Fracture and Damage Mechanics V

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Authors: Jin Ho Kim, Sin Chu Yang
Abstract: Inelastic analysis procedures may be useful as a first approximation for the seismic response of a structure. The Capacity Diagram Method procedure, which is based on R--T (Reduction-ductility-Period) relationships, is investigated to compare with the modified CDM procedure. The CDM procedure is applied to the example model, which is moment resistant RC frame. Two seismic hazard categories having exceedance probabilities of 2% in 50 years and 10% in 50 years earthquake ground motions have been selected for evaluating the performance of the example model. The performance objective of the example model is represented by the combination of a structural performance level and an earthquake hazard level.
Authors: Lei Li, Zhu Feng Yue
Abstract: The stress characterization around the hole in a composite plate under tensile stress has been studied by the analytical method in this paper. The distribution of the stress components has been presented. With the Hashin Failure Criterion, the failure characterization and different failure modes by the analytical method and finite element method are then studied. The possibility of the failure in different modes is compared. It is found that the fiber breakage, matrix failure and delamination are dominant. The place of the failure is between 70 degree and 90 degree to the loading direction in this paper. The results from analytical method and finite element method can agree with each other. And they are all confirmed by the experiment results.
Authors: Yang Du, Jian Feng Gao, Xin Sheng Jiang
Abstract: The fuel-air mixture explosion incidents in the large-scale metal oil storage tank are frequent occurrence and rapidly extend because of the tank structure being fractured and damaged by the fuel-air mixture explosion. In this paper, the simulation experiment and numerical simulation has been carried out for the fuel-air mixture explosion in the large-scale metal storage tank. The shock waves characteristic of the explosive pressure has been studied and discussed. The fracture and damage effects caused by the shock waves characteristic to the tank structure has been analyzed and discussed too.
Authors: Michihiro Sato, Tetsuya Ohashi, Takuya Maruizumi, Isao Kitagawa
Abstract: Thermal stress, plastic slip deformation and accumulation of dislocations in shallow trench isolation (STI) type ULSI devices when the temperature drops from 1000 し to room temperature are analyzed by a crystal plasticity analysis cord. The results show that dislocation accumulation takes place at the temperature range over 800 し, and the difference of 6 MPa in the lattice friction stress at 1000 し!causes increase of dislocation density more than 1.6 times. Dislocations generate and accumulate at the shoulder part of the device area and bottom corners of the trench. Dislocations are categorized into two groups. In one group, dislocation lines are mostly straight and parallel to the trench direction, and in the other group, dislocations make half loop type structure. Possibilities for the suppression of dislocation accumulation through control of lattice friction stress at high temperature region are discussed.
Authors: Lucio Nobile, Giuseppe Lamanna, Alessandro Soprano
Abstract: This work is focussed on the numerical prediction of the fracture resistance of a flat fullscale aluminium alloy 2024 T3 stiffened panel under monotonic traction loading condition. The numerical simulations are based on the micromechanical Gurson-Tvergaard (GT) model for ductile damage. The applicability of the GT model to this kind of structural problem has been studied and assessed by comparing numerical results, obtained by using the WARP 3D finite element code, with experimental data provided from literature.
Authors: Yong Xiang Zhao, Bing Yang, Wei Hua Zhang
Abstract: Fatigue reliability theory has recently verified that the sampling size related effect should be taken into account by confidence (C). However, most of the historic probabilistic S-N curves are given to only consider the scattered regularity effect by survival probability (P). Therefore, a reconstruction method of the historic curves is investigated to consider the sampling size effect. An effort is made on addressing the true production that the sampling size is less than 20 for material specimens and 10 for structural component specimens. A Monte Carlo simulation approach is first established to reconstruct the test S-N data. And then, the P-C-S-N curves are reconstructed with a general maximum likelihood principle. The practice for 40Cr steel has clearly indicated that, beyond all doubt, the reconstructed curves has overcome the shortages of the historic data.
Authors: Feng Hui Wang, Yong Zhang, Hong Wang
Abstract: In recently years, ruby fluorescence spectroscopy has been demonstrated as a powerful technique for monitoring residual stress evolution in the thermally grown oxide scale in thermal barrier coatings(TBC) systems. The measured residual stresses, in turn can be used to monitor evolution of damage in the coatings. Effective use of this technology for real time damage monitoring require the identification of strength in measured stresses that can be used as indicators of damage evolution.the present work focuses on studying the evolution of residual stresses in TBC systems during oxidation. The coating are atmospheric plasma sprayed (APS), the residual stress were measured at different oxidation time and to identify critical features so as to be used as indicators of failure in TBCs.
Authors: Feng Hui Wang
Abstract: Stress intensity factor of crack ahead of notch is important for understanding the failure of this kind structure. In this paper, a model is proposed to calculate the stress intensity factor of crack ahead notch configuration under bending load, the modeling value were verified by the data from literatures and experimental data of this paper, the trend of the value from model is agreement with that from experiments.
Authors: M.X. Zhang, X.L. Lee, A.A. Javadi
Abstract: There is a macro-crack and micro-crack system in rock, which affects almost all the mechanical properties of rock, especially for the fracture mechanism. The propagation of pre-existing cracks in rock samples under load is fundamental to understanding of rock fracture mechanisms. It is evident that assumption of Griffith theory was not in accord with the fact that numerous cracks exist in rock. So, it is difficult to explain how the propagation of a micro-crack developed into macro-failure by conventional theories. In order to investigate the cause and results of fracture within the rock, the stress concentration around the micro-cracks was analyzed, which resulted in propagation of wing cracks and connecting adjacent original cracks, eventually leading to macro-failure. The experiments on gypseous samples with pre-existing parallel cracks (flat rectangular in shape) under compression were carried out. The fracture mechanism and the stress equilibrium condition at brittle rock were discussed. Based on the fracture mechanism of brittle rock, a strength criterion of rock was proposed.
Authors: Hyo Jin Kim, Sang Ho Lee, Moon Kyum Kim
Abstract: An efficient and accurate numerical program with enhanced point collocation meshfree method is developed to simulate crack propagation under dynamic loading conditions. The enhanced meshfree method with point collocation formulation and derivative approximation in solids is presented. This study also presents the crack propagation criterion and computation of propagating direction, and the total structure of the numerical program named PCMDYC(Point Collocation Meshfree method for DYnamic Crack propagation). Several examples of crack propagation under dynamic loads are analyzed to simulate the arbitrary crack propagation under dynamic loads. The results show that PCMDYC predicts the propagating path of crack under dynamic loading conditions accurately and robustly.

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