Advances in Fracture and Failure Prevention

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Authors: Le Wen Zhang, Shu Chen Li, Shu Cai Li
Abstract: The method of bolt-grouting supporting, grouting into surrounding rock mass by bolts in jointed rock mass roadway, is obtained wide application. However, it is difficult to determine rock mass parameter of bolt-grouting supporting. This paper begins with the displacement, which is measured easily in practice. The method of back analysis is adopted to calculate the equivalent mechanics parameters of bolt-grouting rock mass. In process of back analysis three mechanics models is supposed which are homogeneous elastic model, inhomogeneous elastic model and elastic-plastic model and corresponding algorithm is established. What's more, this paper discusses the stability of inverse algorithm and copes the problem of back analysis parameter probably instable with QR decomposed algorithm and singular value decomposed algorithm, which will be a theoretical base to determine the mechanics parameter of bolt-grouting supporting rock mass and to estimate the surrounding rock stability. In a word, the method is established to estimate mechanics parameters of bolt-grouting jointed surrounding rock mass, and some significant results are obtained, which are of reference for actual project.
Authors: P. Lin, W.Y. Zhou, Q. Yang, Yu Jing Hu
Abstract: In this paper, a new three dimensional FEM model was elucidated on arch dam cracking analysis. Based on the least potential energy method, the stiffness of the interface between two types of mesh is coupled into the whole stiff matrix in this model. By this means, the FEM mesh of local area of arch dam can be easily changed from a coarse mesh to a fine mesh. By changing the density of mesh, the consideration of heterogeneity for the calculating elements is achieved by assigned to the elements random strength and elastic modulus according to a Weibull distribution. This model allows to densify the mesh of a local area and to trace the cracking of this area undertake damage criterion. By applying this new model, the mechanism of vertical cracks opening along the downstream surface of Shuanghe Arch Dam after two years of operation was briefly analyzed. The numerical result is basically agreed with the field investigation.
Authors: Sang Kyung Sung, Tae Sam Kang, Chul Hyun, Byeung Leul Lee, Jang Gyu Lee, Chan Gook Park, Young Jae Lee
Abstract: In this paper, presented are design, analysis, and experimental result of a tunable surface micromachined resonant accelerometer, ACRC-RXL. Also fabrication process of mechanical structure is illustrated. We used 40[μm] thick epitaxially grown polysilicon as structural layer and sealing area. With the exception of the CMP process, for smoothing the bonding area, the fabrication processes are simple as the conventional surface micromachining process. Experimental results show that the developed accelerometer has a performance of bias stability about 0.5mg and dynamic range over 10g.
Authors: M. Uchino, W. Fujisaki, E. Kurihara, K. Matsuda, Toshihiko Koseki
Abstract: This study is concerned with the fundamental characteristics of a new nondestructive measuring technique of the tooth roughness with precisely. In the dental clinics, the estimation of roughness of tooth surfaces with a hand explorer is one of the important tests for the finishing the crown re-shaping and resin fillings. If the tooth surface is rough enough to hold dental plaque, it occasio-nally causes dental diseases around it. Therefore, it is important to measure the roughness of the tooth surfaces for the prevention of furthermore distraction of the tooth. Laser speckle measurement is used as an evaluation method for objectively measuring the surface roughness with non-contact. In this study, a laser speckle measurement system for measuring the surface roughness is constructed. Comparison measurement is carried out for the tooth pieces with the various unidirectional roughness and the metallic test pieces with the standard roughness. The experimental results using the actual measuring system show some important points as follows. Firstly, there is a good correla-tion between the laser speckle pattern and the tooth roughness as well as that of the metallic test pieces. Secondly, the reflection from the tooth shows a different tendency in comparison with the reflection from the metallic test pieces.
Authors: Wei Hua Xu, Tong Yi Zhang
Abstract: This paper studies surface effects on the depth-dependent hardness and proposes a novel method to estimate the apparent surface stress from nanoindentation tests. Good agreement is found between the theoretical predictions and experimental data of the depth-dependent hardness, thereby indicating that the apparent surface stress plays an important role in the depth-dependent hardness for various types of materials, such as metals, ceramics, and polymers.
Authors: M. Tanaka, Y. Kimura, A. Kayama, L. Chouanine, Reiko Kato, J. Taguchi
Abstract: A computer program of the fractal analysis by the box-counting method was developed for the estimation of the fractal dimension of the three-dimensional fracture surface reconstructed by the stereo matching method. The image reconstruction and fractal analysis were then made on the fracture surfaces of materials created by different mechanisms. There was a correlation between the fractal dimension of the three-dimensional fracture surface and the fractal dimensions evaluated by other methods on ceramics and metals. The effects of microstructures on the fractal dimension were also experimentally discussed.
Authors: L. Chouanine, M. Takano, F. Ashihara, Osamu Kamiya
Abstract: A microtibological study of the effect of the CMP machining surface damages (SD) on the micromechanical properties of AlN electro-static chuck (ESC) for silicon plasma etching is presented. AFM and SEM examinations of the AlN ESC, which were CMP finished to a surface roughness, Ra = 20 nm, have revealed machining geometry errors and chemical mechanical SD caused by the CMP slurry. The elastic modulus (E) and hardness (H) of AlN and those of yttrium (Y) particles were discretely clarified using localized nanoindentation technique. The results showed that the CMP machining SD fatally affected the AlN/Y boundary strength and resulted to errors in the first contact points between the indenter and the sample. In addition to SD, the micro scale viscoelasticity phenomena of AlN in indentation caused peculiarities at peak loads in the load vs. depth plots. Under these circumstances, the values of E and H measured using Oliver and Pharr's method are in fact underestimated; E = 400 GPa and H = 20 GPa for AlN particles, 300 GPa and 17 GPa for Y particles and 500 GPa and 16 GPa for AlN/Y interface, respectively.
Authors: Ai Ling Wen, R.M. Ren, Sheng Wu Wang, Shinichi Nishida
Abstract: The paper investigated nano-crystallization on surface layer of commercial pure titanium by using high-energy shot peening. The grain size and the microstructure in deformed surface layer by high-energy shot peening are analyzed with X-ray diffraction and TEM etc. In addition, the variations of surface microhardness are examined after high-energy shot peening. The results described that the nano-crystalline surface layer have been formed in commercial pure titanium with a structure of hexagonal closet packet, by high-energy shot peening. The surface microhardness increases and the grain size in nano-crystalline surface layer diminishes, with increasing the time in high-energy shot peening. The minimum nano-crystalline grain size is approximately 40 nm.
Authors: Tsutomu Yoshida, Shin-ichi Matsui, Mitsuo Hoshino, Masaru Sakata
Abstract: Analyzing a sound produced by an impact of a fallen ball upon a small rectangular bar specimen, elastic moduli of engineering ceramic composites can be determined. In this paper,three-points bending and torsional test devices which employed the specimen for the impactsound test were designed. Using the devices, elastic moduli of various materials were mea-sured applying deformation theory. The elastic constants evaluated by the impact sound testwere compared with those measured by the devices. They agreed well. A reliable measure-ment system was developed for elastic constants of anisotropic materials.
Authors: T. Nakamura, Hiroki Nakamura, O. Fujita, T. Noguchi, K. Imagawa, T. Inoue
Abstract: Atomic Oxygen (AO) is a main constituent of the atmosphere on low earth orbit where the International Space Station (ISS) goes around, and is also known as the matter which deteriorate many kinds of polymers. However, the strength properties of polymers suffered from AO have not been fully clarified. To investigate this problem, we irradiated AO to Poly-Ether-Ether-Keton (PEEK) films under three kinds of tensile stresses. Based on the analysis of irradiated samples, the effects of AO fluence (total amount of AO per unit area) and tensile stresses on damage properties were discussed with regard to reaction efficiency Re, surface morph, and tensile strength properties. As a result, the following were obtained: (1) Test piece surfaces exhibited considerable damage covered by conical pits of 1μm sizes with a few μm depths. (2) Test piece thickness of irradiated area decreased almost proportionally to AO fluence. (3) Re and thickness reduction was accelerated by tensile stress. (4) Strength properties after AO irradiation were almost same as those of a pristine sample considering the decrease of specimen thickness.

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