• International Journal of Automotive Technology
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• 제3권4호
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• pp.157-163
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• 2002

It is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing (NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam (DCB). An optimal condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated and discussed. The experimental values are in good agreement with the computed results by boundary element method (BEM) and Ripling's equation.

• Computers and Concrete
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• 제8권3호
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• pp.327-341
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• 2011

Three-dimensional graphic objects created by MATLAB are exported to the AUTOCAD program through the MATLAB handle functions. The imported SAT format files are used to produce the finite element mesh for MSC.PATRAN. Based on the Monte-Carlo random sample principle, the material heterogeneity of cement composites with randomly distributed fibers is described by the WEIBULL distribution function. In this paper, a concept called "soft region" including micro-defects, micro-voids, etc. is put forward for the simulation of crack propagation in fiber-reinforced cement composites. The performance of the numerical model is demonstrated by several examples involving crack initiation and growth in the composites under three-dimensional stress conditions: tensile loading; compressive loading and crack growth along a bimaterial interface.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.97-102
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• 2000

It is well recognized that the ultrasonic methods is one of the most common and reliable nondestructive testing(NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam(DCB). The optimum condition of transmission coefficients in the adhesively bonded joints and it's experimental accuracy by the ultrasonic method have been investigated. The experimental values are in good agreement with the computed results by boundary element method(BEM) and Ripling's equation.

• 소성∙가공
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• 제21권5호
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• pp.291-297
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• 2012

In this paper, the effect of back tension in multi-pass drawing or wiredrawing on the central bursting defect is investigated using finite element predictions. A rigid-plastic finite element method was used together with the McClintock damage model. Central bursting defects under different back tension stress values ranging from 0% to 20% of the yield strength of the material were predicted and they were compared to understand the effect of the back tension stress values on the central bursting defect. It is found that the level of back tension has a strong influence on the cumulative damage. Thus, higher back tension raises the possibility of the central bursting defect occurring, even though it decreases the interfacial pressure between the die and the work piece.

• 한국전기전자재료학회논문지
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• 제20권2호
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• pp.118-123
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• 2007

The purpose of this work was to investigate the design and fabrication process effects on electrical properties in high capacitance multilayer ceramic capacitor (MLCC) with nickel electrode. Dielectric breakdown voltage and insulation resistance value were decreased with increasing stack layer number, but dielectric constant and capacitance were increased. With increasing green sheet thickness, dielectric breakdown voltage, C-V and I-V properties were also increased. The major reasons of the effects were thought to be the defects generated extrinsically during fabrication process and interfacial reactions formed between nickel electrode and dielectric layer. These investigations clearly showed the influence of both green sheet thick ness and stack layer number on the electrical properties in fabricating the MLCC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1057-1059
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• 1993

Some interested phenomena, which were appeared near the bonding interface, were investigated by angle lapping and delineation method, SEM, and TEM observations. Voids, defects, material continuity, and interfacial oxide stability were observed and discussed in the fusion-bonded Bi-Si or Si-$SiO_2$/Si wafer pairs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.189.1-189.1
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• 2013

Titanium dioxide (TiO2) is a wide bandgap semiconductor possessing photochemical stability and thus widely used for photocatalysis. However, enhancing photocatalytic efficiency is still a challenging issue. In general, the efficiency is affected by physio-chemical properties such as crystalline phase, crystallinity, exposed crystal facets, crystallite size, porosity, and surface/bulk defects. Here we propose an alternative approach to enhance the efficiency by studying interfaces between thin TiO2 layers to be stacked; that is, the interfacial phenomena influencing on the formation of porous structures, controlling crystallite sizes and crystallinity. To do so, multi-layered TiO2 thin films were fabricated by using a sol-gel method. Specifically, a single TiO2 thin layer with a thickness range of 20~40 nm was deposited on a silicon wafer and annealed at $600^{\circ}C$. The processing step was repeated up to 6 times. The resulting structures were characterized by conventional electron microscopes, and followed by carrying out photocatalytic performances. The multi-layered TiO2 thin films with enhancing photocatalytic efficiency can be readily applied for bio- and gas sensing devices.

• E2M - 전기 전자와 첨단 소재
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• 제16권9호
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• pp.64.2-65
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• 2003

A 4 nm layer of ZrOx (targeted x-2) was deposited on an interfacial layer(IL) of native oxide (SiO, t∼1.2 nm) surface on 200 mm Si wafers by a manufacturable atomic layer chemical vapor deposition technique at 30$0^{\circ}C$. Some as-deposited layers were subjected to a post-deposition, rapid thermal annealing at $700^{\circ}C$ for 5 min in flowing oxygen at atmospheric pressure. The experimental x-ray diffraction, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and high-resolution parallel electron energy loss spectroscopy results showed that a multiphase and heterogeneous structure evolved, which we call the Zr-O/IL/Si stack. The as-deposited Zr-O layer was amorphous $ZrO_2$-rich Zr silicate containing about 15% by volume of embedded $ZrO_2$ nanocrystals, which transformed to a glass nanoceramic (with over 90% by volume of predominantly tetragonal-$ZrO_2$(t-$ZrO_2$) and monoclinic-$ZrO_2$(m-$ZrO_2$) nanocrystals) upon annealing. The formation of disordered amorphous regions within some of the nanocrystals, as well as crystalline regions with defects, probably gave rise to lattice strains and deformations. The interfacial layer (IL) was partitioned into an upper Si $o_2$-rich Zr silicate and the lower $SiO_{x}$. The latter was sub-toichiometric and the average oxidation state increased from Si0.86$^{＋}$ in $SiO_{0.43}$ (as-deposited) to Si1.32$^{＋}$ in $SiO_{0.66}$ (annealed). This high oxygen deficiency in $SiO_{x}$ indicative of the low mobility of oxidizing specie in the Zr-O layer. The stacks were characterized for their dielectric properties in the Pt/{Zr-O/IL}/Si metal oxide-semiconductor capacitor(MOSCAP) configuration. The measured equivalent oxide thickness (EOT) was not consistent with the calculated EOT using a bilayer model of $ZrO_2$ and $SiO_2$, and the capacitance in accumulation (and therefore, EOT and kZr-O) was frequency dispersive, trends well documented in literature. This behavior is qualitatively explained in terms of the multi-layer nanostructure and nanochemistry that evolves.ves.ves.

• 한국염색가공학회지
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• 제29권1호
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• pp.37-44
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• 2017

An issue of major concern in the utilization of laminated composites based epoxy resin is associated with the occurrence of delaminations or interlaminar cracks, which may be related to manufacturing defects or are induced in service by low-velocity impacts. A strong interfacial filament/brittle epoxy resin bonding can, however, be combined with the high fracture toughness of weak interfacial bonding, when the filaments are arranged to have alternate sections of shear stress. To improve this drawback of the epoxy resin, UV-thermal dual curable resin were developed. This paper presents UV-thermal dual curable resin which were prepared using epoxy acrylate oligomer, photoinitiators, a thermal-curing agent and thermoset epoxy resin. The UV curing behaviors and characteristics of UV-thermal dual curable epoxy resin were investigated using Photo-DSC, DMA and FTIR-ATR spectroscopy. The mechanical properties of UV-thermal dual curable epoxy resin impregnated CF prepreg by UV curable resin content were measured with Tensile, Flextural, ILSS and Sharpy impact test. The obtained results showed that UV curable resin content improves the epoxy toughness.

• The Journal of Advanced Prosthodontics
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• 제10권3호
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• pp.197-204
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• 2018

PURPOSE. To determine the extent of treatment traces, the roughness depth, and the quantity of titanium nitride (TiN) removed from the surface of CAD/CAM abutments after treatment with various instruments. MATERIALS AND METHODS. Twelve TiN coated CAD/CAM abutments were investigated for an in vitro study. In the test group (9), each abutment surface was subjected twice (150 g vs. 200 g pressure) to standardized treatment in a simulated prophylaxis measure with the following instruments: acrylic scaler, titanium curette, and ultrasonic scaler with steel tip. Three abutments were used as control group. Average surface roughness (Sa) and developed interfacial area ratio (Sdr) of treated and untreated surfaces were measured with a profilometer. The extent of treatment traces were analyzed by scanning electron microscopy. RESULTS. Manipulation with ultrasonic scalers resulted in a significant increase of average surface roughness (Sa, P<.05) and developed interfacial area ratio (Sdr, P<.018). Variable contact pressure did not yield any statistically significant difference on Sa-values for all instruments (P=.8). Ultrasonic treatment resulted in pronounced surface traces and partially detachment of the TiN coating. While titanium curettes caused predominantly moderate treatment traces, no traces or detectable substance removal has been determined after manipulation with acrylic curettes. CONCLUSION. Inappropriate instruments during regular plaque control may have an adverse effect on the integrity of the TiN coating of CAD/CAM abutments. To prevent defects and an increased surface roughness at the transmucosal zone of TiN abutments, only acrylic scaling instruments can be recommended for regular maintenance care.