• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3191-3196
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• 2013

Ultrasonic transducer is the sensor which is measuring distance. Piezo ceramic of ultrasonic sensor and adhesive technique of matching layer are the most core techniques. With the study of relation on matching layer which takes off the ultrasonic wave into the air, this paper aims to find the second useful frequency as the results which can be changed are extracted in case piezo ceramic and matching layer are bonded. And the experiment is done with piezo ceramic as real piezoelectric element and matching layer of chemical wood. OD of piezo ceramic has designed by ${\Phi}50{\times}3T$ and OD of matching layer is designed by ${\Phi}62{\times}12t$ with ${\lambda}=1/4$. Acoustic impedance is generated at the most optimum resonant frequency of 53 Khz. As experimental result, more available frequency can be generated by using the adhesive close to solid than the flexible one.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.627-632
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• 1998

This study deals with the effect on adhesive strength properties of waterproofing and reinforcing layer and mortar or concrete substrate applicated by epoxy resin anticorrosive and bonding materials. Properties of adhesive strength change condition of concrete substrate, temperature, moisture, curing and cleaning and so on. The purpose of this study is that it makes the estimation value of bond strength of concrete wall and epoxy resin layer when coated epoxy resin as anticorrosive materials for durability performance estimation depend on concrete watertightness, and when penetrated epoxy resin for the reinforcement of concrete used the carbon fiber sheet.

• Applied Microscopy
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• v.28 no.3
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• pp.273-282
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• 1998

Ultrastructure of fertilized egg envelope in the tomato clown anemonefish (Amphiprion freatus) was examined by mean of light, scanning and transmission electron microscopies. The fertilized egg of tomato clown anemonefish was of non-transparent, ellipsoidal, adhesive and non-floted type, and there were numerous oil droplets in the yolk sac and adhesive filaments in the area of the animal pole. The outer surface of egg envelope was smooth. The fertilized egg envelope consisted of two distinct layers; a non-adhesive outer electron-dense layer and an inner layer, consisting of five horizontal low electron-dense lamellae alternating with the middle electron dense interlamellae.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.11a
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• pp.90-93
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• 2001

In the present work, ultrasonic testing method has been developed to evaluate adhesive layers in rocket motor case assembly for the reliability of the rocket. The main objective of the present work was to find debonding between steel and rubber layers. The relationship between adhesion ratio and reflected ultrasonic amplitude was calculated by considering reflection coefficient at the interface between steel and rubber layers. It was found that the higher amplitude of ultrasound is reflected for the debonding area, and shown good agreements with experimental results. The ultrasonic C-scan images offers good implements for the determination of debonding area. The nondestructive testing results were compared with the micrography of destruective testing. As results, ultrasonic testing could be utilized for the evaluation of adhesive layer in the rocket motor case assembly.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.216-219
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• 2000

The adhesive bonded single-lap joint is due to its intrinsic load eccentricity problem, severe peel stresses concentration occur at both end of the joint. In this paper, new lap-joint is designed to avoid the singular peel stress, and to compare the stresses of the middle adhesive layer between the single-lap joint and the wavy-lap joint. Two adherend lay-up, i.e., [90/0/90/0]$_{2s}$ and [0/90/0/90]$_{2s}$ were consider in the study.

• Structural Engineering and Mechanics
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• v.83 no.5
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• pp.693-707
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• 2022

Bonded joints have proven their performance against conventional joining processes such as welding, riveting and bolting. The single-lap joint is the most widely used to characterize adhesive joints in tensile-shear loadings. However, the high stress concentrations in the adhesive joint due to the non-linearity of the applied loads generate a bending moment in the joint, resulting in high stresses at the adhesive edges. Geometric optimization of the bonded joint to reduce this high stress concentration prompted various researchers to perform geometric modifications of the adhesive and adherends at their free edges. Modifying both edges of the adhesive (spew) and the adherends (bevel) has proven to be an effective solution to reduce stresses at both edges and improve stress transfer at the inner part of the adhesive layer. The majority of research aimed at improving the geometry of the plate and adhesive edges has not considered the effect of temperature and water absorption in evaluating the strength of the joint. The objective of this work is to analyze, by the finite element method, the stress distribution in an adhesive joint between two 2024-T3 aluminum plates. The effects of the adhesive fillet and adherend bevel on the bonded joint stresses were taken into account. On the other hand, degradation of the mechanical properties of the adhesive following its exposure to moisture and temperature was found. The results clearly showed that the modification of the edges of the adhesive and of the bonding agent have an important role in the durability of the bond. Although the modification of the adhesive and bonding edges significantly improves the joint strength, the simultaneous exposure of the joint to temperature and moisture generates high stress concentrations in the adhesive joint that, in most cases, can easily reach the failure point of the material even at low applied stresses.

• Korean Journal of Materials Research
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• v.8 no.8
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• pp.744-750
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• 1998

Unlike common device, MEMS(micro-electro-mechanical system) device consists of very small mechanical structures which determine the performance of the device. Because of its small mechanical structure inside. MEMS device is very sensitive to thermal stress caused by CTE(coefficient of thermal expansion) mismatch between its components. Therefore, its characteristics are affected by material properties. process temperature. and dimensions of each layer such as chip, adhesive and substrate. In this study. we investigated the change of the thermal stress in the chip attached to a substrate. With computer-aided finite element method (FEM), the computer simulation of the thermal stress was conducted on variables such as bonding material, process temperature, bonding layer thickness and die size. The commercial simulation program, ABAQUS ver5.6, was used. Subsequently 3-layer test samples were fabricated, and their degree of bending were measured by 3-D coordinate measuring machine. The experimental results were in good agreement with the simulation results. This study shows that the bonding layer could be the source of stress or act as the buffer layer for stress according to its elastic modulus and CTE. Solder adhesive layer was the source of stress due to its high elastic modulus, therefore high compressive stress was developed in the chip. And the maximum tensile stress was developed in the adhesive layer. On the other hand, polymer adhesive layer with low elastic modulus acted as buffer layer, and resulted in lower compressive stress. The maximum tensile stress was developed in the substrate.

• Journal of KSNVE
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• v.8 no.6
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• pp.1093-1102
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• 1998

The success of controllability of smart structures depends on the quality of the bonding along the interface between the main structure and the attached sensing and acuating elements. Generally, the analysis procedures neglect the effect of the interfacial bond layer or assume that this bond layer behaves like viscoelastic material. Three different bond layers. two modified epoxy adhesives, and one isocyanate adhesive were prepared for their toughness and moduli. Bond layer of the chosen adhesive provides an almost perfect bonding condition between the composite structure and the PZT while bended significantly like arrow-shape. The perfect bonding condition is tested by considering various material properties of the bond layers. and based on this perfect bonding condition, the effects of the interfacial bond layer on the dynamic behavior and controllability of the test structure is experimentally studied. Once the perfect bonding condition is achieved. dynamic effects of the bond layer itself on the dynamic characteristics of the main structure is negligible. but the contribution of the attached PZT elements on the stiffness of the multi-layered structure becomes significant when the thickness of the bond layer increased.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.280-281
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• 2009

Piezoelectric vibrators can be good replacements of electric motors to excite touch screen of a mobile device owing to small volume and low power consumption. One problem to be solved yet for real application is larger excitation force or moment than available currently. More efficient excitation by a piezoelectric vibrator could be achieved by operating at one of resonance frequencies of the system, which must also be as close as possible to frequency range where index finger is most sensitive and increasing transmission force or moment at that frequency. In this study, dynamic models are derived for the piezoelectric exciter and an adhesive viscoelastic layer, which connect the exciter to the screen. The adhesive layer is modeled as distributed stiffness by considering its geometric shape to relative to the piezoelectric exciter. Then, equations of motion for the piezoelectric exciter and the adhesive layer are derived using Hamilton's principle. Based on this model, dynamic characteristics of the exciter will be designed to maximize the force or moment transmitted onto the screen structure.

• Computational Structural Engineering
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• v.10 no.2
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• pp.131-138
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• 1997

This paper concerns the stress singularity at the interface corner of the viscoelastic adhesive layer bonded between rigid adherends, subjected to a uniform transverse tensile strain. The characteristic equation is derived in the Laplace transformed space, following Williams, and the transformed characteristic equation is inverted analytically into real time space for the viscoelastic model considered here. The order of the singularity is obtained numerically. The time-domain boundary element method is employed to investigate the nature of stresses along the interface. Numerical results show that the order of the singularity increases with time while the free-edge stress intensity factors are relaxed with time.