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Experimental investigation of the optimization of stilling basin with shallowwater cushion used for low Froude number energy dissipation

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Journal of Hydrodynamics 2015年第4期27卷 522-529页

作者：李连侠廖华胜刘达蒋胜银 State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Guangdong Research Institute of Water Resources and Hydropower Chengdu Municipal Engineering Design and Research Institute

energy dissipations induced by the hydraulic jump and the trajectory jet are the most widely known as the two dissipation modes at the downstream of flood discharging structures, which are often considered quite different even contradictory. However, such two energy dissipators can be used jointly and harmonically. In this paper, a new type of stilling basin with a shallow-water cushion and a triangular bottom deflector is proposed based on two different scale physical model tests of the flood discharging tunnel No.2 of Luding hydropower project. The experimental results show that the flow regime of the hydraulic jump in the presented stilling basin with bottom deflector enjoys a good and stable performance within a large range of flow rates and the energy dissipation rate is considerably high as compared to the conventional stilling basin even at a low Froude number. The results also indicate that the stilling basin with triangular bottom deflector has a better performance in improving the potential cavitation erosion according to the analysis of the pressure and the cavitation number compared to the trapezoidal one. The proposed new type of shallow-cushion stilling basin with a shallow-water cushion can be applied in similar energy dissipation projects with low Froude number and large range of flow rates.

关键词： stilling basin shallow-water cushion energy dissipation low Froude number bottom deflector

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Dry friction damping mechanism of flexible microporous metal rubber based on cell group energy dissipation mechanism

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Friction 2023年第2期11卷 259-279页

作者： Liangliang SHEN Zhiying REN Jian XU Lin PAN Youxi LIN Hongbai BAI School of Mechanical Engineering and Automation Fuzhou UniversityFuzhou 350116China Engineering Research Center for Metal Rubber Fuzhou UniversityFuzhou 350116China State Key Laboratory of Fine Chemicals Liaoning High Performance Polymer Engineering Research CenterSchool of Chemical EngineeringDalian University of TechnologyDalian 116024China Fuzhou Friction and Lubrication Industry Technology Innovation Center Fuzhou 350108China

Flexible microporous metal rubber (FMP-MR) is a high-damping material that dissipates energy by dry friction through internal spiral metal wires in contact with each other. However, the FMP-MR energy dissipation mechanism is not fully understood owing to its disordered grid interpenetrating structure. In this work, computer-aided preparation technology is used to accurately reconstruct the complex spiral network structure of FMP-MR multipoint random contact, and a cell group model with an energy dissipation mechanism is proposed to obtain the dynamic energy distribution of the contact friction in both space and time dimensions. By judging the effective contact point, a global displacement ablation phenomenon of hooked staggered porous materials is induced. The macro- and micro-equivalent frictions are introduced to effectively explain the characteristics of the strong energy dissipation in FMP-MR under fretting excitation. A real and effective damping hysteresis constitutive model is then constructed to dynamically capture the mapping relationship between the complex nonlinear topological structure effect of the materials and spatial random contact dry friction in real time. The results indicate that the contact behavior between turns of the FMP-MR wire follows a clear quasi-Gaussian distribution under an external load, forcing the topological results to change. The energy dissipation of the materials revealed peak energy consumption lagging behind the loading limit for a certain distance, which can be determined by the effective contact point and contact dry friction slip. The consistency between the quasi-static compression tests and constitutive curves of the model was quantitatively verified through residual analysis. The data demonstrated the differential behavior of the FMP-MR meso-structure to follow a phased growth law during loading with different action mechanisms in the guiding, main growth, and relaxation stages of the energy consumption displacement cur

关键词： flexible microporous metal rubber(FMP-MR) effective contact energy dissipation dry friction damping hysteresis

A five-parameter constitutive model for hysteresis shearing and energy dissipation of rock joints

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International Journal of Mining Science and Technology 2022年第4期32卷 737-746页

作者： Yikun Li Tongbin Zhao Yifei Li Yang Chen College of energy and Mining Engineering Shandong University of Science and TechnologyQingdao 266590China State Key Laboratory of Mining Disaster Prevention and Control Cofounded by Shandong Province and the Ministry of Science and Technology Shandong University of Science and TechnologyQingdao 266590China National Demonstration Center for Experimental Mining Engineering Education Shandong University of Science and TechnologyQingdao 266590China School of Civil and Transportation Engineering Qinghai Nationalities UniversityXining 810007China Shandong energy Group Co. Ltd.Jinan 250014China

Rock joints exhibit hysteresis shearing behavior and produce energy dissipation under shear cyclic loads,which however cannot be accurately depicted by existing constitutive models. This paper establishes a constitutive model for hysteresis shearing and associated energy dissipation of rock joints. Analytical expressions of the model during cyclic shearing processes are derived. Derivation of the model indicates no energy dissipation in the elastic stage. When the shear load exceeds elastic boundary, nonlinear energy dissipation takes place. Validations with experiments show that the proposed model provides good conformities with direct shear curves and hysteresis loops, and can predict the energy dissipation characteristics of rock joints under different working conditions. Compared to the constitutive models using Weibull's distribution, the proposed one is smooth at the elastic boundary and can accurately capture the maximum shear stress. Unlike the existing incremental-type models, the proposed one provides clear and direct analytical expressions for both shear stress and energy dissipation during the whole displacement domain, which is more convenient in application.

关键词： Iwan model Rock joint Cyclic shear Hysteresis energy dissipation

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Hierarchical Voronoi Structure Inspired by Cat Paw Pads Substantially Enhances Landing Impact energy dissipation

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Journal of Bionic Engineering 2024年第4期21卷 1847-1861页

作者： Da Lu Baoqing Pei Yangyang Xu Mengyuan Hu Shijia Zhang Le Zhang Xin Huang Yangwei Wang Xueqing Wu Beijing Key Laboratory for Design and Evaluation Technology of Advanced Implantable&Interventional Medical Devices Beijing Advanced Innovation Center for Biomedical EngineeringSchool of Biological Science and Medical EngineeringBeihang University100083BeijingChina National Key Laboratory of Science and Technology on Materials under Shock and Impact Beijing Institute of Technology100081BeijingChina Shenzhen Institute of Beihang University 518000ShenzhenChina

When a human lands from a high drop,there is a high risk of serious injury to the lower *** the other hand,cats can withstand jumps and falls from heights without being fatally wounded,largely due to their impact-resistant paw *** aim of the present study was to investigate the biomechanism of impact resistance in cat paw pads,propose an optimal hierarchical Voronoi structure inspired by the paw pads,and apply the structure to bionic cushioning shoes to reduce the impact force of landing for *** microstructure of cat paw pads was observed via tissue section staining,and a simulation model was reconstructed based on CT to verify and optimize the structural cushioning *** distribution pattern,wall thickness of compartments,thickness ratio of epidermis and dermis,and number of compartments in the model were changed and simulated to achieve an optimal composed structure.A bionic sole was 3D-printed,and its performance was evaluated via compression test and a jumping-landing *** results show that cat paw pads are a spherical cap structure,divided from the outside to the inside into the epidermis,dermis,and compartments,each with different cushioning capacities.A finite element simulation of different cushioning structures was conducted in a cylinder with a diameter of 20 mm and a height of 10 mm,featuring a three-layer *** optimal configuration of the three layers should have a uniform distribution with 0.3–0.5 mm wall thickness,a 1:1–2 thickness ratio of epidermis and dermis,and 100–150 compartments.A bionic sole with an optimized structure can reduce the peak impact force and delay the peak arrival *** energy absorption rate is about 4 times that of standard *** jumping 80,100,and 120 cm,the normalized ground reaction force is also reduced by 8.7%,12.6%and 15.1%compared with standard *** study provides theoretical and technical support for effective protection against human lower limb landing injuries.

关键词： Cat paw pads Hierarchical Voronoi structure Landing impact energy dissipation Bionic sole

Effect of backward-facing step heights in vegetation-step model on reducing the velocity of a tsunami inundation and increasing the energy dissipation efficiency

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Journal of Hydrodynamics 2024年第5期36卷 803-816页

作者： Wen-xin Huai Xiao-hua Zhang Dan Li Zhong-hua Yang Yi-dan Ai State Key Laboratory of Water Resources Engineering and Management Wuhan UniversityWuhan430072China

A coastal forest combined with a backward-facing step is an efficient facility to reduce tsunami damage to residential areas behind sea *** study establishes a generalized model,and experimentally explores the water level changes upstream of the vegetation-step mitigation model as well as its energy dissipation effect under different initial Froude numbers,step heights,and vegetation *** results show that the relative backwater rise increases with the growth of vegetation density,patch length and initial Froude number,representing a slowing down of the tsunami *** for energy dissipation,it is mainly caused by the additional resistance of the vegetation and the hydraulic *** the vegetation condition not only affects the energy dissipation due to stem-scale turbulence within the patch,but also changes the hydraulic jump process of water falling from the step in cooperation with the step *** a result,the energy dissipation efficiency always increases with the growth of vegetation density,vegetation patch length and step *** the criterion that the energy dissipation efficiency and its growth rate can hardly change with vegetation parameters,this study innovatively defines the threshold slope and gives the principle of judging the most cost-effective vegetation conditions at different step *** results are expected to provide an important reference for the design of composite tsunami mitigation facilities.

关键词： Vegetation-step model step height backwater rise energy dissipation

Dynamic friction energy dissipation and enhanced contrast in high frequency bimodal atomic force microscopy

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Friction 2022年第5期10卷 748-761页

作者： Xinfeng TAN Dan GUO Jianbin LUO State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

Dynamic friction occurs not only between two contact objects sliding against each other,but also between two relative sliding surfaces several nanometres *** emerging micro-and nano-mechanical systems that promise new applications in sensors or information technology may suffer or benefit from noncontact *** we demonstrate the distance-dependent friction energy dissipation between the tip and the heterogeneous polymers by the bimodal atomic force microscopy(AFM)method driving the second order flexural and the first order torsional vibration *** pull-in problem caused by the attractive force is avoided,and the friction dissipation can be imaged near the *** friction dissipation coefficient concept is proposed and three different contact states are determined from phase and energy dissipation *** contrast is enhanced in the intermediate setpoint *** work offers an effective method for directly detecting the friction dissipation and high resolution images,which overcomes the disadvantages of existing methods such as contact mode AFM or other contact friction and wear measuring instruments.

关键词： dynamic friction energy dissipation contact states image contrast bimodal atomic force microscopy(AFM)

Hysteresis Analysis on Origami energy dissipation Braces with Local Miura Units

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Acta Mechanica Solida Sinica 2024年第5期37卷 700-710页

作者： Ya Zhou Xu Li Yuting Zhang Jian Feng Jianguo Cai Key Laboratory of C and PC Structures of Ministry of Education National Prestress Engineering Research CenterSoutheast UniversityNanjing211189China Shenzhen Research Institute Southeast UniversityShenzhen518071China

A local design scheme for origami energy dissipation braces was proposed by combining local Miura units at both ends and a straight segment in the *** design was implemented to address the issue of uneven axial stiffness observed in global origami *** and locally designed origami braces were simulated and compared under cyclic loading to validate the advantages of the proposed design scheme in terms of hysteretic ***,an analysis was conducted on the designed braces with varying straight segment lengths,geometric angles,and origami plate thicknesses for *** indicate that the local design significantly increases the tensile bearing load,enhances the anti-buckling capability,and improves the energy dissipation performance compared to the global *** positive impact on bearing capacity and energy dissipation performance was observed with increased straight segment length,geometric angles,and origami plate ***,excessively large parameter values result in brace buckling under compression,diminishing energy dissipation capacity.

关键词： Origami brace Local design energy dissipation Hysteretic property

Nonlinear aspects of energy dissipation in wood-panel joints Sara Casciati

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Earthquake Engineering and Engineering Vibration 2007年第4期6卷 259-268页

作者： Sara Casciati ASTRA Dept. School of Architecture University of Catania at Siracusa 96100 Siracusa Italy

The joints connecting vertical and horizontal elements are the ＂weak link＂ in structural systems assembled from wood panels. If they are too weak, local failures may occur, resulting in performance that is significantly below expectations. If they are too resistant, the joints may be unable to dissipate energy during vibrations, thus possibly initiating a fast progressive failure. This paper re-processes and re-elaborates the results of shaking table tests previously carried out by the author and other co-workers. The goal is to assess the feasibility of a joint which is able to dissipate energy during vibration, without degrading the connection performance.

关键词： dynamic excitation energy dissipation wood panels joint monitoring system shaking table tests

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Dynamic Mechanical Properties and energy dissipation Characteristics of Frozen Soil Under Passive Confined Pressure

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Acta Mechanica Solida Sinica 2021年第2期34卷 184-203页

作者： Jinxuan Jia Huaiping Tang Huijian Chen Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Impact compression tests on frozen soil samples with different freezing temperatures and subjected to passive confined pressure were performed using a split Hopkinson pressure bar at different loading strain *** three-dimensional stress-strain curves of the frozen soil samples under the corresponding conditions were *** experimental results showed that,when the frozen soil was loaded to its elastic limit,shear failure occurred,the bearing capacity of pore ice was lost,and the thawed soil functioned as the main stress-bearing ***,the capacity of frozen soil to withstand hydrostatic pressure continued to *** dynamic mechanical properties of the frozen soil under passive confined pressure were observed to be strongly related to the loading strain rate and freezing *** the loading strain rate increased,the secant modulus,elastic modulus,and strength(including the shear strength)of the frozen soil increased,whereas its Poisson^ratio and coefficient of lateral pressure *** the freezing temperature decreased,the secant modulus,elastic modulus,and shear strength of the frozen soil increased;however,its Poisson5s ratio and coefficient of lateral pressure *** the frozen soil was subjected to impact loading under passive confined pressure,energy dissipation occurred due to plastic deformation,mesoscopic damage evolution,and ice-water phase *** shear failure occurred,the absorption energy per unit volume of frozen soil increased as the freezing temperature decreased and the loading strain rate increased.

关键词： Frozen soil Split Hopkinson pressure bar Passive confined pressure Dynamic mechanical properties energy dissipation