• Title, Summary, Keyword: Fatigue analysis Model

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A Study on Fatigue Durability through the Structural Analysis of Strut Bar (스트럿 바의 구조 해석을 통한 피로 내구성에 관한 연구)

  • Han, Moonsik;Cho, Jaeung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.24 no.5
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    • pp.504-511
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    • 2016
  • This study investigates the durability of strut bar at car through structural and fatigue analyses. In this study, there are model 1 and model 2 as the analysis subjects. Model 1 is the existed one and model 2 is the improved one added with the reinforced part. Model 1 has the maximum equivalent stress of 165.11 MPa shown intensively at the welding part between the bracket and the bar. This stress is distributed over at the part of model 2 reinforced with this part. In case of fatigue analysis, there are three kinds of fatigue load as SAE bracket history, SAE transmission and sample history. The maximum fatigue life at SAE bracket history among three kinds of fatigue loads has the least value of $3.3693{\times}10^5$ cycles. The maximum fatigue life of model 2 becomes longer than that of model 1. As model 2 has the fatigue damage less than model 1, model 2 has the safety than model 1. As the fatigue durability about the configuration of strut bar is analyzed, it is thought to apply this study result into the real part effectively.

Durability Analysis on Fatigue of Caliper Cylinder (캘리퍼 실린더의 피로에 대한 내구성 해석)

  • Han, Moonsik;Cho, Jaeung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.23 no.2
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    • pp.208-213
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    • 2015
  • In this study, two models due to the configuration of caliper cylinder among the parts of automotive brake system are studied by structural and fatigue analysis. As the maximum equivalent stress at model 2 becomes 1.5 times lower than model 1, model 2 can endure load higher than model 1. In case of fatigue damage analysis on model 1 and 2, model 1 has the damage area more than model 2. Fatigue damage at model 1 happen more than model 2. These study results can be effectively utilized with the design on caliper cylinder by anticipating prevention against its damage and investigating durability.

Numerical Analysis Model for Fatigue Life Prediction of Welded Structures (용접구조물의 피로수명예측을 위한 수치해석모델)

  • Lee, Chi-Seung;Lee, Jae-Myung
    • Journal of Welding and Joining
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    • v.27 no.6
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    • pp.49-54
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    • 2009
  • In this study, the numerical analysis model for fatigue life prediction of welded structures are presented. In order to evaluate the structural degradation of welded structures due to fatigue loading, continuum damage mechanics approach is applied. Damage evolution equation of welded structures under arbitrary fatigue loading is constructed as a unified plasticity-damage theory. Moreover, by integration of damage evolution equation regarding to stress amplitude and number of cycles, the simplified fatigue life prediction model is derived. The proposed model is compared with fatigue test results of T-joint welded structures to obtain its validation and usefulness. It is confirmed that the predicted fatigue life of T-joint welded structures are coincided well with the fatigue test results.

A Study on Optimal Spot-weld Layout Design of the Shock Tower Structure Considering Fatigue Life under Random Vibration Load (불규칙 진동하중을 받는 쇽 타워의 피로수명을 고려한 점용접 위치 최적설계)

  • Lee, Yong-Hoon;Lee, Seung-Yoon;Bae, Bok-Soo;Yim, Hong-Jae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.538-543
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    • 2011
  • In this paper, optimal spot weld layout design of the shock tower structure is performed for increasing fatigue life of spot weld and fatigue life of shock tower simultaneously. To predict the fatigue life, linear static analysis is conducted then fatigue analysis is performed by applying random vibration load. To optimize the spot weld layout, design variables that have an effect on spot weld fatigue life are selected. Based on the DOE table, spot weld fatigue analysis is conducted. Finally, response surface model is made from fatigue analysis results and optimized spot weld layout model which increases fatigue life of sport weld and fatigue life of shock tower is determined.

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A Structural Model for Symptom Management of the Patients with Chronic Fatigue (만성피로 환자의 증상관리 구조모형 구축)

  • 한금선
    • Journal of Korean Academy of Nursing
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    • v.34 no.2
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    • pp.333-343
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    • 2004
  • Purpose: This study was designed to construct a structural model for symptom management of life of the patients with chronic fatigue. The hypothetical model was developed based on the literature review and Self-regulating Model. Method: Data were collected by questionnaires from 252 patients with chronic fatigue in the 8 community from December 2002 to April 2003 in Seoul. Data analysis was done with SAS for descriptive statistics and PC-LISREL Program for Covariance structural analysis. Result: The fit of the hypothetical model to the data was moderate, thus it was modified by excluding 4 path and including free parameters and 3 path to it The modified model with path showed a good fitness to the empirical data($x^2$=318.11, p=0.0, GFI=.98, AGFI=.98, NNFI=.95, RMSR=.03, RMSEA=.05). The symptoms of stress, self-efficacy, and present fatigue level were found to have significant direct effect on symptom management of the patients with chronic fatigue. The ways of coping, perceived stress, and fatigue symptom were found to have indirect effects on symptom management of the patients with chronic fatigue. Conclusion: The derived model is considered appropriate in explaining and predicting symptom management of the patients with chronic fatigue. Therefore, it can effectively be used as a reference model for further studies and suggested direction in nursing practice.

A Study on Durability of Under Bar at Car through Structural and Fatigue Analysis (자동차 언더바의 구조 및 피로해석을 통한 내구성 연구)

  • Han, Mu Shick;JO, Jae-Woong
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.2
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    • pp.44-50
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    • 2015
  • This study investigated the durability of the under bar of a car through structural and fatigue analysis. Model 1 had the lowest value among three kinds of models. In the case of the maximum equivalent stress and displacement at structural analysis, model 1 showed the highest durability. Also, models 3 and 2 showed structural durability in order of this value. In the case of fatigue analysis, the maximum fatigue lives of the three models were equal to $2{\times}10^7$cycles. However, model 1 showed the highest value among the three models, as the minimum fatigue life of model 1 becames 92.56 cycles. Also models 3 and 2 showed fatigue durability in order of this value. The maximum possibility of fatigue damage for models1,2,and 3 became 30%. If the results of this study are applied to change the design shape of the under bar of cars, the ride comfort for automobile passengers and car durability can be improved.

Fatigue Assessment Model of Corroded RC Beams Strengthened with Prestressed CFRP Sheets

  • Song, Li;Hou, Jian
    • International Journal of Concrete Structures and Materials
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    • v.11 no.2
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    • pp.247-259
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    • 2017
  • This paper presents a fatigue assessment model that was developed for corroded reinforced concrete (RC) beams strengthened using prestressed carbon fiber-reinforced polymer (CFRP) sheets. The proposed model considers the fatigue properties of the constituent materials as well as the section equilibrium. The model provides a rational approach that can be used to explicitly assess the failure mode, fatigue life, fatigue strength, stiffness, and post-fatigue ultimate capacity of corroded beams strengthened with prestressed CFRP. A parametric analysis demonstrated that the controlling factor for the fatigue behavior of the beams is the fatigue behavior of the corroded steel bars. Strengthening with one layer of non-prestressed CFRP sheets restored the fatigue behavior of beams with rebar at a low corrosion degree to the level of the uncorroded beams, while strengthening with 20- and 30%-prestressed CFRP sheets restored the fatigue behavior of the beams with medium and high corrosion degrees, respectively, to the values of the uncorroded beams. Under cyclic fatigue loading, the factors for the strengthening design of corroded RC beams fall in the order of stiffness, fatigue life, fatigue strength, and ultimate capacity.

Durability Study through Structural and Fatigue Analyses of Brake Pads with Different Configurations (형상이 다른 브레이크 패드의 구조 및 피로해석을 통한 내구성 연구)

  • Han, Moonsik;Cho, Jaeung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.22 no.6
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    • pp.128-133
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    • 2014
  • In this study, Two kinds of pad models with different configurations as the part of brake system are investigated by structural and fatigue analyses. As the maximum equivalent stress of model 2 becomes higher to the extent of 60% than that of model 1, model 2 can endure more load than model 1. In cases of two kinds of models, the maximum fatigue life at 'Sample history' becomes longer 60 times than 'SAE bracket history' and this life in case of 'SAE transmission' becomes longer 3.5 times than the case of 'SAE bracket history'. Maximum fatigue damages in cases of 'SAE bracket history', 'SAE transmission' and 'Sample history' at model 1 become higher than model 2. Model 2 is thought to have more fatigue durability than model 1. These study results can be effectively utilized with the design of brake pad by anticipating and investigating prevention and durability against its fatigue damage.

A Model for Fatigue Life In CFRP Laminates with Impact Damage (충격손상을 가진 CFRP 적층복합재료의 피로수명예측모델)

  • Gang, Gi-Won;Kim, Jeong-Gyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.11
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    • pp.2828-2835
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    • 2000
  • This paper presents the fatigue behavior of composite materials with impact-induced damage. The impact damage parameter is proposed to evaluate the effect of impact damage on fatigue life. Subsequently, a new model is developed to predict the fatigue life of impacted composite materials. Also, a stochastic model is proposed to describe the variation of fatigue life due to the material nonhomogeneity. For these models, the fatigue tests were performed on the unimpacted and impacted composite materials, The effect of impact damage on fatigue life can be characterized by the impact damage parameter. Additionally, the results by the present fatigue life prediction model agree will with experimental results regardless of applied impact energy. Also, the variation of fatigue life can be described by the present stochastic model and is reduced with applied impact energy.

Stochastic modelling fatigue crack evolution and optimum maintenance strategy for composite blades of wind turbines

  • Chen, Hua-Peng;Zhang, Chi;Huang, Tian-Li
    • Structural Engineering and Mechanics
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    • v.63 no.6
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    • pp.703-712
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    • 2017
  • The composite blades of offshore wind turbines accumulate structural damage such as fatigue cracking due to harsh operation environments during their service time, leading to premature structural failures. This paper investigates various fatigue crack models for reproducing crack development in composite blades and proposes a stochastic approach to predict fatigue crack evolution and to analyse failure probability for the composite blades. Three typical fatigue models for the propagation of fatigue cracks, i.e., Miner model, Paris model and Reifsnider model, are discussed to reproduce the fatigue crack evolution in composite blades subjected to cyclical loadings. The lifetime probability of fatigue failure of the composite blades is estimated by stochastic deterioration modelling such as gamma process. Based on time-dependent reliability analysis and lifecycle cost analysis, an optimised maintenance policy is determined to make the optimal decision for the composite blades during the service time. A numerical example is employed to investigate the effectiveness of predicting fatigue crack growth, estimating the probability of fatigue failure and evaluating an optimal maintenance policy. The results from the numerical study show that the stochastic gamma process together with the proper fatigue models can provide a useful tool for remaining useful life predictions and optimum maintenance strategies of the composite blades of offshore wind turbines.