• Journal of Ship and Ocean Technology
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• v.9 no.4
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• pp.11-22
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• 2005

This paper addresses details of wave load nonlinearity effect on stress RAO and damage ratio using component stochastic fatigue analysis. Traditional spectral fatigue analysis for ship structure is based on linear theory; however, there are a number of nonlinearity sources. Especially loading nonlinearity, such as hydrodynamic pressure applying to ship side and gravity changes due to roll and pitch motion, is thought to critically violate the linearity assumption of spectral fatigue analysis, which involves stress RAO as linear parameter. The main focus is placed on how to idealize complicated characteristics of loading nonlinearity and how to implement the nonlinear bias to linear spectral fatigue analysis.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.796-804
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• 2003

The use of fracture mechanics has traditionally concentrated on crack growth under an opening mechanism. However, many service failures occur from cracks subjected to mixed-mode loading. Hence, it is necessary to evaluate the fatigue behavior under mixed-mode loading. Under mixed-mode loading, not only the fatigue crack propagation rate is of importance, but also the crack propagation direction. In modified range 0.3$\leq$a/W$\leq$0.5, the stress intensity factors (SIFs) of mode I and mode II for the compact tension shear (CTS) specimen were calculated by using elastic finite element analysis. The propagation behavior of the fatigue cracks of cold rolled stainless steels (STS304) under mixed-mode conditions was evaluated by using K$\_$I/ and $_{4}$ (SIFs of mode I and mode II). The maximum tangential stress (MTS) criterion and stress intensity factor were applied to predict the crack propagation direction and the propagation behavior of fatigue cracks.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.573-579
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• 2010

The notch effects on the fatigue strength of welded joints are both stress concentration and fatigue strength reduction. In the notch stress approach, the notch effects are usually approximated by introducing weld-bead parameters for the local detailed weld joints. In this paper, well-known notch stress approaches - critical distance method, area method and fictitious rounding method are presented for the fatigue strength of cruciform joints. The estimated results of the present methods are applied to the experiments performed in this study and reported in the references. The results of the application show that the fatigue-life scatterness of the experimental data expressed in the nominal stress is significantly reduced by introducing the effective fatigue stress of the present study.

• Steel and Composite Structures
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• v.38 no.3
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• pp.271-280
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• 2021

In this study, the fatigue property of U rib-to-crossbeam connections in orthotropic steel bridge (OSB) crossbeams under heavy traffic vehicle load was investigated considering the effects of in-plane shear stress. The applicability of an improved structural stress (ISS) method was validated for the fatigue behavior analysis of nonwelded arc-shaped cutout regions in multiaxial stress states. Various types of fatigue testing specimens were compared for investigating the equivalent structural stress, fatigue crack initiation positions, and failure modes with the unified standards. Furthermore, the implications of OSB crossbeams and specified loading cases are discussed with respect to the improved method. The ISS method is proven to be applicable for analyzing the fatigue property of nonwelded arc-shaped cutout regions in OSB crossbeams. The used method is essential for gaining a reliable prediction of the most likely failure modes under a specific heavy traffic vehicle load. The evaluated results using the used method are proven to be accurate with a slighter standard deviation. We obtained the trend of equivalent structural stress in arc-shaped cutout regions and validated the crack initiation positions and propagation directions by comparing them with the fatigue testing results. The implications of crossbeam spans on fatigue property are less significant than the effects of crossbeams.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.8-13
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• 2013

This study analyzes about poclain bucket through fatigue durability analysis. Maximum equivalent stress and total deformation are shown at the lower of bucket and edge part respectively. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of -10000Pa to 5000MPa and the amplitude stress of 0 to 6000MPa, the possibility of maximum damage becomes 3%. This stress state can be shown with 5 or 6 times more than the damage possibility of 'SAE bracket history' or 'SAE transmission'. The structural result of this study can be effectively utilized with the design of poclain bucket by investigating prevention and durability against fatigue damage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.5
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• pp.724-733
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• 2003

Fatigue design rules for welds in the ASME Boiler and Pressure Vessels Code are based on the use of Fatigue Strength Reduction Factors(FSRF) against a code specified fatigue design curve generated from smooth base metal specimens without the presence of welds. Similarly, stress intensification factors that are used in the ASME B3l.1 Piping Code are based on component S-N curves with a reference fatigue strength based on straight pipe girth welds. But the determination of either the FSRF or stress intensification factor requires extensive fatigue testing to take into account the stress concentration effects associated with various types of component geometry, weld configuration and loading conditions. As the fatigue behavior of welded joints is being better understood, it has been generally accepted that the difference in fatigue lives from one type of weld to another is dominated by the difference in stress concentration. However, general finite element procedures are currently not available for effective determination of such stress concentration effects. In this paper, a mesh-insensitive structural stress method is used to re-evaluate the S-N test data, and then more effective method is proposed for pressure vessel and piping fatigue design.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.3
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• pp.87-92
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• 2011

This study analyzes structural stress and fatigue on control arm of automobile under nonuniform load. Maximum equivalent stress at bolt part is shown with 419.1MPa and the corner is deformed with maximum displacement of 1.1628mm. Among 3 cases of nonuniform fatigue loads applying on control arm, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of $-10^5MPa$ to $10^5MPa$ and the amplitude stress of 0 MPa to $10^5MPa$, the possibility of maximum damage becomes 3%. This stress state can be shown with 6 times more than the damage possibility of 'SAE bracket history' or 'SAE transmission'. Safety and durability on automobile can be effectively improved by applying the fatigue analysis result on control arm.

• Journal of Aerospace System Engineering
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• v.3 no.2
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• pp.12-19
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• 2009

The research for the fatigue analysis is regarded greatly as important in aerospace field. Moreover, a study on the fatigue characteristic is very actively progressing. In this study, the fatigue life estimation was performed for Flaperon Joint which has FCL(fatigue critical location) of tilt-rotor UAV. The Flaperon Joint should be taken the various loads by several missions profiles of UAV. The fatigue load spectrum of Flaperon Joint is generated by the standard mission segment for the tilt-rotor UAV, and this spectrum is used for the fatigue test and analysis. The in-house fatigue analysis program is applied to calculate the fatigue life based on Stress-Life(S-N) method. The S-N curve is generated from the S-N data of Mil-Handbook by second order polynomial regression method. Moreover, the coefficient of determination is used to ensure how accuracy it has. In addition, the Goodman equation is used to consider the mean stress effect for evaluating more accurate fatigue life. Finally, the result of fatigue analysis is verified by comparing with the fatigue test result for the Flaperon Joint.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.120-126
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• 1998

Second step shot peening was applied on both smooth specimen and U-notch specimen in order to investigate the stress distribution and the improvement in fatigue strength. Various experiments and measurements such as rotary bending fatigue test and the measurement of compressive residual stress were performed. The results showed that the fatigue strength of second step shot peened specimens increased by 34 percent compared to that of unpeened ones. Compressive residual stress also considerably increased, which resulted in the increase of fatigue strength. finite element analysis showed that shot peening is effective in decreasing the bending stress by external force. The effectiveness of shot peening in reducing the compressive residual stress was anticipated by the superposition of the concentrated stress and the compressive residual stress.

• Journal of International Academy of Physical Therapy Research
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• v.8 no.2
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• pp.1135-1141
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• 2017

Stress and fatigue are general physical aspects of our daily lives. It has been shown that physical therapists have different levels of job stress and fatigue according to the type A/B behavior patterns. This study collected data from 212 physical therapists between October 28 and November 23, 2016 using an anonymous, self-administered questionnaire. The study results showed the proportion of physical therapists with the Type A behavior patterns(TABP) was 18% greater than that of physical therapists with the Type B behavior patterns(TBBP). In this study, physical therapists with TABP were compared with physical therapists with TBBP. The results indicated that physical therapists with TABP were more inclined to experience higher levels of overall job stress and fatigue from the following stress factors: physical environment, job requirement, and job autonomy. Therefore, the stronger the tendency toward TABP, the stronger the feeling of job stress and fatigue from physical environment, job requirement, and job autonomy. Those with a tendency toward TBBP showed positive correlations between job requirement and the total job stress score; thus, the stronger the tendency toward TBBP, the stronger the feeling of overall job stress and fatigue from job requirement. This study suggests that it is necessary to manage the job stress and fatigue of physical therapists with both TABP and TBBP and to manage the job stress and fatigue of physical therapists with the type A behavioral pattern.