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Acta Mechanica Solida Sinica 2022年第1期35卷 79-89页

作者： Zhanqi Cheng You Wu Liusheng Chu Jiyu Tang Chengfang Yuan Hu Feng School of Civil Engineering Zhengzhou UniversityZhengzhou 450001China

In this paper,a semi-discrete model based on peridynamics(PD)for engineered cementitious composites(ECCs)is applied to simulate the fracture behavior of functionally graded ECC(FGECC)*** is a new application of PD in *** to simulating the crack behavior,the convergence of the PD model for ECC is discussed and the appropriate horizon size 5 and nonlocal ratio m are obtained,i.e.,S=1.6 mm and m=*** addition,when the bond strain exceeds the elastic limit,a damage variable is introduced into the model,and the model is validated using a simple numerical ***,the dynamic fracture behavior of a two-dimensional FGECC beam under four-point bending is investigated,and the effect of the initial crack location on the fracture behavior is *** results show that the initial crack location can affect the crack propagation pattern,thereby enabling one to understand the dynamic fracture behavior of ECC structures and guide the engineering practice.

关键词： Peridynamics Functionally graded ECC structures Semi-discrete models dynamic fracture

A Peridynamic Model for dynamic fracture of Layered Engineered Cementitious Composites

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Acta Mechanica Solida Sinica 2022年第4期35卷 661-671页

作者： You Wu Jiajia Zhou Jiyu Tang Chengfang Yuan Zhanqi Cheng School of Civil Engineering Zhengzhou UniversityZhengzhou450001China School of Mechanics and Safety Engineering Zhengzhou UniversityZhengzhou450001China

In this paper,a peridynamic model for simulating the dynamic fracture in layered engineered cementitious composites(LECC)is *** model takes into account the location information of the fibers as well as the distribution *** addition,numerical simulations of LECC beams under four-point bending are carried *** effects of notch size and fiber volume fraction are *** numerical results show that the notch size and gradient distribution of fiber volume fraction affect the crack propagation pattern,which can help to understand the dynamic fracture behavior of engineered cementitious composites.

关键词： Peridynamics Layered ECC dynamic fracture Fiber

dynamic fracture ANALYSIS OF AGED GLASSY POLYCARBONATE BY THE METHOD OF CAUSTICS

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Acta Mechanica Solida Sinica 2013年第5期26卷 448-457页

作者： Guiyun Gao Zheng Li Mehrdad Negahban State Key Lab for Turbulence and Complex Systems and College of Engineering Peking University Department of Engineering Mechanics University of Nebraska-Lincoln

The purpose of this work is to investigate the dynamic fracture properties of glassy polycarbonate （PC） with different aging times. The optical method of caustics is adopted in which the shadow spot patterns are recorded by a high speed camera during the dynamic fracture process. Then, the dynamic crack propagation, the stress intensity factor （SIF） and the dynamic fracture toughness of aged PC are obtained through an analysis of the characteristic size of caustic pattern. Moreover, by combining with the investigation of the fracture surface and the energy release rate analysis, the influence of aging time on the dynamic fracture behavior is discussed. Results show that the dynamic fracture toughness and critical energy release rate of PC decreases with aging time for short aging times, whereas they have little change or even increase for longer aging times. Therefore, aging modifies the mechanical properties especially the dynamic fracture properties of PC nonlinearly, not linearly as generally thought of.

关键词： polycarbonate physical aging dynamic fracture stress intensity factor

Finite Element Simulations of dynamic fracture of Full-Scale Gas Transmission Pipelines

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Acta Mechanica Solida Sinica 2018年第3期31卷 357-368页

作者： Peishi Yu Jinjie Lv Junhua Zhao Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology School of Mechanical Engineering Jiangnan University

The dynamic crack growth in a full-scale gas pipeline of API X80 steel is analyzed using the finite element method with the cohesive zone model. Based on the simulation, it is revealed that for the moderate steady-state crack growth, the crack-tip-opening angle strongly depends on the crack growth speed. In addition, the threshold initial crack sizes under different internal pressures are analyzed, which show a significant three-dimensional effect due to the wall thickness of the pipeline. The presented model offers a feasible way to study some details of the dynamic fracture of full-scale pipelines when tests are difficult or expensive.

关键词： dynamic fracture Finite element Full-scale pipeline Cohesive zone model

Study on dynamic fracture behavior of TA15ELI alloy under mode-Ⅱ loading by caustics method

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Rare Metals 2010年第4期29卷 361-365页

作者： LIU Rui,HUI Songxiao,YE Wenjun,MI Xujun,XIONG Baiqing,and YOU Zhenping State Key Laboratory for Fabrication & Processing of Nonferrous Metals,General Research Institute for Nonferrous Metals,Beijing 100088,China State Key Laboratory for Fabrication & Processing of Nonferrous Metals General Research Institute for Nonferrous Metals Beijing China

The dynamic fracture behavior of TA 15ELI alloy with lath-like microstructure was studied by caustics method. Specimens with double-side pre-notch were tested under the plane-stress condition at mode-II loading with a drop hammer system. Caustics information recorded in films illustrated the histories of both crack length and stress intensity factor. The dynamic fracture toughness and crack growth velocity of TA15ELI with lath-like microstructure were determined to be 279 MPa.m1/2 and 32.6 m/s, respectively. SEM fractograph analysis showed a mixed feature of mainly plastic mode for TA 15ELI alloy in dynamic mode-II fracture. Shear localization was observed in the vicinity of the crack initiation area.

关键词： titanium alloy dynamic fracture caustics method fracture toughness crack growth

A NOVEL METHOD FOR EVALUATING PLANE STRESS dynamic fracture TOUGHNESS OF 0Cr18Ni10Ti STAINLESS STEEL WELDED JOINTS

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Acta Metallurgica Sinica(English Letters) 2008年第4期21卷 303-312页

作者： Z.J. Xu Y.L. Li School of Aeronautics Northwestern Polytechnical University Xi＇an 710072 China

A novel method was proposed for the evaluation of Mode I dynamic fracture toughness （DFT） under plane stress and small scale yielding conditions for welded joints of stainless steel （SS）, 0Cr18Ni10Ti. In a hybrid experimental-numerical approach, the experiments were carried out on the Hopkinson pressure bar apparatus, and three dimensional （3D） transient numerical simulations were performed by a finite element （FE） computer program. Macroscopical plastic deformation was observed at the loading and supporting points, on the specimens, after the test, which could cause a large error if omitted in the numerical simulation. Therefore, elustic-viscoplustic analysis was performed on the specimen by adopting the Johnson-Cook （J-C） model to describe the rate-dependent plastic flow behavior of the material. The material heterogeneity in the mismatched welded joints, induced by the difference in the base metal （BM） and the weld metal （WM） in yield stress, has also been taken into consideration by using the J-C models separately. Good accordance was obtained between the experimental and the computational results by the present approach. The relationship between plane stress DFT and loading rate was also obtained on the order of 108 MPa.m^1/2.s^-1.

关键词： 0Cr18Ni10Ti Welded joint High strain rate dynamic fracture Plane stress

dynamic fracture of a Semi-Crystalline Bio-Based Polymer Pipe: Effect of Temperature

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Journal of Minerals and Materials Characterization and Engineering 2021年第3期9卷 227-244页

作者： Jean Benoit Kopp Jeremie Girardot Arts et Metiers Institute of Technology Université de Bordeaux CNRS INRA INP I2M HESAM Université Talence France

The influence of temperature on the resistance to rapid crack propagation of a semi-crystalline bio-based polymer was studied. The experimental results described in this study allow to initiate a first discussion on the role of viscosity and its link with the fracture behaviour and a heterogeneous microstructure such as the semi-crysalline polymer. dynamic fracture tests on pipes were carried out. It would appear that a temperature decrease of approximately 40℃ relative to ambient has no significant influence on the average crack propagation velocity (≈0.6cR), fracture energy and surface roughness. On the contrary, crack propagation paths seem to vary with temperature. The difference in fracture behaviour between the amorphous and crystalline phase varies significantly as a function of temperature. The difference between the initiation resistance and the rapid propagation also varies. This difference seems to be significantly reduced by lowering the temperature. The mechanisms of cavitation damage and plastic flow are increasingly limited by the decrease in temperature (and therefore in macromolecular mobility). Crack propagation in the pipe is more extensive and therefore more critical. This is emphasised in particular by the probability of the material to be macro-branched as the temperature decreases.

关键词： dynamic fracture Rapid Crack Propagation Semi-Crystalline Pipe Fractography

Predicting impact strength of perforated targets using artificial neural networks trained on FEM-generated datasets

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Defence Technology（防务技术） 2024年第2期32卷 32-44页

作者： Nikita Kazarinov Aleksandr Khvorov Saint Petersburg State University Saint Petersburg 199034Russia Higher School of Economics Saint Petersburg 190121Russia

The paper considers application of artificial neural networks(ANNs)for fast numerical evaluation of a residual impactor velocity for a family of perforated PMMA(Polymethylmethacrylate)*** ANN models were trained using sets of numerical results on impact of PMMA plates obtained via dynamic FEM coupled with incubation time fracture *** developed approach makes it possible to evaluate the impact strength of a particular target configuration without complicated FEM calculations which require considerable computational ***,it is shown that the ANN models are able to predict results for the configurations which cannot be processed using the developed FEM routine due to numerical instabilities and errors:the trained neural network uses information from successful computations to obtain results for the problematic cases.A simple static problem of a perforated plate deformation is discussed prior to the impact problem and preferable ANN architectures are presented for both *** insight into the perforation pattern optimization using a genetic algorithm coupled with the ANN is also made and optimized perforation patterns which theoretically enhance the target impact strength are constructed.

关键词： Machine learning Impact dynamic fracture FEM Mesh distortion Optimization

Perforation studies of concrete panel under high velocity projectile impact based on an improved dynamic constitutive model

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Defence Technology(防务技术) 2023年第9期27卷 64-82页

作者： Fei Zhou Hao Wu Yuehua Cheng Department of Disaster Mitigation for Structures College of Civil EngineeringTongji UniversityShanghai200092China

The finite-depth concrete panels have been widely applied in the protective structures,and its impact resistance and dynamic fracture failures,especially the scabbing/perforation limits,under high velocity projectile impact,are mainly concerned by protective engineers,which are numerically studied based on an improved dynamic concrete model in this ***,based on the framework of the KCC(Karagozian&Case concrete)model,a dynamic concrete model is proposed which considers an independent tensile damage model and a continued transition between dynamic tensile and compressive ***,the strength surface,equation of state and damage parameters of the proposed model are comprehensively calibrated by a triaxial compressive test with high confinement pressure,the rationality of which is further verified based on the single element tests,e.g.,uniaxial and triaxial compression as well as uniaxial,biaxial and triaxial ***,a series of projectile high velocity impact tests on thin and thick concrete panels are simulated,which indicates that the projectile residual velocity and dynamic fracture failures are reproduced satisfactorily,while the KCC model underestimates both the spalling and scabbing dimensions ***,based on the validated concrete model and finite element analyses approach,the validations of the existing five empirical formulae are evaluated,in terms of the depth of penetration(DOP)and scabbing/perforation limits of concrete *** the Army corps of engineers(ACE)and modified National Defense Research Committee(NDRC)formulae are recommended in the design of the protective structure to avoid scabbing failure.

关键词： Concrete panel Projectile dynamic fracture Scabbing limit Constitutive model

A fractional differential constitutive model for dynamic stress intensity factors of an anti-plane crack in viscoelastic materials

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Acta Mechanica Sinica 2014年第3期30卷 403-409页

作者： Run-Tao Zhan Zhao-Xia Li Lei Wang Department of Engineering Mechanics Southeast UniversityJiangsu Key Laboratory of Engineering Mechanics School of Civil Engineering Southeast University

Fractional differential constitutive relationships are introduced to depict the history of dynamic stress inten- sity factors （DSIFs） for a semi-infinite crack in infinite viscoelastic material subjected to anti-plane shear impact load. The basic equations which govern the anti-plane deformation behavior are converted to a fractional wave-like equation. By utilizing Laplace and Fourier integral transforms, the fractional wave-like equation is cast into an ordinary differential equation （ODE）. The unknown function in the solution of ODE is obtained by applying Fourier transform directly to the boundary conditions of fractional wave-like equation in Laplace domain instead of solving dual integral equations. Analytical solutions of DSIFs in Laplace domain are derived by Wiener-Hopf technique and the numerical solutions of DSIFs in time domain are obtained by Talbot algorithm. The effects of four parameters α, β, b1, b2 of the fractional dif- ferential constitutive model on DSIFs are discussed. The numerical results show that the present fractional differential constitutive model can well describe the behavior of DSIFs of anti-plane fracture in viscoelastic materials, and the model is also compatible with solutions of DSIFs of anti-plane fracture in elastic materials.

关键词： dynamic fracture Stress intensity factors Fractional differentiation - Anti-plane fracture Viscoelasticmaterial Wiener-Hopf