• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.8
• /
• pp.1487-1494
• /
• 2002

In this study, to propose the prediction method of the crack growth under flight-simulation loading, crack growth tests are conducted on 2124-7851 aluminum alloy specimens. The prediction of crack growth under flight-simulation loading is performed by the stochastic crack growth model which was developed in previous study. First of all, to reduce the complex load history into a number of constant amplitude events, rainflow counting is applied to the flight-simulation loading wave. The crack growth, then, is predicted by the stochastic crack growth model that can describe the load interaction effect as well as the variability in crack growth process. The material constants required in this model are obtained from crack growth tests under constant amplitude loading and single tensile overload. The curves predicted by the proposed model well describe the crack growth behavior under flight-simulation loading and agree with experimental data. In addition, this model well predicts the variability of fatigue lives.

• Transactions of Materials Processing
• /
• v.29 no.1
• /
• pp.20-26
• /
• 2020

In the design of the metal forming processes, various types of ductile fracture criteria are used to predict crack initiation and to fabricate metallic products without any defects. However, the quantitative measurement method for determination of crack initiation is insufficient. It is very difficult to detect crack initiation in ductile metals with excellent deformability because no significant load drop is observed due to crack generation. In this study, the applicability of acoustic emission sensors, which are commonly used in facility diagnostics, to measure crack initiation during the metal forming process was analyzed. Cylindrical notch specimens were designed using the finite element method to induce a premature crack on the surface of pre heat-treated steel (ESW90) material. In addition, specimens with various notch angles and heights were prepared and compression tests were carried out. During the compression tests, acoustic emission signal on the dies and images of the surface of the notch specimen were recorded using an optical camera in real time. The experimental results revealed that the acoustic emission sensor can be used to detect crack initiation in ductile metals due to severe plastic deformation.

• Journal of Korean Society on Water Environment
• /
• v.26 no.4
• /
• pp.585-589
• /
• 2010

In order to evaluate the performance of a powdered activated carbon (PAC) contactor, two water treatment plants (WTP) were selected as target sites. The result of tracer tests showed that the plug flow portion of a bisymmetry-type contactor (H WTP) was more than 70%. A maze-type contactor (C WTP) also had more than 70% of plug flow portion after intra-basin baffles were installed. According to the operating data of the target WTPs, there was no clear evidence that the addition of PAC contributed to the removal of organics. However, the results of jar tests, conducted with the raw water taken from the H WTP, proved that PAC could remove dissolved organic carbon (DOC) to some extent when the proper velocity gradient was maintained. It was estimated that the production rate, defined as the ratio of the operating flowrate to the design flowrate, of the C and H WTPs was only 27 and 50%, respectively. Because of these lower production rates, the mixing intensity in the contactor was much less than the designed value and, finally, the performance of the PAC contactor was much lower than what was expected.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.1008-1014
• /
• 2010

When the industrial complex creation and the structures are constructed on the soft clayey ground, the long-term consolidation settlement greatly becomes a problem. In the present study, long-term consolidation tests to examine the change in the coefficient of secondary consolidation by the influence of the initial consolidation load and the influence of the consolidation load increment ratio($\Delta_p/_{p_0}$) in the normally consolidated state with an improved standard oedometer tester were examined. In addition, the finite difference method was executed by using one dimensional Elasto-Viscous model proposed by Yoshikuni et. al. From the result of the numerical analysis of the comparison laboratory tests, the applicability of the Elasto-Viscous model was verified from the agreement of the secondary consolidation process.

• Biomolecules & Therapeutics
• /
• v.15 no.1
• /
• pp.1-6
• /
• 2007

The application of the knowledge from the Human Genome Project to clinical medicine will be through both industrial drug development and the application of pharmacogenomics (PG) to patient care. The slow uptake of clinical innovations into clinical practice can be frustrating, but understanding the history of acceptance and sustaining medical innovation is critically important to position PG to succeed. This primarily means that PG tests must have legitimacy; they must be thoroughly validated, must be cost-effective, must be widely accepted by medical practitioners, must be supported by public policy, and must have a way of being easily incorporated into current medical practice. They must also lead to actionalble decisions by health care providers for their patients. Innovative PG assays should be tested in the best US laboratories, and reimbursement for testing must be accepted at the federal and state level. The companies providing these PG tests should be capable of sup-porting the interpretation and use of the test throughout medical practice. Advances such as the addition of PG information to drug labeling and the routine use of validated biomarkers to determine choice of cancer chemotherapy have been made. The PG research community must pay attention to the principles that have been previously described for acceptance and sustaining medical innovations in order for PG to be widely accepted in clinical medical practice.

• Research in Plant Disease
• /
• v.21 no.1
• /
• pp.20-23
• /
• 2015

A sequential planting method was developed to screen rice plants with durable resistance against rice blast in a short time, and applied for several years in Korean rice breeding program. In this study, we showed the advantages of a sequential planting method compared to other pathogenicity tests. The correlation analysis among three pathogenicity tests and other factors demonstrated that durable resistance depended on the average of diseased leaf area and the number of compatible pathogens. Significant correlations were found in the nursery test but not in the field test result. In addition, we traced changes in the pathogen population during sequential planting stages through re-isolation of the pathogen. The portion of compatible pathogens was increased during sequential planting. Through this study, we provide an effective sequential planting method and direction of durable resistance in a breeding program.

• Geomechanics and Engineering
• /
• v.11 no.3
• /
• pp.325-343
• /
• 2016

A total stress-based bounding surface model is developed to predict the undrained behaviour of saturated soft clays under cyclic loads based on the anisotropic hardening modulus field and bounding-surface theories. A new hardening rule is developed based on a new interpolation function of the hardening modulus that has simple mathematic expression and fewer model parameters. The evolution of hardening modulus field is described in the deviatoric stress space. It is assumed that the stress reverse points are the mapping centre points and the mapping centre moves with the variation of loading and unloading paths to describe the cyclic stress-strain hysteresis curve. In addition, by introducing a model parameter that reflects the accumulation rate and level of shear strain to the interpolation function, the cyclic shakedown and failure behaviour of soil elements with different combinations of initial and cyclic stresses can be captured. The methods to determine the model parameters using cyclic triaxial compression tests are also studied. Finally, the cyclic triaxial extension and torsional shear tests are performed. By comparing the predictions with the test results, the model can be used to describe undrained cyclic stress-strain responses of elements with different stress states for the tested clays.

• Earthquakes and Structures
• /
• v.12 no.1
• /
• pp.23-34
• /
• 2017

Composite steel plate deep beam (CDB) is proposed as a lateral resisting member, which is constructed by steel plate and reinforced concrete (RC) panel, and it is connected with building frame through high-strength bolts. To investigate the seismic performance of the CDB, tests of two 1/3 scaled specimens with different length-to-height ratio were carried out under cyclic loads. The failure modes, load-carrying capacity, hysteretic behavior, ductility and energy dissipation were obtained and analyzed. In addition, the nonlinear finite element (FE) models of the specimens were established and verified by the test results. Besides, parametric analyses were performed to study the effect of length-to-height ratio, height-to-thickness ratio, material type and arrangement of RC panel. The experimental and numerical results showed that: the CDBs lost their load-carrying capacity because of the large out-of plane deformation and yield of the tension field formed on the steel plate. By increasing the length-to-height ratio of steel plate, the load-carrying capacity, elastic stiffness, ductility and energy dissipation capacity of the specimens were significantly enhanced. The ultimate loading capacity increased with increasing the length-to-height ratio of steel plate and yield strength of steel plate; and such capacity increased with decreasing of height-to-thickness ratio of steel plate and gap. Finally, a unified formula is proposed to calculate their ultimate loading capacity, and fitting formula on such indexes are provided for designation of the CDB.

• Smart Structures and Systems
• /
• v.19 no.6
• /
• pp.679-694
• /
• 2017

The complexity, enlargement and irregularity of structures and multi-directional dynamic loads acting on the structures can lead to unexpected structural behavior, such as torsion. Continuous torsion of the structure causes unexpected changes in the structure's stress distribution, reduces the performance of the structural members, and shortens the structure's lifespan. Therefore, a method of monitoring the torsional behavior is required to ensure structural safety. Structural torsion typically occurs accompanied by displacement, but no model has yet been developed to measure this type of structural response. This research proposes a model for measuring dynamic torsional response of structure accompanied by displacement and for identifying the torsional modal parameter using vision-based displacement measurement equipment, a motion capture system (MCS). In the present model, dynamic torsional responses including pure rotation and translation displacements are measured and used to calculate the torsional angle and displacements. To apply the proposed model, vibration tests for a shear-type structure were performed. The torsional responses were obtained from measured dynamic displacements. The torsional angle and displacements obtained by the proposed model using MCS were compared with the torsional response measured using laser displacement sensors (LDSs), which have been widely used for displacement measurement. In addition, torsional modal parameters were obtained using the dynamic torsional angle and displacements obtained from the tests.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.6
• /
• pp.507-520
• /
• 2014

In this study, the surface displacement was investigated according to the various depth of cover when the tunnel excavation equipment was used in a clay soil. For this the laboratory scaled model test was carried out using the soil sample similar to the in-situ conditions. We carried out four tests according to tunnel depth(1.5D, 2.0D, 2.5D, 3.0D). The distribution of impact due to tunnelling was quantitatively analyzed in the three-dimension by measuring the surface displacement. In addition, the pattern of surface displacements was figured out.