• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1552-1561
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• 1996

It requires uch time and cost to obtain the fatigue crack growth life and fatigue crack growth path morphlogy from the fatigue crack growth tests. In this study, the Monte-Carlo simulation program was developed to predict the fatigue crack growth lofe and fatigue crack growth path morphology of metal matrix composites. Fatigue crack growth lives of 5%, 10%, 15%, 20%, 25% and 30% $SiC_w$/Al composites were predicted by usign the Monte-Carlo Simulation. And the fatigue crack growth lives of 25% $SiC_w$/Al and Almatrix from Monte-carlo simulation were compared with fatigue life from experiments in order to verify the accuracy of Monte-Carlo Simulation program.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.232-237
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• 2001

The evaluation of specimen thickness effect of fatigue crack growth life by the simulation of probabilistic fatigue crack growth is presented. In this paper, the material resistance to fatigue crack growth is treated as a spatial stochastic process, which varies randomly on the crack surface. Using the previous experimental data, the non-Gaussian(eventually Weibull, in this report) random fields simulation method is applied. This method is useful to estimate the probability distribution of fatigue crack growth life and the variability due to specimen thickness by simulating material resistance to fatigue crack growth along a crack path.

• Structural Engineering and Mechanics
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• v.35 no.3
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• pp.283-299
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• 2010

This paper addresses the numerical simulation of fatigue crack growth in arbitrary 2D geometries under constant amplitude loading by the using a new finite element software. The purpose of this software is on the determination of 2D crack paths and surfaces as well as on the evaluation of components Lifetimes as a part of the damage tolerant assessment. Throughout the simulation of fatigue crack propagation an automatic adaptive mesh is carried out in the vicinity of the crack front nodes and in the elements which represent the higher stresses distribution. The fatigue crack direction and the corresponding stress-intensity factors are estimated at each small crack increment by employing the displacement extrapolation technique under facilitation of singular crack tip elements. The propagation is modeled by successive linear extensions, which are determined by the stress intensity factors under linear elastic fracture mechanics (LEFM) assumption. The stress intensity factors range history must be recorded along the small crack increments. Upon completion of the stress intensity factors range history recording, fatigue crack propagation life of the examined specimen is predicted. A consistent transfer algorithm and a crack relaxation method are proposed and implemented for this purpose. Verification of the predicted fatigue life is validated with relevant experimental data and numerical results obtained by other researchers. The comparisons show that the program is capable of demonstrating the fatigue life prediction results as well as the fatigue crack path satisfactorily.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.716-728
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• 1994

In this paper, fatigue tests were carried out to study the behavior of growth and coalescence of multi-surface cracks which were initiated at the semi-circular surface notches, and a simulation program was developed to predict their growth and coalescence behavior. By comparing the experimental result with those of the simulation based on SPC(surface point connection), ASME and BSI(British Standards Institution) conditions, we tried to enhance the reliance and integrity of structures. This shows that the simulation result has utility for fatigue life prediction.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.441-449
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• 2016

Agricultural tractors are designed using the empirical method due to the difficulty of measuring precise load cycles under various working conditions and soil types. Especially, directly drives various tractor implements, the power take off (PTO) gear. Therefore, alternative design methods using gear design software are needed for the optimal design of tractors. The objective of this study is to simulate fatigue life of the PTO gear according to the operating point of the tractor engine. The PTO gear was made with SCr415 alloy steel with carburizing and quenching treatments. The fatigue life of the PTO gear was simulated by using bending and contact stress according to the torque of the load levels. The PTO gear simulation was conducted by the KISSsoft commercial software for gear analysis. Bending and contact stress were calculated by the ISO 6336:2006 Method A and B. The simulation of fatigue life was calculated by the Miner's cumulative damage law. The total fatigue life of tractors can be estimated to 3,420 hours; thus, 3,420 hours of fatigue life were used in the simulation of the PTO gear of tractors. The main simulation results showed that the maximum fatigue life of the PTO gear was infinite fatigue life at maximum engine power. Minimum fatigue life of the PTO gear was 19.61 hours at 70% of the maximum engine power. Fatigue life of the PTO gear changed according to load of tractor. Therefore, tractor work data is needed for optimal design of the PTO gear.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.61-75
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• 1997

The social demand urges us to use some equipments and structures in high temperature environment. By this occasion, the necessity of studying the fatigue crack growth is an important aspect of new materials. However, the present situation is rarely to accumulate the fatigue data. Especially, 1Cr-1Mo-0.25V steel and 304 stainless steel have been increased to be used under the severe condition of high temperature. And so, the fatigue estimation of those materials is important and appropriate. Fatigue tests have been carried out to examine the crack initiation, growth behaviour for the small fatigue crack of 1Cr-1Mo-0.25V steel and 304 stainless steel at room temperature and 538^{\circ}C$. The remote measurement system which has many merits of checking and saving the image for detailed examination was applied to closely detect the crack length. Generally, the fatigue crack initiated in the form of multiple cracks and grew each other. And then it coalesced to become a major crack. The major crack governed the rest of the fatigue life. In the growing process, each peripheral cracks interact and grow for a certain period. After then, it coalesced and fractured. On the basis of the above experimental data for the small crack, a simulation program was developed to predict the residual life time and to estimate the integrity of machine elements and structures. At the same time, the simulation was extended to 1Cr-1Mo-0.25V steel. The simulation results have shown a good agreement to those of the experimental ones for both materials of 1Cr-1Mo-0.25V steel and 304 stainless steel with small cracks. The NASCRAC has applied to compare the fatigue life with the experimental results. And so, it can be said that the simulation program is valuable tools to the industrial fields.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.690-693
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• 2005

In this paper, probabilistic distribution of fatigue life of chassis component is determined statistically by applying the design of experiments and the Pearson system. To construct $p-\varepsilon-N$ curve, the case that fatigue data are random variables is attempted. Probabilistic density function(p.d.f) for fatigue life is obtained by design of experiment and using this p.d.f fatigue reliability about any aimed fatigue life can be calculated. Lower control arm and rear torsion bar of chassis component are selected as examples for analysis. Component load histories, which are obtained by multi-body dynamic simulation for Belsian load history, are used. Finite element analysis are performed using commercial software MSC Nastran and fatigue analysis are performed using FE Fatigue. When strain-life curve itself is random variable, probability density function of fatigue life has very little difference from log-normal distribution. And the case of fatigue data are random variables, probability density functions are approximated to Beta distribution. Each p.d.f is verified by Monte-Carlo simulation.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.2 s.191
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• pp.110-117
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• 2007

In this paper, probabilistic distribution of chassis component fatigue life is determined statistically by applying the design of experiments and the Pearson system. To construct p - ${\varepsilon}$ - N curve, the case that fatigue data are random variables is attempted. Probabilistic density function (p.d.f) for fatigue life is obtained by the design of experiment and using this p.d.f fatigue reliability, any aimed fatigue life can be calculated. Lower control arm and rear torsion bar of chassis components are selected as examples for analysis. Component load histories which are obtained by multi-body dynamic simulation for Belsian load history are used. Finite element analysis is performed by using commercial software MSC Nastran and fatigue analysis is performed by using FE Fatigue. When strain-life curve itself is random variable, the probability density function of fatigue life has very little difference from log-normal distribution. And the cases of fatigue data are random variables, probability density functions are approximated to Beta distribution. Each p.d.f is verified by Monte-Carlo simulation.

• Journal of Ocean Engineering and Technology
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• v.9 no.1
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• pp.142-151
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• 1995

A simulation program concerned with multi-surface fatigue cracks which initiated at the semi-circular surface notches has been developed to predict their growth and coalescence behaviors at the elevated temperature. Three kinds of coalescence models such as SPC(surface point connection), ASME and BSI(British Standards Institution) conditions were applied, and the results of the simulation were compared with those of the experiment. This simulation is able to enhance the reliance and integrity of structures especially under the elevated temperature which have lots of difficulties in experiments and applications. This shows that the simulation result has utility for fatigue life prediction. Even though all the specimens were the same shape, the error rate was increased in accordance with the applied stress to the specimen. Among the material constants C and m in the narrow band, the results applied upper values of the band to the simulation has shown quite small error compared with the experiment results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.1
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• pp.63-69
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• 2008

A fatigue test on the steel welded L-shaped frame was conducted. The frame was consisted with carbon steel tube and reinforced bracket. The four type reinforced brackets were fabricated. They were two rectangular plate reinforced bracket, two sided pentagon plate reinforced bracket, triangular plate reinforced bracket and fully reinforced bracket. The fatigue test of frame was conducted with axial tension loading. The fatigue simulation of the steel welded L-shaped frame was also performed by the finite element method with code FEMFAT. The frame of fully reinforced bracket had the highest fatigue life and reinforced quality factor.