Progresses in Fracture and Strength of Materials and Structures

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Authors: Choon Yeol Lee, Il Sup Chung, Young Suck Chai
Abstract: A pressure plate, a component of the clutch system, was analyzed by two-dimensional and three-dimensional finite element method under three major load conditions of thermal loading due to temperature distribution, centrifugal force and contact pressure of diaphragm spring. The results show that the effects of thermal loading and contact pressure of diaphragm spring are important, which suggests the direction of design improvement. A hub plate was also analyzed with finite element modeling. A stress concentration occurs around the fillet region around the window in the plate where the fracture analysis is executed to find the stress intensity factors. These results will be used as the fundamental data for design improvement of the shapes of pressure plates and hub plates.
Authors: Zhe He Yao, Xin Li, Zi Chen Chen
Abstract: Self-chatter is a serious problem in cutting process. This paper aims to solve the problem by establishing time series model of vibration acceleration signal in cutting process based on Hidden Markov Model (HMM) technology and achieve the purpose of chatter recognition and prediction. Features which can indicate cutting state are extracted from the acceleration signal. HMM parameters are obtained by model training, and the reference models database is built. Then cutting state recognition is performed according to the feature matching level. Simulations and experiments are conducted, and the results show that the proposed method is feasible and it could get high recognition
Authors: Hong Sheng Su, You Peng Zhang
Abstract: To improve the accuracy and overcome the flaws of single neural network, an integrated neural classifier for stream turbine vibration fault identification is proposed based on particle swarm optimization (PSO) in the paper. The method firstly establishes diagnosis decision table of stream turbines from fault sources to fault symptoms based on wavelet package decomposition technique to faults wave-shape. Then the discrete decision table is acquired by quantifying attribute values in decision table using information entropy, a simplified decision table then is generated by rough set reduction. Based on it, several neural networks are applied to identify steam turbine faults at the same time, and their results are integrated with PSO-based. Both simulation and trial in stream turbine damage identification indicate that the proposed method has higher identification rate and shorter training time as well as excellent generalized ability, and is an ideal pattern classifier.
Authors: Yong Gang Zhao, Wei Dong Zhao, Shi Rong Li, Lian Sheng Ma
Abstract: Based on the von Kármán classical nonlinear plate theory, nonlinear axisymmetric vibrations of a clamped thin circular plate subjected to transverse harmonic load are investigated. Effects of static deformation on the vibration responses are considered. Harmonic motion is assumed. The time variable is eliminated and the partial differential equations are converted into a system of nonlinear ordinary differential equations by employing a Kantorovich time averaging method. The resulting nonlinear ordinary differential boundary-value problem is solved numerically by using shooting method. Effects of static-dynamic load on the transverse deflection, frequencies and amplitudes are examined in details. The resonance phenomenon is discussed emphatically.
Authors: Fei Xu, Meng Hui Zhu, Zhong Bin Tang, Yu Long Li
Abstract: The mechanical properties of various parts of the welding-line material are different, while they play very important role in the welding structures, such as the differences of the melted part and the temperature-affected part. In this paper, a non-contacting laser based technique, ISDG (Interference Strain Displacement Gauge) method, is applied to find out these property differences on very small specimen. The testing is very successful and the whole stress-strain curves in such small scale are obtained on different parts of the welding-line material. The soften phenomena of the temperature-affected part is observed by the comparison of the Young’s modulus and yield stress between the melted part and the temperature-affected part.
Authors: Sung Cheol Yoon, Chang Sung Jeon, Jeong Guk Kim
Abstract: This paper describes a carbody structural analysis and the result of its loading test. The purpose of this study is to evaluate the safety and functionality of the body structure operating under maximum load. Aluminum alloy was used as the body structure’s material. The body structure consisted of side frame, under frame, roof frame, and end frame. Of these components, the side frame and under frame were the most important components considering the vehicle and passenger loads. Both structural analysis and loading test were performed under the condition based on "Performance Test Standard for Electrical Multiple Unit" with the reference code JIS E 7105. The test results showed that the body structure is safe and stable under the condition of designed load.
Authors: Li Hong Chen, Jian Yang, You Ren Yuan, Tao Sun
Abstract: Linear and nonlinear shear strength models of rockfill, and the safety factor criterion of nonlinear shear strength were discussed in this paper. The slope stability of 261.5 m high Nuozhadu rockfill dam was analyzed with three different shear strength models. The safety factors are almost equal and the positions of potential failure surface are similar. It is found that the allowable safety factor base on linear criterion in the existing code can be used without any change when applying nonlinear shear strength rules.
Authors: Li Hong Chen, Xiao Guang Zhou, Yin Qi Wei
Abstract: The deformation and strength characteristic of rockfill is different when it is dry or wet. The wetting effects should be a major factor in the long-term settlement of a rockfill dam. The 160 m high Yellow River Xiaolangdi dam is a rockfill dam with inclined core clay. Moistening laboratory tests were carried out to investigate the deformation and strength characteristic of the rockfill in the Xiaolangdi dam. Based on the test results, two-dimensional consolidation numerical simulations on the dam employed nonlinear stress strain constitutive model were conducted to investigate the effects of wetting on the deformation performance of the dam.
Authors: Yeon Su Kim, Sung Hyuk Park, Rag Gyo Jeong, Jai Kyun Mok
Abstract: This study was aimed to verify the performance and stability of the 3rd rail type power collector for rubber-tired vehicles. Performance (power interruptions), durability (stresses), stability (vibrations and contact force variations) of the developed power collector were measured and analyzed, while the rubber-tired vehicle ran at various speeds on the test track(about 2.4km).
Authors: Ming Tu Ma, Zhi Gang Li, Hong Liang Yi, Hao Zhang
Abstract: The crankshafts of semi-finished products were manufactured by two processes: as-cast followed by normalizing and iron mould with sand liner as-cast. Then those were machined and nitridized followed by the bending fatigue test. At last mechanical properties and impact properties of sampled crankshafts were tested. The mechanical properties are similar in the crankshafts treated by both of the processes, however, the bending fatigue limits of as-cast spherical graphite iron crankshafts are much higher than that of normalized spherical graphite iron crankshafts, whose crack producing work and extending work is higher as well. The higher extended work is considered to relate to the oeil-de-boeuf ferrite and graphite structure and pearlite in as-cast spherical graphite iron crankshafts, while the normalized ones with lower fatigue limit value are composed of spherical graphite and pearlite. Cracks having initiated in the graphite, the tips of cracks can be blunted and the crack propagation can be impeded efficiently by ferrites surrounding the graphite in this structure.

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