Materials and Technology

OPTIMIZATION OF LASER SPOT WELDING PARAMETERS FOR 304 STAINLESS STEEL THIN SHEETS USING NUMERICAL SIMULATION

2026-04-09T11:05:38+02:00

Laser spot welding of stainless steel is widely used for connecting vehicle body structures and electronic components. In this study, numerical simulation of laser spot welding was conducted on lap joints of 304 austenitic stainless steel thin plates measuring 120 × 80 × 0.8 mm. The equivalent stress and total deformation of the welded joints under different welding sequences and fixture clamping forces were investigated, and the stress and deformation around the weld spots were characterized. The results demonstrate that at a laser power of 1300 W, the equivalent stress after welding with the sequence (1-4-3-6-2-5) reaches a minimum value of the maximum equivalent stress of 421.87 MPa, indicating the optimal welding sequence. Under the optimal welding sequence, when the clamping forces on both sides are 100 N, the equivalent stress and total deformation reach the lowest values of 421.87 MPa and 0.27 mm, respectively, representing the optimal fixture clamping forces. These findings provide guidance for optimizing the laser spot welding process in industrial applications.

LONG-TERM DEGRADATION MECHANISMS AND SERVICE LIFE PREDICTION OF BFRP AND GFRP BARS UNDER ALKALINE CORROSION ENVIRONMENTS

2026-04-09T11:05:39+02:00

Fiber reinforced polymer (FRP) composites are increasingly employed in civil infrastructure due to their high strength-to-weight ratio and corrosion resistance, yet their long-term durability in alkaline environments remains a critical concern for structural safety. This study investigated the long-term durability of basalt fiber reinforced polymer (BFRP) and glass fiber reinforced polymer (GFRP) bars that were exposed to alkaline corrosion environments. Accelerated aging tests were conducted at 40 °C and 60 °C to evaluate the degradation in tensile strength, interlaminar shear strength, and moisture absorption. The experimental results demonstrated that both BFRP and GFRP bars exhibited progressive deterioration, with BFRP showing more severe strength loss, particularly at elevated temperatures. Moisture uptake behavior was observed to follow Fickian diffusion in the early stage but later transitioned into nonlinear regimes, indicating structural changes that facilitated accelerated degradation. Scanning electron microscopy revealed that matrix corrosion was dominant at the initial stage, while fiber–matrix debonding and fiber corrosion became predominant with extended exposure, leading to void expansion and corrosion channel formation. An improved Fick-based degradation model was developed to predict the strength retention and service life of FRP bars. The model exhibited good agreement with experimental data, confirming its applicability for life prediction in practical engineering.

TENSILE DEFORMATION BEHAVIOR AND CONSTITUTIVE MODELING OF SOLID-SOLUTION-TREATED 6061 ALUMINUM ALLOY

2026-04-09T11:05:41+02:00

To systematically investigate the tensile deformation behavior of solid-solution-treated 6061 aluminum alloy under varying temperatures and strain rates and to establish an applicable constitutive model, uniaxial tensile tests were conducted using a 68TM-50 universal tensile testing machine and a Gleeble-3800 thermomechanical simulator. The experiments covered a temperature range of 25–300 °C and strain rates of 0.001–0.1 s^–1 to obtain true stress-strain data. The results indicate that, at a constant strain rate, the peak stress decreases significantly with increasing temperature, whereas at a constant temperature, the peak stress increases with the strain rate. Temperature exhibits a more pronounced influence on peak stress than strain rate. For room-temperature conditions (25 °C), the Swift model accurately predicts the deformation behavior, achieving an overall correlation coefficient (R) of 0.99846 and an average absolute relative error (AARE) of 1.41 %. For elevated temperatures (150 °C and 300 °C), a modified Johnson-Cook (J-C) model was developed by incorporating a quadratic polynomial strain-hardening term and a temperature-strain rate coupling factor, effectively integrating the effects of strain hardening, strain rate sensitivity, and thermal softening. The modified J-C model demonstrates robust predictive capability in the warm temperature regime, with an overall R of 0.99739 and an overall AARE of 5.29 %.

NUMERICAL SIMULATION OF PARTICLE DEPOSITION EFFICIENCY IN HVOF SPRAYING : MATERIALS EFFECT

2026-04-09T11:05:43+02:00

Particle critical velocity (for thermally sprayed particles) is not only the threshold for successful deposition of particles, but also a key parameter influencing deposition efficiency and coating quality. High velocity oxy-fuel (HVOF) thermal spraying is a well-established thermal spraying process, which has been extensively used in engineering fields. The coating produced by HVOF boasts the benefits of low porosity, low oxide content, and high adhesion. This study uses WC-Co and 316L stainless steel particles with different thermal conductivities as the spray particles, and develops the corresponding finite element models in Abaqus. A finite element model was developed to investigate two key aspects of HVOF thermal spraying: the relationship between particle critical velocity and particle diameter/temperature, and the influence of intrinsic material property variations on particle critical velocity. Numerical results show that particles with higher temperature and smaller diameter exhibit lower critical velocity and are more likely to form effective bonding with the substrate. Materials featuring high thermal conductivity and low specific heat capacity exhibit better heating capability. The better the heating ability, the more sensitive the material is. It can greatly affect the critical velocity, thereby enhancing the deposition efficiency of particles.

XSBRL-MODIFIED PHENOLIC RESIN COMPOSITES FOR BASKETBALL COURT SURFACES: MECHANICAL AND MICROSTRUCTURAL CHARACTERIZATION

2026-04-09T11:05:44+02:00

High joint injury rates in basketball are frequently linked to the inadequate shock absorption of traditional court surfaces. This study investigates a carboxylated styrene-butadiene rubber latex (XSBRL)-modified phenolic resin composite, reinforced with magnesium calcium sand, to address the trade-off between safety and durability. Results indicate that 12 w/% XSBRL yields optimal mechanical properties, achieving a 90-day compressive strength of 68 MPa and a flexural strength of 4.5 MPa. Consequently, the composite exhibits superior biomechanics with 55 % impact absorption – significantly outperforming hardwood (35 %) and polyurethane (48 %) – and an ideal static friction coefficient of 0.68. Microstructural analysis via SEM confirmed a brittle-to-ductile fracture transition, clarifying the mechanism behind the enhanced toughness. Furthermore, process reproducibility was secured through an orthogonal experimental design. This optimized XSBRL-modified composite demonstrates a superior balance of performance and protection, offering a robust solution for next-generation basketball court construction.

PERFORMANCE OPTIMIZATION AND MOLECULAR DYNAMICS MECHANISM OF COMPOSITE INSULATING SILICONE RUBBER AFTER ELECTRIC HEATING POST-TREATMENT

2026-04-09T11:05:46+02:00

This study investigates the optimization of composite silicone rubber (SR) through a physical electrothermal post-treatment process that functions as an efficient structural annealing method. The aim is to enhance the material’s intrinsic properties without relying on formulation modifications. Experimental results show that post-treatment at 300 °C for 1 h significantly improved the material’s mechanical properties, achieving a simultaneous increase in stiffness and toughness: tensile strength and Young’s modulus (YM) rose by 45 % (to 14.9 MPa) and 56 % (to 0.75 GPa), respectively, while elongation at break improved to 391 %. Molecular dynamics (MD) simulations were employed to understand the microscopic mechanisms behind these improvements. The post-treatment process increased the crosslink density (CD) from 78 % to 92 %, leading to a densified molecular chain network, with a reduction in the free volume fraction (FVF). The simulated YM growth (+49 %) closely matched the experimental increase (+56 %), confirming that crosslink network optimization was the main contributor to performance enhancement. Thermal performance analysis revealed that the glass transition temperature (Tg) increased from –48.5 °C to –42.1 °C, alongside an improvement in thermal stability. Electrical properties also improved, with a reduction in the dielectric constant and an increase in insulation resistance by 24 % (to 310.7 MW). This study demonstrates that electrothermal post-treatment, guided by MD simulations, effectively enhances the performance of SR, offering a reliable endogenous optimization alternative to traditional additive-based modification techniques.

STUDY ON THE ELECTROCHEMICAL CORROSION BEHAVIOR OF Mg-xSn-0.6Ca (x = 1, 2, 6, 7) ALLOYS

2026-04-09T11:05:48+02:00

This study systematically investigated the effects of different Sn contents on the microstructure and electrochemical corrosion behavior of Mg-xSn-0.6Ca (x = 1, 2, 6, 7) alloys. The corrosion behavior of the alloys in a 3.5 w/% NaCl solution was evaluated using hydrogen evolution weight loss analysis, potentiodynamic polarization curve analysis, and electrochemical impedance spectroscopy (EIS). The results indicate that as the Sn content increases, the quantity and size of the Mg₂Sn and CaMgSn secondary phases in the alloys significantly increase, effectively hindering the diffusion of corrosive media, thereby enhancing the corrosion resistance of the alloys. When the Sn content is 6 %, the Mg-6Sn-0.6Ca alloy exhibits the best corrosion resistance. Electrochemical test results show that the Mg-6Sn-0.6Ca alloy has the lowest self-corrosion current density. Additionally, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analyses reveal that the synergistic effect of Sn and Ca elements significantly improves the corrosion resistance of the alloy. However, an excessive Sn content (e.g., 7 %) may lead to localized micro-galvanic corrosion, reducing the corrosion resistance.

EFFECTS OF LASER POWER, SCAN SPEED AND HEAT TREATMENT ON MICROSTRUCTURE AND HARDNESS OF PBF-LB INCONEL 718

2026-04-09T11:05:49+02:00

This study quantifies the effects of laser power and scan speed on the aged microstructure and hardness of PBF-LB Inconel 718 processed under the EOS-standard heat-treatment schedule. Cylindrical specimens were fabricated on an EOS M290 using six power–speed combinations spanning a line energy (E_line = P/v) range of 0.167–0.583 J·mm^–1, followed by solution annealing and double ageing according to the EOS recommendation. Microstructure was assessed by EBSD, and hardness was measured in both the as-built and aged conditions. EBSD revealed build-direction-aligned columnar  grains under all conditions, while increasing line energy was associated with a progressively coarser boundary/subgrain network. The lowest line-energy (highest scan-speed) condition (200 W/1200 mm·s^–1; 0.167 J·mm^–1) achieved the highest post-age hardness (459 HV5), whereas the highest line-energy condition (350 W/600 mm·s^–1; 0.583 J·mm^–1) exhibited the lowest hardness (438 HV5) together with void-like, non-indexed features consistent with porosity. Overall, the results provide a compact process–structure–property map and energy-aware guidance for selecting PBF-LB Inconel 718 parameter windows, highlighting that while lower line-energy conditions maximise performance, higher-speed regimes may still deliver sufficient quality for short-life or productivity-driven components.

FIRST-PRINCIPLE CALCULATIONS OF THE SYNERGISTIC CATALYTIC PERFORMANCE OF GRAPHENE AND TRANSITION METALS FOR MGH2 DEHYDROGENATION

2026-04-09T11:05:52+02:00

To address the challenges of high dehydrogenation temperature and sluggish kinetics in magnesium hydride (MgH₂), this study systematically investigates the synergistic catalytic effects of transition metals (Ni, Fe, Cu, Cr, Sc) anchored on monolayer graphene in enhancing the dehydrogenation performance of magnesium-based hydrogen storage materials. First-principles calculations were performed using density functional theory (DFT) within the generalized gradient approximation (GGA), combined with a double numerical plus polarization (DNP) basis set. The computational results demonstrate that Ni-, Cr-, and Cu-modified graphene substrates significantly reduce both the dehydrogenation enthalpy and reaction energy barrier of Mg₄H₈ clusters. Charge density analysis, density of states, and differential charge density calculations were employed to elucidate the electronic interactions and charge redistribution within these systems. These analyses confirm a substantial weakening of the Mg–H bonds in Mg₄H₈, which effectively facilitates hydrogen desorption. Comprehensive evaluation based on thermodynamic and kinetic parameters, including dehydrogenation enthalpy, activation energy, and electronic structure features, establishes that the Cu/graphene composite doping exhibits the most pronounced improvement, achieving the optimal dehydrogenation performance of MgH₂. This work provides valuable theoretical insights and predictive guidance for the rational design of high-efficiency catalytic systems in magnesium-based hydrogen storage applications.

REPEATABILITY OF MECHANICAL MUSCLE ACTIVITY MEASUREMENTS USING A MUSCLE CONTRACTION (MC) SENSOR: TIME-SERIES AND DISCRETE VARIABLE ANALYSIS OF THE VASTUS MEDIALIS

2026-04-09T11:05:53+02:00

The primary objective of this study was to provide empirical evidence of the repeatability of the muscle contraction (MC) sensor signal and the associated measurement methodology based on a discrete covariate analysis. Despite the growing interest in this technology, the repeatability of MC sensor measurements across different environments and applications has not yet been systematically investigated, which is essential for establishing the reliability and practical applicability of these sensors. Therefore, this study presents a comprehensive repeatability analysis of MC sensor measurements obtained from the vastus medialis muscle of the thigh. This study provides strong evidence for the repeatability of muscle contraction (MC) sensor signals and the associated thigh muscle measurement methodology. Furthermore, the results highlight the potential of MC sensor technology for real-time investigation of mechanical muscle activity, offering a promising alternative to existing measurement techniques.

MICROSTRUCTURAL EVOLUTION AND HARDNESS OF FERRITIC SUPERALLOYS CONTAINING NiAl-B2 AND L21–Ni2TiAl PRECIPITATES

2026-04-09T11:05:55+02:00

This study investigates the effect of homogenization and aging treatments on the microstructure and hardness of ferritic superalloys containing NiAl-B2 and L2₁–Ni₂TiAl precipitates. Two alloy compositions were prepared using an electric arc furnace, with Ti additions of 2 w/% (Alloy I) and 4 w/% (Alloy II). The ingots were homogenized at 1150 °C for 10 h followed by furnace cooling, and subsequently aged at 800 °C for 8 h. Characterization was conducted using scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Vickers hardness testing. The as-cast alloys exhibited the highest hardness, averaging 650.8 HV for Alloy I and 625.6 HV for Alloy II, due to the presence of metastable precipitates formed during rapid solidification. Homogenization reduced the hardness to 487.2 HV (Alloy I) and 522.6 HV (Alloy II) as a result of precipitate dissolution and redistribution of the alloying elements, while aging increased the hardness to approximately 525 HV in both alloys through secondary precipitation of the NiAl-B2 and L2₁–Ni₂TiAl with finer and more homogeneous distributions. SEM-EDS confirmed that Alloy I exhibited a more uniform dispersion of precipitates, whereas Alloy II contained a greater quantity of Ni₂TiAl, but with local agglomerations. In conclusion, homogenization and aging treatments strongly influenced the precipitation behavior and hardness of ferritic superalloys, with Alloy I showing superior homogeneity and Alloy II favoring greater Ni₂TiAl formation, highlighting the effect of Ti content on phase stability and mechanical performance.

DEVELOPMENT OF Cu- AND Fe-DOPED ZEOLITE-COATED CERAMIC FOAMS AS FUNCTIONAL CATALYSTS FOR AUTOMOTIVE NOx REDUCTION

2026-04-17T07:15:00+02:00

The effective control of nitrogen oxides (NO_x) from gasoline engines remains a critical challenge for sustainable emission management, as conventional three-way catalytic converters (TWCs) exhibit limited NO_x conversion efficiency under oxygen-rich exhaust conditions. This study presents the development and evaluation of metal-doped zeolite-based catalysts – Cu-ZSM-5 and Fe-ZSM-5 – coated onto ceramic foam substrates as advanced alternatives to conventional noble-metal honeycomb monoliths. The catalysts were synthesized via ion-exchange methods and characterized using XRF, SEM, and XRD to confirm successful metal incorporation without compromising the zeolite’s MFI crystalline framework. Engine tests were conducted on a twin-cylinder, 624 cm³ spark ignition engine to compare the catalytic performance of the laboratory-fabricated converters with a commercial TWC. Results demonstrated superior NO_x reduction efficiencies of 71 % and 76 % for Cu- and Fe-doped zeolite converters, respectively, at maximum load conditions. Fe-ZSM-5 exhibited enhanced high-temperature NO_x conversion (up to 79 %), whereas Cu-ZSM-5 showed better low-temperature activity. Both catalysts also achieved higher CO (up to 89 %) and HC (up to 95 %) conversion efficiencies compared to the commercial system. Although a minor decrease in brake thermal efficiency was observed due to the increased backpressure of the ceramic foam substrate, the overall performance indicates that metal-doped zeolite-coated ceramic converters provide a cost-effective, thermally stable, and environmentally sustainable alternative to noble-metal TWCs. This work advances the practical application of zeolite-based catalysts for next-generation automotive emission control systems.

COMPARISON OF TWO METHODS: DENTAL ARCH IMPRESSIONS AND INTRAORAL SCANNING

2026-04-09T11:05:58+02:00

This study compared traditional alginate impressions with intraoral scanning (IOS) in terms of time efficiency, anatomical detail, cost, and patient comfort. Twenty patients underwent both impression techniques using Aroma Fast Plus alginate and the 3Shape Trios 3 scanner. The resulting plaster and 3D-printed models were assessed digitally, and patient experiences were evaluated using questionnaires. The mean time for alginate impressions was 283.57 s (SD = 37.66), while IOS took 358.86 s (SD = 44.13), a statistically significant difference (t = –4.679, p = 0.003). Despite the longer IOS time, the digital workflow allowed for simplified logistics, reduced manual labor, and immediate transmission of the scan files to the laboratory. Anatomical detail was found to be comparable overall, although alginate impressions captured vestibular soft tissue more extensively (p < 0.001), while digital scans more precisely reproduced the dental morphology in specific regions, such as interproximal spaces and cervical crown contours. Patient responses strongly favored 3D scanning. Comfort scores were significantly higher for IOS than for alginate (mean = 8.25 versus 6.07, respectively), and participants with a pronounced gag reflex reported less discomfort during digital scanning. All participants preferred the digital method over traditional impressions. While alginate impressions remain advantageous for soft tissue capture the digital workflow proved more efficient and better tolerated by patients. These findings support the broader clinical use of IOS in dentistry.

EXPERIMENTAL AND ANN-BASED INVESTIGATION OF RUBBERIZED GEOPOLYMER CONCRETE FOR SUSTAINABLE CONSTRUCTION

2026-04-09T11:06:00+02:00

This study develops a mix design for geopolymer concrete (GPC) incorporating waste tyre rubber as a partial replacement for fine aggregate. Standard cube and beam specimens were cast and tested for compressive strength, and the resulting experimental data were used to train an artificial neural network (ANN) model for strength prediction. The proposed AI-driven framework enables the early estimation of compressive strength, reducing reliance on extensive laboratory testing and supporting timely decision-making in material design and quality control. The ANN model achieved R² values of 0.70, 0.42, and 0.57 on the training, validation, and test datasets, respectively, indicating moderate and consistent predictive performance. The network employs a two-layer feedforward architecture with seven input parameters, a sigmoid activation function in the hidden layer, and a linear output layer. While the model demonstrates reliable performance, further improvements through hyperparameter tuning and expanded datasets are anticipated. By integrating recycled tyre rubber into the GPC, the study addresses environmental and economic concerns, promotes sustainable construction practices, and supports circular-economy principles by valorising waste materials.

THE EFFECT OF WAX EMULSION ON THE PERFORMANCE OF CHROMIUM-FREE ANTI-FINGERPRINT PASSIVATION FILM

2026-04-09T11:06:02+02:00

Limited research exists on the passivation film of anionic waterborne polyurethane resin, particularly regarding strategies to enhance its performance. This study investigates the influence of the wax emulsion’s particle size and concentration on the structure, interfacial behavior, corrosion resistance, friction resistance, and adhesion properties of the passivation film. Findings reveal that using a 450-nm wax-emulsion particle size and a 2 % addition yield a composite passivation film characterized by a high surface gloss, low roughness, and exceptional friction resistance. Notably, while maintaining adhesion, the corrosion resistance is improved, thereby enhancing the overall performance of the passivation film. This research sheds light on the effects of wax emulsion on the performance of passivation films, providing valuable insights for optimizing anionic waterborne polyurethane-resin passivation films in future studies.

GROWTH FACTOR LOADED BIOMATERIALS FOR PERIODONTAL TISSUE REGENERATION: A SYSTEMATIC REVIEW OF PRECLINICAL STUDIES ON ANIMAL MODELS

2026-04-09T11:06:03+02:00

Over the past decade, numerous biomaterials have been developed for periodontal tissue regeneration. The aim of this systematic review was to evaluate the application of growth factor–loaded biomaterials for the regeneration of the periodontal complex in preclinical animal studies. The review was conducted in accordance with PRISMA guidelines. A computerized search of SCOPUS, PubMed, and Web of Science was performed, including English-language articles published between 2015 and 2025. From an initial yield of 173 articles, 12 studies met the inclusion criteria after screening titles, abstracts, and full texts. All included studies demonstrated successful regeneration of the three key periodontal tissues – alveolar bone, cementum, and periodontal ligament – in animal models. With one exception, the studies were short-term, with histological evaluations performed up to 12 weeks. The biomaterials used ranged from relatively simple systems to complex multiphasic scaffolds. Six studies employed biomaterials loaded with a single growth factor, while the remaining six used combinations of two or more growth factors. Fibroblast growth factor (FGF) was the most frequently used growth factor, followed by bone morphogenetic proteins (BMPs). The findings indicate that scaffolds are the most commonly used biomaterial platform, and that FGF- and BMP-based systems are predominant. Notably, simpler biomaterial and growth factor combinations often achieve regenerative outcomes comparable to more complex scaffold designs but remain robust, especially when the goal is functional regeneration.

MECHANISMS OF LARGE PARTICLE SPALLATION IN THERMAL FATIGUE OF HIGH-CHROMIUM TOOL STEEL

2026-04-09T11:06:05+02:00

High-chromium steels used for hot rolling work rolls are exposed to severe cyclic thermal and mechanical loads, which often lead to unexpected early failure due to large particle spalling. This study investigates the mechanisms of oxidation-assisted cracking that promote early spallation under thermal fatigue conditions. Laboratory tests were performed on centrifugally cast high-chromium steel using a thermomechanical simulator to replicate harsh oxidation and cyclic heating environments. Microstructural analysis revealed that eutectic carbides and chromium-depleted regions are particularly susceptible to oxidation, accelerated crack initiation and growth. Three distinct modes of crack linking were identified as critical pathways for large particle spalling: (Mode 1) direct linking of radial cracks, (Mode 2) linking of radial cracks via lateral cracks, and (Mode 3) linking of radial cracks via oxidized eutectic carbides. The results highlight combined influence of oxidation, carbide network arrangement, and thermal stress on early spallation of large particles, providing new insights into roll surface degradation and potential directions for improving roll lifetime in industrial hot rolling.

ADAPTING QUALITY PLANNING TOOLS TO EVOLVING PRODUCTS AND MANUFACTURING PROCESSES: THE CASE OF FMEA

2026-04-09T11:06:06+02:00

This study examines the evolution of design failure mode and effects analysis (DFMEA) in response to the automotive product transformation from conventional to mechatronic systems. The research combines a literature review with case studies to identify key changes in risk assessment methodology. The analysis compares severity ratings between conventional and mechatronic systems, with reference to the corresponding process failure mode and effects analysis (PFMEA) changes. Results indicate systematic increases in the severity of failure modes in the mechatronic DFMEA and decreasing differences between DFMEA and PFMEA risk assessments, reflecting the blurring of the boundaries between design and process risks. The study confirms the need for a more systemic risk analysis that considers complex component interactions and the increased impact of the production process on modern mechatronic product functionality.

ANALYSIS OF DUST-PARTICLE EMISSIONS DURING THE CUTTING OF S460 TOOL STEEL

2026-04-09T11:06:07+02:00

Oxyfuel cutting and plasma cutting were investigated with respect to the particulate emissions generated during the cutting of SIHARD S460 cold-work tool steel. The aim of the study was to compare the amount and characteristics of the particles emitted during the two cutting processes. Particles were collected by sampling and analyzed gravimetrically, while their size, morphology, and chemical composition were characterized using FEG-SEM and EDXS. The results indicated that oxyfuel cutting generated higher particulate emissions than plasma cutting, with emission rates of 0.096 g/h and 0.066 g/h, respectively. Oxyfuel cutting produced a higher fraction of particles below 1.75 µm, while particles larger than 5.5 µm were observed only for plasma cutting. All the analyzed particles were smaller than 10 µm. EDXS analysis further revealed that a substantial fraction of the collected particulate matter consisted of metal oxide particles formed during thermal cutting. Overall, oxyfuel cutting was identified as the more intensive source of fine particulate emissions during the processing of SIHARD S460 steel.