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Rock Dynamic Crack Propagation Behaviour and Determination Method with Improved Single Cleavage Semi-circle Specimen Under impact loads

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Acta Mechanica Solida Sinica 2020年第6期33卷 793-811页

作者： Fei Wang Meng Wang Zheming Zhu Jianhui Deng Mohaddeseh Mousavi Nezhad Hao Qiu Peng Ying Failure Mechanics&Engineering Disaster Prevention and Mitigation Key Laboratory of Sichuan ProvinceSichuan UniversityChengdu 610065China Key Laboratory of Deep Underground Science and Engineering(Sichuan University) Ministry of EducationChengdu 610065China School of Engineering The University of WarwickCoventry CV47ALUK

This paper studied the rock dynamic fracture propagation under impact loads elaborately with a determination method proposed to calculate crack propagation dynamic stress intensity factor(DSIF).By utilizing the split-Hopkinson pressure bar,the impact experiments with an improved single cleavage semi-circle(ISCSC)specimen were conducted to illuminate the dynamic crack propagation ***,the fracture characteristics and crack propagation velocity were obtained by the crack propagation *** experiments with a numerical approach,the crack propagation dynamic stress intensity factors were calculated by an experimental—numerical method with fractal ***,a finite difference model was developed based on the tensile fracture softening damage *** the analysis of numerical and experimental results,the crack propagation behaviour and mechanism of crack arrest were discussed *** results demonstrate that the novel ISCSC specimen shows a definite advantage in determining crack propagation and arrest ***,the crack arrest DSIF is larger than the average propagation DSIF with a sharp ***,the numerical simulation results which agree well with the actual crack propagation illustrate that the crack arrest should be dominated by the compressive stress perpendicular to the crack path,and there were several arrest pauses existing in the transitory crack arrest process.

关键词： impact loads Crack propagation Crack arrest Numerical simulation Fractal method Dynamic stress intensity factor

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Image-based numerical study of three-dimensional meso-structure effects on damage and failure of heterogeneous coal-rock under dynamic impact loads

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Particuology 2020年第4期18卷 132-141页

作者： Kehong Zheng Bingjing Qiu Zhenyu Wang Xuefeng Li Jianping Li Kuidong Gao College of Civil Engineering and Architecture Zhejiang UniversityHangzhou 310058China School of Energy and Mechanical Engineering Nanjing Normal UniversityNanjing 210000China College of Mechanical and Electrical Engineering China University of Mining and Technology Xuzhou 221116China College of Mechanical&Electrical Engineering Shandong University of Science&Technology Qingdao 266000China

This paper proposes a numerical three-dimensional(3D)mesoscopic approach based on the discrete element method combined with X-ray computed tomography(XCT)images to characterize the dynamic impact behavior of heterogeneous coal-rock(HCR).The dynamic impact loading in three directions was modelled to investigate the effects of the 3D meso-structure on the failure patterns and fracture mechanism,with different impact *** XCT image-based discrete element model of HCR was calibrated through appropriate standard uniaxial compression *** simulations were carried out to investigate how the breakage behaviors are affected by different loading directions with different impact *** loading direction,input energy,and spatial distribution of the mineral phase had a remarkable influence on the failure patterns and load-carrying *** shape of the gangue phase and the approximate location of the gangue interfaces are key parameters to consider when investigating the failure patterns and fracture mechanism of heterogeneous rock *** damage and fracture tended to propagate from the surfaces to the HCR *** gangue phase area contacting the loading wall,growth direction of the strong gangue interfaces,and loading directions greatly influenced the failure patterns of the heterogeneous rock materials.

关键词： Heterogeneous coal-rock impact loads X-ray computed tomography(XCT) 3D image-based discrete element modelling Failure pattern

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Performances of a new sustainable and durable dry beam-column joints under cyclic and impact loads

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Science China(Technological Sciences) 2023年第2期66卷 282-300页

作者： HAO Hong NGO Tuan T. PHAM Thong M. LI HuaWei Center for Infrastructural Monitoring and Protection School of Civil and Mechanical EngineeringCurtin UniversityBentley WA 6102Australia The Faculty of Engineering and Technology Quy Nhon UniversityBinh Dinh 590000Viet Nam Guangzhou University-Curtin University Joint Research Center for Structural Monitoring and Protection against Multi-Dynamic Hazards School of Civil EngineeringGuangzhou UniversityGuangzhou 510006China

This study investigated the performances of a new type of precast beam-column joint subjected to earthquake and impact *** sustainability and durability considerations,new materials such as corrosion-resistant fibre reinforced polymer(FRP)bolts and reinforcements,fibre reinforced concrete(FRC),and geopolymer concrete(GPC)were used to construct the *** examine the resilience,durability,sustainability,and multi-hazard resistance capacities,both cyclic and pendulum impact tests were carried *** experimental results demonstrated that the proposed precast joints had the comparable or even better performances as compared with the traditional monolithic joints under cyclic and impact *** simulations using ABAQUS were also adopted to determine the optimal values of the concrete-end-plate(CEP)thickness for the proposed dry joints and to further quantify other response parameters which could not be obtained during the test,e.g.,stress distribution,energy absorption,and stress *** on the influences of various parameters on joint performances under different loading conditions was also presented in this study.

关键词： multi-hazards cyclic loads impact loads FRP bolts FRP reinforcements geopolymer concrete fibre-reinforced concrete dry joints ABAQUS

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Failure Process and Energy Transmission for Single-Layer Reticulated Domes Under impact loads

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Transactions of Tianjin University 2008年第B10期14卷 551-557页

作者：王多智支旭东范峰沈世钊 School of Civil Engineering Harbin Institute of Technology

No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. TE (the time that the end of impact force) and TF (the time that members are broken) are two key times in the failure process. Characteristics of dynamic responses at the two key times are shown in order to make the failure mechanism clear. Then three steps of energy transfer are summarized, i.e. energy applying, energy loss and energy transfer, energy consump-tion. Based on the three steps, energy transfer process for the failure reticulated dome under once impact is introduced. Energy transmissibility and local loss ratio are put forward firstly to obtain EL F(the energy left in the main reticulated dome) from the initial kinetic energy of impactor. More-over, the distribution of failure modes is decided by EL F which leads to the maximum dynamic re-sponse of the reticulated dome, but not by the initial impact kinetic energy of impactor.

关键词： reticulated domes impact loads energy failure process energy transmissibility local loss ratio

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Experimental Investigation into Magnetorheological Damper Subjected to impact loads

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Transactions of Tianjin University 2008年第B10期14卷 540-544页

作者：相衡波方秦龚自明吴昊 Engineering Institute of Corps of Engineers PLA University of Science and Technology

A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation. But at present, the mechanical models of MRD were all derived from the experiment subjected to harmonic vibration loads. In this paper, a commercial MRD (type RD-1005-3) manufactured by Lord Corporation was studied ex-perimentally in order to investigate its isolation performance under the impact loads. A new me-chanical model of MRD was proposed according to the data obtained by impact test. A good agreement between the numerical results and test data was observed, which showed that the model was good to simulate the dynamic properties of MRD under impact loads. It is also demon-strated that MRD can improve the acceleration and displacement response of the structure obvi-ously under impact loads.

关键词： magnetorheological damper mechanical model impact loads

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Simultaneously measuring initiation toughness of pure mode Ⅰ and mode Ⅱ cracks subjected to impact loads

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Journal of Central South University 2022年第11期29卷 3720-3731页

作者： LANG Lin ZHU Zhe-ming ZHOU Chang-lin ZHOU Lei WANG Meng WANG Lu School of Architecture and Civil Engineering Xihua UniversityChengdu 610039China Key Laboratory of Deep Earth Science and Engineering(Sichuan University) Ministry of EducationChengdu 610065China Chengdu Surveying Geotechnical Research Institute Co. Ltd.of MCCChengdu 610023China

In order to simultaneously measure the initiation toughness of pure mode Ⅰ and mode Ⅱ cracks in one specimen,a large-size double-cracked concave-convex plate(DCCP)specimen configuration was *** tests were implemented in the drop plate impact *** gauges were employed to measure impact loads and crack initiation *** corresponding numerical model was established by using the dynamic finite difference program AUTODYN,and the experimental-numerical method and ABAQUS code were utilized to obtain the initial fracture toughness of the *** experiments and numerical research,we concluded that the DCCP specimen is suitable for measuring the initial fracture toughness of pure mode Ⅰ and mode Ⅱ cracks at the same time;the dynamic initiation toughness increases with the increase of loading rate and the crack initiation time decreases with increasing loading rate;the initiation toughness of mode Ⅱ crack is 0.5 times that of mode Ⅰ crack when subjected to the same loading *** the pre-crack in the vicinity of the bottom of a sample,when its length increases from 20 to 100 mm,the dynamic initiation toughness of the pure mode Ⅰ crack gradually decreases,and the longer the lower crack length is,the easier the crack would initiate,but the dynamic initiation toughness of pure mode Ⅱ crack varies little.

关键词： initiation toughness crack initiation time mode Ⅰ crack mode Ⅱ crack impact loads

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Non-Linear Analysis of Energy Absorption Systems under impact loads through FEM

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Journal of Mechanics Engineering and Automation 2012年第8期2卷 487-494页

作者： Elias Rigoberto Ledesma-Orozco Jose Angel Diosdado-De la Pena Gerardo Israel Pdrez-Soto Alonso Salazar-Garibay Juan Francisco Reveles-Arredondo Gilberto Villalobos-Llamas Pedro Duran-Resendiz Department of Mechanical Engineering Universidad de Guanajuato (DICIS) Salamanca M~xico

This paper presents a non-linear simulation of the impact on a structure with different energy absorption systems using finite element models. Literature review on bistable structure, aluminum foam and expandable polystyrene is presented and taken as basis to propose energy absorption systems. Using a base structure, these systems are implemented by means of finite element modeling. A comparison of the damage caused to the structure in case of impact without implementing energy absorption system, and implementing energy absorption systems based on bistable structures, polystyrene foam and aluminum foam are shown here in. The results demonstrate the advantages of using energy absorption systems on structures under impact loads.

关键词： Bistable impact loads non-linear analysis energy absorption.

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Finite element analysis of impact loads on the femur

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Chinese Journal of Traumatology 2007年第1期10卷 44-48页

作者：俞学中郭乙木李俊张蕴秋何荣新 Orthopedic Department Second Affiliated Hospital College of Medicine Zhejiang University Hangzhou 310009 China Department of Engineering Mechanics Zhejiang University Hangzhou 310027 China

Objective： To investigate the stress distribution and fracture mechanism of proximal femur under impact loads. Methods ： The image data of one male＇ s femur were collected by the Lightspeed multi-lay spiral computed tomography. A 3D finite element model of the femur was established by employing the finite element software ANSYS, which mainly concentrated on the effects of the directions of the impact loads arising from intense movements and the parenchyma on the hip joint as well as those of the femur material properties on the distribution of the Mises equivalent stress in the femur after impact. Results： The numerical results about the effects of the angle δ of the impact loads to the anterior direction and the angle γ of the impact loads to the femur shaft on the bone fracture were given. The angle δ had larger effect on the stress distribution than the angle γ, which mainly represented the fracture of the upper femur including the femoral neck fracture when the posterolateral femur was impacted. This result was consistent with the clinical one. The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. Conclusions ： A 3D finite element analysis model of the femoral hip joint under dynamic loads is successfully established by using the impact dynamic theory.

关键词： Femoral fractures Finite element analysis impact loads

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Wear behavior of bainite ductile cast iron under impact load

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International Journal of Minerals,Metallurgy and Materials 2014年第9期21卷 871-877页

作者： Ting Sun Ren-bo Song Fu-qiang Yang Chun-jing Wu School of Materials Science and Engineering University of Science and Technology Beijing

The dry impact wear behavior of bainite ductile cast iron was evaluated under three different impact loads for 30000 cycles. The strain-hardening effects beneath the contact surfaces were analyzed according to the surfaces＇ micro-hardness profiles. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） were used to observe the wom surfaces. The results indicated that the material with the highest hardness was the one continuously cooled at 20℃, which exhibited the lowest wear rate under each set of test conditions. The hardness of the worn surface and the thickness of the hardened layer increased with the increases in impact load and in the number of test cycles. The better wear performance of the sample cooled at 20℃ is attributed to its finer microstructure and superior mechanical properties. All the samples underwent the transformation induced plasticity （TRIP） phenomenon after impact wear, as revealed by the fact that small amounts of retained austenite were detected by XRD.

关键词： cast iron continuous cooling wear behavior impact loads martensitic transformations

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Ballistic behavior of plain and reinforced concrete slabs under high velocity impact

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Frontiers of Structural and Civil Engineering 2020年第2期14卷 299-310页

作者： Chahmi OUCIF Luthfi Muhammad MAULUDI Farid Abed Institute of Structural Mechanics Bauhaus-Universitat WeimarWeimar D-99423Germany Teknik Sipil Politeknik Negeri BandungGegerkalong Hilir Ds.CiwarugaBandung 40012Indonesia Department of Civil Engineering American University of SharjahSharjah 26666United Arab Emirates

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete *** this paper,we focus on the comparison of the performance of the plain and reinforced concrete slabs of unconfined compressive strength 41 MPa under ballistic *** concrete slab has dimensions of 675 mm x 675 mm x 200 mm,and is meshed with 8-node hexahedron solid elements in the impact and outer *** ogive-nosed projectile is considered as rigid element that has a mass of 0.386 kg and a length of 152 *** applied velocities vary between 540 and 731 m/s.6 mm of steel reinforcement bars were used in the reinforced concrete *** constitutive material modeling of the concrete and steel reinforcement bars was performed using the Johnson-Holmquist-2 damage and the Johnson-Cook plasticity material models,*** analysis was conducted using the commercial finite element package Abaqus/*** diameters and residual velocities obtained by the numerical model were compared with the experimental results and effect of steel reinforcement and projectile diameter were *** validation showed good agreement between the numerical and experimental *** added steel reinforcements to the concrete samples were found efficient in terms of ballistic resistance comparing to the plain concrete sample.

关键词： Johnson-Holmquist-2 Johnson-Cook reinforced concrete damage impact loads

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