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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]

Purpose: To investigate the physical and mechanical behaviors of polyether ether ketone (PEEK) before and after thermocycling, as well as its potential use as a more durable prosthetic component for implantsupported and -retained removable dental prostheses (I-RDPs). Materials and Methods: Roughness and surface hardness were evaluated in specimens obtained using the subtractive method (n = 20) with a diameter of 9 mm and a thickness of 2 mm, and retention force was measured using attachments with a diameter of 4 mm and a height of 3 mm. For fatigue resistance testing, a polyurethane matrix with two ball abutment implants (MDL, Intra-Lock International) was used to simulate the mandibular alveolar ridge. A total of 40 attachments (n = 20 pairs) were placed in acrylic resin blocks using an analog technique for the direct clinical pickup of overdenture female attachments, then submitted to 2,900 insertion/removal cycles to simulate 24 months of overdenture use. Physical analyses were performed by Fouriertransform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and differential scanning calorimetry (DSC) before and after thermocycling (5°C to 55°C for 10,000 cycles). After normal distribution was verified by Shapiro-Wilk test, one-way ANOVA was applied to analyze the surface roughness and hardness, and two-way ANOVA with Bonferroni adjustment was used to assess the retention force (a = .05). Results: Thermocycling did not change the PEEK surface roughness or hardness (P > .05). As for the retention force, the highest average was observed after the thermocycling test (P = .006). Conclusion: Based on the FTIR, XRD, and DSC results, PEEK crystallinity decreased after thermocycling, and the physical and mechanical behaviors of this polymer were compatible with the proposed application, suggesting that PEEK is a component of greater durability for I-RDPs. [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]

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]

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]

The effect of cold rotary swaging (RS) and subsequent aging on the structure, electrical conductivity, mechanical characteristics and fracture toughness of the Cu-0.77%Cr-0.86%Hf alloy was studied. RS leads to the formation of a microstructure elongated along the direction of deformation with grains width of 8.0 ± 0.2 μm. An ultrafine-grained structure with shear bands of 370 ± 10 nm in width and subgrains of 500 ± 13 nm in size is formed inside these elongated grains. The refinement of the microstructure after RS leads to an increase in ultimate tensile strength (UTS) from 300 ± 5 to 505 ± 12 MPa and a decrease in ductility from 54.0 ± 2.4 to 12.9 ± 0.3%. A subsequent aging of the alloy leads to the precipitation of fine particles of Cr and Cu5Hf phases. The precipitation of these particles leads to an additional increase in UTS of RS-treated alloy up to 558 ± 11 MPa and ductility up to 15.4 ± 2.4%. In this case, the decomposition of the supersaturated solid solution, which accompanies the particles precipitation, leads to an increase in the electrical conductivity of the deformed alloy up to 77.7 ± 1.6%IACS. The combination of RS and subsequent aging at a temperature of 450 °C for 4 h leads to an increase in the fatigue limit from 220 to 393 MPa. In addition, this treatment allows to increase the fracture toughness coefficient by 6 times. [ABSTRACT FROM AUTHOR]

Adhesive‐bonded joints in glass fiber‐reinforced polymer (GFRP) composite structures give numerous benefits, such as greater flexibility, good specific strength, improved fatigue resistance, and the ability to reduce stress concentration. Consequently, adhesive‐bonded joints are considered more influential if compared to fasteners. This research investigates the effects of incorporating graphene nanoparticles (GNPs) into the adhesive layer on several aspects of adhesively bonded co‐cure (CC) single‐lap GFRP composite joints. These aspects include shear strength, flexural strength, failure mechanisms, and fractography studies. The study examined six distinct weight percentages of GNP, specifically 0.25, 0.50, 0.75, 1.0, 1.25, and 1.5 wt.%, which are considered to enhance the interfacial strength of adhesive joints. Based on the research, 0.75 wt.% of GNP single‐lap joint (SLJ) shear strength improved by 69.40% when compared to the plain matrix SLJ. This suggests excellent load transmission between adherends. In addition, the flexural strength increased by 46.57% in the specimens containing 1.25 wt.% GNP when compared to the plain matrix used to bond in SLJ. After testing, fractured specimen microscopic images were used to examine failure mechanisms. According to fractography studies, adding GNPs to the adhesive causes surfaces to become rougher, which improves the adhesion between the adhesive and the adherends. Highlights: Six distinct wt.% of GNPs were used to prepare the matrix by sonication.Single‐lap GFRP composite joints were fabricated through a CC technique.SLJ's maximum shear strength was found at 0.75 wt% of GNP.SLJ's maximum flexural strength was found at 1.25 wt% of GNP.Failure analysis was conducted using microscopes and FESEM images. [ABSTRACT FROM AUTHOR]

High‐performance bio‐based fibers have unique advantages in biocompatibility for biomedical applications, such as sutures, hernia patches, and blood vessels. Herein, strong and tough biofibers based on regenerated silk fibroins (RSFs) are designed by a dual‐crosslinking strategy and prepared continuously in situ via a single‐channel microfluidic device. During the wet spinning process, covalent bonds between tyrosines are introduced by photo crosslinking and coordination interactions of Zn2+ ions with serines are built between RSFs, forming a dual‐crosslinked, and inter‐connected network and effectively improving the mechanical performances of RSF fibers. By optimizing the wet spinning parameters and applying an optimal post‐stretching treatment, dual‐crosslinked RSF fibers exhibit an excellent tensile strength of 891 MPa, a remarkable Young's modulus of 15.0 GPa, a large tensile strain of 20.1%, and an outstanding toughness of 114 MJ m−3, which are superior to other regenerated biofibers. In addition to the outstanding mechanical performances, dual‐crosslinked RSF fibers also possess excellent temperature adaptability, fatigue resistance, biocompatibility, and biodegradability, making them ideal candidates for biomedical applications. In vivo tests of dual‐crosslinked RSF fibers as sutures demonstrate a good wound healing performance with smaller scar and lower inflammation. [ABSTRACT FROM AUTHOR]

In the last few decades, the advancements made in material characterisation equipment and physics-based multiscale material modeling have generated vast database in the field of Material Science and Engineering. This has inspired material innovators to attempt predicting mechanical properties of synthesised materials using big-data so as to reduce the cost, time and effort for materials innovation. However, the impact of collinerarity has always been a matter of concern in emperical research, specially in such predictions of mechanical properties. In the present work, we revisit NIMS database for steel and study the effect of multicollinearity on regression based models for predicting fatigue strength for the material. We use an iterative scheme to isolate highly correlated parameters contributing in determination of the fatigue strength of the steel. We then construct a regression model using only the non-correlated parameters to make the model more efficient computationally. Our results show that the regression model built after consideration of multicollinearity of the variables provide better performance in comparison with regression model built without consideration of the same. [ABSTRACT FROM AUTHOR]

The present study investigates the effect of adding waste glass powder (WGP) along with titanium carbide (TiC) as reinforcement on the microstructure, wettability, mechanical, and tribological behavior of AZ91D magnesium-based alloy. The addition of 3 wt.% WGP and 6 wt.% TiC resulted in a refined microstructure, with the formation of good interfacial bond and a decrease in the porosity of the alloy. The wettability of the alloy was improved with the addition of reinforcements. The mechanical properties of the modified AZ91D alloy were enhanced significantly, with an increase in the hardness (51.66% improvement), fatigue strength (59.19% improvement) and ultimate tensile strength (11.9% improvement). The wear resistance of the alloy was observed to increase with the addition of WGP and TiC, owing to the formation of a protective layer on the surface of the alloy. The results suggest that the addition of WGP and TiC can improve the overall properties of AZ91D magnesium-based alloys, making them suitable for various industrial applications. Wear results showed that the resistance against wear rate of the developed composite significantly improved after the addition of the mixture of 3% Waste glass powder + 6% TiC. [ABSTRACT FROM AUTHOR]

Thick-walled cylinders are specially used in various high-tech industries to withstand internal pressure. The presence of the compressive residual stresses in the wall of these vessels increases the bursting pressure and their fatigue life. The processes of autofrettage and radial interference in multilayer cylinders are among the conventional methods of creating compressive residual stresses. To achieve higher strength and fatigue life, the combination of these processes is also used. This research studies the bursting pressure of a double-layered cylinder with a semi-elliptical planar crack on the inner surface of the inner layer. These layers have some interference, and the inner layer is autofrettaged. Effects of various parameters as autofrettage percent, radial interference, depth, angle, and geometry of the crack are investigated on the J-integral distribution and bursting pressure. The inner and outer layers were made of AA 7075-T6 alloy. The periodic nonlinear hardening behavior of this alloy has been estimated using the Chaboche model. The validity of the results has been checked and acceptable accuracy of the numerical results proved by experimental data. [ABSTRACT FROM AUTHOR]

Synthetic biomaterials play a crucial role in developing tissue-engineered heart valves (TEHVs) due to their versatile mechanical properties. Achieving the right balance between mechanical strength and manufacturability is essential. Thermoplastic polyurethanes (TPUs) and elastomers (TPEs) garner significant attention for TEHV applications due to their notable stability, fatigue resistance, and customizable properties such as shear strength and elasticity. This study explores the additive manufacturing technique of selective laser sintering (SLS) for TPUs and TPEs to optimize process parameters to balance flexibility and strength, mimicking aortic valve tissue properties. Additionally, it aims to assess the feasibility of printing aortic valve models with submillimeter membranes. The results demonstrate that the SLS-TPU/TPE technique can produce micrometric valve structures with soft shape memory properties, resembling aortic tissue in strength, flexibility, and fineness. These models show promise for surgical training and manipulation, display intriguing echogenicity properties, and can potentially be personalized to shape biocompatible valve substitutes. [ABSTRACT FROM AUTHOR]

Shielding gas, metal vapors, and gases trapped inside powders during atomization can result in gas porosity, which is known to degrade the fatigue strength and tensile properties of components made by laser powder bed fusion additive manufacturing. Post-processing and trial-and-error adjustment of processing conditions to reduce porosity are time-consuming and expensive. Here, we combined mechanistic modeling and experimental data analysis and proposed an easy-to-use, verifiable, dimensionless gas porosity index to mitigate pore formation. The results from the mechanistic model were rigorously tested against independent experimental data. It was found that the index can accurately predict the occurrence of porosity for commonly used alloys, including stainless steel 316, Ti-6Al-4V, Inconel 718, and AlSi10Mg, with an accuracy of 92%. In addition, experimental data showed that the amount of pores increased at a higher value of the index. Among the four alloys, AlSi10Mg was found to be the most susceptible to gas porosity, for which the value of the gas porosity index can be 5 to 10 times higher than those for the other alloys. Based on the results, a gas porosity map was constructed that can be used in practice for selecting appropriate sets of process variables to mitigate gas porosity without the need for empirical testing. [ABSTRACT FROM AUTHOR]

Within the scope of this research, patterns of changes in the fatigue life and limit of metals under cyclic stress were identified and the most informative parameters were determined as the basis for developing a method for the universal transformation of experimental data on the fatigue of metals and alloys for their subsequent generalization. Experimental data on metal fatigue, obtained by a large number of authors for a wide range of grades of steels and alloys, under the influence of various combinations of factors, were systematized. A generalized dependence of the recalculated parameters of fatigue life and limit was obtained, its characteristics were assessed, and a sensitivity analysis was performed, confirming the universal nature of the obtained dependence. A system of parameters has been proposed making it possible to consider and forecast high-cycle fatigue processes for a wide range of metals and alloys, under the conditions of various combinations of operating factors, from unified positions and a more general point of view. [ABSTRACT FROM AUTHOR]

Surface residual stresses in welded specimens significantly influence properties such as fatigue resistance, fracture toughness, and the superplasticity of joints. In this study, we employed friction stir welding, a well-established joining method, to weld dissimilar titanium alloys. By combining two distinct titanium alloys, we aimed to harness their unique properties when subjected to cyclic loading, impact, or superplastic forming processes. Utilizing X-ray diffraction, macroscopic surface stresses were assessed in dissimilar titanium alloys (Ti-6242 standard grain (SG) and Ti-54M) welded via friction stir welding, assuming a linear lattice distortion. The study accounted for misalignment, significant distortion, and grain refinement in the stir zone. Macroscopic surface residual stresses were quantified on the weld surface and at a depth of 1.5 mm beneath it within a square cross-section (1 × 1 mm2) by oscillating the specimen in the (X-Y) direction. The sin2φ method, implemented through the LEPTOS® (v7.8) software, was employed for residual stress measurement. The analysis of the results was conducted with respect to different rotation and traverse speeds. It was noted that at the center (CEN) of the weld, commonly referred to as the weld nugget, approximately 50 MPa of tensile stress was observed under the lowest values of both tool rotation speed and traverse speed. Tensile residual stresses were evident at the boundaries and within the stir zone. No discernible pattern was observed at the specified locations. Notably, the resultant values of residual stress, influenced by rotation and traverse speeds, exhibited asymmetry. [ABSTRACT FROM AUTHOR]

This paper presents a rolling contact fatigue life prediction model for bearing steel. In the initial stage of rolling contact, the gradient structure appears in the subsurface region of bearing steel and the hardness shows a gradient distribution along the contact depth direction due to the roller compaction effect. This indicates that the fatigue resistance of bearing steel varies in the subsurface region. Besides, each subsurface material volume element is subject to different stress cycles. Based on Weibull theory, the survival possibility of subsurface volume elements is formulated. Then the rolling contact fatigue life is evaluated considering the stress state and anti-fatigue performance of each elementary volume of the subsurface material. According to the phenomenon and assumption, the model proposed for gradient material was applied in the rolling contact fatigue life prediction of the bearing steel GCr15 and validated with the fatigue experiment data in the open literature. Furthermore, the accuracy of the proposed model results was compared with the traditional empirical rolling contact fatigue life prediction models. [ABSTRACT FROM AUTHOR]

Objective: Surgical treatment with internal fixation, specifically percutaneous fixation with three cannulated compression screws (CCSs), is the preferred choice for young and middle‐aged patients. The mechanical advantage of the optimal spatial configuration with three screws provides maximum dispersion and cortical support. We suspect that the spatial proportion of the oblique triangle configuration (OTC) in the cross‐section of the femoral neck isthmus (FNI) may significantly improve shear and fatigue resistance of the fixed structure, thereby stabilizing the internal fixation system in femoral neck fracture (FNF). This study aims to explore the mechanical features of OTC and provide a mechanical basis for its clinical application. Methods: Twenty Sawbone femurs were prepared as Pauwels type III FNF models and divided equally into two fixation groups: OTC and inverted equilateral triangle configuration (IETC). Three 7.3 mm diameter cannulated compression screws (CCSs) were used for fixation. The specimens of FNF after screw internal fixation were subjected to static loading and cyclic loading tests, respectively, with five specimens for each test. Axial stiffness, 5 mm failure load, ultimate load, shear displacement, and frontal rotational angle of two fragments were evaluated. In the cyclic loading test, the load sizes were 700 N, 1400 N, and 2100 N, respectively, and the fracture end displacement was recorded. Results were presented as means ± SD. Data with normal distributions were compared by the Student's t test. Results: In the static loading test, the axial stiffness, ultimate load, shear displacement, and frontal rotational angle of two fragments were (738.64 vs. 620.74) N/mm, (2957.61 vs. 2643.06) N, (4.67 vs. 5.39) mm, and (4.01 vs. 5.52)° (p < 0.05), respectively. Comparison between the femoral head displacement after 10,000 cycles of 700N cyclic loading and total displacement after 20,000 cycles of 700–1400N cyclic loading showed the OTC group was less than the IETC group (p < 0.05). A comparison of femoral head displacement after 10,000 cycles of 1400N and 2100N cycles and total displacement after 30,000 cycles of 700–2100N cycles showed the OTC group was less than another group, but the difference was not significant (p > 0.05). Conclusion: When three CCSs are inserted in parallel to fix FNF, the OTC of three screws has obvious biomechanical advantages, especially in shear resistance and early postoperative weight‐bearing, which provides a mechanical basis for clinical selection of ideal spatial configuration for unstable FNF. [ABSTRACT FROM AUTHOR]

The article discusses a research project called "nodularWELD" that investigates the fatigue behavior of welded thick-walled nodular cast iron components used in heavy industry and wind energy turbines. The study examines the effects of local material defects on the lifetime of these components and explores the possibility of repair welding. The research project examines different welding fillers and conducts fatigue tests to assess the usability of repair-welded nodular cast iron. The findings show a reduction in fatigue strength for all materials in the welded condition, with the highest loss observed for EN-GJS-450-18. The research suggests that welding for repair purposes may not be feasible for certain applications. The document also includes a list of nomenclature, references, and acknowledgments to the funding source and project partners. [Extracted from the article]

This document is a compilation of various research papers and articles that discuss the use of machine learning and other techniques to predict fatigue lifetimes in different materials and structures. The papers cover topics such as the use of neural networks, XGBoost, and physics-informed machine learning models for fatigue prediction. The research focuses on different materials, including aluminum alloys and lead-free solders, and explores the effects of factors such as wear, lubrication, corrosion, and stress on fatigue life. The papers provide insights into the application of machine learning techniques in predicting fatigue lifetime and offer potential solutions for improving the accuracy of these predictions. [Extracted from the article]

This article presents the findings of a study on the ultrasonic fatigue testing of AISI 304 and 316 stainless steels. The researchers conducted experiments to evaluate the fatigue properties of the stainless steels under different cooling conditions. The results showed that the thermal effect had a significant impact on specimen fracture at higher loads and temperatures, but reducing the load mitigated this effect. The study also found that stainless steel 316 had higher resistance to ultrasonic fatigue compared to stainless steel 304, and the type of immersion fluid used affected the corrosion wear on the surface of the specimens. The article emphasizes the importance of surface finish in improving the fatigue life of the material. Overall, the study provides valuable insights into the behavior and performance of stainless steel in various industrial applications. [Extracted from the article]

Inconel 718 (IN 718) belongs to the category of nickel-based superalloys with outstanding mechanical characteristics such as high strength, better corrosion resistance, greater hardness, fatigue and wear resistance. This alloy is mostly implemented in manufacturing the components of aeroengines, nuclear reactors, space shuttles, pressurized boilers and so on. In most cases, the parts made from this alloy work in severe aggressive environments. A prolonged exposure of this alloy in such environments will pave the way for corrosion phenomenon which will minimize the service life of the components. It is reported that the parts made via additive manufacturing will exhibit better mechanical characteristics than the casted and forged parts. This work is aimed to investigate the anti-corrosion characteristics of both as-cast and LPBF printed IN 718 samples at various time intervals in the seawater environment. By means of FESEM micrographs, the microstructural evolution in both as-cast and LPBF printed IN 718 samples was analyzed. The anti-corrosion characteristics of both samples were investigated in the environment containing 3.5 wt.% NaCl (seawater) in terms of EIS and potentiodynamic polarization curves along with the corroded morphology. The results showed that the LPBF printed IN 718 samples exhibit fine cellular and columnar grains decorated with the NbC precipitates along their boundaries, whereas the casted samples have larger and coarser grains with uneven segregation of NbC precipitates. From the Tafel and EIS (Nyquist and Bode) plots, the LPBF IN 718 sample showed greater corrosion resistance in terms of current density and polarization resistance values. In particular, the 15 h LPBF sample has a strong, compact passive film formed on it. This compact passive film paved the way for this sample to exhibit lower current density (3.03 × 10 − 7 A/cm2) and higher polarization resistance (3678 Ω · cm2) when compared with the LPBF and cast samples at other intervals. [ABSTRACT FROM AUTHOR]

Natural rubber (NR) is widely used in various fields including aerospace, military industry and transportation due to its superior elasticity and comprehensive mechanical properties. Nonetheless, the commercial NR prepared by different methods usually exhibits different mechanical properties, primarily due to variations in processing conditions during the conversion from latex to bulk rubber material. Consequently, this poses challenges in scientific research and industrial production of NR. In order to assess the properties of various commercially available NR and identify key structural and compositional components, this study systematically compares and analyzes four representative NR raw materials: air dried sheet (ADS), ribbed smoked sheets (RSS), constant viscidity NR (CV), and whole field latex rubber (WF). The investigation focuses on evaluating their static mechanical behavior, SIC behavior, wear resistance, and fatigue resistance. The findings indicate that protein and gel content exhibit a crucial influence on the NR properties. These constituents contribute to the formation of a high-crosslinking density region, generating a heterogeneous network structure within the rubber. This structure amplifies strains during deformation, leading to earlier and stronger strain-induced crystallization (SIC). Among the four commercial NR brands, RSS demonstrates superior overall mechanical and dynamic properties owing to its high protein and gel content. This study serves as a valuable reference for comprehending the differences in properties among various commercial NR, thereby offering guidance for the actual processing and selection of NR. [ABSTRACT FROM AUTHOR]

High cycle fatigue (HCF) behavior of Ni superalloy 617M is investigated at 973 K and R‐ratio −1 on a resonance‐based fatigue testing system at 85 Hz frequency. The alloy experiences an abrupt drop in fatigue life within a narrow domain of 2.5–5 MPa near its fatigue strength at 320 MPa. Electron microscopy and diffraction techniques were employed to thoroughly analyze the nominal fatigue damage. The characterization revealed the significance of precipitation of secondary phases M23C6, Ti (C, N), and γ′ phase in dictating the HCF strength of the alloy. Cyclic loading at high temperature causes γ‐matrix hardening and secondary phase precipitation synergistically strengthening the material beyond its yield strength. Conjunctively, dynamic strain aging was also seen to play a major role in the evolution of fatigue damage. The work highlights the collective contribution of γ′‐phase precipitation, carbides, and dynamic strain aging and their influence on the HCF behavior of alloy 617M. Highlights: Response of alloy 617M under high cycle fatigue load is studied at high temperature.Near fatigue limit, sharp drop in fatigue life causes nominal microstructural damage.Precipitation of phases γ′ and carbides in matrix, DSA, and cyclic hardening strengthens alloy.Precipitates at the grain and twin boundaries weakened the fatigue resistance of alloy. [ABSTRACT FROM AUTHOR]

Engineering materials commonly suffer from cumulative and irreversible damage during cyclic deformation, leading to fatigue failure. Developing materials with better fatigue resistance is imperative. This work reports a metallic glass network nanomaterial that possesses superior strain‐hardening ability. After a certain number of fatigue tests, the peak stress of the nanomaterial can even be up to four times its original value. This superior strain‐hardening ability originates from the unique plastic mechanism. During cyclic deformation, localized shear transformation zones form and develop, especially in the stress concentration regions. Ligaments crosslinked to these regions cannot sustain their original configurations and contract toward these plastic hinges, resulting in the collapse and coalescence of voids. This densification enhances the engineering stress during each cycle. The fatigue features can be altered by adjusting the cyclic frequency. Stronger strain‐hardening ability can be achieved at lower cyclic frequencies. Highlights: Fatigue responses of nanoporous metallic glass (NPMG) are revealed.The NPMG exhibits superior strain‐hardening ability and remarkable densification.This strain‐hardening behavior is caused by plastic deformation.The fatigue responses of NPMG can be tuned by tailing the cyclic frequency and strain. [ABSTRACT FROM AUTHOR]

The sliding door with the retractable handrail examined in this study can be installed in hospitals and nursing facilities for helping the elderly and disabled to walk independently. This provides the prospect of restoring their declining walking abilities. In this study, wood is not used as building construction, which is common usage, but as mechanical structure. Though the strength evaluation is required, there is no clear standard for the fatigue strength of wood. Hence, this study shows the method of calculating the yield strength and fatigue limit of wood by investigating the methods of calculating allowable stresses in ASTM and AIJ, which are intended to be used for building construction. Using the result, the maximum tensile stress σ max T and the maximum compressive strength σ max C on the installation part of the handrail bar mounting plate where the risk is the highest are obtained by the finite element method (FEM). It is shown to be safe for the static strength and fatigue strength above. [ABSTRACT FROM AUTHOR]

Steel fibers in ultra-high performance concrete (UHPC) have been demonstrated to improve resistance to crack growth, decrease deflection, and increase fatigue life under cyclic loads. Using steel fibers as shear reinforcements, this paper investigates its effect on the postcracking shear fatigue behavior of nonstirrup UHPC beams. The study involved five UHPC beams comprising two static and three fatigue specimens to test the effects of the upper fatigue load, steel-fiber ratio, and stirrup ratio on the shear fatigue response. The test results showed that increasing the initial crack width in the nonstirrup UHPC beam from 0.05 to 0.2 mm (the equivalent of doubling the upper fatigue load) decreased the fatigue life from over two million to 24,875 cycles. The use of steel fibers in place of stirrups increased the residual-to-static strength and residual-to-initial stiffness ratios by 5% and 16%, respectively, after two million cycles. Compared with the specimen with stirrups, the steel-fiber-reinforced specimen had a lower midspan fatigue deflection-to-ultimate static deflection ratio owing to the relieved fatigue strain localization and increased tensile steel reinforcement-UHPC bond fatigue strength. The current codes predict the shear fatigue strength conservatively. A calculation model for accurately predicting fatigue deflection was proposed and compared with the existing test results. A future study on the wider parametric analysis and large-scale beam tests on the fatigue performance of these beams should be conducted. [ABSTRACT FROM AUTHOR]

Q370qENH weathering steel is widely used in railway steel bridge construction in China. However, limited research has been conducted on the high-cycle fatigue damage of the welds in weathering steel railway bridges. In this study, we conducted experimental tests to investigate the high-cycle fatigue performance of the heat-affected zone (HAZ) of Q370qENH weathering steel. First, coarse-grain heat-affected zone (CGHAZ) specimens and fine-grain heat-affected zone (FGHAZ) specimens of Q370qENH were obtained using the welding thermal simulation (WTS) method. The accuracy of the WTS method was verified through metallographic structure analysis. Subsequently, high-cycle fatigue tests were conducted on the base material and HAZ specimens. Then, probabilistic stress-life (P-S-N) curves and the fatigue strength of the Q370qENH HAZ were obtained. Finally, the fatigue extension mechanism of the Q370qENH HAZ was examined. The results indicate that the WTS method effectively produced HAZ specimens matching the welded joint. The fatigue life of the FGHAZ and CGHAZ specimens was significantly lower than that of the Q370qENH base material. The fatigue strength of HAZ was approximately 80% of that of the base material, and the fatigue strength reference of the Q370qENH HAZ was 175 MPa. Furthermore, the CGHAZ specimens were more prone to slip and had a high stress concentration at the microscopic scale, leading to their inferior fatigue performance. This study provides a valuable reference for the design and fatigue assessment of weathering steel bridges. [ABSTRACT FROM AUTHOR]

Ferroelectricity-based storage technology is anticipated to achieve nonvolatile, low-power, and high-density storage in integrated field circuits. Here, the phenomena of electrically reversible switching of nanocracks in the tellurium film/ferroelectric PMN-PT heterojunctions are discussed. Upon the application of external electric fields (±2 kV/cm), the nonvolatile resistance on-off ratio reached over 106 at room temperature. This was achieved through the opening and closing of cracks in the Te film caused by the electric-field-driven flipping of 109° ferroelectric domains in a ferroelectric single crystal. In addition, the ON/OFF resistance states remain stable even after more than 103 cycles and the retention time exceeds 6 h, demonstrating excellent fatigue resistance performance of the device. This work renders a window to design nonvolatile memory by constructing electric-field tunable nanocracks in a semiconductor film/ferroelectrics heterojunction system. [ABSTRACT FROM AUTHOR]

Artificial electronic skin (E‐skin), a class of promising materials mimicking the physical‐chemical and sensory performance of the human skin, has gained extensive interest in the field of human health‐monitoring and robotic skins. However, developing E‐skin simultaneously achieving high resilience, hysteresis‐free, and absent external power is always a formidable challenge. Herein, a liquid‐free eutectic gel‐based self‐powered E‐skin with high resilience, fatigue resistance, and conductivity is prepared by introducing hydroxypropyl cellulose (HPC) into metal salt‐based deep eutectic solvents (MDES). The unique structural design of cellulose‐anchored permanent entangled poly(acrylic acid) (PAA) chain, in combination with rapid broken/reconstruction of the dense dynamic sacrificial bonds, realizes the fabrication of high‐elastic E‐skin with negligible hysteresis. This further demonstrates the promising practical application of the cellulose‐based eutectogel with high transmittance (92%), high conductivity (36.6 mS m−1), and high resilience (98.1%), and excellent environment stability in robust triboelectric nanogenerator for energy harvesting and high resilience, self‐powered E‐skin for human health‐caring and human‐machine interaction. [ABSTRACT FROM AUTHOR]

With the gradual promotion of new energy technologies, there is a growing demand for capacitors with high energy storage density, high operating temperature, high operating voltage, and good temperature stability. In recent years, researchers have been devoted to improving the energy storage properties of lead‐based, titanium‐based, and iron‐based multilayer ceramic capacitors (MLCCs). However, limited research has been conducted into MLCC development using NaNbO3 (NN)‐based materials. In this paper, the successful achievement of excellent overall energy storage performance in a novel NaNbO3–(Bi0.5Na0.5)TiO3–Bi(Mg0.5Hf0.5)O3 lead‐free MLCCs is presented. The disordered tilting around the cp axis, disrupts Na and Bi ions' long‐range displacements and induces PNRs and strong relaxor behavior, which ensures a superior energy storage performance, together with the multilayer ceramic design strategy. As a result, the NN‐based MLCC device presents an ultra‐high Wrec = 12.65 J cm−3 and η = 88.5%, simultaneously showing superior temperature stability (Wrec varies <±1% and η varies <±6% from −50 to 125 °C) and fatigue resistance (Wrec and η vary <±1% over 107 cycles). This study highlights the advanced energy storage potential of NaNbO3‐based MLCCs for various applications, and ushers in a new era for designing high‐performance lead‐free capacitors that can operate in harsh environments. [ABSTRACT FROM AUTHOR]

Cement, as a construction material, has low thermal resistance, inherent fire resistance, and is incombustible up to a certain degree. However, the loss of its mechanical performance and spalling are its primary issues, and it thus cannot retain its performance in refractory applications. The present study explores the performance of geopolymer formulations that have excellent fire resistance properties for potential refractory applications. This study is unique, as it investigates advanced solid geopolymer formulations that need only water to activate and bind. Various solid geopolymer formulations with fly ash as a precursor; potassium hydroxide and potassium silicate as activators; and mullite and alumina as refractory aggregates were studied for their compressive strength at up to 1100 °C and compared with their two-part conventional liquid alkaline geopolymer counterparts. Advanced solid geopolymer formulations with mullite and alumina as refractory aggregates had mechanical strength values of 84 MPa and 64 MPa post-1100 °C exposure and were further exposed to ten thermal cycles of 1100 °C to study their fatigue resistance and post-exposure compressive strengths. The geopolymer sample with mullite as a refractory aggregate yielded 115.2 MPa compressive strength after the fourth cycle of exposure. This sample was also studied for its temperature distribution upon direct flame exposure. All the geopolymer formulations displayed a drop in compressive strength at 600 °C due to viscous sintering and then a rise in strength at 1100 °C due to phase transformation. X-ray diffraction studies revealed that the formation of crystalline phases such as leucite, sanidine, and annite were responsible for the superior strengths at 1100 °C for the alumina- and mullite-based geopolymer formulations. [ABSTRACT FROM AUTHOR]

In order to examine the mechanical properties and rotational bending fatigue performance of 40CrNi2MoE steel subsequent to tempering at varying temperatures, the steel specimen was subjected to tempering within the range of 400~460 °C. SEM, EBSD, and TEM were used to analyze the microstructure as well as precipitates. The strain hardening law was studied using the modified Crussard–Jaoult method. Investigations were undertaken to reveal the rotational bending fatigue life with respect to the tempering temperature. The findings indicate that the strength and fatigue life of the examined steels exhibit a decline as the tempering temperature increases, with the primary factor affecting this trend being the alteration in dislocation density. No notable impact on the fatigue fracture morphology exerted by tempering temperature was found within the range of the experiment. The C–J model analysis reveals that the work-hardening behavior of the trial steels is influenced by dislocations and the second phase. [ABSTRACT FROM AUTHOR]

Solid-state refrigeration based on elastocaloric materials (eCMs) requires reversibility and repeatability. However, the intrinsic intergranular brittleness of ferromagnetic shape memory alloys (FMSMAs) limits fatigue life and, thus, is the crucial bottleneck for its industrial applications. Significant cyclic stability of elastocaloric effects (eCE) via 53% porosity in Ni-Fe-Ga FMSMA has already been proven. Here, Ni-Fe-Ga foams (single-/hierarchical pores) with high porosity of 64% and 73% via tailoring the material's architecture to optimize the eCE performances are studied. A completely reversible superelastic behavior at room temperature (297 K) is demonstrated in high porosity (64–73%) Ni-Fe-Ga foams with small stress hysteresis, which is greatly conducive to durable fatigue life. Consequentially, hierarchical pore foam with 64% porosity exhibits a maximum reversible ∆Tad of 2.0 K at much lower stress of 45 MPa with a large COPmat of 34. Moreover, it shows stable elastocaloric behavior (ΔTad = 2.0 K) over >300 superelastic cycles with no significant deterioration. The enhanced eCE cyclability can be attributed to the pore hierarchies, which remarkably reduce the grain boundary constraints and/or limit the propagation of cracks to induce multiple stress-induced martensitic transformations (MTs). Therefore, this work paves the way for designing durable fatigue life FMSMAs as promising eCMs by manipulating the material architectures. [ABSTRACT FROM AUTHOR]

To enhance the performance of ultra-high voltage power fittings in severe weather conditions without altering their current structure, the high-strength and toughness aluminum alloys were rationally selected to study the optimization of the die-casting process. This approach aims to improve the overall longevity and function of the power fittings in extreme climates. First of all, the propose of this study is to use the material's strength–toughness product (STP) concept to evaluate the material stability of the power fitting impact resistance and fatigue toughness in order to determine the appropriate material selection. Secondly, the location of the mold's sprue and gate was optimized through finite element simulation to prevent gas volume and flow defects during the casting process. This improves the material's toughness and anti-fatigue failure characteristics of the product. Then, vacuum equipment and a vacuum valve auxiliary system were added based on the existing die-casting machine, and the mold structure was optimized to enable the vacuum die-casting process. Finally, a water-based boron nitride environmentally friendly mold release agent was used to solve demolding difficulties with an A356 aluminum alloy and improve mold lubrication and surface quality. The production of quad-bundled spacers using A356 and vacuum die casting has resulted in parts with a tensile strength of at least 250 MPa and an elongation of no less than 7%. This improvement has laid a foundation for enhancing the operational reliability of existing overhead transmission line fittings. [ABSTRACT FROM AUTHOR]

Background: Scientific literature lacks strong support for using narrow diameter implants (NDI) in high masticatory force areas, especially in molars. Implant splinting in cases of multiple missing teeth reduces lateral forces, improves force distribution, and minimizes stress on implants. However, no studies have evaluated the fatigue load resistance of unitary or splinted implants. Methods: This in vitro study compares five groups of new metal alloy implants, including unitary and splinted implants with varying diameters. Mechanical characterization was assessed using a BIONIX 370 testing machine (MTS, Minneapolis, MN, USA) according to ISO 14801. For each of the five study sample groups, (n = 5) specimens underwent monotonic uniaxial compression at break testing and (n = 15) cyclic loading to determine the maximum force (Fmax) and the fatigue life (LF) values. Scanning electron microscopy (SEM) was employed for the fractographic analysis of the fractured samples. Results: The Fmax values for unitary samples ranged from 196 N to 246 N, whereas the two-splinted samples displayed significantly higher values, ranging from 2439 N to 3796 N. Similarly, the LF values for unitary samples ranged from 118 N to 230 N, while the two-splinted samples exhibited notably higher values, ranging from 488 N to 759 N. Conclusions: The observed resistance difference between sample groups in terms of Fmax and LF may be due to variations in effective cross-sectional area, determined by implant diameter and number. Additionally, this disparity may indicate a potential stiffening effect resulting from the splinting process. These findings have significant implications for dental clinical practice, suggesting the potential use of splinted sets of small-sized NDI as replacements for posterior dentition (premolars and molars) in cases of alveolar bone ridge deficiencies. [ABSTRACT FROM AUTHOR]