Search Results (644)

The study establishes key patterns in the influence of pre-applied impact-oscillatory loading (IOL) of varying intensity—realizing dynamic non-equilibrium processes (DNP)—in liquid nitrogen on the mechanical properties and structural state of stainless steel X10CrNi18-8. Static tensile deformation was investigated at room temperature following impulsive strain levels of ε_imp = 0.06–2.69%. A wave-like mechanical response of the steel to DNP was observed within this ε_imp range, most pronounced at ε_imp = 0.11% and ε_imp = 2.69%. After DNP at ε_imp = 0.11%, despite a maximum increase in ultimate strength by 5.25%, the relative elongation of the specimen increased to 10.3%. The scatter in ultimate tensile strength specimens across all loading regimes was within 6.38%, while the variation in ductility reached up to 21.25%. In contrast, after ε_imp = 2.69%, the stress–strain diagram resembled that of the steel in its initial state. Metallophysical investigations and X-ray diffraction analysis were conducted to explain the observed effects. At ε_imp > 2.7%, the high-strength but low-ductility X10CrNi18-8 steel undergoes brittle failure under impulsive loading. At the same time, the total fraction of the more brittle martensitic phase in the steel microstructure reaches approximately 22%. Full article

We investigated the impacts of a rapidly changing hydrometeorological regime on coastal erosion in the shallow, seasonally freezing Sea of Azov from 2000 to 2025. Our comparative approach integrated numerical modeling (SWAN), satellite remote sensing, and long-term field observations at two high-erosion sites: the Northern Site in Taganrog Bay and the Southern Site at the open sea boundary. The results demonstrate that coastal erosion is governed by complex, site-specific interactions rather than direct regional climatic trends. A major regime shift characterized by declining fast ice and increasing storm activity during the extended warm season has amplified coastal vulnerability, particularly after 2010. Despite high long-term average erosion rates at both sites, 1.1 to 1.6 m/year in the north and 1.5 to 1.8 m/year in the south, their annual erosion patterns were largely non-synchronous. The Northern Site is controlled by geological structure and surge phenomena, with peak rates reaching 8.5 m/year, while the Southern Site is governed by storm waves and extreme surges, enduring dynamic loads up to 10.0 tf/m². These results provide complex interaction nature of coastal processes and hydrometeorological components and its response to climate change in periodically freezing sea. These findings are vital for improving vulnerability models and underscore the necessity of site-specific hazard assessments for seasonally freezing coasts under a warming climate. Full article

During drill-and-blast construction, complex and variable rock masses are frequently encountered. Owing to the transient nature of the explosion process and the randomness of crack propagation, the response of different rock masses to explosive loading is highly intricate. This study primarily investigates the dynamic response of rock masses with varying strengths under two different charge configurations. First, four cement mortar specimens of differing strengths were prepared then subjected to general blasting and slit charge blasting, respectively. High-speed cameras and digital image correlation techniques were employed to capture and analyse stress wave propagation and crack propagation during detonation. Fractal dimension analysis was subsequently employed to quantify and compare the extent of damage in the specimens. Findings indicate that rock strength influences stress wave attenuation patterns: lower-strength rocks exhibit higher peak strains but faster decay rates. Crack propagation velocity was calculated by deploying monitoring points along fracture paths and defining fracture initiation thresholds. Higher rock strength correlates with both peak and average crack propagation velocities. Slit charge blasting effectively optimizes damage distribution, concentrating it within the intended directions while reducing chaotic fracturing. These findings provide scientific justification for blasting operations in complex rock formations. Full article

Reinforced concrete shear wall structures (RCSWs) are commonly used as explosion-resistant chambers for storing hazardous chemical materials and housing high-pressure reaction equipment, serving to isolate blast waves and prevent chain reactions. In this study, full-scale experiments and numerical simulations were conducted to investigate the blast resistance of RC shear wall protective structures subjected to internal explosions. A full-scale RC shear wall structure measuring 9.7 m × 8 m × 6.95 m with a wall thickness of 0.8 m was constructed, and an internal detonation equivalent to 200 kg of TNT was initiated to simulate the extreme loading conditions that may occur in explosion control chambers. Based on experimental data analysis and numerical simulation results, the damage mechanisms and dynamic response characteristics of the structure were clarified. The results indicate that under internal explosions, severe damage first occurs at the wall–joint regions, primarily exhibiting through-thickness shear cracking near the supports. The structural damage process can be divided into two stages: local response and global response. Using validated finite element models, a parametric study was carried out to determine the influence of TNT charge weight and reinforcement configuration on the structural dynamic response. The findings of this research provide theoretical references for the design and strengthening of blast-resistant structures. Full article

Buried pipelines represent critical lifeline infrastructure whose seismic performance is governed by complex soil–structure interaction mechanisms. In this study, a process-based numerical framework is developed to evaluate the pseudo-static seismic response of buried steel pipelines installed within a trench. A comprehensive parametric analysis is conducted using the finite-element software Rocscience RS2 (version 11.027) to examine the influence of burial depth, pipeline diameter, slope angle, groundwater level, soil type, and permanent ground deformation. The seismic loading was represented using a pseudo-static horizontal acceleration, which approximates permanent ground deformation rather than full dynamic wave propagation. Therefore, the results represent simplified lateral seismic demand and not the complete dynamic soil–structure interaction response. To verify the reliability of the 2D plane–strain formulation, a representative configuration is re-simulated using the fully three-dimensional platform Rocscience RS3. The comparison demonstrates excellent agreement in shear forces, horizontal displacements, and cross-sectional distortion patterns, confirming that RS2 accurately reproduces the dominant load-transfer and deformation mechanisms observed in three-dimensional (3D) models. Results show that deeper burial and stiffer soils increase shear demand, while higher groundwater levels and larger permanent ground deformation intensify lateral displacement and cross-sectional distortion. The combined 2D–3D evaluation establishes a validated computational process for predicting the behavior of buried pipelines under a pseudo-static lateral load and provides a robust basis for engineering design and hazard mitigation. The findings contribute to improving the seismic resilience of lifeline infrastructure and offer a validated framework for future numerical investigations of soil–pipeline interaction. Full article

With the rapid advancement of offshore wind power, structural vibration induced by multi-source excitations in complex marine environments is a critical concern. This study developed a multi-degree-of-freedom (MDOF) dynamic model of an offshore wind turbine using a lumped mass approach, which was then reduced to a first-order linear system to improve frequency-domain analysis and optimization efficiency. Given the non-stationary, broadband nature of wind and wave loads, a band-pass filtering technique was applied to extract dominant frequency components, enabling linear modeling of excitations within primary modal ranges. The displacement response spectrum, derived via system transfer functions, served as the objective function for optimizing tuned mass damper (TMD) parameters. Both single TMD and multiple TMD (MTMD) strategies were designed and compared. A hierarchical particle swarm optimization (H-PSO) algorithm was proposed for MTMD tuning, using the optimized single TMD as an initial guess to enhance convergence and stability in high-dimensional spaces. The results showed that the frequency-domain optimization framework achieved a balance between accuracy and computational efficiency, significantly reducing structural responses in dominant modes and demonstrating strong potential for practical engineering applications. Full article

Large-scale vertical-axis wind turbines (VAWTs) have potential applications in the oceanic environment due to their ease of installation and maintenance. Most research has focused on the aerodynamic enhancement of VAWTs; however, controlling the structural vibration of a VAWT supported by a floating platform has seldom been addressed in previous work. In this paper, four optimized structures are proposed to passively mitigate the dynamic response of a 5 MW floating VAWT subjected to high wind speeds (25 m/s) and combined platform motions (pitch and surge). Computational fluid dynamics (CFD) was used to calculate the wind loads, while the wave loads were represented by accelerations applied to the bottom of the turbine. The dynamic responses of the original and optimized models were comprehensively compared. The results show that the optimized models effectively reduce vibration by shifting the blade swing and flapping modes to higher frequencies. Specifically, the model incorporating brace struts, cables, and spring-damping units demonstrates the highest damping efficiency, reaching 96.83% for the y-direction displacement at the blade tip. Full article

Although the dynamic response of orthotropic materials under uniaxial impact loading has been extensively studied, their behavior under multiaxial stress states, which more accurately represent real-world blast and impact scenarios, has received limited attention. To address this gap, this study employed a self-developed biaxial impact testing apparatus to systematically investigate the dynamic mechanical behavior of beech wood, a typical orthotropic material, under three biaxial loading configurations: radial-tangential, radial-longitudinal, and tangential-longitudinal. By combining theoretical derivation with experimental data, it systematically examines stress wave propagation characteristics, strain rate effects, and anisotropy evolution under different loading paths. The results reveal that beech wood exhibits significantly distinct dynamic responses along different material orientations, with a consistent strength hierarchy: longitudinal > radial > tangential. Biaxial loading notably enhances the equivalent stress–strain response and alters the deformation mechanisms and energy absorption behavior. Furthermore, lateral confinement and multiaxial stress coupling are identified as critical factors influencing the dynamic performance. This study provides the first systematic revelation of the strain rate strengthening mechanisms and wave propagation characteristics of orthotropic materials from the perspective of multiaxial dynamic loading, thereby offering theoretical and experimental foundations for developing advanced dynamic constitutive models suitable for complex impact conditions. These findings provide important guidance for the design and evaluation of lightweight impact-resistant structures in fields such as aerospace and protective engineering. Full article

As a new kind of large observation platform, the three-anchor buoy system can effectively realize multifunctional ocean observation, e.g., ocean profiling and autonomous underwater vehicle docking. In order to understand effects of different anchor chain arrangements on the motion response of the three-anchor buoy system under the coupling effect of wind, wave, and current loads, a hydrodynamic model of the buoy system was developed. Wave-period-dependent characteristics of added mass, radiation damping, and the motion response amplitude operator (RAO) were analyzed to derive their response curves; the effects of adding additional viscous damping on RAO performance were investigated. Subsequently, frequency domain and time domain analyses were conducted on five three-anchor buoy systems with distinct anchor chain arrangements to investigate the variation patterns of 6-DOF motion response amplitudes, top-chain tension characteristics, and submarine anchor chain length alterations under combined wind, wave, and current loading conditions. The results show that under the same environmental load, when the three anchor chains are evenly distributed at 120°, the 6-DOF motion response amplitude of the buoy system is the smallest, the top-chain tension and the submarine anchor chain length are more in line with the design requirements, and the comprehensive performance is better. Full article

Marine risers, critical structures connecting underwater production systems and surface floating platforms, stand freely in water and endure extremely complex marine environmental loads. To meet the multi-parameter observation demand for their overall state, a fiber-optic sensing-based marine riser buoy observation system was developed. Unlike traditional point-type and offline monitoring systems, it integrates marine buoys with sensing submarine cables to achieve long-term real-time online monitoring of risers’ overall state via fiber-optic sensing technology. Comprising two main modules (buoy monitoring module and fiber-optic sensing module), the buoy’s stability was verified through theoretical derivation, simulation, and stability curve plotting. Frequency domain analysis of buoy loads and motion responses, along with calculation of motion response amplitude operators (RAOs) at various incident angles, showed the system avoids wave periods in the South China Sea (no resonance), ensuring structural safety for offshore operations. A 7-day marine test of the prototype was conducted in Yazhou Bay, Hainan Province, to monitor real-time temperature and strain data of the riser in the test sea area. The sensing submarine cable accurately responded to temperature changes at different depths with high stability and precision; using the Frenet-based 3D curve reconstruction algorithm, pipeline shape was inverted from the monitored strain data, enabling real-time pipeline monitoring. During the test, the buoy and fiber-optic sensing module operated stably. This marine test confirms the buoy observation system’s reasonable design parameters and feasible scheme, applicable to temperature and deformation monitoring of marine risers. Full article

Fatigue cracks in highly stressed regions of marine structures, caused primarily due to wave loading, are critical life-limiting factors that can lead to structural failure. Structural Health Monitoring (SHM) systems offer the ability to remotely monitor damage progression during its initial phases, enabling failure prevention. One diagnostic approach utilizes the strain redistribution in the vicinity of the crack tip, captured by sensor readings, to inversely calculate the corresponding crack length. This work addresses the challenge of accurately calculating the crack length under variable sources of uncertainty by employing the statistical framework of Maximum Likelihood Estimation (MLE). The method is demonstrated on a simplified test geometry using simulated strain data, registered at locations where structural response sensors may be placed. This approach enables the integration of multiple strain features at modest computational cost, facilitating the assessment of different sensor placement strategies under realistic noise conditions. Full article

A variety of Offshore Floating Photovoltaics (OFPVs) applications rely on the capacity of their floating support structures displacing in the shape of surface waves to reduce extreme wave-induced loads exerted on their floating-mooring system. This wave-adaptive displacement behaviour is typically realized through two principal design approaches, either by employing slender and continuously deformable structures composed of highly elastic materials or by decomposing the structure into multiple floating rigid pontoons interconnected via flexible connectors. The hydrodynamic behaviour of these structures is commonly analyzed in the literature using potential flow theory, to characterize wave loading, whereas in order to deploy such OFPV prototypes in realistic marine environments, a high-fidelity numerical fluid–structure interaction model is required. Thus, a versatile three-dimensional numerical scheme is herein presented that is capable of handling non-linear fluid-flexible structure interactions for Very Flexible Floating Structures (VFFSs): Multibody Dynamics (MBD) for modularized floating structures and floating-mooring line interactions. In the present study, this is achieved by employing the Smoothed Particles Hydrodynamics (SPH) fluid model of DualSPHysics, coupled both with the MBD module of Project Chrono and the MoorDyn+ lumped-mass mooring model. The SPH-MBD coupling enables modelling of large and geometrically non-linear displacements of VFFS within an Applied Element Method (AEM) plate formulation, as well as rigid body dynamics of modularized configurations. Meanwhile, the SPH-MoorDyn+ captures the fully coupled three-dimensional response of floating-mooring and floating-floating dynamics, as it is employed to model both moorings and flexible interconnectors between bodies. The coupled SPH-based numerical scheme is herein validated against physical experiments, capturing the hydroelastic response of VFFS, rigid body hydrodynamics, mooring line dynamics, and flexible connector behaviour under wave loading. The demonstrated numerical methodology represents the first validated Computational Fluid Dynamics (CFD) application of moored VFFS in three-dimensional domains, while its robustness is further confirmed using modular floating systems, enabling OFPV engineers to comparatively assess these two types of wave-adaptive designs in a unified numerical framework. Full article

This study addresses the system identification of a small autonomous surface vehicle (ASV) under moored conditions using Hankel dynamic mode decomposition with control (HDMDc) and its Bayesian extension (BHDMDc). Experiments were carried out on a Codevintec CK-14e ASV in the CNR-INM towing tank, under both irregular and regular head wave conditions. The ASV under investigation features a recessed moon pool, which induces nonlinear responses due to sloshing, thereby increasing the modeling challenge. Data-driven reduced-order models were built from measurements of vessel motions and mooring loads. The HDMDc framework provided accurate deterministic predictions of vessel dynamics, while the Bayesian formulation enabled uncertainty-aware characterization of the model response by accounting for variability in hyperparameter selection. Validation against experimental data demonstrated that both HDMDc and BHDMDc can predict the vessel’s response under unseen regular and irregular wave excitations. In conclusion, this study shows that HDMDc-based ROMs are a viable data-driven alternative for system identification, demonstrating for the first time their generalization capability for an unseen sea condition different from the training set, achieving high accuracy in reproducing the vessel dynamics. Full article

To investigate the relationship between the three-dimensional size of a structure and the impact of the traveling wave effect, models derived from an orthographic quadrangle flat grid based on a practical engineering case were established and validated. The plane size (ranging from 30 m to 90 m), height (ranging from 0 m to 9 m), and space of the supporting columns (ranging from 6 m to 12 m for peripheral columns and from 18 m to 24 m for internal columns) were changed. The time history method was used to perform a statistical analysis of the proportion and distribution of special bars and to investigate their seismic response under multiple-support excitation along the length of the structure and single excitation. The results show that an increase in the structural length and decreases in the structural span and the height and distance of the columns lead to an increase in the traveling wave effect, with special bars spreading from the supports to the peripheries and from the edge to the middle along the span. It is concluded that the traveling wave effect can be regarded as an additional dynamic load according to the excitation time differences among supporting columns along the propagation direction of the seismic wave, which spreads from supports to peripheries in a manner similar to energy radiation. The smaller the apparent wave velocity, the larger the time difference, the larger the additional dynamic load, and the larger the degree and range of the traveling wave effect. Increasing the plane and the height and space of the supporting columns to certain sizes will lead to a decrease in the traveling wave effect due to its limited range. Full article

Surface-acoustic-wave (SAW) sensors with Langasite (LGS) substrate have broad prospects in the field of wireless passive temperature sensing in harsh environments. However, there are still challenges in terms of accuracy regarding the material temperature coefficient of LGS and the temperature simulation of heavy mass load electrodes. This paper presents a method for fitting the material temperature coefficient of LGS based on a combination of finite element simulation (FEM) and measured data. Eleven different cuts of LGS SAW resonators were fabricated, and the frequency response of each cut device at 30–800 °C was obtained through experiments. Some of the data were used in the training dataset and the material temperature coefficient of LGS was obtained through comsol simulation fitting. The remaining data were used as a test dataset to verify the accuracy of the results. The results show that the material coefficient obtained using this method has good accuracy in the frequency prediction of thick electrode LGS SAW sensors at different temperatures with different cuts. Full article