• Tuberculosis and Respiratory Diseases
• /
• 제42권2호
• /
• pp.218-225
• /
• 1995

연구배경: 기도저항은 body plethysmograph를 이용하여 flow/alveolar pressure의 관계를 측정함으로써 얻어질 수 있는데, 기도저항이 정상인 경우 oscillooscope 상에서 얻어지는 resistance curve가 거의 linear 하나 증가된 경우에는 그 모양이 기울어지거나 loop을 형성하는 경우가 많아 이러한 curve를 분석하여 환자의 임상평가에 도움이 되는 결과를 얻고자 하였다. 방법: 기도저항이 증가되어 있는 환자를 대상으로 body plethysmograph에서 quiet breathing시에 얻어진 resistance curve의 형태를 분석하여 폐기능을 비교하였다. 결과: 1) Resistance curve는 type 1: linear, type 2: ovoid, type 3: sigmoid, type 4: scoop, type 5: paisley의 5가지 형태로 구분할 수 있었으며, 1예를 제외한 type 3과 type 4 및 5는 loop을 형성하였다. 2) Curve의 형태가 특정 질환에 특징적이지는 않았으나 급성질환은 주로 type 1, 및 2, 만성기류폐쇄는 주로 type 3, 4 및 5에 속하였으며, 기관지 천식이나 오래된 폐결핵은 그 정도에 따라 type 1 에서 5까지의 형태를 모두 보였다. 3) Type 1에서 type 5로 갈 수록, loop을 형성 할 수록 기도폐쇄가 심하고 기도저항이 증가되며 잔기량이 커지는 경향을 보였다. 결론: 기도저항을 측정할 경우 기도저항의 측정치 뿐 아니라 resistance curve를 분석하여 기도폐쇄와 air trapping의 정도를 판단하는데 도움을 얻을수 있으며, resistance curve의 모양이 특정 질환에 특징적이지는 않았지만 호기시 loop이 형성되는 경우 심한 기도폐쇄를 시사하였다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2006년도 추계 학술발표회
• /
• pp.409-429
• /
• 2006

In designing rock-socketed drilled shaft, bearing capacity evaluation is very important because the maximum values of base and side resistance are not generally mobilized at the same value of displacement, FHWA and AASHTO code suggest different ultimate bearing capacity formular according to rock type and shaft settlement. In domestic code suggest base resistance and side resistance can be added on condition that after confirming the result of field load test with axial load transfer test. This paper shows that static load test and hi-directional load test result analysis of deep rock-socketed drilled shaft in three different sites. Load-settlement curve, t-z, and q-w curve in rock-socketed part were calculated and compared. t-z curve in weathered and soft rock showed no deflection softening behavior in pretty large strain (about 2-3% of diameter). Ultimate resistance could be the summation of side resistance and base resistance in rock-socketed drilled shaft in domestic sites.

• 대한기계학회논문집A
• /
• 제33권9호
• /
• pp.930-937
• /
• 2009

The estimation method of the fracture resistance curve for the pipe specimen was proposed using the load ratio method for the standard specimen. For this, the calculation method of the load - CMOD curve for the pipe specimen with the common format equation(CFE) was proposed by using data of the CT specimen. The proposed method agreed well with experimental data. The J-integral value and the crack extension were calculated from the estimated load - CMOD data. The fracture resistance curve was estimated from the calculated J-integral and the crack extension. From these results, it have been seen that the proposed method is reliable to estimate the J-R curve of the pipe specimen.

• 한국해양공학회지
• /
• 제10권2호
• /
• pp.98-105
• /
• 1996

A method is proposed to evaluate the elastic-plastic fracture resistance curve only with load displacement records without the crack length measurement in CT specimen. This method is based on the idea that the effect of plastic deformation and the crack growth can be measured only by using a load-displacement record. If we know the reference-load curve representing the hardening of specimen, then the crack extension can be calculated by the elastic compliance determined from the load ratio. The results of this proposed method were compared to those of the elastic-plastic fracture resistance curve for the ASTM standard unloading compliance method. The experimental results for two kinds of ductile materials showed that the proposed method well simulates the material J-R curves. This method is currently applied for CT specimens. but it can be extended to the other specimen geometries.

• Journal of Welding and Joining
• /
• 제17권2호
• /
• pp.97-103
• /
• 1999

The dynamic resistance monitoring in primary circuit is one of the important issues. Because in-process and real time quality assurance of resistance spot weld is needed to increase the product reliability. In this study, new dynamic resistance detecting method is proposed as a practical manner of weld quality assurance using instantaneous current and voltage measured at the primary circuit. and also, various patterns of primary dynamic resistance curve are characterized with the macro photograph and the weldability lobe curve. It is found that the primary dynamic resistance patterns are basically similar to those of the secondary, but there is evident advantage such as no extra devices are needed to obtain the quality information and eventually real time feedback control will be possible.

• Geomechanics and Engineering
• /
• 제29권4호
• /
• pp.407-420
• /
• 2022

Embedded piles, which are typically used in Korea, are precast piles inserted into prebored ground with cement paste. Dynamic pile tests tend to underestimate the bearing capacity of embedded piles because of the undeveloped shaft resistance prior to the curing of the cement paste and the insufficient energy transferred after the curing. In this study, a resistance combination method using the base resistance before the cement paste is cured and the shaft resistance after the cement paste is cured is proposed to obtain a combined load-settlement curve from dynamic pile tests. Two pairs of embedded piles with diameters of 600 and 500 mm are installed. Each pair comprises one pile for the dynamic pile test and another pile for the static load test. The shape of the load-settlement curve obtained using the proposed method is similar to that obtained from the static load test. Thus, the resistances evaluated using the proposed method at selected settlements are similar to those obtained from the static load test. This study shows that the resistance combination method may be used effectively in dynamic pile tests to accurately evaluate the bearing capacity of embedded piles.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제7권1호
• /
• pp.195-211
• /
• 2015

Flat plate friction lines have been used in the process to estimate speed performance of full-scale ships in model tests. The results of the previous studies showed considerable differences in determining form factors depending on changes in plate friction lines and Reynolds numbers. These differences had a great influence on estimation of speed performance of full-scale ships. This study was conducted in two parts. In the first part, the scale effect of the form factor depending on change in the Reynolds number was studied based on CFD, in connection with three kinds of friction resistance curves: the ITTC-1957, the curve proposed by Grigson (1993; 1996), and the curve developed by Katsui et al. (2005). In the second part, change in the form factor by three kinds of friction resistance curves was investtigated based on model tests, and then the brake power and the revolution that were finally determined by expansion processes of full-scale ships. When three kinds of friction resistance curves were applied to each kind of ships, these were investigated: differences between resistance and self-propulsion components induced in the expansion processes of full-scale ships, correlation of effects between these components, and tendency of each kind of ships. Finally, what friction resistance curve was well consistent with results of test operation was examined per each kind of ships.

• 대한기계학회논문집A
• /
• 제29권1호
• /
• pp.107-114
• /
• 2005

In order to analyze the elastic-plastic fracture behavior of a structure, the fracture resistance curve of the material should be known first. The standard CT specimen was used to obtain the fracture resistance curves of a piping system. However, it is known that the fracture resistance curve by the standard CT specimen is very conservative to evaluate the integrity of a structure. Also the fracture resistance curve is effected by the specimen geometry and the dimensions because of the constraint effect. The objective of this paper is to be certain the conservativeness of the fracture resistance curve by the standard CT specimen and to provide an additional safety margin. For these, the fracture tests using a real pipe specimen and the standard CT specimen test were performed. A 4-point bending jig was manufactured for the pipe test and the direct current potential drop method was used to measure the crack extension and the length for the pipe test. Also finite element analyses were performed with a CT specimen and a pipe in order to prove the additional safety margin. From the result of tests and analyses of the pipe and the standard CT specimen, it was observed that the fracture analysis with the standard CT specimen is conservative and the additional safety margin was proved.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1240-1245
• /
• 2003

Reduced activation ferritic steel (JLF-1) is considered as a promising candidate material for blanket or first-wall structure of D-T fusion reactors. The fracture tests of fracture resistance curve (J-R curve) and $J_{IC}$ are desirable to investigate the exact fracture toughness of JLF-1 steel, since it has a high ductility. The fracture toughness of JLF-1 steel is affected by the configuration of test specimen such side groove, specimen thickness or specimen size. In this study, the fracture toughness tests were performed with various size(plane size and thickness) and various side groove of specimens. The test results showed the standard specimen with the side groove of 40 % represented a valid fracture toughness. The fracture resistance curve increased with increasing plane size and decreased with increasing thickness. However, the fracture resistance curve of half size specimen was similar to that of the standard specimen.

• 대한기계학회논문집A
• /
• 제28권4호
• /
• pp.352-361
• /
• 2004

One important element of the Leak-Before-Break analysis of nuclear piping is how to determine relevant fracture toughness (or the J-resistance curve) for nonlinear fracture mechanics analysis. The practice to use fracture toughness from a standard C(T) specimen is known to often give conservative estimates of toughness. To improve the accuracy, this paper proposes a new method to determine fracture toughness using a nonstandard testing specimen, curved wide-plate in tension. To show validity of the proposed curved wide-plate test, the J-resistance curve from the full-scale pipe test is compared with that from the curved wide-plate test and that from the C(T) specimen. It is shown that the J-resistance curve form the curved wide-plate tension test is similar to, but that from the C(T) specimen is lower than, the J-resistance curve from the full-scale pipe test. Further validation is performed by investigating crack-tip constraint conditions via detailed 3-D FE analyses, which shows that the crack-tip constraint condition in the curved wide-plate tension specimen is indeed similar to that in the full-scale pipe under bending.