Fatigue Life Of Magnesium Alloy Research Articles

Ratcheting behavior of surface‐modified AZ80 magnesium alloy after pre‐corrosion in simulated body fluids with various pH values

AbstractAZ80 magnesium alloy was surface treated by micro‐arc oxidation (MAO) and composite of laser shock penning (LSP) and MAO techniques. Untreated and treated specimens were pre‐corroded in simulated body fluids (SBF) with different pH values (pH 4, 7.4, and 9). The ratcheting behavior of all test specimens was experimentally investigated under stress‐controlled loading. The positive or negative value of the ratcheting strain reflects the mechanism of cyclic deformation. The ratcheting strain with negative values is associated with the cyclic deformation being dominated by twinning–detwinning, while the ratcheting strain with positive values is due to dislocation slip playing a dominant role in the cyclic deformation. A higher absolute value of the ratcheting strain means a lower the ratcheting life. Single MAO coating is not conducive to the fatigue life of magnesium alloy in acidic SBF environment, while LSP/MAO composite coating can improve the fatigue life of magnesium alloy under various loading conditions and different pH environment.

Improving low-cycle fatigue life of ZK61 magnesium alloy via basal texture weakening by the compression-extrusion process

In response to the problem that intense basal texture seriously affects the low-cycle fatigue life of magnesium alloys, the compression-extrusion process for basal texture weakening was implemented in ZK61 magnesium alloys. The low-cycle fatigue life under uniaxial symmetrical tension-compression cyclic loading was dramatically improved by basal texture weakening, up to 1.5∼3 times that in an intense-textured state. Basal texture weakening promoted basal slip to dominate the cyclic deformation, thus significantly reducing the cyclic tension-compression asymmetry caused by the {10–12} twinning-detwinning. Further, the suppression of {10–12} twinning and the decrease of compressive plastic strain slowed down dislocation accumulation inhibiting the cyclic hardening and fatigue crack initiation. The Manson-Coffin equation was feasible to predict the fatigue life of the intense-textured and weak-textured ZK61 magnesium alloys. The promotion of basal slip arising from basal texture weakening led to the decrease of fatigue ductility coefficient and the increase of fatigue ductility exponent contributing to the higher fatigue life.

Bee colony intelligence in fatigue life estimation of simulated magnesium alloy welds

The fatigue life of magnesium alloy is influenced by many factors such as stress concentration factor, stress ratio and stress amplitude as well as different material states. Since all these factors affect the fatigue life of the alloy, the effects of these parameters need to be investigated. This study aims to obtain fatigue life values with satisfactory results on the samples of magnesium alloy AZ31. In order to solve the problem, firstly an exponential-trigonometric function model is constructed. Secondly, an artificial bee colony algorithm is used to optimize the weights of this function. Sample data of the alloy is used to verify the correctness of the fatigue life estimation model. The estimated results are compared with the results of experimental studies. Simulation results show that the fatigue life prediction model proposed in this paper can fit the experimental Wöhler lines with high estimation accuracy. The model based on artificial bee colony is a good candidate to estimate the fatigue life of magnesium alloy.

Estimation of High Cycle Fatigue Life of AZ91E-Ni Coated Al2O3 Particulate Nano Composites Using Reliability Based Approach

This paper presents a method to determine sample size for estimating fatigue life of Magnesium alloy composites. Semi solid stir casting methodology was employed for the preparation of composites and the effect of nano Al2O3 as well as Nickel coated nano Al2O3 reinforcements on the fatigue life of AZ91E Magnesium alloy has been studied. Rotating beam bending machine is used to calculate the high cycle fatigue strength under fully reversed conditions. Fatigue tests are conducted at five different stress levels and at each stress level, minimum sample size is determined using statistical design. S–N curve for AZ91E and its composites are presented and compared. A regression analysis is performed for the S–N curve and the developed equations are validated through analysis of variance.

Neural Network Based on Sum Squared Relative Error to Predict the Multixial Fatigue Life of Magnesium Alloy

Neural Network Based on Sum Squared Relative Error to Predict the Multixial Fatigue Life of Magnesium Alloy

Temperature evolution and fatigue life evaluation of AZ31B magnesium alloy based on infrared thermography

The surface temperature of extruded AZ31B alloy plate was measured by infrared thermograph in air during tension and high-cycle fatigue tests. The mechanism of heat production was discussed and the value of critical fatigue damage temperature was calculated according to the P—ΔT curve. Results show that the variation trend of temperature is different between tension and fatigue tests. The temperature evolution in tension test consists of four stages: linear decrease, reverse linear increase, abrupt increase, and final drop. The initial decrease of temperature is caused by thermal elastic effect, which is corresponding to the elastic deformation in tension progress. When cyclic loading is above the fatigue limit, the temperature evolution mainly undergoes five stages: initial increase, steep reduction, steady state, abrupt increase, and final drop. The peak temperature in fatigue test is caused by strain hardening that can be used to evaluate the fatigue life of magnesium alloy. The critical temperature variation that causes the fatigue failure is 3.63 K. When ΔT≤3.63 K, the material is safe under cyclic loading. When ΔT>3.63 K, the fatigue life is determined by cycle index and peak temperature.

Prediction on Residual Stress and Fatigue Life of Magnesium Alloy Treated by Laser Shot Peening

Numerical study on fatigue life of ZK60 magnesium alloy plate before and after laser shot peening (LSP) was carried out in this paper. Based on the FEA model, residual stress field induced by LSP was analyzed, the fatigue life and position of weak area were predicted with ABAQUS software and MSC.Fatigue code, respectively, and the processing parameters were optimized. The results show that the fatigue life of ZK60 sheet metal by single LSP with one side and both sides increased by 72.9% and 78.5% compared with the untreated sample respectively. The size and depth of compressive residual stress increase with the increment of peening number, but when the peening number gets to a certain value, the residual stress reaches saturation and the fatigue life increase no longer significantly.