• Journal of Welding and Joining
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• 제15권1호
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• pp.92-100
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• 1997

손상된 ASTM A-470 class 8 고압 증기 터어빈 로터강의 수명 연장을 위해 보수 용접이 행하여졌다. SAW 용접부의 미세경도 측정결과 모재의 경도는 VHN 253이었으나 모재에 근접한 열영향부의 경도는 VHN 227로 떨어졌다. 이와 같이 경도가 떨어진 영역을 "연화층"이라 정의하였으며 약 0.5-0.6mm의 크기를 나타내었다. 한편 크립 파단 시험시 파괴는 연화층 부근에서 일어났으며 593.deg. C와 19Ksi(132 Mpa)에서 파단시간은 772.4hr이었다. 연화층의 크기를 줄이기 위해서 MIG 및 TIG 용접이 행하여졌는데 연화층 크기는 MIG의 경우 0.3-0.4mm이고, TIG의 경우에는 입열량의 크기에 따라 0부터 0.4mm의 크기를 나타내었다. 그러나 크립 파단시간은 연화층 크기가 작아질수록 감소하였다. 특히 TIG 용접부의 경우 크립 파단시간은 입열량과 밀접한 관계를 나타내었는데 입열량이 클수록 파단시간은 길어졌다. 대부분의 파괴는 ICHAZ에서 발생되었으나 입열량이 감소함에 따라 파단부는 CGHAZ으로 이동하였다. 파단면은 tearing과 dimple을 갖는 입내파괴를 나타내었다.파괴를 나타내었다.

• 대한족부족관절학회지
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• 제22권1호
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• pp.21-25
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• 2018

Purpose: To analyze the correlation between a rupture of the hypovascular zone and early single heel raising after Achilles tendon repair. Materials and Methods: From January 2012 to August 2015, 68 patients, who underwent surgical treatment for a Achilles tendon rupture using Krackow method, were analyzed retrospectively. The patients were divided into two groups according to possibility of single heel raises within 3 months postoperatively. During the periodic outpatient observations, the visual analogue scale, Achilles tendon total rupture score (ATRS), and timing capable single heel raises were evaluated. In addition, the preoperative defect size and distance between the calcaneal osteotendinous junction and the rupture site were measured by ultrasound in all cases. Results: Twenty-three patients could perform a single heel raise within 3 months after surgery (early single heel raise group), and fortyfive patients could perform a single heel raise after 3 month postoperatively. The age, gender, body mass index, smoking, and operation delay were similar in the two groups. In addition, the defect size and distance between the calcaneal osteotendinous junction and rupture site as measured by preoperative ultrasound were similar (p=0.379 and p=0.631, respectively). On the other hand, when the rupture site was divided into the hypovascular zone (4~7 cm from calcaneal osteotendinous junction) and non-hypovascular zone, the hypovascular zone rupture rate was significantly lower in the early single heel raise group (60.9%, 14/23; 91.1%, 41/45; p=0.003). In logistic regression analysis, the odds of the hypovascular zone rupture group being capable of early single heel raise were 0.189 (p=0.017). The ATRS score at 3 months and 1 year after surgery were significantly higher in the early single heel raise group (p<0.001). Conclusion: Achilles tendon rupture at the hypovascular zone is a poor prognostic factor for early single heel raise and might affect the prognosis significantly after an Achilles tendon rupture operation.

• Journal of Welding and Joining
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• 제34권6호
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• pp.47-54
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• 2016

Post-Weld Heat Treatment (PWHT) cracking susceptibility in the weld heat-affected zone (HAZ) of reduced activation ferritic-martensitic (RAFM) steels was evaluated through stress-rupture tests. 9Cr-1W based alloys including different C, Ta and Ti content were prepared. The coarse grained heat-affected zone (CGHAZ) samples were simulated with welding condition of 30 kJ/cm heat input. CGHAZ samples consisted of martensite matrix. Stress rupture experiments were carried out using a Gleeble simulator at temperatures of $650-750^{\circ}C$ and at stress levels of 125-550 MPa, corresponding to PWHT condition. The results revealed that PWHT cracking resistance was improved by Ti addition, i.e., Ti contributed to the formation of fine and stable MX precipitates and suppression of coarse M23C6 carbides, resulting in improvement of stress rupture ductility. Meanwhile, rupture strength increased with increasing solute C content.

• 한국지진공학회논문집
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• 제24권5호
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• pp.219-232
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• 2020

The slip-weakening model developed by Ohnaka and Yamashita is extended over the breakdown zone by equating the scaling relationships for the breakdown zone and the whole rupture area. For the extension, the study uses the relationship between rupture velocity and radiation efficiency, which was derived in the theory of linear elastic fracture mechanics, and the definition of f_max given in the specific barrier model proposed by Papageorgiou and Aki. The results clearly show that the extended scaling relationship is governed by the ratio of rupture velocity to S wave velocity, and the velocity ratio can be determined by the ratio of characteristic frequencies of a Fourier amplitude spectrum, which are corner frequency, f_c, and source-controlled cut-off frequency, f_max, or vice versa. The derived relationship is tested by using the characteristic frequencies extracted from previous studies of more than 130 shallow crustal events (focal depth less than 25 km, M_W 3.0~7.5) that occurred in Japan. Under the assumption of a dynamic similarity, the rupture velocity estimated from f_max/f_c and the modified integral timescale give quite similar scale-dependence of the rupture area to that given by Kanamori and Anderson. Also, the results for large earthquakes show good agreement to the values from a kinematic inversion in previous studies. The test results also indicate the unavailability of the spectral self-similarity proposed by Aki because of the scale-dependent rupture velocity and the rupture velocity-dependent f_max/f_c; however, the results do support the local similarity asserted by Ohnaka. It is also remarkable that the relationship between the rupture velocity and f_max/f_c is quite similar to Kolmogorov's hypothesis on a similarity in the theory of isotropic turbulence.

• Journal of the Korean Wood Science and Technology
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• 제41권5호
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• pp.392-398
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• 2013

This study investigated the effect of test zone selection for evaluating bending strength of visually graded lumber. This will contribute to the understanding of two different methods under different standards. In method I, the major defect was randomly placed in the test specimen. In method II, the major defect was randomly placed in the maximum moment zone (MMZ). The results showed that the method II is more accurate for reflecting the effect of defects governing the grade of lumber. Unless the maximum strength-reducing defect (MSRD) is placed in MMZ, the evaluated value would be higher than that of MSRD. For evaluating the modulus of rupture (MOR) of visually graded lumber in test set-up of Method I, the Eq. (5) needs to be considered.

• 대한정형외과스포츠의학회지
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• 제6권1호
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• pp.45-49
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• 2007

목적: 전방 십자 인대 파열 시 동반되는 반월상 연골 파열에서 반월상 연골의 파열 부위 및 파열 형태 등을 분석하여 반월상 연골 파열이 봉합 가능한 부위인지를 예측하고 준비하고자 함이다. 대상 및 방법: 전방 십자 인대 파열로 전방 십자 인대 재건술을 시행 받은 환자 78예를 대상으로 하였다. 파열의 기준은 수상일로부터 12개월 이내에 수술한 경우로 하였으며 반월상 연골 파열 부위 및 형태를 술 전 시행한 자기 공명 영상 소견 및 전방 십자 인대 재건술시 시행한 관절경 소견을 종합하여 분류 하였다. 결과: 전방 십자 인대 파열이 있은 78예 중 50예 (64%)에서 반월상 연골 파열이 동반되었으며 외측 반월상 연골파열이 32예, 내측 반월상 연골 파열이 24예 이었고, 그 중 6예 에서는 양측 반월상 연골 파열이 동시에 있었다. 파열의 형태는 종주 파열이 30예 (53%)로 가장 많았고, 파열의 부위는 방사상 구역(radial zone)에 의하면 후각부 파열이 35예 (62%)이었고 환상 구역 (circumferential zone)에 의하면 red-red 구역이 22예 (39%)로 가장 많았다. 결론: 전방 십자 인대 파열과 동반된 반월상 연골 파열이 있는 경우 반월상 연골의 종주 파열이 가장 많았으며 이 들은 주로 관절경적 반월상 연골 봉합술로 치유될 가능성이 있는 부위의 파열이었다.

• Geomechanics and Engineering
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• 제34권6호
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• pp.683-696
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• 2023

The destruction and fracture of rock masses are crucial components in engineering and there is an increasing demand for the study of the influence of rock mass heterogeneity on the safety of engineering projects. The numerical manifold method (NMM) has a unified solution format for continuous and discontinuous problems. In most NMM studies, material homogeneity has been assumed and despite this simplification, fracture mechanics remain complex and simulations are inefficient because of the complicated topology updating operations that are needed after crack propagation. These operations become computationally expensive especially in the cases of heterogeneous materials. In this study, a heterogeneous model algorithm based on stochastic theory was developed and introduced into the NMM. A new fracture algorithm was developed to simulate the rupture zone. The algorithm was validated for the examples of the four-point shear beam and semi-circular bend. Results show that the algorithm can efficiently simulate the rupture zone of heterogeneous rock masses. Heterogeneity has a powerful effect on the macroscopic failure characteristics and uniaxial compressive strength of rock masses. The peak strength of homogeneous material (with heterogeneity or standard deviation of 0) is 2.4 times that of heterogeneous material (with heterogeneity of 11.0). Moreover, the local distribution of parameter values can affect the configuration of rupture zones in rock masses. The local distribution also influences the peak value on the stress-strain curve and the residual strength. The post-peak stress-strain curve envelope from 60 random calculations can be used as an estimate of the strength of engineering rock masses.

• Journal of Welding and Joining
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• 제8권4호
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• pp.27-34
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• 1990

Integranular corrosion behaviors of KAL (Knife Line Attack) and mechanical properties such as tensile and creep rupture were investigated for the tube material used for nearly 20 years under the condition of 463.deg. C and 28 $kg/cm^2$. Based and weld metal were austenitic stainless steel AISI 321 containing Ti, AISI 347 containing Nb, respectively. KLA is a kind of the intergranular corrosion which often occurs just near the HAZ (heat affected zone) of AISI 321 and AISI 347 stainless steel due to the grain boundary sensitization. In KLA zone, intergranular corrosion crack has propagated outwards from the inner surface and carbides of white and narrow band type assuming as (Cr, Fe) carbide were confirmed. All the delta-ferrite formed in the weld metal during weld solidification has been transformed into sigma-phase since delta-ferrte was exposed for 20 years at 463.deg. C. Elongation was very low at the range from room temperature to 600.deg. C and it was confirmed that creep-rupture properties were not consideralbly affected.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.845-850
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• 2007

The empirical AISC panel zone thickness provision$(t_z\geq(d_z+w_z)$/90) to prevent the cyclic shear buckling of the panel zone was proposed based on the test data of Krawinkler et al. (1971) and Bertero et al. (1973) However, no published records of the equation development or any other background information appear to be available. The calibrated finite element analysis results of this study indicated that the AISC provision was not reasonable. In this study, through including the effects of the column axial force and the aspect ratio of the panel zone, a new equation for the relative strength between the beam and the panel zone was proposed such that the proposed equation can prevent the panel zone shear buckling and reduce the potential fracture associated with the kinking of the column flanges.

• 한국안전학회지
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• 제17권2호
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• pp.76-84
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• 2002

The seismic behaviors of steel moment connections with different structural characteristics are investigated. The rupture index, which represents the fracture potential, is adopted to study the effect of concrete slab and the relative strength between the coin the beam, and Panel zone on the ductility of connections. The results show that the presence of slab increases the beam strength, imposes constraint near the beam top flange, and consequently, induces concentrated deformation near the beam access hall, which reduces the ductility of the connection. The total deformation capacity of the connection depends not only on the beam but also on the column and panel zone. Therefore, the detrimental slab effects and the relative strength should be considered in the seismic design of the connection.