Estimation of stress in specimens loaded with ultrasonic fatigue machines

Ultrasonic fatigue testing is an increasingly used method to study the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) properties of materials. Specimens are cycled at an ultrasonic frequency, which leads to a drastic reduction of testing times. This work focused on summarising the current understanding, based on literature data and original work, whether and how fatigue properties measured with ultrasonic and conventional equipment are comparable. Aluminium alloys are not strain-rate sensitive. A weaker influence of air humidity at ultrasonic frequencies may lead to prolonged lifetimes in some alloys, and tests in high humidity or distilled water can better approximate environmental conditions at low frequencies. High-strength steels are insensitive to the cycling frequency. Strain rate sensitivity of ferrite causes prolonged lifetimes in those steels that show crack initiation in the ferritic phase. Austenitic stainless steels are less prone to frequency effects. Fatigue properties of titanium alloys and nickel alloys are insensitive to testing frequency. Limited data for magnesium alloys and graphite suggest no frequency influence. Ultrasonic fatigue tests of a glass fibre-reinforced polymer delivered comparable lifetimes to servo-hydraulic tests, suggesting that high-frequency testing is, in principle, applicable to fibre-reinforced polymer composites. The use of equipment with closed-loop control of vibration amplitude and resonance frequency is strongly advised since this guarantees high accuracy and reproducibility of ultrasonic tests. Pulsed loading and appropriate cooling serve to avoid specimen heating.

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Ultrasonic fatigue testing in as-built and polished Ti6Al4V alloy manufactured by SLM

Forces in Mechanics ◽

10.1016/j.finmec.2021.100024 ◽

2021 ◽

pp. 100024

Author(s):

Pedro R. da Costa ◽

Manuel Sardinha ◽

Luís Reis ◽

Manuel Freitas ◽

Manuel Fonte

Keyword(s):

Fatigue Testing ◽

Ti6al4v Alloy ◽

Ultrasonic Fatigue

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A new method for ultrasonic fatigue testing of equibiaxial and pure shear cruciform specimens

International Journal of Fatigue ◽

10.1016/j.ijfatigue.2021.106423 ◽

2021 ◽

pp. 106423

Author(s):

Pedro R. da Costa ◽

Luís Reis ◽

Diogo Montalvão ◽

Manuel Freitas

Keyword(s):

Fatigue Testing ◽

Pure Shear ◽

New Method ◽

Ultrasonic Fatigue

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Gigacycle Fatigue of Welded Joints of Structural Materials (A Review)

Advanced Engineering Forum ◽

10.4028/www.scientific.net/aef.17.14 ◽

2016 ◽

Vol 17 ◽

pp. 14-30 ◽

Cited By ~ 1

Author(s):

Okechukwu P. Nwachukwu ◽

Alexander V. Gridasov ◽

Ekaterina A. Gridasova

Keyword(s):

Fatigue Testing ◽

Fatigue Behavior ◽

Testing Machine ◽

Structural Materials ◽

Fatigue Tests ◽

Material Defects ◽

Graphite Cast Iron ◽

Ultrasonic Fatigue ◽

Materials Used ◽

Fatigue Failures

This review looks into the state of gigacycle fatigue behavior of some structural materials used in engineering works. Particular attention is given to the use of ultrasonic fatigue testing machine (USF-2000) due to its important role in conducting gigacycle fatigue tests. Gigacycle fatigue behavior of most materials used for very long life engineering applications is reviewed.Gigacycle fatigue behavior of magnesium alloys, aluminum alloys, titanium alloys, spheroid graphite cast iron, steels and nickel alloys are reviewed together with the examination of the most common material defects that initiate gigacycle fatigue failures in these materials. In addition, the stage-by-stage fatigue crack developments in the gigacycle regime are reviewed. This review is concluded by suggesting the directions for future works in gigacycle fatigue.

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A Comparative Study on Infrared Thermography during Ultrasonic Fatigue Testing of Cast Steel 42CrMo4 and Cast Aluminium Alloy AlSi7Mg

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.592-593.501 ◽

2013 ◽

Vol 592-593 ◽

pp. 501-504 ◽

Cited By ~ 1

Author(s):

Dominik Krewerth ◽

Anja Weidner ◽

Horst Biermann

Keyword(s):

Aluminium Alloy ◽

Infrared Thermography ◽

Fatigue Testing ◽

Cast Steel ◽

Material Testing ◽

Initiation Point ◽

Testing Method ◽

Cast Aluminium ◽

Ultrasonic Fatigue ◽

Non Destructive

The present paper illustrates a comparison of infrared thermography during ultrasonic fatigue testing of cast steel 42CrMo4 and cast aluminium alloy AlSi7Mg. Against the background of different material properties (e.g. mechanical properties as well as thermal properties) the benefit of this non-destructive material testing method in terms of determining the crack initiation point and time during fatigue testing as well as crack propagation is evaluated and discussed. Moreover, correlations between fractography and infrared thermography are performed for both materials.

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Experimental Evidence of Specimen-Size Effects on EN-AW6082 Aluminum Alloy in VHCF Regime

Applied Sciences ◽

10.3390/app11094272 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4272

Author(s):

Stefano Invernizzi ◽

Francesco Montagnoli ◽

Alberto Carpinteri

Keyword(s):

Aluminium Alloy ◽

Cross Section ◽

Fatigue Testing ◽

Testing Machine ◽

Experimental Tests ◽

Theoretical Explanation ◽

Specimen Size ◽

Section Surface ◽

Middle Cross Section ◽

Ultrasonic Fatigue

The present paper investigates the influence of the specimen size of EN-AW6082 wrought aluminium alloy subjected to very high cycle fatigue (VHCF) tests. The hourglass specimens were tested under fully reversed loading condition, up to 109 cycles, by means of the ultrasonic fatigue testing machine developed by Italsigma® (Italy). Three specimens groups were considered, with a diameter in the middle cross-section ranging from 3 mm up to 12 mm. The stress field in the specimens was determined numerically and by strain gauge measurements in correspondence of the cross-section surface. The dispersion of experimental results has been accounted for, and data are reported in P-S-N diagrams. The decrease in fatigue resistance with increasing specimen size is evident. Theoretical explanation for the observed specimen-size effect is provided, based on Fractal Geometry concepts, allowing to obtain scale independent P-S*-N curves. The fatigue life expectation in the VHCF regime of the EN-AW6082 aluminium alloy full-scale components is rather overestimated if it is assessed only from standard small specimens of 3 mm in diameter. Experimental tests carried out on larger specimens, and a proper extrapolation, are required to assure safe structural design.

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Effect of Plasma Nitriding on Ultra-High Cycle Fatigue Behaviors of Ti-6Al-4V

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.295-297.2386 ◽

2011 ◽

Vol 295-297 ◽

pp. 2386-2389 ◽

Cited By ~ 1

Author(s):

Ren Hui Tian ◽

Qiao Lin Ouyang ◽

Qing Yuan Wang

Keyword(s):

High Cycle Fatigue ◽

Plasma Nitriding ◽

Fatigue Behavior ◽

Fatigue Crack Initiation ◽

Fatigue Tests ◽

Fatigue Properties ◽

Cycle Fatigue ◽

Ultrasonic Fatigue ◽

Ultra High Cycle Fatigue ◽

Stress Ratios

In order to investigate the effect of plasma nitriding treatment on fatigue behavior of titanium alloys, very high cycle fatigue tests were carried out for Ti-6Al-4V alloy using an ultrasonic fatigue machine under load control conditions for stress ratios of R=-1 at frequency of ƒ=20KHz. Experiment results showed that plasma nitriding treatment played the principal role in the internal fatigue crack initiation. More importantly, plasma nitriding treatment had a detrimental effect on fatigue properties of the investigated Ti-6Al-4V alloy, and the fatigue strength of material after plasma nitriding treatment appeared to be significantly reduced about 17% over the untreated material.

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