Search Results (1,340)

The evaluation of interfacial bonds between polymeric cementitious composites (PCCs) and concrete is considered as a critical factor to determine structural safety, durability, and service life regarding the repair and strengthening of old concrete structures. Conventional evaluations of interfacial bond strength have primarily relied on destructive testing methods, such as the pull-off and slant shear tests. However, these methods inherently possess fundamental limitations, including localized damage, non-uniform stress distribution, and uncertainty in result interpretation. This review aims to provide a comprehensive overview of existing standards and methods for assessing interfacial bond strength. For this purpose, the evaluation methods and results for the interfacial bond strength between cementitious composites such as PCCs and concrete were systematically reviewed. It further examines the characteristics and sources of error of the representative destructive method (pull-off test), highlighting its inherent limitations. Furthermore, this study conducted an in-depth analysis of a hybrid evaluation strategy combining non-destructive testing (NDT) and artificial intelligence (AI) to overcome the limitations of conventional interfacial bond strength assessment methods and minimize prediction errors. The results demonstrated that the NDT–AI hybrid approach, based on an ANN–BFGS model, achieved the highest accuracy in bond strength prediction and was identified as the optimal method for quantitatively and non-destructively evaluating interfacial bond behavior. Full article

The rapid expansion of island and reef infrastructure has intensified the demand for sustainable concrete materials, yet the scarcity of conventional aggregates and freshwater severely constrains their supply. More critically, the fundamental bonding mechanism between steel reinforcement and coral aggregate concrete (CAC) remains poorly understood due to the highly porous, ion-rich nature of coral aggregates and the complex interfacial reactions at the steel–cement–coral interface. Moreover, the synergistic effect of polyoxymethylene (POM) fibers in modifying this interfacial behavior has not yet been systematically quantified. To fill this research gap, this study develops a C40-grade POM-fiber-reinforced CAC and investigates the composition–property relationship governing its bond performance with steel bars. A comprehensive series of pull-out tests was conducted to examine the effects of POM fiber dosage (0, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%), protective layer thickness (32, 48, and 67 mm), bar type, and anchorage length (2 d, 3 d, 5 d, and 6 d) on the interfacial bond behavior. Results reveal that a 0.6% POM fiber addition optimally enhanced the peak bond stress and restrained radial cracking, indicating a strong fiber-bridging contribution at the micro-interface. A constitutive bond–slip model incorporating the effects of fiber content and c/d ratio was established and experimentally validated. The findings elucidate the multiscale coupling mechanism among coral aggregate, POM fiber, and steel reinforcement, providing theoretical and practical guidance for the design of durable, low-carbon marine concrete structures. Full article

This paper addresses the problem where optimizing a single production shop within a production chain may not improve the overall performance of the entire chain. To overcome this and synchronize the efficiency of each shop, methods are proposed to align the output rate of an upstream shop with the limited intake rate of its downstream shop. In the proposed methods, the output rate of the upstream shop is used to guide job scheduling, processing, and resource allocation in the shop. Simulation results from a real-world case study demonstrate that implementing this pull-based system reduces job earliness and tardiness by over 90% in the tested factory, where the upstream shop is a flexible job shop, leading to lower inventory costs, idling costs, and labor costs. Full article

Accurate determination of soil and contact parameters is crucial for tillage machinery design; however, the interactions among soil, tools, and roots in citrus orchards covered with green manure remain insufficiently defined. This study, therefore, combined physical experiments with DEM simulations to characterize these interactions. Using significance analysis and response surface methodology (RSM), the effects of major factors on angle of repose (AoR) and initial slip angle (ISA) at varying soil depths were evaluated, enabling precise calibration of both external (soil–machinery) and internal (particle–particle) parameters. Subsequently, a GA-BP optimization model was constructed to enhance calibration accuracy, yielding optimal values for the soil-to-soil rolling friction coefficient (γ = 0.125–0.136), soil-to-65Mn static friction coefficient (μ′ = 0.431 − 0.540), and soil surface energy (JKR = 0.952 − 1.091 J·m⁻²). Shear tests using the bonding V2 model were conducted to calibrate the Bonding parameters of green manure stems and roots, while pull-out tests and simulations were used to validate the root–soil parameters. Direct shear tests confirmed the model’s reliability, with errors in internal friction angle and cohesion below 10%. These findings may contribute to improving DEM simulation accuracy for soil improvement under green manure coverage and support the optimization of soil tillage in citrus orchards. Full article

Background: The study evaluated the acute effect of dryland maximum strength (MS) training on water polo performance. Methods: Twelve female players (20.3 ± 1.4 years) underwent initial assessments, including a head-out 20 m swim and a one-repetition maximum (1RM) strength test in three exercises: bench press, seated pull row, and half squat. These exercises were used as the experimental (EXP) condition. During the main testing sessions, participants completed the EXP and a control (CON) condition. In the EXP, players completed MS training (three sets of six repetitions at 80% 1RM), followed 15 min later by in-water testing. In the CON, only the in-water tests were performed. These included a 10 s tethered swim to measure force, a 20 m head-out swim at maximum intensity to measure performance time, ten goal-targeted throws to reach the highest accuracy and throwing velocity, and three in-water vertical jumps as high as possible. Results: The performance time in the head-out 20 m swim (EXP: 14.21 ± 0.4, CON: 14.18 ± 0.5 s), tethered swimming force (EXP: 86.85 ± 14.82, CON: 89.58 ± 15.92 N), shooting velocity (EXP: 14.67 ± 1.19, CON: 14.91 ± 0.32 m·s⁻¹), shooting accuracy (EXP: 16.5 ± 5.4, CON: 19.0 ± 5.1 points), and in-water vertical jump height (EXP: 51.7 ± 5.6, CON: 52.9 ± 4.2 cm) were no different between conditions (p > 0.05). Conclusions: Dryland maximum strength training performed with high loads (80% 1RM) does not impair subsequent performance during sport-specific testing in female water polo players. These findings suggest that such MS training can be safely implemented 15 min prior to in-water training sessions. Full article

Background: Falls are a leading cause of injury and disability among older adults. Conventional clinical tests typically do not challenge reactive postural responses to unexpected perturbations, which limits their ability to comprehensively assess fall risk. Objective: To examine the test–retest reliability of five pragmatic, low-cost, perturbation-based tests designed to identify compensatory stepping strategies in older adults, and to explore their concurrent validity against established clinical assessments. Methods: Fifty-seven older adults (44 community-dwelling and 13 institutionalized) completed five compensatory stepping tests (obstacle crossing, forward push, backward pull, and lateral pulls to the right and left) and conventional functional tests [Timed Up and Go (TUG), 30 s Chair Stand, and the Short Physical Performance Battery (SPPB)] on two separate days, ten days apart. Cohen’s weighted kappa (Kw) quantified test–retest reliability, and Pearson’s correlation coefficients assessed relationships with conventional tests. Results: Obstacle (Kw = 0.443), forward push (Kw = 0.518), and backward pull (Kw = 0.438) demonstrated moderate agreement overall. Lateral pull tests showed poor reliability. Nevertheless, moderate correlations were observed between some perturbation tests (particularly obstacle and backward pull) and standard clinical measures, especially TUG and SPPB. Conclusions: Although reliability was limited—most notably for lateral perturbations—specific tests showed meaningful associations with validated functional assessments. Pending methodological refinements, these low-cost tools may offer useful insights for initial fall-risk screening. Full article

This study investigates the bond strength of fifteen cement-based adhesive mortars used for expanded polystyrene (EPS) in External Thermal Insulation Composite Systems (ETICS). Field surveys and contractor interviews (170 questionnaires) found that adhesive layer thicknesses in real applications typically range from 15–20 mm and frequently exceed 20 mm, in contrast to the smaller values most often recommended by guidelines and technical instructions. Laboratory testing was conducted using two approaches: the standardized pull-off procedure according to EAD 040083-00-0404 (EAD and EAD′ variants) and an in-house pull-off procedure designed to reflect practical conditions of substrate type (concrete slab, silicate block), substrate orientation (horizontal, vertical), and adhesive layer thickness (10 and 20 mm). The results showed that adhesive bond strength is strongly influenced by adhesive layer thickness, substrate type, and substrate orientation. Increasing thickness from 10 mm to 20 mm on concrete substrates typically reduced bond strength by about 65–75%, while vertical orientation lowered adhesion to about half of that obtained in horizontal placement. Silicate substrates exhibited generally lower bond strength but higher variability, occasionally with ratios above unity due to their greater porosity. In some configurations, detachment occurred already during specimen preparation, underlining the variability of performance. The combined effect of increased thickness and vertical orientation on concrete substrates reduced adhesion by about 85% compared to the 10 mm horizontal baseline, highlighting the severity of unfavorable application conditions, whereas on silicate blocks, the effect was weaker but accompanied by large variability. The findings indicate that adhesive layer thickness has a stronger impact on bond strength than orientation and that substrate properties play an important role. The study provides a comparative perspective on current and alternative testing approaches, revealing significant differences in the results. The author’s testing method makes it possible to account for, in laboratory conditions, primarily the geometric shape and orientation of samples that are close to the actual form of adhesive mortar application in real insulation installations. This allows for the assessment of the properties of mortars and substrates that were not exposed under the conditions of current testing methods. The above provides a basis for further discussion on the inclusion of realistic application conditions in the evaluation of adhesive mortars used for bonding thermal insulation in ETICS, and for the validation assessment of an additional testing method, which is currently of an experimental nature. Full article

With the development of infrastructure construction, seawater sea–sand concrete (SWSSC) is expected to solve the shortage of freshwater and river sand. Polyoxymethylene (POM) fiber, owing to its excellent corrosion resistance, provides a novel approach to enhancing the bond performance of SWSSC. This study systematic study of the bond properties of bimetallic steel bars (BSBs) in POM fiber-reinforced SWSSC and develops a predictive model. Mechanical property tests of SWSSC and pull-out tests of BSB and SWSSC were conducted with various POM fiber contents. The results showed that the optimal volume fraction of POM fibers was 0.6%. At this fraction, the compressive strength and splitting tensile strength of SWSSC were improved by 17.7% and 20.3%, respectively, compared with the group without fibers. All pull-out specimens experienced splitting failure. The bond strength increased monotonically with the increase in relative cover thickness and exhibited a trend of first increasing and then stabilizing with rising POM fiber volume fraction. In addition, a bond stress–slip prediction model between BSBs and POM fiber-reinforced SWSSC was established based on the test results, which can provide theoretical support for the numerical simulation and design of BSB-SWSSC structures. Full article

Carbon nanotubes (MWCNTs) were synthesized in situ on para-aramid fabrics (gCPO) via a low-temperature (450 °C) chemical vapor deposition (CVD) process to enhance interfacial pull-out, frictional, and fracture toughness characteristics. FESEM analysis confirmed CNT coverage on fiber surfaces, while FTIR, Raman, and XRD results indicated limited structural modification without significant polymer degradation. The CNT-functionalized fabrics exhibited a 66.19% increase in maximum pull-out force, 55.32% improvement in interlacement rupture strength, and a three-fold rise in intra-yarn shear resistance compared with control fabrics (KPO). The static and kinetic friction coefficients increased by 26.67% and 16.67%, respectively, due to CNT-induced surface roughness, enhancing inter-fiber load transfer and reducing slippage. Single-yarn pull-out tests revealed notable gains in energy dissipation and fracture toughness (up to 1769 J/m²), whereas multi-yarn pull-out performance decreased due to excessive friction surpassing filament strength. The study demonstrates that low-temperature MWCNT growth enables effective interfacial reinforcement of soft para-aramid fabrics, establishing a novel framework for meso-scale mechanical screening of flexible nano-ballistic composites. Full article

This study investigates the ballistic performance of epoxy matrix composites reinforced with raffia fabric, aiming to evaluate their potential as the second layer in multilayered armor systems (MAS), replacing conventional synthetic aramid (Kevlar™) laminates. Composite plates with different volumetric fractions of raffia fabric (10, 20, and 30%) were manufactured and integrated with a ceramic front layer (Al₂O₃/Nb₂O₅) in MAS structures, which were then subjected to ballistic impact tests using high-energy 7.62 mm caliber ammunition. The backface signature (indentation depth) measured in ballistic clay, used as a human body simulant, showed that only the 10% raffia-reinforced composite (ER10) met the National Institute of Justice (NIJ 0101.06) safety threshold of 44 mm. Higher raffia contents (20% and 30%) led to increased indentation, compromising ballistic integrity. Scanning electron microscopy (SEM) of the fractured surfaces revealed typical energy dissipation mechanisms, such as fiber rupture, fiber pull-out, and interfacial delamination. The results indicate that raffia fabric composites with 10% fiber content can serve as a cost-effective and sustainable alternative to Kevlar™ in personal armor applications, while maintaining compliance with ballistic protection standards. Full article

Objectives: This study aimed to analyze the effects of varying antagonist volume in upper-body supersets on mechanical (lifting velocity), metabolic (blood lactate), and perceptual (perceived exertion) variables. Methods: A randomized crossover study was conducted in which 14 resistance-trained men performed three strength training conditions. In the control condition (CTR), participants performed four sets of bench press with 8 repetitions at their 12-repetition maximum load, whereas in the experimental conditions, a prone bench pull was performed immediately after the bench press using 33% (SS1) or 66% (SS2) of the individual’s maximum possible repetitions. Lifting velocity, lactate concentration, and perceived exertion were measured. Repeated-measures ANOVA or Friedman test was applied to compare conditions, with Bonferroni-corrected post hoc tests and effect sizes reported. Results: Despite a progressive decrease in mean set velocity (p < 0.001) and fastest set velocity across sets (p = 0.014) in the agonist exercise (i.e., bench press), these variables did not significantly differ between conditions. The only difference observed was a lower mean set velocity during the prone bench pull in the SS2 condition compared to the SS1 condition (p = 0.011). Perceived exertion also increased across sets (p < 0.001), with no differences between protocols. Blood lactate concentration, measured before the final set, was significantly higher in SS2 compared to CTR (p = 0.003) and SS1 (p < 0.001), indicating a greater metabolic load during training. Conclusions: Agonist–antagonist supersets allow for reduced training time without negatively impacting acute mechanical performance in the agonist exercise. Low-fatigue configurations (SS1) in the secondary exercise do not significantly increase lactate levels, while moderate-fatigue configurations (SS2) in the secondary exercise increase metabolic load. Full article

Primary hip and knee arthroplasties are common surgeries in the U.S., with periprosthetic joint infection (PJI) being the leading cause of implant revision. Systemic antibiotics often fail to achieve sufficient local concentrations, driving interest in localized drug delivery. Titanium (Ti) implants modified with titania nanotubes (TNTs) provide an increased surface area for drug loading and controlled release. Previous studies have shown that gentamicin-loaded TNTs inhibit Staphylococcus aureus growth in vitro without compromising osteoblast viability. This study investigated the effect of gentamicin–chitosan (GC)-coated TNT implants in a murine model, hypothesizing a positive impact on osseointegration. Titanium alloy (Ti6Al4V) wires were anodized to form TNTs and then coated with gentamicin–chitosan (GC) via electrophoretic deposition. Implants (Bare, TNT, TNT+GC; n = 30) were inserted bilaterally into femoral canals of C57BL/6J mice. After > 1 month, osseointegration was assessed by histological point counting, scanning electron microscopy (SEM)-based areal analysis, and mechanical pull-out testing. ANOVA was used to identify differences between groups, and linear regression was applied to account for harvest time, bone contact area, and anatomical section. Bone area fraction (BAF) around the implant measured by the SEM–areal method was significantly higher around TNT+GC (18.4% ± 1.1) and TNT (16.5% ± 1.4) versus Bare (9.0% ± 2.3) (p < 0.0028) implants. The maximum fixation strength was higher for TNT (0.878 ± 0.175 N/mm²) and TNT+GC (0.853 ± 0.215N/mm²) when compared to bare implants 0.316 ± 0.082 N/mm²) (p = 0.048 and p = 0.050, respectively). No significant differences appeared between TNT and TNT+GC. These findings indicate that GC coatings on TNT implants do not impair osseointegration and may even enhance bone–implant integration. Such coatings may therefore provide dual benefits, offering antibacterial protection while improving bone fixation, making them a promising strategy for PJI prevention. Further long-term studies are needed to confirm durability and clinical translation. Full article

Fully grouted rock bolts play a vital role in stabilising underground excavations, particularly in corrosive environments where material properties, geometric configuration, and installation conditions influence their load transfer performance. Although the practical importance of fully grouted fibreglass rock bolts is well recognised, quantitative evidence on their axial load transfer mechanisms remains limited. Prior work has primarily centred on steel rock bolts, with few studies on how embedment length, grout stiffness, interface roughness and confining stress govern bond mobilisation in fully grouted fibreglass rock bolts, indicating a clear need for further scientific investigation. This study examines the axial load transfer and shear behaviour of fully grouted fibreglass rock bolts, focusing on the effects of embedment length (EL), grout properties, and boundary conditions. A comprehensive series of laboratory pull-out tests were conducted on two widely used Australian glass fibre reinforced polymer (GFRP) rock bolts, TD22 and TD25, with diameters of 22 mm and 25 mm, respectively, under varying ELs and grout curing times to evaluate their axial performance. Additionally, single shear tests and uniaxial compressive strength (UCS) tests were conducted to assess the shear behaviour of the rock bolts and the mechanical properties of the grout. The results showed that increased EL, bolt diameter, and grout curing time generally enhance axial capacity. With grout curing from day 7 to the day 28, the influence of embedment length became increasingly pronounced, as the axial peak load rose from 35 kN (TD22-50, 7 days) to 116 kN (TD22-150, 28 days) and from 39 kN (TD25-50, 7 days) to 115 kN (TD25-150, 28 days), confirming that both longer bonded lengths and extended curing significantly enhance the axial load-bearing capacity of fully grouted GFRP rock bolts. However, the TD22 rock bolts exhibited superior shear strength and ductility compared to the TD25 rock bolts. Also, a calibrated distinct element model (DEM) was developed in 3DEC to simulate axial load transfer mechanisms and validated against experimental results. Parametric studies revealed that increasing the grout stiffness from 5 e7 N/m to 5 e8 N/m increased the peak load from 45 kN to 205 kN (approximately 350%), while reducing the peak displacement, indicating a shift toward a more brittle response. Similarly, increasing the grout-bolt interface roughness boosted the peak load by 150% (from 60 kN to 150 kN) and enhanced residual stability, raising the residual load from 12 kN to 93.5 kN. In contrast, confining stress (up to 5 MPa) did not affect the 110 kN peak load but reduced the residual load by up to 60% in isotropic conditions. These quantitative findings provide critical insights into the performance of GFRP bolts and support their optimised design for underground reinforcement applications. Full article

The mechanical properties of dental implants are critical for their durability. The purpose of this study was to determine the maximum force required to induce full pull-out of a titanium implant from the bone and to characterize the mechanical behavior during this process. First, pull-out tests were performed on monolithic implants embedded in bovine ribs and foam blocks that mimic the mechanical parameters of human bone, allowing a quantitative evaluation of implant–bone interface strength and a comparison of geometric variants. Second, the extraction process was recreated in a three dimensional finite element model incorporating nonlinear interface contact and parameterization, enabling the reproduction of load–displacement curves; the results obtained showed good agreement with the experiment. Third, the fracture surfaces were observed macroscopically and by scanning electron microscopy/energy dispersive spectroscopy. The results demonstrated significant distinctions in the forces required to extract implants with varying thread geometries, clearly indicating the impact of implant design on their mechanical stability. The presented FEM-based methodology provides a reliable tool to study mechanical interactions at the implant–bone interface. The findings obtained can improve our understanding of implant behavior in biological systems and provide a basis for further optimization of their design. Full article

The most critical aspect of farm mechanization management is determining the optimal capacity, including the size and type of implements, to efficiently perform agricultural operations within the available time frames while minimizing the operating costs of farming mechanisms. In this study, 30 test reports yielded 353 data points as each test had different values of drawbar pull, forward speed and fuel consumption for Massey Ferguson tractors were obtained from the Nebraska Tractor Test Laboratory (NTTL), USA. The tractors chassis type was front wheel assist tractor. These test reports were reviewed for the period from 1997 to 2016, except for 2002. Stepwise regression was applied, and two mathematical models were derived to predict drawbar pull (kN) (R² = 0.907) and fuel consumption (lit/h) (R² = 0.911). Through a field test on an asphalt track, data were obtained on the drawbar pull, forward speed, and fuel consumption of a Massey Ferguson tractor, model 440. The values of drawbar pull and fuel consumption were compared with those from the developed mathematical models after incorporating the appropriate independent variables. The average relative error for drawbar pull was found to be approximately 21.25%, and the average relative error for fuel consumption was approximately 12.38%. Therefore, the two developed models can be used in agricultural mechanization management. Full article