• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.339-349
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• 2004

The method for fatigue life prediction of ball bearing is proposed applying the algorithm of contact fatigue prediction based on stress analysis. In order to do this, a series of simulation such as initial surface stress analysis, EHL analysis, subsurface stress analysis and fatigue analysis are conducted from the loading at each ball location calculated for a bearing subjected to external bearing load and contact shape function. And uniaxial fatigue tests are performed to obtain fatigue parameter of AISI 52100 steel. It was found that since stress is usually higher at the inner raceway contact than at the outer raceway contact, fatigue failure occurs on the inner raceway first. When the fatigue life calculated in the stress-based method are compared with $L_{50}$ life of L-P model, Crossland criterion for the radial load increment is similar to $L_{50}$ life and Dang Van criterion for the axial load increment is similar. In the case of EHL contact. there is no difference of fatigue life between dry contact and EHL contact, when maximum Hertz pressure exceeds 2.5GPa.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.5
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• pp.44-55
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• 2007

The method for fatigue life prediction of ball bearing is proposed applying the algorithm of contact fatigue prediction based on stress analysis. In order to do this, a series of simulation such as initial surface stress analysis, EHL analysis, subsurface stress analysis and fatigue analysis are conducted from the loading at each ball location calculated for a bearing subjected to external bearing load and contact shape function. And uniaxial fatigue tests are performed to obtain fatigue parameter of AISI 52100 steel. It was found that since stress is usually higher at the inner raceway contact than at the outer raceway contact, fatigue failure occurs on the inner raceway first. When the fatigue life calculated in the stress-based method are compared with L50 life of L-P model, Crossland criterion for the radial load increment is similar to L50 life and Dang Van criterion for the axial load increment is similar. In the case of EHL contact, there is no difference of fatigue life between dry contact and EHL contact, when maximum Hertz pressure exceeds 2.5GPa.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1498-1506
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• 1997

Procedures are presented for influence of shot peening on fatigue strength, fatigue life and effects of shot peening are discussed from experiments were taken between shot peened and unpeened SPS5, SM45C specimens. After the residual stress on shot peened specimens was measured by X-ray diffractometer, rotating bending fatigue tests were carried out. In addition, the compressive residual stress profile was obtained by the superposition method of three stresses which is based on Al-Obaid's equation. Predicted fatigue life considering residual stress profile which was obtained by the Al-Obaid's equation and another predicted fatigue life considering residual stress profile which was measured in test were compared. For the purpose of predicting fatigue life, Morrow's equation considering the residual stress and mean stress was used.

• Tribology and Lubricants
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• v.36 no.6
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• pp.371-377
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• 2020

In In this study, we compared the results of a ball bearing life prediction model based on rolling element loads with the results of fatigue life prediction of ball bearings when a stress-based contact fatigue life prediction technique is applied to the ball bearing. We calculate the load acting on each rolling element by the external load of the bearing and apply the result to the Lundberg-Palmgren (LP) theory to calculate ball bearing life based on the rolling element. We also calculate stress-based ball bearing life through contact and fatigue analyses based on contact modeling of the ball and raceway while considering the fatigue test results of AISI 52100 steel. In stress-based life prediction, we use three high-cycle fatigue-determination equations that can predict the fatigue life when multi-axis proportional loads such as rolling-slide contact conditions are applied. These equations are derived from the stress invariant and critical plane methods and the mesoscopic approach. Life expectancy results are compared with those of the LP model. Results of the analysis indicated that the fatigue life was predicted to be lower in the order of the Crossland, Dang Van, and Matake models. Of the three, the Dang Van fatigue model was found to be the closest to the LP life.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.99-104
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• 2001

Effect of mean stress on the fatigue life of natural rubber for engine mount was investigated. Fatigue damage parameter based on the maximum Green-Lagrange strain was employed to account for the effect of mean stress. A procedure to predict the fatigue life of rubber components based on the maximum Green-Lagrange strain method was proposed. Nonlinear finite element analysis and fatigue test of jang-gu shape specimen were conducted to predict the fatigue life of engine mount. Predicted fatigue lives have a good agreement with tested lives within a factor of 3.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.268-271
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• 1999

Fatigue life Prediction is investigated analytically based on the fatigue modulus concept. Fatigue modulus degradation rate at any fatigue cycle was assumed as a power function of number of fatigue cycles. New stress function describing the relation of initial fatigue modulus and elastic modulus was used to account for material non-linearity at the first cycle. It was assumed that fatigue modulus at failure is proportional to applied stress level. A new fatigue life prediction equation as a function of applied stress is proposed. The prediction was verified experimentally using cross-ply carbon/epoxy laminate (CFRP) tube.

• Structural Engineering and Mechanics
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• v.35 no.5
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• pp.571-592
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• 2010

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial, bending and shear fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In the first part of this study, energy expressions that construct the constitutive law are equated in the form of total strain energy and the distortion energy dissipated in a fatigue cycle. The resulting equation is further evaluated to acquire the equivalent stress per cycle using energy based methodologies. The equivalent stress expressions are developed both for biaxial and multiaxial fatigue loads and are used to predict the number of cycles to failure based on previously developed prediction criterion. The equivalent stress expressions developed in this study are further used in a new finite element procedure to predict the fatigue life for two and three dimensional structures. In the second part of this study, a new Quadrilateral fatigue finite element is developed through integration of constitutive law into minimum potential energy formulation. This new QUAD-4 element is capable of simulating biaxial fatigue problems. The final output of this finite element analysis both using equivalent stress approach and using the new QUAD-4 fatigue element, is in the form of number of cycles to failure for each element on a scale in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure at each location in gas turbine engine structural components. In order to obtain experimental data for comparison, an Al6061-T6 plate is tested using a previously developed vibration based testing framework. The finite element analysis is performed for Al6061-T6 aluminum and the results are compared with experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.175-182
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• 2003

The fatigue life of welded joints is sensitive to welding residual stress and complexity of their geometric shapes. To predict the fatigue life more reasonably. the effects of welding residual stress and its relaxation on their fatigue strengths should be considered quantitatively, which are often regarded to be equivalent to the effects of mean stresses by external loads. The hot-spot stress concept should be also adopted which can reduce the dependence of fatigue strengths for various welding details. Considering the factors mentioned above, a fatigue life prediction model using the modified Goodman's diagram was proposed. In this model, an equivalent stress was introduced which is composed of the mean stress based on the hot-spot stress concept and the relaxed welding residual stress. From the verification of the proposed model to real welding details, it is proved that this model can be applied to predict reasonably their fatigue lives.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.977-985
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• 2004

An evaluation of fatigue life of welded components is complicated due to various geometrically complex welding details and stress raisers in vicinity of weld beads, ego under cuts, overlaps and blow holes. These factors have a considerable influence on the fatigue strength of welded joints, as well as the welding residual stress which is relaxed depending on the distribution of local stress at the front of the stress raisers. To reasonably evaluate fatigue life, the effect of geometries and welding residual stress should be taken into account. The several methods based on the notch strain approach have been proposed in order to accomplish this. These methods, however, result in differences between analytical and experimental results due to discrepancies in estimated amount of relaxed welding residual stress present. In this paper, an approach that involves the use of a modified notch strain approach considering geometrical effects and a residual stress relaxation model based on experimental results was proposed. The fatigue life for five types of representative welding details, ego cruciform, cover plate, longitudinal stiffener, gusset and side attachment joint, are evaluated using this method.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.453-461
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• 1999

The estimation of fatigue life at the design stage is very important in order to arrive at feasible and cost effective solutions considering the total lifetime of the structure and machinery compo-nents. In this study the practical procedure of prediction of fatigue life by use of cumulative damage factors based on Miner-Palmgren hypothesis and probability density function is shown with a $135,000m^3$ LNG tank being used as an example. In particular the parameters of Weibull distribution taht determine the stress spectrum are dis-cussed. At the end some of uncertainties associated with fatigue life prediction are discussed. The main results obtained from this study are as follows: 1. The practical procedure of prediction of fatigue life by use of cumulative damage factors expressed in combination of probability density function and S-N data is proposed. 2. The calculated fatigue life is influenced by the shape parameter and stress block. The conser-vative fatigue design can be achieved when using higher value of shape parameter and the stress blocks divded into more stress blocks.