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Modeling the Interaction between Vacancies and Grain Boundaries during Ductile Fracture

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Computer Modeling in engineering & Sciences 2024年第8期140卷 2019-2034页

作者： Mingjian Li Ping Yang Pengyang Zhao department of engineering Mechanics School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

The experimental results in previous studies have indicated that during the ductile fracture of pure metals,vacancies aggregate and form voids at grain ***,the physical mechanism underlying this phenomenon remains not fully *** study derives the equilibrium distribution of vacancies analytically by following thermodynamics and the micromechanics of crystal *** derivation suggests that vacancies cluster in regions under hydrostatic compression to minimize the elastic strain ***,a finite element model is developed for examining more general scenarios of interaction between vacancies and grain *** model is first verified and validated through comparison with some available analytical solutions,demonstrating consistency between finite element simulation results and analytical solutions within a specified numerical accuracy.A systematic numerical study is then conducted to investigate the mechanism that might govern the micromechanical interaction between grain boundaries and the profuse vacancies typically generated during plastic *** simulation results indicate that the reduction in total elastic strain energy can indeed drive vacancies toward grain boundaries,potentially facilitating void nucleation in ductile fracture.

关键词： Ductile fracture vacancy grain boundary micromechanical finite element method

Experimental and Three-Dimensional Numerical Simulation of Phenomena Induced by Submerged Oblique Jet Scouring

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Fluid Dynamics & Materials Processing 2024年第8期20卷 1799-1821页

作者： Hao Chen Xianbin Teng Faxin Zhu Zhibin Zhang Jie Wang School of naval architecture and Maritime Zhejiang Ocean UniversityZhoushan316022China School of marine engineering Guangzhou Maritime UniversityGuangzhou510725China

Scouring experiments were conducted using a three-dimensional laser scanning technology for angles of the jet spanning the interval from 0°to 30°,and the characteristics of the scour hole in equilibrium conditions were investigated *** results indicate that the optimal scouring effects occur when the jet angle is in the ranges between 15°and 20°.Moreover,the dimensionless profiles of the scour hole exhibit a high degree of similarity at different jet *** simulations conducted using the Flow-3D software to investigate the bed shear stress along the jet impingement surface have shown that this stress is influenced by both the resultant force and the jet impingement surface *** reaches its maximum value when the jet is vertical,decreases rapidly as the jet starts to tilt,then increases slightly,and decreases again significantly when the angle exceeds 20°.

关键词： Submerged jet jet angle experimental study numerical simulation bed shear stress

Rapid validation of water wave metamaterials in a desktop-scale wave measurement system

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International Journal of Fluid Engineering

International Journal of Fluid engineering 2024年第1期 31-39页

作者： Yi Huang Saishuai Dai Zhi-Ming Yuan Laibing Jia department of naval architecture Ocean and Marine Engineering University of Strathclyde

Metamaterials have a unique ability to manipulate wave phenomena beyond their natural capabilities, and they have shown great promise in electromagnetic and acoustic wave control. However, their exploration in hydrodynamics remains limited. This article introduces a novel desktop-scale wave measurement system, specifically designed for the rapid prototyping and validation of water wave metamaterials. By utilizing 3D printing, the system accelerates the transition from theoretical designs to practical testing, offering a versatile and user-friendly platform. This is further enhanced by a synchronized stereo-camera setup and advanced data processing algorithms, enabling precise measurement and reconstruction of water wave behavior. Our experimental results demonstrate the system's effectiveness in capturing intricate interactions between engineered structures and water waves. This significantly advances rapid prototyping for water wave metamaterial research, underscoring the system's potential to catalyze further innovation in this emerging field.

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Constitutive Behavior of the Interface between UHPC and Steel Plate without Shear Connector:From Experimental to Numerical Study

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Computer Modeling in engineering & Sciences 2024年第8期140卷 1863-1888页

作者： Zihan Wang Boshan Zhang Hui Wang Qing Ai Xingchun Huang School of naval architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China department of Bridge engineering Tongji UniversityShanghai200092China

The application of ultra-high performance concrete(UHPC)as a covering layer for steel bridge decks has gained widespread *** employing a connection without a shear connector between the steel plate and UHPC,namely,the sandblasted interface and the epoxy adhesive with sprinkled basalt aggregate interface,the installation cannot only be simplified but also the stress concentration resulting from the welded shear connectors can be *** study develops constitutive models for these two interfaces without shear connectors,based on the interfacial pull-off and push-out *** validation,three-point bending tests on the steel-UHPC composite plates are *** results indicated that the proposed bilinear traction-separation model for the sandblasted interface and the trapezoidal traction-separation model for the epoxy adhesive with sprinkled basalt aggregate interface can generally calibrate the interfacial ***,the utilization of the experimentally determined pure shear strength underestimates the load-carrying capacity of the composite plates in the case of three-point bending *** recalling the Mohr-Coulomb criterion,this underestimation is attributed to the enhancement of the interface shear strength by the presence of normal stress.

关键词： Cohesive zone model interfacial behavior finite element simulation UHPC steel plate

Development of deep-learning-based autonomous agents for low-speed maneuvering in Unity

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Journal of Intelligent and Connected Vehicles

Journal of Intelligent and Connected Vehicles 2024年第3期7卷 229-244页

作者： Riccardo Berta Luca Lazzaroni Alessio Capello Marianna Cossu Luca Forneris Alessandro Pighetti Francesco Bellotti Electrical Electronics and Telecommunication Engineering and Naval Architecture Department(DITEN)University of GenoaGenoa 16145Italy

This study provides a systematic analysis of the resource-consuming training of deep reinforcement-learning (DRL) agents for simulated low-speed automated driving (AD). In Unity, this study established two case studies: garage parking and navigating an obstacle-dense area. Our analysis involves training a path-planning agent with real-time-only sensor information. This study addresses research questions insufficiently covered in the literature, exploring curriculum learning (CL), agent generalization (knowledge transfer), computation distribution (CPU vs. GPU), and mapless navigation. CL proved necessary for the garage scenario and beneficial for obstacle avoidance. It involved adjustments at different stages, including terminal conditions, environment complexity, and reward function hyperparameters, guided by their evolution in multiple training attempts. Fine-tuning the simulation tick and decision period parameters was crucial for effective training. The abstraction of high-level concepts (e.g., obstacle avoidance) necessitates training the agent in sufficiently complex environments in terms of the number of obstacles. While blogs and forums discuss training machine learning models in Unity, a lack of scientific articles on DRL agents for AD persists. However, since agent development requires considerable training time and difficult procedures, there is a growing need to support such research through scientific means. In addition to our findings, we contribute to the R&D community by providing our environment with open sources.

关键词： automated driving autonomous agents deep reinforcement learning curriculum learning modeling and simulation

Jellyfish-inspired alginate composite hydrogel filter prepared by macro-micro double bionic strategy for efficient water purification

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Frontiers of Environmental Science & engineering 2024年第4期18卷 141-157页

作者： Huiting Peng Yan Chen Jiaopan Lin Chelsea Benally Mohamed Gamal El-Din Junkai Gao School of naval architecture and marinetime Zhejiang Ocean UniversityZhoushan 316022China department of Civil and Environmental engineering University of AlbertaEdmontonAB T6G 1H9Canada

Recently,research on hydrogel materials with a porous structure and superior water absorption capabilities significantly ***,the hydrogel under gravity-driven separation conditions often exhibit an unstable pore structure,poor mechanical properties,and limited *** this end,this work presents a novel approach that combines a macro-micro double bionic strategy with a triple crosslinking method to develop a multifunctional alginate composite hydrogel filter(2%-SA-κCG-PVA-Ca^(2+),2%-SKP-Ca^(2+)for short)with a stable pore structure and superior mechanical properties,which possessed an umbrella-shaped structure resembling that of *** 2%-SKPCa^(2+)filter was synthesized using polyvinyl alcohol(PVA)as a stable structure-directing agent,and sodium alginate(SA)andκ-carrageenan(κ-CG)as polymer *** distinctive umbrellashaped hydrogel of 2%-SKP-Ca^(2+)filter,formed through the triple crosslinking method,overcomes the limitations of unstable pore structure and poor durability seen in hydrogels prepared by traditional crosslinking ***,the utilization of the 2%-SKP-Ca^(2+)filter in water treatment demonstrates its good selective permeability,excellent resistance to fouling,and extended longevity,which enables it to simultaneously achieve the multifunctional water purification and the coating of multi-substrate anti-fouling ***,not only does this research provide an efficient,multifunctional,highly pollution-resistant preparation method for designing a new filter,but it also confirms the application prospect of the macro-micro dual bionic strategy developed in this study in complex water treatment.

关键词： Triple crosslinking method Alginate Umbrella-shaped Jellyfish Water purification

Experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering boundary effect

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Journal of Rock Mechanics and Geotechnical engineering 2024年第3期16卷 1072-1084页

作者： Xuwei Wang Yeshuang Xu State Key Laboratory of Ocean engineering School of Naval ArchitectureOceanand Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China Shanghai Key Laboratory for Digital Maintenance of Buildings and Infrastructure Department of Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

The boundary condition is a crucial factor affecting the permeability variation due to *** experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering the boundary effect is conducted,where the hydraulic head difference(DH)varies,and the boundary includes non-loss and soil-loss *** samples are filled into seven soil storerooms connected in *** evaluation,the variation in content of fine sand(ΔR_(f))and the hydraulic conductivity of soils in each storeroom(C_(i))are *** the non-loss test,the soil sample filling area is divided into runoff,transited,and accumulated areas according to the negative or positive ΔR_(f) values.ΔR_(f) increases from negative to positive along the seepage path,and Ci decreases from runoff area to transited area and then rebounds in accumulated *** the soil-loss test,all soil sample filling areas belong to the runoff area,where the gentle-loss,strengthened-loss,and alleviated-loss parts are further divided.ΔR_(f) decreases from the gentle-loss part to the strengthened-loss part and then rebounds in the alleviated-loss part,and C_(i) increases and then decreases along the seepage *** relationship between ΔR_(f) and Ci is different with the boundary *** exponentially decreases with ΔR_(f) in the non-loss test and increases with ΔR_(f) generally in the soil-loss test.

关键词： Suffusion Permeability Experimental investigation Boundary effect Horizontal seepage

不同装载条件下小型渔船参数横摇的非定常RANS CFD仿真

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哈尔滨工程大学学报（英文版） 2024年第2期23卷 327-351页

作者： Muhammad Iqbal Momchil Terziev Tahsin Tezdogan Atilla Incecik department of naval architecture Oceanand Marine EngineeringUniversity of StrathclydeGlasgow-G40LZUK department of naval architecture Diponegoro UniversitySemarang-50275Indonesia department of Civil Maritime and Environmental EngineeringUniversity of SouthamptonSouthampton-SO167QFUK

Fishing boats have unique features that make them prone to changing loading *** the boat leaves the port,the empty fish tank gradually fills up during fishing operations which may result in parametric roll(PR).This dangerous phenomenon that can lead to *** present study aims to understand better the behaviour of parametric roll in fishing boats and its relation to changing loading *** study considers the effects of displacement and the GM/KM ratio on parametric roll,as well as the longitudinal flare distribution at the *** assessments to detect the parametric roll occurrence in early stage were carried out by using the level 1 assessment of parametric roll based on the Second Generation of Intact Stability criteria(SGIS)from International maritime Organisation(IMO)and the Susceptibility criteria of Parametric roll from the American Bureau of Shipping(ABS).Then,the CFD method is used to predict the amplitude of the parametric roll *** results provide important insights to fishing vessel operators on how to manage loading conditions to maintain stability and avoid hazardous *** following the guidelines outlined in this study,fishing boats can operate more safely and efficiently,reducing the risk of accidents and improving the overall sustainability of the fishing industry.

关键词： Small fishing boat Parametric roll URANS-CFD KRISO Container Ship(KCS) Stability in waves

The Optimization Design of the Nozzle Section for theWater Jet Propulsion System Applied in Jet Skis

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Computer Modeling in engineering & Sciences 2024年第3期138卷 2277-2304页

作者： Cheng-Yeh Li Jui-Hsiang Kao department of Systems engineering and naval architecture Taiwan Ocean UniversityKeelungTaiwanChina

The performance of a water jet propulsion system is related to the inlet duct,rotor,stator,and ***,the flow inlet design must fit the bottom line of the hull,and the design of the inlet duct is often limited by stern *** entire section,from the rotor to the nozzle through the stator,must be designed based on system integration in that the individual performance of these three components will influence each ***,the section from the rotor to the nozzle significantly impacts the performance of a water jet propulsion *** study focused on nozzle design and established referable analysis results to facilitate subsequent integrated studies on the design parameters regarding nozzle *** existing studies concentrate on discussions on rotor design and the tip leakage flow of rotors or have replaced the existing complex computational domain with a simple flow ***,research has yet to implement an integrated,optimal design of the section from the rotor to the *** the above,our program conducted preliminary research on this system integration design issue,discussed the optimal nozzle for this section in-depth,and proposed design suggestions based on the *** program used an existing model as the design *** study referred to the actual trial data as the design conditions for the proposed *** prior references’simple flow field form,this study added a jet ski geometry and free surface to the computational *** the linear hull shape was considered,the inflow in the inlet duct would be closer to the actual *** on the numerical calculation result,this study recommends that the optimal nozzle outlet area should be 37%of the inlet area and that the nozzle contour should be ***,for the pump head,static pressure had a more significant impact than dynamic pressure.

关键词： Water jet propulsion system rotor nozzle outlet area nozzle contour