• Journal of Advanced Marine Engineering and Technology
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• v.25 no.1
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• pp.87-94
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• 2001

Filament winding process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. And now it is well established as a versatile method for storage tanks and pipe for the chemical and other industries. In this study, tensile strength of a filament wound ring specimens were evaluated by split disk test fixture and dress disk test fixture. The results obtained from experiments were compared with the theoretical values obtained by the rule of mixture. And the purpose of this paper is to suggest an appropriate test method for the evaluation of tensile properties of filament wound structures. The tensile strength of a ring specimens tested by the dress disk test showed better agreement with the theoretical values than of a ring specimen tested by the split disk test because the stress concentration in edges of s split disk test fixture is more severe than the that of dress disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.11a
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• pp.15-20
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• 2000

Filament winding process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. And it is now well established as a versatile method for storage tanks and pipe for the chemical and other industries. In this study, tensile strength of a filament wound ring specimens were evaluated by split disk test fixture and dress disk test fixture. The results obtained from experiments were compared with the theoretical values obtained by the rule of mixtures in composites . And the purpose of this paper is the suggestion of an appropriate test method for the evaluation of tensile properties of filament wound structures. The tensile strength of a ring specimen tested by the dress disk test showed better agreement with the theoretical values than that of a ring specimen tested by the split disk test because the stress concentration in edges of a split disk test fixture is more severe than that of dress disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.203-207
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• 2000

Filament Winding Process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. And now well established as a versatile method for storage tanks and pipe for the chemical and other industries . In this study, tensile strength of a filament wound ring specimens were evaluated by split disk test fixture and dress disk test fixture , The results obtained from experiments were compared with the theoretical values obtained by the rule of mixtures. And the purpose of this paper is the suggestion of an appropriate test method for the evaluation of tensile properties of filament wound structures .The tensile strength of a ring specimen tested by the dress disk test showed better agreement with the theoretical values than of a ring specimen tested by the split disk test because the stress concentration in edges of a split disk test fixture is more severe than that of dress disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1349-1355
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• 1990

By examining the fatigue deformation properties of 12% Cr rotor steel which has been proved to have high fatigue and creep rupture strength around 600deg. C, authors reviewed major fatigue life prediction models such as Manson, Langer and Morrow equations, and following results were obtained. (1) A simple life prediction model for 12% Cr rotor steel was obtained as follows : DELTA..epsilon.$_{t}$ =2.18+.sigma.$_{u}$ /E+ $N^{-0.065}$+ $e^{0.6}$ $N^{-0.025}$ This equation shows that fatigue life, N, can be easily determined when total strain range, DELTA..epsilon.$_{t}$ and ultimate tensile strength, .sigma.$_{u}$ are known by simple tension test on the given test conditions. (2) Life prediction equation with equivalent maximum stress, DELTA..sigma./2, corresponding maximum strain in one cycle at room temperature is as follows: DELTA..sigma./w=-7.01logN+96.69+96.69

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.450-453
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• 2009

In order to overcome drawbacks of the advanced high strength steel such as inferior formability and large springback, the hot press forming process(HPF) has been being applied for forming of automotive sheet parts. Good formability and dimensional accuracy without springback as well as good crash performance of final products are the advantages of the HPF process. In this work, a method to characterize the mechanical properties of the HPF steel was developed based on the simple tension test at high temperatures and its finite element analysis, while it was applied to obtain strain rate and temperature dependent flow curves of the HPF steel. The final flow curves were represented by utilizing the Johnson-Cook type equation both in uniform and post-uniform deformation regions.

• Proceedings of the Safety Management and Science Conference
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• 2008.04a
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• pp.185-196
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• 2008

The objective of this study is to evaluate the mechanical behaviors and structural integrity of the weldment of high strength steel by using an acoustic emission (AE) techniques. Simple tension and AE tests were conducted against the 3 kind of welding test specimens. In order to analysis the effectiveness of weldability, joinability and structural integrity, we used K-means clustering method as a unsupervised learning pattern recognition algorithm for obtained multivariate AE main data sets, such as AE counts, energy, amplitude, hits, risetime, duration, counts to peak and rms signals. Through the experimental results, the effectiveness of the proposed method is discussed.

• Journal of the Korea Safety Management & Science
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• v.10 no.4
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• pp.127-134
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• 2008

The objective of this study is to evaluate the mechanical behaviors and structural integrity of the weldment of high strength steel by using an acoustic emission (AE) techniques. Monotonic simple tension and AE tests were conducted against the 3 kinds of welded specimen. In order to analysis the effectiveness of weldability, joinability and structural integrity, we used K-means clustering method as a unsupervised learning pattern recognition algorithm for obtained multi-variate AE main data sets, such as AE counts, energy, amplitude, hits, risetime, duration, counts to peak and rms signals. Through the experimental results, the effectiveness of the proposed method is discussed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.163-171
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• 2003

Most of existing beam-to-column connections are reinforced symmetrically because of reverse action cause by earthquake but in the weak-earthquake region like Korea connections reinforced asymmetrically can be used. Specially, the connections between CFT(Concrete Filled Tube) column and H-shape beam can be applied by simplified lower diaphragm. The tensile capacity of Combined Cross Diaphragm for upper reinforcing was tested by simple tension test and four types for lower reinforcing; Combined Cross, None, Horizontal T-bar and Vertical Plate were tested by ANSI/AISC SSPEC 2002 loading program. Horizontal T-bar and stud bolts in vertical flat bar transmit tensile stress from bottom flange of beam to filled concrete. All test specimens were satisfied 0.01 radian of inelastic rotational requirement in ordinary moment frame of AISC seismic provision. As the results of parametric studies, simplified lower diaphragms demonstrated an outstanding strength, stiffness and plastic deformation capacity to use sufficient seismic performance in the field.

• Journal of computational fluids engineering
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• v.13 no.4
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• pp.126-134
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• 2008

We developed a three dimensional Navier-Stokes code based on the level set method to simulate two phase flows with high density ratio. The Navier-Stokes equations with consideration of the surface tension effects are solved by using SIMPLE algorithm on a non-staggered grid. The present code is validated by simulating two test problems. First one is to simulate a rising bubble inside a cube. The thickness of the interface of the bubble is shown to affect the pressure distribution around the interface. As the thickness decreases, the pressure field around the interface becomes more oscillatory. As the bubble rises, a ring vortex is shown to form around the interface and the bubble eventually develops into an ellipsoidal shape. Merge of two bubbles inside a container is secondly tested to show the robustness of the present code for two phase flow simulation. Numerical results show stable and reliable behavior during the process of merging of two bubbles. The velocity and pressure fields around the interface of bubbles are shown oscillation free during the merging of two bubbles.

• International Journal of Concrete Structures and Materials
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• v.4 no.1
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• pp.63-68
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• 2010

With the emergence of ultra-high strength of concrete, the compression lap splice has become an important area of interest. According to ACI 318-08, a compression splice can be longer than a tension splice when high-strength concrete is used. By reevaluating the test results of compression splices and performing regression analysis, a simplified design equation for splice length in compression was developed based on the basic form of design equations for development/splice lengths of deformed bars and hooks in tension. A simple linear relation between $l_s/d_b$ and $f_{sc}\sqrt{f'_c}$ was assumed, and yields good values for the correlation coefficient and the mean and the COV (coefficient of variation) of the ratios of tests to predictions of splice strengths in compression. By including the 5% fractile coefficient of 0.83, a design equation for splice length in compression was developed. The splice length calculated using the proposed equation has a reliability that is equivalent to other provisions for reinforcing bars.