======================================================================                   ENGINEERING NEWS IN BRIEF                         E-Mail Newsletter                                No.52              Issued by the Asian TOP Panel, April 2006            The Chinese Mechanical Engineering Society (CMES)            The Institution of Engineers, Indonesia (PII)            The Japan Society of Mechanical Engineers (JSME)            The Korean Society of Mechanical Engineers (KSME) ======================================================================     According to the agreement made in the 2nd Asian TOP Panel Meeting, the ENGINEERING NEWS IN BRIEF (E-mail newsletter) has now been edited by the CMES for the year 2006. ====================================================================== [Contents] (1) Quantification and Classification of Cracks in Aircraft Multi-layered Structure (Source: CMES) (2) Etching Processing of Microneedls for Drug Delivery (Source: CMES) (3) Numerical Simulation of AZ31B Magnesium Alloy Laser-TIG Hybrid Welding with New Heat Source Model (Source: CMES) (4) Basic Research on Aluminum-Based Materials for High-Pressure-Hydrogen Container (Source: JSME) (5) Laser Microfabrication Using a Bessel Laser Beam (Source: JSME) (6) Traditional Japanese Steel ?Wakou? by Ancient Steelmaking Process?Tat?and Japanese Sword (Source: JSME) (7) A New Flow Control Technique for Handling Infinitesimal Flows Inside a Lab-On-a-Chip (Source : KSME) (8) Fully Plastic Analyses of Unequally Notched Specimens in Bending Moment (Source : KSME) (9) Fatigue Analysis of Fiber-Reinforced Composites Using Damage Mechanics (Source : KSME) ======================================================================== (1) Quantification and Classification of Cracks in Aircraft Multi-layered Structure YANG Binfeng LUO Feilu ZHANG Yuhua College of Mechatronic Engineering and Automation, National University of Defense Technology It is difficult to detect flaws in multi-layered structures of aircraft fuselage lap splices. Pulsed eddy current (PEC) is the effective method that has been demonstrated to be capable of quantifying this defect. Time frequency analysis techniques are used to quantify cracks appearing in aircraft structure. With the purpose of overcoming the problem of low accuracy of PEC in the cracks classification, a new feature, termed as frequency spectrum separating point, is proposed to enhance the accuracy in classification of defects. The agreement between theory and experiment shows that the present method is correct. ======================================================================== (2) Etching Processing of Microneedls for Drug Delivery FU Xin JIAO Feng State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University Although modern biotechnology has produced extremely sophisticated and potent drugs, many of these compounds can not be effectively delivered by convention drug delivery techniques (e.g., pills and injections). Transdermal delivery is an attractive alternative, but it is limited by the extremely low permeability of skin. As the primary barrier of drug delivery is the upper skin in the thickness about 120 μm and the nerves is distributed in the tissue about 200 μm under the upper skin, the arrays of microneedles can be used to penetrate through the upper skin without stimulating the nerves. Therefore, the key technique of this drug delivery method is the fabrications of the of microneedle arrays. The silicon fabrication processing based on the combination of isotropic and anisotropic etching is discussed. ======================================================================== (3) Numerical Simulation of AZ31B Magnesium Alloy Laser-TIG Hybrid Welding with New Heat Source Model LIU Liming CHI Mingsheng Dalian University of Technology A new heat source model of laser-TIG hybrid welding that based upon rotary-Gauss body heat source model and Gauss area heat source is established. The model must consider the physical characteristics of material and hybrid welding because two heat sources are not repeated addition simply. On this basis, the numerical simulation of hybrid welding temperature field and welding seam sectional form is performed and the advice of parameters modification is brought forward. Compared with the experimentally measured value, the result shows that the new model can simulate the AZ31 magnesium alloy hybrid welding accurately. The characteristics of hybrid welding including high welding speed, energy increased and narrow heat affected zone are verified by the calculated result of numerical simulation. ======================================================================= (4)Basic Research on Aluminum-Based Materials for High-Pressure-Hydrogen Container Goroh ITOH, Ibaraki University Hydrogen is being highlighted as an ultimate clean energy since it causes no problem on dryness or global wanning, unlike fossil fuels, while it is generally thought to be dangerous to handle because of its easiness of explosion.?As a part of the huge national project on safe utilization of hydrogen to lighten the regulations concerned. A fundamental study on aluminum alloys for high-pressure-hydrogen container for fuel cell car is being performed. In this study, tensile testing under air environments with controlled humidity is made as a safe and convenient method that is effective to the material screening. This method utilizes a high-fiigacity hydrogen gas generated on the reaction between the metallic aluminum and water vapor and has shown that hydrogen embrittlement does not occur in most aluminum alloys other than 7075-T6. Together with this testing, hydrogen microprint technique is also being conducted. This method can visualize the microscopic location of hydrogen emission from metallic materials using the strong reducing power of hydrogen in metals. ============================================================ (5) Laser Micro-fabrication Using a Bessel Laser Beam Masamichi KOHNO, Kyushu University Yoshihiko MATSUOKA, National Institute of Advanced Industrial Science and Technology Micro-fabrication techniques play an important role in industrial process. Therefore, many kinds of micro-fabrication techniques such as lithography, etching and electrical discharge machining have been investigated. Laser micro-drilling is the technique that uses ablation or fusion process. This method is nowadays widely used for drilling of materials (metals, polymers and glasses). For laser micro-drilling, focusing a laser beam tightly on an object is important. It is possible to focus a laser beam using a conventional convex lens system to its spot diameter comparable to the light wavelength. However, as its focal depth also becomes comparable to the light wavelength, the precise alignment requires that the position of the object be kept within the focal depth. We have found that applying a Bessel beam to micro-drilling has important advantages (for example, a precise alignment is not required) over conventional method since the Bessel beam has a deep focal depth (typically, a few tens mm to 1m). In this report, 1.The principle of a Bessel beam, 2.Laser micro-fabrication with good reproducibility and without precise distance control, 3.Drilling through holes in austenitic stainless steels, were introduced. ============================================================ (6) Traditional Japanese steel Wakou by ancient steel-making process Tatara and Japanese sword Muneo YASO, Yasugi City Wakou Museum Iron and steel-making was introduced into Japan from China and the Korean Peninsula-Abundant charcoal was used for the smelting of the iron sand which, are of good quality in Japan. The process of smelting the iron sand at that time was called the Tatara furnace process. High quality steel was produced from Tatara processing of iron. This method of producing high quality steel can be traced back to more than 1000 years until Meiji period of Japan. The steel produced from Tatara was used by the Japanese for making sword, chisel and kitchen knives.and this has exerted greater influence on the Japanese culture and history. In Chugoku district of Japan,talking about Tatara reminds one about the history of sword manufacturing in Japan. Manufacturing of sword by Tatara still exists in Japan and it is superior to any other method used?for steel-making. This paper reports on steel-making by Tatara, Wakou and the history of Japanese sword which are still active in Shimane prefecture in Japan. ======================================================= (7) A New Flow Control Technique for Handling Infinitesimal Flows Inside a Lab-On-a-Chip Su Dong Han, Guk Bae Kim and Sang Joon Lee Pohang University of Science and Technology A syringe pump or a device using high electric voltage has been used for controlling flows inside a LOC (lab-on-a-chip). Compared to LOC, however, these micro-fluidic devices are large and heavy that they are burdensome for a portable μ-TAS (micro total analysis system). In this study, a new flow control technique employing pressure regulators and pressure chambers was developed. This technique utilizes compressed air to control the micro-scale flow inside a LOC, instead of a mechanical actuator or an electric power supply. The pressure regulator controls the output air pressure by adjusting the variable resistor attached. We checked the feasibility of this system by measuring the flow rate inside a capillary tube of 100 diameter in the Re numbers ranged from 0.5 to 50. In addition, the performance of this flow control system was compared with that of a conventional syringe pump. The developed flow control system was found to show superior performance, compared with the syringe pump. It maintains automatically the air pressure inside a pressure chamber whether the flow inside the capillary tube is on or off. Since the flow rate is nearly proportional to the resistance, we can control flow in multiple microchannels precisely. However, the syringe pump shows large variation of flow rate when the fluid flow is blocked in the microchannel. ======================================================= (8) Fully Plastic Analyses of Unequally Notched Specimens in Bending Moment Chang-Kyun Oh, Yun-Jae Kim, Jin-Moo Pakr Korea University This study proposes slip line fields for bending of unequally notched specimens in plane strain that have a sharp crack in one side and a sharp V-notch in the other side. Depending on the back angle, two slip line fields are proposed, from which the limit moment and crack tip stress fields are obtained as a function of the back angle. Excellent agreement between slip line field solutions with those from detailed finite element limit analysis based on non-hardening plasticity provides confidence in the proposed slip line fields. One interesting point is that, for the unequally notched specimen, the difference between the crack tip triaxial stress for tension and that for bending increases significantly with increasing the back angle. This suggests that such a specimen could be potentially useful to investigate the crack tip constraint effect on fracture toughness of materials. In this respect, the possibility of designing a new toughness testing specimen with varying crack tip constraint is discussed. ============================================================ (9) Fatigue Analysis of Fiber-Reinforced Composites Using Damage Mechanics Jung-Kyu Kim, Dong-Min Lim, Ihn-Soo Yoon, Ki-Weon Kang Hanyang University Due to their intrinsic anisotropy, composite materials show quite complicated damage mechanism with their fiber orientation and stacking sequence and especially, their fatigue damage process is sequential occurrence of matrix cracking, delamination and fiber breakage. In the study, to propose new model capable of describing damage mechanism under fatigue loading, fatigue analysis of composite laminates based on damage mechanics, are performed. The average stress is disassembled with stress components of matrix, fiber and interlaminar interface through stress analysis. Each stress components are used to assess static damage analysis based on continuum damage mechanics (C.D.M.). Fatigue damage curves are obtained from hysteresis loop and assessed by the fatigue damage analysis. Then, static and fatigue damage analysis are combined. Expected results such as stress-cycle relation are verified by the experimental results of fatigue tests. ============================================================ Editor : Tian Ruizhu            The Dept. of Internationa Affairs            Chinese Mechanical Engineering Society

 

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