• Title/Summary/Keyword: Modified Miner rule

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Evaluation of Rail Fatigue Life by Grinding of Kyeong-Bu High-Speed Line (경부고속선의 레일 연마에 따른 레일 피로수명 평가)

  • Kim, Man-Cheol;Choi, Eun-Soo
    • Journal of the Korean Society for Railway
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    • v.13 no.6
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    • pp.577-582
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    • 2010
  • The importance of maintenance of rail surface defects is increasing according to the KTX operation. That is because during high speed operation of rolling stocks, rail surface defects shorten fatigue life of rail, accelerate track degradation and deteriorate ride comfort. Rail grinding has been applied for effective rail maintenance in Kyeong-Bu HS line. This paper evaluates the effectiveness of rail grinding in term of rail fatigue life. To this end, the stresses of the rail are measured under KTX running and the equivalent stress range is calculated by RMC after the frequency analysis done with rainflow counting method. Also, The Modified Miner's rule is applied to predict the fatigue life of ground rail. The result of the analysis shows that the fatigue life of ground rail is increased by 15%.

Prediction of Bending Fatigue Life to Welding Parts of Rail on Slab Track (슬래브궤도상의 레일 용접부 피로수명 예측)

  • 김만철;김진성;한상철
    • Journal of the Korean Society for Railway
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    • v.4 no.4
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    • pp.138-146
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    • 2001
  • For the purpose of the effective maintenance of surface irregularities of rail, this paper investigates the rail service life to a bending fatigue failure of welding parts of rail on the slab track by the structures laboratory testing to derive S-N curves, a GTDAP(General Track Dynamic Analysis Program) to calculate the stresses and a modified Miner's rule to predict a fatigue life. The useful guides for maintenance of rail welded parts on the slab track are proposed in terms of a grinding period and the depth of rail surface irregularities. This study also proposed the guides for maintenance of rail welded part on the ballast track. The effects of fatigue service lives are compared one another.

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Prediction of bending fatigue lifes of rail welded parts (레일용접부 피로수명 예측)

  • 양신추;이진욱;나성훈
    • Proceedings of the KSR Conference
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    • 1999.05a
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    • pp.390-397
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    • 1999
  • This paper investigates about the prediction of rail bending fatigue lifes for the purpose of the effective maintenance of surface irregularities of rail welded parts. The rail bending stresses are calculated using a track dynamic analysis program. The rail surface irregularities measured in situ are given as inputs in the analyses. On the other hand, the S-N curves are derived based on the results of bending fatigue tests. Using data found so far, rail fatigue lifes are estimated adopting a modified Miner's rule. The useful guides for maintenance of rail welded part are proposed in terms of grinding period and grinding depth of rail surface irregularities.

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Fatigue Life Predictions for Variable Load Histories (변동하중하의 피로수명예측)

  • 하재선;송지호;이시중
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.4
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    • pp.760-780
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    • 1988
  • Using the fatigue test results obtained in the SAE Fatigue Cumulative Damage Test Program, prediction methods of fatigue crack initiation life for notched members undergoing random loaming histories were discussed in detail. Conventional fatigue life predictions based on so-called modified Miner's rule were found to be apt to give nonconservative estimate, due to lack of sufficient consideration for stress-interaction effect. A modified .epsilon.-N curve concept was proposed to account for the stress-interaction effect. The predicted fatigue life based on the modified .epsilon.-N curve concept was in good agreement with the experimental results of SAE Test Program. Specifically for the cases when fatigue data was not available at hand, was proposed a procedure to give conservative estimate of fatigue life.

Severeness of Transmission Loads of Agricultural Tractor for Rotary Operations in Poorly Drained Paddy Field (습답 로터리 작업에 대한 농용 트랙터의 변속기 부하 가혹도에 관한 연구)

  • 한경훈;김경욱;오영근
    • Journal of Biosystems Engineering
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    • v.24 no.4
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    • pp.293-300
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    • 1999
  • The objectives of this study were to analyze the load acting on the transmission when tractor performed rotary operations in the poorly drained paddy fields and to compare its severeness with those obtained under different operational conditions. The loads were measured at the input shaft of the transmission and the load spectrum was constructed using the rain-flow cycle counting method. The severeness of the loads was represented by the partial damage sum which was determined by suing the modified Miner's rule. In the field with a shallow hardpan PTO speed affected severeness of the rotary operations greater than the forward speed did. In the field with deep hardpan, on the other hand, the effect of the forward speed was greater. the severeness in the well drained fields did not differ significantly from that in the field with a shallow hardpan. The severest load was recorded in the field with a deep hardpan.

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Effect of Mean Stress on Fatigue Properties in Spring Steel (스프링강의 피로 특성에 미치는 평균 응력의 영향)

  • Seok, Chang-Sung;Kim, Hyung-Ick;Chang, Pil-Soo;Joo, Jae-Man;Kang, Jeong-Hoon
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.255-260
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    • 2003
  • Most of the fatigue test were achieved in fully reversed condition that mean stress is zero. But, generally, mean stress can not be zero. This research was achieved the bending fatigue test that changes mean stress to spring steel and was studied relation with the mean stress and the fatigue life. The method to search effect about mean stress was extended S-N graph in two cases. One method was extended S-N graph using modified Miner's rule with considering damage. Another was extended using tendency of S-N graph. The exponential value(${\alpha}$) of mean stress-alternating stress equation is converged between the Goodman's and the Gerber's value even if fatigue life increases.

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Design of Excavator Boom Structure Based on Fatigue Strength of Weldment(II) (용접부 피로강도를 고려한 굴삭기 붐 구조물 설계(II))

  • Park, Sang-Chul
    • Journal of Welding and Joining
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    • v.29 no.4
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    • pp.61-66
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    • 2011
  • The purpose of this study is to develop improved boom structures with reliable fatigue strength of weldment and lower production cost. For that purpose, multi-body dynamic analysis was performed to evaluate forces acting on arm & boom cylinders and joints of boom structure during operation of an excavator for three working postures, then stress analysis was made to investigate stress distribution around diaphragms at the bottom plate of boom structures which was known to be susceptible to fatigue failures of welded joints, and finally boom structures with optimum arrangement of diaphragms was proposed. This work mainly consists of the following two parts: part 1 focuses on multi-body dynamic analysis of excavators during operation and part 2 includes evaluations of fatigue strength of welded joints for modified boom structures.

Fatigue Life Prediction of Automotive Rubber Component Subjected to a Variable Amplitude Loading (가변진폭하중에서의 자동차 고무 부품의 피로 수명 예측)

  • Kim, Wan-Soo;Kim, Wan-Doo;Hong, Sung-In
    • Elastomers and Composites
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    • v.42 no.4
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    • pp.209-216
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    • 2007
  • Fatigue life prediction methodology of the rubber component made of vulcanized natural rubber under variable amplitude loadings was studied. The displacement-controlled fatigue tests were conducted at different levels and the maximum Green-Lagrange strain was selected as damage parameters. A fatigue life curve of the rubber represented by the maximum Green-Lagrange strain was determined from the nonlinear finite element analysis. The transmission load history of SAE as variable amplitude loading was used to perform the fatigue life prediction. And then a signal processing of variable loading by racetrack and simplified rainflow cycle counting methods were performed. The modified miner's rule as cumulative damage summation was used. Finally, when the gate value is 30%, the predicted fatigue life of the rubber component agreed well with the experimental fatigue lives with a factor of two.

Fatigue Strength Evaluation of Carbody and Bogie Frame for the Light Rail Transit System (경량전철에 대한 차체 및 대차틀의 피로강도평가)

  • Lee, Eun-Chul;Lee, Joon-Seong;Choi, Yoon-Jong;Lee, Jung-Hwan;Suh, Myung-Won;Lee, Ho-Yong;Lee, Yang-Chang
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.10
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    • pp.77-83
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    • 2008
  • In terms of saving costs, energy and materials, the weight of cars has been gradually reduced by optimizing design of structure, which also gives us good performance. In compliance with this, it should satisfy the lifetime of cars for 25 years under the operation. The purpose of this study is to evaluate the strength of fatigue using date from strain gauges attached carbody and bogie frame. This dynamic stress can be evaluated using S-N curve based on stress amplitude. Modified S-N curve by CORTON-DOLAN is used for more conservative and substantial evaluation. In addition, !he loadings itself of carbody and bogie frame are considered by calculating the rate of the differences which are occurred between empty car and fuiiy occupied car with passengers. Rainflow cycle counting method is applied to arrange the stress data for the modified S-N curve to predict lifetime of the materials. Conclusively the cumulative damages are not only calculated by Miner's Rule, but the safety factors are also determined by Goodman diagram.

Study on the Load Properties of Main Shaft of Medium Size Wind-turbine Gearbox using Monitoring (모니터링을 이용한 중형 풍력발전기용 증속기 주축의 부하특성 분석 연구)

  • Park, Young-Joon;Lee, Geun-Ho;Lee, Jong-Won;Nam, Yoon-Su;Cha, Jong-Whan
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.06a
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    • pp.378-382
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    • 2007
  • To improve the reliability for a wind-turbine gearbox, the mechanical loads acting on the gearbox need to be monitored and analysed exactly. This study was conducted to identify the characteristics of torques and bending moments acting on the main shaft of the gearbox using the rainflow counting method and predict the fatigue life of the main shaft by using the modified Miner's rule. While the mean wind speed became 3.5 m/s, the life of the main shaft by the acting torques was predicted as 4.3${\times}10^6$ years, and it by the bending moments was as 2.3${\times}10^4$ years. If the life of the wind turbine was estimated as 20 years, the fatigue life of the main shaft was regarded as infinite. Also, it was suggested that the life of the main shaft must be predicted by not the torques but the bending moments.

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