0920 Evaluation of fatigue life and fatigue properties of the Mg alloy under different R ratios.

Local tensile properties and fatigue properties of Al-Zn-Mg alloy welded joint were investigated. Experiment results show that A7N01 aluminium alloy welded joint is highly inhomogenous both in microstructure and mechanical performances. Ultimate tensile strength and yield strength of base metal are superior compared to HAZ and weld metal. U-shape notched specimens were used in fatigue tests to study local fatigue properties of the joint. Fatigue tests results demonstrate that the difference of local fatigue life is conspicuous in the three regions. The difference of yield strength is believed to result from the diversity of fatigue life for each region in A7N01 aluminium alloy welded joint.

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Effect of Texture and {10-12} Twin on the Low Cycle Fatigue Properties of Rolled AZ31 Mg Alloy

Korean Journal of Metals and Materials ◽

10.3365/kjmm.2013.51.5.325 ◽

2013 ◽

Vol 51 (5) ◽

pp. 325-332 ◽

Cited By ~ 5

Author(s):

Sung Hyuk Park ◽

Seong-Gu Hong ◽

Chong Soo Lee ◽

Ha Sik Kim

Keyword(s):

Low Cycle Fatigue ◽

Mg Alloy ◽

Fatigue Properties ◽

Cycle Fatigue ◽

Az31 Mg Alloy

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Investigation of Changes in Fatigue Damage Caused by Mean Load under Block Loading Conditions

Materials ◽

10.3390/ma14112738 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2738

Author(s):

Roland Pawliczek ◽

Tadeusz Lagoda

Keyword(s):

Fatigue Life ◽

Fatigue Damage ◽

Strain Curve ◽

Mean Value ◽

Fatigue Properties ◽

Stress Strain ◽

Reference Case ◽

Block Loading ◽

The Mean ◽

Mean Strain

The literature in the area of material fatigue indicates that the fatigue properties may change with the number of cycles. Researchers recommend taking this into account in fatigue life calculation algorithms. The results of simulation research presented in this paper relate to an algorithm for estimating the fatigue life of specimens subjected to block loading with a nonzero mean value. The problem of block loads using a novel calculation model is presented in this paper. The model takes into account the change in stress–strain curve parameters caused by mean strain. Simulation tests were performed for generated triangular waveforms of strains, where load blocks with changed mean strain values were applied. During the analysis, the degree of fatigue damage was compared. The results of calculations obtained for standard values of stress–strain parameters (for symmetric loads) and those determined, taking into account changes in the curve parameters, are compared and presented in this paper. It is shown that by neglecting the effect of the mean strain value on the K′ and n′ parameters and by considering only the parameters of the cyclic deformation curve for εm = 0 (symmetric loads), the ratio of the total degree of fatigue damage varies from 10% for εa = 0.2% to 3.5% for εa = 0.6%. The largest differences in the calculation for ratios of the partial degrees of fatigue damage were observed in relation to the reference case for the sequence of block n3, where εm = 0.4%. The simulation results show that higher mean strains change the properties of the material, and in such cases, it is necessary to take into account the influence of the mean value on the material response under block loads.

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Quantitative Analysis of Inclusion Engineering on the Fatigue Property Improvement of Bearing Steel

Metals ◽

10.3390/met9040476 ◽

2019 ◽

Vol 9 (4) ◽

pp. 476 ◽

Cited By ~ 3

Author(s):

Chao Gu ◽

Min Wang ◽

Yanping Bao ◽

Fuming Wang ◽

Junhe Lian

Keyword(s):

Fatigue Life ◽

Quantitative Analysis ◽

Critical Size ◽

Fatigue Behavior ◽

Fatigue Cracks ◽

Fatigue Property ◽

Bearing Steel ◽

Fatigue Properties ◽

Bearing Steels ◽

Inclusion Distribution

The fatigue property is significantly affected by the inner inclusions in steel. Due to the inhomogeneity of inclusion distribution in the micro-scale, it is not straightforward to quantify the effect of inclusions on fatigue behavior. Various investigations have been performed to correlate the inclusion characteristics, such as inclusion fraction, size, and composition, with fatigue life. However, these studies are generally based on vast types of steels and even for a similar steel grade, the alloy concept and microstructure information can still be of non-negligible difference. For a quantitative analysis of the fatigue life improvement with respect to the inclusion engineering, a systematic and carefully designed study is still needed to explore the engineering dimensions of inclusions. Therefore, in this study, three types of bearing steels with inclusions of the same types, but different sizes and amounts, were produced with 50 kg hot state experiments. The following forging and heat treatment procedures were kept consistent to ensure that the only controlled variable is inclusion. The fatigue properties were compared and the inclusions that triggered the fatigue cracks were analyzed to deduce the critical sizes of inclusions in terms of fatigue failure. The results show that the critical sizes of different inclusion types vary in bearing steels. The critical size of the spinel is 8.5 μm and the critical size of the calcium aluminate is 13.5 μm under the fatigue stress of 1200 MPa. In addition, with the increase of the cleanliness of bearing steels, the improvement of fatigue properties will reach saturation. Under this condition, further increasing of the cleanliness of the bearing steel will not contribute to the improvement of fatigue property for the investigated alloy and process design.

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Effect of precipitate free zones on low cycle fatigue life of Al–Zn–Mg alloy

Materials Science and Technology ◽

10.1179/mst.1995.11.9.921 ◽

1995 ◽

Vol 11 (9) ◽

pp. 921-925 ◽

Cited By ~ 12

Author(s):

D. S. Park ◽

S. W. Nam

Keyword(s):

Fatigue Life ◽

Low Cycle Fatigue ◽

Mg Alloy ◽

Cycle Fatigue

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Effect of Graphene Nanoplatelets (GNPs) on Fatigue Properties of Asphalt Mastics

Materials ◽

10.3390/ma14174864 ◽

2021 ◽

Vol 14 (17) ◽

pp. 4864

Author(s):

Ke Li ◽

Haisheng Ren ◽

Weirong Huang

Keyword(s):

Growth Rate ◽

Fatigue Life ◽

Graphene Nanoplatelets ◽

Fatigue Properties ◽

Modified Asphalt ◽

Good Linear ◽

Asphalt Mastics ◽

Time Sweep ◽

Time Sweep Test ◽

Good Linear Correlation

To investigate the effect of graphene on the fatigue properties of base asphalt mastics, graphene nanoplatelets (GNPs)-modified asphalt mastics and base asphalt mastics were prepared. A dynamic shear rheometer (DSR) was used to conduct the tests in the stress-controlled mode of a time-sweep test. The results showed that GNPs can improve the fatigue life of asphalt mastic. Under a stress of 0.15 MPa, the average fatigue life growth rate (ω¯) was 17.7% at a filler-asphalt ratio of 0.8, 35.4% at 1.0, and 45.2% at 1.2; under a stress of 0.2 MPa, the average fatigue life growth rate (ω¯) was 17.9% at a filler-asphalt ratio of 0.8, 25.6% at 1.0, and 38.2% at 1.2. The growth value (ΔT) of fatigue life of GNPs-modified asphalt mastics increased correspondingly with the increase of filler–asphalt ratio, the correlation coefficient R2 was greater than 0.95, and the growth amount showed a good linear relationship with the filler–asphalt ratio. In the range of 0.8~1.2 filler–asphalt ratio, the increase of mineral powder can improve the fatigue life of asphalt mastics, and there is a good linear correlation between filler–asphalt ratio and fatigue life. The anti-fatigue mechanism of GNPs lies in the interaction between GNPs and asphalt, as well as its own lubricity and thermal conductivity.

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Low Cycle Fatigue Properties of FGH720Li Superalloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1035.292 ◽

2021 ◽

Vol 1035 ◽

pp. 292-296

Author(s):

Zi Chao Peng ◽

Jun Ying Sheng ◽

Xu Qing Wang ◽

Yue Tang

Keyword(s):

Fatigue Life ◽

Powder Metallurgy ◽

Applied Stress ◽

Low Cycle Fatigue ◽

Influencing Factor ◽

Fatigue Tests ◽

Fatigue Properties ◽

Nickel Base Superalloy ◽

Loading Frequency ◽

Cycle Fatigue

Low cycle fatigue (LCF) properties of a powder metallurgy(PM) nickel base superalloy FGH720Li were systematically studied in this work, including smooth LCF and notched LCF tested at various temperatures and different stress. The relationship between the fatigue life and applied stress was analyzed both for smooth fatigue and notch fatigue tests. The effects of loading frequency and stress ratio on LCF behavior were also studied. As an important influencing factor of the fatigue life in powder metallurgy superalloy, the effect of inclusions on LCF life was also investigated. The results showed that the fatigue properties of FGH720Li alloy was excellent, when tested at the temperature of 450°C and applied stress of 1230MPa, the fatigue life could exceed 5×104 cycles. When tested at 650°C and 1150MPa, the average fatigue life was still beyond 2×105 cycles.

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Fatigue Life Improvement of the High Strength Steel Welded Joints by Ultrasonic Impact Peening

Metals ◽

10.3390/met9060619 ◽

2019 ◽

Vol 9 (6) ◽

pp. 619 ◽

Cited By ~ 5

Author(s):

Ján Lago ◽

Libor Trško ◽

Michal Jambor ◽

František Nový ◽

Otakar Bokůvka ◽

...

Keyword(s):

Residual Stress ◽

Fatigue Life ◽

Welded Joints ◽

Compressive Residual Stress ◽

High Strength ◽

Fatigue Properties ◽

Low Alloy Steel ◽

Residual Stress Field ◽

Near Surface ◽

Life Improvement

Ultrasonic impact peening was applied on welded joints manufactured from Strenx 700 MC high strength low alloy steel with the aim to improve the fatigue properties. Three different surface treatment parameters were tested, which resulted in transformation of the near-surface tensile residual stresses in the weld metal and heat affected zone to compressive residual stress field, while maximal values from −400 MPa up to −800 MPa were reached. The highest fatigue life improvement was reached by the double peening with the 85 N contact force, where the fatigue limit for N = 108 cycles increased from 370 MPa to 410 MPa.

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The Influence of Laser Shock Peening on Fatigue Properties of AA2024-T3 Alloy with a Fastener Hole

Metals ◽

10.3390/met10040495 ◽

2020 ◽

Vol 10 (4) ◽

pp. 495

Author(s):

Ruslan Sikhamov ◽

Fedor Fomin ◽

Benjamin Klusemann ◽

Nikolai Kashaev

Keyword(s):

Fatigue Life ◽

Fatigue Cracks ◽

Initial Crack ◽

Fatigue Tests ◽

Laser Shock Peening ◽

Fatigue Properties ◽

Hole Drilling ◽

Laser Shock ◽

Fastener Hole ◽

Shock Peening

The objective of the present study was to estimate the influence of laser shock peening on the fatigue properties of AA2024-T3 specimens with a fastener hole and to investigate the possibility to heal the initial cracks in such specimens. Fatigue cracks of different lengths were introduced in the specimens with a fastener hole before applying laser shock peening. Deep compressive residual stresses, characterized by the hole drilling method, were generated into the specimens by applying laser shock peening on both sides. Subsequently, the specimens were subjected to fatigue tests. The results show that laser shock peening has a positive effect regarding the fatigue life improvement in the specimens with a fastener hole. In addition, laser shock peening leads to a healing effect on fatigue cracks. The efficiency of this effect depends on the initial crack length. The effect of laser shock peening on the fatigue life periods was determined by using resonant frequency graphs.

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