Fracture and Damage Mechanics V

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Authors: Ming Chun Tseng, Hsin Her Yu, Shug June Hwang, Chien Chang Lin, Kuang Chyi Lee
Abstract: A novel flexible polymer was used for the new generation display panel, which was prepared by thermal annealing treatments. Atomic force microscope (AFM) and visible spectroscopy were employed to measure the surface roughness and the optical transparency of the substrates. Mechanical cycles bending were carried on the flexible substrates in this study. Surface morphology of the substrates after bending was observed by scanning electron microscope (SEM). The performances of the OLED device were compared for the samples with and without cycles bending.
Authors: Jai Sug Hawong, Dong Chul Shin, Song Ling Han
Abstract: The reflective photoelastic experimental hybrid method for the fracture mechanics of orthotropic material was developed in this research. it was verified that the reflective photoelastic experimental hybrid method was more useful for the static plane problems of fracture mechanics, for the determination of stress intensity factors and for the separation of stress components at the vicinity of the crack-tip than the transparent photoelastic experimental hybrid method in orthotropic materials.
Authors: Young Tae Cho, Choong Ho Lee, Kwang Hee Im, In Nam Hwang
Abstract: General structures or machines are firmly connected by bolts so that they have many contact surfaces. Between these contact surfaces, there is a movement that vibrates with tiny amplitude, which causes friction, leading to fretting damage. This damage causes a remarkable reduction in the fatigue strength of the structures sub-materials, leading to remarkable fall-down of life span of machines and structures. The particle reinforced composites under research in the aerospace and automobile industries, theoretical analysis and research on fretting fatigue involved with contact are needed, but there are few domestic studies. Therefore, this study is to identify cracking damage, its initiation, growth direction and location by considering the strength load and contact (surface/surface) in particle reinforced composites. So it performed a study on ellipsoidal particle reinforced composites that have contact force under tensile load. This study performed a theoretical analysis and a fretting test to identify damage mechanism to industrial structures as well as aerospace and automobile industries according to expanded coverage of application and development of the composites.
Authors: Huo Ran Sun, Shu Hong Wang, Shuai Xu, Wen Lin Chen
Abstract: The 290 level cave is situated in Nanfen Surface Mine, Liaoning, China. Nanfen surface mine is one of the biggest iron ore in Benxi Iron Company. The base line of the pit bottom has reached 346m level in Nanfen surface mine. The importance of in situ assessment of stability of the 290 level cave for next mining design and construction has been met. Investigation at the Nanfen Surface Mine has shown that damage exists around 290 level cave and that the damage develops from the energy imparted to the rock by the excavation method and by redistribution of the in situ stress field around the 290 level cave. Subsequent near-by excavations, removal of loose material from the existing cave and pore pressure changes will all influence the development and extent of rock damage, as does the rock type and its fabric. Based on the engineering characters and rock mechanics, the main characteristics of stress induced brittle failure of the site are introduced. Various evaluation and measures are sought to stabilize the over-stressed rock mass. The induced anisotropic damage process was modeled. The major results from numerical analysis of the cavern are presented and validated by direct comparison with actual monitoring data. Next, an optimization study was conducted with the experimentally validated and adjusted mathematical model, measured with a recorder within such a cave. And the stability of the 290 level cave in Nanfen Surface Mine was analysis. As a result, the model is expected to be a useful tool for simulation, design, and optimization of pasteurization tunnels. A suitable support measure was proposed and taken.
Authors: Kai Duan, Xiao Zhi Hu
Abstract: The recently-developed boundary effect concept and associated asymptotic model are used to explain the size effect phenomena in fracture of quasi-brittle materials. It is demonstrated that the size dependence of the fracture toughness and strength of quasi-brittle materials is indeed due to the influences of specimen boundaries on the failure mode and therefore, on the strength of the specimen. To verify the boundary effect concept, fracture tests on a high strength concrete reported by Karihaloo et al are analysed and predicted using the asymptotic model. The results show that the predictions of the asymptotic boundary effect model agree very well with those experimental results.
Authors: Dao Ying Xi, Song Lin Xu, Yue Zhan Tao, Ting Li
Abstract: As the rocks were composed of many minerals, high temperature might lead to the non-consistent deformation among these components. That was the mechanism of thermal damage. In the present paper, the thermal damage of rocks was investigated under a much broader temperature range until minerals phase transition. The experimental techniques of AE and the internal friction were proven to be the most useful tools to reveal the thermal damage. The affection of thermal damage to Kaiser Effect of temperature and the coupled effects of thermal and mechanical damage were also discussed.
Authors: Li Yun Li, Feng Guang Xu, He Ping Xie, Wei Ning
Abstract: This paper illustrates some preliminary experimental, numerical and theoretical analysis results of mixed mode I-III rock cracks under apparent mode III loading. Some edge notched granite specimens are tested under out-of-plane four-points shearing loading condition, i.e., an apparent mode III loading condition. A series finite element analysis was conducted to understand the mechanism of the crack fracture propagation under this loading condition. The stress intensity factor distributions along the 3-D crack tips are also obtained. All crack fracture propagation surfaces of the specimens are similar helicoids which radius can be mainly influenced by the loading patterns, i.e., the action width s. The crack fracture initiates at the midpoint of the crack front. From the numerical calculation and experimental investigation, it has been revealed that all of these crack fracture initiations are caused by maxima tensile stress σ1. Based on this stress σ1, a new fracture criterion of mixed mode I-III is proposed. Its predictions agree well with the experiment results. This criterion can be applied to practice engineering designs which are related with mixed mode I-III or pure mode III rock crack fracture problems.
Authors: H.H. Lee, P.Y. Chang
Abstract: This study proposes a procedure of damage inspection for the infrastructure in the harbor. Because most infrastructures in the harbor are submerged under the water the damage inspection is very difficult to process. Normally, divers with special scheme of damage inspection are required and the cost is very expensive. Therefore, a two-stage inspection strategy is proposed. After the first stage of inspection the more detailed second stage inspection will be requested dependent on the examination results. In the second stage of inspection particularly, it is focused on the wharf structures of steel-sheet pile type, where the related items are identified corresponding to the characteristics of the structural system.
Authors: Tomoyuki Hirata, Junichi Shibano, Takahisa Shobu, Kenji Suzuki, Hiroshi Kaneko, Michiaki Kobayashi
Abstract: The strain in the bulk of material was evaluated using high energy white X-rays from a synchrotron radiation source of SPring-8 in Japan. An austenitic stainless steel (JIS-SUS304L) was used for a specimen. The specimen of 5 mm thickness was subjected to the bending. The internal strain of it could be measured using white X-rays which range of energy from 60 keV to 125 keV. The measurement of the internal strain with a high accuracy was accomplished using the strain data from several lattice planes of γ-Fe simultaneously. Furthermore, the measurement error of strain could be decreased by using the diffracted beam with high energy, high peak count and the similar profile with the Gaussian distribution. The results showed that the high energy white X-rays is effective for the internal strain measurement in the depth of the order of millimeter.
Authors: Wei Ping Jia, Dong Ying Ju, Akira Shimamoto
Abstract: An experimental study of high pressure water jet peening treatment on SPA-H and SPCC steel was conducted to study the effects of cavitation impacts of high-speed water on fatigue crack initiation and propagation of notched specimens. Pull-pull fatigue tests’ condition was 350 MPa maximum stress amplitude, 0.1 stress ratio and 10Hz frequency, while in-situ observation by SEM was employed. It was found that fatigue life of water jet peening treated SPA-H specimens has been obviously elongated by comparison with specimens without this treatment. However, for SPCC steel specimens, by comparison with those without water jet peening treatment, fatigue life was a little elongated, almost the same and obviously shortened corresponding to water jet peening treatment time of 5, 10 and 15 minute, respectively. High pressure water jet caused surface corrosion for SPCC low carbon steel, while with almost the same carbon content, copper, chromium and nickel elements increased anti-corrosion properties of SPA-H steel. These resulted in the different fatigue life of SPA-H and SPCC steel. In-situ observation on the crack tips approved above analysis.

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