• Title, Summary, Keyword: Fatigue Test

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The Fatigue Behavior of Laser Weldment in Heterogeneous Materials (이종재료 레이저 용접부의 피로거동)

  • 권응관;오택열;곽대순;이종재
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.759-764
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    • 1997
  • In this study, Fatigue behavior of laser weldment in heterogeneous materials was investigated. Fatigue strength test and fatigue crack propagation test were performed for specimens with laser weldment in heterogeneous materials, and hardness test was performed. From the fatigue strength test. it was observed that the difference of strength between heterogeneous materials had eflect on crack initiation position and fatigue limit. From the fatigue crack propagation test. it was observed that fatigue behavior of laser weldment in heterogeneous materials is different from that in same materials. The difference of strength between heterogeneous materials and laser weldment had effect on fatigue crack propagation rate.

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Ultrasonic Fatigue Test for a High Strength Steel Plate (고장력 강판의 초음파 피로시험)

  • Yeom, Hyunho;Jung, Yongchan;Kim, Chayeong;Kang, Ki-Young;Lee, Moon Gu;Hong, Min-Sung;Jeon, Yongho
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.24 no.6
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    • pp.589-593
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    • 2015
  • The demand of high cycle fatigue behavior on plate material is increasing because of its various applications. However, the high-cycle fatigue life data of the plate material is very rare compared to the rod material. Thus, in this study, a plate specimen is designed for the ultrasonic fatigue test because it is time efficient as compared to the conventional fatigue test. To apply the ultrasonic fatigue test, the specimen design is required to resonate at 20 kHz. Therefore, the dynamic elastic modulus was determined by measuring the resonance frequency with a piezoelectric element and laser doppler vibrometer (LDV). As a result, the plate specimen is designed and demonstrated using the ultrasonic fatigue testing machine. The ultrasonic fatigue test results were compared with the hydraulic fatigue test results.

Safety Evaluation of Bogie Frame for Tilting Railway Vehicles by Fatigue and Nondestructive Tests (피로시험 및 비파괴 검사를 통한 틸팅열차용 주행장치 프레임의 안전성 평가)

  • Kim Jung-Seok;Kim Nam-Po
    • Journal of the Korean Society for Railway
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    • v.8 no.5
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    • pp.419-424
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    • 2005
  • This paper has performed fatigue and nondestructive test of bogie frame for Korean tilting train. Before the fatigue test, static tests were carried out. From the test, the structural safety was investigated using Goodman diagram. After the static test, the fatigue test were conducted under tilting load conditions. The fatigue test was conducted for $10{\times}10^6$ cycles. During the fatigue test, the nondestructive tests using magnetic particle and liquid penetrant were performed at $6{\times}10^6$ cycle and $10{\times}10^6$cycle. From the crack detection tests, it was known that there was no fatigue crack in the bogie frame.

A Study on Reliability Estimation for Fatigue Life of the Spider from a Drum Washing Machine (드럼 세탁기 Spider의 피로수명 신뢰성 평가에 대한 연구)

  • 이성민;조상봉;조성진;김영수;강동우;정연수;정보선
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.46-49
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    • 2004
  • The spider of a drum washing machine receives the repeated fatigue loadings during laundering. Although the spider is designed statically safely, it often happens fatigue failure. Therefore it requires the safe design for fatigue and needs the prediction of quantitative fatigue life. The S-N diagram for a spider material is developed by fatigue test and statistical analysis. The stresses are measured directly from strain gages on the spider. To predict the fatigue life of spider, the rainflow counting method and Miner's rule are used. The data for fatigue life are analyzed statistically. From these data, reliability estimation for fatigue life can be done and also, equivalent fatigue life can be obtained. It will be applied to make and improve to a short period for design and prototype test.

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A Study on the Fatigue Life Prediction and Evaluation of Rubber Components for Automobile Vehicle (자동차 방진고무부품의 피로수명 예측 및 평가)

  • Woo, Chang-Su;Kim, Wan-Doo;Kwon, Jae-Do
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.6
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    • pp.56-62
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    • 2005
  • The fatigue analysis and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. Fatigue lifetime prediction methodology of the rubber component was proposed by incorporating the finite element analysis and fatigue damage parameter from fatigue test. Finite element analysis of 3D dumbbell specimen and rubber component were performed based on a hyper-elastic material model determined from material test. The Green-Lagrange strain at the critical location determined from the FEM was used for evaluating the fatigue damaged parameter of the natural rubber. Fatigue life of the rubber component are predicted by using the fatigue damage parameter at the critical location. Predicted fatigue lifes of the rubber component agreed fairly well the experimental fatigue lives.

Deterioration in strength of studs based on two-parameter fatigue failure criterion

  • Wang, Bing;Huang, Qiao;Liu, Xiaoling
    • Steel and Composite Structures
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    • v.23 no.2
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    • pp.239-250
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    • 2017
  • In the concept of two-parameter fatigue failure criterion, the material fatigue failure is determined by the damage degree and the current stress level. Based on this viewpoint, a residual strength degradation model for stud shear connectors under fatigue loads is proposed in this study. First, existing residual strength degradation models and test data are summarized. Next, three series of 11 push-out specimen tests according to the standard push-out test method in Eurocode-4 are performed: the static strength test, the fatigue endurance test and the residual strength test. By introducing the "two-parameter fatigue failure criterion," a residual strength calculation model after cyclic loading is derived, considering the nonlinear fatigue damage and the current stress condition. The parameters are achieved by fitting the data from this study and some literature data. Finally, through verification using several literature reports, the results show that the model can better describe the strength degradation law of stud connectors.

Cyclic fatigue resistance tests of Nickel-Titanium rotary files using simulated canal and weight loading conditions

  • Cho, Ok-In;Versluis, Antheunis;Cheung, Gary S.P.;Ha, Jung-Hong;Hur, Bock;Kim, Hyeon-Cheol
    • Restorative Dentistry and Endodontics
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    • v.38 no.1
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    • pp.31-35
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    • 2013
  • Objectives: This study compared the cyclic fatigue resistance of nickel-titanium (NiTi) files obtained in a conventional test using a simulated canal with a newly developed method that allows the application of constant fatigue load conditions. Materials and Methods: ProFile and K3 files of #25/.06, #30/.06, and #40/.04 were selected. Two types of testing devices were built to test their fatigue performance. The first (conventional) device prescribed curvature inside a simulated canal (C-test), the second new device exerted a constant load (L-test) whilst allowing any resulting curvature. Ten new instruments of each size and brand were tested with each device. The files were rotated until fracture and the number of cycles to failure (NCF) was determined. The NCF were subjected to one-way ANOVA and Duncan's post-hoc test for each method. Spearman's rank correlation coefficient was computed to examine any association between methods. Results: Spearman's rank correlation coefficient (${\rho}$ = -0.905) showed a significant negative correlation between methods. Groups with significant difference after the L-test divided into 4 clusters, whilst the C-test gave just 2 clusters. From the L-test, considering the negative correlation of NCF, K3 gave a significantly lower fatigue resistance than ProFile as in the C-test. K3 #30/.06 showed a lower fatigue resistance than K3 #25/.06, which was not found by the C-test. Variation in fatigue test methodology resulted in different cyclic fatigue resistance rankings for various NiTi files. Conclusions: The new methodology standardized the load during fatigue testing, allowing determination fatigue behavior under constant load conditions.

Determination of the Threshold Stress Intensity Factor in Fatigue Crack Growth Test (피로균열성장시험에서 하한계 응력확대계수의 결정)

  • 허성필;석창성;양원호
    • Journal of the Korean Society of Safety
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    • v.15 no.3
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    • pp.1-6
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    • 2000
  • In fatigue crack growth test, it is important not only to analyze characteristics of fatigue crack growth but also to determine the threshold stress intensity factor, ${\Delta}K_{th}$. which is the threshold value of fatigue crack growth. Linear regression analysis using fatigue test data near the threshold is suggested to determine the ${\Delta}K_{th}$ in the standard test method but the ${\Delta}K_{th}$ can be affected by a fitting method. And there are some limitations on the linear regression analysis in the case of small number of test data near the threshold. The objective of this study is to investigate differences of the ${\Delta}K_{th}$ due to regression analysis method and to evaluate the relative error range of the ${\Delta}K_{th}$ in same fatigue crack growth test data.

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Strength Evaluation for Bolster of Korean Tilting Train by Static and Fatigue Tests (정적 및 피로시험에 의한 틸팅열차용 볼스터의 구조강도평가)

  • Kim Nam-Po;Kim Jung-Seok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.2
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    • pp.210-218
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    • 2006
  • This paper has performed static, fatigue and nondestructive test of tilting' bolster frame for Korean tilting train. From the static test, the structural safety was investigated using Goodman diagram. After the static test, the fatigue test were conducted under tilting load conditions. The fatigue test was conducted for $10\times10^6$ cycles. During the fatigue test, the nondestructive tests using magnetic particle and liquid penetrant were performed at $6\times10^6$cycle and $10\times10^6$cycle. From the crack detection tests, it was known that there was no fatigue crack in the tilting bolster.

Split Tension Fatigue Characteristics Analysis of Fatigue Tests Data for Concrete Pavements (콘크리트 포장 피로실험 데이터의 쪼갬인장 피로특성)

  • Kim, Dong-Ho;Kim, Sung-Hwan;Yun, Byung-Sung;Lee, Bong-Hak
    • Journal of Industrial Technology
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    • v.23 no.A
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    • pp.139-147
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    • 2003
  • The purpose of this study was to investigate and analyze the fatigue test data of pavement concrete. The static strength tests were carried out to check the compressive strength, flexural strength, and split tension strength at 56 days in order to minimize strength variation effect during test. The specimens were fabricated at twelves sections at a construction site of highway. The stress level and stress ratio of fatigue test were determined from static test results. The results are as follow: The flexural strength at 28 days mostly satisfied the criterion for design, but the compressive strength at 28 days were slightly below the criterion even though it satisfied at 56 days. The fatigue limit was 2 million cycles if the specimen was not failed to that cycles. The S-N curves were developed from the fatigue test results at each stress levels and each stress ratio. Then, the fatigue life of pavement concrete at a given stress level and fatigue strength of pavement concrete could be derived from these curves. Analysis using method No.2 was more acceptable because resulting of comparison and analysis using method No.2 was presented 2 sections were presented $R^2$ < 0.7, and other 2 sections were presented 0.7 < $R^2$ < 0.8, and the others 8 sections were $R^2{\geq}0.8$.

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