Correction to: Estimation of Low-Cycle Fatigue Lifetime in Aluminum-Silicon-Magnesium Alloy of Cylinder Heads based on Striation Marks as Failure Features of Fracture Surfaces and Paris Crack Growth Law

The objective of the present paper is to investigate the stress-controlled low-cycle fatigue behavior of piston aluminum-silicon (AlSi) alloy reinforced with nano-clay particles and T6 heat-treatment. The piston aluminum-silicon alloy strengthened by 1 wt.% nano-clay particles were prepared by the stir casting method and then subjected to the heat-treatment. The optical microscopy analysis demonstrates that heat-treatment changed the size, morphology, and distribution of silicon phases through the microstructure of the aluminum matrix. In addition to tensile tests, stress-controlled low-cycle fatigue experiments at different loading conditions including the variation of the mean stress, the stress rate, and the stress amplitude were conducted at room temperature. The obtained experimental results showed no clear improvement in either mechanical or fatigue properties of the material. Moreover, the density measurements using the Archimedes method reveal a higher content of the porosity in nano-composite. It was observed that the reinforcement (nano-particles and heat-treatment) can change the cyclic behavior of the AlSi alloy, significantly. The cyclic hardening feature of the AlSi alloy changed to cyclic softening and also the fatigue lifetime and the ratcheting resistance decreased after the nano-particles addition and heat-treatment. Through the microstructural analysis, it was indicated that the neglecting of higher kinematics of age hardening in nano-composite was the major source of mechanical properties reduction. In the end, it was shown that the fatigue lifetime of samples can be described adequately utilizing a modified plastic strain energy technique considering the mean stress effect.

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Fatigue of AZ91E-T6 Cast Magnesium Alloy

Journal of Engineering Materials and Technology ◽

10.1115/1.2904236 ◽

1993 ◽

Vol 115 (4) ◽

pp. 391-397 ◽

Cited By ~ 49

Author(s):

D. L. Goodenberger ◽

R. I. Stephens

Keyword(s):

Fatigue Crack ◽

Magnesium Alloy ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Low Cycle Fatigue ◽

Fatigue Behavior ◽

Mean Stress ◽

Cycle Fatigue ◽

Cast Magnesium Alloy ◽

Cast Magnesium

The purpose of this research was to obtain room temperature fatigue behavior of AZ91E-T6 cast magnesium alloy and to determine if commonly used models that depict fatigue behavior are applicable to this cast alloy. Axial strain-controlled fatigue behavior using cylindrical specimens were employed to determine low cycle fatigue behavior with strain ratios R = εmin/εmax = 0, −1, and −2. The conventional log-log total strain low cycle fatigue model properly represented the R = −1 axial fatigue data. Significant mean stress relaxation occurred for all R = 0 and −2 axial fatigue tests. However, for the smaller strain amplitude tests with R = 0, sufficient mean stresses were retained such that fatigue life was reduced. The mean strains/stresses had little influence on the cyclic stress-strain curve which exhibited cyclic strain hardening. Mean stress effects were analyzed using the Morrow, SWT and Lorenzo-Laird models and similar, but oftentimes nonconservative, calculations resulted. Region I and II fatigue crack growth behavior was determined using C(T) speciments with load ratios R = Pmin/Pmax = 0.05 and 0.5. Values of ΔKth and (ΔKth)eff were less than 1.5 MPa m and the Paris equation slopes were between 3.3 and 3.9. Quasi-cleavage was predominant for both fatigue crack growth and final fracture regions. The commonly used low cycle fatigue and fatigue crack growth models appear to reasonably represent most of the results with this AZ91E-T6 cast magnesium alloy.

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Low Cycle Fatigue Characteristics of Oxygen-Free Copper for Electric Power Equipment

Materials ◽

10.3390/ma14154237 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4237

Author(s):

Takuma Tanaka ◽

Togo Sugioka ◽

Tatsuya Kobayashi ◽

Ikuo Shohji ◽

Yuya Shimada ◽

...

Keyword(s):

Heat Treatment ◽

Electric Power ◽

Stress Amplitude ◽

Low Cycle Fatigue ◽

Ebsd Analysis ◽

Fatigue Properties ◽

Power Equipment ◽

Cycle Fatigue ◽

Fracture Surfaces ◽

Heat Treated

The effect of heat treatment on tensile and low cycle fatigue properties of the oxygen-free copper for electric power equipment was investigated. The heat treatment at 850 °C for 20 min, which corresponds to the vacuum brazing process, caused the grain growth and relaxation of strain by recrystallization, and thus, the residual stress in the oxygen-free copper was reduced. The tensile strength and 0.2% proof stress were decreased, and elongation was increased by the heat treatment accompanying recrystallization. The plastic strain in the heat-treated specimen was increased compared with that in the untreated specimen under the same stress amplitude condition, and thus, the low cycle fatigue life of the oxygen-free copper was degraded by the heat treatment. Striation was observed in the crack initiation area of the fractured surface in the case of the stress amplitude less than 100 MPa regardless of the presence of the heat treatment. With an increase in the stress amplitude, the river pattern and the quasicleavage fracture were mainly observed in the fracture surfaces of the untreated specimens, and they were observed with striations in the fracture surfaces of the heat-treated ones. The result of the electron backscattered diffraction (EBSD) analysis showed that the grain reference orientation deviation (GROD) map was confirmed to be effective to investigate the fatigue damage degree in the grain by low cycle fatigue. In addition, the EBSD analysis revealed that the grains were deformed, and the GROD value reached approximately 28° in the fractured areas of heat-treated specimens after the low cycle fatigue test.

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