• 대한치과보철학회:학술대회논문집
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• 2002.11a
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• pp.91-91
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• 2002

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.164-173
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• 2009

Purpose: The purpose of this study was to evaluate the effect of abutment material on screw-loosening before and after cyclic loading. Among the different materials of abutments, zirconia and metal abutment were used. Material and methods: Two types of implant systems: external butt joint(US II, Osstem Implant, Korea) and internal conical joint(GS II, Osstem Implant, Korea) were used. In each type, specimens were divided into two different kinds of abutments: zirconia and metal(n=5). The implant was rigidly held in a special holding to device ensure fixation. Abutment was connected to 30 Ncm with digital torque gauge, and was retightened in 30 Ncm after 10 minutes. The initial removal torque values were measured. The same specimens were tightened in 30 Ncm again and held in the cycling loading simulator(Instron, USA) according to ISO/FPIS 1480. Cycling loading tests were performed at loads 10 to 250 N, for 1 million cycles, at 14 Hz,(by subjecting sinusoidal wave from 10 to 250 N at a frequency of 14 Hz for 1 million cycles,) and then postload removal torque values were evaluated. Results: 1. In all samples, the removal values of abutment screw were lower than tightening torque values(30 Ncm), but the phenomenon of the screw loosening was not observed. 2. In both of the implant systems, initial and postload removal torque of zirconia abutment were significantly higher than those of metal abutment(P<.05). 3. In both of the implant systems, the difference in removal torque ratio between zirconia abutment and metal abutment was not significant(P>.05). 4. In metal abutments, the removal torque ratio of GS II system(internal conical joint system) was lower than that of US II system(external butt joint system)(P<.05). 5. In zirconia abutments, the difference in removal torque ratio between the two implant systems was not significant(P>.05). Conclusion: Zirconia abutment had a good screw joint stability in the condition of one million cycling loading.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.1
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• pp.27-36
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• 2012

As the popularity of implant treatment using a variety of problems have been reported. The proper torque values recommended by the manufacturer and the actual tightening force applied to the observed differences. Period for each product used in this study using different torque controllers accuracy for each of the comparisons, were analyzed. Error rate varies by the manufacturer, but all the products used in the reference period for increasing the error rate increased. Repeat the initial tightening, but the reference, showed a value close to the reference value for the width of change was larger. However, increasing the number of repeated tightening of the reference value for the error rate increased, but has reduced the width of the observed changes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.911-912
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• 2011

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.165-176
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• 2006

This paper deals with the experiment and construction case of concrete beams strengthened with wire rope using the tightening force of bolts. The mechanical bolting of wire rope for prestressing force is adopted, which is very easy for construction. For the flexural strengthening effect of the proposed method, the experiment was proceeded as follows. The main parameters of specimens, concrete strength is 24MPa, are initial prestressing forces of wire rope and the number of saddle. The flexural strengths of strengthened specimens compared with non-strengthened test piece were increased about 160%. Also, as the initial prestressing forces were increased, the crack and ultimate moments were increased. The number of saddle did not play an important role for the moment capacity. This proposed method as a construction example showed a more competitive method than any others.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.4
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• pp.419-432
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• 2010

Various torque generating devices have been developed and employed to apply a proper torque. These devices are usually calibrated by the manufacturer to apply appropriate torque levels for their specific implants and attachments. The purpose of this investigation was to determine and compare the accuracy of the torque controllers. In this study, 4 types of torque controllers were used; torque limiting device(TLD), torque indicating device(TID) and contra angle torque driver(CA), electronic torque controller(ETC). Digital torque gauge was employed to measure the de-torque value. Thirty cycles of tightening and loosening were repeated with each torque controller. All implant torque controllers have shown slight errors and deviations. The contra angle torque driver exhibited the most accurate data. In the limitation of this study, it would be recommended that the implant torque controllers should be checked whether uniformed and precise torque can be generated and a measuring error should be corrected.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.4
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• pp.243-248
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• 2012

Purpose: The purpose of this study is to compare the removal torque between prefabricated and customized implant abutment screw. Materials and methods: Three types of implant system (Osstem, Astra, Zimmer) were used. For each system, prefabricated abutment screw (control group) and customized abutment screw (test group) were used to connect the fixture and the abutment (n = 6). Digital torque gauze was used to control the tightening torque and the screws were tightened under each manufacturer's recommendation. 10 minutes after the connection the same tightening torque was applied, and 5 minutes after the second connection, the removal torque was measured. This procedure was repeated 10 times. In the cyclic loading test, 10 minutes after the first connection to the 6 groups (n = 3), the same tightening torque was applied, and a total of 1,000,000 time loading was applied at 30 degree angle to long axis with 50 N load. Repeated measures of ANOVA test (${\alpha}$=.05) was used as statistics to evaluate the effect of repeated loading number on the removal torque. Independent t-test was used to evaluate the difference in removal torque after cyclic loading. Results: The removal torque significantly decreased as the number of loading repetition increased (P<.05). In the 10 time repetition test, there was no significant difference between the prefabricated and customized implant abutment screw of the 3 implant system (P<.05). Also in the cyclic loading test, there was no significant difference between the prefabricated and customized implant abutment screw of the 3 implant system (P<.05). Conclusion: Within the limitation of this study, there was no significant difference in the removal torque between the prefabricated abutment screw and customized abutment screws.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.94-98
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• 2012

In order to serve the exact torque clamping force, the torque measurement system use the curve fitting algorithm by the least square. The corrected least square curve fitting algorithm which suggested in this paper can surpport more exact clamping force for fastner in variable industry field using the torque. At first, This paper introduces mathematical modeling for curve fitting algorithm, and simulate it. As a result, the corrected least square algorithm have shown lower standard error value than that of the used algoritm with torque, and so this corrected least square algorithm prove high accuracy than nomal least square algorithm. The suggested algorithm will contribute to improvement of cost and safety on industry field with bolt clamping force for precision industry parts, electronics parts, aircraft, aerospace, etc.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.119-126
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• 2022

This study proposed a BCM(Binding Column Method) that can reinforce the insufficient seismic force of piloti buildings that are not designed for seismic resistance. In addition, 4 reinforcement specimens and 1 reference specimen were manufactured for the proposed seismic reinforcement method. The effect of improving seismic performance before and after reinforcement was examined through repeated loading tests. As a result of experiment, seismic reinforcement specimen with BCM system showed hysteretic characteristics of a large ellipse with great energy dissipation ability and increased strength and stiffness, while reference specimen showed rapid reduction in strength and brittle shear failure column. In addition, it can be seen that the reinforcing effect is improved as the gap is narrow, the torque is large, and the thickness of the L-shaped steel sheet is thicker. The SC4 specimen showed the best seismic performance reinforcement effect.

• Composites Research
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• v.18 no.6
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• pp.9-18
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• 2005

With the wide applications of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joints have become a very important research area because the joints are often the weakest areas in composite structures. This paper presents an analytical study of the stress distributions in mechanically single-fastened and multi-fastened composite laminates. The finite element models which treat the pin and hole contact problem using a contact stress analysis are described. A dimensionless stress concentration factor is used to compare the stress distributions in composite laminates quantitatively In the case of single-pin loaded composite laminate, the effects of stacking sequence, the ratio of a hole diameter and the width of a laminate (W/D ratio), the ratio of hole diameter and distance from edge to hole (E/D ratio), friction coefficient and clamping force are considered. In the case of multi-pin loaded composite laminate, the influence of the number of pins, pitch distance, number of rows, row spacing and hole pattern are considered. The results show that P/D ratio and E/D ratio affect more on stress distributions near the hole boundary than the other factors. In the case of multi-pin loaded composite laminate, the stress concentration in the double column case is better than the other cases of multi-pin loaded composite laminate.