Search Results (245)

The development of halogen-free flame-retardant formulations for wood-based panels is a promising strategy to improve both fire safety and environmental performance. In this study, oriented strand boards (OSB) were impregnated with aqueous solutions of sodium borate (SBo) and sodium bicarbonate (SBi) to evaluate their combined effects on fire resistance and mechanical properties. Fire performance was assessed using the ASTM D3806 small-scale tunnel test, while mechanical and physical properties were measured according to ASTM D1037. Significant improvements in fire performance were observed: mass loss (ML) during flammability testing decreased by 38% (from 6.9% to 4.3%), flame spread speed (FSS) was reduced by more than 50% (from 6.8 to 3.3 mm/s), and after-flame times (AFT) dropped from 17.2 s to 0 s. Thermogravimetric analysis (TGA) further confirmed enhanced thermal stability, with increased char residue (from 16.9% in untreated boards to 31.5% in treated ones). Mechanical testing revealed a 16% increase in internal bond (IB) strength (from 0.44 to 0.51 MPa), while modulus of rupture (MOR) and modulus of elasticity (MOE) were only slightly affected (decreased by up to 4.2% and 3.6%, respectively). Interestingly, the two additives exerted contrasting effects: SBo reduced strength and bonding performance, whereas SBi improved internal bond strength and dimensional stability. The optimal balance was obtained with treatment P250-50 (250 g SBi and 50 g SBo), which combined enhanced fire resistance with acceptable mechanical integrity. Overall, the results demonstrate that the synergistic use of SBo and SBi offers an effective halogen-free approach to simultaneously enhance the fire resistance and mechanical performance of OSB panels, highlighting its potential for industrial applications. Full article

This study evaluates the cosmetic degradation of polyethylene (PE) and polypropylene (PP) automotive components under four exposure scenarios—no exposure, outdoor exposure with and without glass shielding, and accelerated UV chamber weathering (ASTM G154)—through the evolution of visible (VIS) reflectance. Thirty-two samples (16 PE, 16 PP) were monitored over five time points; surface reflectance was recorded at 21 wavelengths and summarized into seven VIS bands, and hardness (Shore D) was measured pre/post-exposure. Repeated-measures univariate and multivariate analyses consistently revealed significant effects of Condition, Time, and their interaction on reflectance, with initial-reflectance adjustment improving inference stability across bands. PE exhibited more gradual and coherent reflectance decay, whereas PP showed greater band-to-band variability—most notably under UV chamber exposure. Additionally, hardness decreased in most exposed groups, aligning with optical changes. To place spectral trajectories in a kinetic context, a family of exponential models with small-sample information criterion selection was fitted, yielding $\eta \left(t\right)$—a dimensionless degradation efficiency summarizing spectral change. The contribution of this work is a multi-statistical framework—combining VIS-band-aware summaries with covariate-adjusted univariate/multivariate testing—that supports comparisons across materials and exposure conditions, underscoring the practical value of UV chamber protocols as surrogates for outdoor weathering. In sum, the study demonstrates the effectiveness of multivariate and covariate-adjusted models in quantifying optical degradation of polyolefins, offering pragmatic guidance for assessing mid- to long-term performance in automotive applications. Full article

This study presents a newly developed program that seamlessly converts G-code into formats compatible with Abaqus, enabling precise finite element simulations for FDM 3D printing. The tool operates on a two-pronged framework: a mathematical model incorporating key print parameters (layer thickness, extrusion temperature, print speed, and raster width) and a shape generator managing geometric parameters (fill density, pattern, and raster orientation). Initially, a predefined virtual section, based on predetermined dimensions, enhanced the correlation between experimental results and simulations. Subsequently, a corrected virtual section, derived from the mathematical model using the Box–Behnken methodology, improves accuracy, achieving a virtual thickness error of 1.06% and a width error of 8%. The model is validated through tensile testing of ASTM D638 specimens at 0°, 45°, and 90° orientations, using adaptive C3D4 mesh elements (0.35–0.6 mm). Results demonstrate that the corrected cross-section significantly improved simulation accuracy, reaching correlations above 95% in the elastic zone and 90% in the elastoplastic zone across all orientations. By optimizing the workflow from design to manufacturing, this program offers substantial benefits for the aerospace, medical, and automotive sectors, enhancing both the efficiency of the printing process and the reliability of simulations. Full article

Self-fluxing Ni-based coatings (NiCrFeBSiC) were deposited through gas-flame spraying and evaluated in three conditions: as-sprayed, flame-remelted, and furnace-heat-treated (1025 °C/5 min). Phase analysis (XRD) revealed FeNi₃ together with strengthening carbides/borides (e.g., Cr₇C₃, Fe₂₃(C,B)₆); post-treatments increased lattice order. Cross-sectional image analysis showed progressive densification (thickness ~805 → 625 → 597 µm) and a drop in porosity from 7.866% to 3.024% to 1.767%. Surface roughness decreased from Ra = 31.860 to 14.915 to 13.388 µm. Near-surface microhardness rose from 528.7 ± 2.3 to 771.6 ± 4.6 to 922.4 ± 5.7 HV, while adhesion strength (ASTM C633) improved from 18 to 27 to 34 MPa. Wettability followed the densification trend, with the contact angle increasing from 53.152° to 79.875° to 89.603°. Under dry ball-on-disk sliding against 100Cr6, the friction coefficient decreased and stabilized (0.648 ± 0.070 → 0.173 ± 0.050 → 0.138 ± 0.003), and the counterbody wear-scar area shrank by ~95.6% (0.889 → 0.479 → 0.0395 mm²). Wear-track morphology evolved from abrasive micro-cutting (as-sprayed) to reduced ploughing (flame-remelted) and a polishing-like regime with a thin tribo-film (furnace). Potentiodynamic tests indicated the lowest corrosion rate after furnace treatment (CR ≈ 0.005678 mm·year⁻¹). Overall, furnace heat treatment provided the best structure–property balance (lowest porosity and Ra, highest HV and adhesion, lowest and most stable μ, and superior corrosion resistance) and is recommended to extend the service life of NiCrFeBSiC coatings under dry sliding. Full article

Sustainable development and growing energy demand require the search for alternative fuels, especially for heavy transport. The study compared diesel fuel (DF), hydrogenated vegetable oil (HVO) and fuels from the pyrolysis of polypropylene (PPO), polystyrene (PSO) and car tyres (TPO). The lowest cold filter plugging point values were obtained for HVO (−38 °C) and PSO (−29 °C). TPO and DF were in the moderate range, while PPO achieved the worst result (−10 °C). Only DF met the EN 590 standard requirements for density at 15 °C (0.820–0.845) g/cm³. HVO and PPO were approx. 5% below the lower limit, while PSO and TPO exceeded the upper limit. All samples except PPO, which was below the lower limit, met the kinematic viscosity requirement according to the same standard at 40 °C (2.0–4.5) mm²/s. Based on a series of tribological tests, it was found that DF (400 µm) had the lowest lubricity expressed by the WSD index, while PSO (246 µm) had the highest. All samples tested met the requirements of EN 590, ASTM D975 and the Worldwide Fuel Charter in this respect. The results provide valuable information for engine technology, enabling more accurate durability predictions and fuel mixture optimization. Full article

The automotive industry has been employing Al alloys to reduce the weight of chassis; however, this can present some corrosion problems. In this research, we study the electrochemical behavior of SiO₂ superhydrophobic on Al 7075. The electrochemical techniques employed were cyclic potentiodynamic polarization (CPP), performed at a scan rate of 60 mV/s from −800 to 800 mV vs. OCP, and electrochemical impedance spectroscopy (EIS) at ±10 mV with frequencies ranging from 10 mHz to 100 kHz, as per ASTM G61 and ASTM G106. The electrolytes employed were NaCl and H₂SO₄ at 3.5 wt.% simulating marine and industrial atmospheres. The results showed that the coating presented an efficiency of 81% when exposed to NaCl, but the corrosion in this medium is localized. In H₂SO₄, the corrosion type is uniform. Full article

A systematic investigation into the solid particle erosion (SPE) of monolithic, sandwich-type hybrid and multi-scale (Multi Wallet Carbon Nanotube (MWCNT)-reinforced) glass/carbon fiber composites was performed confirming to the ASTM G76-18 standard, utilizing angular alumina erodent (~600 µm) at 34 m/s across key impingement angles of 30°, 45°, 60°, and 90°. The analysis reveals a profound performance dichotomy dictated by the governing wear mechanism. At the shear-dominated 30° angle, where maximum material loss was observed, hybridization consistently enhanced erosion resistance relative to both monolithic benchmarks. This synergy, however, contrasts sharply with the nuanced behavior under the 90° impact-dominant regime; here, although strategically hybridizing a brittle CFRP with tougher glass fibers reduced the erosion rate (ER) by a remarkable ~50%, this benefit was compromised by the matrix embrittlement induced by MWCNT incorporation. This work clarifies the difference between shear-dominated erosion in the ductile regime and fracture toughness under impact-dominated conditions. Full article

Spatial heterogeneity in soil deposition poses a significant challenge to accurate geotechnical characterization, which is essential for sustainable infrastructure development. This study presents an advanced geotechnical data-driven mapping framework, based on a monotonized and augmented formulation of Shepard’s inverse distance weighting (IDW) algorithm, implemented through the Google Earth Engine (GEE) platform. The approach is rigorously evaluated through a comparative analysis against the classical IDW and Kriging techniques using standard key performance indices (KPIs). Comprehensive field and laboratory data repositories were developed in accordance with international geotechnical standards (e.g., ASTM). Key geotechnical parameters, i.e., standard penetration test (SPT-N) values, shear wave velocity (Vs), soil classification, and plasticity index (PI), were used to generate high-resolution geospatial models for a previously unmapped region, thereby providing essential baseline data for building infrastructure design. The results indicate that the augmented IDW approach exhibits the best spatial gradient conservation and local anomaly detection performance, in alignment with Tobler’s First Law of Geography, and outperforms Kriging and classical IDW in terms of predictive accuracy and geologic plausibility. Compared to classical IDW and Kriging, the augmented IDW algorithm achieved up to a 44% average reduction in the RMSE and MAE, along with an approximately 30% improvement in NSE and PC. The difference in spatial areal coverage was found to be up to 20%, demonstrating an improved capacity to model spatial subsurface heterogeneity. Thematic design maps of the load intensity (LI), safe bearing capacity (SBC), and optimum foundation depth (OD) were constructed for ready application in practical design. This work not only establishes the inadequacy of conventional geostatistical methods in highly heterogeneous soil environments but also provides a scalable framework for geotechnical mapping with accuracy in data-poor environments. Full article

The development of thin, wear-resistant coatings is a relevant area in the field of surface engineering, especially given the increasing demand for resource efficiency and reliability of machine elements. In this study, we investigate the structural and phase composition, tribological characteristics, and physical and mechanical properties of zirconium carbonitride (ZrCN) coatings deposited by high-velocity oxygen-fuel spraying (HVOF) on U8G carbon steel substrates. Particular attention is paid to the influence of spraying parameters, in particular air pressure, on the formation of coatings and their performance properties. X-ray phase analysis methods revealed the formation of Zr₂CN, ZrC, ZrN, ZrO₂, and Fe₃O₄ phases, with the dominance of the cubic phase ZrN(C) with a lattice parameter of a = 4.6360 Å. Tribological tests have shown that at an air pressure of 0.38 MPa, the minimum friction coefficient is achieved, presumably due to the formation of an amorphous CN_x phase with a self-lubricating effect. The wear mechanism is predominantly abrasive in nature; the width of wear tracks is 329–759 μm. The coatings demonstrate a significant increase in microhardness—up to 1512–1857 HV, which is 4–4.5 times higher than the substrate. The results of adhesion tests carried out in accordance with ASTM D4541-22 showed a maximum adhesion strength of 14.56 MPa. The results obtained confirm the high efficiency of thin ZrCN coatings obtained by the HVOF method as a promising solution for protecting metal surfaces subject to intense wear in tribological systems. Full article

This study presents the results of experimental studies on the thermal conductivity of specimens made from selected pure polymer filaments manufactured with the use of FFF 3D-printing technology. The tested samples were made of polylactic acid (PLA), polyethylene terephthalate glycol (PET-G), and acrylonitrile butadiene styrene (ABS). In particular, the effects of the infill patterns and infill density on the tested samples were examined in order to characterize the influence of these parameters on the materials’ effective thermal conductivity. Honeycomb and grid infill patterns of the tested samples with infill densities of 40%, 60%, 80%, and 100% were examined. The influence of temperature on thermal conductivity was studied as well. Thermal conductivity was measured using the guarded heat flow method, according to the ASTM E1530 standard within the defined temperature ranges of 20–60 °C for ABS and PET-G and 20–50 °C for PLA material. Samples of the tested materials were manufactured with the use of the Fused Filament Fabrication method (FFF), and filaments with a uniform black color were used. The obtained results were analyzed in terms of thermal conductivity variation after samples’ infill pattern and infill density modifications, which provides extended thermal property characterization of the polymeric filaments adopted for 3D printing. Full article

Styles are invasive medical devices that are visible on images and are used in several medical specialties, including cardiology, neurology, orthopaedics, anaesthesia, oto-rhino-laryngology (ENT), and dentistry. With their thin and flexible design, they allow for the optimal positioning and precise guidance of medical devices such as nerve stimulation, defibrillation, electrode positioning, and catheter insertion. Generally, they are made of stainless steel, offering a combination of rigidity and flexibility. The aim of this study is to evaluate the sensitivity of austenitic stainless steel 304L used for the manufacture of J-stylets in uniform, pitting, crevice, and intergranular corrosion. We follow the manufacturing process step by step in order to analyse the risks of corrosion sensitisation and the cumulative effects of various forms of degradation, which could lead to a significant release of metal cations. Another objective of this study is to determine the optimal heat treatment temperature to minimise sensitivity to the intergranular corrosion of 304L steel. Uniform corrosion: Two samples were taken at each stage of the manufacturing process (eight steps in total), in the form of rods. After one hour of immersion, potentiodynamic polarisation curves were plotted up to ±400 mV vs. SCE. A coulometric analysis was also performed by integrating the anode zone between E (i = 0) and +400 mV vs. SCE. The values obtained by integration are expressed as mC/cm². The test medium used was a simulated artificial plasma solution (9 g/L NaCl solution). Intergranular corrosion: (a) Chemical test: Thirty rod-shaped samples were tested, representing the eight manufacturing steps, as well as heat treatments at 500 °C, 620 °C, and 750 °C, in accordance with ASTM A262 (F method). (b) Electrochemical Potentiokinetic Reactivation (EPR) according to ASTM G108–94 (2015). Two samples were tested for each condition: without heat treatment and after treatments at 500 °C, 620 °C, and 750 °C. Release of cations: The release of metal ions was evaluated in the following two media: artificial sweat, according to EN 1811:2011+A1:2015, and bone plasma, according to the Fitton-Jackson and Burks-Peck method. Six samples that had been heat-treated at 500 °C for one hour were analysed. Results, discussions: (a) Analysis of the polarisation curves revealed significant disturbances in the heat treatment steps, as well as the μC/cm² quantities, which were between 150,000 and 400,000 compared to only 40–180 for the other manufacturing steps; (b) Electrochemical Potentiokinetic reactivation (EPR) tests indicated that the temperature of 500 °C was a good choice to limit 304L steel sensitisation in intergranular corrosion; and (c) the quantities of cations released in EN 1811 sweat were of the order of a few μg/cm² week, as for Fe: 2.31, Cr: 0.05, and Ni: 0.12. Full article

The alkali–silica reaction (ASR) is an important mechanism of concrete deterioration, whereby reactive silica in aggregate interacts with cement alkalis to form expanding gel, which compromises the structural integrity of the concrete. Although the Republic of Korea has historically been classified as a low-risk region for ASR due to its geological stability, documented examples of concrete damage since the late 1990s have necessitated a rigorous reassessment of local aggregates. This study evaluated the ASR potential of 84 aggregate samples sourced from diverse Korean geological regions using standardized protocols, including ASTM C 1260 for mortar bar expansion and ASTM C 289 for chemical reactivity, supplemented by soundness, acid drainage, and weathering index analyses. The results indicate expansion within the range of 0.1–0.2%, classified as potentially deleterious, for some rock types. In addition to ASR reactivity, isolated high anomalies (e.g., high soundness, acid producing, and weathering) suggest the existence of other durability risks. Consequently, while Korean aggregates predominantly have a low ASR reactivity, the adoption of various validated ASR tests as a routine test and the integration of supplementary cementitious materials are recommended to ensure long-term concrete durability, highlighting the need for sustained monitoring and further investigation into mitigation strategies. Full article

In this study, solid particle erosion tests were conducted to evaluate the resistance of AISI 4340 (EN24) and 8620 alloy steels against silicon carbide (SiC). These steels were selected due to their high hardness, yield strength (σ_y), ultimate tensile strength (σ_uts) and elongation (%), which are significant parameters, influencing wear resistance. An erosion rig based on the ASTM G76-95 standard was used to perform the testing. Tests were carried out using different impact angles, 30°, 45°, 60° and 90°, with a particle velocity of 24 ± 2 m/s. The abrasive flow rate was 0.7 ± 0.5 g/min and the temperature was between 35 °C and 40 °C. Characterization techniques such as SEM were employed to identify the chemical composition of AISI 4340 and AISI 8620 steels and optical microscopy to determine the morphology of SiC abrasive particles. In addition, the SiC particle size was between 350 and 450 µm; it was determined by the particle size distribution technique. SEM micrographs were obtained to classify the wear mechanisms, characterized by micro-cutting, micro-ploughing, grooves, pitting actions and embedded particles on the surface at 30° and 90°. The results showed that AISI 8620 steel exhibited higher erosion resistance than AISI 4340 steel. Finally, AFM was used to evaluate the roughness variations before and after erosion tests, specifically in the central zone of the wear scars at 30° and 90° for both materials. Full article

Alternative energies have become relevant in global strategies to address climate change, and third-generation biodiesel derived from the generation of lipids from microalgae represents a viable option. This process can also be coupled with wastewater treatment to remove organic matter. To determine the effects of two catalyst levels (1 and 1.5% KOH) and two molar ratios of alcohol (methanol) with oil (1:6 and 1:9) on the conversion of lipids into FAMEs and the quality of the biodiesel produced, this work suggests a method for the ultrasonication-based extraction of lipids from C. vulgaris. It also employs an experimental 2² design and three replicates. It was found that with a molar ratio of 1:9 and a 1% catalyst, the highest yield of 98.48 ± 1.13% was achieved. The FAME profile was similar to the profiles obtained in cultures with bold basal medium or INETI. The quality of the biodiesel met ASTM standards, achieving refractive indices of 1.435–1.478. The flash point (FP) was 165 ± 18 °C, and the acid number was 0.31 ± 0.17 mg KOH/g. The viscosity ranged from 4.33 to 4.87 mm²/s. However, the rheological behavior was correlated with the Ostwald–de Waele model with pseudoplastic behavior. Full article

This article focuses on the possibilities of increasing the service life of tools for crushing unwanted growths. One way to increase their service life is to increase the hardness and resistance to abrasive wear of exposed surfaces of the tool, which are their face and back. At the same time, however, care must be taken to ensure that the shape and weight of the tool is not altered after the additive has been hardfaced on. Thus, the tool was first modified by removing the material by milling from the face and back. Subsequently, two surfacing materials, namely UTP 690 and OK WearTrode 55, were chosen and hardfaced by welding onto the pre-prepared surfaces. After hardfacing by welding, the tools were ground to their original shape and their weight was measured. Subsequently, the tool was sawn, and specimens were created for Rockwell hardness evaluation, material microstructure and for abrasive wear resistance testing as per ASTM G133-95. The OK WearTrode 55 electrode is a hardfacing electrode that produces weld metal with a high-volume fraction of fine carbides in a martensitic matrix. Better results were achieved by the UTP 690 hardfacing material. The hardness was 3.1 times higher compared to the base tool material 16MnCr5 and 1.2 times higher than the OK WearTrode 55 material. The abrasive wear resistance was 2.76 times higher compared to 16MnCr5, and 1.14 times higher compared to the OK WearTrode 55 material. The choice of a suitable pre-treatment for the tool and the selection and application of such additional material, which with its complex properties better resists the effects of the working environment, is a prerequisite for increasing the service life of tools working in forestry. Full article