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Eighth International Conference on Structures Under Shock and Impact, SUSI VIII

作者： Verleysen, P. Degrieck, J. Van Slycken, J. De Cooman, B. Samek, L. Dept. of Mechanical Construction Faculty of Engineering Ghent University Belgium Metallurgy and Materials Science Faculty of Engineering Ghent University Belgium

Split Hopkinson bar set-ups are considered to be valuable, if not indispensable, to study the strain rate dependent mechanical behaviour of materials. In recent years results of SHB experiments on a wide range of materials have been reported in literature. Given their importance for crash relevant applications, special attention has been paid to the tensile properties of steel sheets used in the automotive industry. For tensile experiments most often dogbone-shaped geometries are used, however with widely divergent dimensions. In this contribution results of an extensive experimental study on the influence of the specimen geometry are presented. Based on data found in literature, seven geometries are defined and subjected to strain rates ranging from 650/s to 1250/s. The material considered is a TRIP (TRansformation Induced Plasticity) steel sheet. An advanced measurement technique is used to monitor the true distribution of the deformation along the length of the specimen. It is shown that the influence of the specimen geometry on the test results cannot be neglected, and that this can mainly be attributed to the fact that the true distribution of the deformation deviates from the assumed distribution.

关键词： Bars (metal)

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Hypersonic plasma particle deposition of nanostructured coatings and micropatterns

Hypersonic plasma particle deposition of nanostructured coat...

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3rd ASME Integrated Nanosystems Conference - Design, Synthesis, and Applications

作者： Hafiz, J. Mukherjee, R. Wang, X. Mook, W. Heberlein, J.V.R. McMurry, P.H. Gerberich, W.W. Girshick, S.L. Dept. of Mechanical Engineering University of Minnesota Minneapolis MN United States Dept. of Chemical Engineering and Materials Science University of Minnesota Minneapolis MN United States

ISBN: (纸本)0791841774

A one-step method called hypersonic plasma particle deposition was developed to produce and deposit nanoparticles using a thermal plasma reactor. Particle synthesis was achieved by dissociating vapor phase reactants in the plasma, and quenching the hot gas in a supersonic nozzle expansion. In-situ particle size distribution measurements showed particle size distributions peak around 10 nm under typical operating conditions. Scanning electron microscopy (SEM) results confirm the presence of nanostructured grains, and x-ray diffraction (XRD) results show the presence of crystalline TiN and TiSi 2, while X-ray photoelectron spectroscopy (XPS) measurements illustrate the presence of amorphous Si3n4.

关键词： Hypersonic aerodynamics

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Static and dynamic mechanical properties of extracellular matrix synthesized by cultured chondrocytes

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materials science and engineering C 2004年第3期24卷 425-429页

作者： Miyata, Shogo Furukawa, Katsuko S. Ushida, Takashi Nitta, Yasuo Tateishi, Tetsuya Biomedical Engineering Laboratory Dept. of Mechanical Enginieering Graduate School of Engineering Hongo 7-3-1 Bunkyo Tokyo 113-8656 Japan Biomaterials Center Natl. Inst. for Materials Science Japan

Recently, an approach to restore cartilage defects, culturing autologous chondrocytes in vitro to create a three-dimensional tissue and then implanting the cultured tissue, has been developed. In this kind of approach, it is important to study whether the extracellular matrixes synthesized by cultured chondrocytes have appropriate mechanical property. In this study, we attempted to evaluate in detail mechanical properties of the extracellular matrix synthesized by chondrocytes in vitro. Therefore, we cultured bovine chondrocytes in agarose gel and assessed the changes in not only static but also dynamic mechanical properties during long-term culture. In addition, to assess the mechanical property of the extracellular matrix synthesized by chondrocytes only, we calculated the volume ratio of the extracellular matrix in agarose gel from the cross section and estimated the static Young's modulus of the extracellular matrix synthesized by cultured chondrocytes based on the Rule of Mixture. As a result, both the equilibrium aggregate modulus and dynamic Young's modulus of chondrocyte/agarose disks increased with time. The value of calculated modulus was larger than that of the pericellular matrix of cartilage explant. In conclusion, the biomechanical property of chondrocyte/agarose constructs and the matrix synthesized by chondrocytes were assessed in detail. © 2004 Elsevier B.V. All rights reserved.

关键词： Cartilage

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Relation between the Three-dimensional Flow Structure and Aerodynamic Sound Generated from Inclined Circular Cylinder

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Journal of Thermal science 2004年第2期13卷 127-132页

作者： Mitsuru SHINGAI Yasutake HARAMOTO Kazuyoshi MATSUZAKI Mizue MUNEKATA Hideki OHBA Dept. of Mechanical Engineering and Materials Science Kumamoto University Kurokami 2-39-1 Kumamoto 860-8555 Japan Mitsui Miike Machinery Co. LTD Asahi-machi 2-28 Ohmuta Fukuoka 836-8588 Japan

The major causes of the sound pressure level (SPL) variation due to the changes of the inclined angle of a circular cylinder and the aspect ratio (ratio of distance between endplates to cylinder diameter) were investigated. The velocity fluctuation of the wake and the surface pressure fluctuation of the cylinder were measured in a low noise wind tunnel to find the correlation length, coherent output power and Strouhal number. The results show that the changes of these values qualitatively correspond with the change of SPL. Flow visualization tests are performed to clarify the variation of wake in relation with inclined angle and aspect ratio. It is found that the spanwise structure of Karman’s vortex street is broken down by the upward flows generated around the bottom endplate, and the degree of the interference between the upward flow and Karman’s vortex street is smaller when the aspect ratio is larger.

关键词： aerodynamic sound correlation length coherent output power Strouhal number flow visualization.

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Three-dimensional occupancy grids with the use of vision and proximity sensors in a robotic workcell

Three-dimensional occupancy grids with the use of vision and...

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2004 ASME International mechanical engineering Congress and Exposition, IMECE

作者： Kumar, Manish Garg, Devendra P. Dept. of Mechanical Engineering and Materials Science Duke University Box 90300 Durham NC 27708-0300 United States

This paper discusses the use of multiple vision sensors and a proximity sensor to obtain three-dimensional occupancy profile of robotic workspace, identify key features, and obtain a 3-D model of the objects in the work space. The present research makes use of three identical vision sensors. Two of these sensors are mounted on a stereo rig on the sidewall of the robotic workcell. The third vision sensor is located above the workcell. The vision sensors on the stereo rig provide information about three-dimensional position of any point in the robotic workspace. The camera to robot calibration for these vision sensors in stereo configuration has been obtained with the help of a three-layered feedforward neural network. Squared Sum of Difference (SSD) algorithm has been used to obtain the stereo matching. Similarly, camera to robot transformation for the camera located above the work cell has been obtained with the help of a three-layered feedforward neural network. Three-dimensional positional information from vision sensors on stereo rig and two-dimensional positional information from a camera located above the workcell and a proximity sensor mounted on the robot wrist have been fused with the help of Bayesian technique to obtain more accurate positional information about locations in workspace. Copyright © 2004 by ASME.

关键词： Robotics

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The adaptive piezoelectric microsensoriactuator for active control of microcantilevers

The adaptive piezoelectric microsensoriactuator for active c...

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2004 ASME International mechanical engineering Congress and Exposition, IMECE

作者： Burns, Steven Robert Cole, Daniel G. Clark, Robert L. Adaptive Systems and Structures Lab. Dept. of Mechanical Engineering and Materials Science Duke University Durham NC 27708 United States

The adaptive piezoelectric sensoriactuator is modified for use at the microscale to facilitate non-contact mode imaging of a microcantilever MEMS device in atomic force microscopy. The sensoriactuator is a truly colocated (sensor and actuator occupy exactly the same position on the structure) sensor/actuator device that uses a hybrid digital and analog design to drive a structure while simultaneously sensing the mechanical response. Using a piezoelectric material to both sense and actuate simultaneously is problematic because of the difficulty in resolving the sensory (mechanical) and actuator (electrical) parts of the output signal. Implementation of the adaptive piezoelectric sensoriactuator at the microscale results in a system with electrical quantities that are vastly reduced or increased from typical macroscale values, requiring more precise components and more careful design and construction of analog circuitry. For example, a typical microcantilever piezoelectric has a capacitance of on the order of 100 pF with an impedance at 50 kHz nearly 32 kΩ. The signal levels are significantly smaller with a typical piezoelectric current on the order of 100 nA. Thus, environmental noise can overwhelm signals in the system mandating the use of high precision operational amplifiers featuring ultra-low bias currents (±30 fA) and careful guarding or shielding of all circuitry. As reported in this paper, the adaptive piezoelectric microsensoriactuator has been successfully used to simultaneously sense and actuate while imaging using non-contact mode. The self-sensing microcantilever was successfully tested to produce a surface image using the microsensoriactuator to measure the movement of the microcantilever. The RMS value of the microsensoriactuator output is compared with the desired RMS output and the difference is used to drive an active resonance response controller. The active resonance response controller determines the control signal required to augment or attenuat

关键词： Piezoelectric devices

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Directed assembly of metal oxide nanobelts with microsystems into integrated nanosensors

Directed assembly of metal oxide nanobelts with microsystems...

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2004 ASME International mechanical engineering Congress and Exposition, IMECE 2004

作者： Yu, Choongho Hao, Qing Shi, Li Kang, Dae-Jin Kong, Xiangyang Wang, Z.L. Dept. of Mechanical Engineering Center for Nano and Molecular Science and Technology University of Texas at Austin Austin TX 78712 Dept. of Mechatronics Engineering Korea Polytechnic University Shiheung Kyunggi Korea Republic of School of Materials Science and Engineering Georgia Institute of Technology Atlanta GA 30332

Single-crystalline tin dioxide (SnO2) nanobelts have been assembled with microfabricated suspended heaters as low-power, sensitive gas sensors. With less than 4 mW power consumption of the micro-heater, the nanobelt can be heated up to 500°C. The electrical conductance of the heated nanobelt was found to be highly stable and sensitive to toxic and inflammable gas species including dimethyl methyl phosphonate (DMMP), nitrogen dioxide (NO2), and ethanol. The experiment is a step towards the large scale integration of nanomaterials with microsystems, and such integration via a directed assembly approach can potentially enable the fabrication of low-power, sensitive, and selective integrated nanosensor systems. Copyright © 2004 by ASME.

关键词： Nanostructured materials

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Aggregate formation of bone marrow stromal cells by rotation culture

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materials science and engineering C 2004年第3期24卷 421-424页

作者： Suenaga, Hideyuki Furukawa, Katsuko S Ushida, Takashi Takato, Tsuyoshi Tateishi, Tetsuya Dept. of Oral/Maxillofacial Surgery Graduate School of Medicine University of Tokyo 7-3-1 Hongo Bunkyo Tokyo 113-8655 Japan Biomedical Engineering Laboratory Department of Mechanical Engineering Graduate School of Engineering Tokyo Japan Biomaterials Center Natl. Inst. for Materials Science Ibaraki Japan

The rotation culture method adopted in our experiments induced numerous aggregates of bone marrow stromal cells (BMSCs);this method augments the frequency of cell-cell contacts and thereby facilitates cell aggregation. Cell condensation plays an important role in differentiation and development. Cell adhesion molecules and the extracellular matrix (ECM) are important regulators of cell adhesion and apoptosis. Therefore, we investigated not only whether aggregates of BMSCs could be formed by rotation culture, but also whether expression of N-cadherin and β1-integrin was involved in the formation of cell aggregates and in the avoidance of apoptosis. The culture medium was supplemented with fibroblast growth factor-2 (FGF-2) or transforming growth factor-β1 (TGF-β1), expected to prompt the formation of cell aggregates. This study enabled the formation of numerous aggregates of BMSCs by rotation culture. Reverse transcription- polymerase chain reaction (RT-PCR) analysis indicated that FGF-2 and TGF-β1 increased expression of N-cadherin and β1-integrin. Morphological analysis by light microscopy indicated that FGF-2 and TGF-β1 increased cell-cell adhesion and formation of cell aggregates. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay indicated that FGF-2 and TGF-β1 prevented apoptosis. These results suggest that numerous aggregates of BMSCs were formed efficiently by rotation culture since FGF-2 and TGF-β1 increase cell-cell adhesion and rotation increases cell-cell contact. © 2004 Published by Elsevier B.V.

关键词： Cells

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Research of the Effects of Electron Focused Electric Field upon an Enhanced Glow Discharge Plasma Ion Implantation

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材料保护 2004年第S2期37卷 141-143页

作者： LI Liu-he Wu Yong-qin ZHANG Yan-hua CAI Xun Chu Paul K School of Mechanical Engineering and Automation Beijing University of Aeronautics and Astronautics. Beijing 100083 School of Materials Science and Technology Shanghai Jiao Tong UniversityShanghai 200240 P. R. China School of Mechanical Engineering and Automation Beijing University of Aeronautics and Astronautics. Beijing 100083 School of Materials Science and Technology Shanghai Jiao Tong UniversityShanghai 200240 P. R. China Dept. of Physics & Materials Science City University of Hong KongKowloon Hong Kong

A new Enhanced Glow Discharge Plasma Ion Implantation methods are introduced, in which the plasma are produced by the self glow discharge excitated by high negative voltage bias. The electric field is designed to a electron focusing mode by using a small area hollow anode and a large area sample holder cathode. The pattern of equipotentials of the electric field are calculated through finite-element method. By using the special electron-focusing field, the self glow discharge are enhanced and provide denser ions to implanted into the substrate.

关键词： PBII enhanced glow discharge plasma ion implantation finite-element

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An Effort for Improving Transport Efficiency of Plasma in Acurved Magnet Filter

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材料保护 2004年第S2期37卷 125-127页

作者： Hu Yawei LI Liuhe XU Ming LIU You-ming CAI Xun CHU P K School of materials science and technology Shanghai Jiao Tong University Shanghai 200240 School of materials science and technology Shanghai Jiao Tong University Shanghai 200240 School of Mechanical Engineering and Automation Beijing University of Aeronautics and Astronautics. Beijing 100083 P. R. China Dept. of Physics & Materials Science City University of Hong Kong Kowloon Hong Kong

In this article an effort was made to increase the efficiency of plasma transmission by using a additional wire netting between the substrate and the filter duct which was floated. The substrate was biased with a negative voltage or connected to anode, respectively. the parameters of the exited plasma and ion saturation current are examined by Langmuir probe and current collector plate. It was found that When the wire netting is connected to apositive voltage and the substrate is biased with a negative voltage, the ion saturation current and ion density had obviously improvement . The result proved that this method could improve the ion saturation current and ion density.

关键词： curved magnet filter Langmuir probe ion saturation current ion density

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