• Geomechanics and Engineering
• /
• v.14 no.5
• /
• pp.439-451
• /
• 2018

The stress path characteristics of surrounding rock in the formation of gob were analysed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analysing the instability of deep gob was established based on the mechanism of stress relief in deep mining. The energy evolution law was investigated by introducing the local energy release rate index (LERR), and the energy criterion of instability of surrounding rock was established based on the cusp catastrophe theory. The results showed that the evolution equation of the local energy release energy of the surrounding rock was quartic function with one unknown and the release rate increased gradually during the mining. The calculation results showed that the gob was stable. The LERR per unit volume of the bottom structure was relatively smaller, which mean the stability was better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meet the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release, transfer and dissipation which provided an important reference for the study of the stability of deep mined out area.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.53 no.6
• /
• pp.153-163
• /
• 2011

This research describe improved algorithm that is able to decide terminal criterion of Evolutionary Structural Optimization (ESO), reducing load of calculation to search load path of concrete beam, and apply to agricultural facilities. The ESO method is that make to discrete structure, structural analyze each element stress through FEM. And repeat generation with next material condition to become for most suitable composing. Individual element introduces concept of zero stiffness, but zero stiffness decisions are gone to direction of exclusion. In this stduy, improve algorithm to be convergence by 'Rule of Alive or Die' in arrival because is most suitable. Also, existing terminal criterion lack consistency because that used depend on experience of researcher. This research procedure is fellowed. First, all modulus of elasticity assume a half of elasticity modulus of material, Second, structural analysis by FEM, Third, apply to the remove ratio and restoration ratio for the 'rule of alive or die'. Forth, reconstruct the element and material conditions. And repeat the first to forth process. The terminal time of evolutional procedure is the all elastic modulus of element changed to blank value or elasticity modulus value of original. Therefore, in this study, consist the algorithm for programming, and apply to the agricultural facilities with concrete.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.5
• /
• pp.842-849
• /
• 1997

The aim of this study is an investigation of the interaction of two micro hole defects affecting fatigue crack initation life and propagation behavior. The locatio of two micro hole defects was considered as an angle of alignment and the distance between the centers of two micro hole defects. The fatigue cracking behavior is experimented under bending. When micro defects are located close to each other, the fatigue crack initiation lives are varied with their relative locations. In the experiments, the area of local plastic strain strongly played a role in the fatigue crack initiation lives. Therefore we introduce a parameter which contains the plastic deformation area at stress concentrations and propose a fatigue crack initiation life prediction curve. In addition, the directions and propagation rates of fatigue cracks initiated at two micro hole defects are studied experimentally.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.6
• /
• pp.738-744
• /
• 2011

The reliability of blade root fixing section is required to endure the centrifugal force and vibration stress for the last stage blade of steam turbine in thermal power plant. Most of the domestic steam turbine last stage blades have finger type roots. The finger type blade is very complex, so the inspection had been performed only on the exposed fixing pin cross-section area due to the difficulty of inspection. But the centrifugal force and vibration stress are also applied at the blade root finger and the crack generates, so the inspection method for finger section is necessary. For the inspection of root finger, inspection points were decided by simulating ultra-sonic path with 3D modeling, curve-shape probe and fixing jig were invented, and the characteristics analysis method of ultrasonic reflection signal and defect signal disposition method were invented. This invented method was actually executed at site and prevented the blade liberation failure by detecting the cracks at the fingers. Also, the same type blades of the other turbines were inspected periodically and the reliability of the turbine increased.

• Geotechnical Engineering
• /
• v.10 no.1
• /
• pp.103-118
• /
• 1994

A series of drained triaxial testis was performed on a Band by use of cubical triaxial apparatus, in which three principal stresses could be applied independently. The stress -strain behavior on the same stress path with cubical triaxial test was analyzed with application of the isotropic single hardening constitutive model presented by Lade. The behavior predicted by the constitutive model presented good coincidence with experimental results during poi mary loading. However, the predicted Mo윤ding and reloading behavior wan much different from results of cubical triaxial testy. That is, the softening part of the prediction might result in a rough approximation, since the plastic work parameters of single hardening model were based on the hardening portion of the data.

• Journal of the Korean Home Economics Association
• /
• v.31 no.3
• /
• pp.29-46
• /
• 1993

The purpose of this study were to investigate the relation between home management ability and family life satisfaction of home makers, and to find out variables which influence them. The data were collected though the questionnaire whose respondent were 408 home makers in Kwang Ju and Kang Reung. The data were analyzed by various statistical method such as Cronbach's coefficient, factor analysis, frequency, percentage, mean, F-test, t-test, Duncan's multiple range test, regression analysis and path analysis. The results were as follow. 1. Home management ability score showed 68.5. Influential variables on home management ability were the level of education (husband and wife), occupation of husband and income as sociodemographic variables, and degree of resourcefulness recognition and of communication as psychological variables. 2. Family life satisfaction score showed 74.6. Influential variables on home management ability were the level of education (husband), occupation of husband and income as sociodemographic variables, and degree of resourcefulness recognition, of communication and of stress recognition as psychological variables. 3. The degree of communication was the highest influential variable to have influence on family life satisfaction. And the degree of resourcefulness recognition, of stress recognition, occupation of husband and wife, level of education(husband), number of children were variables to have directly and/or indirectly influence on family life satisfaction.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.8 s.227
• /
• pp.1221-1228
• /
• 2004

The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Table liner is one of grinding elements of vertical roller mill and is subjected to the cyclic bending stress by rollers load and the centrifugal force by rotation of table. It demands $4{\times}10^7$ cycle but has $4{\times}10^6{\sim}8{\times}10^6$ cycle. It fractures at the edge of grinding path of outside roller. The repair expense for it amounts to $30\%$ of total maintenance of vertical roller mill. Therefore, this study shows the fracture mechanism of table liner for vertical roller mill using HDM and fatigue analysis and makes the estimation for safety of vertical roller mill.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.3 no.4
• /
• pp.88-94
• /
• 2004

High manganese steel was maintained stability of Non-Magnetics performance. Fatigue tests were carried out under constant stress amplitude, using a non-magnetic high manganese steel. The fatigue crack growth mechanism of the high manganese steel was clarified from results such as observation of crack growth path and fracture surface. The result of getting this study was shown as following: 1) Remarkably ${\Delta}Kth$ of the high manganese steel is big with about 3 times of the general steel product. 2) In the low ${\Delta}K$ value region, da/dN is dependent on Kmax, and in the high ${\Delta}K$ value region, it is dependent on ${\Delta}Keff$. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. 3) It seems to ease the stress concentration of crack tip crack growth behavior in the ${\Delta}Kth$ vicinity by the generation of the secondary crack.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.8
• /
• pp.833-838
• /
• 2007

In tube hydroforming process, several defective products could be obtained such as bursting, wrinkling, folding, buckling. Because, especially, bursting is most frequently occurred failure among the well known failures, it is mostly important to predict the onset of bursting failure on tube hydroforming process. For most sheet metal forming processes, strain based forming limit diagram(FLD) is used often as a criteria to estimate the possibility of onset of the failures proposed above. However, FLD has a shortcoming that it is dependent on strain path while stress based diagram is independent on strain history. Generally, tube hydroforming consists of three main processes such as pre-bending, pre-forming, and hydroforming and it means that the strain histories of final products are nonlinear. Therefore, forming limit stress diagram(FLSD) is more suitable to predict forming limit for hydroforming parts. In this study, FLSD is applied to estimate bursting failure for an engine cradle of an automobile part. Consequently, it is proved that application of FLSD to predict forming limit is available for tube hydroforming parts.

• Journal of the Korean Society of Food Culture
• /
• v.33 no.1
• /
• pp.26-35
• /
• 2018

This study conducted an empirical analysis of the effects of job characteristics on work-family conflict relation and quality of life, as well as moderating effects in accordance with operation type, by targeting 245 dietitian/cooks working for contract foodservice companies. The results of this study are as follows. First, the autonomy and feedback had negative (-) effects on work-family conflict while functional diversity had positive (+) effects on work-family conflict. Job identity and job importance had no relation with work-family conflict. Second, work-family conflict had negative (-) effects on job satisfaction, work-family relation, job support, general happiness, and job environment while having positive (+) effects on job stress. Third, in all paths except for the path with effects of work-family conflict on job stress, there were no differences between the group of shops operating 365 days and the group of shops operating 5 days a week. It would be helpful to the effective operation of human resources by emphasizing the necessity of differentiated management for companies with shops operating 365 days and shops operating 5 days a week, as well as managing employees' job characteristic factors, work-family conflict, and even quality of life.