic loading, but in the fatigue analysis, the life of the divertor does not meet the design standards and further optimization is needed.The conclusion shows that the optimized helium-cooled T-tube divertor has good thermo-mechanical properties, and the safety of the helium-cooled T-tube divertor unit can be guaranteed.

Treatment of patients with posttraumatic deformities of the thoracolumbar spine using Schwab 5 osteotomy through combined and posterior approaches

Objective. To analyze the results of surgical treatment of patients with rigid posttraumatic deformities of the thoracolumbar spine operated on using Schwab 5 osteotomy through combined and posterior approaches.Material and Methods. A retrospective cohort study was conducted. Study group included 60 patients (m/f = 25/35). Median age was 48 (26–58) years, median time since injury was 11 (9–14) months, and minimum follow-up period was 2 years. A two-stage intervention with resection of the vertebral body, correction of the deformity, and placement of an interbody implant through the anterior approach followed by final fixation through the posterior approach (VCRa+p group) was performed in 29 cases. Vertebral body resection through the posterior approach with correction of the deformity, installation of an interbody implant, and rigid transpedicular fixation (VCRp group) was performed in 31 cases. In all patients, the magnitude of correction was assessed, as well as the following parameters: frontal balance, sagittal balance, thoracic kyphosis, lumbar lordosis, pelvic incidence, sacral slope and pelvic tilt. The results of treatment were evaluated in dynamics by the level of pain syndrome (VAS) and quality of life (ODI), as well as based on the analysis of postoperative complications.Results. The groups were comparable in terms of gender, age, magnitude of the kyphotic component of the deformity, level of pain syndrome and degree of initial neurological deficit (p > 0.05). Correction of the deformity kyphotic component was significantly better in patients in the VCRp group compared to those in the VCRa+p group (p = 0.036). Both groups showed a significant decrease in the level of pain syndrome 3 months after surgery. However, further follow-up showed a tendency for back pain to increase on average one year after surgery in the VCRa+p group. A total of 67 complications were revealed in 40 (66.7 %) patients. Herewith, in the early postoperative period there were 55 complications in 31 patients, and in the late period there were 12 complications in 9 patients. Analysis of early complications showed a higher incidence of anemia (p = 0.002) and liquorrhea (p = 0.017) in the VCRp group compared to those in the VCRa+p group. The incidence of long-term complications did not differ significantly between groups (p = 0.866). An increase in back pain in the long-term period was observed in 12 (41.4 %) patients of the VCRa+p group and in 4 (12.9 %) patients of the VCRp group. Analysis of risk factors for this condition showed a tendency for back pain to increase in the long-term period in patients with residual local deformity against the background of low pelvic index values.Conclusion. Correction of the kyphotic component of deformity was significantly better in patients of the VCRp group, which was accompanied by greater surgical trauma and incidence of early postoperative complications. The tendency of patients’ quality of life to deteriorate in the long-term follow-up period seems to be related to the occurrence of pain syndrome in the lumbar spine in patients with residual kyphotic deformity against the background of initially low compensatory capabilities.

Behaviour of embedded H-profile balcony-to-slab connection

This paper investigates experimentally and numerically the behaviour of a balcony-to-slab connection made by an H-profile embedded in the concrete slab. A large-scale test was performed on a specimen of the connection system in order to determine the moment-bearing capacity, the deformation behaviour, the cracking patterns, the distribution of the bending moment along the axis of the embedded steel H-profile as well as the failure mode of the connection system. The test results showed that the failure mode was governed by the concrete shear of the slab. In addition, a 3D finite element model of the experimental test was also carried out and successfully validated against the experimental results. For a practical design of the connection system, a model based on Timoshenko beam on elastic foundation (BEF) was investigated and verified against the results obtained from the validated FE model. The Winkler modulus of the BEF model was determined by considering the local deformation of the concrete based on a strut-and-tie model. The results demonstrate that the BEF model with this value of the Winkler modulus provides a conservative estimation of the shear and bending forces applied to both the embedded H-profile and the concrete cross-sections. This method is a first tentative design basis using linear elastic theory for such a system.

Earth Observation Capacity of the National Geoinformation Center of Bulgaria as Part of the Tools for Geo- and Anthropogenic-Hazard Management in EPOS

Exploring the nature of the Earth system and its multi-scale architecture requires an integrated symbiotic approach not only to understand our planet but also to reveal the hazards and footprints of their events on human life. Following the conceptual model of the European Plate Observing System (EPOS) we integrate a variety of research to obtain a multilateral use of geoinformation for scientific and practical purposes. In 2018, we started building a Bulgarian distributed scientific infrastructure called the National Geoinformation Center, aiming to provide data, products, and expertise to predict and prevent natural and anthropogenic risks and disasters, as well as environmental changes. The present paper demonstrates the capabilities of seismological, Global Navigation Satellite System (GNSS), geomagnetic and multi-scale laboratories (MSL) in Bulgaria that participate to the respective thematic core services of EPOS. More than 40 seismological stations register and transmit data in real time through the operational center of the Bulgarian Seismological Network. Data from 18 GNSS stations, part of the National GNSS network, are officially registered in the EPOS GNSS Data Gateway. Data and products are available via the EPOS GNSS Product Portal for interested users. Panagjurishte geomagnetic observatory (PAG) provides real time variations and long-period data series for the Earth’s magnetic field. The Palaeomagnetic Laboratory at the National Institute of Geophysics, Geodesy and Geography (NIGGG) participates in MSL with its unique facilities for paleo-, archeo- and environmental magnetism studies. Four case studies are presented to illustrate best practices for utilizing the data collected. The analysis of seismicity in a region of a long-time exploited salt deposit is upgraded with GNSS data to reveal the reason for crustal movements in the region. The results show that the majority of the seismic events took place in the upper part of the Earth’s crust at a depth of up to 5 km, where the salt body is buried. The observed significant local deformations of the Earth’s surface are very likely related to the technological process of deposit exploitation. A recent model of the geomagnetic declination over the Bulgarian territory is also presented. It tracks the variation of the regional magnetic field from 2015 to 2020 and adds short-wavelength signals from the secular network observations. Last but not least, the application of a mineral magnetic laboratory analysis along the depth of a Holocene soil profile is demonstrated. Results reveal the soil evolution in response to environmental changes adding a new magnetic proxy parameter for more precise identification and characterization of the soil formation processes.

Analytical study on the dynamic mechanical behaviours of foam-core sandwich plate under repeated impacts

The foam-core sandwich structures are probably subjected to repeated impact loadings in engineering applications, resulting in structural plastic deformation and accumulative damage. A valuable analytical approach is needed to predict the accumulative plastic deformation of foam-core sandwich structures under repeated impacts. In this paper, an analytical model of the dynamic responses of foam-core sandwich plates under repeated impacts is proposed using the circumscribing yield locus and the inscribing yield locus based on the rigid-perfectly plastic theory. By employing the principle of energy dissipation rate balance, the analytical expressions of structure permanent deformation and peak force are obtained from the iteration of initial conditions. In addition, polyvinyl chloride (PVC) foam has steady chemical properties and corrosion resistance, which can better adapt to the practical environment and meet the needs of structural protection. To validate the proposed analytical model, the repeated impact dynamic mechanical behaviours of PVC foam-core sandwich plates were experimentally and numerically studied. Results show that theoretical results such as the permanent deformation, peak force, and deformation modes of foam-core sandwich plates under repeated impacts are in good agreement with experimental and numerical results. With the increase in impact numbers, the global bending deformation and local indentation deformation of facesheets increase, the PVC foam core layer is constantly being compressed, and the bottom facesheet plays an increasingly important part in the repeated impact energy absorption with a maximum value of 29.20 %.

Effect of thermal ageing on the deformation behaviour of ferrite and austenite in a duplex stainless steel: Micropillar characterisation and dislocation density modelling

The deformation behaviour of the austenitic and ferritic phases in an aged duplex stainless steel is investigated experimentally and numerically. The effect of the ferritic phase’s spinoidal decomposition during thermal ageing on the mechanical behaviour of the alloy is studied through micropillar compression tests on the individual single crystal phases before and after ageing, and APT and TEM investigations of the decomposed ferrite and corresponding dislocation structures. Dislocation density-based crystal plasticity models are formulated for the austenitic and ferritic phases, and calibrated from the measured micropillars responses.A considerably higher and more homogeneously distributed initial dislocation density is observed in the austenite, resulting in a more homogeneous deformation of the austenitic micropillars than the ferritic ones. The spinoidal decomposition of the ferrite leads to a considerable increase of its initial flow stress. The strengthening effect of thermal ageing and the resulting localised deformation response of the aged ferritic micropillars are correctly described by the crystal plasticity results, which required a higher initial obstacle (dislocations + inter-phases of the newly formed α′ domains) density to dislocation motion. Moreover, a strong size effect was observed on the behaviour of the as-received and aged austenitic and as-received ferritic micropillars, but not in the aged ferritic ones. Such contrasting behaviour originates from the fact that, for the size sensitive cases, the dislocation mean free path is controlled by the mean micropillar diameter, whereas in the aged ferrite micropillars, it is by the ∼ 5 nm wide Cr-rich domains within the spinoidal decomposed ferrite.

Influence of basement high and detachment on the kinematics of a fold-and-thrust belt in the central South Yellow Sea Basin, China: Insights from analog modeling

A fold-and-thrust belt (FTB) characterized by a basement high and detachment layer was developed beneath the South Yellow Sea Basin, an important petroleum exploration target. In the central basin, magnetic anomalies have revealed the basement high developed under the Laoshan Uplift. Seismic reflection together with drilling data have revealed the Lower Silurian Gaojiabian Formation exceeding ∼500 m acting as a low-cohesion detachment layer. However, the influence of these features on regional structures and the consequent hydrocarbon preservation conditions remains unclear. This study examined the kinematic characteristics and deformation localization associated with the basement high and intermediate detachment, respectively and collectively, using four sandbox models and particle velocity analysis under the FTB framework. Model 1, the reference, used pure quartz sand without either feature. Model 2 examined the role of the intermediate detachment using glass microbeads, finding very limited effect in producing typical thin-skinned FTB. Model 3 considered the basement high, finding that it strongly constrained the deformation regime of the wedge. Model 4 examined both features and suggested combined influence on FTB deformation processes. In Model 2, with the absence of a pre-existing basement high, the intermediate detachment did not play a role in FTB deformation. In Model 3, with the absence of an intermediate detachment, deformation propagated along the surface of the basement high after reaching its edge. In Model 4, shortening propagated upward along the edge of the basement high and then into the intermediate detachment; moreover, comparable structural geometry to the prototype was produced, including both thick- and thin-skinned FTBs in nature. The results indicate that in the central South Yellow Sea Basin, structural layers between the basement high and detachment should similarly experience weak deformation; thus, good hydrocarbon preservation conditions can be expected there. This study is of significant importance to guide future petroleum exploration in the central South Yellow Sea Basin.

Effectiveness of one-stage posterior eggshell osteotomy and long-segment pedicle screw fixation for ankylosing spondylitis kyphosis combined with acute thoracolumbar vertebral fracture

To explore the safety and effectiveness of one-stage posterior eggshell osteotomy and long-segment pedicle screw fixation in the treatment of ankylosing spondylitis kyphosis combined with acute thoracolumbar vertebral fracture. A clinical data of 20 patients with ankylosing spondylitis kyphosis combined with acute thoracolumbar spine fracture, who were treated with one-stage posterior eggshell osteotomy and long-segment pedicle screw fixation between April 2016 and January 2022, was retrospectively analyzed. Among them, 16 cases were male and 4 cases were female; their ages ranged from 32 to 68 years, with an average of 45.9 years. The causes of injury included 10 cases of sprain, 8 cases of fall, and 2 cases of falling from height. The time from injury to operation ranged from 1 to 12 days, with an average of 7.1 days. The injured segment was T 11 in 2 cases, T 12 in 2 cases, L 1 in 6 cases, and L 2 in 10 cases. X-ray film and CT showed that the patients had characteristic imaging manifestations of ankylosing spondylitis, and the fracture lines were involved in the anterior, middle, and posterior columns and accompanied by different degrees of kyphosis and vertebral compression; and MRI showed that 12 patients had different degrees of nerve injuries. The operation time, intraoperative bleeding, intra- and post-operative complications were recorded. The visual analogue scale (VAS) score and Oswestry disability index (ODI) were used to evaluate the low back pain and quality of life, and the American spinal cord injury association (ASIA) classification was used to evaluate the neurological function. X-ray films were taken, and local Cobb angle (LCA) and sagittal vertical axis (SVA) were measured to evaluate the correction of the kyphosis. All operations were successfully completed and the operation time ranged from 127 to 254 minutes (mean, 176.3 minutes). The amount of intraoperative bleeding ranged from 400 to 950 mL (mean, 722.5 mL). One case of dural sac tear occurred during operation, and no cerebrospinal fluid leakage occurred after repair, and the rest of the patients did not suffer from neurological and vascular injuries, cerebrospinal fluid leakage, and other related complications during operation. All incisions healed by first intention without infection or fat liquefaction. All patients were followed up 8-16 months (mean, 12.5 months). The VAS score, ODI, LCA, and SVA at 3 days after operation and last follow-up significantly improved when compared with those before operation ( P<0.05), and the difference between 3 days after operation and last follow-up was not significant ( P>0.05). The ASIA grading of neurological function at last follow-up also significantly improved when compared with that before operation ( P<0.05), including 17 cases of grade E and 3 cases of grade D. At last follow-up, all bone grafts achieved bone fusion, and no complications such as loosening, breaking of internal fixation, and pseudoarthrosis occurred. One-stage posterior eggshell osteotomy and long-segment pedicle screw fixation is an effective surgical procedure for ankylosing spondylitis kyphosis combined with acute thoracolumbar vertebral fracture. It can significantly relieve patients' clinical symptoms and to some extent, alleviate the local kyphotic deformity.

A Soft, Adhesive Self-Healing Naked-Eye Strain/Stress Visualization Patch.

Learning about the strain/stress distribution in a material is essential to achieve its mechanical stability and proper functionality. Conventional techniques such as universal testing machines only apply to static samples with standardized geometry in laboratory environment. Soft mechanical sensors based on stretchable conductors, carbon-filled composites, or conductive gels possess better adaptability, but still face challenges from complicated fabrication process, dependence on extra readout device, and limited strain/stress mapping ability. Inspired by the camouflage mechanism of cuttlefish and chameleons, here an innovative responsive hydrogel containing light-scattering "mechano-iridophores" is developed. Force induced reversible phase separation manipulates the dynamic generation of mechano-iridophores, serving as optical indicators of local deformation. Patch-shaped mechanical sensors made from the responsive hydrogel feature fast response time (<0.4 s), high spatial resolution (≈100µm), and wide dynamic ranges (e.g., 10-150% strain). The intrinsic adhesiveness and self-healing material capability of sensing patches also ensure their excellent applicability and robustness. This combination of chemical and optical properties allows strain/stress distributions in target samples to be directly identified by naked eyes or smartphone apps, which is not yet achieved. The great advantages above are ideal for developing the next-generation mechanical sensors toward material studies, damage diagnosis, risk prediction, and smart devices.

Formation of expanded phases in ferritic stainless steel nitrided at low temperatures

Nitriding treatments at low temperatures (<450 °C) are receiving increasing interest for the surface engineering of stainless steels due to the possibility of producing supersaturated solid solutions of nitrogen in the iron-based lattices, known as “expanded” phases. In this study this treatment was applied to AISI 430 ferritic stainless steel with the aim of clarifying the characteristics of the modified surface layer, and in particular the microstructure and phase composition. The formation of expanded ferrite caused high compressive stresses, so that local plastic deformation phenomena occurred, observable as microstructural changes (slip lines, grain swelling) both at the surface and in the section of the samples. Moreover, the formation of a nitrogen-containing hexagonal close-packed phase, dissimilar to ε-nitride, was reported for the first time for low-temperature nitrided ferritic stainless steels. It is suggested that this phase might be a N-rich expanded ε′-martensite, which formed from expanded ferrite due to a bcc-to-hcp displacive transformation and it remained in the microstructure owing to the residual compressive stresses and nitrogen and chromium solubilization. The presence of this phase contributed to the increase of surface microhardness together with expanded ferrite. The assessment of the corrosion behaviour in 3.5 wt% NaCl aerated solution by means of electrochemical impedance spectroscopy analysis and potentiodynamic measurements showed that, when the modified surface layer consisted only of expanded ferrite, impedance values and corrosion potential had a marked increase and corrosion current density decreased, as compared to those of the untreated steel, suggesting an enhancement of the resistance to general corrosion. On the contrary, when a heterogeneous modified layer formed (expanded ferrite and N-rich expanded ε′-martensite), a worsening of corrosion resistance was observed.

Numerical validation of fatigue properties and investigation of local deformation of heat-affected zones in P91 steel’s weld joint

The low cycle fatigue (LCF) behavior of P91 steel weld joint (WJ), prepared by gas tungsten arc welding, has been investigated both experimentally and numerically. However, due to the smaller size and complex geometry of various zones of the WJ, the experimental investigation of the local fatigue behavior of different sub-regions of the heat-affected zones (HAZ) could not be made. Hence, the sub-regions of the WJ were reproduced at bulk scale by physical-thermal simulation (PTS) (i.e., heat treatment) to study the LCF behavior of the individual zones of P91 WJ. In the literature, the accuracy of such physical-thermally simulated bulk-scale specimens, which correspond to different sub-regions in the weld joint, is confirmed by comparing the microstructures and microhardness. In this article, a new method, based on the LCF experiment and finite element simulation, is proposed to validate the PTS method and the fatigue properties of the sub-regions of the weld joint. The simulation accurately predicted the failure location and also the most vulnerable sub-region within the WJ, as observed experimentally. Moreover, significant ratchetting and heterogeneous deformation were observed in the sub-regions of the WJ.

Achieving near zero-hysteretic superelasticity in a Ni43Fe18Ga27Co12 single-crystalline microwire via Lüders-like phase transformation

Ni43Fe18Ga27Co12 single-crystalline microwires directly fabricated by the Taylor liquid drawing method show the nature of a strong first-order martensitic transformation under external stress or load-biased temperature cycling. By eliminating the nucleation energy barrier through localized plastic deformation, a fully recoverable superelastic strain approaching 11 % with negligible hysteresis is achieved in the course of tensile deformation. Based on in-situ synchrotron high-energy X-ray diffraction analysis, the mechanism of nearly non-hysteretic transformation is unraveled as a sharp, Lüders-like phase transformation. It is found that a single martensitic domain propagates continuously in a monolithic fashion under superelastic cycling with poor crystallographic compatibility of λ2 = 0.950 and small volume change of ∆V = -0.17 % accompanying martensitic transformation. We attributed such near zero-hysteretic transformation characteristics to combining conditions of low crystal defect density, high nucleation barriers but without continual nucleation events, flexibility of the microwire, and small volume change.

Elastic and inelastic major-axis flexural buckling of cellular steel columns

This study investigates the elastic and inelastic major-axis flexural buckling of cellular steel columns. Based on the stationary principle of potential energy, the existing elastic buckling load equation is refined to incorporate the local bending deformations at web posts. The column strength curve for determining the critical loads is then derived. For the elastic buckling, the refinement provides a significant improvement. For the inelastic buckling, the effects of residual stresses and initial geometric imperfections on the column strength are examined by the validated nonlinear finite element (FE) models. The initial geometric imperfection amplitudes of L/300 and L/500, where L is the column length, are recommended for global buckling of cellular steel columns fabricated from the parent steel shapes with h/b ≤ 1.2 and h/b > 1.2, respectively, where h/b is the depth-to-width ratio of the parent steel shapes. The developed column strength curve conservatively predicts the major-axis flexural buckling strength of practical cellular steel shapes, with an average prediction-to-FE buckling stress ratio of 0.97. A comparison also shows that the current EC3 and AISC360 equations are applicable for predicting the strength of practical cellular columns, provided that the refined elastic buckling load is adopted.

Rapid acquisition of digital fingerprints of Ti-6Al-4V macrotexture from machining force measurement data

Titanium alloys display anisotropic deformation properties due to the hexagonal close-packed (hcp) crystal structure of the α-phase. When subjected to localised deformation during machining, this behaviour influences fluctuations in the cutting force response of the material as the tool encounters grains of different orientations. In this research, cutting force signals acquired during face turning of Ti–6Al–4V possessing a lamellar α colony structure have been spatially mapped demonstrating the ability to identify microstructural features such as prior-β grain boundaries, grain boundary α, and α colonies. Measured cutting forces have been correlated to texture using orientation information acquired from large area EBSD analysis. A relationship between the misalignment of the crystallographic a slip vector with respect to the cutting direction and the passive cutting force response has been established, demonstrating a rise in cutting forces as this misalignment is increased. This novel approach to in-process materials evaluation offers manufacturers the potential of a powerful digital quality assurance tool, with the results presented here demonstrating the possibility for rapid characterisation of entire component surfaces, revealing microstructural features, and inferring the crystallographic orientation of macrotextured regions in Ti–6Al–4V.

Spatially Programmable Architected Materials Inspired by the Metallurgical Phase Engineering.

Programmable architected materials with the capabilities of precisely storing predefined mechanical behaviors and adaptive deformation responses upon external stimulations are desirable to help increase the performance and the organic integration of materials with surrounding environments. Here, a new approach inspired by the physical metallurgical principles is proposed to allow the materials designers to not only enhance the global strength but also precisely tune mechanical properties (such as strength, modulus, and plastic deformation) locally in architected materials to create a new class of intelligent mechanical metamaterials. Such programmable materials not only have high strength and plastic deformation stability but also the ability to regulate the local deformation states and spatially control the internal propagation of deformation. This innovative approach also provides new and effective ways to enhance the adaptivity of the materials thanks to responsive strengths that not only make the materials increasingly stronger but also allow threshold-based adaptive responses to external loading.

InSAR Monitoring Using Persistent Scatterer Interferometry (PSI) and Small Baseline Subset (SBAS) Techniques for Ground Deformation Measurement in Metropolitan Area of Concepción, Chile

InSAR capabilities allow us to understand ground deformations in large metropolitan areas, this is key to assessing site conditions in areas in an inherently expanding context. The multi-temporal interferometry of SAR data records ground surface displacement velocities over large metropolitan areas, identifying anomalous and potential geological hazards. The metropolitan city of Concepción, Chile, is an alluvial basin in one of the world’s most seismically active subduction zones, where many subduction earthquakes have occurred throughout history. In this study, we monitored the deformations of the ground surface in the metropolitan area of Concepción using two interferometric techniques, the first being Persistent Scatterer Interferometry (PSI) and the second, the Small Baseline Subset (SBAS) technique. To do this, we have used the same Sentinel-1 dataset, obtaining ground movement rates between 2019 and 2021. The velocities were aligned with the GNSS station available in the area. Ground deformation patterns show local deformations depending on factors such as soil type and heterogeneity, and regional deformations due to geographical location in the subduction area. Our results highlight the similarity of the deformation rates obtained with different processing techniques and have also allowed us to identify areas of deformation and compare them to site conditions. These results are essential to evaluate ground conditions and contribute to urban planning and risk management in highly seismic areas.

Simulation of fracture in vascular tissue: coupling a continuum damage formulation with an embedded representation of fracture

AbstractThe fracture of vascular tissue, and load-bearing soft tissue in general, is relevant to various biomechanical and clinical applications, from the study of traumatic injury and disease to the design of medical devices and the optimisation of patient treatment outcomes. The fundamental mechanisms associated with the inception and development of damage, leading to tissue failure, have yet to be wholly understood. We present the novel coupling of a microstructurally motivated continuum damage model that incorporates the time-dependent interfibrillar failure of the collagenous matrix with an embedded phenomenological representation of the fracture surface. Tissue separation is therefore accounted for through the integration of the cohesive crack concept within the partition of unity finite element method. A transversely isotropic cohesive potential per unit undeformed area is introduced that comprises a rate-dependent evolution of damage and accounts for mixed-mode failure. Importantly, a novel crack initialisation procedure is detailed that identifies the occurrence of localised deformation in the continuum material and the orientation of the inserted discontinuity. Proof of principle is demonstrated by the application of the computational framework to two representative numerical simulations, illustrating the robustness and versatility of the formulation.