Progresses in Fracture and Strength of Materials and Structures

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Authors: Xin Gui Zhang, Guo Wei Ma, T.Y. Khoon, N.P. Yi, H. Wu
Abstract: The stabilized soil is a reinforcement material being applied extensively to civil engineering and hydraulic engineering. At present, chemical methods are used to improve density and strength of soil by increasing the state of inter-particles’ contacts and forces among particles or particle groups. Liquid stabilizer is the chemical reinforcing agent of stabilized soil. The physical and chemical interaction of reinforcing agent - clay - water affects the reinforcement of soil. The mechanism of strengthening soil using the Liquid stabilizer had not been clear. In laboratory, many experiments were carried out in order to study strengthening mechanism of the stabilized soil. From the result of the test and analysis of its characteristics, we recognized that the reinforcement effect of the liquid stabilizer is controlled by the mini-structure of the stabilized soil, and strength of the stabilized soil comes mainly from its mini-structure.
Authors: Kwang Joon Hong, Young Nam Chun, Bong Ju Lee
Abstract: We developed a device that makes possible the normal production of low-temperature plasma under atmospheric pressure. For plasma generation, a radio frequency of rf (13.56MHz) was used. From the Fourier transform infrared (FT-IR) analysis, the absorption peak of C=O (the carbonyl group) was observed around 1715 cm-1, and the absorption peak of CH was observed around 2950 cm-1. Of those, from the conclusion that the absorption peak of C=O was proportional to the amount of CO2 added, we discovered that the C=O carbonyl group originated from the CO2 molecules.
Authors: Kenji Machida, Shohei Miyagawa
Abstract: Recently, the influence of heat conduction has been considered to be a big problem. Then, the influence of heat conduction was investigated by the experiment which changed the material, thickness of the specimen and frequency of a cyclic load. Then, the infrared hybrid method was developed to separate individual stress components. However, it has the influence by heat conduction in the infrared stress measuring method. Therefore, an error will arise in the infrared hybrid analysis. Then, the system which corrects the error by the inverse analysis was developed. Thereby, the accuracy of the stress intensity factor was able to be raised. Furthermore, the accuracy of hybrid method considering to heat conduction was discussed in comparison with the 3-D finite-element analysis and 2-D hybrid method.
Authors: Kenji Machida, Kazuhiro Okazaki
Abstract: The displacement obtained from the experiment is including large error and it is impossible to evaluate the stress and the strain with high accuracy using raw displacement data. The 2-D intelligent hybrid method was applied in order to evaluate the 2-D stress field. In the infinitesimal deformation within elastic region of steel or an aluminum alloy, the quantity of displacement is less than 1 pixel, and analysis accuracy deteriorates. We need the system which can analyze the displacement more exactly in sub-pixel field. Hence, the Newton-Raphson method was applied after obtaining the displacement at any point of the image. On uniform deformation field, the infinitesimal strain was estimated with less than 0.01pixels of an error by DIC by taking into consideration only the 1st deformation gradient in the Newton Raphson method. On nonuniform deformation near the crack tip, it was estimated with about 0.018pixels error by taking the 2nd deformation gradient into consideration.
Authors: Naoaki Noda, Yasushi Takase, Ryohji Shirao, Jun Li, Jun Suke Sugimoto
Abstract: In this study, singular stress fields at the ends of fibers are discussed by the use of models of rectangular and cylindrical inclusions in a semi-infinite body under pull-out force.The body force method is used to formulate those problems as a system of singular integral equations where the unknown functions are densities of the body forces distributed in a semi-infinite body having the same elastic constants as those of the matrix and inclusions.Then generalized stress intensity factors at the corner of rectangular and cylindrical inclusions are systematically calculated with varying the elastic ratio, length, and spacing of the location from edge to inner of the body. The effects of elastic modulus ratio and aspect ratio of inclusion upon the stress intensity factors are discussed.
Authors: Seiji Ioka, Keiji Masuda, Shiro Kubo
Abstract: Free-edge stress singularity usually prevails at the edge of the interface of the bonded dissimilar materials. When two materials are bonded by using an adhesive, an interlayer develops between two materials. An interlayer may inserted between two materials to defuse the residual stress due to the difference in the coefficients of thermal expansion. In this study, to investigate the effect of the interlayer on the free-edge stress singularity of the bonded dissimilar materials with an interlayer, the stress distributions on the interface were examined numerically and theoretically. Relation between the free-edge stress singularity of the bonded dissimilar materials with and without an interlayer was investigated by using the boundary element method. It was found that the effect of the interlayer on the stress distribution was limited within a small area of the order of the interlayer thickness. Stress distributions near the edge of the interface were controlled by the free-edge stress singularity of the bonded dissimilar materials without an interlayer.
Authors: Young Shin Lee, Se Hoon Lee, Young Jin Choi, Je Wook Chae, Eui Jung Choi
Abstract: On the human-rifle system, the human body is affected by the firing impact. The firing impact will reduce the firing accuracy and change the initial shooting posture. Therefore the study of biomechanical characteristics using human-rifle modeling and numerical investigation is needed. The muscle-skeleton model was developed by the finite element method using beam and spar elements. In this study, a structural analysis has been performed in order to investigate the human body impact by firing a 5.56mm small caliber machine gun. The firing experiments with a standing shooting posture were performed to verify analytical results. The result of this study shows analytical displacements of the human-rifle system and experimental displacements of real firing. In the results, the analytical displacement on the human body is presented.
Authors: Yue Peng Song, Xiao Zhang, Guo Quan Liu
Abstract: The Jominy end-quench curves of non-alloyed and alloyed steels can be predicted by nonlinear equation method. Without considering the interaction effects of alloying elements on the curves, however, the prediction for multi-alloyed steels may be different markedly from that experimentally determined. Hence, an improved mathematic model for predicting the Jominy end-quench curves of multi-alloyed steels was proposed by introducing a parameter named “alloying element interactions equivalent” to the nonlinear equations. With the improved model, the predicted Jominy curves agree very well with the experimental ones for more than 300 steel grades found in the literature. A computer-aided design system for hardenability of structural steels was then developed. The system not only can quantitatively evaluate the hardenability of structural steels, but also is very helpful to design steels and hardenability-aimed components. The optimal composition range of a new steel was so successfully designed as an example. Further research results show that the computer-aided design system so developed can also be used for monitoring of hardenability variation in steel industrial production.
Authors: Qi Zhang, Yang Guang Chen, Li Sha Niu, Hui Ji Shi
Abstract: Flow-induced localized corrosion is regarded as one of the main degradation mechanisms of materials. As an initial step of the simulation of a pipe, a plate is chosen to simplify the problem. In this paper, finite element method is used to simulate the corrosion process in the plate by employing nonlinear geometry and physics equations of the material to describe the quasi-static process. An elastic modulus iterative procedure was performed to obtain the material parameters in consideration of the nonlinear physical properties of corrosion. The effect of corrosion is then considered by introducing a criterion between depth and time, calculating corrosion depth at progressive given time. Dead and live finite elements are employed to consider the invalidation of the material. Thus the movable boundary conditions can be taken into account and the dynamic status of corrosion can be simulated. Stress corrosion process under flowing fluid condition is analyzed and then the results of representative examples are compared with published results.
Authors: Shinjiro Kawabe, Hidetoshi Sakamoto, Kazuo Satoh, Masahiro Himeno, Shigeru Itoh
Abstract: The high-speed fracture mechanics of glass bottles by using underwater shockwaves technique and its application for recycling system of glass bottles were discussed. The proposed small fragments, also called “Cullet”, generation technique can decrease the recycling cost by carrying out of crashing and cleaning process simultaneously. In this study, the effects of the explosive conditions and multi-specimen’s arrangements on the “Cullet” sizes were investigated and basic data for commercialization of this method were obtained. An FEM simulation and framing photograph were used to observe underwater shock wave and fracture propagation.

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