• Journal of Industrial Technology
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• v.20 no.B
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• pp.87-94
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• 2000

A study has been made on the behavior of microscopic fatigue crack growth at the stress level of the fatigue limit with ferrite-martensitic structures. For the above purpose, two types of the microstructures were prepared ; one is the microstructure having the ferrite encapsulating the islands of second phase martensite(FEM), the other is the microstructure with the martensite encapsulating the islands of ferrite(MEF). It has been pointed out that the fatigue limits of these microstructures are related to the critical stress at which the microcrack in the ferrite proceeds to the martensite. The high fatigue limit might be excepted for the MEF microstructure in which the critical crack length would be restricted within the second phase spacing in contrast with the FEM microstruture. However, the fatigue tests shows that no appreciable difference of the fatigue limits among them were recognized. Also, it turned out from the metallographic observations that the micro crack path is very much affected by the microstructures, so that the microcracks grow according to the 3-dimentional situation of its microstructures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.1013-1028
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• 2017

This paper presents key findings obtained from the numerical experiment investigating into the use of the cylindrical cavity for rock splitting operations. The stress and strain path analyses were carried out in order to provide a better insight into the crack formation. The principal stress analysis carried out along the crack line using the results obtained from these numerical analyses allowed the failure of the brittle material and the crack propagation to be investigated. This paper also suggested possible reasons for the change in crack direction observed during the rock splitting operations using the results obtained.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.391-399
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• 2001

Three-dimensional dynamic analysis of underground openings subjected to explosive loadings considering the effects of water saturation is carried out in this study. The surrounding rock mass is assumed to be the limestone with 13.5% of porosity. Two calculations are compared using as identical explosive charge; the first in dry rock of 13.5% porosity, the second in the identical rock, but in a fully saturated condition. It is shown that velocity, displacement, and stress time histories are higher in saturated rock than those in dry rock through numerical studies. It is also shown that underground openings in saturated rock masses could be significantly more vulnerable to the potential damages associated with shear failure than those in dry medium.

• Computers and Concrete
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• v.16 no.4
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• pp.625-642
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• 2015

Prestressed concrete bridges with corrugated steel webs have emerged as one of the promising bridge forms. This structural form provides excellent structural efficiency with the concrete flanges primarily taking bending and the corrugated steel webs primarily taking shear. In the design of this type of bridges, the flexural ductility and deformability as well as strength need to be carefully examined. Evaluation of these safety-related attributes requires the estimation of full-range behaviour. In this study, the full-range behaviour of beam sections with corrugated steel webs is evaluated by means of a nonlinear analytical method which uses the actual stress-strain curves of the materials and considers the path-dependence of materials. In view of the different behaviour of components and the large shear deformation of corrugated steel webs with negligible longitudinal stiffness, the assumption that plane sections remain plane may no longer be valid. The interaction between shear deformation and local bending of flanges may cause additional stress in flanges, which is considered in this study. The numerical results obtained are compared with experimental results for verification. A parametric study is undertaken to clarify the effects of various parameters on ductility, deformability and strength.

• International journal of steel structures
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• v.18 no.4
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• pp.1139-1152
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• 2018

Many studies on the application of stainless steels as structural materials in buildings and infra-structures have been performed thanks to superior characteristics of corrosion resistance, fire resistance and aesthetic appeal. Experimental investigation to estimate the ultimate strength and fracture mode of the fillet-welded connections of cold-formed austenitic stainless steel (STS304L) with better intergranular corrosion resistance than that of austenitic stainless steel, STS304 commonly used has carried out by authors. Specimens were fabricated to fail by base metal fracture not weld metal fracture with main variables of weld lengths according to loading direction. All specimens showed a block shear fracture mode. In this paper, finite element analysis model was developed to predict the ultimate behaviors of welded connection and its validity was verified through the comparison with test results. Since the block shear behavior of welded connection due to stress triaxiality and shear-lag effects is different from that of bolted connection, stress and strain distributions in the critical path of tensile and shear fracture section were investigated. Test and analysis strengths were compared with those by current design specifications such as AISC, EC3 and existing researcher's proposed equations. In addition, through parametric analysis with extended variables, the conditions of end distance and longitudinal weld length for block shear fracture and tensile fracture were suggested.

• Steel and Composite Structures
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• v.39 no.2
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• pp.135-148
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• 2021

Hollow structural section (HSS) columns have been increasingly popular due to their structural and architectural merits. However, practical difficulty lies in developing proper connections. The through-diaphragm connections are considered as suitable connection type that is widely adopted in Asian countries. However, the stress concentration occurs at the location connecting through-diaphragm and steel beam. Furthermore, the actual load path from the beam flange is not uniformly transferred to the HSS column as conventionally assumed. In this paper, tensile tests were further conducted on three additional specimens with beam flange plate to evaluate the load versus displacement response. The load-displacement curves, yield and ultimate capacity, ductility ratio were obtained. Furthermore, the strain development at different loading levels was discussed comprehensively. It is shown that the studied connection configuration significantly reduces the stress concentration. Meanwhile, simplified trilinear load-displacement analytical model for specimen under tensile load was presented. Good agreement was found between the theoretical and experimental results.

• Journal of Korean society of Dental Hygiene
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• v.20 no.6
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• pp.925-936
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• 2020

Objectives: This study proposes a hypothetical model for job stress, job satisfaction, organizational commitment, and turnover intention through social exchange relations (LMX, TMX) and political skills (LPS) for dental hygienists working in dental clinics hygienists. Methods: A self-administrated questionnaire was administered from April 1 to May 12, 2020, with 171 dental clinic hygienists participating in Seoul, Busan and Gyeongnam. The data were analyzed using SPSS and AMOS statistical analysis programs. Results: First, in the hypotheses testing, a total of 7 of 18 hypotheses were supported. Second, the relatonship between leader-member exchange (LMX) or team-member exchange (TMX) and turnover intention, a full mediating effect of job stress or job satisfaction or organizational commitment on that exchange was found. However, the leader's political skills on the path to turnover intention were not statistically significant. Conclusions: It is considered that education to enhance job skills, support for leisure activities, and time to communicate opinions with each other should be provided to create an organizational culture that satisfies all members, thereby lowering the intention to turnover.

• Journal of the Korean Geotechnical Society
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• v.22 no.1
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• pp.5-14
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• 2006

A simple and useful plane strain testing device was newly developed and its mechanical features were presented in this paper. The new testing device was designed to be capable of testing various stress paths expected under plane strain condition with only the conventional triaxial loading system. The applicability of the new testing device was systematically checked both by theoretical evaluation and by experiments. As a result, it was found that the new testing device has much wider range of application than the conventional plane strain testing devices.

• Geomechanics and Engineering
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• v.28 no.2
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• pp.171-180
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• 2022

Time-dependent stress-strain behaviour significantly influences the compressibility characteristics of the clayey soil. In this paper, a series of oedometer tests were conducted in two loading patterns and investigated the time-dependent compressibility characteristics of Indian Montmorillonite Clay, also known as black cotton soil (BC) soil, during loading-unloading stages. The experimental data are analyzed using a new non-linear function of the Elasto-Visco-Plastic Model considering Swelling behaviour (EVPS model). From the experimental result, it is found that BC soil exhibits significant time-dependent behaviour during creep compared to the swelling stage. Pore water entrance restriction due to consolidated overburden pressure and decrease in cation hydrations are responsible factors. Apart from it, particle sliding is also evident during creep. The time-dependent parameters like strain limit, creep coefficient and C_αe/C_c are observed to be significant during the loading stage than the swelling stage. The relationship between creep coefficients and applied stresses is found to be nonlinear. The creep coefficient increases significantly up to 630 kPa-760 kPa (during reloading), and beyond it, the creep coefficient decreases continuously. Several parameters like loading duration, the magnitude of applied stress, loading history, and loading path have also influenced secondary compressibility characteristics. The time-dependent compressibility characteristics of BC soil are presented and discussed in detail.

• Journal of Families and Better Life
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• v.9 no.2
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• pp.1-18
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• 1991

The purpose of this study is to find out influential variables related to Home Management Ability of urban home makers. This study focuses on the following aspects; 1) to find out which variables of sociodemographic variables (ie. home maker's age, level of education-husband, wife, job-husband, wife, income, duration of marriage), of psychological variables (ie. degree of resourcefulness recognition, degree of stress recognition, degree of life level recognition) have significant effects on home management ability. 2) to find out which variables of sociodemographic variables have significant effects on degree of resourcefulness recognition, of stress recognition, and of life level recognition. 3) to identify the influence of significant variables related to home management ability. Data was analyzed by frequency. percentage, mean , F-test, t-test, Duncan's multiple range test. regression analysis , path analysis pearson's r. x2-test. Major findings are as follows; 1) The level of education (husband , wife)and occupation of husband were variables to have influences on home management ability. 2) a. The level of education (husband, wife) and income were variable to have influences on degree of resourcefulness recognition. b. The employment of home makers. income, and the form of family were variables to have influences on degree of stress recognition. c. The level of education (husband, wife) occupation of husband , income , and duration of marriage were variables to have influences on degree of life level recognition. 3) There were significant relationships between home management ability and degree of resourcefulness recognition and of stress recognition (r=0.13, r=-0.12, p<.05). a. The higher degree of resourcefulness recognition, the higher home management ability (x2=11.17. df=4. p<.05) b. The higher degree of stress recognition, the lower home n=management ability (x2=14.64. df=4. p<.01) 4) The education level of homemakers (β =0.15) and income (β=0.12) were variables to have indirect influences on home management ability through the medium of the degree of resourcefulness recognition (β =0.13) 5) The employment of home makers (β=-0.17) was a variable to have indirect influence on home management ability through the medium of the degree of stress recognition(β=-0.12) 6) the education level of husband (β=0.16) and income (β=0.32) were variables to have direct influence on degree of life level recognition. 7) The degree of life level recognition (β=0.13) and education level of home makers (β=0.17) were variables to have indirect influences on home management ability through the medium of the degree of resourcefulness recognition (β=0.13) 8)The degree of life level recognition (β=-0.22) the employment of home makers(β=-0.17) and the from of family(β=-0.10) were variables to have indirect influences on home management ability through the medium of the degree of stress recognition.