How and why the fatigue S–N curve does not approach a horizontal asymptote

Bathìas, Claude; Drouillac, L.; François, Pierre

doi:10.1016/s0142-1123(01)00123-2

Cited by 169 publications

(108 citation statements)

References 8 publications

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“…Latest developments in the ultrasonic technique are presented by Bathias et al [1][2][3][4][5]. An extensive review of the fundamentals on VHCF fatigue using ultrasonic methods, including considerations on the machine development, its performance and applications, can be found in these works.…”

Section: Introductionmentioning

confidence: 99%

Automation in Strain and Temperature Control on VHCF with an Ultrasonic Testing Facility

Lage

Ribeiro

Montalvão

et al. 2014

Application of Automation Technology in Fatigue and Fracture Testing and Analysis

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Increased safety and reliability in mechanical components became a subject of prime importance over the past recent years. Therefore, a proper understanding of damage and fracture mechanics in materials and components designed to withstand Very High Cycle Fatigue (VHCF) loadings is extremely important nowadays. However, conventional machines used for fatigue testing are very time-consuming and costly in order to perform VHCF tests. Ultrasonic machines have been introduced as a way to increase the number of cycles in fatigue testing up to 1E 8 to 1E 10 cycles within a considerably reduced amount of time. Nevertheless, the accurate measurement of the parameters that influence fatigue life at ultrasonic frequencies (e.g., stress, displacement, strain-rate, temperature and frequency) is still a matter of concern and on-going development. Due to the high frequencies involved in VHCF testing, a huge amount of heat is generated over the specimen, which greatly affects the variables determining the fatigue behavior. This paper describes the design and instrumentation of an ultrasonic fatigue testing machine that operates at 20 kHz working frequency. Among other features, it incorporates automated strain and temperature control. In order to run automated tests, a closed loop monitoring and control system was developed based on the measured temperature and displacement amplitudes. Temperature readings are made with a pyrometer and thermography camera and displacement is monitored at the free end of the specimen with a high resolution laser. The machine's power output is continuously adjusted from the displacement readings, so that the stress variations within the specimen are as flat as possible. When temperature increases above a certain set value, a cooling function is triggered and the test is interrupted until the specimen is cooled down. Data is acquired, managed and processed with a data acquisition device working at 400 kHz sampling frequency.The advantages and limitations of metal fatigue testing at very high frequencies are discussed in this paper, with special emphasis on the strain and temperature control issues. Comparison of tests carried out with and without both displacement and temperature control are made on two metallic alloys, copper 99% and carbon steel, with the determination of S-N curves.

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Section: Introductionmentioning

confidence: 99%

Automation in Strain and Temperature Control on VHCF with an Ultrasonic Testing Facility

Lage

Ribeiro

Montalvão

et al. 2014

Application of Automation Technology in Fatigue and Fracture Testing and Analysis

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“…With equal highly stressed volumes, there is good agreement between conventional and ultrasonic fatigue test results. [5] Regarding the expected results, Bathias et al [2] identified three different types of fatigue crack initiation. Their findings are based on cylindrical samples with polished surfaces, i.e.…”

Section: Introductionmentioning

confidence: 86%

“…the type of specimens generally used in ultrasonic fatigue testing. Bathias et al [2] state that, in the low cycle regime (1e4 cycles), crack initiations are typically multiple and located on the surface. In a megacycle regime (1e6 cycles), crack initiation occurs on the surface but from a single point.…”

Section: Introductionmentioning

confidence: 99%

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QT steel High Cycle Fatigue Testing with Ultrasonic

Korhonen¹,

Kuoppala²,

Väntänen³

et al. 2017

RakMek

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“…Since the work by Naito et al [1], a number of researches have shown that fatigue failures of high-strength steels may occur at the stress lower than the conventional fatigue limit defined at failure cycles of 10 7 [2][3][4][5][6][7]. Different from low cycle fatigue, the crack initiation site for the fatigue life larger than 10 7 (very-high-cycle fatigue, VHCF) for high-strength steels usually changes from the surface to the interior of specimen and the failure is mostly caused by interior non-metallic inclusions.…”

Section: Introductionmentioning

confidence: 99%

Effects of inclusion size and stress ratio on fatigue strength for high-strength steels with fish-eye mode failure

Sun

Lei

Xie

et al. 2013

International Journal of Fatigue

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a b s t r a c tExperimental results indicate that the fatigue life reduces by about two orders of magnitude when inclusion size doubles. Then, a model is proposed for predicting the fatigue strength of high-strength steels with fish-eye mode failure based on the experimental results for the effect of inclusion size and stress ratio. In the model, the effect of inclusion size a 0 and stress ratio R on fatigue strength r a is expressed as r a / a 0, where m and a are material parameters. The predicted results are in good agreement with our experimental results and the ones reported in literature.

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How and why the fatigue S–N curve does not approach a horizontal asymptote

Cited by 169 publications

References 8 publications

Automation in Strain and Temperature Control on VHCF with an Ultrasonic Testing Facility

Automation in Strain and Temperature Control on VHCF with an Ultrasonic Testing Facility

QT steel High Cycle Fatigue Testing with Ultrasonic

Effects of inclusion size and stress ratio on fatigue strength for high-strength steels with fish-eye mode failure

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