• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.11-16
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• 1990

The effects on the dynamic behaviour of the geometric nonlinearity and large dynamic tensile forces occurring in hostile sea environments must be investigated for assessing extreme tensions and fatigue life expectancy of cable. In this paper, the combined effects on the cable dynamic responses are shown through comparisons between numerical solutions to the cable dynamic equations with geometric nonlinearity and large tensile force terms as well as nonlinear drag term and those to the cable equations with only nonlinear drag term. It is found that, in steady state, the cambined effects increase the maximum dynamic tension and reduce the magnitude of the minimum of the dynamic tension at the middle of the cable. This decrease together with the increase of the maximum dynamic tension, cause the average tension to become higher and, therefore, it may deteriorate the cable fatigue life.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.5
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• pp.588-595
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• 2016

This paper is a study on head bolts that are used in A/C compressors to reduce production cost and solve leak problems on the head bolt seat area that causes massive intermittent malfunctioning during production. In this study, the pre-heat treated steel, which was used as a material in the head bolt, eliminated the heat treatment process after forging. The pre-heat treated steel head bolts, which have 10 % lower tensile strength than the conventional SCM 435 head bolts, were selected after considering the results of creeping rupture properties, axial force, and stress concentration per tensile strength variation. Then, the performance test and the durability test with the A/C compressor that was assembled with the pre-heat treated steel head bolts were performed and verified. Based on the results, the pre-heat treated steel head bolts developed in this study saved 7.3 % in production cost by eliminating the heat treatment process and the logistics process. Furthermore, the leak problem on the head bolt seat area in the A/C compressor was addressed significantly on the mass production assembly line.

• Transactions of Materials Processing
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• v.29 no.6
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• pp.323-330
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• 2020

The surface region of a sheet metal may have different characteristics from the inner region because the surface region is less restricted than the interior. In addition, the grains on the free surface are less hardened because of surface adsorption of the dislocations, rather than piling up. In the case of bulk or thick sheet metals, this effect is negligible because the fraction of the surface region is much smaller than that of the inner region. However, this surface effect is important in the case of ultra-thin sheet metals. In order to evaluate the surface effect, tensile and bending tests were performed for the SS304 stainless steel with a thickness of 0.39 mm. The bending force predicted using the tensile behavior is higher than the measurement because of the surface effect. To account for the surface effect, the surface layer model was developed by dividing the sheet section into surface and inner layers. The mechanical behaviors of the two regions were calibrated using the tensile and bending properties. The surface layer model reproduced the bending behavior of the ultra-thin sheet metal.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.1
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• pp.41-49
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• 1991

A knowledge of the resdual stress distribution at circumferential weldments can normally increase the accuracy of a fracture assessment in pipe line. In this paper, we present the measurements about the residual stress distributions at three kinds of circumferential butt welded pipes using the holl drilling strain gage method. By this experiment, we have obtined the following characteristics. At the inner surface of the pipe region near the center line of welding is under high tensile residual stress. However, as the distance from the center line of welding increases, the tensile component decreases and finally becomes compressive residual stress at region far away from the center line of welding. The longitudinal residual stress at the outer surface is compressive regardless of the diameter of pipe and the circumferential stress is changed from compressive to tensile as pipe diameter increases. The results also demonstrate that the residual stress is mainly caused by self-restraint bending force in the pipe welding.

• Journal of Korean Association for Spatial Structures
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• v.23 no.1
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• pp.53-60
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• 2023

A bending experiment was conducted to verify the structural performance of the U-flange truss hybrid bean using rebars or steel pipes to reinforce the upper compression zone. As a result of evaluating the bending strength of the truss hybrid beam according to the Structural Design Standard (KDS 14 2020: 2022) by introducing the lattice member as a tensile resistance element, the following conclusions were obtained. Considering the lattice element as a tensile resistance element, the nominal bending strength was increased by 38.57 to 47.90 kN.m. As a result of reviewing the experiment as to whether the flexural member has proper ductility, it was found that it is desirable to place appropriate rebars, steel quality plans, and lateral restraints on the upper and lower parts of the hybrid beam to have sufficient ductility ratio.

• Journal of Technologic Dentistry
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• v.45 no.3
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• pp.61-66
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• 2023

Purpose: The current study examined the retention and wear resistance of stud-type attachments made of high-performance polyetheretherketone (PEEK) or polyetherketoneketone (PEKK) from the polyaryletherketones (PAEKs) family. Methods: The study sample included 10 PEEK or PEKK attachments that were mounted onto their male parts, designed on the upper aspect of the attachment, with a load of 30 N. Tensile stress was applied using an Instron machine to separate the male and female parts, and the maximum tensile stress to be applied was determined based on the retention force observed. The wear resistances of PEEK and PEKK were evaluated by measuring the inner diameter of the inserted female part 10 times. Results: The maximum tensile stresses of PEEK and PEKK were 56.26±0.58 and 69.12±0.92 N, respectively, with the maximum stress required to remove the PEKK specimens from the abutment being 12.86 N higher than that required to remove the PEEK specimens. Furthermore, PEKK exhibited higher wear resistance than PEEK. Conclusion: This study evaluated custom-made removable implant-retained attachment components for overdentures, wherein the female parts were made of PEEK or PEKK. The retention stress and wear resistance were evaluated based on the type of attachment material, and the results showed that both types of attachment inserts demonstrated clinically acceptable results in terms of retention.

• Korean Journal of Materials Research
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• v.34 no.4
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• pp.194-201
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• 2024

In this study, the surfaces of two gold nanoparticles of different shapes were modified with hexadecyltrimethylammonium bromide (CTAB) and used for contact lenses. The polymer was based on 2-hydroxyethyl methacrylate (HEMA), and spherical and sea urchin-shaped gold nanoparticles were used as additives. CTAB was used to modify the surface of the sea urchin-shaped gold nanoparticles. To analyze the physical properties of the prepared contact lens, optical transmittance, refractive index, water content, contact angle, and atomic force microscope (AFM) were measured and evaluated. The results showed the nanoparticles did not significantly affect optical transmittance, refractive index, or water content of the lens, and tensile strength increased according to the ratio of the additive. The addition of the sea urchin-shaped nanoparticles resulted in lower wettability compared with the spherical nanoparticles, but somewhat superior tensile strength. In addition, it was found that the wettability of the lens was improved when the surface-modified sea urchin-shaped gold nanoparticles were added. The types of gold nanoparticles and surface modification methods used in this study are considered to have great potential for use in ophthalmic materials.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.3
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• pp.296-305
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• 2002

The main disadvantage of cement-retained implant restorations is their difficulty in retrievability. Advocates of cemented implant restorations frequently state that retrievability of the restoration can be maintained if a provisional cement is used. The purpose of this study was to find the optimal properties of provisional luting cements and the surface treatment of abutments in single implant abutment system. 30 prefabricated implant abutments, height 8mm, diameter 6mm, 3-degree taper per side, with light chamfer margins were obtained. Three commercially available provisional luting agents which were all zinc oxide eugenol type ; Cavitec, TempBond and TempBond NE were evaluated. No cement served as the control. TempBond along with vaseline, a kind of petrolatum (2:1 ratio) was also evaluated. Ten out of thirty abutments were randomly selected and abutment surfaces were sandblasted with $50{\mu}m$ aluminum oxide. Another ten abutments were sandblasted with $250{\mu}m$ aluminum oxide. A vertical groove, 1 mm deep and 5mm long was cut in each twenty abutments. Ten of them were sandblasted with $50{\mu}m$ aluminum oxide. The full coverage casting crowns were cemented to the abutments with the designated provisional luting agent. Specimens were stored in distilled water at $37^{\circ}C$ for 24 hours. Each specimen was attached to a universal testing machine. A crosshead speed of 0.5mm/min was used to apply a tensile force to each specimen. Within the limitations of this in vitro study, the following conclusions were drawn: 1. Tensile bond strength of provisional luting cements in no surface treatment decreased with the sequence of TempBond NE, TempBond, Cavitec, TempBond with vaseline, no cement. 2. Tensile bond strength more increased by surface treatment. Sandblasting with $250{\mu}m$ aluminum oxide exhibited the highest tensile bond strength in the abutment cemented with TempBond NE and sandblasting with $50{\mu}m$ aluminum oxide exhibited the highest tensile bond strength in cemented with TempBond. 3. In the aspect of a groove formation, tensile bond strength significantly increased in TempBond with vaseline only and the others had no significant effect on tensile bond strength.

• Restorative Dentistry and Endodontics
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• v.12 no.2
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• pp.45-53
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• 1987

The purpose of this study was to evaluate the tensile bond strength between composite resin and the human enamel. Three composite resin systems, two chemical (Clearfil Posterior, and Clearfil Posterior-3) and one light cure (Photo Clearfil-A), used with and without an intermediate resin (clearfil bonding agent), were evaluated under different amounts of load (10g, 200g and 200g for a moment) for in vitro tensile bond strength to acid-eched human enamel. Clinically intact buccal or lingual surfaces of 144 freshly extracted human permanent molars, embedded in acrylic were flattened with No #600 carborundum discs. Samples were randomly assigned to the different materials and treatments using a table of random numbers. Eight samples were thus prepared for each group(Table 2) these surfaces were etched with an acid etchant (Kurarey Co. Japan) in a mode of etching for 30 seconds, washing for 15 seconds, and drying for 30-seconds. During the polymerization of composite resin on the acid-etched enamel surfaces with and without bonding agent 10-gram, 200 gram and temporary 200 gram of load were applied. The specimens were stored in 50% relation humidity at $37^{\circ}C$ for 24 hours before testing. An universal Testing machine (Intesco model No. 2010, Tokyo, Japan) was used to apply tensile loads in the vertical directed (fig 5), and the force required for separation was recorded with a cross head speed of 0.25 mm/min and 20 kg in full scale. The results were as follow: 1. The tensile bond strength was much greater in applying a bonding agent than in not doing that. 2. The tensile bond strength of chemical cure composite resin was higher than that of light cure composite resin with applying on bonding agent on the acid-etched enamel. 3. In case of not applying a bonding agents on the acid-etching enamel, the highest tensile bond strength under 200 gram of load was measured in light cure composite resin. 4. The tensile bond strength under 200-gram of load has no relation with applying the bonding agent. 5. Under the load of 10-gram, There was significant difference in tensile bond strength as applying the bonding agent.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.314-318
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• 2004

This research is conducted to investigate weldability characteristics with various welding conditions on the 4 lap spot welded joint of structural steel sheets in automobile. The relationship between the tensile-shear strength and the indentation depth has been investigated to evaluate the weldability and the optimum welding conditions. The welding current and the welding time have a greatly affect to the tensile-shear strength compared to the electrode force. It was found that the indentation depth has a relatively close relationship with the expulsion occurrence. The optimum welding conditions were proposed for the 4 lap spot welded joint.