• Journal of Advanced Marine Engineering and Technology
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• 제19권3호
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• pp.62-69
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• 1995

In order to investigate the effect of TiN coating on corrosion fatigue behavior of metal, the rotary bending corrosion fatigue tests were carried out in 3% NaCl solution by using the round bar specimens of high-speed steel, SKH-9, coated with TiN by PVD method. From the experimental results, fatigue strength of TiN coating steel in air was obvious improvement as compared with that of the substrate because of the restriction of dislocation movement in near surface of the substrate by hard thin film. In 3% NaCl solution, corrosion fatigue life of TiN coating specimen in high stress level was improvement same as in air. But in low stress level, corrosion fatigue life of TiN coating one was equivalent to that without coating, due to much crack initiated from corrosion pits formed at the substrate by failure of coating layer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.353-358
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• 2004

We got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at $25^{circ}C$, $-60^{circ}C$, $-80^{circ}C$, and $-100^{circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. And there is a difference between shot peened specimen and unpeened specimen. The purpose of this study is to predict the behavior of fatigue crack propagation as one of fracture mechanics on the compressive residual stress. Fatigue crack growth rate of shot peened metal was lower than that of unpeened metal. The compressive residual stress made an impact on tension and compression of the plasticity deformation in fatigue crack plasticity zone. That is. the constrained force about plasticity deformation was strengthened by resultant stress, which resulted from plasticity deformation and compressive residual stress in the process of fatigue crack propagation.

• Advanced Composite Materials
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• 제17권3호
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• pp.215-224
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• 2008

The present study aims to design a multilayer microstrip antenna with composite sandwich construction and investigate fatigue behavior of this multilayer SAS (surface antenna structure) that was asymmetric sandwich structure for the next generation of structural surface technology. This term, SAS, indicates that the structural surface becomes an antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, antenna elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.2 GHz. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of the SAS was obtained. The experimental results of bending fatigue were compared with single load level fatigue life prediction equations and in good agreement. The SAS concept is can be extended to give a useful guide for manufacturers of structural body panels as well as antenna designers.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.467-469
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• 2009

In this study, fatigue samples were prepared from cylinder head parts that are actually used in domestic (A) and foreign (B) automobiles; high-temperature, high-cycle, and low-cycle fatigue characteristics were then evaluated and compared. A study on the correlation between the microstructural factor and high temperature fatigue characteristic was attempted. The chemical compositions of the heat resistant aluminum alloys above represented A356 (A) and A319 (B), respectively. The result of the tensile strength test on material B at $250^{\circ}C$ was higher by 30.8MPa compared to material A. On the other hand, elongation was 8.5% higher for material A. At $130{\circ}C$, material B exhibited high fatigue life given high cycle fatigue under high stress, whereas material A showed high fatigue life when stress was lowered. With regard to the low-cycle fatigue result ($250^{\circ}C$) showing higher fatigue life as ductility is increased, material A demonstrated higher fatigue life. Through the observation of the differences in microstructure and the fatigue fracture surface, an attempt to explain the high-temperature fatigue deformation behavior of the materials was made.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1332-1336
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• 2005

It could make the LIghtweight Piezoelectric Composite Actuator (LIPCA) damageable by the cyclic large deformation. If the progressive microvoid coalescence of LIPCA interlaminar took place, the decrease of the stiffness and the weakness of stress transmission and fiber bridging effect would make the fatigue characteristics worse suddenly. Therefore, it is required to study the variation of fatigue behavior and interlaminar condition in LIPCA under resonant frequencies. These studies such as the changeable fatigue phase and interlaminar behavior of LIPCA affected by the resonant frequencies should be carried out due to the strong anisotropy of CFRP layer. Hence, these studies are as follows. 1) The residual stresses distribution of interlaminar in LIPCA using the Classical Lamination Theory (CLT). 2) Comparative analysis of interlaminar behavior for the intact LIPCA versus LIPCA containing an artificial delamination during resonant frequency.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.131-139
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• 1993

Low cycle fatigue characteristics of cast aluminum alloy A356 with a yield strength and ultimate strength of 229 and 283 MPa respectively was evaluated using smooth axial specimen under strain controlled condition. Reversals to failure ranged from 16 to 107. The cast aluminum alloy exhibited cyclically strain-gardening behavior. The results of low cycle fatigue tests indicated that the conventional low cycle fatigue tests indicated that the conventional low cycle fatigue life model was not a satisfactory representation of the data. This occurred because the elastic strain-life curve was not-log-log linear and this phenomena caused a nonconservative and unsafe fatigue life prediction at both extremes of long and short lives. A linear log-log total strain-life model and a bilinear log-log elastic strain-life model were proposed in order to improve the representation of data compared to the conventional low cycle fatigue life model. Both proposed fatigue life models were statistically analyzed using F tests and successfully satisfied. However, the low cycle fatigue life model generated by the bilinear log-log elastic strain-life equation yielded a discontinuous curve with nonconservatism in the region of discontinuity. Among the models examined, the linear log-log total strain-life model provided the best representation of the low cycle fatigue data. Low cycle fatigue life prediction method based on the local strain approach could conveniently incorporated both proposed fatigue life models.

• 한국공작기계학회논문집
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• 제14권3호
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• pp.74-80
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• 2005

Steel plates used for common structures are manufactured by rolling processes in general. The rolling direction traces generated during the processes have significant influences on mechanical properties and fatigue behavior of the plates. The objective of present study is to investigate those directional characteristics for the enhancement of steel structure safety. SS400 steel plates of 3 mm thickness are tested in this study, When the angles between the tensile loading direction and the rolling direction of the plates are increased, their yield strengths are increased and elongations are rather decreased. It is also shown that fatigue crack growth rates in the plates can be increased according to the changes of those mechanical characteristics. For the safety of the structures, therefore, it is critical to decrease the angles between the rolling direction and the tensile loading direction.

• Journal of Welding and Joining
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• 제12권4호
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• pp.151-161
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• 1994

FCAW has wide application in ship fabrication, maintenance and field erection. It has many advantages over SMAW.SAW and GMAW process. In many applications, the FCAW provides highquality weld metal. This method can reduce weld defects especially porosity and spatter. But the fatigue characteristics of those deposited metal have been rarely investigated. The purpose of this study is to investigate the cyclic stress-strain behavior and fatigue tests by the constant strain control were carried out on the rounded smooth specimen with deposited metal using the metal type flux cored wire. As the results of this study for the deposited metal welded by the metal type flux cored wire, the hardening or softening characteristics under cyclic load were investigated and cyclic stress-strain curve, strain-fatigue life curve, stress-strain function and fatigue life relation which are useful to estimate the fatigue life under the stress concentration condition were obtained.

• 한국자동차공학회논문집
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• 제11권4호
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• pp.117-124
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• 2003

The lightness of components required in automobile and machinery industry is requiring high strength of components. In particular, manufacturing process and new materials development for solving the fatigue fracture problem attendant upon high strength of suspension of automobile are actively advanced. In this paper, the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in high temperatures($100^{\circ}C$, $150^{\circ}C$, $180^{\circ}C$) was investigated with considering fracture mechanics. So, we can obtain followings. (1)Compressive residual stress decreases in high temperature, that is, with increasing temperature. (2)The effect of compressive residual stress on fatigue crack growth behavior in high temperature increases below $\Delta$K=17~19MPa (3)It was investigated by SEM that the constraint of compressive residual stress for plastic zone of fatigue crack tip was decreased in high temperature as compared with room temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.247-254
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• 2003

The lightness of components required in automobile and machinery industry is requiring high strength of components. In particular manufacturing process and new materials development for solving the fatigue fracture problem attendant upon high strength of suspension of automobile are actively advanced. In this paper, the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in high temperatures($100^{\circ}$, $150^{\circ}$, $180^{\circ}$) was investigated with considering fracture mechanics. So, we can obtain followings. (1)Compressive residual stress decreases in high temperature, that is, with increasing temperature. (2)The effect of compressive residual stress on fatigue crack growth behavior in high temperature increases below ${\Delta}K=17{\sim}19MPa$ (3)It was investigated by SEM that the constraint of compress residual stress for plastic zone of fatigue crack tip was decreased in high temperature as compared with room temperature.