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The network structure within polymers significantly influences their mechanical properties, including their strength, toughness, and fatigue resistance. All-atom molecular dynamics (AAMD) simulations offer a method to investigate the energy dissipation mechanism within polymers during deformation and fracture; Such an approach is, however, computationally inefficient when used to analyze polymers with complex network structures, such as the common chemically double-networked hydrogels. Alternatively, coarse-grained molecular dynamics (CGMD) models, which reduce the computational degrees of freedom by concentrating a set of adjacent atoms into a coarse-grained bead, can be employed. In CGMD simulations, a coarse-grained force field (CGFF) is a critical factor affecting the simulation accuracy. In this paper, we proposed a data-based method for predicting the CGFF parameters to improve the simulation efficiency of complex cross-linked network in polymers. Here, we utilized a typical chemically double-networked hydrogel as an example. An artificial neural network was selected, and it was trained with the tensile stress–strain data from the CGMD simulations using different CGFF parameters. The CGMD simulations using the predicted CGFF parameters show good agreement with the AAMD simulations and are almost fifty times faster. The data-inspired CGMD model presented here broadens the applicability of molecular dynamics simulations to cross-linked polymers and has the potential to provide insights that will aid the design of polymers with desirable mechanical properties. [ABSTRACT FROM AUTHOR]

Compression-compression fatigue behavior of hybrid unidirectional/woven carbon-fiber reinforced composite laminates after low-velocity impact (LVI) was studied in this paper. The paper contains two parts. Firstly, different levels of impact energy were introduced on the specimens. Impact damage modes were obtained and characterized as fiber breakages, matrix cracks, indentation and delamination. The relationships between indentation depth/damage area and impact energy were established. Secondly, compression-compression fatigue tests were conducted on the impact damaged specimens. Fatigue life degradation trends were analyzed and fatigue limit for different types of specimens was determined. Delamination areas by depth mode and amplitude mode of C-scan showed an increasing trend with the fatigue life increasing. Stiffness decreased sharply in the early and ending stages of fatigue life. However, stiffness exhibited stable or slightly decreasing rates in the mid-stage of fatigue life. A line-shaped failure cracks going through the impact point were observed in the fatigue failure specimens. [ABSTRACT FROM AUTHOR]

For Ti alloys used in oil drilling pipe, the fatigue crack propagation (FCP) resistance is one of the key properties for petroleum industrial applications. In this work, the fatigue crack propagation behaviors of bimodal, equiaxed, lamellar, and Widmanstatten microstructures have been systematically investigated and characterized by SEM and EBSD. The results show that the Widmanstatten microstructure containing α colonies has higher yield strength (877 MPa), moderate elongation (9.3%), and better FCP resistance compared to other specimens. During the process of crack propagation, the large α colonies can effectively deflect the cracks and induce secondary cracks, which significantly impedes the main crack propagation. Additionally, 101¯2<101¯1¯> tensile twinning can occasionally occur within the large α colony along the crack, improving the plasticity of the crack tip and resulting in a decrease in fatigue crack propagation rate (FCPR). Highlights: Fatigue crack propagation behaviors of different microstructures were investigated.The Widmanstatten exhibits good tensile properties and crack propagation resistance.The 101¯2<101¯1¯> tensile twinning was found inside the large α colony along crack. [ABSTRACT FROM AUTHOR]

The prediction of fatigue strength for metallic materials in a wide range of stress ratios is a crucial engineering challenge. To pursue a more accurate method, the dependence of fatigue strength on stress ratio for 35CrMo steel and other materials was investigated in detail. It was found that as the stress ratio increases, the damage mechanism changes, and the errors of the conventional models in predicting the fatigue strength increase. The reason is that those models fail to describe the fatigue damage evolution of metallic materials under some special conditions. Based on the variational fatigue damage, a new prediction method was proposed by introducing the damage parameter. Through the validation with fatigue strength covering a variety of metallic materials and loading conditions, the method exhibits higher universality. And then the corresponding parameter of the formula is further analyzed to elucidate the influences of various loading conditions on fatigue damage of materials. Highlights: The new method exhibits good generality and accuracy.The new method greatly improves the prediction efficiency.The optimized method can offer theoretical support to enhance fatigue properties. [ABSTRACT FROM AUTHOR]

The investigation of fatigue behavior typically involves time‐consuming tests, leading some researchers to explore methodologies based on self‐heating tests to reduce the process. For composite materials, the conventional approach involves piecewise linear approximations of the self‐heating curve and the stress transition between the first and second regimes is arbitrarily associated with a fatigue lifetime equal to 106 cycles. This paper proposes a novel methodology to address these simplifications. First, a non‐linear viscoelastic model is used to describe the self‐heating curve. Based on the mechanisms established in the literature, a link is proposed between the dissipation and the fatigue limit. The load leading to a significant contribution of non‐linear mechanisms is associated with an infinite life time. It allows the identification of an S– N curve and prediction of fatigue behavior through a minimal number of tests. The comparison with fatigue results is satisfactory. Highlights: A link is proposed between dissipation and fatigue.Modeling of the dissipation in laminated composites subjected to cyclic loadings.A criterion is proposed to identify the fatigue limit based on the dissipation.A S– N curve is identified and extrapolated up to high cycles fatigue. [ABSTRACT FROM AUTHOR]

Bamboo fiber is a natural fiber that is ecologically beneficial and one of the best materials to replace lignin fiber for roads, which is still difficult to utilize properly in asphalt mixtures owing to its poor adherence, dispersion, and hydrophilicity. Previous research has discovered that alkali treatment, as an effective treatment approach, may effectively lower the hydrophilicity of plant fibers and improve their compatibility with the matrix. As a result, it is vital to investigate the effect of alkali treatment on bamboo fibers used in asphalt mixtures. The composition and microstructure of bamboo fibers treated with alkali were investigated using SEM and FTIR methods, while the adhesion between the bamboo fiber and asphalt before and after alkali treatment was tested using the fiber pull-out test. In addition, the dispersion rate of bamboo fibers in asphalt mixture was determined by developing a connection equation using the Schellenberg binder drainage test. The performance of bamboo fiber asphalt mixtures was then evaluated using rutting tests, beam bending tests, immersion Marshall tests, freeze-thaw splitting tests, and cyclic fatigue testing. The results showed that the alkali treatment successfully eliminated impurities in the outer layer of the bamboo fibers and reduced their hydrophilicity, which enhanced the asphalt-bamboo fiber interactions as well as the asphalt mixture's water damage resistance, specifically manifested as the residual stability of ABM was enhanced by 7.8% and the splitting tensile strength of ABM was raised by 12.2%. Furthermore, the surface polarity of the bamboo fibers was reduced, which weakened the agglomeration phenomenon and increases the dispersion rate of bamboo fibers in the mixture by 9%, efficiently improving the low-temperature cracking resistance and fatigue performance of asphalt mixtures. [ABSTRACT FROM AUTHOR]

This study investigates the profound influence of multi-axial forging (MAF) on the microstructural characteristics, high cycle fatigue properties, and impact toughness behaviour of the bulk ultrafine-grained aluminum-lithium (Al–Li) 8090 alloy. The solution-treated Al–Li 8090 alloy was subjected to MAF at both liquid nitrogen temperature (LNT) and room temperature for 2, 4, and 6 forging cycles, resulting in cumulative true strains of 1.2, 2.4, and 3.6, respectively. The MAFed sample at LNT after 6 cycles displayed a well-defined ultrafine-grained microstructure, exhibiting grain sizes ranging from 100 to 400 nm. Detailed electron backscatter diffraction analysis confirmed significant grain refinement with increasing MAF cycles for various conditions. The high-cycle fatigue strength exhibited a progressive enhancement with the increasing number of cycles and was observed to be maximum for the CF cycle-6 condition (131 MPa), attributing to the effective suppression of dynamic recovery at cryogenic temperatures. [ABSTRACT FROM AUTHOR]

Photochromic luminescent glass-ceramics attract lots of attention as an optical storage medium owing to their large storage capacity, reversible luminescence modulation, simple operation, etc. Herein, a kind of phosphosilicate glass containing AgBr nanoparticles was designed and prepared, which can realize the color reversible transformation between light yellowish-green and brown by alternating 365 nm light illumination and thermal treatment at 300 °C. The mechanism of photochromism and bleaching of the glass is related to the generation and decomposition of Ag0 clusters. Relying on the re-absorption effect, the emission intensity of Eu3+ ions could be reversibly regulated, showing the maximum luminescence contrast of 74 %. A good fatigue resistance and reproducibility of transmittance and luminescence modulation could be observed in cycle measurements, demonstrating its potential in the optical memory field. [ABSTRACT FROM AUTHOR]

The paper focuses on the cutting behavior of Glass Fiber Reinforced Polymer (GFRP) composites and GNP–GFRP composites that contain varying amounts of Graphene Nano Platelets (GNP). GFRP composites are increasingly being used in a variety of industrial applications due to their excellent mechanical properties, such as high strength, stiffness, and low weight. However, their machining and cutting behavior can be challenging due to the presence of the reinforcing fibers. Therefore, the study aims to investigate the machining behavior of GFRP composites and the effect of adding GNP on their cutting behavior. The effect of different parameters such as cutting speed, feed rate and reinforcement rate on cutting forces and delamination factor is investigated. In addition, the tensile strength and fatigue behavior of the composite materials with the best and worst delamination factors were also determined. Addition of up to 0.2 wt.% of GNP to GFRP composites resulted in an increase in cutting forces and delamination factor when drilling GFRP composites. While the cutting force and delamination factor decreased with the increase in cutting speed, the cutting force and delamination factor increased with the increase in the feed rate. Analysis of variance (ANOVA) was performed to determine the effects of drilling parameters and reinforcement ratio on cutting force and delamination factor according to full factorial experimental design. The most efficient factor on the cutting forces is found to be feed rate (84.97%), followed by the reinforced rate (6.48%) and cutting speed (6.13%). The most efficient factor on the delamination factor is determined to be feed rate for (44.49%), followed by the reinforced rate (29.20%) and cutting speed (21.73%). [ABSTRACT FROM AUTHOR]

As promising candidates for widespread application, advanced ceramic fiber mats with robust mechanical properties are urgently needed. However, the brittleness, fatigue failure, and large density of ceramic fiber pose significant obstacles to its practical application. Herein, a novel SiO2 aerogel/ZrO2 composite nanofibrous membrane (SZCNFM) with excellent flexibility was prepared by introducing SiO2 aerogel nanoparticles into ZrO2 nanofiber via simple co‐electrospinning. The developed tetragonal zirconia phase without changing up to 1200°C endows SZCNFM material with excellent thermal stability. Furthermore, the as‐prepared membranes exhibit fatigue resistance ability which can maintain 98% of the original stress after 100 buckling cycle tests. The addition of mesoporous structure aerogel reduces the heat transfer of the nanofibrous membrane, giving its low thermal conductivity (30 mW/m/K) and low‐frequency sound absorption (noise reduction coefficient of 0.52). Combined with the high‐temperature resistance, low thermal conductivity and excellent sound‐absorption ability make it a promising material for heat insulation and acoustic absorption. [ABSTRACT FROM AUTHOR]

Hydrogels, recognized for their flexibility and diverse characteristics, are extensively used in medical fields such as wearable sensors and soft robotics. However, many hydrogel sensors derived from biomaterials lack mechanical strength and fatigue resistance, emphasizing the necessity for enhanced formulations. In this work, we utilized acrylamide and polyacrylamide as the primary polymer network, incorporated chemically modified poly(ethylene glycol) (DF-PEG) as a physical crosslinker, and introduced varying amounts of methacrylated lysine (LysMA) to prepare a series of hydrogels. This formulation was labeled as poly(acrylamide)-DF-PEG-LysMA, abbreviated as pADLx, with x denoting the weight/volume percentage of LysMA. We observed that when the hydrogel contained 2.5% w/v LysMA (pADL2.5), compared to hydrogels without LysMA (pADL0), its stress increased by 642 ± 76%, strain increased by 1790 ± 95%, and toughness increased by 2037 ± 320%. Our speculation regarding the enhanced mechanical performance of the pADL2.5 hydrogel revolves around the synergistic effects arising from the co-polymerization of LysMA with acrylamide and the formation of multiple intermolecular hydrogen bonds within the network structures. Moreover, the acid, amine, and amide groups present in the LysMA molecules have proven to be instrumental contributors to the self-adhesion capability of the hydrogel. The validation of the pADL2.5 hydrogel's exceptional mechanical properties through rigorous tensile tests further underscores its suitability for use in strain sensors. The outstanding stretchability, adhesive strength, and fatigue resistance demonstrated by this hydrogel affirm its potential as a key component in the development of robust and reliable strain sensors that fulfill practical requirements. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive study of the mechanical properties of selective laser sintered polyamide components is presented, for various different process parameters as well as environmental testing conditions. For the optimization of the static and dynamic mechanical load behavior, different process parameters, e.g., laser power, scan speed, and build temperature, were varied, defining an optimal parameter combination. First, the influence of the different process parameters was tested, leading to a constant energy density for different combinations. Due to similarities in mechanical load behavior, the energy density was identified as a decisive factor, mostly independent of the input parameters. Thus, secondly, the energy density was varied by the different parameters, exhibiting large differences for all levels of fatigue behavior. An optimal parameter combination of 18 W for the laser power and a scan speed of 2666 mm/s was determined, as a higher energy density led to the best results in static and dynamic testing. According to this, the variation in build temperature was investigated, leading to improvements in tensile strength and fatigue strength at higher build temperatures. Furthermore, different ambient temperatures during testing were evaluated, as the temperature-dependent behavior of polymers is of high importance for industrial applications. An increased ambient temperature as well as active cooling during testing was examined, having a significant impact on the high cycle fatigue regime and on the endurance limit. [ABSTRACT FROM AUTHOR]

Offshore wind-turbine (OWT) support structures are subjected to cyclic dynamic loads with variations in loadings from wind and waves as well as the rotation of blades throughout their lifetime. The magnitude and extent of the cyclic loading can create a fatigue limit state controlling the design of support structures. In this paper, the remaining fatigue life of the support structure for a GE Haliade 6 MW fixed-bottom jacket offshore wind turbine within the Block Island Wind Farm (BIWF) is assessed. The fatigue damage to the tower and the jacket support structure using stress time histories at instrumented and non-instrumented locations are processed. Two validated finite-element models are utilized for assessing the stress cycles. The modal expansion method and a simplified approach using static calculations of the responses are employed to estimate the stress at the non-instrumented locations—known as virtual sensors. It is found that the hotspots at the base of the tower have longer service lives than the jacket. The fatigue damage to the jacket leg joints is less than 20% and 40% of its fatigue capacity during the 25-year design lifetime of the BIWF OWT, using the modal expansion method and the simplified static approach, respectively. [ABSTRACT FROM AUTHOR]

Magnesium matrix composites are essential lightweight metal matrix composites, following aluminum matrix composites, with outstanding application prospects in automotive, aerospace lightweight and biomedical materials because of their high specific strength, low density and specific stiffness, good casting performance and rich resources. However, the inherent low plasticity and poor fatigue resistance of magnesium hamper its further application to a certain extent. Many researchers have tried many strengthening methods to improve the properties of magnesium alloys, while the relationship between wear resistance and plasticity still needs to be further improved. The nanoparticles added exhibit a good strengthening effect, especially the ceramic nanoparticles. Nanoparticle-reinforced magnesium matrix composites not only exhibit a high impact toughness, but also maintain the high strength and wear resistance of ceramic materials, effectively balancing the restriction between the strength and toughness. Therefore, this work aims to provide a review of the state of the art of research on the matrix, reinforcement, design, properties and potential applications of nano-reinforced phase-reinforced magnesium matrix composites (especially ceramic nanoparticle-reinforced ones). The conventional and potential matrices for the fabrication of magnesium matrix composites are introduced. The classification and influence of ceramic reinforcements are assessed, and the factors influencing interface bonding strength between reinforcements and matrix, regulation and design, performance and application are analyzed. Finally, the scope of future research in this field is discussed. [ABSTRACT FROM AUTHOR]

In recent years, asphalt pavement has been subjected to varied environmental conditions during its service life, conditions that predispose it to deformation and cracking. To enhance the performance of asphalt pavement, rock asphalt has been selected as a modifier due to its good compatibility with virgin asphalt binder and its ability to improve the fatigue cracking resistance of asphalt mixtures. Although scholars have conducted some studies on rock asphalt mixtures, research on the fatigue and self-healing performance of these mixtures under conditions such as ultraviolet (UV) aging and freeze–thaw remains limited. This paper presents findings from a study that employs a combined fatigue-healing test to assess the impact of such complex environmental factors on the fatigue and self-healing properties of fine aggregate matrix (FAM) mixtures containing three types of rock asphalts, i.e., Buton, Qingchuan (QC), and Uintaite Modifier (UM). The analysis of fatigue-healing test results, grounded in viscoelastic continuum damage (VECD) theory, indicates that rock asphalt can extend the fatigue life of FAM mixtures, albeit with a concomitant decrease in their self-healing capabilities. The study further reveals that UV aging, freeze–thaw, and UV aging–freeze–thaw conditions all led to a diminution in the fatigue and self-healing properties of FAM mixtures. However, FAM mixtures containing rock asphalt demonstrated greater resilience against these reductions. Atomic force microscope (AFM) results indicate that UV aging reduced the number of bee-structures and enlarged their area, whereas the incorporation of rock asphalt enhanced the uniformity of these structures' distribution, thereby improving the fatigue cracking resistance of FAM mixtures. Fourier transform infrared spectroscopy (FTIR) analysis reveals that while UV aging increased the carbonyl and sulfoxide indices within the asphalt binder, rock asphalt is effective in mitigating this effect to a certain degree, thereby enhancing the aging resistance of FAM mixtures. [ABSTRACT FROM AUTHOR]

Reversible optical regulation has potential applications in optical anti-counterfeiting, storage, and catalysis. Compared to common power materials, the reverse opal structure has a larger specific surface area and an increased contact area for optical regulation, which is expected to achieve higher regulation rates. However, it is difficult to achieve reversible and repeatable regulation of the luminescent properties of photonic crystals, especially with the current research on the structural collapse of photonic crystals. In this work, WO3: Yb3+, Er3+ inverse photonic crystals were prepared by the template approach, and reversible multi-mode optical modification was investigated. Upon heat treatment in a reducing atmosphere or air, the color of the photonic crystals can reversibly change from light yellow to dark green, accompanied by changes in absorption and upconversion of luminescence intensity. The stability and fatigue resistance of this reversible optical modification ability were explored through cyclic experiments, providing potential practical applications for photocatalysis, optical information storage, and electrochromism. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of the low-cycle fatigue (LCF) properties of C45, X20Cr13, and 34CrNiMo6 steels subjected to various heat treatment processes. Strain-controlled LCF tests were carried out with a total cyclic strain amplitude equal to 0.5, 1 and 1.5%. Fatigue life, cyclic stress-strain behavior and hardness were analyzed. Qualitative and quantitative relationships between material LCF properties resulting from the heat treatment processes, were related to the indentation force P*, which was derived experimentally by applying an instrumented indentation procedure with the use of the Vickers indenter. The proposed parameter P* and its changes ΔP* seem to be promising for the identification of the structural stress parameter σ* that is necessary for deriving values of the fatigue strength coefficients σf' corresponding to different tempering temperatures. The common feature of all steels analyzed in this paper is that the elastic parts of the strain-life characteristics remain parallel after being subjected to different tempering temperatures. [ABSTRACT FROM AUTHOR]

The fatigue behavior of a high-strength bearing steel tempered under three different temperatures was investigated with ultrasonic frequency and conventional frequency loading. Three kinds of specimens with various yield strengths exhibited obvious higher fatigue strengths under ultrasonic frequency loading. Then, a 2D crystal plasticity finite element method was adopted to simulate the local stress distribution under different applied loads and loading frequencies. Simulations showed that the maximum residual local stress was much smaller under ultrasonic frequency loading in contrast to that under conventional frequency at the same applied load. It was also revealed that the maximum local stress increases with the applied load under both loading frequencies. The accumulated plastic strain was adopted as a fatigue indicator parameter to characterize the frequency effect, which was several orders smaller than that obtained under conventional loading frequencies when the applied load was fixed. The increment of accumulated plastic strain and the load stress amplitude exhibited a linear relationship in the double logarithmic coordinate system, and an improved fatigue life prediction model was established. [ABSTRACT FROM AUTHOR]

The resistance of nickel–titanium endodontic instruments against cyclic fatigue failure remains a significant concern in clinical settings. This study aimed to assess the cyclic fatigue strength of five nickel–titanium rotary systems, while correlating the results with the instruments' geometric and metallurgical characteristics. A total of 250 new instruments (sizes S1/A1, S2/A2, F1/B1, F2/B2, F3/B3) from ProTaper Gold, ProTaper Universal, Premium Taper Gold, Go-Taper Flex, and U-Files systems underwent mechanical testing. Prior to experimental procedures, all instruments were meticulously inspected to identify irregularities that could affect the investigation. Using a stereomicroscope, design characteristics such as the number of spirals, length, spirals per millimeter, and average helical angle of the active blade were determined. The surface finishing characteristics of the instruments were examined using a scanning electron microscope. Differential scanning calorimetry was employed to establish the instruments' phase transformation temperatures, while energy-dispersive X-ray spectroscopy was utilized to analyze the elemental composition of the alloy. The instruments were subjected to cyclic fatigue testing within a stainless steel non-tapered artificial canal featuring a 6 mm radius and 86 degrees of curvature. Appropriate statistical tests were applied to compare groups, considering a significance level of 0.05. The assessed design characteristics varied depending on the instrument type. The least irregular surface finishing was observed in U-Files and Premium Taper Gold files, while the most irregular surface was noted in Go-Taper Flex. All instruments exhibited near-equiatomic proportions of nickel and titanium elements, whereas ProTaper Universal and U-Files instruments demonstrated lower phase transformation temperatures compared to their counterparts. Larger-sized instruments, as well as ProTaper Universal and U-Files, tended to display lower cyclic fatigue strength results. Overall, the design, metallurgical, and cyclic fatigue outcomes varied among instruments and systems. Understanding these outcomes may assist clinicians in making more informed decisions regarding instrument selection. [ABSTRACT FROM AUTHOR]

Bismuth titanate (BIT) is widely known as one of the most prospective lead‐free ferroelectric and piezoelectric materials in advanced high‐temperature sensing applications. Despite significant advances in developing BIT ferroelectrics, it still faces major scientific and engineering challenges in realizing super‐high performance to meet next‐generation high‐sensitivity and light‐weight applications. Here, a novel ferroelectric domain‐engineered BIT ceramic system is conceived that exhibits super‐high piezoelectric coefficient (d33 = 38.5 pC N−1) and inverse piezoelectric coefficient (d33* = 46.7 pm V−1) at low electric field as well as excellent fatigue resistance (stable up to 107 cycles). The results reveal that the introduction of high‐density layered (001)‐type 180° domain walls with flexible polarization rotation features and the formation of small‐size multi‐domain states with low energy barriers are mainly responsible for the excellent electrical performance. To the best of knowledge, it is the first time to reveal such intriguing domain structures in BIT ceramics in detail, especially from the atomic‐scale perspective by using atomic number (Z)‐contrast imaging in combination with atomic‐resolution polarization mapping. It is believed that this breakthrough conduces to comprehensively understand structural features of ferroelectric domains in BIT ceramics, and also opens a window for future developments of super‐high performance in bismuth layer‐structured ferroelectrics via domain engineering. [ABSTRACT FROM AUTHOR]

As ferroelectrics hold significance and application prospects in wearable devices, the elastification of ferroelectrics becomes more and more important. Nevertheless, achieving elastic ferroelectrics requires stringent synthesis conditions, while the elastification of relaxor ferroelectric materials remains unexplored, presenting an untapped potential for utilization in energy storage and actuation for wearable electronics. The thiol‐ene click reaction offers a mild and rapid reaction platform to prepare functional polymers. Therefore, we employed this approach to obtain an elastic relaxor ferroelectric by crosslinking an intramolecular carbon‐carbon double bonds (CF=CH) polymer matrix with multiple thiol groups via a thiol‐ene click reaction. The resulting elastic relaxor ferroelectric demonstrates pronounced relaxor‐type ferroelectric behaviour. This material exhibits low modulus, excellent resilience, and fatigue resistance, maintaining a stable ferroelectric response even under strains up to 70 %. This study introduces a straightforward and efficient approach for the construction of elastic relaxor ferroelectrics, thereby expanding the application possibilities in wearable electronics. [ABSTRACT FROM AUTHOR]

As ferroelectrics hold significance and application prospects in wearable devices, the elastification of ferroelectrics becomes more and more important. Nevertheless, achieving elastic ferroelectrics requires stringent synthesis conditions, while the elastification of relaxor ferroelectric materials remains unexplored, presenting an untapped potential for utilization in energy storage and actuation for wearable electronics. The thiol‐ene click reaction offers a mild and rapid reaction platform to prepare functional polymers. Therefore, we employed this approach to obtain an elastic relaxor ferroelectric by crosslinking an intramolecular carbon‐carbon double bonds (CF=CH) polymer matrix with multiple thiol groups via a thiol‐ene click reaction. The resulting elastic relaxor ferroelectric demonstrates pronounced relaxor‐type ferroelectric behaviour. This material exhibits low modulus, excellent resilience, and fatigue resistance, maintaining a stable ferroelectric response even under strains up to 70 %. This study introduces a straightforward and efficient approach for the construction of elastic relaxor ferroelectrics, thereby expanding the application possibilities in wearable electronics. [ABSTRACT FROM AUTHOR]

Metal Matrix Composites (MMCs) have recently been preferred over traditional materials in many engineering applications. Titanium matrix composites (TMCs) are used in the automotive, aerospace and defence industries thanks to their exceptional strength, high fatigue strength, good corrosion resistance and high elastic modulus. Some of the most used reinforcement materials for TMCs are SiC, Zr 2 O 3 , Al 2 O 3 , graphene, carbon nanotube (CNT) and TiC. In this study, TMCs reinforced Al 2 O 3 were produced via conventional powder metallurgy (PM) and ultrasonic-assisted mixing. An Al 2 O 3 in varying amounts (5 and 10 wt%) was incorporated into the TMCs via mechanical alloying (MA) for 5 h in a high-energy ball mill and using different process control agents (PCA, Stearic acid (SA), Polyvinyl Alcohol (PVA), Ethanol). The mechanically alloyed (MA'ed) powders were compacted by a hydraulic press under uniaxial pressure of 450 MPa and sintered at 1200 °C for 2 h in an argon atmosphere. The microstructural, mechanical and tribological properties of Ti-xAl 2 O 3 powders and bulk samples were investigated. The highest hardness and the lowest specific wear rate were found in specimens reinforced with 5 wt% Al 2 O 3 , using ethanol as PCA, and produced by ultrasonic-assisted mixing, but the same specimen had the lowest compressive strength. [ABSTRACT FROM AUTHOR]

The force drop after transcranial magnetic stimulation (TMS) delivered to the motor cortex during voluntary muscle contractions could inform about muscle relaxation properties. Because of the physiological relation between skeletal muscle fibertype distribution and size and muscle relaxation, TMS could be a noninvasive index of muscle relaxation in humans. By combining a noninvasive technique to record muscle relaxation in vivo (TMS) with the gold standard technique for muscle tissue sampling (muscle biopsy), we investigated the relation between TMS-induced muscle relaxation in unfatigued and fatigued states, and muscle fiber-type distribution and size. Sixteen participants (7F/9M) volunteered to participate. Maximal knee-extensor voluntary isometric contractions were performed with TMS before and after a 2-min sustained maximal voluntary isometric contraction. Vastus lateralis muscle tissue was obtained separately from the participants’ dominant limb. Fiber type I distribution and relative cross-sectional area of fiber type I correlated with TMS-induced muscle relaxation at baseline (r = 0.67, adjusted P = 0.01; r = 0.74, adjusted P = 0.004, respectively) and normalized TMS-induced muscle relaxation as a percentage of baseline (r = 0.50, adjusted P = 0.049; r = 0.56, adjusted P = 0.031, respectively). The variance in the normalized peak relaxation rate at baseline (59.8%, P < 0.001) and in the fatigue resistance (23.0%, P = 0.035) were explained by the relative cross-sectional area of fiber type I to total fiber area. Fiber type I proportional area influences TMS-induced muscle relaxation, suggesting TMS as an alternative method to noninvasively inform about skeletal muscle relaxation properties. NEW & NOTEWORTHY Transcranial magnetic stimulation (TMS)-induced muscle relaxation reflects intrinsic muscle contractile properties by interrupting the drive from the central nervous system during voluntary muscle contractions. We showed that fiber type I proportional area influences the TMS-induced muscle relaxation, suggesting that TMS could be used for the noninvasive estimation of muscle relaxation in unfatigued and fatigued human muscles when the feasibility of more direct method to study relaxation properties (i.e., muscle biopsy) is restricted. [ABSTRACT FROM AUTHOR]

Functionally graded materials (FGM) with indistinct boundaries potentially eliminate the damaging stresses occurring at the interfaces. FGM applications in dental ceramics have enhanced their fatigue resistance and interfacial toughness. This scoping review aims to map graded designs in dental ceramics, distinguish their methodological approaches with their material characteristics and properties, and understand the factors affecting the outcomes of each of the graded approaches. A systematic electronic search was performed with the databases MEDLINE (PubMed), Scopus, Cochrane Library, EBSCO, and Google Scholar along with a manual search. About 2675 articles were initially found from all the searches with no date restriction till July 2023. After rejecting duplicates and based on exclusion criteria, about 52 articles were included. Methodological approaches in grading such as glass-infiltration and silica-infiltration have been investigated on pre-sintered zirconia. The type of infiltration and the method of infiltrate application significantly influenced the phase transformation of zirconia, its microstructure, surface hardness, fracture toughness, flexural strength, wear, and fatigue strength of graded dental zirconia. Interlayers were accommodated between metal-ceramic and veneer-core all-ceramic layers. Fractions of zirconia-porcelain and alumina-porcelain showed high bending strength and better stress distribution. The results of finite element analysis studies predicted that using 10-layered graded layers reduced the stresses at the crown-cement-dentin interface. [Display omitted] [ABSTRACT FROM AUTHOR]

Evaluation of significant parameters influencing the fatigue strength of typical details – experimental investigations The phenomenon of fatigue plays a significant role in many constructions of modern infrastructure. Therefore, the fatigue assessment of steel structures is of great importance. In order to make fatigue design acc. to DIN EN 1993‐1‐9 more efficient, important influencing factors on the fatigue strength of standard fatigue details were analyzed in the research project EVOKERB. This contribution presents the corresponding experimental research results, with a focus on influences related to geometry, manufacturing, and weld quality. In addition, test data from the literature are included through a soon‐to‐be‐publicly‐available fatigue test database. The database comprises the essential background data of DIN EN 1993‐1‐9. In summary, the presented test results identify or exclude important influences on the fatigue strength of typical details. In the future, the scope of investigations will be expanded through numerical simulations, allowing for the derivation of general normative rules. These rules are intended to contribute to a more efficient fatigue assessment – an important step towards greater resource efficiency and sustainability in steel construction. [ABSTRACT FROM AUTHOR]

Hot spot stress on circular hollow section joints – methods in comparison For the assessment of the fatigue strength of tubular joints, the structural stress concept is predominantly used. The structural stress can be determined using various methods. In this regard, the surface extrapolation method is mainly applied. Accordingly, this procedure is well established in normative specifications. In the frame of this contribution, in addition to this approach, the concept of through‐thickness linearization is elucidated, as only less detailed application guidelines are provided in the relevant standards. Furthermore, an alternative approach is presented, which in principle allows a direct extraction of structural stresses from the computational model. In order to assess the comparability and the validity of this methods, investigations were conducted on K‐, Y‐, and KK‐joints. The results are subsequently compared. [ABSTRACT FROM AUTHOR]

Current insights of the use of adhesive in preloaded bolted connections considering manufacturing influences Not predominantly static loaded structures in steel construction are preferably executed with slip‐resistant connections since they exhibit a high resistance against fatigue. Nevertheless, the transferable shear loads are limited. With additionally applied adhesive on the friction surfaces, the so‐called preloaded hybrid connection is formed. The related increase of load capacity considering various manufacturing influences and the load‐bearing behaviour under permanent load as well as under the influence of temperature is presented in the following article. [ABSTRACT FROM AUTHOR]

Restoration of the concrete and glass windows of St. Mauritius Church in accordance with the preservation requirements The development of repair systems for use on heritage‐listed concrete structures represents a major challenge in terms of materials and aesthetics. The reinforced concrete structures of the St. Mauritius Church in Wiesbaden, in particular the artistically designed concrete and glass window bands, are severely corroded and need to be repaired. Based on historical data collections and visual inspections of the degree of damage to these window bands, a restoration approach was developed to extend the service life of the glass surrounds under current conditions of use. Taking into account the material compatibility, dedicated fiber‐reinforced concretes were developed for the repair. Care was taken to ensure that the materials used were matched to each other in order to achieve an optimized packing density. In this way, a similar structural density was achieved for the repair concrete as for high‐strength or ultra‐high performance concretes. The physical and mechanical properties were adapted to the old concrete; especially compressive strength, flexural strength and adhesive tensile strength as well as the modulus of elasticity, shrinkage, thermal fatigue resistance and water absorption. It was experimentally proven that fiber reinforcement significantly improves the adhesive tensile strength of the repair concrete and increases its durability. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review of natural fiber-reinforced composites (NFRCs) for lower-limb prosthetic designs. It covers the characteristics, types, and properties of natural fiber-reinforced composites as well as their advantages and drawbacks in prosthetic designs. This review also discusses successful prosthetic designs that incorporate NFRCs and the factors that make them effective. Additionally, this study explores the use of computational biomechanical models to evaluate the effectiveness of prosthetic devices and the key factors that are considered. Overall, this document provides a valuable resource for anyone interested in using NFRCs for lower-limb prosthetic designs. [ABSTRACT FROM AUTHOR]

This study investigates the interaction between static and fatigue strength and the rheological properties of acrylonitrile–butadiene–styrene (ABS) polymer reinforced with graphene nanoplatelets (GNPs) in both filament and 3D-printed forms. Specifically focusing on the effects of 1.0 wt.% GNPs, the study examines their influence on static/fatigue responses. The rheological behaviour of pure ABS polymer and ABS/GNPs nanocomposite samples, fabricated through material extrusion, is evaluated. The results indicated that the addition of 1.0 wt.% GNPs to the ABS matrix improved the elastic modulus of the nanocomposite filaments by up to about 34%, while reducing their ductility by approximately 60%. Observations revealed that the static and fatigue responses of the composite filament materials and 3D-printed parts were not solely attributed to differences in mechanical properties, but were also influenced by extrusion-related process parameters. The shark-skin effect, directly related to the material's rheological properties, had a major impact on static strength and fatigue life. The proposed method involved adjusting the temperature of the heating zones of the extruder during filament production to enhance the static response of the filament and using a higher nozzle temperature (270 °C) to improve the fatigue life of the 3D-printed samples. The findings reveal that the proposed parameter optimisation led to filaments with minimised shark-skin effects, resulting in an improvement in ultimate tensile strength compared to pure ABS. Moreover, the 3D-printed samples produced with a higher nozzle temperature exhibited increased fatigue lives compared to those manufactured under identical conditions as pure ABS. [ABSTRACT FROM AUTHOR]

The positive effects of deep rolling on fatigue strength—reduced surface roughness, work hardening and compressive residual stress—in the near-surface region are achieved by controlled high plasticisation of the treated material. However, excessive and/or repeated plasticising poses a risk of damage to the machined component. This paper investigates the damage caused by deep rolling of a railway axle. Two sections of the axle are experimentally deep rolled repeatedly at different feed rates until damage is detected. For comparative analysis, these experiments are numerically analysed and the damage is assessed using the strain-based damage calculation. The results are compared and a damage sum of ~120% is evaluated for both tests, thus developing a reliable and conservative assessment method. The single deep rolling treatment at a feed rate of 0.25 mm causes damage of 6.1%, and at a feed rate of 0.5 mm, damage of 4.7%. The developed and experimentally validated evaluation method allows for investigating the limits of applicability of different deep rolling parameters. The influence of the deep rolling force and feed rate and a proposed optimisation with multiple deep rolling with reduced deep rolling forces are investigated. [ABSTRACT FROM AUTHOR]

The reliability of friction stir welded joints is a critical concern, particularly given their potential applications in the aerospace manufacturing industry. This study offers a quasi-in situ observation of the microstructural response during fatigue crack growth (FCG) of a friction stir welded AA2024-T4 joint, aiming to correlate fatigue crack growth behavior with mechanical properties investigated using electron backscatter diffraction (EBSD). Notched compact tension (CT) specimens corresponding to the morphology of the stir zone (SZ), advancing side (AS), and retreating side (RS) were meticulously designed. The findings indicate that the welding process enhances the joint's resistance to fatigue crack growth, with the base metal exhibiting a shorter fatigue life (i.e., ~105 cycles) compared to the welding zones (SZ ~ 3.5 × 105 cycles, AS ~ 2.5 × 105 cycles, and RS ~ 3.0 × 105 cycles). Crack propagation occurs within the stir zone, traversing refined grains, which primarily contribute to the highest fatigue life and lowest FCG rate. Additionally, cracks initiate in AS and RS, subsequently expanding into the base metal. Moreover, the study reveals a significant release of residual strain at the joint, particularly notable in the Structural-CT-RS (Str-CT-RS) sample compared to the Str-CT-AS sample during the FCG process. Consequently, the FCG rate of Str-CT-AS is higher than that of Str-CT-RS. These findings have significant implications for improving the reliability and performance of aerospace components. [ABSTRACT FROM AUTHOR]

In this study, a series of impact-induced rockburst experiments were carried out by applying multilevel cyclic stresses on a cubic sandstone with a circular opening. Information on rockburst evolution was monitored using video and AE techniques together. Experimental results show that the opening in the sandstone sample was observed to undergo rock grain ejection, rock spalling and buckling in sequence. AE activity under the lower cyclic stress level followed the Kaiser's effect, while the Felicity's effect of AE was also involved at the higher cyclic stress level. Multi-axial cyclic loading can shorten the fatigue life and fatigue strength of the sandstone sample. However, the multi-axial cyclic loading can obviously reduce the AE hits and its energy rate, in which case the proportion of the AE single with low frequency is less than those under the uni-axial cyclic compression. It is also found that the failure zone in the sandstone is characterized by V-shaped notch. The depth of the failure zone is reduced sequentially under uni-axial, bi-axial, and tri-axial cyclic compression, respectively. In contrast, the extent angle of the failure zone will increase. According to the observed profiles of the failure zone, the changes of friction angle of the sandstone are interpreted by the Mohr–Coulomb strength criterion, as well as movement of the failure line due to the fatigue damage. These findings can provide insights into the study of rock failure mechanisms under various dynamic disturbances. Highlights: Impact-induced rockburst in laboratory was simulated by applying uniaxial, bi-axial, and tri-axial cyclic loadings, respectively to cubic sandstone samples with an opening. The opening in the sandstone sample was observed to undergo rock grain ejection, rock spalling and buckling in sequence. AE activity under the lower cyclic stress level can be explained by the Kaiser's effect, while the Felicity's effect of AE was also involved at the higher cyclic stress level. Failure zone around the opening in the sandstone was characterized by V-shaped notch, whose depth of the failure zone was reduced sequentially under uni-axial, bi-axial, and tri-axial cyclic compression. [ABSTRACT FROM AUTHOR]

Recently developed Nickel-Titanium (NiTi) instruments with practical changes have resulted in safer instrumentation. In addition, topographical features on the file surface are a contributing factor to clinical durability. Therefore, this study aimed to investigate both the cyclic fatigue resistance and the roughness change of MTwo and Rotate instruments (VDW, Munich, Germany). Each instrument (n = 6/each group) was scanned with an atomic force microscopy prior to and after instrumentation. In addition, cyclic fatigue testing was conducted for each instrument (n = 11/each group) with stainless-steel blocks, including 45°-60°-90° degrees of curvature milled to the instruments' size. The roughness parameters increased for both systems after instrumentation (p<0.05). Both systems presented an increased roughness following instrumentation (p<0.05). The cyclic fatigue resistance was lowest at 90° for both systems (p<0.05), whereas the Rotate files presented a higher resistance than that of the Mtwo files (p<0.05). Compared to the Mtwo files, Rotate files presented better resistance, while the resistance decreased as the curvature increased. [ABSTRACT FROM AUTHOR]

This study examines the effects of minor variations in the building angle of 3D‐printed AlSi10Mg components on mechanical properties under different processing and postprocessing conditions (as‐built [AB], stress relief [SR], and platform heating [HP]). Beginning with tensile tests to determine stress ranges for subsequent fatigue experiments, findings indicate that the building angle significantly impacts tensile strength, yield strength, and ultimate strain, rising with inclining angles. However, Young's modulus remains unaffected. High‐cycle fatigue testing at stress amplitudes below yield strength values reveals differences in S‐N fatigue curves among AB, SR, and HP conditions. While the building angle's influence is not statistically significant, AB samples exhibit lower fatigue resistance than SR and HP counterparts. HP samples perform similarly to SR at high stress levels but notably worse at low stress values. The developed multiple linear regression model shows reasonable accuracy, with 84% of predictions within ±2‐factor and 97.2% within ±3‐factor. Highlights: Tensile strength and ultimate strain increase with inclining building angles.Eighty‐four percent of the predictions of regression model fell within the ±2‐factor error range.The fracture surface shows the crack initiation and propagation area, and the final fracture zone.The fatigue crack originated near the surface shows the presence of multiple initiation spots. [ABSTRACT FROM AUTHOR]

The stress intensity factor (SIF) distribution of a semi‐elliptical surface crack is often used for evaluating the fatigue strength of structures. Virtually exact distributions of SIFs FISE,FIISE,FIIISE can be provided along the crack front by solving the hypersingular integral equation of the body force method. In this paper, to create a very accurate SIF variation formula, the elliptical crack SIF solutions FIE, FIIE, FIIIE are used and the SIF ratios FISE/FIE, FIISE/FIIE, FIIISE/FIIIE are mainly focused. Paying attention to the corner point singularity, by applying the least squares method to the ratio FISE/FIE, FIISE/FIIE in the whole range of parametric angle β, FISE and FIISE formulas can be proposed. Instead, FIIISE formula can be proposed by applying the method of least squares to the ratio of FIIISE/FIIIE in the range β≥15° but applying directly to FIIISE in the range β≤15°. In this way, all of formulas proposed in this paper provide the SIFs with better than 1.0% accuracy. Highlights: Accurate SIF formulas for semi‐elliptical surface cracks were created within 1% error.Similar to solving the HIEM, closed form solutions of an elliptical crack were utilized.This formula assume the crack front intersects the free surface at an angle θS≅100.5°.Using singularity r‐0.5 along the crack front, the shape FISE(β)≈const. was investigated. [ABSTRACT FROM AUTHOR]

To provide more suggestions for the anti‐fatigue design of cold‐formed steel, a series of high‐cycle fatigue tests are carried out on cold‐rolled steel sheets connected by self‐tapping screws and blind rivets in this paper. Subsequently, fatigue failure mode, fatigue strength, and fatigue damage are analyzed in detail. The test results show that all effective data points are below the S‐N curve of screws in the code. Meanwhile, the fatigue limit values of the fitted curves with 95% survival probability fall within the range of 0.3 to 0.67 times the specified value. Besides, the fatigue damage expansion rate of cold‐rolled steel sheets is less than the standard value. Through further discussion, it is noticed that metal grade has little influence on the fatigue performance, while thickness has a significantly positive influence on the shear resistance and fatigue performance. Moreover, the fatigue performance of the two connection types appears to be similar. [ABSTRACT FROM AUTHOR]

This paper focuses on the effect of laser shock peening on the rotational bending fatigue life of S51740 stainless steel round bar specimens. The improvement of material properties by laser shock peening is investigated by combining simulation calculations and experiments. The main results are as follows: Finite element simulations yielded three sets of laser process parameters for the study (LPS-1, LSP-2, LSP-3). The fatigue test results show that laser impact strengthening can effectively improve the fatigue life of the material, and compared with the unenhanced specimens, 350% increase in fatigue life of LSP-2 specimens. EBSD analysis showed that the LSP-2 specimen performed the best. It was verified that the material properties of S51740 stainless steel were greatly improved when the laser process parameter was LSP-2. [ABSTRACT FROM AUTHOR]

The use of three‐dimensional (3D) printing technology for producing continuous fiber‐reinforced composites has given us the freedom to fabricate individual designs and lightweight composite structures with improved specific strength, modulus, and fatigue resistance. In this direction, utilizing in‐nozzle impregnation, 3D‐printed continuous cotton fiber (CCoF) reinforced poly lactic acid (PLA) bio‐composites have been fabricated, and the influence of varying layer widths (i.e., 0.5, 0.6, 0.7, and 0.8 mm) on the mechanical performance of the CCoF‐PLA composites was investigated. Results revealed that 3D printing of PLA/CCoF at 0.5 mm layer width enhanced the tensile and flexural strength by 1.2 times and 3.1 times compared with 3D printed neat PLA specimens. The relationships between layering width—microstructural characteristics—mechanical properties of PLA/CCoF composite were quantitatively analyzed based on experimental results. Highlights: CCoF‐reinforced PLA composites fabricated through a 3D printing routine.CCoF/PLA samples were fabricated at different layer widths (0.5, 0.6, 0.7, and 0.8 mm).Better mechanical performance is achieved at 0.5 mm layer width.σy and UTS of composites enhanced by 1.19 times and 1.87 times, respectively.Ef of composites printed at 0.5 mm layer width enhanced by two times. [ABSTRACT FROM AUTHOR]

Background: Rheumatoid Arthritis (RA), an autoimmune systemic inflammatory disease, affects more than 17 million people globally. People with RA have higher risk of premature mortality; often experience chronic fatigue, pain and disrupted sleep; and are less physically active and more sedentary than healthy counterparts. It remains unclear how people with RA may balance sleep and awake movement activities over 24-hours, or how differences in 24-hour behaviours may be associated with determinants of health, or alignment with published activity guidelines. Methods: Cross-sectional exploration of objective measures of 24-hour sleep-wake activities in 203 people with RA. Latent Class Analysis (LCA) derived classes from time, by tertile, in six sleep-awake activities over 24 h. Comparisons of model fit statistics, class separation and interpretability defined best fit for number of classes. Variations in sleep-awake behaviour across classes and association of profile allocation with determinants of health, quality metrics for sleep, sitting and walking and alignment with published guidelines were explored. Multinomial logistic regression identified factors associated with likelihood of profile allocation. Results: LCA identified 2 to 6 classes and a 4-class model was determined as best fit for 24-hour sleep-awake behaviour profiles. One profile (26%) presented with more balanced 24-hour sleep, sitting and walking behaviours. The other three profiles demonstrated progressively less balanced 24-hour behaviours including: having low (< 7 h), high (> 8 h), or recommended (7–8 h) sleep duration in respective combination with high sitting (> 10 h), limited walking (< 3 h) or both when awake. Age, existing sitting and walking habit strength and fatigue were associated with likelihood of belonging to different profiles. More balanced 24-hour behaviour was aligned with better quality metrics for sleep, sitting and walking and published guidelines. Discussion: For people living with RA it is important to understand the 'whole person' and their 'whole day' to define who may benefit from support to modify 24-hour sleep-awake behaviours and which behaviours to modify. Supports should be informed by an understanding of personal or health-related factors that could act as barriers or facilitators for behavioural change, including exploring existing habitual sitting and walking behaviours. Trial registrations: ClinicalTrials.gov ID: NCT02554474 (2015-09-16) and ClinicalTrials.gov ID: NCT03404245 (2018-01-11) [ABSTRACT FROM AUTHOR]

Coal gangue is a byproduct of coal mining and processing, and according to incomplete statistics, China has amassed a substantial coal gangue stockpile exceeding 2600 large mountains, which poses a serious threat to the ecological environment. Utilizing gangue as a coarse aggregate to produce gangue concrete (GC) presents a promising avenue for addressing the disposal of coal gangue; however, gangue concrete presents several challenges that need to be tackled, such as low strength and poor resistance to repeated loads. In this study, polypropylene fibers (PPFs) were incorporated into gangue concrete to enhance its utilization rate. Uniaxial compressive and repeated loading experiments were then conducted to investigate the uniaxial strength and fatigue properties of polypropylene fiber-reinforced gangue concrete (PGC) with varying gangue substitution rates (20%, 40%, and 60%) and different polypropylene fiber admixtures (0, 0.1%, 0.2%, and 0.3%). The findings indicate that incorporating gangue at a substitution rate of 40% could notably enhance the uniaxial compressive strength of PGC, resulting in a maximum increase of 19.4%. In the repeated loading experiments, the ductility of PGC was enhanced with the incorporation of PPFs, resulting in a reduction of 33.76% in the damage factor and 19.42% in residual strain for PGC-40-0.2 compared to PGC-40-0. A PPF content of 0.2% was found to be optimal for enhancing the fatigue performance of PGC. Scanning electron microscope (SEM) testing proved the improvement effect of polypropylene fiber on gangue concrete from a microscopic perspective. This study provides crucial experimental data and a theoretical foundation for the utilization of gangue concrete in complex stress environments. [ABSTRACT FROM AUTHOR]

This study introduces a Finite Element (FE) hybrid methodology for analyzing deepwater offshore oil and gas floating production systems. In these systems, flexible risers convey the production and are connected to a balcony on one side of the platform. The proposed methodology couples, in a cost-effective manner, the hydrodynamic model of the platform with the FE model that represents the risers and the mooring lines, considering all nonlinear dynamic interactions. The results obtained and the associated computational performance are then compared with those from traditional uncoupled analyses, which may present inaccurate results for deepwater scenarios, and from fully coupled analyses that may demand high computational costs. Moreover, particular attention is dedicated to integrating global and local stress analyses to calculate the fatigue resistance of the flexible riser. The results demonstrate that the coupled global analyses adequately capture the asymmetric behavior due to all risers being connected to one of the sides of the platform, thus resulting in a more accurate distribution of fatigue damage when compared to the uncoupled methodology. Also, fatigue life is significantly affected by adequately considering the coupling effects. [ABSTRACT FROM AUTHOR]

The low-temperature fatigue crack propagation rate of 925A steel, as a rudder steel for polar special ships, has a crucial impact on the evaluation of the fatigue strength of polar ships. The purpose of this article is to study the fatigue crack propagation rate of 925A steel under different low-temperature conditions from room temperature (RT) to −60 °C. The material was subjected to fatigue crack propagation tests and stress intensity factor tests. The experimental tests were conducted according to the Chinese Standard of GB/T6398-2017. The results show that as the temperature decreases, the lifespan of 925A increases. Within a certain stress intensity factor, as the temperature decreases, the fatigue crack propagation rate decreases. At −60 °C, it exhibits ductile fracture; within normal polar temperatures, it can be determined that 925A meets the requirements for low-temperature fatigue crack propagation rates in polar regions. However, in some extreme polar temperatures below −60 °C, preventing brittle failure becomes a key focus of fatigue design. Finally, the fatigue crack propagation behavior at the microscale of 925A steel at low temperatures was described using fracture morphology. The experimental data can provide reference for the design of polar ships to further resist low-temperature fatigue and cold brittle fracture. [ABSTRACT FROM AUTHOR]

Bridge cable wires suffer from alternating stress and environmental erosion, leading to premature failure prior to its design life. This paper investigates the fatigue and mechanical behaviors of corroded bridge cable wires with a zinc–aluminum (Zn-Al) alloy coating. Based on the salt spray corrosion test and microstructure analysis, the anti-corrosion resistance and corrosion appearance characteristics of the Zn-Al alloy coating and galvanized coating were investigated. The Zn-Al alloy coating was superior in resistance to corrosion fatigue for the improvement in toughness and the generation of anti-corrosion Zn-Al and Fe-Zn-Al phases. Equations of the accelerated corrosion depth of the steel wires had been regressed to roughly estimate the corrosion life of the Zn-Al alloy coating, which can reach 29.1 years with a thickness of 70 μm. The fatigue and mechanical properties of the bare wires after the salt spray test were further studied based on tensile tests and fatigue tests. The fatigue properties of the bridge cable wire would decrease with the corrosion degree due to the deterioration and embrittlement of materials, where ductility characterized by the elongation rate was the most affected. Fracture surfaces of the wires were captured and analyzed based on a method for recognizing graphical contours. Insufficient fatigue life may occur in the steel wires after corrosion and increase with the degree of corrosion. The pit depth logarithmically weakened the fatigue life of steel wires for the weakening of fatigue toughness and the bearing area. The flat fracture was more common with a single fatigue source, while multiple fatigue sources led to step-like fractures for the generation of multiple dispersed crack propagation regions. Corrosion fatigue was more sensitive to the existence of fatigue sources than the reduction. Multiple initiation sources significantly reduced the fatigue life due to the cracking facilitation of the joint effect of multiple pits. The electrochemical reactions of corrosion can lead to material embrittlement and a reducing effect on the fracture toughness of the steel wires. [ABSTRACT FROM AUTHOR]

In recent years, assembled bridges have become widely utilized in bridge construction, raising concerns about durability-related bridge diseases over time. These issues significantly impact the fatigue life of assembled bridges, necessitating an in-depth exploration of their fatigue performance. While existing research primarily concentrates on the transverse connection of multiple longitudinal beams, there is a notable dearth of studies on longitudinal precast segmental assembled bridges. This paper addresses this gap by establishing a fatigue benchmark finite element model for segmental assembled concrete beams, building upon existing experiments. The study employs numerical simulation to analyze the entire fatigue process, examining stress distribution, damage development, and considering the influence of reinforcement corrosion. Furthermore, a fatigue life prediction method, based on fatigue residual strength (R), is proposed for predicting the fatigue life (N) of concrete in precast segmental assembled beams. Results reveal that prestressed and ordinary reinforcements experience increasing stress with loading cycles, peaking around 100,000 cycles. Throughout fatigue loading, compressive stress in concrete remains low, preventing fatigue compression failure. However, tensile stress near joints gradually rises, initiating cracks at the mid-span beam's bottom. With continued cyclic loading, these cracks propagate towards the loading point. The upper and lower limits of fatigue life predicted by the fatigue life prediction method closely align with the compressive fatigue test values of concrete, proposed fatigue life prediction method is efficient and accurate. [ABSTRACT FROM AUTHOR]

This document is a summary of a special issue on the subject of severe plastic deformation (SPD) and bulk nanostructured materials (BNM). The special issue covers various topics related to the application, processing, and properties of SPD-processed materials. It includes review articles on advanced applications of SPD-processed materials, articles on microstructure-mechanical property relationships, diffusion and kinetics of nanocrystalline materials, deformation mechanisms, and the utilization of SPD processing for fabricating functional materials. The special issue also explores the opportunities for SPD processing in post-additive manufacturing treatment and discusses new SPD techniques and nanocrystalline structures. The document concludes by acknowledging the authors and editors involved in the special issue and expressing hope for further research and development in the field. [Extracted from the article]