• Journal of Computational Design and Engineering
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• v.3 no.2
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• pp.140-150
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• 2016

Normally all manufacturing and fabrication processes introduce residual stresses in a component. These stresses exist even after all service or external loads have been removed. Residual stresses have been studied elaborately in the past and even in depth research have been done to determine their magnitude and distribution during different manufacturing processes. But very few works have dealt with the study of residual stresses formation during the casting process. Even though these stresses are less in magnitude, they still result in crack formation and subsequent failure in later phases of the component usage. In this work, the residual stresses developed in a shifter during casting process are first determined by finite element analysis using ANSYS(R) Mechanical APDL, Release 12.0 software. Initially the analysis was done on a simple block to determine the optimum element size and boundary conditions. With these values, the actual shifter component was analyzed. All these simulations are done in an uncoupled thermal and structural environment. The results showed the areas of maximum residual stress. This was followed by the geometrical optimization of the cast part for minimum residual stresses. The resulting shape gave lesser and more evenly distributed residual stresses. Crack compliance method was used to experimentally determine the residual stresses in the modified cast part. The results obtained from the measurements are verified by finite element analysis findings.

• Structural Engineering and Mechanics
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• v.66 no.1
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• pp.45-59
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• 2018

The bi-material elastic system consisting of the pre-stressed hollow cylinder and pre-stresses surrounding infinite elastic medium is considered and it is assumed that the mentioned initial stresses in this system are caused with the compressing or stretching uniformly distributed normal forces acting at infinity in the direction which is parallel to the cylinder's axis. Moreover, it is assumed that on the internal surface of the cylinder the ring load which moves with constant velocity acts and within these frameworks it is required to determine the influence of the aforementioned initial stresses on the critical velocity of the moving load. The corresponding investigations are carried out within the framework of the so-called three-dimensional linearized theory of elastic waves in initially stresses bodies and the axisymmetric stress-strain state case is considered. The "moving coordinate system" method is used and the Fourier transform is employed for solution to the formulated mathematical problem and Fourier transformation of the sought values are determined analytically. However, the originals of those are determined numerically with the use of the Sommerfeld contour method. The critical velocity is determined from the criterion, according to which, the magnitudes of the absolute values of the stresses and displacements caused with the moving load approaches an infinity. Numerical results on the influence of the initial stresses on the critical velocity and interface normal and shear stresses are presented and discussed. In particular, it is established that the initial stretching (compressing) of the constituents of the system under consideration causes a decrease (an increase) in the values of the critical velocity.

• Korean Journal of Human Ecology
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• v.6 no.1
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• pp.15-27
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• 1997

The purpose of this study was to examine the effects from social supports and global self-worth on stresses for the children. The subjects were 438 children of the 5th grade in Elementary School and the first grade in Junior High School in Taejeon. The instruments used for this study were Children's Social Support, Global Self-Worth and Stress Scale. The data were analyzed using t-test, Pearson's correlation, multiple regression and path analysis. The main results of the study were as follows; 1. The stresses were different depending on age. When the family and the teacher give higher social supports, the 5th graders have higher global self-worth. When the family gives higher social supports, the stresses were decreased for the 5th graders. When the children have higher global self-worth, the stresses were decreased. 2. When the first graders in Junior High School experienced higher global self-worth and social supports from their friends, family, teacher, the stresses were decreased. 3. The first graders in Junior High School experienced more stresses than the 5th graders in Elementary School in parent-related and academic-related domains. But the first graders in Junior High School experienced less stresses than the 5th graders in Elementary School in friend-related domains. 4. The path analysis showed that social supports from friends and family explained 15% of the stresses for the 5th graders in elementary school. Social support from friends, family, and teacher explained 28% of the stresses for the first graders in Junior High School. 5. For the 5th graders in Elementary School, social supports from friends and family had direct influences on the global self-worth. And the global self-worth had direct influence on children's stresses. But for the first graders in Junior High School, social supports from friends, family, and teacher had direct influences on the global self-worth. And the social supports from friends had direct and indirect effects on children's stresses. 6. For predicting the stresses, the most significant variable was the global self-worth for the 5th graders in Elementary School and the first graders in Junior High School.

• Journal of Mechanical Science and Technology
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• v.14 no.1
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• pp.19-29
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• 2000

A viscoelastic finite element analysis is presented to investigate residual stresses occurred in a laminated cylindrical shell during cure. An incremental viscoelastic constitutive equation that can describe stress relaxation during the cure is derived as a recursive formula which can be used conveniently for a numerical analysis. The finite element analysis program is developed on the basis of a 3-D degenerated shell element and the first order shear deformation theory, and is verified by comparing with an one dimensional exact solution. Viscoelastic effect on the residual stresses in the laminated shell during the cure is investigated by performing both the viscoelastic and linear elastic analyses considering thermal deformation and chemical shrinkage simultaneously. The results show that there is big difference between viscoelastic stresses and linear elastic stresses. The effect of cooling rates and cooling paths on the residual stresses is also examined.

• Journal of Fisheries and Marine Sciences Education
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• v.21 no.1
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• pp.121-133
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• 2009

This study tested the relations of schools organizational climate and teachers' job stresses, perceived by 913 teachers from 45 elementary, junior- and senior-high schools. Pearson's correlation analysis for the relations between the sub-factors of both organizational climate and job stresses and cannonical correlation analysis for the relative contribution of individual variable of organizational climate upon job stress were applied for the test. The results of Pearson's correlation analysis showed that while 'intimacy', 'esprit', 'considerations', and 'production emphasis' climate had negative correlations with job stress sub-factors, 'disengagement' and 'aloofness' climate had positive correlation. 'Student guidance', a sub-factor of job stresses, did not have statistically significant correlation with any sub-factors of organizational climate. Findings from cannonical correlation analysis showed 2 significant cannonical functions to explain the relations between the sets of variables. 'Disengagement' from organizational climate positively contributed with 'authority forfeiture' and 'dissention and conflict' of the job stresses variables.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.61-68
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• 2000

In general, the design of membrane structures takes three steps. The first is shape finding analysis which is determination of initial equilibrium geometry with uniform stresses. The second step involve the computation of the stress-deformation to get completed membrane under various load conditions. The third step is to divide the membrane structures into several plan strips from the initial equilibrium states. This procedure is needed because of the initial shape has usually undevelopable curved surface and is called as "cutting patterns generation". By introducing this work, the deformation due to the initial stress is removed and approximate cutting patterns are generated. In this approach, however, material properties is not considered, therefore the error between the design stresses and actual stresses during the fabrication of plan strips should be occurred. In this paper, actual equilibrium shape analysis procedure for HP shape models is presented. The deviations of stresses between the design stresses and actual stresses are estimated.

• Journal of the Korean Society of Safety
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• v.23 no.3
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• pp.8-11
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• 2008

In the present work, the measurement method of residual stresses in thermal barrier coatings(TBCs) which are received the thermal shock is performed numerically. For this, the internal residual stresses are predicted by commercial FEM software ABAQUS because the hole drilling strain gage method measures residual stresses only near the surface of a material. As the results of this study, the residual stresses are linearly increased when the surface temperatures are over $1,200^{\circ}C$. It is also found that the values of residual stress are increased as the coating thickness is thin.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.3
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• pp.199-206
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• 1981

This paper presents a method of calculation of the stresses, the strains and the deflections due to welding in L shape and in T shape. Using step by step method of plasticity and establishing the equilibrium conditions in section, we calculated thermal stresses and strains during welding and in the final step of calculation we got the residual stresses, strains and the deflections due to welding. Also we measured the stresses and the strains with hole-drilling method and compared the results with the method of calculation presented in this paper. Because of its symmetry of section, the deflection due to welding in T shape is generally much less than that in L shape. The residual stresses are tensile in welded joints and HAZ, and compressive in base metal as butt welding of plates, but the compressive stresses in base metal decrease repidly as the points are away from welded joint except horizontal plates of T shape. The theoretical method of calculaiton presented in this paper coincides faily well with the experiment.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.148-155
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• 2003

Most manufacturing processes such as welding, cutting and molding generate residual stresses on the surface of manufactured parts. Between compressive and tensile residual stresses, the tensile residual stress is harmful to the surface integrity, which results in reduced fatigue life and causes other structural failures when the service stresses are superimposed on the residual stresses. In the research, the residual stresses in the hardened tool steel (SKD11) were measured using hole-drilling method. The specimens were prepared through hard turning. Most of residual stresses in the machined surface were compressive.

• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.469-477
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• 1993

Residual stresses is one of the major factors to degrade the magnetic properties of VCR magnetic heads. Vicker's indentation technique was adapted to estimate the residual stresses Residual stresses and distribution in the glass and ferrite were obtained after bonding ferrite with glass, varing the cooling rate. The compressive and tensile stresses were developed in the interface and gradually decreased with increasing distance from the interface. The stresses were decreased with a cooling rate. The mean values of residual stress in ferrite were 10MN/㎡, 8MN/㎡, 5MN/㎡ with cooling rate 10℃/min, 5℃/min, 1℃/min respectively. When the bonded sample was annealed above the glass transition temperature followed by cooling at 5℃/min cooling rate, the residual stress was reduced to 6MN/㎡.