The Experts below are selected from a list of 214503 Experts worldwide ranked by ideXlab platform
Akira Todoroki - One of the best experts on this subject based on the ideXlab platform.
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Damage Identification of Woven Graphite/Epoxy Composite Beams using the Electrical Resistance Change Method
Journal of Intelligent Material Systems and Structures, 2006Co-Authors: Yoshiyasu Hirano, Akira TodorokiAbstract:This study examines the damage identification for woven graphite/epoxy composite beams by means of an electrical Resistance Change method. The method has been proposed by the authors and successfully applied to cross-ply and quasi-isotropic laminates; the method has yet to be applied to woven laminates. In many practical structures, woven plies are adopted to prevent peeling of the surface layer. Therefore, a woven graphite/epoxy composite is selected as the target material of the electrical Resistance Change method to identify the damage. Beam type specimens consisting of woven laminates are the focus of this article. For the purpose of identification, the response surface is adopted as a solving method for the inverse problem. As a result, the method shows an excellent performance for estimating delamination crack locations and sizes.
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matrix crack detection of cfrp using electrical Resistance Change with integrated surface probes
Composites Science and Technology, 2006Co-Authors: Akira Todoroki, Yoshinobu Shimamura, Kazuomi Omagari, Hideo KobayashiAbstract:For the cryogenic tanks of next generation reusable launching vehicles, the laminated composite tank is one of the key technologies. For composite fuel tanks made from laminated carbon fibre reinforced polymers (CFRP), matrix cracking is a significant problem that may cause fuel leakage. In the present paper, an electrical Resistance Change method with integrated probes on a single side of the surface of a CFRP composite structure is adopted to detect the matrix cracking of the laminated composites. For a fuel tank structure made of a CFRP laminate, we cannot mount electrical probes on the end of structure or on the inside of the tank structure. We have to mount all probes only on the outside surface. The present method used finite element analyses (FEA) to search for the best placement of probes for matrix crack detection using a rectangular plate. To simulate the tank structure, all probes are placed on a single surface of the CFRP plate specimen. The present study adopted a four-probe method for measuring the electrical Resistance Change. The FEA revealed that the electrical Resistance increases linearly with increase in the number of matrix cracks inside of the probes. By means of thin CFRP cross-ply laminate, the method was experimentally confirmed to be useful for detecting matrix crack density between the probes. Residual electrical Resistance at the completely unloaded condition increased with increase in matrix crack density. Measurements of the residual electrical Resistance enabled us to detect the matrix crack density without loading.
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Detectability of Bearing Failure of Composite Bolted Joints by Electric Resistance Change Method
Key Engineering Materials, 2006Co-Authors: Yoshinobu Shimamura, Akira Todoroki, Keiko Oda, Masahito UedaAbstract:Bolted joints are widely used for composite structures. As is well known, excessive bearing load gives rise to bearing failure at hole boundaries. Detecting bearing failure is important for assuring integrity of composite structures. Since conventional nondestructive inspection methods are expensive, cumbersome, time-consuming, and not suitable for health monitoring, a simple, low-cost inspection method for bearing failure must be developed. Authors have demonstrated the feasibility of detecting bearing failure by using an electric Resistance Change method. In this study, more detailed analyses were carried out to investigate the detectability in terms of the damage size and the distance between damage and electrodes. The results show that bearing failure of less than 10mm square causes the electric Resistance Change of a few hundred ppm and thus can be easily detected, and that the electrodes can be mounted more than 10 mm far from a bolt hole.
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electrical Resistance Change method for monitoring delaminations of cfrp laminates effect of spacing between electrodes
Composites Science and Technology, 2005Co-Authors: Akira Todoroki, Miho Tanaka, Yoshinobu ShimamuraAbstract:The present study employs an electrical Resistance Change method for monitoring delamination. The authors have found that the electrical Resistance Change method using response surfaces is very effective in identify delaminations in CFRP laminates both experimentally and analytically. In the present study, the effect of the spacing between electrodes on the method is investigated using FEM analyses. Five types of spacing are analyzed here, and the two types of fiber volume fractions are also calculated. Cross-ply beam type specimens are adopted for the analyses. As a result, it was revealed that the effect of the spacing depends on the fiber volume fraction. For laminates of high fiber volume fraction, a short spacing is required to obtain high estimation performances of delamination location and length.
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electrical Resistance Change of unidirectional cfrp due to applied load
Jsme International Journal Series A-solid Mechanics and Material Engineering, 2004Co-Authors: Akira Todoroki, Jyunji YoshidaAbstract:Carbon Fiber Reinforced Plastic (CFRP) is composed of electric conductive carbon fibers and electric insulator resin. Self-monitoring system has been reported utilizing electric Resistance Change of unidirectional CFRP due to fiber breakages and to applied strain. Piezoresistivity is electric Resistance Change with applied strain. Many researchers have already reported the piezoresistivity of unidirectional CFRP. There is, however, large discrepancy in the measured piezoresistivity even in the fiber direction during tensile loading: both positive piezoresistivity (electric Resistance increase) and negative piezoresistivity (electric Resistance decrease) are reported during tensile tests. Electric Resistance Change at electrodes due to poor electric contacts are reported to be a main cause of this large discrepancy. In the present study, therefore, basic properties of piezoresistivity were measured with specimens made from single-ply and multi-ply laminates using a four-prove method. Many cases of electric Resistance Changes in the fiber direction transverse direction were measured during tensile loading. Effect of shear loading was also investigated using a shear test. To investigate the effect of poor electric contact at the electrodes, electrodes were made without polishing specimen surface and a tensile test was performed with measuring piezoresistivity. After the test, the specimen surface was polished, and a tensile test was performed again using the identical specimen. As a result, positive piezoresistivity was obtained for both single-ply and multi-ply specimens and negative piezoresistivity is confirmed that it was caused by the poor electric contact at electrodes.
Björn P. Andreasson - One of the best experts on this subject based on the ideXlab platform.
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role of oxygen vacancies in cr doped srtio3 for Resistance Change memory
Advanced Materials, 2007Co-Authors: Markus Janousch, G I Meijer, B Delley, U Staub, S F Karg, Björn P. AndreassonAbstract:A high density of oxygen vacancies has been found in an experiment to determine the path of electrical conduction in Cr-doped SrTiO3 memory cells. The Cr acts as a seed for the localization of oxygen vacancies, leading to a statistically homogeneous distribution of charge carriers within the path. This warrants a controllable doping profile and improved device scaling down to the nanometer scale. The combination of laterally resolved micro-X-ray absorption spectroscopy and thermal imaging concludes that the Resistance switching in Cr-doped SrTiO3 originates from an oxygen-vacancy drift to/from the electrode that was used as anode during the conditioning process. The experiments shows that this oxygen vacancy concept is crucial for the entire class of transition-metal-oxide-based bipolar Resistance-Change memory.
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Role of oxygen vacancies in cr-doped SrTiO3 for Resistance-Change memory
Advanced Materials, 2007Co-Authors: Markus Janousch, Siegfried E. Karg, G I Meijer, Urs Staub, B Delley, Björn P. AndreassonAbstract:Transition-metal oxides exhibiting a bistable Resistance state are attractive for non-volatile memory applications. The relevance of oxygen vacancies (VO) for the Resistance-Change memory was investigated with x-ray fluorescence, infrared microscopy, and x-ray absorption spectroscopy using Cr-doped SrTiO3 as example. We propose that the microscopic origin of Resistance switching in this class of materials is due to an oxygen-vacancy drift occurring in close proximity to one of the electrodes.
A Ignatiev - One of the best experts on this subject based on the ideXlab platform.
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evidence for an oxygen diffusion model for the electric pulse induced Resistance Change effect in transition metal oxides
Physical Review Letters, 2007Co-Authors: Yibo Nian, J Strozier, Xin Chen, Naijuan Wu, A IgnatievAbstract:Electric-pulse induced Resistance hysteresis switching loops for ${\mathrm{Pr}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ perovskite oxide films were found to exhibit an additional sharp ``shuttle tail'' peak around the negative pulse maximum for films deposited in an oxygen-deficient ambient. The Resistance relaxation in time of this ``shuttle tail'' peak as well as Resistance relaxation in the transition regions of the Resistance hysteresis loop show evidence of oxygen diffusion under electric pulsing, and support a proposed oxygen diffusion model with oxygen vacancy pileup at the metal electrode interface region as the active process for the nonvolatile Resistance switching effect in transition-metal oxides.
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electric pulse induced reversible Resistance Change effect in magnetoresistive films
Applied Physics Letters, 2000Co-Authors: S Q Liu, N J Wu, A IgnatievAbstract:A large electric-pulse-induced reversible Resistance Change active at room temperature and under zero magnetic field has been discovered in colossal magnetoresistive (CMR) Pr0.7Ca0.3MnO3 thin films. Electric field-direction-dependent Resistance Changes of more than 1700% were observed under applied pulses of ∼100 ns duration and as low as ±5 V magnitude. The Resistance Changes were cumulative with pulse number, were reversible and nonvolatile. This electrically induced effect, observed in CMR materials at room temperature has both the benefit of a discovery in materials properties and the promise of applications for thin film manganites in the electronics arena including high-density nonvolatile memory.
Yoshinobu Shimamura - One of the best experts on this subject based on the ideXlab platform.
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matrix crack detection of cfrp using electrical Resistance Change with integrated surface probes
Composites Science and Technology, 2006Co-Authors: Akira Todoroki, Yoshinobu Shimamura, Kazuomi Omagari, Hideo KobayashiAbstract:For the cryogenic tanks of next generation reusable launching vehicles, the laminated composite tank is one of the key technologies. For composite fuel tanks made from laminated carbon fibre reinforced polymers (CFRP), matrix cracking is a significant problem that may cause fuel leakage. In the present paper, an electrical Resistance Change method with integrated probes on a single side of the surface of a CFRP composite structure is adopted to detect the matrix cracking of the laminated composites. For a fuel tank structure made of a CFRP laminate, we cannot mount electrical probes on the end of structure or on the inside of the tank structure. We have to mount all probes only on the outside surface. The present method used finite element analyses (FEA) to search for the best placement of probes for matrix crack detection using a rectangular plate. To simulate the tank structure, all probes are placed on a single surface of the CFRP plate specimen. The present study adopted a four-probe method for measuring the electrical Resistance Change. The FEA revealed that the electrical Resistance increases linearly with increase in the number of matrix cracks inside of the probes. By means of thin CFRP cross-ply laminate, the method was experimentally confirmed to be useful for detecting matrix crack density between the probes. Residual electrical Resistance at the completely unloaded condition increased with increase in matrix crack density. Measurements of the residual electrical Resistance enabled us to detect the matrix crack density without loading.
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Detectability of Bearing Failure of Composite Bolted Joints by Electric Resistance Change Method
Key Engineering Materials, 2006Co-Authors: Yoshinobu Shimamura, Akira Todoroki, Keiko Oda, Masahito UedaAbstract:Bolted joints are widely used for composite structures. As is well known, excessive bearing load gives rise to bearing failure at hole boundaries. Detecting bearing failure is important for assuring integrity of composite structures. Since conventional nondestructive inspection methods are expensive, cumbersome, time-consuming, and not suitable for health monitoring, a simple, low-cost inspection method for bearing failure must be developed. Authors have demonstrated the feasibility of detecting bearing failure by using an electric Resistance Change method. In this study, more detailed analyses were carried out to investigate the detectability in terms of the damage size and the distance between damage and electrodes. The results show that bearing failure of less than 10mm square causes the electric Resistance Change of a few hundred ppm and thus can be easily detected, and that the electrodes can be mounted more than 10 mm far from a bolt hole.
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electrical Resistance Change method for monitoring delaminations of cfrp laminates effect of spacing between electrodes
Composites Science and Technology, 2005Co-Authors: Akira Todoroki, Miho Tanaka, Yoshinobu ShimamuraAbstract:The present study employs an electrical Resistance Change method for monitoring delamination. The authors have found that the electrical Resistance Change method using response surfaces is very effective in identify delaminations in CFRP laminates both experimentally and analytically. In the present study, the effect of the spacing between electrodes on the method is investigated using FEM analyses. Five types of spacing are analyzed here, and the two types of fiber volume fractions are also calculated. Cross-ply beam type specimens are adopted for the analyses. As a result, it was revealed that the effect of the spacing depends on the fiber volume fraction. For laminates of high fiber volume fraction, a short spacing is required to obtain high estimation performances of delamination location and length.
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analysis of the effect of the configuration of the delamination crack on delamination monitoring with electric Resistance Change method
Journal of the Japan Society for Composite Materials, 2003Co-Authors: Akira Todoroki, Miho Tanaka, Yoshinobu Shimamura, Hideo KobayashiAbstract:Since delaminations of composite laminates are usually invisible or difficult to be detected by visual inspections, the delamination causes low reliability of primary structures. In order to improve the low reliability, automatic systems for delamination identifications in-service are desired. The present study employs an electric Resistance Change method for detections of the delaminations. Although the method is effective to monitor the delamination cracks, the method requires many experiments to solve inverse problems. Since the experiment cost is high, an analytical method for preparation of the data sets of the electric Resistance Changes is desired. In practical delamination, however, usually includes a matrix cracking. In the present study, therefore, the effect of the matrix cracking on the electric Resistance Changes between the electrodes is investigated with FEM analyses. As a result, it can be concluded that the simple calculations using a straight delamination crack model are enough for obtaining the data set of electric Resistance Changes to calculate the response surfaces.
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delamination monitoring of graphite epoxy laminated composite plate of electric Resistance Change method
Composites Science and Technology, 2002Co-Authors: Akira Todoroki, Yuuki Tanaka, Yoshinobu ShimamuraAbstract:The present paper employs the electric Resistance Change method for monitoring of location and size of a delamination crack of graphite/epoxy composite laminates. The method is applied to a plate-type specimen with an embedded delamination of cross-ply and quasi-isotropic laminates. Ten electrodes made from copper foil are mounted on the specimen top surfaces. An embedded delamination crack is created by a static indentation test, and the electric Resistance Changes are measured using a conventional strain gage amplifier. Response surfaces are adopted as a tool for solving inverse problems to estimate location and size of delamination crack from the measured electric Resistance Changes of all segments between electrodes. As a result, the present method successfully provides estimations of location and size of the embedded delamination for graphite/epoxy laminated composites.
Markus Janousch - One of the best experts on this subject based on the ideXlab platform.
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transition metal oxide based Resistance Change memories
Ibm Journal of Research and Development, 2008Co-Authors: S Karg, G I Meijer, Markus Janousch, J G Bednorz, C T Rettner, A G Schrott, Eric A Joseph, C Lam, U Staub, F La MattinaAbstract:We provide a status report on the development of perovskite-based transition-metal-oxide Resistance-Change memories. We focus on bipolar Resistance switching observed in Cr-doped SrTiO3 memory cells with dimensions ranging from bulk single crystals to CMOS integrated nanoscale devices. We also discuss electronic and ionic processes during electroforming and Resistance switching, as evidenced from electron-parametric resonance (EPR), x-ray absorption spectroscopy, electroluminescence spectroscopy, thermal imaging, and transport experiments. EPR in combination with electroluminescence reveals electron trapping and detrapping processes at the Cr site. Results of x-ray absorption experiments prove that the microscopic origin of the electroforming, that is, the insulator-to-metal transition, is the creation of oxygen vacancies. Cr-doped SrTiO3 memory cells exhibit short programming times (≤100 ns) and low programming currents (<100 µA) with up to 105 write and erase cycles.
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role of oxygen vacancies in cr doped srtio3 for Resistance Change memory
Advanced Materials, 2007Co-Authors: Markus Janousch, G I Meijer, B Delley, U Staub, S F Karg, Björn P. AndreassonAbstract:A high density of oxygen vacancies has been found in an experiment to determine the path of electrical conduction in Cr-doped SrTiO3 memory cells. The Cr acts as a seed for the localization of oxygen vacancies, leading to a statistically homogeneous distribution of charge carriers within the path. This warrants a controllable doping profile and improved device scaling down to the nanometer scale. The combination of laterally resolved micro-X-ray absorption spectroscopy and thermal imaging concludes that the Resistance switching in Cr-doped SrTiO3 originates from an oxygen-vacancy drift to/from the electrode that was used as anode during the conditioning process. The experiments shows that this oxygen vacancy concept is crucial for the entire class of transition-metal-oxide-based bipolar Resistance-Change memory.
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Role of oxygen vacancies in cr-doped SrTiO3 for Resistance-Change memory
Advanced Materials, 2007Co-Authors: Markus Janousch, Siegfried E. Karg, G I Meijer, Urs Staub, B Delley, Björn P. AndreassonAbstract:Transition-metal oxides exhibiting a bistable Resistance state are attractive for non-volatile memory applications. The relevance of oxygen vacancies (VO) for the Resistance-Change memory was investigated with x-ray fluorescence, infrared microscopy, and x-ray absorption spectroscopy using Cr-doped SrTiO3 as example. We propose that the microscopic origin of Resistance switching in this class of materials is due to an oxygen-vacancy drift occurring in close proximity to one of the electrodes.
