• Journal of Welding and Joining
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• 제20권2호
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• pp.59-64
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• 2002

When the vehicle travels in an actual road, resistance spot weldments of the vehicle structure are exposed to complex loading state. Since the fatigue strength in resistance spot weldment of vehicle body can be determined by effect of residual stresses and loading state of driving, estimating actual loading state and considering residual stress effect are needed. In this study, Fatigue stress-fatigue life relation concerned residual stress effect was obtained by thermo elastic plastic finite element analysis. And applied loading in resistance spot weldments of vehicle body was calculated by dynamic analysis. Presumption of fatigue life was performed using proposed method

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1113-1119
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• 2003

Experimental and numerical analyses were performed to characterize the fatigue behavior of spot welded joints in suspension mounting of a passenger car body. Static and fatigue tests were carried out for the tensile-shear and cross-tension specimens. S-N curve and fatigue strengths were obtained from the fatigue test of various specimens. Nonlinear finite element analysis showed that fatigue behavior of spot welded joints could be well estimated in terms of Von Mises stress at the nugget edge. Fatigue behavior of spot welded joint was represented by Von Mises stress better than the fatigue load.

• 치과방사선
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• 제22권1호
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• pp.7-22
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• 1992

The stress distributions on a human mandible for 18 load cases under two different boundary conditions (mouth open and closed), using the three dimensional finite element modeling were studied. Also, the expected fracture loads for each load cases were calculated by using the Von-Mises yield criterion. The model of a mandible with all teeth was composed of 2402 hexahedron elements and 3698 nodes. CAD techniques were used to analyze the 3-dimensional results. The conclusions of this study were as follows: 1. In the mouth open state, the maximum stress occured at the condyle neck; when the lateral load was exerted, the maximum stress occured at the load side condyle. 2. In the mouth closed state, when the loads were exerted on the mandibular body and chin, the maximum stress occured at the loaded area, and when the loads were exerted on the angle and ramus, the maximum stress occured at the condyle neck. 3. The expected fracture loads in each load case were calculated using the Von-Mises yield criterion, and it was confirmed that the mandible in the mouth open state was more easily fractured than that in the mouth closed state, and the expected fracture loads are lesser in the cases that load direction is parallel at mandibular plane than 45°. 4. The magnitudes of the expected fracture loads increased in the order of angle, ramus, body and chin in case of the mouth closed state, while chin, body, angle and ramus in case of the mouth open state. 5. The Von-Mises stress concentration regions analyzed by F.E.M. corresponded well with the results of clinical studies.

• 한국직업건강간호학회지
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• 제25권3호
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• pp.199-207
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• 2016

Purpose: The purpose of this study was to identify the obesity stress, weight bias and health care on Body Mass Index (BMI) in soldiers of non-combat area and to provide data for improving the quality of their life. Methods: This research involved 165 soldiers working in non-combat area. Data collection was conducted from November 1 to 20, 2015. Statistical analysis of the collected data were t-test and ANOVA, $Scheff{\acute{e}}$ method post hoc analysis, Pearson's correlation coefficients, and multiple liner regression using IBM SPSS 22.0. Results: The mean score of obesity stress was moderate ($19.05{\pm}5.28$). The mean score of weight bias was 69.03 and health care was 2.41 points. There are a positive correlation between obesity stress and BMI (r=.19, p<.05). Weight bias (r=-.19, p<.01) and health care (r=-.26, p<.01) among the subjects had negative correlations with BMI. In a multiple liner regression, obesity stress (${\beta}=.18$, p<.05), health care (${\beta}=-.18$, p<.05) were associated with BMI. Conclusion: Based on the findings that obesity stress and health care influence BMI, there is a need to control stress and to properly set proper guidelines on health care for soldiers.

• Animal Bioscience
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• 제37권1호
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• pp.16-27
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• 2024

Objective: The objective of this study was to investigate the effect of heat stress on the growth traits and genetic parameters of Thai native chickens. Methods: A total of 16,487 records for growth traits of Thai native chickens between 2017 and 2022 were used in this study. Data included the body weight at birth, body weight at 4, 8, and 12 weeks of age (BW0, BW4, BW8, BW12), average daily gain during 0 to 4, 4 to 8, and 8 to 12 weeks of age (ADG0-4, ADG4-8, ADG8-12), absolute growth rate at birth, at 4, 8, and 12 weeks of age (AGR0, AGR4, AGR8, AGR12). The repeatability test day model used the reaction-norm procedure to analyze the threshold point of heat stress, rate of decline of growth traits, and genetic parameters. Results: At temperature and humidity index (THI) of 76, Thai native chickens began to lose their growth traits, which was the onset of heat stress in this study. The estimated heritability, genetic correlation between animal and heat stress effect, and correlations between the intercept and slope of the permanent environmental effects were 0.27, -0.85, and -0.83 for BW, 0.17, -0.81, and -0.95 for ADG, 0.25, -0.61, and -0.83 for AGR, respectively. Male chickens are more affected by heat stress than female chickens with a greater reduction of BW, ADG, and AGR, values equal to -9.30, -0.23, -15.21 (in males) and -6.04, -0.21, -10.10 (in females) gram per 1 level increase of THI from the THI of 76. Conclusion: The influence of thermal stress had a strong effect on the decline in growth traits and genetic parameters in Thai native chickens. This study indicated that genetic models used in conjunction with THI data are an effective method for the analysis and assessment of the effects of heat stress on the growth traits and genetics of native chickens.

• 한국의류학회지
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• 제36권10호
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• pp.1050-1057
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• 2012

This study helps develop a cool body armor that maintains a tight-fit configuration to the body surface and evaluates the performance of newly developed body armor in a wear test. Three types of body armor were used for evaluation. One was a tight fitting body armor that was constructed to improve the degree of fit and ease of movement for Korean soldier using 3D technology. Another was ventilating body armor with attached spacers on the shoulder to reduce the thermal stress on the soldier. The third was a prevailing body armor produced by a Korean body armor company. In order to evaluate the performance of the body armor, a human wear test, a thermal mannequin test, and computational fluid dynamics (CFD) were executed. Five subjects participated in the wear test. Subjective wear sensation, total amount of sweat and dynamic change of clothing microclimate were observed during and after exercise on a treadmill; subsequently, it was found that subjects rated tight fitting body armor and ventilating body armor lighter, drier, and easier to move than the conventional body armor (p<.05). Total amount of sweat was the least in the case of ventilating body armor. The thermal resistance and vapor resistance of the ventilating body armor were improved remarkably. In addition, the skin temperature of the ventilating body armor with spacers was lower than the tight fitting body armor by at least $1^{\circ}C$ in the CFD result. It is noted that thermal-wet comfort of the 3D body armor with ventilating feature is superior to the conventional body armor, especially when the ventilating channel is not closed due to a backpack.

• 한국간호교육학회지
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• 제4권2호
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• pp.317-330
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• 1998

A descriptive-explanatory design was employed in this study. The purpose of this study was identify the level of assertiveness and clinical stress and the relationships between assertiveness and clinical stress in nursing students. A convenient sample of 143 nursing students was used for the study. The results of this study are as follows : 1) The level of assertiveness of nursing students was 3.65 in domain of contents, 3.68 in domain of voice, and 4.13 in domain of body language. Thus the level of asertiveness of nursing students was higher in body language. 2) The level of clinical stress of nursing students was 3.73 in domain of clinical education and evaluation by professors, 3.59 in domain of nurses, 3.32 in domain of human relationships, and 3.30 in domain of environment. Thus the level of clinical stress of nursing students was higher in clinical education and evaluation by professors. 3) The assertiveness of nursing students was found significantly related to human relationships. 4) The clinical stress of nursing students was found significantly related to satisfaction of nursing, satisfaction of clinical practice and priority of candidate for nursing. 5) The assertiveness of nursing students was not found significantly related to clinical stress in nursing students.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.87-90
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• 2001

In particle or short-fiber reinforced composites, cracking of the reinforcements is a significant damage mode because the broken reinforcements lose load carrying capacity. This paper deals with elastic stress distributions and load carrying capacity of intact and cracked ellipsoidal inhomogeneities. Three dimensional finite element analysis has been carried out on intact and broken ellipsoidal inhomogeneities in an infinite body under pure shear. For the intact inhomogeneity, as well known as Eshelby(1957) solution, the stress distribution is uniform in the inhomogeneity and non-uniform in the surrounding matrix. On the other hand, for the broken inhomogeneity, the stress in the region near crack surface is considerably released and the stress distribution becomes more complex. The average stress in the inhomogeneity represents its load carrying capacity, and the difference of average stresses between the intact and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The load carrying capacity of the broken inhomogeneity is expressed in terms of the average stress of the intact inhomogeneity and some coefficients. It is found that the broken inhomogeneity with higher aspect ratio still maintains higher load carrying capacity.

• 오토저널
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• 제13권5호
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• pp.42-50
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• 1991

According as the members and inner and outer plates of the automobile body structure have been thinned their thickness and have become high strength, each part of the body structure has been put more severe stress condition. Therefore, it has been increasingly required to improve the fatigue strength of the spot welded structures. As one of the improving methods for such problem, the author had previously proposed the method of alleviating stress concentration at nugget edge of the spot weld part and improving its fatigue strength [1]. But, because fatigue strength of the spot welded lap joint is influenced by its geometrical and mechanical factors, welding condition and etc., there needs a quantitative and systematic estimation method of them. In this report, by considering nugget edge of the spot weld part of the spot welded lap joint subjected to tensile load to the ligament crack, fatigue strength of various spot welded lap joints was estimated with the stress intensity factor (S.I.F.) K which is fracture mechanical parameter. It is known that evaluation of fatigue strength of the spot welded lap joint by the stress intensity factor (S.I.F.) K is more effective than the maximum stress $(\sigma_{ymax}$) at edge of the spot weld part on the center line of width of the plate.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1638-1645
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• 2006

This paper proposes a modeling technique which is able to not only reliably and easily represent the hysteretic characteristics but also analyze the dynamic stress of a taper leaf spring. The flexible multi-body dynamic model of the taper leaf spring is developed by interfacing the finite element model and computation model of the taper leaf spring. Rigid dummy parts are attached at the places where a finite element leaf model is in contact with an adjacent one in order to apply contact model. Friction is defined in the contact model to represent the hysteretic phenomenon of the taper leaf spring. The test of the taper leaf spring is conducted for the validation of the reliability of the flexible multi-body dynamic model of the taper leaf spring developed in this paper. The test is started at an unloaded state with the excitation amplitude of $1{\sim}2mm/sec$ and frequency of 132 mm. First, the simulation is conducted with the same condition as the test. Then, the simulations are conducted with various amplitudes in a loaded state. The hysteretic diagram from the test is compared with the ones from the simulation for the validation of the reliability of the model. The dynamic stress analysis of the taper leaf spring is also conducted with the developed flexible multi-body dynamic model under a dynamic loading condition.