Fatigue Strength Of Aluminum Alloy Research Articles

605 気中キャビテーション噴流によるアルミニウム合金鋳物の疲労強度向上

605 気中キャビテーション噴流によるアルミニウム合金鋳物の疲労強度向上

Effect Of Anodized Coatings On Fatigue Strength In Aluminium Alloy.

In order to mvestigate the effect of anodized film on fatigue strength of aluminum alloy, A2014-T6. repeated tensile fatigue test was conducted in laboratory air under the stress ratio, R. of 0.01 using smooth specimen with anodized film thickness of 3 p m. Fatigue strength of anodized specimen tested under R=0.01 decreased by 18-20 % as compared with that of the untreated one. even though the anodized film did not affect the fatigue behavior under the rotating-bending fatigue test of R = -I. The anodized film is fractured at an early stage of repeated tensile fatigue process. because it is too brittle to accommodate the substrate metal. Many cracks are induced to initiate at the substrate by flaws of the anodized film. It was pointed out through the study that the fatigue strength of anodized aluminum alloy is controlled by the crack initiation behavior in the substrate induced by the rupture of the anodized film, which is related to deformation of the substrate metal during fatigue process.

The Effect of Anodized Coating on Fatigue Strength of Aluminum Alloys.

As a study in a series to investigate the effect of anodized coating on fatigue strength of aluminum alloys, repeated tensile fatigue test was conducted in laboratory air and at room temperature under the stress ratio of 0.01 using smooth plate specimen of A2014-T6 and A6151-T6 with anodized film thickness of 3μm. Fatigue strength of the anodized specimens decreased by 20-30% as compared with those of uncoated one. Decrease of fatigue strength depended on static strength of the tested materials. The fracture of anodized coating film occurred at the critical strain formed by the accumulation of plastic deformation of substrate metal at an early stage of repeated tensile fatigue process and crack was induced in the substrate at the flaw of the anodized film. It was recognized that fatigue life of anodized specimens was quantitatively evaluated by the consideration of cyclic stress-strain response and strain-life fatigue behavior.

316 キャビテーション・ショットレス・ピーニングによるアルミニウム合金鋳物の疲労強度向上(OS1-3 表面改質処理と疲労強度)(OS1 高強度材・表面改質材の疲労と破壊)

316 キャビテーション・ショットレス・ピーニングによるアルミニウム合金鋳物の疲労強度向上(OS1-3 表面改質処理と疲労強度)(OS1 高強度材・表面改質材の疲労と破壊)

K-0709 キャビテーション・ショットレス・ピーニングによる疲労強度向上(S07-3 疲労信頼性の向上(熱処理,加工))(S07 表面改質とその機能特性評価)

Cavitation impacts, which normally cause damage to hydraulic machinery, can be used to improve the fatigue strength of metallic materials in a similar way to shot peening. Cavitation impact enables the surface of a material to be peened without the use of shot, thus it is called cavitation shotless peening. As there are no solid body collisions occurring in this peening process, the roughness of the peened surface should be less than that produced by shot peening. This characteristic makes it suitable for peening. In order to demonstrate the improvement of the fatigue strength of samples peened by cavitation impacts induced by the cavitating jet, a rotating bending fatigue test on specimens with and without peening is reported in this paper. The test materials were aluminum alloy (JIS AC4CH) and silicon manganese steel (JIS SUP7). It was revealed that the improvement of fatigue strength of aluminum alloy was 40% and that of silicon manganese steel was about 14%.

339 アルミニウム合金のフレッティング疲労強度に及ぼすショットピーニングの影饗(OS フレッティング摩耗と疲労)

339 アルミニウム合金のフレッティング疲労強度に及ぼすショットピーニングの影饗(OS フレッティング摩耗と疲労)

High Cycle Fatigue Strength and Fatigue Crack Properties of Semi-Liquid Die Casting Aluminum Alloys.

Rotating bending fatigue tests were carried out on semi-liquid die casting aluminum alloys. Compared with the conventional casting, the semi-liquid die casting could reduce cast defects and porosities of casting aluminum alloys, and could miniatureize structrue size, therefore fatigue life of semi-liquid die casting aluminum alloys were expected to be improved. And fatigue crack initiation sites were alternative of cast defects and eutectic silicon particles. According to crack initiation sites, the crack initiation life varied, and crack propagation property depended on the form and the distribution of eutectic silicon particles. Therefore the fatigue strength of aluminum alloys was higher in turn of the semi-liquid die cast material that cracked from eutectic silicon particles, the same material that cracked from porosity and the conventional die cast material (AC 4CH). As a result, as to aluminum alloys, the fatigue life was estimated from the crack initiation life and the crack propagation life, and obtained fatigue life prediction gave good agreement with the experiment value.

Characteristics of Fatigue Strength on Anodized 2014-T6 Aluminum Alloy.

In order to investigate the effect of anodized film on fatigue strength of aluminum alloy, A2014-T6, repeated tensile fatigue test was conducted in laboratory air under the stress ratio, R, of 0.01 using smooth specimen with anodized film thickness of 3μm. Fatigue strength of anodized specimen tested under R=0.01 decreased by 18∼20% as compared with that of the untreated one, even though the anodized film did not affect the fatigue behavior under the rotating-bending fatigue test of R=-1. The anodized film is fractured at an early stage of repeated tensile fatigue process, because it is too brittle to accommodate the substrate metal. Many cracks are induced to initiate at the substrate by flaws of the anodized film. It was pointed out through the study that the fatigue strength of anodized aluminum alloy is controlled by the crack initiation behavior in the substrate induced by the rupture of the anodized film, which is related to the deformation of substrate metal during fatigue process.

Fatigue Strength of Aluminum Alloys in High-Humidity Environment.

Fatigue strength in high-humidity environment has been studied for aluminum alloys such as a high-strength aluminum alloy (A7075-T6), an annealed alloy (A7575-O) and a corrosion-resistant alloy (A5052-H34). Pits are easily initiated in the early stage at humidity exceeding the critical humidity. The critical humidity is 60 pct RH for high-strength aluminum alloys (A7075-T6 and A7075-O) and 70 pct RH for a corrosion-resistant alloy (A5052-H34). Fatigue strength in a high-humidity environment is reduced markedly for all aluminum alloys and is almost the same as that in ion-exchanged water. Thus, a transition of environmental fatigue strength was found with increasing humidity. The reduction ratio of fatigue strengh for A7075-T6 is higher than that for A7075-O and A5052-H34 due to the initiation of large corrosion pits and a high notch sensitivity. The results were compared with those for structural steels, and it was found that the critical humidity is lower and the reduction ratio higher for aluminum alloys than for structural steels.

Effect of Pre-Strain on Fatigue Strength of Aluminum Alloy 5052.

Effect of Pre-Strain on Fatigue Strength of Aluminum Alloy 5052.

Effect of plasma coatings on the fatigue strength of aluminum alloys

Hot gas spraying reduces the fatigue resistance of specimens of D16A-T alloy by 30% and that of Dlch alloy by 85%.

A Study on Low Cycle Fatigue Strength of Aluminum Alloy A 5083 P-O Welded Joints

A Study on Low Cycle Fatigue Strength of Aluminum Alloy A 5083 P-O Welded Joints

A Study on Low Cycle Fatigue Strength of Aluminum Alloy A 5083 P-O Butt Welded Joints

Low-temperature, low-cycle fatigue strength of aluminum alloy welded joints were investigated, carring out deflection controlled repeated bending fatigue tests at room temperature and at -196°C on the following four materials : 5083-O plate, 5083/5183 butt weldments with and without reinforcement, and Tee-fillet weldments made by MIG welding process.The results showed the fatigue properties at -196°C to be superior to those at room tem..' perature, except for the butt weldment with reinforcement machined off in the fatigue life range less than 100 cycles. The fatigue strength ratio at both temperatures increased with increasing fatigue life up to about the ultimate tensile strength ratio at both temperatures.The strain-basis fatigue strength reduction factor due to the reinforcement of the weld Kf., as difined by the ratio of the fatigue strength of the weldment to that of the 'plate, was found to be essentially the same at both temperatures and to become greater than or equal to the elastic stress concentration factor at the weld toe. The above mentioned factor Kf., was reasonably evaluated by Stowell's equation.From these observations it is concluded that the application of the fatigue strength at'room temperature as an allowable stress in the fatigue design of LNG tanks will be on the conservative side.

Effect of heat treatment on the low-cycle fatigue strength of aluminum alloy 01420

Isothermal hardening improves the ductility and increases the static fatigue strength of alloy 01420 by 9–12%.

Effect of Tensile Prestrain on Fatigue Strength of Aluminum Alloy in High Cycle Fatigue

The effect of tensile prestrain on rotating bending fatigue strength of B51-S aluminum alloy in the solution treated and precipitation hardened condition, has been studied at fatigue life in the range of 5 × 104 to 106 cycles. The fatigue strength decreases when the tensile prestrain is 1.5 percent. At a higher prestrain of 3 to 4 percent, fatigue strength is close to that of virgin material. The cyclic stress-strain curves for virgin and prestrained materials are linear. There is no perceptible strain hardening/strain softening of the material under fatigue loading. The cyclic Young’s modulus is about 4 percent lower than the static modulus irrespective of the material condition. The relative disposition of static bending stress-strain curves in the inelastic region for virgin and prestrained materials shows qualitatively the relative disposition of the corresponding S-N curves.

On the P-S-N diagrams of A5083-0 and A7N01-T6 alloys

As a part of study on data scattering of fatigue strength of aluminum alloys, the P-S-N diagrams of the notched and unnotched specimens of A5083-0 and A7N01-T6 (Al-Zn-Mg) alloys were obtained.(1) The fatigue strength of th unnotched 5083-0 alloy is 15.22kg/mm2 and 14.73kg/mm2 for 50% and 90% survivors at 107 cycles, respectively, while those of the A7N01-T6 alloy are 18.28kg/mm2 and 17.75kg/mm2. The notched A5083-0 alloy specimens with the stress-concentration factor of 3.0 have the fatigue strength of 6.28kg/mm2 for 50% survivors and of 5.77kg/mm2 for 90% survivors. The notched A7N01-T6 alloy specirnens with the similar shape have the fatigue strength of 11.38kg/mm2 and 11.02kg/mm2 for the corresponding cases.(2) The P-N line shows a linearelation on the log-normal probability representation. However, when the stress level is close to the fatigue strength at 107 cycles, the P-N curves are composecl of two straight lines. This suggests that the fracture mechanism at the low stress level is different from that at the high stress level.(3) The fatigue strength, obtained by the staircase method, at 107 cycles reasonably agrees with that calculated from the P-S-N diagram under the assumption of the straight P-N line. However, the strength of 10% survivors, obtained from the P-S-N diagram, lies in the dangerous area.

The Effect of Superimposed Stress of Higher Frequency on the Fatigue Strength of Aluminum Alloy

This is the report of the study that was made of the behavior of fatigue strength of aluminum alloy 7075-T6 under a composite stress consisting of rotating bending stress and superimposed stress of higher frequency. The rotating bending stress is denoted by primary stress σ1 and the superimposed stress, by secondary stress σ2. The frequency ratio of the secondary stress to the primary stress is selected to about 12.Main conclusions are as follows. It was observed that the fatigue strength only depended on the frequency ratio of the primary and secondary stresses, but independent of the values of respective frequencies. The effect of the magnitude of secondary stress on the fatigue life was more or less depending on the magnitude of maximum stress σmax (=σ1+σ2). Let the σmax be higher than 1.5σw (σw; endurance limit), the fatigue life was observed to fall when σ2/σmax which is the ratio of the secondary stress to the maximum stress was more than 0.4, but not to fall when the σ2/σmax was less than 0.4. On the other hand, let the σmax be lower than 1.5σw, the fall rate of the fatigue life was slight in proportion to the decrease of maximum stress. In conclusion a convenient method of estimating the fatigue strength under composite stress is proposed.

Effect of corrosive and surface-active media on the fatigue strength of aluminum alloys

1. Analysis of fatigue tests on alloys D16 and V95 exposed to corrosive and surface-active media indicates that these media (especially the corrosive) do affect the fatigue strength of the materials in question. The degree of influence depends on the aggressiveness of the media and the test base. Thus, for example, in testing D16 and V95 in ordinary water, the endurance limit for P=0.5% falls by 30–46% as compared with that obtained in air. On testing these materials in a more aggressive medium, 3% NaCl solution, the limit falls by 4–5 times. 2. Different alloys behave differently when the aggressiveness of the medium changes. For example, in ordinary water, the fatigue strength of V95 falls more than that of D16, but in 3% NaCl solution the reverse is true. 3. Reducing the failure probability leads to an increase in the effect of the medium on the fatigue strength of the material. 4. The action of corrosive and surface-active media results in a very considerable shortening of the life measured in cycles. At stress levels close to the arbitrary endurance limit in air, when P=0.5% the life in cycles is reduced by a factor of several tens for the materials studied. This loss of endurance is an extremely important factor in determining the service life of aircraft on the basis of accumulated fatigue damage over a wide range of loadings with respect to both amplitude and frequency.

Effects of prior static and dynamic stresses on the fatigue strength of aluminium alloys

Effects of prior static and dynamic stresses on the fatigue strength of aluminium alloys