Fatigue Life Of Aluminum Alloy Research Articles

Overhead conductor heating chamber and temperature effects on the fatigue life of aluminum alloy 6201‐T81 conductors

AbstractThis work investigates the impact of temperature on the fatigue life All Aluminum Alloy Conductors (AAAC) made of 6201‐T81. A heating chamber was developed to simulate thermal effects induced by electric current passage. Wöhler fatigue curves were generated under isothermal conditions at 75 and 150°C and later compared with the one at 20°C. The conductor exhibited similar fatigue life at 20 and 75°C; however, a significant increase of life was observed for tests at 150°C. Hardness tests and failure analysis of wire breakages were carried out on samples extracted from the conductor coil and on artificially aged samples maintained at controlled temperatures. The analyses revealed that at a temperature of 150°C, there is formation of small precipitates of magnesium and silicon within the aluminum matrix, which impeded the propagation of discontinuities, increasing the material's hardness and fatigue resistance.

Fatigue Life Estimation under High Temperature and Variable Loading of AA7001-T6 Using Shot Peening

In this study, the fatigue life of aluminum alloys (7001-T6) was predicted with shot peening at various temperatures. Surface treatment with shot peening steel balls is a mechanism for reducing damage. An experimental investigation was conducted to find the degree of fatigue accumulation for AA7001-T6 under rotational bending loading and stress ratio R = −1. The experiments were conducted at RT (25 ℃), 330 ℃, and SP + 330 ℃ temperatures. A modified damage stress model that considers damage at various load levels was recommended for forecasting the fatigue life under high temperatures. The model and experimental results were compared to determine the most damage (Miner’s rule). The experimental results of the fatigue life indicated that the increased testing temperature reduced the fatigue life. However, using shot peening at high temperatures increased the fatigue life by 8% when loading sequence L-H and 10% when loading sequence H-L. The results showed a satisfactory degree of safety for the present model. Nevertheless, Miner’s model featured two models: one for low–high loading and high-low loading. The results were proper for prolonging fatigue life.

Fretting Fatigue Life Prediction for Aluminum Alloy Based on Particle-Swarm-Optimized Back Propagation Neural Network

Fretting fatigue is a specific fatigue phenomenon. Due to the complex mechanisms and multitude of influencing factors, it is still hard to predict fretting fatigue life accurately, despite there being many works on this topic. This paper developed a particle-swarm-optimized back propagation neural network to predict the fretting fatigue life of aluminum alloys using the test data gathered from the published literature. A commonly used critical plane model, the Smith, Watson, and Topper criterion, was used as a contrast. The analysis result shows that the proposed fretting fatigue life prediction neural network model achieves a higher prediction accuracy compared to the traditional SWT model. Experimental validation demonstrates the effectiveness of the model in improving the accuracy of fretting fatigue life prediction. This research provides a new data-driven methodology for fretting fatigue life prediction.

Cumulative Fatigue Life Estimation Under Combined Shot Peening and Elevated Temperature for AA7001-T6

The fatigue life of aluminum alloys (7001–T6) and shot peening at various temperatures are predicted in this study. Shot peening (SP) steel balls is a surface treatment technique that can help minimize damage. This study set out to conduct an experimental investigation in order to ascertain the amount of damage caused by fatigue buildup for AA7001-T6 under rotating bending loading and a stress ratio R = -1. RT (room temperature), 330 °C, and SP + 330 °C were the temperatures used in the testing. To predict the fatigue life under high temperatures, it was suggested to use a modified damage stress model that had been established to take damage at different load levels into account. To determine the most damage (Miner's rule), the output of the current model was compared to experimental findings and the output from the fatigue damage model. The comparison showed that the current model had a respectable level of safety, whereas the miners' model had two models: one for low-high loading and the other for high-low loading, and the results were suitable for extending fatigue life. Despite the fact that H-L loading has a longer fatigue life (19477) cycles than the experimental (16433 cycles), L-H loading is conservative (Nf is 19477 cycles less than the experimental (24733 cycles) (non-conservative).

New neural network-based algorithm for predicting fatigue life of aluminum alloys in terms of machining parameters

Various classification of aluminum alloys is one of the most common applied materials in transportation industries due to the specific mechanical and material properties. Body of vehicles, including cars, ships, and airplanes, are constantly exposed to different cyclic loads that lead to surface damage and finally, fatigue failure occurs by crack growth. Therefore, the quality of the machined surface has a direct effect on the fatigue life of the products. In this regard, the most important source of surface roughness is the choice of machining parameters. To understand it, turning operations were performed on 2xxx and 7xxx series aluminum alloys considering different values of process parameters. For any series of aluminums, 189 high-cycle fatigue testing specimens were prepared, and experiments were performed by axial tension–compression fatigue test machine in 7 levels of stress (all tests were repeated three times and the mean failure cycles were reported as the fatigue life). Next, an Artificial Neural Network (ANN) based on the Back Propagation (BP) error algorithm was developed to predict fatigue life of Al alloys which are machined with different conditions. To this end, the parameters considered as input variables to the neural network structure include the Yield Strength (YS) and Ultimate Tensile Strength (UTS) to identify the aluminum series, as well as the process parameters such as cutting depth (d), rotational speed (R), and feed speed (V). In addition, the applied cyclic stress (S) to specimen was considered as input. Furthermore, surface roughness (Z) and number of cycles to failure (N) were considered as ANN output. The comparison of the obtained results from ANN predicting with the experimental values indicates that this approach was tuned finely. Eventually, the presented model can be a suitable alternative to perform fatigue tests with high costs and time-consuming.‌‌ Also, the most effective machining parameter on the surface roughness and fatigue limit was reported.

Influence of Biomimetic Laser Shock Peening on the Crack Resistance and Residual Fatigue Life of Aluminum Alloys

Influence of Biomimetic Laser Shock Peening on the Crack Resistance and Residual Fatigue Life of Aluminum Alloys

Actual Marine Atmospheric Pre-Corrosion Fatigue Performance of 7075-T73 Aluminum Alloy

Actual marine atmospheric pre-corrosion behavior and its effect on the fatigue performance of 7075-T73 aluminum alloy were studied by means of marine atmospheric outdoor exposure testing and fatigue testing. The surface and cross-sectional microstructures of aluminum alloy specimens after different numbers of days of exposure were analyzed. Localized pitting, and intergranular and exfoliation corrosion occurred during the outdoor exposure of aluminum alloy specimens in a marine atmosphere. The degree of severity of atmospheric corrosion increased with increasing duration of exposure. The effects of Fe-rich constituent particles (Al23CuFe4) and grain boundary precipitates (MgZn2) on the marine atmospheric corrosion behavior were discussed. In addition, when the exposure time was increased from 0 days to 15 days, the average fatigue life of aluminum alloy specimens decreased dramatically from about 125.16 × 104 cycles to 16.58 × 104 cycles. As the exposure time was further increased to 180 days, the average fatigue life slowly decreased to about 6.21 × 104 cycles. The fatigue fracture characteristics and the effect mechanism of marine atmospheric pre-corrosion on the fatigue life of 7075-T73 aluminum alloy were also analyzed.

The influence of milling induced residual stress on fatigue life of aluminum alloys

The effect of machining strategies on the surface integrity have received minimal consideration as this fluid situation develops, specifically, the machining induced residual stress generated in the material during milling. This study investigates the presence of machining induced residual stress in Aluminum 7075 and its effects on fatigue life. The testing consists of a layer removal process to measure residual stress followed by a three-point bending fatigue test. The study finds that an increase in feed per tooth in combination with a reduction in cutting speed increases compressive residual stress at the surface in the material. The fatigue testing concludes that this increase in compressive stress improves fatigue life with varying effects on long crack and short crack propagation.

Evaluation of Fatigue Characteristics of Aluminum Alloys and Mechanical Components Using Extreme Value Statistics and C-Specimens

In this study, the fatigue characteristics of aluminum alloys and mechanical components were investigated. To evaluate the effect of forging, fatigue specimens with the same chemical compositions were prepared from billets and forged mechanical components. To evaluate the cleanliness of the aluminum alloys, the cross-sectional area of specimens was observed, and the maximum inclusion sizes were obtained using extreme value statistics. Rotary bending fatigue tests were performed, and the fracture surfaces of the specimens were analyzed. The results show that the forging process not only elevated the fatigue strength but also reduced the scatter of the fatigue life of aluminum alloys. The fatigue characteristics of C-specimens were obtained to develop finite-element method (FEM) models. With the intrinsic fatigue properties and strain–life approach, the FEM analysis results agreed well with the test results.

Phenomenological Models and Peculiarities of Evaluating Fatigue Life of Aluminum Alloys Subjected to Dynamic Non-Equilibrium Processes

Physical-mechanical models for predicting the fatigue life of aluminum alloys D16ChATW and 2024-T351 are proposed and tested. Damage accumulation patterns are established for these alloys in the initial state and after dynamic non-equilibrium processes (DNP) of different intensity that occur at maximum cycle stresses σmax from 340 to 440 MPa, cycle asymmetry coefficients R = 0.1 and load frequency f = 110 Hz. The main model parameters are the initial alloy hardness HV and the limiting parameters of scatter of hardness values m. These parameters are evaluated in the process of cyclic loading with fixed maximum stresses of the cycles. Relative values me are also considered. For the alloys in the initial state, the proposed models are shown to be in good agreement with the experimental results. Conversely, structural changes taking place in alloys after DNP complicate the prediction of their fatigue life.

Corrosion mechanism and fatigue behavior of 2A70-T6 aluminum alloy under alternating corrosion and fatigue

PurposeMost supersonic aircraft were manufactured using 2A70 aluminum alloy. The purpose of this paper is to study the corrosion mechanism and fatigue behavior of an aircraft in a semi-industrial atmospheric corrosive environment, alternating effects of corrosion and fatigue were used to simulate the aircraft’s ground parking corrosion and air flight fatigue.Design/methodology/approachFor this purpose, the aluminum alloy samples were subjected to pre-corrosion and alternating corrosion-fatigue experiments. The failure mechanisms of corrosion and corrosion fatigue were analyzed using microscopic characterization methods of electrochemical testing, X-ray diffraction and scanning electron microscopy. Miner’s linear cumulative damage rule was used to predict the fatigue life of aluminum alloy and to obtain its safe fatigue life.FindingsThe results showed that the corrosion damage caused by the corrosive environment was gradually connected by pitting pits to form denudation pits along grain boundaries. The deep excavation of chloride ions and the presence of intergranular copper-rich phases result in severe intergranular corrosion morphology. During cyclic loading, alternating hardening and softening occurred. The stress concentration caused by surface pitting pits and denudation pits initiated fatigue cracks at intergranular corrosion products. At the same time, the initiation of multiple fatigue crack sources was caused by the corrosion environment and the morphology of the transient fracture zone was also changed, but the crack propagation rate was not basically affected. The polarization curve and impedance analysis results showed that the corrosion rate increases first, decreases and then increases. Fatigue failure behavior was directly related to micro characteristics such as corrosion pits and microcracks.Originality/valueIn this research, alternating effects of corrosion and fatigue were used to simulate the aircraft’s ground parking corrosion and air flight fatigue. To study the corrosion mechanism and fatigue behavior of an aircraft in a semi-industrial atmospheric corrosive environment, the Miner’s linear cumulative damage rule was used to predict the fatigue life of aluminum alloy and to obtain its safe fatigue life.

Fatigue Test of 6082 Aluminum Alloy under Random Load with Controlled Kurtosis.

This paper presents the results of experimental tests carried out on an electromagnetic shaker where the excited element was a specimen with additional weight attached to the slip table. The load was random with a different kurtosis parameter value, i.e., it was performed for non-Gaussian loads. The experiment was accompanied by basic fatigue calculations in the frequency domain and their verification with experimental results. A significant decrease in fatigue life was found to take place with an increase in kurtosis and the maintenance of the same standard deviation of the specimen load. The fatigue effect, caused by the deviation from the normal distribution that was described by the kurtosis parameter, on the fatigue life of aluminum alloy 6082 was presented. An analysis revealed the different amplitude probability distributions for the loading signal and the recorded deformation signal. It was concluded that there was a lack of sensitivity of the numerical model to the change in the kurtosis parameter of the distribution of random loads.

Fatigue Life of Aluminum Alloys Based on Shear and Hydrostatic Strain.

The main purpose of this paper is to propose, based on the literature review, a new multiaxial fatigue strain criterion, analogous to the Dang Van stress criterion, considering the maximum amplitude of the shear strain and volumetric strain. The proposed strain criterion was successfully verified by fatigue tests in cyclic bending with torsion of specimens made of 2017A-T4 and 6082-T6 aluminum alloy. The scatter of test results for cyclic bending and the combination of cyclic bending and torsion is included in the scatter of tests for the cyclic torsion of the analyzed materials. Fracture surfaces for respective bending and torsion in the 6082-T6 aluminum test with strain control showed that, in the case of bending, cracks can be observed that develop from the surface of the specimen towards the bending plane. They are inclined from the fatigue crack at an angle of 45° in relation to the crack surface and the remaining cracks come from the static fracture. In the case of torsion, however, a conical fracture at 45° and a static torsion zone can be observed.

Effects of Pouring Temperature Variations on Fatigue Properties of Al-Cu Alloy After Remelting

The aim of this research is to observe the casting temperature variations effects on fatigue properties of Al 2024 with different types of casting temperature. Three different pouring temperatures were carried out 688, 738, 788 °C, and the cast mold was preheated and kept constant at 220°C. The speciment was heat-treated by T6 process in which this method was heat treated in electrical furnace at 500 °C for 2 hours continued by fast quenching into water. Finally, the sample cast was treated by artificial aging method with the temperature at 190 °C. The results show that at 688°C pouring temperature, it has the highest tensile test results than to other variations which is 138.37 MPa, and for the fatigue strength at more than 2x106 cycles is 62.3 MPa. It shows that fatigue life of aluminum alloy 2024 could be improved by T6 heat treatment and artificial aging in which it indicates that the number of the fatigue strength depends on the number of the maximum tensile strength of the material because the increase in the maximum tensile strength will increase the fatigue strength.

Plasma immersion ion implantation and shot peening influence on the fatigue strength of AA 7050-T7451 aluminum alloy

The 7xxx aluminum alloy series is applied in aircraft components that demand high specific mechanical strength and fatigue resistance. The corrosive environment and friction forces imposed on those components reduce the service life. Therefore, anodizing is frequently used to enhance resistance against corrosion and wear. However, anodizing decreases the fatigue life of aluminum alloys. Plasma immersion ion implantation (PIII) is an alternative surface treatment that has been used to improve surface hardness, corrosion resistance and reduce wear damage. The PIII treatment consists of accelerating positive ions towards a sample by applying negative high voltage pulses in plasma. The shot peening (SP) process is a surface treatment that can be used with other surface treatments to improve the fatigue strength. The present work aimed at investigating the fatigue behavior of AA 7050-T451 aluminum alloy treated with SP, PIII, and a combination of both SP and PIII surface treatments. The combination of SP and PIII treatments (SP + PIII) improved the fatigue performance with respect to the base material and was more efficient than PIII in improving the fatigue strength for high-cycle fatigue regime. The fatigue strength improvement is related to the induced compressive residual stresses at the surface layers, which was responsible for delaying the nucleation and early fatigue crack propagation periods. The residual stress at the surface changed from −62 MPa to −130 MPa and −210 MPa for the SP and SP + PIII conditions, respectively. Compared to chromic anodizing, the SP + PIII condition increased the fatigue life in about 4 times at a maximum stress level of 281 MPa. The combination of SP and PIII treatments tested in this work is more advantageous regarding fatigue behavior than chromic anodizing, which reduces the fatigue strength of the material.

A parametric investigation on the fretting fatigue behaviour of heat treated Al 6061-T6 under rotating bending phenomena

ABSTRACT This research investigated the effect of variable fretting parameters on bending fatigue behaviour of heat-treated Al-Mg-Si alloy (Al 6061-T6). Bulk stress, contact pressure, pad geometry, and locations were chosen as variable parameters to measure its consequence on fatigue life. A developed FEM model justified the experimental observation. It observed that, within the lower bulk stress range, fretting action decreases the fatigue life of Aluminium alloy significantly than the plain one. However, this difference almost vanishes at higher-order loading as well as stress in comparison to plain fatigue. Contact pressure and stress distribution along the contact path and non-filleted-edge suggest about the importance of safety design over the fretting zones. The flat on cylinder contacts was found as detrimental at higher-order contact pressure while cylinder on cylinder one reduces notably at low contact pressure. Fuzzy logic, a soft computing technique was implemented to predict the fretting fatigue as well as the effect of pad location from surface graphs. Nevertheless, catastrophic rupture followed the aspect of fretting loading parameter that showed fretting not only affects in quantity but also the quality of the fatigue behaviour of Al 6061-T6.

Study the effect of pre-corrosion on mechanical properties and fatigue life of aluminum alloy 8011

This research paper focus on the consequence of pre corrosion on mechanical properties, fatigue life, microstructure and weight density of Aluminum alloys 8011 because corrosion has emerged biggest reasons for the failure of Aluminum alloy structures. After the pre corrosion of specimens, various tests like tensile test, fatigue test, weight density test and scanning electron microscopy test was performed to compare the mechanical properties and fatigue life of the uncorroded and corroded specimens of Aluminum alloy 8011. Therefore, in this research work influence of the pre corrosion on fatigue life of Aluminum alloy 8011 was done.

An Improved Fish Swarm Algorithm for Neighborhood Rough Set Reduction and its Application

In this paper, an improved fish swarm algorithm for neighborhood rough set reduction (IFSANRSR) is proposed. In IFSANRSR, by introducing an adaptive function to control the visual and step size of artificial fish, the problem of inconsistent convergence speed existed in a traditional artificial fish swarm algorithm (FSA) is avoided. The movement of artificial fish in the swarming and following behavior is improved to shorten the running time of the algorithm. The searching behavior is improved to enhance the local search ability without changing the global searching ability of the algorithm. By introducing the mechanism of extinction and rebirth, the worst solution is eliminated and rebirth takes place after each iteration, which ensures a high level of the overall fitness. The experimental results on three datasets from the University of California at Irvine (UCI) show that the attributes reduction by using the IFSANRSR has higher reduction rate and classification accuracy in most cases. It could better deal with real-valued data attributes and ensure the optimal attribute reduction set to be found. The experimental result on the decision system of aluminum alloy welded joints show that by using the IFSANRSR, the key influencing factors of fatigue life of aluminum alloy welded joints could be obtained, and the weight of each influencing factor could be calculated quantitatively.

Stuy on Fatigue Life of Aluminum Alloy Considering Fretting

To study the influence of fretting on Aluminum Alloy, a global finite element model considering fretting was performed using the commercial code ABAQUS. With which a new model for predicting fretting fatigue life has been presented based on friction work. The rationality and effectiveness of the model were validated according to the contrast of experiment life and predicting life. At last influence factor on fretting fatigue life of aerial aluminum alloy was investigated with the model. The results revealed that fretting fatigue life decreased monotonously with the increasing of normal load and then became constant at higher pressures. At low normal load, fretting fatigue life was found to increase with increase in the pad radius. At high normal load, however, the fretting fatigue life remained almost unchanged with changes in the fretting pad radius. The bulk stress amplitude had the dominant effect on fretting fatigue life. The fretting fatigue life diminished as the bulk stress amplitude increased.

Ultra-low cycle fatigue life of aluminum alloy and its prediction using monotonic tension test results

Ultra-low cycle fatigue (ULCF) life of ductile metal is closely correlated with monotonic tension coupon test results. This paper aims to propose a novel approach to evaluate crack initiation of aluminum alloy under ULCF loading only with monotonic tension coupon test results. ULCF tests on 15 specimens made of aluminum alloy 6061-T6 were conducted, and numerical analyses using a previously proposed cyclic void growth model indicated that the ULCF life of aluminum can be greatly underestimated by the model. A new fracture model based on the concept of different dislocation structures is thus proposed, which classifies damage into kinematic hardening correlated and isotropic hardening correlated. A material constant is employed to consider the relatively low damage induced by the kinematic hardening compared with the isotropic hardening one. The newly proposed fracture model can well simulate the instants of crack initiation for the specimens. A process to evaluate the ULCF life of aluminum alloy based on both monotonic coupon test results and simple numerical analysis is presented.