Experimental Mechanics in Nano and Biotechnology

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Authors: Young Jin Choi, Young Shin Lee, Se Hoon Lee, Je Wook Chae, Eui Jung Choi, Suk Kyun Hong
Abstract: The hit rate is affected by the shooting impact of the human-rifle system. The impact response of the human-rifle system is determined mainly by the geometrical parameters and contact boundary conditions. In this study, the height and weight of the considered human model are 170 cm and 60 kg, as these parameters mirror 50 per cent of Korean males in their twenties. The rifle model is applied on the K-2. The impact path analysis of three typical shooting postures: the standing, kneeling and prone shooting postures is performed with experimental impulse-time history during a shooting test. The biomechanical response such as impact transfer path, force history and displacement history are investigated.
Authors: Hyung Soo Ahn, Il Hyung Park, Denis DiAngelo
Abstract: The biomechanical changes brought on by spine fusion and the artificial disc designs to restore physiologic motion were studied by using a cervical spine computer model. Fusion increased the motion compensation at the adjacent segment during flexion and extension. The global rotational stiffness and segmental disc forces were also increased after fusion. Among the three prosthetic disc designs, the PDD-III (5-DOF spherical joint in plane parallel with the C5-C6 disc level) maintained the normal motion and minimized load build up of adjacent segment.
Authors: T. Tang, S.Q. Wang, Zhuo Zhuang
Abstract: As one kind of the most important cells in human body, myocardial cell becomes the focus of attention, not only the biologist but also the researchers of mechanics. A new viscoelastic constitutive model of the living myocardial cell is developed based on the micropipette suction experiment in which the surface of the cell is aspirated into a small glass tube while tracking the leading edge of its surface. Some numerical simulations are presented by finite element to model the whole process of micropipette suction of the myocardial cell. Meanwhile, a model cell with both mechanical behavior and physiological function is being developed, to prove the viscoelastic constitutive model and to predict more results of myocardial cell under different physiology conditions.
Authors: Kazuo Arakawa, Toshio Mada
Abstract: Dynamic crack propagation in PMMA was studied using the method of caustics in combination with a Cranz-Schardin type high-speed camera. Three different types of specimen geometries were employed to achieve the crack acceleration, deceleration and re-acceleration process in one fracture event. Dynamic stress intensity factor KID and the crack velocity were evaluated in the course of crack propagation to obtain the relationship between KID and the velocity The effect of crack acceleration and deceleration on the KID -velocity relations was examined.
Authors: Song Heo Koo, Young Shin Lee
Abstract: The purpose of the present study is to evaluate thermal shock properties of the ATJ graphite using laser irradiation techniques. Cracks of thermal shock specimens are initiated by maximum tensile stress field. Thermal shock resistance of the ATJ graphite is correlated with thermal parameter and mechanical property. To simulate the thermal stress conditions of rocket nozzle throat for the evaluation of the thermal shock resistance of ATJ graphite, the laser irradiation was applied at the central area of disk specimen. Thermal shock resistance was related to the geometry, the maximum stress, and the thermal and mechanical property. Also the analyses of transient temperature and thermal stress were performed by the finite element method with nonlinear code ABAQUS. Analyses were specially performed for several kinds of shape to determine the minimum power density which could be cracked the specimen. The shape of the thermal shock specimen which was cracked under the lower power density was obtained and the result will be proved to the test.
Authors: Young Suk Kim, Sang Bok Ahn, Kang Soo Kim, Yong Moo Cheong
Abstract: Threshold stress intensity factor or KIH required to initiate a delayed hydride crack in the axial direction of a Zr-2.5Nb tube was determined at temperatures of 160 oC to 280 oC. KIH remained constant at temperatures from 160 to 250 oC, increased with an increasing temperature in excess of 280 oC using a load decreasing method. To correlate KIH and dislocation twins, tensile tests were conducted on the Zr-2.5Nb tube and textural changes during tensile tests were investigated using an X-ray diffractometer. The extent of the twins increased from 150 to 300 oC and then decreased at temperatures in excess of 300 oC with no twins occurring at 350 oC. Temperature dependencies of KIH and a temperature limit for delayed hydride cracking were discussed with cracking of hydrides by the twins. This study provides supportive evidence to the feasibility of Kim’s DHC model.
Authors: Hui Ru Dong, Quan Liang Liu, Zhi Guo Zhang, Yun Xiang Cheng
Abstract: Experimental methods that can be used in three-dimensional mixed mode fracture researches are investigated. The methods are capable of determining the initiation load, maximal load, crack tip opening displacement, crack tip slipping displacement and initiation angle of the mixed mode crack simply and conveniently. As an example, the effect of thickness on mixed-mode I/II fracture of a kind of aluminum alloy is revealed by the methods.
Authors: Jae Hoon Kim, Duck Hoi Kim, Nam Su Rho, Young Shin Lee, Song Heo Koo, Soon Il Moon
Abstract: The objective of this study is to evaluate the mechanical properties of static, quasidynamic and dynamic fracture toughness of glass-filled ceramic as promising structural material for a dome port cover of a ramjet engine system. Static and quasi-dynamic tests were carried out using SEPB (Single Edge Pre-cracked Beam) specimens. Static and dynamic fracture toughness tests were also performed using ASTM and strain gage methods with SENB (Single Edge Notched Beam) specimens machined with various notch radii. The critical notch radius was evaluated. Below the critical notch radius, the static fracture toughness of the SENB specimen well agreed with that of the SEPB specimen.
Authors: Yoon Suk Chang, T.R. Lee, Jae Boong Choi, Young Jin Kim, Min Chul Kim, Bong Sang Lee
Abstract: The objective of this paper is to investigate failure characteristics of SA508 carbon steel in ductile-brittle transition temperature region. To achieve this goal, a series of finite element analyses as well as fracture toughness tests are performed for pre-cracked V-notch specimens. An assessment of failure probabilities is, then, carried out employing Weibull stress models with different rank probability options. Finally, a prototype of toughness scale diagram is derived through comparison of estimated fracture toughness data with those for compact tension specimens. The present results can be utilized to found a basis of realistic integrity evaluation on major nuclear components containing defect.
Authors: Yoon Suk Chang, T.R. Lee, Jae Boong Choi, Chang Sung Seok, Young Jin Kim
Abstract: In this paper, the applicability of local approach is examined for SA515 Gr.60 nuclear steel through a series of finite element analyses incorporating modified GTN and Rousselier models as well as fracture toughness tests. To achieve the goal, fracture toughness test data of standard compact tension (CT) specimens are used for calibration of micro-mechanical parameters. Then, from finite element analyses employing the calibrated parameters, fracture resistance (J-R) curves of CT specimens with different crack length to width ratio, with different thickness and with/without 20% side-grooves are predicted. Finally, suitability of the numerically estimated J-R curves was verified by comparison with the corresponding experimental J-R curves.

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