• Title/Summary/Keyword: Fatigue crack initiation life

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A Study on the Prediection of Fatigue Life in the Axi-symmetric Extrusion Die (축대칭 압출금형의 피로수명예측에 관한 연구)

  • 안수홍;김태형;김병민;최재찬;조해용
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1994.10a
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    • pp.235-239
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    • 1994
  • In this paper, the fatigue behaviour of typical axisymmetric forward extrusion die is investigated and extrusion process is analyzed by the rigid-plastic finite element method and elasto-plastic finite element method. To approach the crack problem involving crack initiation and propagation in extrusion die, LEFM(Linear Elastic Fracture Mechanics) is introduced and singular element which models stress.strain singularity in the crack tip vincity has been used to obtain an accurate stress intensityu factor values and other results. Form the displacement around the crack tip the stress intensity factor and the effective stress intensity factor at the beginning of the die inlet radius has been calculated. Applying proper fatigue crack propagation criterion such as Paris/Erdogan fatigue law to this data the angle and direction of fatigue crack growth has been simulated and these are compared with some experimental results. Using the computed crack growth rate, fatigue life of the extrusion die has been evaluated.

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Fatigue Life Prediction of Tire Belt Edge (타이어 벨트 끝단의 피로수명 예측)

  • 김재연;양영수;김기운
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.954-957
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    • 2004
  • Tire belt durability is characterized by the initiation of a crack at the belt edge region, and the propagation of the crack until the ply is separated. Experimental methods have been used to analysis of the belt durability in the cord-reinforced rubber composite tires, but it takes much cost and time to make experiments. In this paper, a finite element method to analyze the fatigue life of a crack at the belt edge of tires is presented. The fatigue life is analyzed by using a three-dimensional Finite Element Modeling. This method includes a global-local finite element analysis to provide the detail necessary to model explicitly an internal crack and use of the J-integral for energy release rate evaluation.

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Evalustion and Prediction for the Fatigue crack Initiation and Growth Life by Reliability Approach (I) -Statistical Consideration for Fatigue Crack Growth Life- (신뢰성 공학적 피로 균열의 발생, 진전 수명 평가 및 예측에 관한 연구 ( I ) -피로 균열 진전 수명의 통계학적 분포 특성-)

  • 권재도;최선호;황재석;곽상국;전경옥;장재영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.6
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    • pp.1583-1591
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    • 1990
  • Life prediction and residual life prediction of structures of machines are one of the most strongly world wide needed problems as requirement in the stage of slowly developing economy which comes after rapidly and highly developing stage. For the purpose of statistical life prediction, fatigue test was conducted under the 4 stress levels, and for each stress level, about 20 specimens are used. The statistical properties of crack growth parameter m and C in the fatigue crack growth law of da/dN=C(.DELTA.K)sup m/, and the relationship between m and C, and the statistical distribution pattern of fatigue crack growth rate can be obtained by experimental results.

Statistical Life Prediction of Fatigue Crack Growth for SiC Whisker Reinforced Aluminium Composite (SiC 휘스커 보강 Al6061 복합재료의 통계학적 피로균열진전 수명예측)

  • 권재도;안정주;김상태
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.2
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    • pp.475-485
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    • 1995
  • In this study, statistical analysis of fatigue data which had obtained from respective 24 fatigue crack, was examined for SiC whisker reinforced aluminium 6061 composite alloy (SiC$_{w}$/A16061) and aluminium 6061 alloy. SiC volume fraction in composite alloy is 25%. The analysis results stress intensity factor range and 0.1 mm fatigue crack initiation life for SiC$_{w}$/A16061 composite & A16061 matrix are the log-normal distribution. And regression analysis by linear model, exponential model and multiplicative model were performed to find out the relationship between fatigue crack growth rate(da/dN) and stress intensity for find out the relationship between fatigue crack growth rate(da/dN) and stress intensity factor range(.DELTA.K) in the SiC$_{w}$/A16061 composite and examine the applicability of Paris' equation to SiC$_{w}$A16061 composite. Also computer simulation was performed for fatigue life prediction of SiC$_{w}$/A16061 composite using the statistical results of this study.udy.

Influence of laser peening on fatigue crack initiation of notched aluminum plates

  • Granados-Alejo, Vignaud;Rubio-Gonzalez, Carlos;Parra-Torres, Yazmin;Banderas, J. Antonio;Gomez-Rosas, Gilberto
    • Structural Engineering and Mechanics
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    • v.62 no.6
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    • pp.739-748
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    • 2017
  • Notches such as slots are typical geometric features on mechanical components that promote fatigue crack initiation. Unlike for components with open hole type notches, there are no conventional treatments to enhance fatigue behavior of components with slots. In this work we evaluate the viability of applying laser shock peening (LSP) to extend the fatigue life of 6061-T6 aluminum components with slots. The feasibility of using LSP is evaluated not only on damage free notched specimens, but also on samples with previous fatigue damage. For the LSP treatment a convergent lens was used to deliver 0.85 J and 6 ns laser pulses 1.5 mm in diameter by a Q-switch Nd: YAG laser, operating at 10 Hz with 1064 nm of wavelength. Residual stress distribution was assessed by the hole drilling method. A fatigue analysis of the notched specimens was conducted using the commercial code FE-Safe and different multiaxial fatigue criteria to predict fatigue lives of samples with and without LSP. The residual stress field produced by the LSP process was estimated by a finite element simulation of the process. A good comparison of the predicted and experimental fatigue lives was observed. The beneficial effect of LSP in extending fatigue life of notched components with and without previous damage is demonstrated.

A Study on the Fatigue Life Assessment for Load-carrying Fillet Welded Joints using Stress Intensity Factor (응력확대계수를 이용한 하중 전달형 필릿 용접부의 피로강도 평가에 관한 연구)

  • Kim, Myung-Hyun;Kang, Sung-Won;Kim, Hyoung-Rae
    • Journal of Welding and Joining
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    • v.26 no.6
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    • pp.97-102
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    • 2008
  • It is well known that there exist two typical fatigue crack initiation locations in ship structures: one is the weld toe and the other is the weld root where partial penetration weld is performed. In particular, it is important for fillet weldments to avoid weld root cracking in order to prevent catastrophic failure particularly in ship structures. Therefore detail considerations are required for cruciform joints with partial penetration when there is a possibility of weld root crack initiation. For these reasons, fatigue tests on welded joints were performed in this study. Concept of stress intensity factor(SIF) by means of fracture mechanics is applied for predicting fatigue life of fillet welded joints.

Statistical Analysis of Fatigue Crack Growth Properties for Silicon Carbide Particles Reinforced Metal Matrix Composites ($SiCp/A\ell$ 6061 복합재료의 피로균열진전특성에 관한 통계학적 해석)

  • 권재도;문윤배;안정주
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.4
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    • pp.130-139
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    • 1996
  • The silicon carbide particles reinforced aluminium 6061($SiCp/A\ell$) composites are generally known have wild range of applications from automobiles to airospaces. But, by the results of existing study for $SiCp/A\ell$ composites, there are reports that the fatigue life of $SiCp/A\ell$ composites has improved than $A\ell$matrixes and has not improved then $A\ell$ matrixes. Consequently, in order to perform the reliable life prediction for $SiCp/A\ell$, the properties of probability distribution of fatigue crack initiation life & fracture life, crack growth length in constant number of cycles, crack growth rate in constant stress intensity factor range and m & C value in Paris's fatigue crack growth law and the estimation of statistical parameters have been evaluated by the statistics method.

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A Study on the Crack Initiation Life for Crankshaft of Mid-size Engine (중형엔진 크랭크축의 균열발생수명에 대한 고찰)

  • Juh-H. Ham;Myung-H. Hyun;Su-H. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.32 no.3
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    • pp.126-134
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    • 1995
  • The crack initiation life evaluation which is the most commonly used approach in fatigue strength studies for the designers, is performed for the crankshaft of mid-size engine. In order to evaluate the fatigue strength, structural analysis model and applied loads on crankshaft are prepared based on the cyclic system. Using the response data of the finite element analysis, crack initiation life is predicted and plotted on crankshaft geometric model. In this analysis, general purpose programs such as PATRAN, NASTRAN and EMRC/NISA are actively utilized. Life distribution contour plots, which is not yet established as an active tool in actual design system of ship structure & components, are suggested and examples for active predicting procedure such as stress contour plotting in structure strength analysis, are illustrated. Additionally, several correlated equations for prediction of the crack initiation life are introduced and discussed to improve the fatigue strength prediction of crankshaft.

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A Fracture Mechanics Analysis on Fatigue Life Estimation of DEN Plate (DEN판재의 피로수명 평가에 관한 파괴역학적 연구)

  • Lim Chang-Hyeon
    • Journal of the Korean Society of Safety
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    • v.15 no.4
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    • pp.163-169
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    • 2000
  • This paper mainly deals with fatigue lift estimation and prediction in notched structures. The fatigue crack initiation life and the fatigue crack growth behavior in the DEN specimens were predicted using S.I.F. K solution derived in this study and the Paris' crack growth equation. Predicted results showed good agreement with experimental crack growth behaviors under constant-load-amplitude.

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Behavior of Fatigue Crack Initiation and Growth in SM45C Steel under Biaxial Loading (이축하중을 받는 SM45C강의 피로균열의 발생과 성장거동)

  • KIM SANG-TAE;PARK SUN-HONG;KWUN SOOK-IN
    • Journal of Ocean Engineering and Technology
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    • v.18 no.6 s.61
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    • pp.84-90
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    • 2004
  • Fatigue tests were conducted on SM45C steel using hour-glass shaped smooth tubular specimen under biaxial loading in order to investigate the crack formation and growth at room temperature. Three types of loading systems, were employed fully-reserved cyclic torsion without a superimposed static tension or compression fully-reserved cyclic torsion with a superimposed static tension and fully-reserved cyclic torsion with a superimposed static compression. The test results showed that a superimposed static tensile mean stress reduced fatigue life however a superimposed static compressive mean stress increased fatigue life. Experimental results indicated that cracks were initiated on planes of maximum shear strain whether or not the mean stresses were superimposed. A biaxial mean stress had an effect on the direction that the cracks nucleated and propagated at stage 1 (mode II).