High Strain Levels Research Articles

Enhancing structural health monitoring of fiber-reinforced polymer composites using piezoresistive Ti3C2Tx MXene fibers

The anisotropic behavior of fiber-reinforced polymer composites, coupled with their susceptibility to various failure modes, poses challenges for their structural health monitoring (SHM) during service life. To address this, non-destructive testing techniques have been employed, but they often suffer from drawbacks such as high costs and suboptimal resolutions. Moreover, routine inspections fail to disclose incidents or failures occurring between successive assessments. As a result, there is a growing emphasis on SHM methods that enable continuous monitoring without grounding the aircraft. Our research focuses on advancing aerospace SHM through the utilization of piezoresistive MXene fibers. MXene, characterized by its 2D nanofiber architecture and exceptional properties, offers unique advantages for strain sensing applications. We successfully fabricate piezoresistive MXene fibers using wet spinning and integrate them into carbon fiber-reinforced epoxy laminates for in-situ strain sensing. Unlike previous studies focused on high strain levels, we adjust the strain levels to be comparable to those encountered in practical aerospace applications. Our results demonstrate remarkable sensitivity of MXene fibers within low strain ranges, with a maximum sensitivity of 0.9 at 0.13% strain. Additionally, MXene fibers exhibited high reliability for repetitive tensile deformations and low-velocity impact loading scenarios. This research contributes to the development of self-sensing composites, offering enhanced capabilities for early detection of damage and defects in aerospace structures, thereby improving safety and reducing maintenance expenses.

A comprehensive study on the effect of high-temperature deformation level on microstructure development of austenitic stainless steel

ABSTRACT Austenitic stainless steel has been deformed to different strain levels at high temperatures and electron back-scattered diffraction has been done at the centre of the deformed samples to study the microstructure. A low strain of 0.22 develops deformation substructures and does not contribute much to the change in microstructure. An increase in strain value develops equiaxed grains and at 900 ℃, a necklace-type structure is observed. A decrease in average grain size with increased strain level is observed (except at 1200 ℃). A high fraction of high-angle grain boundaries with a significant fraction of Ʃ3 boundaries is observed at high temperatures and high-strain levels. The texture intensity showed the formation of strong [101] and [001] fibres. However, the intensity distribution between [101] and [001] varies with strain level and deformation temperature. Finally, discussions on the effect of high-temperature deformation on microstructure and texture development have been presented.

The CareVirtue Digital Journal for Family and Friend Caregivers of People Living With Alzheimer Disease and Related Dementias: Exploratory Topic Modeling and User Engagement Study.

As Alzheimer disease (AD) and AD-related dementias (ADRD) progress, individuals increasingly require assistance from unpaid, informal caregivers to support them in activities of daily living. These caregivers may experience high levels of financial, mental, and physical strain associated with providing care. CareVirtue is a web-based tool created to connect and support multiple individuals across a care network to coordinate care activities and share important information, thereby reducing care burden. This study aims to use a computational informatics approach to thematically analyze open text written by AD/ADRD caregivers in the CareVirtue platform. We then explore relationships between identified themes and use patterns. We analyzed journal posts (n=1555 posts; 170,212 words) generated by 51 unique users of the CareVirtue platform. Latent themes were identified using a neural network approach to topic modeling. We calculated a sentiment score for each post using the Valence Aware Dictionary and Sentiment Reasoner. We then examined relationships between identified topics; semantic sentiment; and use-related data, including post word count and self-reported mood. We identified 5 primary topics in users' journal posts, including descriptions of specific events, professional and medical care, routine daily activities, nighttime symptoms, and bathroom/toileting issues. This 5-topic model demonstrated adequate fit to the data, having the highest coherence score (0.41) among those tested. We observed group differences across these topics in both word count and semantic sentiment. Further, posts made in the evening were both longer and more semantically positive than other times of the day. Users of the CareVirtue platform journaled about a variety of different topics, including generalized experiences and specific behavioral symptomology of AD/ADRD, suggesting a desire to record and share broadly across the care network. Posts were the most positive in the early evening when the tool was used habitually, rather than when writing about acute events or symptomology. We discuss the value of embedding informatics-based tools into digital interventions to facilitate real-time content delivery.

Computational Study of the Influence of Crack Orientation in SCM440 Cracked Shaft on Strain Alteration under Transverse Excitation

Previous studies have demonstrated that crack geometry influences strain generation in cracked shafts under excitation loading. The behavior of strain generation varies notably under transverse loading suggesting that the crack orientation could have a significant effect on strain behavior under excitation. This computational study aims to investigate the influence of different crack orientations on strain behavior. The analysis examines the strain at crack tips and the effects of loading on crack alignment under transverse excitation. Crack-controlled parameters, such as shape factor, characteristic length, and orientation parameter, are found to be significant factors governing strain behavior. Specifically, cracks with greater circularity and larger characteristic lengths exhibit higher strain levels under excitation. Crack orientation becomes particularly significant in conveying the strain from the affected area of excitation loading through the crack front, especially in the case of a straight crack, resulting in high strain levels at both tips and distinct strain generation behavior. The findings highlight the significant impact of excitation-affected areas near the excitation location on strain generation over crack geometry. This underscores the potential risk of existing cracks in the shaft and the importance of these factors on strain generation behavior. This study enhances understanding of how crack orientation impacts strain behavior, offering valuable insights for structural integrity assessment and design optimization in engineering applications.

Experimental study of asphalt mixtures with recycled resources: Influence of electric arc furnace slag aggregate roughness and bitumen film thickness on fatigue performance

Electric arc furnace slag (EAFS) is a viable alternative in asphalt mixtures due to its favourable mechanical properties. This study examines the impact of EAFS content and bitumen film thickness (TF) on the fatigue performance of asphalt mixtures. Mixtures with varying levels of EAFS replacement were designed, and their mechanical properties were evaluated through indirect tensile strength and stiffness tests, followed by fatigue tests using the four-point bending method and EBADE (Strain Sweep Test). The results indicated that mixtures with EAFS exhibited increased stiffness, but fatigue performance decreased at high strain levels. At low strain levels, EAFS mixtures performed similarly or better than the control. HMA_GL had the highest TF (13.97 μm), followed by HMA_GS (13.60 μm), HMA_SL (12.66 μm), and HMA_SS (11.77 μm), showing that as the EAFS content increases, the TF decreases. This finding was verified through Digital Image Analysis. This decrease in TF is due to the high porosity and roughness of the EAFS, which in turn reduces the effective bitumen (Pbe) in the mixture. HMA_SL*, with a TF equal to the control, demonstrated a 22 % improvement in fatigue performance compared to HMA_SL. In the EBADE tests, HMA_GL achieved 44.69 MJ/m3 of dissipated energy, HMA_GS 31.55 MJ/m3, HMA_SL 34.45 MJ/m3, and HMA_SS 35.54 MJ/m3. The improved HMA_SL* recorded 42.15 MJ/m3, nearly matching the control. EBADE results confirmed that higher EAFS content increased initial stiffness, but the complex modulus (|E*|) decreased more rapidly as deformation increased. These results are consistent with the stiffness tests. These findings suggest that EAFS can successfully replace natural aggregates in asphalt mixtures, with a moderate increase in bitumen content recommended to improve fatigue performance.

Corrosion Resistance of Zinc Alloy Coatings Containing 1-3wt% Mg and Al at Small Radius Bends

Environmental targets to increase the whole-life efficiency of many products have led to an increased focus on improvements in metallic coating performance, with view to increase durability and minimise consumption of raw materials. Zinc Magnesium Aluminium (ZMA) alloy galvanised coatings have been the focus of numerous research studies over the past two decades. Research has predominantly been based around the improved corrosion resistance of these coatings for automotive and construction products exposed to external environments. A variety of compositions exist, each forming complex microstructures containing primary zinc within eutectics rich in magnesium and aluminium. These compositions generally include, but are not limited to, alloy additions that range between 1 and 2 wt% to zinc. The alloying additions enhance the corrosion resistance and pressing performance. It has been previously identified that limited systematic research has been undertaken to date to understand what influences adverse mechanical behaviours of these microstructures. Studies have shown that eutectic phases are susceptible to cracking on forming. More recent research has attributed the genesis of the cracks, specifically to the twinning locations within the eutectic phase, MgZn2.This study investigates four Zinc Alloy coatings containing: 1Mg1Al; 3Mg3Al; 1Mg3Al and 3Mg1Al wt% additions. These compositions formed different morphologies, with varying volumes of primary and eutectic phases. All four specimen coatings are approximately 30 microns thick and have been created using identical heat treatment processing parameters and cycle. The galvanic alloy coatings have been mounted upon 0.7mm gauge Interstitial Free (IF) steel substrate. This substrate has been selected as typically used for car body panels in the automotive industry, and cold formed light gauge structural sections in the construction industry. IF steels offer good tensile strength, as well as good formability capability. A Hot Dip Processing Simulator was used to apply the IF steels with the four separate specimen coatings, to isolate variables, such as: substrate grade, substrate thickness, coating thickness, heat treatment cycles and post coating cooling.Uniaxial tensile tests are governed by the structural substrate mechanical properties. Typically, with elongation limits of approximately 20%. Traditional soft-tempered galvanic coatings can achieve as much as 65% elongation, which is desirable when forming pre-galvanised sheet material. However, bending material presents a stress distribution of both tension and compression. Elongations as much as 100% (theoretical 0T bend) can be induced on the coated material surface, without total structural failure of its substrate. BS EN 13523-7 provides a Standard for testing and specifying a minimum bend radius for coated sheet material. As bend radius and material thickness govern bending tensile strain, bends are categorised relative to material thickness.A systematic study was undertaken that incrementally induced relatively high levels of strain to the material surface, by bending the pre-coated steel sheet material. The cracked microstructures of the four zinc alloy coating specimens were quantified before accelerated corrosion tests were undertaken. All specimen samples were immersed in 1wt% NaCl electrolyte solution and test data recorded over a 24-hour period, at room temperature. A GAMRY Potentiostat recorded Open Circuit (OCP) and Linear Polarisation Resistance (LPR) data of both strained and unstrained samples and results were compared.The results showed that for a comparable strain, each of the cracked coating specimens were cathodically polarised. The depths of coating cracks were observed using a scanning electron microscope, during a fracture analysis exercise of cross-sectional images. The cracks were observed to be the full depth of the coating full thickness, exposing the surface of the steel substrate. The characteristics of the coating fractures correspond with the electrochemical test results. The corrosion resistance of these zinc alloy coating specimens was compromised when the coatings cracked on the tension surface at small radius bends, when compared to flat unstrained samples.

Torsional behavior of Ni-rich NiTi alloys obtained by powder metallurgy and hot deformation

The effects of severe plastic deformation on NiTi alloys’ structure and properties have been extensively studied over the past decades. However, there is a notable lack of systematic data regarding the impact of industrial hot deformation techniques on these alloys. This gap arises from challenges in manufacturing processes related to the unevenness of ingots produced by casting technologies. This study investigates the effects of hot rotary swaging, extrusion, and radial shear rolling on the martensitic transformation, shape memory effect, superelasticity, and damping capacity of NiTi Ni-rich alloys fabricated through powder metallurgy. The properties were investigated under torsional load on wires prepared by spark eroding from deformed rods. Our findings indicate that samples after rolling and extrusion exhibit a superelastic strain of 14 ± 0.5% attributed to a high yield stress of approximately 600–800 MPa and torsional testing providing the material to be fully involved in recovery process. Samples after rolling and swaging demonstrate a high level of reversible strain with a one-way shape memory effect ranging from 5 to 7%. Conversely, extrusion, due to the inhomogeneity of resulting workpieces, induces a complex, multi-stage martensitic transformation that undermines the shape memory effect. Furthermore, all deformation methods except extrusion contribute to increased alloy homogeneity, resulting in a narrower temperature range for martensitic transformations. Rotary swaging notably increases the height of an internal friction peak from 0.015 to 0.045 compared to the undeformed material, whereas rolling gives the lowest value of 0.012 among others. This study provides valuable insights into how hot thermomechanical processing influences the properties of NiTi alloys and shows that powder metallurgy combined with hot deformation can be considered an alternative approach for achieving high functional properties of these alloys.

CarersCanADAPT: Study protocol of a stepped care pathway and hybrid type 1 effectiveness-implementation trial of an online cognitive behavioural therapy (iCBT) program for cancer carers with anxiety and depression

BackgroundFamily or friend carers of people with cancer report high levels of depression, anxiety, caregiving strain, and unmet needs. Limited strategies for identification and management of distress have been established among cancer carers. This paper describes the protocol of two linked studies: Study 1a, a distress screening and stepped care pathway feasibility study and Study 1b, a hybrid implementation-effectiveness Randomised Controlled Trial (RCT) to assess the benefit of a comprehensive, carer-centred online Cognitive Behavioural Therapy (iCBT) program for carers with anxiety and depression. MethodsFor Study 1a, 300 cancer carers will be screened for distress. Carers with low distress will be referred to publicly available carer resources. Carers scoring 4 and higher on the distress thermometer will complete depression and anxiety measures. Carers with high anxiety/depression will be recommended psychological therapy. Carers with mild/moderate anxiety and/or depression will be allocated to the Carers iCBT Program, evaluated via a RCT with waitlist control group (Study 1b). For Study 1b, intervention group carers will receive access to a 6-lesson self-directed online iCBT program. Waitlist-controls will access the intervention at 14 weeks. Intervention and control groups will complete baseline, 6 week, and 14 week self-report measures; controls will complete additional measures at 20 and 28 weeks. A sample size of n = 166 carers in the iCBT RCT is needed. ConclusionsIf acceptable, feasible and effective, this pathway and iCBT intervention could offer a sustainable, scalable and low-cost approach to identifying and managing distress in carers, and potentially improving patient and carer outcomes.Trial Registration: Australian and New Zealand Clinical Trial Registry number: ACTRN12623001341617p.

The role of coherent nano precipitates on stacking fault and deformation twin formation during tensile deformation of wire arc additive manufactured nickel-aluminum-bronze

The strain hardening mechanisms and dislocation interactions of a wire arc additively manufactured (WAAM) nickel-aluminum-bronze (NAB) alloy was investigated using multi-scale characterization approach cross-correlating scanning electron microscopy (SEM), SEM-based electron back-scatter diffraction (EBSD), site- and crystallographic orientation-specific focused ion beam (FIB) nanofabrication, scanning transmission electron microscopy (STEM) and STEM-based energy dispersive X-ray spectroscopy (EDS). Flat, rectangular dog bone specimens were strained under uniaxial tension conditions. To understand the micro- and nanometer scale deformation mechanisms throughout the microstructure, tensile test specimens were interrupted near the yield strength and ultimate tensile strength. STEM microstructural characterization revealed that tensile deformation occurs by planar slip and multiple slip bands interacting on different {111} planes as well as the nucleation of dislocations from the interfaces associated with grains and secondary phase particles. To the authors knowledge for the first time the Center of symmetry (COS) analysis revealed that in both samples the shearing of nanoscale precipitates led to the formation of extended stacking faults including a combination of intrinsic stacking faults and 2-layer extrinsic stacking faults. At high strain levels more dislocations and stacking faults were nucleated, as well as intersecting slip bands further facilitating the activation of the stair-rod cross-slip mechanism and thickening of an ESF to create a 3-layer nano-twin. Activated mechanisms of plastic deformation and associated role of the precipitates are discussed with respect to the microscopic strength-plasticity characteristics as well as macroscopic mechanical properties of WAAM NAB alloy.

Characterization of woven composite material under multiaxial loading regimes using FE-based stereocorrelation

In this paper, woven glass fiber composite samples were subjected to three different cyclic loading histories (i.e., tensile, shear and combined loading at 45° via the Modified Arcan Fixture. During the experiments, the samples were monitored by a stereovision system. Finite Element based stereocorrelation was used to measure the displacement and strain fields. The analysis of the experiments revealed different damage mechanisms. Furthermore, for the 45° experiment, the highest strain levels were reached, whereas for the tensile test, the highest stress levels were achieved.

Are Ratings of Perceived Exertion during Endurance Tasks of Predictive Value? Findings in Trunk Muscles Require Special Attention.

Background: Subjective rating scales of perceived exertion are often used to quantify effort levels during various endurance exercises, particularly submaximal tasks. The aim of the current study was to determine whether predictive conclusions can be drawn from perceived exertion levels surveyed at the start of defined submaximal endurance tasks. Methods: In this study, healthy participants performed a 10-min endurance task at 50% of their upper body weight, targeting either the back muscles (n = 47, 24 women) or abdominal muscles (n = 32, 17 women). At the end of each minute, participants were asked to rate their perceived exertion (RPE) using the 14-points Borg Scale. Based on their initial and final RPE levels, and for each muscle group separately, participants were divided into subgroups reflecting low (good start/good end) and high (bad start/bad end) strain levels. These values were then compared over the duration of the exercise. Comparisons of RPE levels between subgroups were made using the Mann-Whitney U-test for independent samples, with Bonferroni-Holm correction to account for multiple comparisons. Results: Overall, strain levels increased throughout the duration of the exercise. For the abdominal muscles, the difference between the two RPE groups remained constant over time: participants with good start/end ratings consistently showed different strain levels from those with bad start/end ratings, regardless of whether the grouping was based on initial or final exertion levels. In contrast, for the back muscles, the initial grouping showed a crossover in strain values: by the end of the task, participants in the good start group tended to report higher strain than those in the bad start group. No differences were found in initial RPE values when the grouping was based on final exertion levels. Conclusions: For endurance tasks involving the abdominal muscles, initial strain levels have strong predictive value, whereas this is not the case for the back muscles. Because back muscles are frequently loaded, continuous monitoring of RPE levels is necessary to prevent unexpected task failure, as initial RPE values are not predictive. In contrast, RPE values of 11 or higher on the 14-points Borg scale predict complete exhaustion or even premature task failure with high certainty for abdominal muscle exercises, while lower RPE levels indicate that exercise intensity can be increased.

The impact of mechanical strain on magnetic and structural properties of 2D materials: A Monte Carlo study.

The inherent flexibility of two-dimensional (2D) materials allows for efficient manipulation of their physical properties through strain application, which is essential for the development of advanced nanoscale devices. This study aimed to understand the impact of mechanical strain on the magnetic properties of two-dimensional (2D) materials using Monte Carlo simulations. The effects of several strain states on the magnetic properties were investigated using the Lennard-Jones potential and bond length-dependent exchange interactions. The key parameters analyzed include the Lindemann coefficient, radial distribution function, and magnetization in relation to temperature and magnetic field. The results indicate that applying biaxial tensile strain generally reduces the critical temperature (Tc). In contrast, the biaxial compressive strain increased Tc within the elastic range, but decreased at higher strain levels. Both compressive and tensile strains significantly influence the ferromagnetic properties and structural ordering, as evidenced by magnetization hysteresis. Notably, pure shear strain did not induce disorder, leaving the magnetization unaffected. In addition, our findings suggest the potential of domain-formation mechanisms. This study provides comprehensive insights into the influence of mechanical strain on the magnetic behavior and structural integrity of 2D materials, offering valuable guidance for future research and advanced material design applications.

Nonlinear viscoelastic effect on the fatigue performance of wood tar-based rejuvenated asphalt

The nonlinear viscoelasticity (NLVE) effects of rejuvenated asphalt are often neglected during fatigue degradation, potentially leading to misjudgment of its true fatigue performance. To more accurately quantify the fatigue life of rejuvenated asphalt under NLVE effects, frequency sweep (FS), incremental stress sweep (ISS), and linear amplitude sweep (LAS) tests were used to study two types of rejuvenated asphalt. FS and ISS tests respectively obtained the dynamic modulus |G*|LVE and |G*|NLVE representing the linear viscoelasticity (LVE) and NLVE of rejuvenated asphalt, and incorporated them into the simplified viscoelastic continuum damage (S-VECD) model to establish the fatigue failure criterion and predict the fatigue life of rejuvenated asphalt under high strain levels in LAS tests. The findings indicate that the NLVE-based-S-VECD model quantifies fatigue damage in rejuvenated asphalt lower than the LVE model, and the fatigue life of rejuvenated asphalt increases significantly after considering the NLVE effect. Besides, the failure difference (∆GR) and failure area difference (∆A) defined during the modeling process explain the impact of NLVE on the fatigue failure criterion average pseudo strain energy release rate (GR) of rejuvenated asphalt, validating the necessity of incorporating NLVE into the fatigue performance analysis of rejuvenated asphalt. Therefore, it's necessary to account for the impact of NLVE effect on the fatigue performance of rejuvenated asphalt in engineering practice, which will contribute to the development and application of rejuvenator.

Biomechanical changes of tree shrew posterior sclera during experimental myopia, after retrobulbar vehicle injections, and crosslinking using genipin

Myopia is a common ocular condition characterized by biomechanical weakening revealed by increasing creep rate, cyclic softening scleral thinning, change of collagen fibril crimping, and excessive elongation of the posterior sclera resulting in blurred vision. Animal studies support scleral crosslinking as a potential treatment for myopia control by strengthening the weakened sclera and slowing scleral expansion. While multiple studies investigated aspects of the biomechanical weakening and strengthening effects in myopia and after scleral crosslinking, a comprehensive analysis of the underlying mechanical changes including the effect of vehicle injections is still missing. The purpose of this study was to provide a comprehensive analysis of biomechanical changes by scleral inflation testing in experimental myopia, after retrobulbar vehicle injections and scleral crosslinking using genipin in tree shrews. Our results suggest that biomechanical weakening in myopia involves an increased creep rate and higher strain levels at which collagen fibers uncrimp. Both weakening effects were reduced after scleral crosslinking using genipin at doses that were effective in slowing myopia progression. Vehicle injections increased mechanical hysteresis and had a small but significant effect on slowing myopia progression. Also, our results support scleral crosslinking as a potential treatment modality that can prevent or counteract scleral weakening effects in myopia. Furthermore, vehicle solutions may cause independent biomechanical effects, which should be considered when developing and evaluating scleral crosslinking procedures.

Mineral and cross-linking in collagen fibrils: The mechanical behavior of bone tissue at the nano-scale

The mineralized collagen fibril is the main building block of hard tissues and it directly affects the macroscopic mechanics of biological tissues such as bone. The mechanical behavior of the fibril itself is determined by its structure: the content of collagen molecules, minerals, and cross-links, and the mechanical interactions and properties of these components. Advanced glycation end products (AGEs) form cross-links between tropocollagen molecules within the collagen fibril and are one important factor that is believed to have a major influence on the tissue. For instance, it has been shown that brittleness in bone correlates with increased AGEs densities. However, the underlying nano-scale mechanisms within the mineralized collagen fibril remain unknown. Here, we study the effect of mineral and AGEs cross-linking on fibril deformation and fracture behavior by performing destructive tensile tests using coarse-grained molecular dynamics simulations. Our results demonstrate that after exceeding a critical content of mineral, it induces stiffening of the collagen fibril at high strain levels. We show that mineral morphology and location affect collagen fibril mechanics: The mineral content at which this stiffening occurs depends on the mineral’s location and morphology. Further, both, increasing AGEs density and mineral content lead to stiffening and increased peak stresses. At low mineral contents, the mechanical response of the fibril is dominated by the AGEs, while at high mineral contents, the mineral itself determines fibril mechanics.

How Does Successful Aging Apply to Black Women? A Latent Class Analysis.

Although prior research has identified racial/ethnic and gender differences in successful aging (SA), heterogeneity within groups has been little examined. We consequently explore the variety of aging experiences among older Black women. We used the 2010/2012 U.S. Health and Retirement Study, limiting analyses to Black women who completed the Psychosocial Leave-Behind Questionnaire (N = 1,186). We conducted latent class analysis using indicators of physical health, psychological well-being, social support/strain, and social engagement. Six SA latent classes were identified and labeled according to their distinctive characteristics: infirm, isolated, taxed, independent, vivacious, and robust. The infirm class had uniformly poor health, whereas the isolated class was in poor physical health but also lacked social relations. Although both had average physical health and psychological well-being, the taxed class experienced high levels of social support and social strain compared to the high support (and unpartnered) independent class. The vivacious and robust classes exhibited high physical health and psychological well-being, high social support/low social strain, and high social engagement, but vivacious women (23% of respondents) were unpartnered and robust women (16% of respondents) were partnered. The robust class had the highest physical and psychological well-being, and best social relations across all classes. Using nationally representative data, we reveal significant heterogeneity in Black women's aging experiences. Although many face difficult aging experiences, 39% of older Black women fit the SA framework well. Future work should recognize that Black women's aging experiences are not homogenous.

Investigating dilation response in PET FRP-confined reinforced concrete: Experimental study

In compression, concrete undergoes dilation due to the Poisson’s effect. Beyond the elastic limit, rapid crack propagation causes unstable expansion, leading to stiffness degradation, reduced strength, and ductility. External confinement with fiber-reinforced polymer (FRP) composites effectively manages this dilation, maintaining core integrity at high strength and deformation levels. However, internal steel reinforcement, especially when poorly detailed, can hinder FRP's efficacy by inducing stress concentrations from longitudinal bar buckling, resulting in premature FRP failure. This study addresses this challenge by utilizing polyethylene terephthalate (PET) FRP with a large rupture strain (LRS) capacity to delay premature rupture to high strain levels. Experimental results on poorly detailed reinforced concrete (RC) externally confined with PET FRP are presented, with variables including PET FRP layers, longitudinal bar buckling length, and cross-sectional aspect ratio. Detailed discussions on the effects of these variables on lateral to axial strain ratio, dilation rate, and volumetric response of confined concrete are provided. Test results have shown that PET FRP effectively managed the unstable dilation of confined concrete, even with internal steel reinforcement. Following the yielding of lateral ties and the buckling of longitudinal bars, PET FRP efficiently handled local stress concentrations and redistributed internal concrete damage. Despite PET FRP's low elastic modulus causing significant lateral expansion, its LRS capacity maintained the integrity of the entire column under high deformation.

Effects of cutting temperature on the genes and fatigue properties of asphalt during its refining process

Asphalt binders performance is affected by refining process and crude oil. In this work, we investigated the effect of cutting temperature on the genes and fatigue properties of asphalt during asphalt refining. Five cutting temperatures (420 °C to 440 °C, interval of 5 °C) were set during the asphalt preparation, expanded the asphalt samples through ageing method. Fourier Transform Infrared (FTIR), Gel Permeation Chromatography (GPC), Nuclear Magnetic resonance Spectrum (1HNMR), Elemental analyzer, and improved Brown-Ladner method were used to characterize the asphalt genes. The fatigue performance of asphalt through Linear Amplitude Sweep (LAS) combined with the Simplified Viscoelastic Continuum Damage (S-VECD). Finally, the Pearson correlation method was used to analyze the correlation between genes and fatigue parameters of binders. The results showed that the cutting temperature and aging process changed the genes distribution of binders and these influence the fatigue properties of binders. In addition, the fatigue life of asphalt decreased at high strain levels and increased at low strain levels as the cutting temperature and the degree of ageing increased. The Pearson correlation results indicated a significant correlation between the genes and fatigue parameters of asphalt, however, the key genes affecting low-strain (2.5% and 5 %) and high-strain (10% and 20%) level fatigue in asphalt are significantly different. The outcomes of the paper provide insights about the influence of cutting temperature on the variation of asphalt genes and fatigue parameters, to allow more informed to promote of asphalt preparation.

Damage evolution and ductile fracture of commercially-pure titanium sheets subjected to simple tension and cyclic bending under tension

This paper describes a study into the evolution of damage in commercial-purity titanium (CP–Ti) sheets subjected to cyclic bending under tension (CBT) and uniaxial tension (simple tension, ST). Sections were taken from sheets that were strained to various levels under both methods and were imaged using X-ray computed tomography (XCT) to reveal insights into the size, density, and distribution of microvoids in the sheets. Digital image correlation (DIC) was also used to observe the surface strain of CBT and ST sheets during testing. These results showed that elongation to failure (ETF) for CBT deformation is about 2.5× higher than for ST, local longitudinal strains in the bulk of the CBT sample are around 1.3× higher than the peak strain in the ST necked region, and 1.7× higher in the localized region of CBT failure. It was found that the volume-density of voids in both sheets followed a similar exponential increase with strain, reaching nearly 45× higher in the CBT than the ST sheets before the onset of failure, mainly due to the higher strain levels achieved. A higher volume density of voids developed in the center of sheets at high levels of strain, for both processes, with the density in the sheet center becoming approximately double that found near the edges. Scanning electron microscopy (SEM) was used to examine the fracture surface of CBT and ST sheets after failure. The observations are presented and discussed highlighting the CBT process as effective to delay ductile fracture of the CP-Ti sheets.

Assessing correlations between two linear amplitude sweep (LAS) standards for evaluating the fatigue properties of aged bitumen

ABSTRACT Linear amplitude sweep (LAS) is an accelerated and well-established testing method to evaluate bitumen fatigue. However, there are different versions of LAS procedures employed. Significant differences in loading modes, damage failure criteria and calculations exist between existing standards, leading to the inconsistency in the performance characterisation of bitumen. This study investigated the fatigue performance of six different bitumen at various ageing levels using two versions of the LAS standards (TP101-14 and T391-20). The stress–strain curves, damage characteristic curves, prediction of fatigue life and cracking length were analysed and compared. It was seen that conclusions drawn from the old version of LAS standard (TP101-14) were unclear as no distinct trends related to change in fatigue life could be observed for binders with progressively increased ageing levels, regardless of the strain levels used for analysis. The new version of LAS (T391-20), however, showed acceptable consistency. The trends indicate that at low strain levels, the fatigue life increases with ageing levels, while opposite trend was observed at higher strain levels. Moreover, the cracking length as defined in the T391-20 standard increases with progressively increased ageing. The new version of LAS standard (T391-20) is recommended for characterising the fatigue performance of aged bitumen.