• Structural Engineering and Mechanics
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• 제18권3호
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• pp.277-286
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• 2004

Defective metallic components and structures are being repaired with bonded composite patches to improve overall mechanical and fatigue properties. In this study, fatigue crack growth tests were conducted on pre-cracked 7075/T6 Aluminum substrates with and without bonded Boron/epoxy patches. A considerable increase in the fatigue life and a decrease in the stress intensity factor (SIF) were observed as the number of patch plies increased. The experimental results demonstrate that the patch configurations and patch thickness can enhance fatigue life by order of magnitude. Quantitative comparisons between analytical and experimental data were made, and the analytical model based on a modified Rose's analytical solution appears to best estimate the fatigue life.

• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.655-661
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• 2006

Dielectric and piezoelectric properties of PMN-PZT ceramics with a high mechanical quality factor$(Q_m)$ and a low temperature sintering temperature were investigated as a function of PZN substitution in order to develop multilayer piezoelectric transformer for AC-DC converter. Multilayer piezoelectric transformers were subsequently manufactured using the PMN-PZN-PZT ceramic offering the optimal behavior and then the electrical performance were invetigated. At the sintering temperature of $940^{\circ}C$, density, electromechanical coupling factor$(k_p)$, mechanical qualify factor$(Q_m)$ and dielectric constant$(\varepsilon_r)$ of 8 mol% PZN substituted specimen were $7.73g/cm^3$, 0.524, 1573 and 1455, respectively. The PZN substitution caused a increase in the dielectric constant and the electromechnical coupling factor. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at near the resonant frequency of 76.55 kHz and increased according to the increase of load resistance. The multilayer piezoelectric transformer with the output impedance coincided with the load resistance showed the temperature increase of less than $20^{\circ}C$ at the output power of 10 W. Based on the results, the manufactured multilayer transformer using the low temperature sintered PMN-PZN-PZT ceramics can be stably driven for both step-up and down transformers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.981-984
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• 2001

The piezoelectric properties of 0.05pb(A $l_{0.5}$N $b_{0.5}$) $O_3$-0.95Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_3$+0.7wt%N $b_2$ $O_{5}$ +0.5wt%Mn $O_2$ceramics with the additives of BaC $O_3$were investigated. For the additions of BaC $O_3$, the dielectric constant ($\varepsilon$$^{T}$ $_{33}$ ), the piezoelectric constant ( $d_{33}$ ), the electromechanical coupling factor ( $k_{p}$ ), and . the mechanical quality factor ( $Q_{m}$ ) were increased, but dielectric loss (tan$\delta$) was decreased. The highest piezoelectric properties and dielectric properties were observed at the sintered temperature of 120$0^{\circ}C$ and 0.4 wt% of BaC $O_3$, and the properties of $d_{33}$ , $k_{p}$ , and $Q_{m}$ were 339(x10$^{-12}$ C/N), 59% and 1754, respectively.vely.y.y.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.255-256
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• 2007

In the study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, PMN-PNN-PZT ceramics were fabricated using $Na_2CO_3,\;Li_2CO_3$ as sintering aids and their dielectric and piezoelectric properties were investigated according to the variations of $MnO_2$ as additives and sintering aids. At the sintering temperature of $900^{\circ}C$ and 0.1wt% $MnO_2$ as sintering aids, density, electromechanical coupling factor$(k_p)$, mechanical quality factor$(Q_m)$, piezoelectric constant$(d_{33})$, and dielectric constant $({\varepsilon}_r)$ showed the optimum value of $7.87[g/cm^3]$, 0.61, 1131, 1127 and 376, respectively, for multilayer piezoelectric actuator application.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.294-296
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• 1999

Solid solution ceramics having various ratios between xPb( $Y_{1}$2/T $a_{1}$2/) $O_3$ and Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_3$were synthesized by a conventional solid state reaction for well sintered specimens, dielectric and piezoelectric prperties were studied as a function of composition. The dielectric constant of PYT-PZT ceramics of 4 mol% PYT was 1,424 at room temperature. The maximum value of electromechanical couping facotr $k_{p}$ of 51% $k_{t}$ of 30% were obtained at the composition of 4 mol% PYT, howerver mechanical quality factor( $Q_{m}$) had a minimum value of 69 at 4 mol% PYT. Also the maximum value of piezoelectric constant of $D_{33}$(310[pC/N]) and $d_{31}$(-131[pC/N]) were obtained at the composition of 4 mol% PYT content.ntent.t.t.t.

• 한국세라믹학회지
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• 제42권10호
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• pp.698-702
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• 2005

Dielectric and Piezoelectric properties of complex perovskite 0.92Pb($Zr_{1/2}Ti_{1/2})O_{3}-(0.08-x)Pb(Cu_{1/3}Nb_{2/3})O_{3}-xPb(Mn_{1/3}Nb_{2/3})O_{3}(0{\leq}x{\leq}0.080$) (PZT-PCN-PMN) system were investigated as a function of PMN content. With the increase of PMN content of the sintered specimens, tetragonal phase was coexisted with rhombohedral phase, the dielectric constant was decreased, mechanical quality factor ($Q_{m}$) was inceased, and optimal sintering temperature was increased up to 1050$^{\circ}C$. For the composition of x = 0.064 sintered at 1050$^{\circ}C$ for 2 h, 1939 of maximum mechanical quality factor ($Q_{m}$), 57$\%$ of electromechanical coupling factor ($k_{p}$), and 1100$^{\circ}C$ of dielectric constant, 0.37$\% $ of dielectric loss (tan $\delta$) were obtained.

• 한국재료학회지
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• 제13권6호
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• pp.360-364
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• 2003

$Sr_{l}$ $\pm$x/$Bi_{2}$ $\pm$y/$Ta_2$ $O_{9}$ and $Sr_{l}$ $\pm$$Bi_{x}$ $2\pm$y$Nb_2$$O_{9}$ ceramics were prepared by a solid state reaction method. X-ray diffraction analysis indicated that single-phase of Bi-layered perovskite was obtained. According to Sr/Bi content ratio, Curie temperature( $T_{c}$), electromechanical factor($K_{p}$ ) and mechanical quality factor($Q_{m}$ ) were measured. The Curie temperature of SBN(SBT) rose from $414^{\circ}C$(314$^{\circ}C$) to $494^{\circ}C$(426$^{\circ}C$) when Sr/Bi content ratio was increased. In the case of Sr/Bi content ratio = 0.55/2.3, the maximum value of the mechanical quality factor $Q_{m}$ of SBT and SBN were obtained 3320 and 1010, respectively.

• 한국전기전자재료학회논문지
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• 제20권12호
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• pp.1049-1055
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• 2007

Lots of integration work has been done in order to miniaturize the devices for communication. To do this work, one of key work is to get miniaturized inductor with high Q factor for RF circuitry. However, it is not easy to get high Q inductor with silicon based substrate in the range of GHz. Although silicon is well known for its good electrical and mechanical characteristics, silicon has many losses due to small resistivity and high permittivity in the range of high frequency. MEMS technology is a key technology to fabricate miniaturized devices and LTCC is one of good substrate materials in the range of high frequency due to its characteristics of high resistivity and low permittivity. Therefore, we proposed and studied to fabricate and analyze the inductor on the LTCC substrate with MEMS fabrication technology as the one of solutions to overcome this problem. We succeeded in fabricating and characterizing the high Q inductor on the LTCC substrate and then compared and analyzed the results of this inductor with that on a silicon and a glass substrate. The inductor on the LTCC substrate has larger Q factor value and inductance value than that on a silicon and a glass substrate. The values of Q factor with the LTCC substrate are 12 at 3 GHz, 33 at 6 GHz, 51 at 7 GHz and the values of inductance is 1.8, 1.5, 0.6 nH in the range of 5 GHz on the silicon, glass, and LTCC substrate, respectively.

• 한국전기전자재료학회논문지
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• 제14권5호
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• pp.356-361
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• 2001

The structureal, dielectric and piezoelectric properties of Pb[(Sb$\_$1/2/Nb$\_$1/2/)$\_$x/-(Ni$\_$1/3/Nb$\_$2/3/)$\_$0.15-x/-(Zr$\_$y/Ti$\_$1-y/)$\_$0.85/]O$_3$(x=0∼0.05, y=0.47∼0.52) ceramics were investigated with the substitution of Pb(Sb$\_$1/2/Nb$\_$1/2/)O$_3$(abbreviated PSN) and the Zr/Ti ratio. At Zr/Ti ratio of 50/50, tetragonality was decreased and grain size abruptly decreased with the increase of PSN substitution. Curie temperature was decreased and dielectric constant increased with the substitution of PSN. The coercive field increased and remnant polarization decreased with the substitution of PSN. Electromechanical coupling factor(k$\_$p/) showed the highest value of 0.622 at 1mol% PSN, but mechanical quality factor(Q$\_$m/) showed the minimum value at that composition. Dielectric constant and electromechanical coupling factor with the Zr/Ti ratio showed maximum values at Zr/Ti ratio of 50/50 and mechanical quality factor showed minimum values near the Zr/Ti ratio of 50/50.

• 대한기계학회논문집B
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• 제23권11호
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• pp.1390-1398
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• 1999

A numerical analysis for ROT sparger of PWR(Pressurized Water Reactor) is carried out. Computation is performed to investigate the flow characteristics as the change of design factor. As the result of this study, RDT sparger's flow resistance coefficient is K=3.53 at the present design condition if engineering mar&in is considered with 20%, and flow ratio into branch pipe is $Q_s/Q_i=0.41$. Velocity distribution at exit is not uniform because of separation in branch pipe. In the change of inlet flow rate and section area ratio of branch pipe for main pipe, flow resistance coefficient is increased as $Q_s/Q_i$ decreasing, but in the change of branch angle and outlet nozzle diameter of main pipe, flow resistance coefficient is decreased as $Q_s/Q_i$ decreasing. As the change rate of $Q_s/Q_i$ is the larger, the change rate of flow resistance coefficient is the larger. The change rate of pressure loss is the largest change as section area ratio changing. The optimal design condition of sparger is estimated as the outlet nozzle diameter ratio of main pipe is $D_s/D_i=0.333$, the section area ratio is $A_s/A_i=0.2$ and the branch angle is ${\alpha}=55^{\circ}$.