• Journal of the Semiconductor & Display Technology
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• v.3 no.2
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• pp.35-40
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• 2004

The total relaxed stress in annealing and the thermal strain/stress were obtained from the identification of the residual stress-free state using electronic speckle pattern interferometry (ESPI). The residual stress fields in case of both single and film / substrate systems were modeled using the thermo-elastic theory and the relationship between relaxed stresses and displacements. We mapped the surface residual stress fields on the indented bulk Cu and the 0.5 $\mu\textrm{m}$ Au film by ESPI. In indented Cu, the normal and shear residual stress are distributed over -1.7 GPa to 700 MPa and -800 GPa to 600 MPa respectively around the indented point and in deposited Au film on Si wafer, the tensile residual stress is uniformly distributed on the Au film from 500 MPa to 800 MPa. Also we measured the residual stress by the x-ray diffractometer (XRD) for the verification of above residual stress results by ESPI...

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.68-74
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• 2014

This study analyzes structural stress and fatigue about three types of automotive wheels. As maximum equivalent stresses at 1, 2 and 3 types become lower than the yield stress of material and deformations become minute, theses types are thought be safe on durability. Type 2 model has the most fatigue life among three kinds of types and the rest of models with fatigue lives are shown in the order of type 1 and 3. As the most fatigue frequency of type 2 model happens at the state of average stress and amplitude stress on the stress range narrower than type 1 or 3, type 2 model becomes most stable. In case of type 2 with the state near the average stress of 0 MPa and the amplitude stress of 300MPa, the possibility of maximum damage becomes 30%. This stress state can be shown as the most damage possibility. These study results can be effectively utilized with the design on automotive wheel by anticipating and investigating prevention and durability against its damage.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.12
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• pp.29-34
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• 2000

The effects of electrical stress on MILC(Metal Induced Lateral Crystallization) poly-Si TFT were studied. After the electrical stress was applied on the TFT’s which were fabricated by MILC process, off-state(VG<0V) current was reduced by $10^2{\sim}10^4$ times. However, when the device on which electrical stress was applied was annealed in furnace, the off-state current increased as annealing temperature increased. From the dependence of off-state current on the post-annealing temperature, activation energy of the trap states in MILC poly-Si thin films was calculated to be 0.34eV.

• Journal of Digital Convergence
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• v.17 no.5
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• pp.225-233
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• 2019

The purpose of this study was to investigate state-anxiety, dyadic adjustment and pregnancy stress in pregnant women and to identify factors influencing pregnancy stress. Data were collected 158 pregnant women. Data were analyzed using t-test, ANOVA, Scheffe's test, Pearson's correlation coefficient, stepwise regression analysis. There was statistically significant difference in state-anxiety on variable such as age. There were statistically significant difference in dyadic adjustment on variables such as education, religion, income. There was not statistically significant difference in pregnancy stress on variables. Pregnancy stress was positively correlated with state-anxiety. Pregnancy stress was negatively correlated with dyadic adjustment. State-anxiety was negatively correlated with dyadic adjustment. Factor influencing pregnancy stress was state-anxiety, which explained 25.1%. Findings provide useful information for further studies in pregnancy stress of pregnant women. Therefore, to reduce pregnancy stress of pregnant women, it is necessary to standardized nursing intervention program.

• Mood & Emotion
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• v.9 no.2
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• pp.78-86
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• 2011

Objectives : The aim of this study was to investigate relationship between perceived stress level, cognitive emotion regulation (CER) strategy and hope in group with high depressive symptom and higher-level perceived stress (H-H) and group with high depressive symptom and lower-level perceived stress (H-L) in patients with depression. Method : A total of 85 patients (over score of 16 by Beck depression Inventory; BDI) were surveyed with Cognitive emotion regulation questionnaire (CERQ), Perceived stress scale (PSS), and The state hope scale (SHS). Mean scores of CERQ and SHS were compared between relatively higher perceived stress and lower perceived stress groups. Correlation analysis and multiple linear regression analyses were performed to identify the effect of BDI, PSS and CER strategy on SHS in two groups. Results : In ANOVA, the level of hope and maladaptive CERQ score proved to be significantly lower among the H-H group than among the H-L group, while adaptive CERQ scores were not. In Regression analysis, the effective CER strategy in SHS were 'Refocus on planning' in H-H group, while it was 'Acceptance' CER strategy in H-L group. The final regression model explained 36% of the variance of SHS in H-H group and explained 21% of SHS in H-L group. Conclusion : These findings suggest that 'Refocus on planning' and 'Acceptance' cognitive emotion strategy are helpful in promotion of state hope on depression. Especially, 'Refocus on planning' strategy is more effective in high depressive symptom and high-perceived stress level, while 'Acceptance' strategy help to promote hope in high depressive symptom and low-perceived stress level in patients with depression.

• Steel and Composite Structures
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• v.24 no.5
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• pp.523-536
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• 2017

A layerwise (LW) formulation based on the Galerkin method is presented to investigate the three-dimensional stress state in long sandwich plate which is subjected to tension force and pure bending moment. Based on the Galerkin method and the LW discretization approach, the equilibrium equations of elasticity for the long plate are written in the weak form and discretized through the thickness of the plate. The discretized equations are written in terms of displacement components of the numerical layers. The governing equations of the plate are solved analytically for the free edge boundary conditions. The distribution of stress state especially the 3D stress state in the vicinity of the edges of the sandwich plate which is subjected to tension and pure bending is studied. In order to increase the accuracy, the out of plane stresses are obtained by integrating the equilibrium equations of elasticity. The convergence and accuracy of the predictions are studied and various numerical results are presented for distribution of the in-plane and out of plane stresses in symmetric and un-symmetric sandwich plates.

• Journal of Welding and Joining
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• v.10 no.1
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• pp.35-42
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• 1992

In this study, the stress concentration phenomenon for the dissimilar joints(ceramic-metal) bonded by thermal treating using a soft-insert metal(copper) was investigated with the aid of FEM(finite element method) under the load condition of uniform tension. The analysis was carried out by the supposing that stress states are plane stress or plane strain and elastic or elastic-plastic. And the Von Mises yield criterion and the incremental theory as plastic flow were adopted in this analysis. As the summarized results obtained, the stress concentration phenomenon was severer as the soft insert metal was thicker, in plane strain than in plane stress and in elastic-plastic state than in elastic state. Furthermore, the inducing mechanism of stress concentration was well expressed by the constraint forces(Fc) generated between the soft and the hard material.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.111-117
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• 1997

The sudden-stop apparatus is made to measure the residual stress of the infinitesimal area at the turning work surface by using the X-ray stress apparatus. This study is trued to make the cutting work the instantaneous stopping state in the normal working state. The behaviour of work material near the tool is estimated. The estimation method is that the distribution of residual stress can be also measured. The object is to clarify and control the mechanism to leave the adequate stress of the finishing surface. It's beginning is due to observe the occurrence state of the residual stress at the cutting work. The result obtained by this study is as follows. The chips are not separated from the work materials at all the cutting experiments of built-up edges or the shearing areas etc. which can be precisely observed by using the sudden-stop apparatus. The strain of movable system which can be seen at the part of working layer means the size of strain. This experiment proves that the working strain should be lessened to make the size of strain control the residual stress happened at the cutting surface.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.932-938
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• 2002

In structural applications, brittle materials such as soda-lime glasses and ceramics are usually subjected to multiaxial stress state. Brittle materials with cracks or damage by foreign object impacts are apt to fracture abruptly from cracks, because of their properities of very high strength and low fracture toughness. But in most cases, the residual strength of structural members with damage has been tested under uniaxial stress condition such as the 4-point bend test. Depending upon the crack pattern developed, the strength under multiaxial stress state might be different from the one under uniaxial. A comparative study was carried out to investigate the influence of stress state on the residual strength evaluation. In comparable tests, the residual strength under biaxial stress state by the ball-on-ring test was greater than that under the uniaxial one by the 4-point bend test, when a small size indendation crack was introduced. In the case that crack having an angle of 90deg. to the applied stress direction, the ratio of biaxial to uniaxial flexure strength was about 1.12. The residual strength was different from crack angles to loading direction when it was evaluated by the 4-point bend test. The ratio of residual strength of 45deg. crack to 90deg. one was about 1.20. In the case of specimen cracked by a spherical impact, it was shown that an overall decrease in flexure strength with increasing impact velocity, and the critical impact velocity for formation of a radial and/or cone crack was about 30m/s. In those cases that relatively large cracks were developed as compared with the case of indented cracks, the ratio of residual strength under biaxial stress state to one uniaxial became small.

• Geomechanics and Engineering
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• v.7 no.4
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• pp.403-430
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• 2014

Shale gas formations exhibit strong mechanical and strength anisotropies. Thus, it is necessary to study the effect of anisotropy on the hydraulic fracture initiation pressure. The calculation model for the in-situ stress of the bedding formation is improved according to the effective stress theory. An analytical model of the stresses around wellbore in shale gas reservoirs, in consideration of stratum dip direction, dip angle, and in-situ stress azimuth, has been built. Besides, this work established a calculation model for the stress around the perforation holes. In combination with the tensile failure criterion, a prediction model for the hydraulic fracture initiation pressure in the shale gas reservoirs is put forward. The error between the prediction result and the measured value for the shale gas reservoir in the southern Sichuan Province is only 3.5%. Specifically, effects of factors including elasticity modulus, Poisson's ratio, in-situ stress ratio, tensile strength, perforation angle (the angle between perforation direction and the maximum principal stress) of anisotropic formations on hydraulic fracture initiation pressure have been investigated. The perforation angle has the largest effect on the fracture initiation pressure, followed by the in-situ stress ratio, ratio of tensile strength to pore pressure, and the anisotropy ratio of elasticity moduli as the last. The effect of the anisotropy ratio of the Poisson's ratio on the fracture initiation pressure can be ignored. This study provides a reference for the hydraulic fracturing design in shale gas wells.