Initial Failure Research Articles

Artificial Intelligence‐Based Detection of Local Spots in Network Materials Prone to Mechanical Failure

ABSTRACTPredicting the failure of a noncrystalline solid such as silica glass is challenging due to the complex fracture phenomenon. Failure originates from particular local zones where the atomic structure is highly susceptible to local rearrangement. The local yield stress (LYS) method predicts such locations of plastic events during external deformation. Despite the precise prediction accuracy of the location of the failure initiation, the LYS method requires substantial computational resources as it evaluates each local zone separately for rearrangement and is time‐consuming. Owing to new age development in artificial neural networks, a relation can be established between the plastic events and the atomic structure. In this study, a neural network is trained to identify this relation and, hence, predict the locations of atomic rearrangements. This approach results in a heatmap indicating soft spots that highly correlate with elementary events of fracture and allows for reliable incorporation of structural identification to coarser mechanical frameworks that need local information for a physically meaningful description. The advantage of this method is that it can be trained on a specific material and can predict the local soft spots for unseen structural information without the need for multiple time‐consuming molecular simulations.

Modeling and analysis of failure initiation and progression of 3D braided composites: a multi-region multi-cell approach

Accurate modeling and analysis are keys to obtaining precise failure behavior of advanced composites with manufacturing details. However, existing models lack a unique shape and fail to account for the intricate yarn path and manufacturing nuances. The current work emphasizes multi-region-based multi-cell models to analyze the damage initiation and progression behavior of 3D braided polymer composites under tensile loading. The progressive damage model is applied with Hashin 3D UMAT and maximum stress failure criteria for the modeled fiber bundle and matrix in the finite element analysis framework. Also, the effects of the void are considered to incorporate manufacturing-induced variations. The damage initiation and progression results are shown with stress-strain curves and verified with existing literature. It is obtained that the observed damage varies according to the different regions of the composite structure. The significant advantage of the current work is that it emphasizes modeling and failure analysis that accounts for manufacturing intricacies, enabling accurate representation of complex advanced composites using a computationally efficient small-scale model. Results and discussions indicate that this approach can be utilized to predict the failure of 3D complex shape composites efficiently.

Segregation at prior austenite grain boundaries: The competition between boron and hydrogen

The interaction between boron and hydrogen at grain boundaries has been investigated experimentally and numerically in boron-doped and boron-free martensitic steels using thermal desorption spectrometry (TDS) and ab initio calculations. The calculations show that boron and hydrogen are attracted to grain boundaries but boron can repel hydrogen. This behavior has also been observed using TDS measurements, with the disappearance of one peak when boron is incorporated into the microstructure. Additionally, the microstructure of both steels has been studied through electron backscattered diffraction, synchrotron X-ray measurements, and correlative transmission Kikuchi diffraction-atom probe tomography measurements. While they have a similar grain size, grain boundary distribution, and dislocation densities, pronounced boron segregation into PAGBs is observed for boron-doped steels. It indicates that boron in PAGBs is responsible for the disappearance of the TDS peaks for the boron-doped steel. Then, the equilibrium hydrogen concentration in different trapping sites has been evaluated using the Langmuir–McLean approximation. This thermodynamic model shows that the distribution of hydrogen is identical for all traps when the total hydrogen concentration is low for boron-free steel. However, when it increases, traps of the lowest segregation energies (mostly PAGBs) are firstly saturated, which promotes failure initiation at this defect type. This finding partially explains why PAGBs are the weakest microstructure feature when martensitic steels are exposed to hydrogen-containing environments.

A FEM-based model for failure initiation in the microstructure of gray cast iron under uniaxial compression

PurposeThe purpose of this study was to validate the feasibility of the proposed microstructure-based model by comparing the simulation results with experimental data. The study also aimed to investigate the relationship between the orientation of graphite flakes and the failure behavior of the material under compressive loads as well as the effect of image size on the accuracy of stress–strain behavior predictions.Design/methodology/approachThis paper presents a microstructure-based model that utilizes the finite element method (FEM) combined with representative volume elements (RVE) to simulate the hardening and failure behavior of ferrite-pearlite matrix gray cast iron under uniaxial loading conditions. The material was first analyzed using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) to identify the different phases and their characteristics. High-resolution SEM images of the undeformed material microstructure were then converted into finite element meshes using OOF2 software. The Johnson–Cook (J–C) model, along with a damage model, was employed in Abaqus FEA software to estimate the elastic and elastoplastic behavior under assumed plane stress conditions.FindingsThe findings indicate that crack initiation and propagation in gray cast iron begin at the interface between graphite particles and the pearlitic matrix, with microcrack networks extending into the metal matrix, eventually coalescing to cause material failure. The ferritic phase within the material contributes some ductility, thereby delaying crack initiation.Originality/valueThis study introduces a novel approach by integrating microstructural analysis with FEM and RVE techniques to accurately model the hardening and failure behavior of gray cast iron under uniaxial loading. The incorporation of high-resolution SEM images into finite element meshes, combined with the J–C model and damage assessment in Abaqus, provides a comprehensive method for predicting material performance. This approach enhances the understanding of the microstructural influences on crack initiation and propagation, offering valuable insights for improving the design and durability of gray cast iron components.

WASTE EGGSHELL AND SAWDUST AS REINFORCEMENTS FOR SUSTAINABLE POLYESTER COMPOSITES: MECHANICAL CHARACTERIZATION AND ENVIRONMENTAL DURABILITY ASSESSMENT

This research endeavor undertakes an experimental investigation into the bending and tensile properties of polyester composites reinforced with waste eggshell powder and sawdust particles at 35 wt.%. Valorizing these waste materials as reinforcements contributes to sustainable practices, waste minimization, and environmental pollution mitigation. Composite samples were fabricated using hand lay-up and compression molding techniques. The effects of environmental exposure to water, acidic, and basic media immersion on the mechanical performance were evaluated to assess durability. Experimental characterization through tensile and three-point bending tests determined mechanical properties, stress-strain behavior, and failure mechanisms. Additionally, finite element analysis (FEA) simulations complemented the experiments by providing insights into stress distributions, deformations, and potential failure initiation sites within the composites under flexural loading. The computational models accurately captured the reinforcing effects of the waste materials and the degradation induced by environmental exposure, validating the experimental trends. Incorporating waste natural fibers significantly enhanced polyester's bending strength by 140% (sawdust) and 75% (eggshell), and tensile strength by 13% (sawdust) and 10% (eggshell). However, environmental exposure degraded properties to varying extents, with water immersion reducing tensile strength by 63% (sawdust) and 3% (eggshell), and flexural strength by 63% (sawdust) and 3% (eggshell). The acidic medium caused 58% (sawdust) and 23% (eggshell) reductions in tensile strength, and similar flexural strength degradations. Strikingly, the basic medium decreased eggshell composite tensile strength by 170% and flexural strength by 6%, while sawdust composite strengths declined by 44%.

Outpatient Worsening Heart Failure in Patients with Transthyretin Amyloidosis with Cardiomyopathy in the HELIOS-B Trial.

Transthyretin amyloidosis with cardiomyopathy (ATTR-CM) is a fatal disease, caused by misfolded transthyretin depositing as amyloid fibrils in the heart. Because disease progression is common, practical and sensitive methods are needed to monitor patients and optimize treatment decisions. Outpatient worsening heart failure (HF) (oral loop diuretic intensification or initiation) is simple to assess and has been shown to be prognostic of mortality in patients with ATTR-CM. We aimed to assess the clinical and prognostic significance of and the effect of vutrisiran treatment on outpatient worsening HF in patients with ATTR-CM from the HELIOS-B trial. Associations between outpatient worsening HF and a composite of all-cause mortality and recurrent cardiovascular (CV) events (CV hospitalizations and urgent HF visits), all-cause mortality, and other disease progression-related endpoints were evaluated. The impact of vutrisiran over 36 months on outpatient worsening HF and an expanded composite of all-cause mortality, recurrent CV events, and outpatient worsening HF was also assessed. Overall, 321 patients (49.1%) had ≥1 outpatient worsening HF, 245 (37.5%) had ≥1 CV event(s), and 120 (18.3%) died; 237 patients (36.2%) had no events. Patients with outpatient worsening HF had an increased risk of all-cause mortality and CV events (hazard ratio [HR]: 2.58; 95% confidence interval [CI]: 2.04-3.27) and all-cause mortality (HR: 2.45; 95% CI: 1.70-3.52), as well as a greater deterioration in 6-minute walk test distance and Kansas City Cardiomyopathy Questionnaire-Overall Summary score, and a greater increase in N-terminal prohormone of B-type natriuretic peptide. In recurrent event analyses over the double-blind period, vutrisiran versus placebo reduced the rate of outpatient worsening HF (relative rate ratio: 0.66; 95% CI: 0.56-0.78). Vutrisiran also reduced the risk of the composite of all-cause mortality, CV events, and outpatient worsening HF versus placebo (HR: 0.69; 95% CI: 0.57-0.83). Outpatient worsening HF was frequent in patients with ATTR-CM in HELIOS-B, and was associated with increased mortality, and reduced by vutrisiran.

Puck 3D-based modeling and validation of progressive failure in instrumented glass fiber-reinforced polypropylene via the split-disk test

This study analyzes the mechanical behavior and damage progression of filament-wound thermoplastic composite rings, focusing on the effects of embedded fiber optic (FO) sensors. Utilizing a split-disk test, the study evaluates both experimental and numerical approaches to examine the impact of FO sensors in glass fiber-reinforced polypropylene composite rings. The split-disk test is employed to measure key mechanical properties such as hoop tensile strength, stiffness and failure strain using strain gauges and 3D Digital Image Correlation (DIC). The research specifically examines two extreme configurations of FO sensor placement: parallel and perpendicular to the reinforced fibers. The objective is to propose sensor integration that minimizes potential negative effects on the material's properties. Both instrumented and non-instrumented samples are analyzed numerically and experimentally. The experimental phase involves detailed mechanical characterization using the split-disk test, while the numerical approach uses a developed UMAT finite element model based on the 3D Puck failure criterion and an element weakening method for progressive failure analysis. The numerical models adopt real microstructural details according to optical microscopic analysis. The study concludes that parallel embedded FO sensors are preferable as they enhance the ultimate strength to failure and avoid creating resin-rich zones near the sensor, thereby improving the overall mechanical performance of the composite rings. The 3D Puck failure criterion combined with the element weakening method provides accurate predictions of fiber failure initiation and growth in the composite rings.

A novel continuum damage evolution model based on the concept of damage driving force for unidirectional composites

A novel damage evolution model for unidirectional (UD) composites is established in this paper in the context of continuum damage mechanics (CDM). It addresses matrix cracking and it is to be applied along with the damage representation established previously. The concept of damage driving force is employed based on the Helmholtz free energy. It is shown that the damage driving force can be partitioned into three parts, resembling closely three conventional modes of fracture, respectively. A damage evolution law is derived accordingly based on the newly obtained expressions of the damage driving force. The fully rationalised Tsai-Wu criterion is employed in the model for predicting the initiation of matrix cracking damage and fibre failure, assisted with the rationalised maximum stress criterion for identifying the damage modes. A mechanism is introduced to describe the unloading behaviour as a part of the proposed model. The predictions were validated against experimental results, showing good agreement with the experiments and demonstrating the capability and effectiveness of the proposed model.

Predicting crack nucleation in commercially pure titanium using orientation imaging microscopy and machine learning

Due to the prohibitively long experimental and simulation times, dwell fatigue (DF) failure prediction in titanium and its alloys is a challenging task. Since most of these failures have a microstructural level origin, this work focusses on utilizing minimal experiments and machine learning for predicting failure initiation points in a given microstructure. Failure initiation points in commercially pure titanium were identified using interrupted tensile and DF tests. Orientation imaging data was used to train a Random Forest model to calculate the relative importance of various grain orientation-based features to crack nucleation. Subsequently a predictive model for identifying locations that are likely to form a DF crack in a microstructure is developed.

Joint formation mechanism and mechanical properties of laser brazed Zn coated steel under different defocusing conditions

Laser brazing, producing a class-A joint surface in automotive, relies on the defocus control to manage laser heating mode and braze performance. This work demonstrates that the laser interaction mechanism transitioned from keyhole welding to conduction brazing as defocus distances increased from −20 to ≥18 mm while keeping other parameters consistent. Uniform brazed joints were achieved at defocuses of +22, +25 and + 30 mm. Increased defocus distance resulted in a wider bead, with a larger laser irradiation area and expanded heat affected zone (HAZ), leading to increased steel melting and more Fe-rich precipitates within the Cu braze. The interfacial reaction layers remained Fe(Si) with increasing thickness as defocus changed from +22 to +30 mm, and two distinct Fe(Si) phases were initially identified. The steel Zn coating evaporated upon direct laser irradiation at upper two regions while participated in interfacial reactions at the weld root. At the weld root, a dramatic phase transition from Zn–Cu to Cu was observed, with liquid Zn(Cu) phases particularly forming in joints with a +30 mm defocus, led to solidification cracks that acted as failure initiation sites during tensile testing. Cracks propagated along the interfacial reaction layer/bead interface, or along large Fe-rich precipitates within the bead. A +30 mm defocus produced a lower hardness HAZ than with a +22 mm defocus, due to the higher content of bainite and tempered martensite resulting from a slower cooling rate. This work provides insights into optimizing laser brazing parameters for Zn-coated steel.

Failure Prediction of an Airfoil-Type Crack in Thermoelectric Coupling Materials

Airfoil-type cracks with curved surfaces and sharp tips are frequently encountered in modern engineering applications and the aerospace industry. However, such cracks significantly threaten structures due to stress concentration and further cause damage. This study investigates the theoretical analysis and failure prediction of airfoil-type cracks within thermoelectric coupling materials under the interaction of remote mechanical loads, heat flux and electric current density. By employing complex variable theory, conformal mapping methods, and the analytic continuation theorem, the full-field stress and stress intensity factors of an airfoil-type crack were determined under three different loading conditions. The results indicate that when the airfoil-shaped crack tip is subjected to horizontal compression, vertical tensile mechanical load, and both heat flux and current density parallel to the crack, the crack tip would reach a dangerous state. Additionally, the full-field stress distribution reveals stress concentration around the crack tip, which explains variations in SIFs under different external forces and shape factors. Four critical situations suppressing crack propagation under mixed loading conditions are proposed. Furthermore, using an acrylic plate and bismuth telluride alloy as examples, the critical values of external loading for the mixed-mode fracture are determined based on the strain energy density criterion. These critical values can be used to predict failure initiation, thus reducing the risk of structural failure due to airfoil cracks within thermoelectric coupling materials.

6411 Ozempic - Oh no! Acute Renal Failure Associated with Initiation of Semaglutide

Abstract Disclosure: K. Barney: None. D. Tahir: None. A. Pannu: None. R. Saeed: None. Background: Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist which has been proven to reduce weight in those with obesity and improve glycemic control in patients with type II diabetes mellitus. The effect of semaglutide on kidney function has not been well established. The phase 3b SUSTAIN trials revealed that when compared with other GLP-1 agonists, semaglutide exhibited more frequent acute kidney injuries [1-3]. The SUSTAIN 6 trial reported two instances of acute renal failure (ARF) in patients with chronic kidney disease, and one case of ARF in a patient with normal kidney function who was treated with semaglutide [3]. Despite these reports, the SUSTAIN 1-9 trials report no significant decline in kidney function associated with semaglutide [3-6]. Case: We present the case of a 58-year-old male with a past medical history of human immunodeficiency virus (HIV), type II diabetes mellitus, and hypertension who presented to the hospital with ARF after initiation of Ozempic (semaglutide) two months prior to presentation. On admission, vitals were stable and physical examination was benign. His pertinent labs were blood urea nitrogen (BUN) 55 mg/dL, creatinine 5.94 mg/dL (baseline 1.2 mg/dL), and urinalysis with 2+ protein. To determine the cause of his renal failure, urine sodium and creatinine were obtained to calculate his fractional excretion of sodium, which was found to be consistent with intrinsic renal disease. Further workup, including renal ultrasound, urine protein, urine eosinophils, complement and free light chain levels, and creatinine kinase, were unrevealing for cause of intrinsic renal injury. He was managed with intravenous fluids and his creatinine improved to 2.03 mg/dL. Given the acute onset of the patient’s renal failure and recent initiation of Ozempic, it was determined that this medication was the cause of his renal failure, and it was discontinued on discharge. He has since followed up with nephrology and endocrinology. He remains off Ozempic and is doing well. Conclusions: Our case highlights a rare but significant adverse effect of semaglutide on renal function. As the use of semaglutide has increased due to its rising popularity for weight loss and glycemic control in type II diabetes mellitus, the potential for renal injury should be considered and discussed with patients. Furthermore, it is imperative that semaglutide associated renal injury be considered as a cause for ARF in patients taking this medication. This case demonstrates that instances of ARF associated with semaglutide treatment are a cause for concern and further exploration. Presentation: 6/1/2024

Prevalence of Axial Spondyloarthritis in Young People With Chronic Low Back Pain at a Hospital-Based Health Management Organization: A 10-Year Database Study.

There is scarce information on the prevalence of axial spondylarthritis (axSpA) using the Assessment of SpondyloArthritis International Society (ASAS) criteria and even less in Latin America. This study aimed to estimate the prevalence of axSpA by applying the ASAS 2009 criteria to a medical records review study of young people with chronic low back pain (LBP) at a university hospital-based health management organization. Electronic medical records from the Hospital Italiano de Buenos Aires health management organization were reviewed to estimate the prevalence of axSpA (radiographic axSpA [r-axSpA] and nonradiographic axSpA [nr-axSpA]) using the ASAS 2009 axSpA criteria in all patients with chronic LBP (≥3 months) aged <45 years at the first LBP appointment, observed between 2009 and 2019. Among 795 young people with CLBP, the estimated prevalence of axSpA was 5.78% (r-axSpA, 2.76%; nr-axSpA, 3.02%). Ten of 46 patients (21.74%) with axSpA (all nr-axSpA) were undiagnosed, with an undiagnosed axSpA prevalence of 1.26%. The median interval between the first LBP appointment and diagnosis was 34.6 months for axSpA (58.7 vs. 23.1 months for r-axSpA vs. nr-axSpA). Previously diagnosed r-axSpA and nr-axSpA patients had comparable use of biological disease-modifying antirheumatic drugs (bDMARDs) (45% vs. 36%) and delays between nonsteroidal anti-inflammatory drug failure and bDMARD initiation (median, 2.76 vs. 2.66 months). In our cohort of young persons with chronic LBP, the prevalence of axSpA was approximately 6%, with a high prevalence of undiagnosed axSpA, which could explain the low prevalence of axSpA reported in previous studies in Latin America.

Solute-induced transition in Poisson's ratio and strength: A phenomenon in additively manufactured Al-Si-Mg alloys

In this study, cubic coupons of AlSi10Mg alloy were printed using the laser powder bed fusion (LPBF) technique. The effect of heating/reheating cycles on solute trapping and partitioning of alloying elements was investigated using atom probe tomography and transmission electron microscopy. Nano-hardness analysis and uniaxial tensile tests equipped with digital image correlation were employed to investigate the mechanical properties and Poisson's ratio. X-ray micro-computed tomography was utilized to detect strain localization sites along the building direction. Also, the uniaxial tensile test was simulated using finite element analysis to verify the experimental data and predict stress triaxiality. The results showed that the solute trapping and partitioning during the LPBF process results in remarkable changes in phases, their size and morphology, Poisson's ratio, strengthening factor, and consequently mechanical properties. While the tensile sample from top part of the LPBF coupon mostly shows porosity due to floating and entrapment of gases during layer-by-layer fusion/solidification, the sample from bottom part is exposed to sub-surface microcracking induced by residual stresses. The hardness, elastic, and shear moduli, Peierls stress, and cumulative strain energy of the top-part sample are higher than those of the bottom-part sample even though electron backscatter diffraction analyses report similar grain size and texture. Besides, by distancing from the build plate, the Poisson's ratio decreases. Simulation results of both samples indicate that the middle of the gauge is a high-potential area of failure initiation, where the bottom-part sample shows higher stress localization.

First Failure Load of Rectangular Laminated and Sandwich Plates Using Isogeometric Analysis

This paper investigates the first failure load of simply supported and clamped laminate and sandwich plates loaded by a distributed normal traction on the top surface. A third-order shear and normal deformable plate theory, the isogeometric basis functions, and five failure criteria, namely, the maximum stress, the Tsai–Wu, the Tsai–Hill, the Hoffman, and the Hashin for laminated plates, and only the Tsai–Hill criterion for sandwich plates are used in this study. Of these, Hashin’s criteria distinguish between the fiber and the matrix failure. The in-plane stresses are found from the plate displacements and Hooke’s law, and the transverse stresses are recovered by integrating the equilibrium equations through the thickness. Effects of the plate aspect ratio, the fiber angle, the face sheet materials, and the core materials on the first failure load are identified. The computed results are found to agree well with those reported in the literature. Whereas the five failure criteria for laminated plates predict nearly the same value of the first failure load, they do not provide the same location of the failure initiation.

An Insight into the Mechanical Properties of Unidirectional C/C Composites Considering the Effect of Pore Microstructures via Numerical Calculation.

Pores are common defects generated during fabrication, which restrict the application of carbon/carbon (C/C) composites. To quantitatively understand the effects of pores on mechanical strength, this paper proposes a representative volume element model of unidirectional (UD) C/C composites based on the finite element method. The Hashin criterion and exponential degraded rule are used as the failure initiation and evolution of pyrolytic carbon matrices, respectively. Interfacial zones are characterized using the cohesive constitutive. At the same time, periodic boundary conditions are employed to study transverse tensile, compressive, and shear deformations of UD C/C composites. Predicted results are compared with the experimental results, which shows that the proposed model can effectively simulate the transverse mechanical behaviors of UD C/C composites. Based on this model, the effects of microstructural parameters including porosity, pore locations, the distance between two pores, pore clustering, and pore shapes on the mechanical strength are investigated. The results show that porosity markedly reduces the strength as porosity increases. When the porosity increases from 4.59% to 12.5%, the transverse tensile, compressive, and shear strengths decrease by 35.91%, 37.52%, and 30.76%, respectively. Pore locations, the distance between two pores, and pore clustering have little effect on the shear strength of UD C/C composites. For pore shapes, irregular pores more easily lead to stress concentration and matrix failure, which greatly depresses the bearing capacity of UD C/C composites.

Effects of interfacial debonding on the stability of finitely strained periodic microstructured elastic composites.

Predicting failure initiation in nonlinear composite materials, often referred to as metamaterials, is a fundamental challenge in nonlinear solid mechanics. Microstructural failure mechanisms encompass fracture, decohesion, cavitation, compression-induced contact and instabilities, affecting their unconventional static and dynamic performances. To fully take advantage of these materials, especially in extreme applications, it is imperative to predict their nonlinear behaviour using reliable, accurate and computationally efficient numerical methodologies. This study presents an innovative nonlinear homogenization-based theoretical framework for characterizing the failure behaviour of periodic reinforced hyperelastic composites induced by reinforcement/matrix decohesion and interaction between contact mechanisms and microscopic instabilities. Debonding and unilateral contact between different phases are incorporated by employing an enhanced cohesive/contact model, which features a special nonlinear interface constitutive law and an accurate contact formulation within the context of finite strain continuum mechanics. The theoretical formulation is demonstrated using periodically layered composites subjected to macroscopic compressive loading conditions along the lamination direction. Numerical results illustrate the ways in which debonding phenomena, in conjunction with fibre microbuckling, may influence the critical loads of the examined composite solid. The sensitivity of the results obtained through the proposed contact-cohesive model at finite strain with respect to its implementation is also explored. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Seismic response and damage evolution process of a bedded slope‒tunnel system via the continuum‒discontinuum element method

To investigate the failure evolution process and failure mechanism of the bedded slope‒tunnel system under earthquakes, this work examines a specific layered slope at a tunnel portal in southeast China and conducts a 2D dynamic analysis with the continuum‒discontinuum element method (CDEM). It investigates the slope's dynamic behavior and potential for instability by evaluating the wave patterns, acceleration, displacement, Hilbert‒Huang transform (HHT) spectral analysis, and equivalent crack ratio. The research results indicate that the analysis of acceleration and displacement over time provides insights into wave propagation within a slope. During minor earthquakes (< 0.3 g), the slope experiences dynamic amplification at the surface and elevation-dependent effects, which are less evident during stronger seismic events. This work also revealed a positive correlation between the tunnel's dynamic amplification and elevation. A method leveraging HHT energy analysis, in conjunction with the slope's equivalent fracture ratio, is introduced to trace the progression of seismic damage across temporal and spatial dimensions. The progression of seismic intensity is characterized by stages of local failure initiation, expansion, and eventual holistic failure. Similarly, the temporal dynamics of instability are categorized into phases of initial instability, acceleration, and eventual sliding. Furthermore, this work explores the impact of tunnels on slope stability by comparing the equivalent fracture ratios and dynamic displacement patterns of slopes both with and without tunnels, revealing the evolution process of seismic damage to slope‒tunnel systems. This work provides a reference for the seismic design of complex slope‒tunnel systems.

The role of the interfaces and cross-links on the mechanical behavior of mineralized collagen fibrils. A numerical approach

Mechanical properties of bone tissue are highly dependent on its hierarchical structure. The presence of microcracks and diffuse damage in lamellar bone is correlated with the failure of the collagen-mineral interface in mineralized collagen fibrils (MCF). The main goal of this work is to evaluate the mechanical behavior of the interfaces and quantify the stiffness loss of the MCF associated with different failure mechanisms, under controlled in-plane displacement. Additionally, we aim to study the role of the cross-links on the fibril mechanical response, beyond the interface failure. Inter- and intra-microfibrilar cross-links are analyzed. In order to address the first issue, a detailed representative volume of the MCF is analyzed by means of the finite element method, under the assumption of plane strain and periodic boundary conditions. In this model the interfaces between constituents are modeled with an exponential cohesive law. Enzymatic cross-links, located at the molecular terminals connecting each 4D (D=67nm) staggered molecules, are represented by non-linear springs. Three in-plane controlled deformations are applied. The results of this work provide the anisotropic stiffness loss of the tissue involved in the different failure mechanisms at the nano-scale length. The initiation of microcracks and the presence of damage zones are compatible with the failure mechanisms observed at interfaces. Interface failure entails a progressive stiffness loss, bringing a non-linear behavior of bone. The strength obtained for the longitudinal maximum deformation is more than 20 times the transverse strength and 3.5 times the shear strength. The quantification of the reduction percentage in the elastic moduli and the shear stiffness when the fibril is damaged, has a potential application in improving failure criteria based on degradation of elastic constants. When longitudinal elongation is applied, the mechanical contribution of the cross-links in delaying the failure initiation of the interface is shown. Likewise, results of this work confirm the scarce influence of the cross-links in the strain range analyzed. Additionally, a three-dimensional numerical model of several microfibrils is defined with the aim of analyzing the mechanical relevance of inter- and intra-microfibrilar cross-links, beyond the interface failure. Results confirm that cross-links transfer the load when strain increases, being highlighted the mechanical competence of the trivalent cross-links.

Elucidating the role of weight loss and glycaemic control in patients with type 2 diabetes.

To investigate the independent contributions of glycated haemoglobin (HbA1c) reduction and weight loss to clinical outcomes in patients with type 2 diabetes (T2D) treated with antidiabetic drugs, including glucagon-like peptide-1 receptor agonists (GLP-1RAs). This observational, retrospective cohort study used deidentified electronic health record-derived data from patients evaluated at the Cleveland Clinic (1 January 2000-31 December 2020). Cohort A included 8876 patients with newly diagnosed T2D treated with any of six antidiabetic drug classes. Cohort B included 4161 patients with T2D initiating GLP-1RA treatment. The effects of body mass index (BMI) and HbA1c reduction, variability, and durability on clinical outcomes were investigated. In Cohort A, each 1% BMI reduction was associated with 3%, 1%, and 4% reduced risk of heart failure (p = 0.017), hypertension (p = 0.006), and insulin initiation (p = 0.001), respectively. Each 1% (~11 mmol/mol) HbA1creduction was associated with 4% and 29% reduced risk of hypertension (p = 0.041) and insulin initiation (p = 0.001), respectively. In Cohort B, each 1% BMI reduction was associated with 4% and 3% reduced risk of cardiovascular disease (p = 0.008) and insulin initiation (p = 0.002), respectively. Each 1% (~11 mmol/mol) HbA1c reduction was associated with 4% and 16% reduced risk of chronic kidney disease (p = 0.014) and insulin initiation (p = 1 × 10-4), respectively. Lower BMI variability and greater BMI durability were associated with decreased risk of clinical outcomes in both cohorts. Antidiabetic medication-associated, and specifically GLP-1RA-associated, weight loss and HbA1c reductions independently reduce real-world clinical outcome risk.