• Journal of the Korean Geotechnical Society
• /
• v.22 no.6
• /
• pp.41-49
• /
• 2006

This paper deals with development and dissipation of excess pore pressure induced by the cyclic load. Cyclic triaxial tests on reconstituted samples of weathered residual soils, which were widely used as construction materials in Korea, were performed. Test results showed that excess pore pressures developed under undrained condition increased with the increase of cyclic loads and confining pressures. And a new concept based on modified excess pore pressure ratio (MEPPR) was proposed for simply estimating excess pore pressures in terms of the number of cyclic load, irrespective of cyclic loads and confining pressures. Also, it was proposed that excess pore pressure ratio (EPPR) could be effectively utilized to estimate volumetric strains during dissipation which decreased as confining pressures increased. Consequently, concept and method to effectively estimate settlements under non-liquefied condition, induced by dynamic loads such as earthquake loads were evaluated based on laboratory test results for reconstituted weathered residual soils.

• Culinary science and hospitality research
• /
• v.20 no.1
• /
• pp.55-64
• /
• 2014

This study was performed to determine the effects of drying methods on the quality and physiological activities of blueberry. Blueberries(Vaccinium ashei) were dried by hot-air ($60^{\circ}C$), cyclic low pressure ($50^{\circ}C$), and freeze drying methods. They contained high properties of carbohydrates(68.48~80.00%), crude protein(1.63~5.41%), crude fat(0.58~1.25%), and ash(0.71~1.11%) regardless of the drying methods. There were no differences in pH according to the drying methods. Browning index increased as the drying temperature increased. The L, a values of the freeze-dried sample were higher than those of the other dried samples, whereas the b value of the cyclic low pressure dried sample was higher than that of the other samples. The free sugar contents of the hot-air sample were higher than those of the other samples. Vitamin C content of the freeze dried sample was higher than that of either the hot-air or cyclic low pressure dried sample. The contents of total polyphenols and anthocyanins were higher in the freeze dried sample. The DPPH radical scavenging activity of freeze drying sample was higher than that of either the hot-air or cyclic low pressure dried sample. The result indicated that there were no differences in product quality depending on the freeze-drying and cyclic low pressure drying methods.

• Applied Chemistry for Engineering
• /
• v.8 no.1
• /
• pp.1-7
• /
• 1997

We show that the usage of the cyclic pressure function in the freeze drying is more effective than the drying rate of the constant pressure process. The ultimate object of this process is to reduce energy costs by shortening the drying time. In this work, the concept of cyclic pressure function to decrease the drying time and the effects of the following factors on drying rate are considered ; pulse type, size in amplitude of pressure, size of intermediate time. Temperature for drying has always been maintained constantly at $20^{\circ}C$ and the pulse type could have found to give useful results than the constant pressure by altering chamber pressure from low pressure to high pressure Also, when the amplitude of the pulse is 0.4 torr and the intermediate time is six hour the drying rate was increased considerably.

• Structural Engineering and Mechanics
• /
• v.75 no.1
• /
• pp.101-108
• /
• 2020

The present study intends to analyze damage in thin-walled steel cylinders undergoing constant internal pressure and thermal cycles through use of anisotropic continuum damage mechanics (CDM) model coupled with nonlinear kinematic hardening rule of Chaboche. Materials damage in each direction was defined based on plastic strain and its direction. Stress and strain distribution over wall-thickness was described based on the CDM model and the return mapping algorithm was employed based on the consistency condition. Plastic zone expansion across the wall thickness of cylinders was noticeably affected with change in internal pressure and temperature gradients. Expansion of plastic zone over wall-thickness at inner and outer surfaces and their boundaries demarking elastic and plastic regions was attributed to the magnitude of damage induced over thermomechanical cycles on the thin-walled samples tested at various pressure stresses.

• Journal of Mechanical Science and Technology
• /
• v.14 no.10
• /
• pp.1151-1158
• /
• 2000

Combustion analysis based on cylinder-pressure provides a mechanism through which a combustion researcher can understand the combustion process. The objective of this paper was to identify the most significant sources of cycle-to-cycle combustion variability in a spark ignition engine at idle. To analyse the cyclic variation in a test engine, the burn parameters are determined on a cycle-to-cycle basis through the analysis of the engine pressure data. The burn rate analysis program was used here and the burn parameters were used to determine the variations in the input parameter-i. e., fuel, air, and residual mass. In this study, we investigated the relationship of indicated mean effective pressure (IMEP), coefficient of variation (COV) of IMEP, burn angles, and lowest normalized value (LNV) in a spark ignition engine in a view of cyclic variations.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.03b
• /
• pp.239-246
• /
• 2000

It has been generally much fine contents in West Coast of Korea. When cyclic shear stress causing liquefaction was estimated as using cyclic triaxial tests in these grounds, it didn't appear linear relations between deviator stress and confining stress where σ'₃ was more than 150 kpa. Namely, due to no normalization of cyclic shear stress ratio, the errors of this is increased. Therefore, more confining stress is increased, more increment of deviator stress is decreased. So, using linear relations between tanø'/sub d/ of dynamic internal friction angle and CSR where σ'₃ was less than 150 kpa, liquefaction of these grounds was evaluated. Also, as doing detail evaluation which had carried response analysis of earthquake, this appeared good results which was well compatible with empirical methods using N-value of SPT. It was thought that these result evaluated vulnerable liquefaction area more correct than existing methods. Also, characteristics of liquefaction in West Coast grounds was compared with clean sands, with analysis of behavior of pore pressure ratio and axial strain affected by fine contents, as cyclic loading was applied.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.12 no.2
• /
• pp.34-39
• /
• 2016

This paper presents a method to quantify R-ratio effect on J-integral under large-amplitude cyclic loading condition. Generally, monotonic tearing resistance curves are used to assess stability of cracked nuclear piping under seismic loading. However, it is well known that fracture toughness decrease at cyclic loading condition, according to R-ratio. For this reason, it is important to quantify the J-R curves under cyclic loading condition. To quantify the R-ratio effect, correction method which was proposed by Tranchand is considered. This method considers crack opening area in order to calculate modified J-integral. This method leads to an increase of fracture toughness. At R=-0.5 case, this method is good agreement with monotonic J-R curves. However, results show that this method has a limit to apply a large R-ratio case.

• Geotechnical Engineering
• /
• v.11 no.1
• /
• pp.23-40
• /
• 1995

In order to investigate the characteristics of the lateral earth pressure at rest under hysteretic Ko -loading l unloading conditions. Seven types of multicyclic models have been studied experimentally using dry sand. For this study a new type of Ko -oedometer appal attn is developed, and horizontal pressure is accurately measured. The multi cyclic models consist of largely 3 cases : (i) Ko-test under the same loading/unloading condition, (ii) multi-cyclic loading /unloading Ko -test exceeding the maximum prevertical stress, and (iii) multi-cyclic loading l unloading Ko -test within the mazimium prevertical stress. As a result, the multi -cyclic model showed that single-cyclic model could be extended as well, in which the exponents for unloading condition(a and a') and the reloading coefficients(m, and m*) were mainily dependent upon type of stress model, number of cycles and relati ve density.

• Geomechanics and Engineering
• /
• v.10 no.3
• /
• pp.325-334
• /
• 2016

Rock salt is a near-perfect material for gas storage repositories due to its excellent ductility and low permeability. Gas storage in rock salt layers during gas injection and gas production causes the stress redistribution surrounding the cavity. The triaxial cyclic loading and unloading tests for rock salt were performed in this paper. The elastic-plastic deformation behaviour of rock salt under cyclic loading was observed. Rock salt experienced strain hardening during the initial loading, and the irreversible deformation was large under low stress station, meanwhile the residual stress became larger along with the increase of deviatoric stress. Confining pressure had a significant effect on the unloading modulus for the variation of mechanical parameters. Based on the theory of elastic-plastic damage mechanics, the evolution of damage during cyclic loading and unloading under various confining pressure was described.

• Geomechanics and Engineering
• /
• v.21 no.5
• /
• pp.433-445
• /
• 2020

The weakening and softening behavior of soft clay subjected to cyclic loading due to the build-up of excess pore water pressure is well-known. During the design stage of the foundation of highways and coastal high-rise buildings, it is important to study the mechanical behavior of marine soils under cyclic loading as they undergo greater settlement during cyclic loading than under static loading. Therefore, this research evaluates the cyclic stress-strain and shear strength of untreated and treated marine clay under the effects of wind, earthquake, and traffic loadings. A series of laboratory stress-controlled cyclic triaxial tests have been conducted on both untreated and treated marine clay using different effective confining pressures and a frequency of 0.5 and 1.0 Hz. In addition, treated samples were cured for 28 and 90 days and tested under a frequency of 2.0 Hz. The results revealed significant differences in the performance of treated marine clay samples than that of untreated samples under cyclic loading. The treated marine clay samples were able to stand up to 2000 loading cycles before failure, while untreated marine clay samples could not stand few loading cycles. The untreated marine clay displayed a higher permanent axial strain rate under cyclic loading than the treated clay due to the existence of new cementing compounds after the treatment with recycled tiles and low amount (2%) of cement. The effect of the effective confining pressure was found to be significant on untreated marine clay while its effect was not crucial for the treated samples cured for 90 days. Treated samples cured for 90 days performed better under cyclic loading than the ones cured for 28 days and this is due to the higher amount of cementitious compounds formed with time. The highest deformation was found at 0.5 Hz, which cannot be considered as a critical frequency since smaller frequencies were not used. Therefore, it is recommended to consider testing the treated marine clay using smaller frequencies than 0.5 Hz.