Measuring techniques for the very high cycle fatigue behaviour of high strength steel at ultrasonic frequencies

Köster, M.; Nutz, Helga; Freeden, Willi; Eifler, Dietmar

doi:10.3139/146.110623

Cited by 12 publications

(4 citation statements)

References 9 publications

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“…The displacement of the specimens at the free end is measured by the LDV and recorded with a rate of 500 kHz. All these parameters are appropriate to control the process and to characterize the fatigue behavior [11]. The measurement of the displacement is additionally used to determine the exact number of cycles per ultrasonic pulse.…”

Section: Methodsmentioning

confidence: 99%

Very High Cycle Fatigue and Damage Behavior of Ti6Al4V

Stefan

Eifler

2015

KEM

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High frequency fatigue tests were carried out with a 20 kHz ultrasonic testing facility to investigate the cyclic deformation behavior of Ti6Al4V in the Very High Cycle Fatigue (VHCF) regime in detail. The S,Nf -curve at the stress ratio R = -1 shows a significant decrease of the stress amplitude and a change from surface to subsurface failures in the VHCF regime for more than 107 cycles. Microscopic investigations of the distribution of the α-and β-phase of Ti6Al4V indicate that inhomogeneities in the phase distribution are reasons for the internal crack initiation. Scanning electron microscopy as well as light microscopy were used to investigate the internal crack initiation phenomenon in the VHCF-regime. Beside the primary fatigue crack additional defects like micro cracks and crack clusters were observed in the fatigued specimens. SEM-investigations of specimens which were loaded up to 1010 cycles without failure show irreversible microstructural changes inside the specimens. Two step tests were performed to evaluate the influence of internal fatigue induced defects observed in specimens which did not fail within 1010 cycles.

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Section: Methodsmentioning

confidence: 99%

Very High Cycle Fatigue and Damage Behavior of Ti6Al4V

Stefan

Eifler

2015

KEM

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“…The physical parameters described above can also be used to characterize the fatigue behavior in the very high cycle fatigue regime (Koster et al, 2011(Koster et al, , 2012. The ultrasonic fatigue tests were performed with the in-house-developed test system "UltraFAST-WKK-Kaiserslautern" (UFK) which is described in detail with all sensors used in the VHCF experiments in Heinz et al, 2011.…”

Section: Temperature and Resistance Measurements To Characterize The mentioning

confidence: 99%

Fatigue monitoring of metals based on mechanical hysteresis, electromagnetic ultrasonic, electrical resistance and temperature measurements

Eifler

Smaga

Klein

2016

Mechanical Engineering Journal

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Alternatively to conventional stress-strain hysteresis measurements in this paper physically based materials data such as specimen temperature, electrical resistance, speed of sound or generator power are used to describe the cyclic deformation behavior of metals in the high cycle (HCF) and the very high cycle fatigue (VHCF) regime. The mentioned physical parameters depend in a characteristic manner on the load and cycle dependent microstructure of metals. The change in temperature is proportional to the dissipated energy due to cyclic plastic deformation, the electrical resistance and speed of sound in metals depend on the individual dislocation and defect structure. Amongst others the generator power of ultrasonic testing machines is influenced by the internal friction of the material and consequently from the microstructure of a fatigued material. In analogy to the plastic strain amplitude all these data can be used to describe the cyclic deformation behavior and to calculate S, N-curves. The materials investigated are taken from technical components such as power plants, high speed trains and automotive industry to demonstrate that the presented methods and physical parameters can be used to describe the cyclic deformation and fatigue behavior of different steels with different microstructures. Related to the regarded materials and fatigues states SEM and TEM investigations were used to identify microstructural details such as slip bands, micro cracks, crack initiation sites and typical dislocation structures as well as phase transformations.

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“…There are different experimental technics developed recently to study fatigue damage and crack initiation mechanisms during the VHCF process 17,28–33 . A fracture surface topographic analysis (FRASTA) method has been used to study crack initiation and propagation behavior 17 .…”

Section: Introductionmentioning

confidence: 99%

“…17 Analytical approaches based on localized stress concentration and simulation have been used to study the large scatter of testing results. 28,29 Three-point bending 30 and stepwise load block 31 have been used to study fatigue damage. In situ damage assessment or crack initiation study using either nonlinear ultrasonic measurement 32 or synchrotron X-ray diffraction 33 are very interesting methods to study VHCF behavior.…”

Section: Introductionmentioning

confidence: 99%

Formation of fine granular area in a non‐defect matrix of austenitic stainless steel during very high cycle fatigue

Chai

Bergström

Burman

2023

Fatigue Fract Eng Mat Struct

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A fine granular area, FGA, is a typical phenomenon observed at the very high cycle fatigue fracture crack origin with a subsurface defect in the material. The FGA has been widely investigated, and different mechanisms have been proposed. In this paper, the formation of FGA in a non‐defect matrix of one austenitic steel during very high cycle fatigue was studied using a progressive stepwise load‐increasing method and electron scanning microscopy/electron channeling contrast imaging (ECCI) technique. A nano rough surface area or FGA at the fatigue crack origin has been observed in the subsurface matrix without any defect. It is a new phenomenon. A mechanism was proposed using the dislocation plasticity theory. The formation of FGA in a non‐defect matrix is a localized plasticity exhausting process by strain localization, grain fragmentation, stress concentration and nano crack initiation and propagation along low‐angle grain boundaries.

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Measuring techniques for the very high cycle fatigue behaviour of high strength steel at ultrasonic frequencies

Cited by 12 publications

References 9 publications

Very High Cycle Fatigue and Damage Behavior of Ti6Al4V

Very High Cycle Fatigue and Damage Behavior of Ti6Al4V

Fatigue monitoring of metals based on mechanical hysteresis, electromagnetic ultrasonic, electrical resistance and temperature measurements

Formation of fine granular area in a non‐defect matrix of austenitic stainless steel during very high cycle fatigue

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