Progresses in Fracture and Strength of Materials and Structures

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Authors: Jian Bing Sang, Su Fang Xing, Xiao Lei Li, Jie Zhang
Abstract: It has been well known that rubber-like material can undergo large deformation and exhibit large nonlinear elastic behavior. Because of the geometrically nonlinear of rubber like material, it is more difficult to analyze it with finite element near the notch tip. What is more, because there are varieties of the strain energy functions, implementation of these models in a general finite element program to meet the need of industry applications can be time consuming. In order to make use of the constitutive equation of Y.C. Gao in 1997 and analyze the notch tip of rubber-like material, a framework to implement the rubber-like material model is established within the general-purpose finite element program MSC.Marc. It will be very convenient to implement this isotropic hyperelastic model into the program with a user subroutine. This paper starts with the theoretical analysis based on the strain energy function given by Y.C. Gao in 1997. A user subroutine is programmed to implement this strain energy function into the program of MSC.Marc, which offer a convenient method to analyze the stress and strain of rubber-like material with the strain energy function that is needed. Though analysis with MSC.Marc, it is found that the result with finite element is consistent with the analytical result that given by Y.C. Gao in 1997, which testify that analyzing rubber like material with this method is reasonable and convenient.
Authors: Bing Rong Miao, Shou Ne Xiao, Ding Chang Jin, Guang Wu Yang
Abstract: In structural design for safety and durability, the primary concern is to reduce structural fatigue damages due to random dynamic loadings during the service life of locomotive vehicle system. Rolling stocks is facing new sever safety problems, such as bogie frame structure components fracture and safety-based design optimization to durability of locomotive. The objective of the current research is to find the most efficient approach to predict structure safety with Multi-Body Simulation (MBS) and Finite Element Method (FEM). The method is implemented to evaluate bogie frame fatigue damages under dynamic stochastic loadings. The time varying boundary conditions and dynamic load history acting on the large structure can be evaluated by applying the Multi-body Simulation technique in software SIMPACK. Stress/strain analysis technology with software ANSYS yields the danger stresses in the critical locations of the structure depending on the unite loads. And modal analysis is used to determine frequencies and mode shapes of structure. Based on these danger stresses distribution and dynamic load time history, fatigue life can be estimated with Palmgren-Miner theory. The standard time history method involves stress or strain cycle counting, damage prediction, and finally life estimation in Software FE-Fatigue with factor of safety technology.
Authors: Hong Wei Ma, Chong Du Cho, Chang Boo Kim, Hyeon Gyu Beom
Abstract: The bolted end-plate composite beam-CCSHRC column connection was validated to be ductile and offered an alternative to pre-Northridge connection. This study aims at the beam lower flange fracture in the connection test, and applies the J-integral criteria to examine the connection’s nonlinear fracture behavior. Advanced 3-D connection models containing initial crack in the high stress zone at lower flange are created, and the J values at the crack tip are calculated with considering the influences of certain parameters. The results demonstrate that the J values are strongly affected by the initial crack length and interstory drift. For 0.94, 1.35, 1.86 and 2.50 mm long crack, the J values sharply increase during loading history. The crack with a length of 2.50 mm propagates at a 66 mm drift, while the 1.35 mm long crack grows at a 120 mm drift. For 0.94 or 0.61 mm long crack, it keeps stable without growing upon loading. Besides, the J values exhibit a weak sensitivity to the beam concrete strength and tensile reinforcement ratio for beam. Under the same drift, the J-integral increases by about 3.5% when concrete strength changes from 15 to 24 MPa, and the J values at 0.6% tensile reinforcement ratio for beam are 1.5% larger than those at 0.3% or 1% reinforcement ratio.
Authors: Zhi Gang Yu, Kai Qing Xiao, Xiao Hua Zhu, Fu Lei Chu
Authors: Chao Hua Fan, Yu Ting He, Heng Xi Zhang, Hong Peng Li, Feng Li
Abstract: In the paper, genetic algorithm is introduced in the study of network authority values of BP neural network, and a GA-NN algorithm is established. Based on this genetic algorithm-neural network method, a predictive model for fatigue performances of the pre-corroded aluminum alloys under a varied corrosion environmental spectrum was developed by means of training from the testing dada, and the fatigue performances of pre-corroded aluminum alloys can be predicted. The results indicate that genetic algorithm-neural network algorithm can be employed to predict the underlying fatigue performances of the pre-corroded aluminum alloy precisely, compared with traditional neural network.
Authors: Shu Lin Li, Man Yi Hou
Abstract: The finite-element simulation models of the projectile and the discrete rod impacting to the aircraft panel structure in high velocity are established according to some experiment projects. Based on dynamic finite-element Program, the forming of impact damage in the panel structure is simulated. Through comparing the simulation results of damage pattern and size in the panel to the experiment results, the reliability of the material models and equations of state and contact algorithm used in the simulations is testified. Take the simulation of projectile vertically impacting to the panel as example, the aircraft panel structure response characteristics are analyzed briefly based on the results including the displacement of typical node in the panel, the stress course of one element and the energy change of the panel.
Authors: Li Jun Su, Jian Hua Yin, Shan Yong Wang, Hong Jian Liao
Abstract: Soil nailing is a widely used technique for stabilizing slopes and excavations. In all current design methods, the nail-soil interface shear strength, that is, the pull-out resistance of a soil nail is an important parameter which controls the design and safety assessment of the soil nailing system. The pressure grouting is a cost effective method for increasing the soil nail pull-out resistance and in turn improving the performance of the nailed structure. In this paper, a three dimensional (3-D) finite element (FE) model for pull-out tests is established and verified by comparing simulated results with measured data. This model is then used to simulate the effect of grouting pressure on the soil nail pull-out resistance.
Authors: Fu Kun Xiao, Guang Yi Sun, Li Hui Tian
Abstract: In order to study the effect of blast shake on the stability of tunnel during mining process, finite element analysis software for rock and soil engineering is used to simulate the effect of blasting shake. In the simulation, a short-time dynamic load is applied to the rock in the blasting zone. Dynamic stress field in the rock mass and distortion in the surface of the tunnel are calculated with the finite-element method. Equivalent displacement method is utilized to determine the amount of sudden applied load, the actuation duration and the range of action. Consequently, the maximum critical explosive content at the critical shake speed of rock mass can be defined.
Authors: Ming Li Huang, Tao Xu, Fei Wang, Wan Cheng Zhu
Abstract: In this paper, some numerical tests on the fracture process zone (FPZ) in concrete tension specimen were carried out with Material Failure Process Analysis code (MFPA2D) to investigate the behavior of the FPZ and the effect of the meso-scale heterogeneity of concrete on fracture process. The numerical results provide a clear indicator of the FPZ of concrete. The numerical results show that the FPZ accompanied by AE events gradually develops ahead of the notch tip with the increase of the loading in the concrete tension specimen. Moreover, many of the AE events bring about very small energy at the beginning of loading stage. Zones of higher energy events demonstrate a localization zone around the notch tip. The zones of AE events progresses forward gradually, and much densely distributed AE events can be observed in the FPZ. Moreover, the numerical simulations about AE events agreed well with those of the microcracks obtained by laboratory findings.
Authors: Ming Li Huang, Shan Yong Wang, Wei Lu, Wan Cheng Zhu
Abstract: In this paper, a Material Failure Process Analysis code (MFPA2D) was employed to investigate the interaction of end effect zone of specimen with the wing crack propagation inside the brittle specimen containing pre-existing flaws under uniaxial compression comparing with the experimental results. The numerical results show that the shorter the distance between the pre-existing flaw and the specimen's end , the slower the crack propagation process and the shorter wing propagation length is , and vice versa. In addition, the end effect zone was also influenced by the wing crack propagation.

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