Papers by Keyword: Void

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Authors: Kazuya Mori, I. Torigoe, M. Tokunaga, S. Hatanaka, Y. Shiramizu
Authors: G. Trumpy, M.D. Bentzon
Authors: Matteo Bosi, Claudio Ferrari, Daniel Nilsson, Peter J. Ward
Abstract: In this work we have studied the carbonization of 3C-SiC on misoriented Si substrates, using different thermal ramp rates and shapes. We observed that the heating rate (°C/sec) from carbonization temperature to film growth temperature plays a major role in controlling the void density. Moreover, void formation can be eliminated by the introduction of silane at different temperatures during the heating ramp. The studies were performed on a small research reactor and the results were successfully transferred to a production scale reactor, aimed to the production of 3C-SiC power devices manufactured on 100 and 150 mm Si substrates.
Authors: Fang Ran Zhao, Jia Lin Cao, Ning Wang
Abstract: Three-dimensional finite element analysis was made on the transverse joint stress state of the concrete pavement slab with void underneath using ANSYS. The transfer effect of dowel bar was discussed with aircraft loaded in the joints. The influence rule of load transfer effect under different dowel bar spacing and dowel bar cross section dimension was compared. Based on the results of finite element analysis, this paper had carried on the experimental study on stress-transferring effect on concrete pavement joints with different location of the dowel bar. The influencing factors of pavement slab transverse joint with void underneath and the resistance of pavement damage on the joint was analyzed. Theoretical analysis showed that in order to reinforce the resistance capacity of local cavity on concrete pavement joint, the largest spacing of transverse dowel bar set shall not be more than 45cm, and the main factors influencing the resistance void ability on the joint are top reaction modulus, coefficient of cavity, the concrete elastic modulus and coefficient of transverse reinforcement.
Authors: Peng Li, Yu Bo Tao, Feng Hu Wang, Sun Guo Wang
Abstract: For further researching the structural characteristics of Orientated strand board (OSB) mat, a three-dimensional model was developed using computer-aided design (CAD) technology to simulate behaviors of individual strands in the mat-forming process. This model provided a more realistic description of the mat structure than the previous simulations in using varied strand geometry and different types of strand orientation, defining strand location, and solving the problem of edge effect. This model can be used to analyze the impact of strand orientation on the number of strand overlaps, and to identify the relationship of strand orientation and the horizontal voids distribution in the mat. Information provided by this model is the basis of further studying the effect of the mat formation on panel void characteristics, and the relationship of the voids volume to panel properties.
Authors: Shin Yamamoto, Hiroyuki Toda, L. Qian, Tomomi Ohgaki, Masakazu Kobayashi, Toshiro Kobayashi, Kentaro Uesugi
Abstract: High resolution phase contrast imaging technique has been applied to obtain clear crack images together with the detailed of microstructural features in a cast aluminum alloy. Crack opening/closure, crack extension and damage evolution in the vicinity of a crack-tip is observed three-dimensionally (3-D). 3-D image analysis is performed to evaluate void initiation and growth near the crack-tip. The information on physical displacement of each microstructural feature is provided for analyzing local crack driving forces at crack front. This technique has been identified to provide a unique possibility to quantitatively interpret the 3-D cracking behavior in bulk materials.
Authors: Chung Ming Tan, Yeau Ren Jeng, Yung Chuan Chiou
Abstract: This paper employs static atomistic simulations to investigate the effect of a void on the nanoindentation of Cu(111). The simulations minimize the potential energy of the complete system via finite element formulation to identify the equilibrium configuration of any deformed state. The size and depth of the void are treated as two variable parameters. The numerical results reveal that the void disappears when the indentation depth is sufficiently large. A stress concentration is observed at the internal surface of the void in all simulations cases. The results indicate that the presence of a void has a significant influence on the nanohardness extracted from the nanoindentation tests.
Authors: M. Noda, Hideharu Shimizu, Kunio Funami, H. Mori
Abstract: Magnesium alloys show promise in meeting the demand for materials of lighter weight and higher rigidity. Mg alloys are hard to process and normally require grain refining for improved formability and mechanical properties. To process these fine-grained Mg alloys effectively, it is important to relate their load stress and mechanical properties to changes in their microstructures. Using a biaxial tensile machine and cruciform specimens, to evaluate the mechanical properties, microstructure, and plasticity, in a high temperature biaxial stress state, used of AZ31 Mg alloy sheet. With biaxial deformation, grain boundary slide occurred more frequently than with uniaxial deformation, causing grain boundary separation and formation of micro-voids between the grains. In the vicinity of the cracks and at the locations of grain boundary separation, although deformation temperature at higher than the recrystallization temperature, fine grains (about 2 )m) showing in duplex grain structures were formed locally. The formation of duplex grain structures as a result of local formation of fine grains during the deformation process is a major issue to be solved from the viewpoint of plasticity processing.
Authors: Michael Uhrmacher
Abstract: The PAC-technique always claims to test the micro-surrounding of the probe atoms. Typically, the samples are macroscopic and more or less homogeneous and there is no debate about the usefulness of the method: substitutional sites, trapped vacancies or phase transitions are easily seen. Even the PAC-“fingerprint” of an amorphous material is known. In case of inhomogeneous samples, perhaps made out of different constituents, the question arises whether the PAC can contribute to the understanding of such materials or not. The article will show the different ways to introduce the probe atoms into the samples and discuss then the influence of these histories on the final site of the probe in the sample. In general, diffusion tends to place the probes into grain boundaries, whereas implantation reaches the bulk. This becomes important for nano-materials with their high fraction of internal surfaces. As a second, important difference for possible experiments the spatial distribution of the probes has to be considered. Implantation leads to a Gaussian shaped depth distribution of the probes. This corresponds – in a certain region – to a 3-dimensional distribution of probes in the sample, used e.g. when doping a semiconductor. In the production of special sensors (which apply e.g. the giant magnetoresistance (GMR) effect) one needs a different package, thin films (1-2 mono-layers). To apply PAC here, the probes have to be introduced during the fabrication of such a sensor. In these cases the probes have to be placed within a plane of nano-scale thickness.
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