Fatigue Properties Of Aluminum Alloy Research Articles

Enhancing plain fatigue strength in aluminum alloys through shot peening: Experimental investigations and a strain energy density interpretation

This study addresses the complex interplay of shot peening-induced effects on the fatigue strength of high-strength aluminum alloys. The inherent poor fatigue properties of aluminum alloys, particularly exacerbated in components manufactured through additive processes, pose significant challenges. Shot peening, a recognized surface treatment, proves effective in enhancing fatigue resistance through mechanisms such as compressive residual stresses, work hardening, and microstructural changes. However, optimizing shot peening and developing accurate fatigue prediction models remain challenging due to the intricate and unclear contributions of the individual mechanisms. In this investigation, five distinct shot peening treatments were employed to emphasize specific effects. Experimental results, analyzed through a strain energy density approach, shed light on the crucial role of compressive residual stresses in maximizing fatigue strength. This comprehensive exploration contributes with valuable insights for designing shot peening treatments to optimize the fatigue performance of high-strength aluminum alloys.

The influence of the structure on the fatigue properties of aluminium alloys for the casting

The article will be focused on monitoring the influence of the structure on the fatigue properties of Al-Mg cast alloy. As an experimental material were used aluminium alloys EN AC 51200 and EN AC 51500, supplied in a cast state without a heat treatment, which were produced by the continuous casting method. These alloys were selected on the basis of the chemical composition, where the content of most alloying elements is comparable. Fatigue properties of aluminium alloys were tested by three-point bending cyclic loading. The fracture surface of the testing sample was examined using scanning electron microscopy (SEM), where samples were observed on various stages of the fatigue process, their characteristics and differences of fracture surfaces.

The Structure of the Aluminium Alloy and Its Influence on the Fatigue Properties

The article will be focused on monitoring the influence of the structure on the fatigue properties of aluminium alloys for the casting of type Al-Mg, especially EN AC 51200 and EN AC 51500. These alloys were selected on the basis of the chemical composition, where the content of most alloying elements is comparable, only in the case of the concentration of magnesium are these alloys significantly different. Fatigue properties of aluminium alloys were tested by three-point bending cyclic loading. The fracture surface of the testing sample was examined using scanning electron microscopy (SEM), where samples were observed on various stages of the fatigue process, their characteristics and differences of fracture surfaces.

High-cycles Fatigue of Different Casted Secondary Aluminium Alloy

Nowadays manufacturers currently use about 35 % of secondary aluminium and about 65 % of primary aluminium to meet their needs. The production of secondary Al alloys have significant advantages. Most important is saving of natural resources with a consequent material cost reduction and a considerable energy-saving associated to reduction in pollution and CO2 emissions. The positive fact is that secondary Al alloys has comparable mechanical properties with primary aluminium alloys. Therefore it is necessary to study properties such alloys especially those which are used for transport industry in order to keeping the quality of casting. One of the major properties of casting for transport industry are fatigue properties. Research point to the fact that more than 90 % of broken engineering components are fractures caused by fatigue of used material. Extremely dangerous are fatigue fractures in transport, for example rails, tire parts, plane wings and hulls of ships, because these are usually connected with human casualties. Due to this fact were studied fatigue properties of aluminium alloys used especially for automotive castings - AlSi9Cu3. The great object was influence of casting to the different mould (sand and metallic) without modification, heat treatments or grain refinement of experimental material to fatigue resistance of the casting. This work shows differences between materials properties which were casted into the different mould.

The Influence of the Structure on the Fatigue Properties of Al-Mg Cast Alloy

AbstractThe article will be focused on monitoring the influence of the structure on the fatigue properties of aluminium alloys for the casting of type Al-Mg. As an experimental material were used aluminium alloys EN AC 51200 and EN AC 51500, supplied in a cast state without a heat treatment. They were produced by the continuous casting method. These alloys were selected on the basis of the chemical composition, where the content of most alloying elements is comparable, only in the case of the concentration of magnesium are these alloys significantly different. Fatigue properties of aluminium alloys were tested by three-point bending cyclic loading. The fracture surface of the testing sample was examined using scanning electron microscopy (SEM), where samples were observed on various stages of the fatigue process, their characteristics and differences of fracture surfaces.

Enhancement of fatigue life of aluminum alloy affected by the density of pulsed electric current

We investigate the effect of pulsed electric current on fatigue-crack growth and the fatigue properties of aluminum alloy (A6061-T6) at current densities of 0–150A/mm2. The fatigue life of most of the treated specimens increases substantially when compared with that of untreated specimens. SEM imaging of the treated specimens shows local melting on the fracture surfaces. To clarify the effect of local melting on fatigue-crack propagation, we examine crack propagation utilizing the plastic replication method. We find that the delay of crack propagation is attributable to the crack-shielding effect arising from current-induced local melting.

Strengthening Effect Analysis of Laser Shock Processing on Aluminum Alloy Welded Joint Process

High-strength aluminum alloy is one of the commonly used materials of pressure vessels. And it has the significant advantages of light-weight and cost-effective. But the strength of welded aluminum alloy greatly decreased. The welding line and heat-affected zone became high-risk area on pressure vessel. At present, it is difficult to improve the welding process, thus improving the microstructure and stress state of welded joints become the main means to improve the fatigue properties and extend the service time of aluminum pressure vessels. As a new treatment process after welding, the process parameters of laser shock processing (LSP) can be precisely controlled, and the process is non-contact. It can be adapted to deal with macro and micro scale aluminum pressure vessels, so it has broad prospects for engineering applications. Based on the introduction of principle and features of LSP welded joint process, the estimation model of laser-induced surface residual stress is analyzed. The safety lives of welded joint specimens with and without LSP are estimated by making low cycle tensile fatigue test. The effect of LSP on fatigue properties of aluminum alloy welded joint is analyzed. The fatigue fracture mechanisms of these specimens with and without LSP are studied by surface integrity and fracture surface testing. The result showed that the safety lives of these specimens with LSP are increased significantly. At the same time, Compressive residual stress and dense surface layer are induced at the surface of welded joints by LSP. After summarizing the research status about fatigue properties of aluminum alloy welded joint by LSP, the problems existing in current research of LSP welded joint process are pointed out. Finally, expectations of future studies on LSP welded joint process are brought forward.

Proportional monitoring of the acoustic emission in crypto-conditions

The work is aimed at studying corrosion and fatigue properties of aluminum alloys by means of acoustic emission (AE). During material degradation are acoustic events scanned and evaluated. The main objective of the article is a description of behavior of aluminum alloys degraded in specific conditions and critical degradation stages determination. The first part of the article describes controlled degradation of the material in the crypto–conditions. The acoustic emission method is used for process analyzing. This part contains the AE signals assessment and comparing aluminium alloy to steel. Then the specimens are loaded on high-cyclic loading apparatus for fatigue life monitoring. Also, the synergy of fatigue and corrosion processes is taken into account.The aim is the description of fatigue properties for aluminum alloys that have already been corrosion-degraded. Attention is also focused on the structure of fatigue cracks. The main part of the article is aimed at corrosion degradation of aluminium alloys researched in real time by means of AE. The most important benefit of AE detection/recording is that it provides information about the process in real time. Using this measurement system is possible to observe the current status of the machines/devices and to prevent serious accidents.

OS1104 DLC表面改質によるAl合金の高機能化と疲労寿命の改善

OS1104 DLC表面改質によるAl合金の高機能化と疲労寿命の改善

G040012 水素マイクロプリント法を用いた7075アルミニウム合金の疲労変形における水素放出の可視化

To improve tank safety and promote the application of aluminum alloys to high-compression hydrogen gas tank liners, it is important to clarify the fatigue properties of aluminum alloys as affected by atmospheric hydrogen. In this study, the effect of fatigue frequency and maximum applied stress on hydrogen evolution in 7075 aluminum alloy was studied by means of a hydrogen microprint technique (HMT). In fatigue deformation, accumulations of hydrogen were observed in the interface between a second phase inclusion (such as an Al_7Cu_2Fe phase) and the matrix. Hydrogen accumulations were also observed within the Al_7Cu_2Fe phase. The amount of hydrogen accumulation increased with decreasing fatigue test frequency. This shows that under elastic fatigue deformation, hydrogen diffusion is influenced by deformation rate. Hydrogen accumulation increased with increasing maximum stress, which indicates that hydrogen evolution during elastic fatigue deformation is controlled by stress-induced diffusion. Depending on the applied stress condition, stress-induced diffusion acted to shift the hydrogen diffusion route from the Al_7Cu_2Fe phase to the interface between that phase and the matrix. This result indicated that the deformation took place over a time sufficiently long for hydrogen to diffuse through that phase.

PS10 7075アルミニウム合金の疲労変形における水素拡散経路の可視化

To improve tank safety for fuel cell vehicles and promote the application of aluminum alloys to high-compression hydrogen gas tank liners, it is important to clarify the fatigue properties of aluminum alloys as affected by atmospheric hydrogen. In this study, the effect of elastic fatigue deformation on hydrogen diffusion for 7075 aluminum alloy was investigated by means of hydrogen microprint technique. The fatigue test was carried out under the various parameters for frequency (10 Hz, 1 Hz, or 0.1 Hz) and applied maximum stress (80%, 60%, or 40% of proof stress (525 MPa for 7075-T6 alloy)). In all fatigue tests, accumulated hydrogen was mainly observed within second phase inclusion such as Al_7Cu_2Fe. This shows that Al_7Cu_2Fe acts as hydrogen diffusion path during elastic fatigue deformation. The amount of hydrogen accumulation increased with decreasing fatigue test frequency, which shows that the hydrogen diffusion is influenced by deformation time. Hydrogen accumulation also increased with increasing maximum stress, which indicates that hydrogen evolution during elastic fatigue deformation is controlled by stress-induced diffusion.

Effects of laser peening treatment without protective coating on axial fatigue property of aluminum alloy

Axial fatigue tests with stress ratio of −1 and 0.1 were conducted in order to investigate effects of laser peening treatment without protective coating (LPwC) on fatigue property such as the fatigue strength and the surface crack behaviors of rolled aluminum alloy A7050-T7451 for aircraft structures. As results, The LPwC treatment was effective for the fatigue strength improvement in fatigue lives regime before 2∼3×106 cycles, but the treatment reduced the strength after the cycles at the both stress ratios conditions. Fatigue cracks initiated at the surface on the higher stress amplitude levels, but the cracks initiated in the internal positions on the lower stress levels. From these results, it is clear that the LPwC treatment could control the crack initiation and propagation behaviors. The fatigue crack propagation property from the pre-crack by the LPwC treatment was evaluated by the stress intensity factor range including the residual stress induced by the LPwC treatment.

激光喷丸强化铝合金疲劳特性的数字化分析

激光喷丸强化铝合金疲劳特性的数字化分析

1008 DLCコーティングによるAl合金のトライボロジー特性と疲労特性の改善(表面改質による機械の高性能化)

1008 DLCコーティングによるAl合金のトライボロジー特性と疲労特性の改善(表面改質による機械の高性能化)

The Improvement of Tribological and Fatigue Properties of Aluminum Alloy coated DLC Hybrid Surface Modification

Aluminum alloy has been used in several kinds of industries against a background of environmental problem and energy saving because aluminum alloy has a lot of advantages ; lightness, recyclability and good corrosion resistance. However, aluminum alloy has poor wear-resistance, so in order to solve this problem, DLC (Diamond Like Carbon) coating which indicates high tribological properties was performed. However, there are some reports which are concerned that coated materials like DLC indicate low fatigue strength compared with substrate only due to high heating history during the coating process. So, in this study, in order to improve wear resistance and to prevent the base material from decrease of fatigue strength, original DLC coating was suggested ; (i) coating process was performed by using UBMS (Unbalanced Magnetron Sputtering) method, and (ii) inter-layer which was doped Tungsten was formed on the substrate, and on the inter-layer (iii) two kind of DLC coatings were laminated for nano order. Wear tests and fatigue tests were carried out. Aluminum alloy coated DLC indicated very low wear rates, excellent tribological properties. Furthermore, it indicated high fatigue strength compared with substrate only.

Super-Long Life Fatigue Properties of Aluminum Alloy Die-casting Related with Internal or Surface Defects

By the ultrasonic fatigue test for Al-Si-Cu die-casting, the influence of internal or surface defects on super-long life properties was investigated. The results were as follows : (1) When surface defects were the crack starting points, the S-N curve leveled off around 107 cycles. On the other hand when the defects were internal defects, the S-N curve showed continued degradation as Nf increase. (2) When the crack starting point was an internal defect, ODA (Optically Dark Area) was observed around the crack initiation point after 108 cycles. However, ODA was not observed when the compulsory fatigue was applied for no-break sample that was tested over 1010 cycles of Nf. This suggests that the incidence of fatigue crack from the defect point or its progress were not recognized. (3) By using the following formula, which compares the relationship between ΔKCD ∝ (√area) 1/3 and ΔKth∝ (√area) 1/3 based on the √area parameter model, it is possible to explain the breaking or non-breaking phenomenon caused by the casting defect in the super-long life area (over 107 cycles).

The Improvement of Tribological and Fatigue Properties of Aluminum Alloy Coated DLC Hybrid Surface Modification

Aluminum alloy has been used in several kinds of industries against a background of environmental problem and energy saving because aluminum alloy has a lot of advantages ; lightness, recyclability and good corrosion resistance. However, aluminum alloy has poor wear-resistance, so in order to solve this problem, DLC (Diamond Like Carbon) coating which indicates high tribological properties was performed. However, there are some reports which are concerned that coated materials like DLC indicate low fatigue strength compared with substrate only due to high heating history during the coating process. So, in this study, in order to improve wear resistance and to prevent the base material from decrease of fatigue strength, original DLC coating was suggested ; (i) coating process was performed by using UBMS (Unbalanced Magnetron Sputtering) method, and (ii) inter-layer which was doped Tungsten was formed on the substrate, and on the inter-layer (iii) two kind of DLC coatings were laminated for nano order. Wear tests and fatigue tests were carried out. Aluminum alloy coated DLC indicated very low wear rates, excellent tribological properties. Furthermore, it indicated high fatigue strength compared with substrate only.

Optimisation of the fatigue resistance of 2024-T351 aluminium alloys by controlled shot peening—methodology, results and analysis

A methodology dedicated to the optimisation of the fatigue properties of aluminium alloys by controlled shot peening is presented. Selection of the peening conditions is made out of the use of the Design of Experiment and the Effects Neutralisation Model. Both techniques allowed the optimisation both in terms of life and crack growth rates. Experimental determination and further analysis of the residual stress relaxation patterns revealed that at high stress levels, low cycle fatigue, life improvement is predominantly due to slow crack growth rates, while in high cycle fatigue the extension of life is attributed to a prolonged period of crack arrest.

Errata: “New Estimation Method of Fatigue Properties of Aluminum Alloys” [ASME Journal of Engineering Materials and Technology, 2003, Vol. 125, No. 2, pp. 208–214

Errata: “New Estimation Method of Fatigue Properties of Aluminum Alloys” [ASME Journal of Engineering Materials and Technology, 2003, Vol. 125, No. 2, pp. 208–214

A Comparison of the Corrosion Fatigue Properties of Plate Aluminium Alloys for Aerospace Applications

A corrosive environment such as salt water can severely degrade the fatigue properties of aluminium alloys used in aerospace applications. The corrosion fatigue crack growth rate properties of two conventional alloys, that is Al-Zn-Mg-Cu-Zr alloy (7010-T7651) and Al-Cu-Mg alloy (2024–T351) have been compared with the more recently developed Al-Li-Cu-Mg alloy (8090-T8771). Increased growth rates were observed in salt water compared to air for 7010 and 8090 but not for 2024. Comparing the three alloys, the 8090 alloy corrosion fatigue rates were similar to those of 2024 which were considerably less than those for 7010. The increase in crack growth in 8090 due to environment was associated with a decrease in the high level of crack closure observed for tests in air. The susceptibility of an alloy to corrosion fatigue can be summarized using a ‘corrosion fatigue resistance’ index, Rcf