• Title/Summary/Keyword: Ultrasonic Fatigue Test

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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.

The Effect of Ultrasonic Impact Treatment(UIT) for Fatigue Life of Weldment (Ultrasonic Impact Treatment(UIT)효과가 용접재의 피로수명에 미치는 영향)

  • Song, Jun-Hyouk;Lee, Hyun-Woo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.6
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    • pp.38-45
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    • 2010
  • Welding structures are designed to endure its expected life. The most important factors are life. Especially on welded structure, fatigue strength is critical. So this study performed a research on Box and T shape weldment specimen to examine the influence of welding type. In this experiment, the results indicate Box shape was available in more than T shape. Fatigue tests were performed to evaluate the fatigue strength of the both as-welded and statically pre-loaded specimens by 3 point bending load. Fatigue life can be improved by using Ultrasonic Impact Treatment(UIT) effect. Ultrasonic Impact Treatment(UIT) is excellent for eliminating the tensile residual stresses and generating compressive residual stresses which elevate fatigue strength of welded structures. Also, this shows that welding part has better fatigue life and welding was performed well. In this study, to evaluate the Ultrasonic Impact Treatment(UIT) effect, for welding structure, the experiment was conducted at various levels of stress range between 100MPa and 500MPa. From the test results, it was indicated that fatigue performance was improving by Ultrasonic Impact Treatment(UIT)

The Prediction of Fatigue Damage for Pressure Vessel Materials using SH Ultrasonic Wave (압력용기 고온 고압부의 피로손상 예측을 위한 SH 초음파 평가 기법 개발)

  • Kang, Yong-Ho;Chung, Yong-Keun;Park, Jong-Jin;Park, Ik-Min
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.678-683
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    • 2003
  • Ultrasonic method using SH(shear horizontal) wave has been developed to determine the surface damage in fatigued material. Fatigue damages based on propagation energy were analyzed by multiregression analysis and phase measurement in interrupted fatigue test specimen including CrMoV and 12Cr alloy steel. From the test results, as the fatigue damage increased the propagation time of the launched waves increased and amplitude of wavelet decreased. Also, analysis for the waveform modulation showed a reliable estimation, with confidence limit of 97% for 12Cr steel and 95% for CrMoV steel, respectively. Therefore, It is thought that SH ultrasonic wave technique can be applied to determine fatigue damage of in-service component nondestructively.

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The Prediction of Fatigue Damage for Pressure Vessel Materials using Shear Horizontal Ultrasonic Wave (SH(shear horizontal) 초음파를 이용한 압력용기용 재료의 피로손상 예측)

  • Kang, Yong-Ho;Chung, Yong-Keun;Song, Jung-Il
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.6
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    • pp.90-96
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    • 2009
  • Ultrasonic method using SH(shear horizontal) wave has been developed to determine the surface damage in fatigued material. Fatigue damages based on propagation energy were analyzed by multi-regression analysis in interrupted fatigue test specimen including CrMoV and 12Cr alloy steel. From the test results, as the fatigue damage increased the propagation time of the launched waves increased and amplitude of wavelet decreased. Also, analysis for the waveform modulation showed a reliable estimation, with confidence limit of 97% for 12Cr steel and 95% for CrMoV steel, respectively. Therefore, It is thought that SH ultrasonic wave technique can be applied to determine fatigue damage of in-service component nondestructively.

Ultrasonic evaluation of small surface fatigue cracks initiating in residual stress zone (잔류응력 영역에서 발생한 작은 피로균열의 초음파 평가)

  • Kang Kae-Myung;Kim Jin-Yeon
    • Journal of the Korean Institute of Gas
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    • v.4 no.1 s.9
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    • pp.55-62
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    • 2000
  • A surface acoustic wave method for the evaluation of small fatigue crack initiated from a pit-type surface flaw is presented. In-situ ultrasonic experiments are performed for aluminum 2024-T3 alloy samples under the fatigue test. During the fatigue test, the surface acoustic wave reflection signal from the pit and crack is measured under different hold-stress levels. From the measured and predicted surface wave reflections the depths of fully and partially open cracks are determined and results are verified by comparing with SEM fractography The crack opening behavior of the fatigue crack is evaluated from the predicted effective crack depths. The method developed in this study can be applied to monitor and characterize crack initiation and propagation from pit-type surface flaws in the early stage of fatigue life.

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Applied Cases and Application Technologies of Ultrasonic Nanocrystalline Surface Modification and Accelerated Fatigue Life Evaluation Using Ultrasonic Elastic Vibrational Energy (초음파탄성진동에너지를 이용한 표면개질처리 및 가속피로수명평가 기술의 적용사례 및 응용기술)

  • Jo, In-Sik;Jo, In-Ho;Oh, Joo-Yeon;Lee, Chang-Soon;Pyoun, Young-Sik;Park, In-Gyu
    • Transactions of the KSME C: Technology and Education
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    • v.1 no.1
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    • pp.115-121
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    • 2013
  • It is greatly expected that the technologies of durability enhancement and evaluation for the core structures of plant facilities, marine plant and bridge constructures will be greatly expanded in the plant industry fields. In this study, the actively ongoing applied cases were tried to be analyzed in the present domestic industry fields through the Ultrasonic Nanocrystalline Surface Modification (UNSM) and Ultrasonic Fatigue Test (UFT) technologies using ultrasonic elastic vibrational energy, and the new application technology to improve the durability of plant industry field, especially plant facilities, marine plant and core weld components of bridge constructures will be presented.

Rolling Contact Fatigue and Residual Stress Properties of SAE52100 Steel by Ultrasonic Nano-Crystalline Surface Modification (UNSM) (초음파 나노표면 개질처리를 통한 베어링강의 회전접촉피로 및 잔류응력 특성에 대한 연구)

  • Lee, Changsoon;Park, Ingyu;Cho, Insik;Hong, Junghwa;Jhee, Taegu;Pyoun, Youngsik
    • Journal of the Korean Society for Heat Treatment
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    • v.21 no.1
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    • pp.10-19
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    • 2008
  • To investigate the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue and residual stress properties of bearing steels, this paper carried out a rolling contact fatigue test, measured residual stress and retained austenite, performed a wear test, observed microstructure, measured micro hardness, and analyzed surface topology. After the UNSM treatment, it was found that the surface became minute by over $100{\mu}m$. The micro surface hardness was changed from Hv730~740 of base material to Hv850~880 with about 20% improvement, and hardening depth was about 1.3 mm. The compressive residual stress was measured as high as -700~-900 MPa, and the quantity of retained austenite was reduced to 27% from 34%. The polymet RCF-6 ball type rolling contact fatigue test showed over 4 times longer fatigue lifetime after the UNSM treatment under 551 kgf load and 8,000 rpm. In addition, this paper observed the samples, which went through the rolling contact fatigue test, with OM and SEM, and it was found that the samples had a spalling phenomenon (the race way is decentralized) after the UNSM treatment. However, before the treatment, the samples had excessive spalling and complete exploration. Comparison of the test samples before and after the UNSM treatment showed a big difference in the fatigue lifetime, which seems to result from the complicated effects of micro particles, compressive residual stress, retained austenite, and surface topology.

Technical Review of Specimens under Ultrasonic Fatigue Test (초음파 피로시험편 결정법의 연구동향)

  • Myeong, No-Jun;Han, Seung-Wook;Park, Jung-Hoon;Choi, Nak-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.8
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    • pp.967-973
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    • 2013
  • An accelerated ultrasonic fatigue test(UFT) has been used for analyzing very high cycle fatigue( VHCF, $N_f$ > $10^7$). This study reviews how the test specimen is to be determined. We focus on UFT using a resonance of 20 kHz. The specimen geometry is determined by selecting test materials by using a dynamic Young's modulus and wavelength of 20 kHz. The dynamic Young's modulus is calculated at the resonant frequency. Through a resonant vibration test at 20 kHz, the length of the specimen is calculated. By determining the shape of the specimen, the stress during the UFT is calculated. The UFT results should be comparable at the test frequency and the specimen geometry obtained by the conventional fatigue tests.

Evaluation of Creep-Fatigue Damage in 304 Stainless Steel using Ultrasonic Non-Destructive Test (초음파 비파괴 검사를 이용한 AISI 304 스테인리스강의 크리프-피로 손상의 평가)

  • Lee, Sung Sik;Oh, Yong Jun;Nam, Soo Woo
    • Korean Journal of Metals and Materials
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    • v.49 no.12
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    • pp.924-929
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    • 2011
  • It is well known that grain boundary cavitation is the main failure mechanism in austenitic stainless steel under tensile hold creep-fatigue interaction conditions. The cavities are nucleated at the grain boundary during cyclic loading and grow to become grain boundary cracks. The attenuation of ultrasound depends on scattering and absorption in polycrystalline materials. Scattering occurs when a propagation wave encounters microstructural discontinuities, such as internal voids or cavities. Since the density of the creep-fatigue cavities increases with the fatigue cycles, the attenuation of ultrasound will also be increased with the fatigue cycles and this attenuation can be detected nondestructively. In this study, it is found that individual grain boundary cavities are formed and grow up to about 100 cycles and then, these cavities coalesce to become cracks. The measured ultrasonic attenuation increased with the cycles up to cycle 100, where it reached a maximum value and then decreased with further cycles. These experimental measurements strongly indicate that the open pores of cavities contribute to the attenuation of ultrasonic waves. However, when the cavities develop, at the grain boundary cracks whose crack surfaces are in contact with each other, there is no longer any open space and the ultrasonic wave may propagate across the cracks. Therefore, the attenuation of ultrasonic waves will be decreased. This phenomenon of maximum attenuation is very important to judge the stage of grain boundary crack development, which is the indication of the dangerous stage of the structures.