• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.105-112
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• 2008

The purpose of this study was to evaluate the contact angle made by 3 kinds of self etching primers (Clearfil SE Bond, AdheSE, and Tyrian) on dentin and to measure the microtensile bond strength of resin composite to dentin using these self-etching primers. Contact angle between each of 3 self etching primers and polished dentin surface was measured (n=30) by contact angle analyzer and the result was analyzed by One-way ANOVA. For the measurement of microtensile bond strength, polished dentin surface was treated with each of 3 self etching primers and dentin adhesives. Z-250 composite resin was built-up with a height of 5 mm on the adhesive-treated surface and light cured for 40s with a halogen light curing unit. Thereafter, each tooth was sectioned into slabs perpendicular to the bonded interface and trimmed (n=45). The microtensile bond strength was measured with universal testing machine and the result was analyzed with Kruskal-Wallis test. AdheSE group showed the highest contact angle followed by Clearfil SE group and Tyrian group (p<0.05). AdheSE group and Clearfil SE group showed significantly higher microtensile bond strength than Tyrian group (P<0.05).

• Tribology and Lubricants
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• v.9 no.2
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• pp.1-8
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• 1993

기어가 비교적 큰 하중과 고속의 운전상태에서 사용되는 경우 되풀이 응력에 의한 피로를 대상으로 하는 면압이나 굽힘강도 이외에 치면에서 발생되는 긁힘이나 융착(瀜着) 또는 용착(溶着)을 대상으로 한 스코어링(scoring) 강도를 고려하여야 한다. 스코어링은 주로 치의 이끝 부분에서 접촉방향으로 긁힘이 나타나는 손상으로 특징지워진다. 미국기어제조협회(AGMA)에서는 윤활막 파손에 의한 금속과 금속과의 접촉에 기인하여 발생되는 여러형태의 손상, 예를 들면 scuffing, seizing, galling 등을 광범위하게 스코어링으로 통칭하고 있다. 미국계통의 기술분야에서는 스코어링을 고온 스코어링(hot scoring)과 저온 스코어링(cold scoring)으로 구분하고 있다. 고온 스코어링은 고속 운전시 표면의 섬광온도(flash temperature)에 기인한 용착과 접촉방향으로 재료를 이탈시키는 형태를 나타내고, 저온 스코어링은 저속의 기어에서 윤활막 파단으로 표면에 줄질(filing)한 듯한 손상이 발생되는 것을 나타낸다. 유럽에서는 고온 스코어링 손상은 스커핑이라 하고 저온 스코어링손상만을 스코어링이라 부르고 있다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.293-308
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• 2012

The shear behavior at the particle/surface interface such as rock joint can determine the mechanical behavior of whole structure. Therefore, a fundamental understanding of the mechanisms governing its behavior and accurately estimation of the interface strength is essential. In this paper, PFC, a numerical analysis program of discrete element method was used to investigate the effects of the surface roughness on interface strength. The surface roughness was characterized by smooth, intermediate, and rough surface, respectively. In order to investigate the effects of particle shape and crushing on particle/surface interface behavior, one ball, clump, and cluster models were created and their results were compared. The shape of particle was characterized by circle, triangle, square, and rectangle, respectively. The results showed that as the surface roughness increases, interface strength and friction angle increase and the void ratio increases. The one ball model with smooth surface shows lower interface strength and friction angle than the clump model with irregular surface. In addition, a cluster model has less interface strength and friction angle than the clump model. The failure envelope of the cluster model shows non-linear characteristic. From these findings, it is verified that the surface roughness and particle shape effect on the particle/surface interface shear behavior.

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.409-419
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• 2013

A T-stub connection with high-strength bolts under tensile force is affected by prying action force and the contact force, among others, between members. If a design equation that does not consider such prying action force and contact force between members is not proposed, the T-stub under tensile force is liable to be fractured under the strength lower than the estimated design strength. To prevent it, many studies have proposed contact force estimation equations between members as well as the prying action force of the T-stub connection with high-strength bolts. However, no design equations based on such research have been proposed in South Korea. Therefore, this study aims to propose an estimation model for more accurate prying action force and contact force, and improve on previously proposed estimation models by implementing the three-dimensional, nonlinear finite element analysis. Throughout the results of three-dimensional, nonlinear finite element analysis, the prediction model proposed in this research for the prying action force and contact force of a T-stub provided much more accurate estimation than that of a existing prediction model previously suggested.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.198-203
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• 2023

Purpose. The aim of this study was to evaluate the proximal contact with a dental floss compared to a celluloid strip and a metal strip in normal dental arch and investigate what the most effective method for measuring is. Materials and methods. The subjects of this study was consisted with 20 healthy adults (10 males and 10 females) who had normal dentition. A dentist with more than 5 years of clinical experience evaluated the proximal contacts using a dental floss method, a celluloid strip method, and a metal strip method. Statistical analysis were performed by the use of Mann-Whitney U test. A P-value < .05 was considered statistically significant in all analysis. In addition, in the evaluation of proximal contact using a dental floss, the measurement of proximal contact using a celluloid strip and a metal strip was compared. Results. 80 % of all proximal contact was proper. Proper proximal contact was observed at the posterior area compared to the anterior area (P < .05). And male had proper proximal contact at the anterior area, female had proper proximal contact at the posterior area (P < .05). The consistency analysis between the results of the celluloid strip and the metal strip experiment on the results obtained from the floss using the consistency scale Kappa index shows that using celluloid strip is more advantageous than using the metal strip. Conclusion. Only 80% of all proximal contact was proper. Using celluloid strips with various thickness for evaluating of proximal contact is considered to be helpful for accurate measuring of proximal contact.

• Journal of the Korean Geosynthetics Society
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• v.5 no.3
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• pp.25-30
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• 2006

Large-scale direct shear tests were conducted in order to evaluate both the shear strength of soil itself and the interface shear strength between soil and woven geotextile. Two types of soil (sand and clay) with a woven geotextile were used in the experimental program. Total nine tests were conducted in this study. It has been found from the experimental results that the friction angle of sand itself were $30^{\circ}$. Interface friction angle between woven geotextile and sand showed $26^{\circ}$ indicating an efficiency of 87%. Similarly, interface friction angle between woven geotextile and clay showed $7.7^{\circ}$.

• Journal of Adhesion and Interface
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• v.23 no.3
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• pp.87-93
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• 2022

To analyze the interfacial property between the fiber and the matrix, work of adhesion was used generally that was calculated by surface energies. In this paper, it was determined what types of contact angle measurement methods were more accurate between static and dynamic contact angle measurements. 4 types of glass fiber and epoxy resin were used each other to measure the contact angle. The contact angle was measured using two types, static and dynamic contact angle methods, and work of adhesion, W_a was calculated to compare interfacial properties. The interfacial property was evaluated using microdroplet pull-out test. Generally, the interfacial property was proportional to work of adhesion. In the case of static contact angle, however, work of adhesion was not consistent with interfacial property. It is because that dynamic contact angle measurement comparing to static contact angle could delete the error due to microdroplet size to minimize the surface area as well as the meniscus measuring error.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2C
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• pp.73-80
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• 2006

The shear behavior of four different interfaces consisting of four types of geosynthetics was investigated, and both static and dynamic test for the geosynthetic interfaces were conducted. The monotonic shear experiments were performed by using an inclined board apparatus and large direct shear device. The interface shear strength obtained from the inclined board test was compared with calculated values from large direct shear tests. The comparison results indicated that direct shear tests show high possibility to over-predict the shear strength in the low normal stress range where direct shear tests are not performed. Curved failure envelopes were also obtained for interface cases where two static shear tests were conducted. By comparing the friction angles measured from three tests, i.e. direct shear, inclined board, and shaking table test, it was found that the friction angle might be different depending on the test method and normal stresses applied in the research. Therefore, it was concluded that the testing method should be determined carefully by considering the type of loads and the normal stress expected in the field with using the geosynthetic materials installed in the site.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.17-25
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• 2012

Shotcrete, rockbolt, and steel rib are installed to support ground after tunnel was excavated. These are important supports for NATM applied tunnels. Recently, lattice girder is increasingly used because it is easily installed. In this study, we developed a new lattice girder by increasing contacting area between spider and rod. To verify the effect of the new lattice girder, the 3-point and 4-point flexural strength tests were carried out for LG-$50{\times}20{\times}30$, LG-$70{\times}20{\times}30$, LG-$95{\times}22{\times}32$. As a result, in case of contacting area, strength of new SGS lattice girder is 17.95% higher than that of original lattice girder. In case of weakness point, strength of new SGS lattice girder is 19.37% higher than that of original lattice girder.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.3
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• pp.99-106
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• 1990

This study was aimed to see the effect of chemical grout on fresh granite joint shear strength. The grouting chemical used in this study was composed of 25% water glass. Direct shear tests were performed on the chemical filled joints, which had been made artificially with granite. The test results show that chemical grouted rock jonts have markedly reduced shear strength comparing with the ungrouted fresh joints and they sheared within chemical grout before the rock to rock contact had been established, while the ungrouted joint sheared between rock surfaces from the beginning of shear deformation. With chemical grouted joints the shear stress slowly reached its maximum without showing distinct peak shear strength. Therefore the shear stiffness of joints were decreased with increasing thickness of grout. but the shear strain at failure was increased with it.