• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.619-625
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• 2008

The effects of thermal cycling on residual stresses in both inorganic passivation/insulating layer that is deposited by plasma enhanced chemical vapor deposition (PECVD) and organic thin film that is used as a bonding adhesive are evaluated by 4 point bending method and wafer curvature method. $SiO_2/SiN_x$ and BCB (Benzocyclobutene) are used as inorganic and organic layers, respectively. A model about the effect of thermal cycling on residual stress and bond strength (Strain energy release rate), $G_c$, at the interface between inorganic thin film and organic adhesive is developed. In thermal cycling experiments conducted between $25^{\circ}C$ and either $350^{\circ}C$ or $400^{\circ}C$, $G_c$ at the interface between BCB and PECVD $ SiN_x $ decreases after the first cycle. This trend in $G_c$ agreed well with the prediction based on our model that the increase in residual tensile stress within the $SiN_x$ layer after thermal cycling leads to the decrease in $G_c$. This result is compared with that obtained for the interface between BCB and PECVD $SiO_2$, where the relaxation in residual compressive stress within the $SiO_2$ induces an increase in $G_c$. These opposite trends in $G_cs$ of the structures including either PECVD $ SiN_x $ or PECVD $SiO_2$ are caused by reactions in the hydrogen-bonded chemical structure of the PECVD layers, followed by desorption of water.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.3
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• pp.7-12
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• 2018

The effects of Ru deposition temperature and post-annealing conditions on the interfacial adhesion energies of atomic layer deposited (ALD) Ru diffusion barrier layer and Cu thin films for the advanced Cu interconnects applications were systematically investigated. The initial interfacial adhesion energies were 8.55, 9.37, $8.96J/m^2$ for the sample deposited at 225, 270, and $310^{\circ}C$, respectively, which are closely related to the similar microstructures and resistivities of Ru films for ALD Ru deposition temperature variations. And the interfacial adhesion energies showed the relatively stable high values over $7.59J/m^2$ until 250h during post-annealing at $200^{\circ}C$, while dramatically decreased to $1.40J/m^2$ after 500 h. The X-ray photoelectron spectroscopy Cu 2p peak separation analysis showed that there exists good correlation between the interfacial adhesion energy and the interfacial CuO formation. Therefore, ALD Ru seems to be a promising diffusion barrier candidate with reliable interfacial reliability for advanced Cu interconnects.

• Journal of dental hygiene science
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• v.15 no.4
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• pp.407-412
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• 2015

This study investigated flexural properties of indirect Gum-shade composite resins for esthetic improvement. The material utilized in this study was Crea.lign, Twiny flow and Twiny paste (TP). Ten specimens were fabricated with a dimension of $25{\times}2{\times}2mm$ according to the ISO 4049. After fabrications, specimens were stored in the distilled water for 24 hours at the temperature of $37^{\circ}C$. Three-point bending test was performed in universal testing machine (Instron 3344; Instron, USA) at a crosshead speed of 1 mm/min until the failure occurred. TP exhibited a higher flexural strength (FS) and flexural modulus (FM) compared to the flowable materials. There were significant differences among the three materials in FS and FM. However, there was no significant difference in work of fracture (WOF) in all tested materials (p>0.05). In Weibull analysis, TP showed the greatest Weibull modulus which means a higher reliability of the materials. Also, Gum-shade composite resins revealed a strong correlation in all flexural properties. There was a positive correlation in FS-FM ($r^2=0.99$) and a negative correlation between FS-WOF and FM-WOF ($r^2>0.97$). Therefore, this confirmed that flexural property was important for mechanical behavior evaluation and useful information. To addition, this improved among mechanical properties correlation of materials as important factor.

• Journal of Korean Society of Disaster and Security
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• v.12 no.4
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• pp.43-52
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• 2019

To analyze the influence on the stability, resulting from application of upgrade pipe roof structure (UPRS) method to the structure existed under subway Station, physical properties of a ground, elasticity and elasto-plastic theories, including displacement analysis of finite elements, stress analysis of finite elements, displacement caused by steel pipe propulsion and internal excavation, and stress change in a steel pipe, were introduced. Then, the influence on structural stability when applying the UPRS method was compared and reviewed based on the construction management standard of the Ministry Land, Infrastructure and Transport and foreign sources, using numerical analysis with a model which assumes that each microelement divided into a structurally stable point consists of the connection of finite points. As a result of the finite element analysis, 7.21 mm maximum displacement, 1/3,950 angular displacement, 70.28 MPa bending compressive stress of steel pipe structure constructed with UPRS (non-excavation) method and 477.38 MPa maximum shear strength were within their allowable standards (25.00 mm, 1/500, 210.00 MPa and 120.00 MPa, respectively), and therefore, the results showed that the design and construction are stable.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.9-14
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• 2017

In the present work, a mechanical performances under cyclic loading in RC (Reinforced Concrete) beams with normal steel and FRPH (Fiber Reinforced Plastic Hybrid) bar are investigated. For the work, RC beam members with $200{\times}200{\times}2175mm$ of geometry and 24 Mpa of design strength are prepared, and 4-point-bending tests are performed for evaluation of cracking, yielding, and ultimate loads. Through static loading test, 48.9kN and 36.0 kN of yielding loads are measured for normal RC and FRPH beam, respectively. They have almost same ultimate load of 50.0 kN. Typical tension hardening behavior is observed in FRPH beam, which is caused by the behavior of FRPH bar with tension hardening. In cyclic loading conditions, FRPH beam has more smaller crack width and scattered crack pattern, and it shows more elastic recovery than normal RC beam. The energy dissipation ratio in FRPH beam is 0.83, which is greater than 0.62 in normal RC beam and it shows more effective resistance to cyclic loadings.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.417-424
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• 2011

This study focused on development of 60 m span PSC girder considering not only structural performance, but also economical efficiency and constructability including from the improvement of cross-section to the tendon profiles in sequence. Bulb-T type cross section was derived from optimization and actual possibilities to design a bridge were assessed through cross section evaluation. Tendons were also arranged efficiently so that the girder could resist the service load effectively. After developed girder was applied to a sample bridge, result of finite element analysis proved all load steps were satisfied with the allowable stress. Furthermore, it seemed that sufficient redundancy will be available to design a bridge safely. Based on these, a full-scale 60 m span girder was fabricated and 4 point bending test was performed. An initial crack occurred over twice of the service load in this experiment, which establishes adequate structural performance. 60 m span Half-Decked PSC girder developed in this study has a lower height for the given span which resulted from cross section improvement and efficient tendon layout. This girder also has not only the structural advantage, but also advantages in economical efficiency and constructability.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.4
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• pp.327-336
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• 2013

This study aimed to investigate the reinforcing effect of two kinds of glass fiber, Quarts Splint$^{TM}$ Mesh and SES MESH$^{(R)}$ and to evaluate the effect of the thermocycling on the transverse strength of the denture base and on the reinforcing effect of the reinforcements. 20 specimens of the size of $2.5{\times}10.0{\times}65.0mm$ were fabricated for each group; control group, metal mesh reinforcement group, Quarts Splint$^{TM}$ Mesh reinforcement group and SES MESH$^{(R)}$ reinforcement group. To find the difference made by the thermocycling, 10 specimens of each reinforcement group were treated by thermocycling. 3-point bending test was performed to measure the transverse strength of the denture base resin. The specimens reinforced with SES MESH$^{(R)}$ and Quarts Splint$^{TM}$ Mesh showed significantly higher transverse strength than the control group (P<.05), and significantly lower transverse strength than the specimens reinforced with the metal mesh (P<.05). Thermocycled specimens were lower in transverse strength than non-thermocycled specimens in the control group, metal mesh group, Quarts Splint$^{TM}$ Mesh group and SES MESH$^{(R)}$ group, however significant difference (P<.05) was found only in the control group.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.587-598
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• 2015

We examined various existing threshold methods for the determination of the first arrival time of acoustic emission (AE), and developed a new variable threshold method that could determine the first arrival time of AE more accurately and more quickly than existing methods. The new method, a modification of an existing threshold method, does not fix the threshold, but applies variable thresholds for the AE signals according to noise analysis. Two- and three-dimensional models were established to test the effectiveness of the new method. It could determine source locations of AE in a two-dimensional model 38.3% more accurately than the pre-existing threshold methods. Its accuracy improvement over the existing methods in a three-dimensional model was about 15.2%. A practical test involved measuring the source locations of AE during three-point bending tests of granite cores. The new method placed the sources closer to the fracture plane than did the pre-existing methods, indicating its superior (and quicker) ability to determine the source locations of AE.

• Advances in concrete construction
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• v.5 no.5
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• pp.513-537
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• 2017

In this study, the fracture toughness $K_{IC}$ of high performance concrete (HPC) was investigated by conducting three-point bending tests on a total of 240 notched beams of $500mm{\times}100mm{\times}100mm$ subjected to heating temperatures up to $450^{\circ}C$ with exposure times up to 16 hours and various heating and cooling rates. For a heating rate of $3^{\circ}C/min$, $K_{IC}$ for the hot concrete sustained a monotonic decrease trend with the increasing heating temperature and exposure time, from $1.389MN/m^{1.5}$ at room temperature to $0.942MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.906MN/m^{1.5}$ for 8-hour exposure time and $0.866MN/m^{1.5}$ for 16-hour exposure time. For the cold concrete, $K_{IC}$ sustained a two-stage decrease trend, dropping slowly with the heating temperature up to $150^{\circ}C$ and then rapidly down to $0.869MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.812MN/m^{1.5}$ for 8-hour exposure time and $0.771MN/m^{1.5}$ for 16-hour exposure time. In general, the $K_{IC}$ values for the hot concrete up to $200^{\circ}C$ were larger than those for the cold concrete, and an inverse trend was observed thereafter. The increase in heating rate slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.893MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.839MN/m^{1.5}$ for $10^{\circ}C/min$ for the hot concrete and from $0.792MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.743MN/m^{1.5}$ for $10^{\circ}C/min$ for the cold concrete after an exposure time of 16 hours. The increase in cooling rate also slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.771MN/m^{1.5}$ for slow cooling to $0.739MN/m^{1.5}$ for fast cooling after an exposure time of 16 hours. The fracture energy-based fracture toughness $K_{IC}$' was also assessed, and similar decrease trends with the heating temperature and exposure time existed for both hot and cold concretes. The relationships of two fracture toughness parameters with the weight loss and the modulus of rapture were also evaluated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.4
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• pp.227-233
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• 2022

The 3D-printing technique is used for manufacturing objects by adding multiple layers, and it is relatively easy to manufacture objects with complex shapes. The 3D concrete printing technique, which incorporates 3D printing into the construction industry, does not use a formwork when placing concrete, and it requires less workload and labor, so economical construction is possible. However, 3D-printed concrete is expected to have a lower strength than that of molded concrete. In this study, the properties of 3D-printed concrete were analyzed. To fabricate the 3D-printed concrete samples, the extrusion path and shape of the samples were designed with Ultimaker Cura. Based on this, G-codes were generated to control the 3D printer. The optimal concrete mixing proportion was selected considering such factors as extrudability and buildability. Molded samples with the same dimensions were also fabricated for comparative analysis. The properties of each sample were measured through a three-point bending test and uniaxial compression test, and a comparative analysis was performed.