Magnesium–zinc alloys in the homogenized condition with various grain sizes (D) and different Zn contents in the α-Mg matrix (xZn) were obtained by adding different amounts of Zn, Ca, and Sr and two-step homogenization treatment. It was revealed that with increasing Zn content, D decreases; while xZn increases upon homogenization. Moreover, Ca and Sr addition leads to grain refinement and change in the possibility of secondary phase dissolution, affecting xZn. Regarding mechanical properties, the main hardening/strengthening effects were characterized as grain boundary strengthening and solid solution via Zn dissolution. As a result, the classical Hall-Petch relationship was unable to present the grain size dependency of hardness (H) and yield stress (YS). To address this issue, the solid solution effect was incorporated into the Hall-Petch relationship, showing improved agreement with the measured H and YS. Accordingly, the modified Hall-Petch formulae of H = 32 + 6xZn + 66.5/√D and YS = 26.2 + 10.54xZn + 159.6/√D were proposed and verified based on the leave-one-out cross-validation (LOOCV) approach. In summary, this work provided preliminary empirical correlations valid for the investigated alloy set and homogenization conditions.
The article develops a novel comprehensive multi-directional and multi-physics framework for analyzing the coupled vibro–electro–magnetic response of advanced smart plate structures. It investigates the porosity-dependent vibration behavior of multi-directional functionally graded magneto-electro-elastic (MFG-MEE) porous plates subjected to externally applied magneto-electrical potentials. The kinematic relations are derived using a refined four-variable shear deformation plate theory. The magneto-electro-elastic properties of the MFG plate varied smoothly along the three directions (length, width, and thickness), are estimated by using the modified power-law rule. Two distinct porosity distribution patterns are incorporated to characterize void and cavity variations through the plate thickness. The governing equations consist of six coupled partial differential equations with variable coefficients are derived. The differential quadrature method (DQM) is employed to discretize these equations, while the integral quadrature method (IQM) efficiently handles the variable coefficients. The accuracy of the proposed model and solution methodology is validated through comparisons with available results in the literature, yielding relative errors ranging from 0.01 to 4.7
This paper focuses on sandwich panels with stepped functionally graded material (FGM) layers and initial geometric imperfections, exploring their nonlinear transient behavior when placed on viscoelastic bases and subjected to sinusoidal forces. The three-layer composition involves a uniform core, with upper and lower FGM face sheets exhibiting a stepped thickness profile. The face sheets are divided into two segments of distinct thicknesses along both the length and width directions, achieving optimal stiffness enhancement while maintaining a constant total thickness. The FGM face sheets exhibit thickness-dependent material properties following a power-law distribution. Utilizing the third-order shear deformation theory (TSDT) and incorporating initial geometric imperfections along with von Kármán geometric nonlinearity, a theoretical model was developed. The governing equations are solved via the Galerkin and Runge–Kutta methods, with model accuracy validated against existing literature and finite element analysis results. In the numerical analysis, four different geometric configurations of the sandwich plates are selected to examine the influence of key parameters, including initial geometric imperfections, aspect ratio, thickness ratio, damping coefficient, load amplitude, load duration, and power-law index, on the transient response of the sandwich plates. The findings of this study provide a theoretical basis for the dynamic design and optimization of stepped FGM sandwich structures with initial geometric imperfections.
Laser metal deposition (LMD) of AlSi10Mg alloy often leads to coarse columnar dendrites, a continuous network of eutectic Si phase, and residual porosity, which degrade mechanical properties and corrosion resistance. In this study, friction stir processing (FSP) was applied to modify the LMD‑fabricated AlSi10Mg alloy. The effects of FSP on the microstructure evolution, phase distribution, elemental homogeneity, microhardness, wear resistance, and corrosion resistance were systematically investigated. The results show that FSP induces intense dynamic recrystallization, transforming the coarse, textured columnar grains into fine, uniform equiaxed grains with an average size reduced from 65.15 μm to 3.26 μm. The continuous network of eutectic Si is broken and redistributed into fine, dispersed particles, and elemental segregation (especially Si) is largely eliminated. These microstructural changes lead to a significant increase in microhardness (from 80 HV0.2 to 105 HV0.2), a 46
NiCr–Cr3C2–xTiC coatings were fabricated with different TiC contents were fabricated using laser deposition, and the effects of TiC content on the microstructural evolution and tribological performance of obtained coatings were systematically investigated. The results indicate that the TiC content influences the phase composition and microstructural characteristics of coatings, and the reinforcing particles become more uniformly distributed and finer with the increase of TiC content, promoting the grain refinement and enhancing coating density. The optimized microstructure leads to the improved hardness and wear resistance, showing that the TiC reinforcement enhances the microhardness and load-bearing capacity of coatings, reducing the coefficients of friction and wear rates. Furthermore, the wear mechanism of coatings with the high TiC content exhibits micro-plastic deformation and fine debris removal, whereas that of coatings with the low TiC content shows brittle fracture-dominated wear. These findings demonstrate that the control of TiC content can effectively tailor the microstructure of laser-deposited NiCr–Cr3C2–xTiC coatings, achieving the enhancement of tribological performance and providing the guidance for the design of high-wear-resistant coatings.
The dissimilar joining of high-nitrogen high-manganese steel (HMS) frogs and high-carbon steel (HCS) rails is susceptible to performance mismatch and interfacial defects. To mitigate these issues, an austenitic stainless steel (SS) interlayer was introduced, and HMS–SS–HCS joints were fabricated by flash butt welding (FBW). With constant parameters on the HCS side, a baseline process (Process I) and an intensified process (Process II) with increased melting and upsetting were applied on the HMS side. Compared with Process I (burn-off length 6.7 mm; upsetting displacement 21.0 mm), Process II increased burn-off length and upsetting displacement by 25.4
This paper integrated experimental and two-step numerical simulation methods (S-ALE and SPH) to systematically investigate the interfacial microstructural characteristics of explosive-welded N4/Q235 steel clad plates, and the thermomechanical behavior at the interface, along with the formation mechanisms of defects and grain structures, were further elucidated. Subsequently, post-weld heat treatment (PWHT) was performed on the clad plate over a temperature range of 923 K to 1223 K, and its effects on the interfacial microstructure evolution and mechanical properties were investigated. The results showed that the interfacial waveform exhibited good agreement with the numerical simulation results. Obvious grain refinement occurred near the interface, and fine columnar grains formed in the vortex zone. Significant element mixing and diffusion phenomena existed in the vortex molten zone (VMZ) and the interfacial molten zone (IMZ). As the PWHT temperature increased, the intermetallic compounds in the interfacial diffusion layer gradually melted, and a solid solution structure dominated by γ - ( Fe,Ni) formed at the interface. The grains on the steel side began to recrystallize and continued to grow, and at 1223 K they all exhibited abnormally coarse characteristics. The diffusion layer thickness increased with PWHT temperature. Mechanical property tests indicated that the microhardness near the Q235 steel side first decreased and then increased as the PWHT temperature rose. The clad plate possessed both high ductility (48.8
Burr formation is a concentrated manifestation of micro milling mechanics, material dynamic response, and multi-physics coupling. In micro milling process, burrs are the key factor directly determining the precision, performance, reliability, and manufacturing cost of micro-parts. This study focuses on the mechanism of surface generation and burr formation during micro slot milling. Three-dimensional finite element simulation models are established for micro-scale and conventional- scale milling processes respectively, which dynamically demonstrate entire procedure of tool engagement and disengagement, chip formation and material removal for micro-milling cutters and conventional milling cutters respectively. The stress-strain distribution and chip formation mechanism between micro-scale and conventional- scale milling are compared and analyzed, revealing the dynamic characteristics of material deformation, fracture and burr evolution in the micro slot milling process. Besides, micro slot milling experiments are conducted on the typical plastic material of brass to investigate the time-varying characteristics of micro slot milling force signal waveforms as well as the burr height and width, and the surface quality and topography of the micro slot bottom. Moreover, the influence laws of spindle speed, feed rate and milling depth on surface roughness, burr size and cross sectional profile are explored and main influencing factors are quantitatively analyzed. The research results provide a theoretical basis and practical guidance for optimizing quality and improving accuracy of micro slot milling process.
Seismic pounding between adjacent structures is a significant concern in earthquake engineering, particularly in urban environments where insufficient separation distances are prevalent. This study investigates the effects of structural pounding on the seismic response of a base-isolated RC building placed next to a fixed-base structure, considering various pounding configurations and separation distances under near-field ground motions. The effects of geometric misalignment and insufficient seismic separation gaps are also evaluated in terms of selected structural response parameters and the seismic performance of adjacent buildings. To this aim, a four-story RC building was modelled with lead-rubber bearings (LRBs) as the base isolation system, while the adjacent structure was modelled as a conventional fixed-base building with similar geometric characteristics. Four different pounding configurations were defined based on the transverse offset between the buildings, representing common in-plan misalignments observed in real urban layouts. For each configuration, four levels of separation distances were introduced to assess the influence of clearance. The structural responses examined in the study include plastic hinge rotations of beams and columns, inter-story pounding forces, story accelerations, torsional moments, story rotations, and isolation story displacements. The results revealed that when sufficient separation distance (100
To enhance the utilization of coal-based solid wastes and address the challenges associated with real-time characterization and prediction of damage in backfill during service, this study develops a cemented backfill jointly activated by coal gangue, fly ash, gasification slag, and desulfurization gypsum. In addition, a full-process damage constitutive modeling method integrating acoustic emission (AE) characteristic parameters with binary medium theory is proposed. First, the optimal mix proportion was determined using an orthogonal experimental design. Uniaxial compression tests with synchronous AE monitoring were subsequently conducted on specimens prepared with the optimal mixture at different curing ages to reveal the staged characteristics of damage evolution and the law of characteristic stresses; the macro–micro correlation mechanism was further elucidated on the basis of microstructural observations. The results indicate that the optimal mixture consists of 60
Utilizing the laminated Ni/Al sheets (LANS) with excellent plastic deformation capability prepared by vacuum hot-pressing and subsequent in-situ reaction, holds significant potential for the fabrication of NiAl complex thin-walled component. In this paper, the GTN damage model was applied to the Ni and Al layers in LANS, while a brittle fracture model was adopted for the Ni-Al intermetallic layer between the Ni and Al layers, thereby establishing a high-temperature deformation damage model for LANS. The initial parameters of the damage model were obtained by high-temperature uniaxial tensile experiments and microstructural characterization. The damage and fracture mechanisms of LANS during high-temperature deformation were investigated through in-situ microstructural observation during tensile tests and simulation, validating the rationality of the model construction. Moreover, through hot gas bulging experiments and simulations, the high-temperature forming limit curve (FLC) of LANS was plotted. The results demonstrated that the hybrid LANS damage model is reasonable, as the fracture strain predicted by the tensile simulation agreed well with experimental results, with an error of less than 5
In the context of increasing circularity in steel recycling and the connected increasing build-up of residual elements in the steel industry, the present study investigates the influence of Mo, Cu, and hot plastic deformation on critical temperatures and phase transformation kinetics of 4 wt
This study investigates the synergistic effects of nano-clay (NC) incorporation and waste tire aggregate (TA) substitution on the mechanical, thermal, and durability performance of alkali-activated composites (AACs). Ground granulated blast furnace slag (GBFS) served as the primary precursor, with NC introduced at 0–5
Submerged concrete infrastructure in semi-enclosed marine basins is exposed to a complex set of degradation factors, including chloride and sulphate attack, biofouling and, in the case of the Baltic Sea, the suspected influence of historically dumped chemical munitions. Conventional condition assessment relies on core drilling, which is costly, logistically demanding and unacceptable in areas where unexploded ordnance or chemical contamination cannot be ruled out. However, no validated, minimally invasive analytical protocol has been established for those environments. This study validates that “samples of opportunity” - loose concrete fragments retrieved by remotely operated vehicles from three Southern Baltic Sea harbours (Puck, Ustka, Kołobrzeg) - when inspected through correlative X-ray micro-computed tomography (µCT) and scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS), provide quantitative and site-specific evidence of the underlying degradation mechanisms. µCT analysis revealed pore volume fractions ranging from 0.78
This study investigates the influence of a polyaniline–chitosan (PANI: CS) polymer blend used as a dual-functional additive on the rheological, aging, fatigue, and performance properties of bitumen binders and asphalt mixtures. Two road bitumens (70/100 and 50/70) were modified under different technological conditions and evaluated using conventional physical tests, aging simulations, and fatigue characterization based on the Linear Amplitude Sweep (LAS) method combined with the Viscoelastic Continuum Damage (VECD) model. Asphalt mixtures produced using hot mix asphalt (HMA) and warm mix asphalt (WMA) technologies containing reclaimed asphalt pavement (RAP) were also analyzed in terms of volumetric properties, moisture resistance, stiffness modulus, and environmental performance using a screening life cycle assessment. Modification with the PANI: CS blend resulted in a 23–38
This study examines the production of lightweight foamed geopolymers using aluminum powder as the main foaming agent and lime as both a partial replacement for ground granulated blast-furnace slag (GGBFS) and a secondary contributor to pore formation. While the individual effects of aluminum powder and lime have been reported in the literature, their combined use in GGBFS-based foamed geopolymers has received little attention. In particular, the influence of lime on both matrix development and pore generation remains unclear. Nine mixtures were prepared by varying the lime content between 0 and 20
This paper is an attempt at a holistic and synthetic presentation of the key theoretical and technical aspects of the sensory monitoring of bridges during their building and operational use. The authors – on the basis of their many-year investigations of bridges and their experience gained through participation in domestic and international research projects – undertook an attempt to make the domain knowledge relating to the sensory monitoring of bridges more specific, structured and uniform. Comprehensive methodological framework for monitoring bridges by means of electronic instrumentation systems has been created; offering a step-by-step structured approach to carrying out monitoring tasks and achieving their goals. Comparison of the sensory monitoring with the inspection-based monitoring of bridge condition is presented, taking into account load-independent and load dependent diagnostic methods. Qualification of bridges demanding sensory monitoring as well as taxonomy of sensory monitoring systems are described, together with bridge performance indicators. Developed procedures for the design of monitoring systems architecture and functionality, selection of measuring technologies, implementation and operation of sensory monitoring systems are presented, taking into account problems relating to the acquisition, processing, analysis of measurement results and their use in the evaluation of technical and operating parameters of a bridge.
Occupational accidents remain one of the key challenges for modern work systems, both from the perspective of employee health and life, and in terms of economic, social, and organisational losses for society. Despite the significant diagnostic value of near misses, data on such events have not been incorporated as input variables in predictive models. This study aimed to develop, experimentally test, and empirically validate the effectiveness of various mathematical models in predicting occupational accidents. The performance of thirteen machine learning and deep learning algorithms, including Random Forest, logistic regression, SVC, ARIMA, SARIMAX, and a proposed modified convolutional neural network incorporating Bayesian correction and a tailored ReLU activation function, was compared. The best results were achieved with a CNNKT model, yielding an accuracy of 0.939, an F1-score of 0.934, and a G-Mean of 0.942. The findings confirm the superiority of deep convolutional networks over traditional statistical models in occupational safety analysis.
This study aimed to ascertain the possibility of replacing fly ash in alkali-activated materials (AAMs) with residues obtained through the extraction of chlorine from cement bypass dust (CBPDex). The effects of different cement bypass dust contents (5, 10, 15 and 20
Brass-dominant multilayered composites reinforced with St14 steel were fabricated by accumulative roll bonding (ARB) up to eight passes, followed by annealing of selected P4 and P6 conditions at 250–350 °C for 30–60 min. Microstructural evolution, texture development, mechanical response, and physical properties were investigated using OM, SEM, EBSD, XRD, and tensile testing. ARB processing progressively refined the layered structure, reducing the initial thicknesses of brass and St14 layers from 0.8 mm to 0.6 mm to approximately 110 μm and 96 μm after P2, respectively, and further to about 8 μm and 8.2 μm after P8, respectively, accompanied by interfacial distortion and fragmentation. The tensile strength increased from 616 MPa in P2 to 802 MPa in P8, while elongation decreased from 17
