Fracture and Damage Mechanics V

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Authors: Byeong Wook Noh, Young Woo Choi, Sung In Bae
Abstract: Automobile pedal which is loaded by driver’s input is transmitting load to throttle cable, braking device and clutch device and controlling automobile. Measuring working condition and applying equivalent damage are needed for reliability of developing pedal. The measuring working condition is requiring more investigation with various respects because of widely ranged drivers, road condition and environmental condition. Additionally, when equivalent damage is applied, there are not suitable for test condition if equivalent damage is too high level to apply or unused region. In this study, load history is measured with 95percentile customer. Measured load history is converted to stress history about critical area of pedal by FEM. There are drawn up histogram of pedal cycles and load from stress history with rain flow cycle counting method, calculated relative damage of extended stress history with Palmgren-Miner rule. From the results, calculated total relative damage is applied to calculation method of test time and load. Calculation method for test condition is carried out with three methods which are enforcing with total stress by rain flow cycle counting, representative load and blocked load. Accelerated durability test condition of pedal using with relative damage and acceleration factors are proposed.
Authors: Akbar K. Haghi, Mahyar Arabani, Morteza Shakeri
Abstract: The objective of this research was to advance understanding of the cracking process via laboratory and computational studies and to convey the obtained results in a form that can be utilized for the prediction of cracking in flexible pavements. The primary purpose of this project reported herein was to evaluate the effects of tire cords on the fatigue response of asphalt mix and to develop recommendations for improving the fatigue performance of asphalt pavements. Based on the results presented in this paper, the indirect tensile strength tests can propose as a simple performance test for fatigue cracking of asphalt mixture. The results clearly demonstrate a great potential procedure for the fatigue cracking evaluation of asphalt mixture.
Authors: Byeong Wook Noh, Jung Il Song, Sung In Bae
Abstract: In this study, fatigue strength of load-carrying cruciform fillet welded joints were evaluated using a new method proposed by Yamada, for geometric or structural stress in welded joint, that is, one-millimeter stress below the surface in the direction corresponding to the expected crack path. Validity of the method is verified by analyzing fatigue test results for load-carrying cruciform welded specimens has different size of weld toe radius, leg length and plate thickness reported in literature. Structural stress concentration factor for 1mm below the surface was calculated by finite element analysis for each specimen respectively. When compared to the basic fatigue resistance curve offered by BS7608, the one-millimeter stress method shows conservative evaluation for load-carrying cruciform fillet welded joints.
Authors: Rak Hee Kim, Jung Hoon Son, Dong Sik Bae
Abstract: Ba(MgxNb1-x)O3 nanoparticles were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. Ba(MgxNb1-x)O3 nanoparticles were obtained in the temperature range of 170185 for 4 h. TEM and X-ray diffraction patterns showed that the synthesized particles were crystalline. The average size and size distribution of the synthesized particles were around 100 nm and broad, respectively.
Authors: K.S. Lee, Chang Sik Choi
Abstract: This paper presents a method for determining required shear and flexural strengths associated with structural damage states for various levels of earthquake demand of low-rise RC buildings having a dual lateral-load resisting system. The interaction curves of the required strengths are derived for various ductility ratios based on nonlinear dynamic analyses of the singledegree- of-freedom system. Damage states of buildings controlled by both shear and flexure are evaluated by the procedure outlined by the Japanese Standard. The proposed method predicts reasonably well damage sustained by actual buildings during an earthquake. The proposed method can be used to develop performance-based seismic evaluation and rehabilitation procedures of lowrise RC buildings having a dual lateral-load resisting system.
Authors: K.S. Lee, Chang Sik Choi
Abstract: This paper proposes an efficient structural optimization methods based on the harmony search (HS) heuristic algorithm that treat integrated discrete sizing and continuous geometric variables. The recently developed HS algorithm was conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so derivative information is unnecessary. A benchmark truss example is presented to demonstrate the effectiveness and robustness of the new method, as compared to current optimization methods. The numerical results reveal that the proposed method is a powerful search and design optimization technique for structures with discrete member sizes, and may yield better solutions than those obtained using current methods.
Authors: J.W. Kim, S.W. Kim, K.S. Park, J.K Lee, Byung Ik Kim, Dong Sik Bae
Abstract: Zinc titanate nanoparticles were prepared under high temperature and pressure conditions by precipitation from metal precursors with aqueous ammonium hydroxide. Zinc titanates powders were obtained in the temperature range of 180-230 for 4 h. The phase of synthesized particle with calcined at 800 for 2h. ZnTiO3, Zn2TiO4, Zn2Ti3O8, TiO2, ZnO. The average particle size and distribution of the synthesized zinc titanate nanoparticles were below 100 nm and narrow, respectively.
Authors: Joon Hyuk Song, Su Rok Sin, Hee Yong Kang, Chai Won Kim, Hyu Sun Yu, Sung Mo Yang
Authors: Jan Klusák, Zdeněk Knésl
Abstract: Geometrical and material discontinuities in constructions lead to singular stress concentrations and consequently to a crack initiation. The model of a bi-material wedge makes it possible to analyse such construction points to assess their stability. The presented approach is based on the knowledge of the strain energy density factor distribution in the concentrator vicinity.
Authors: Long Liu, Guang Meng, Hai Huang
Abstract: An approach of damage detection based on ESPI and SVM is proposed. ESPI (Electronic Speckle Pattern Interferometry) is a non-contacting measuring method, which can measure the small static and dynamitic surface deformations and reveal the flaws by looking for flaw-induced deformation anomalies. Support Vector Machine (SVM) is a machine learning algorithm based on statistical learning theory, and it has recently been established as a powerful tool for classification and regression problems. To develop the precision of processing the pattern fringe data, the SVM is introduced to process the patterns corrupted by the laser speckle effect. The SVM is trained with fringe patterns generated from a finite element model and a simple model of the laser speckle effect. The output pattern is obtained to flag whether the damage exists or not. The trained SVM is tested for robustness with model generated test patterns of a flat plate. The results show that this approach is a promising and effective for damage detection.

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