Fatigue Life In Water Research Articles

Environmental Fatigue Behavior of a Z3CN20.09M Stainless Steel in High Temperature Water

The low-cycle fatigue behavior of a Z3CN20.09M austenitic stainless steel was investigated and its fatigue life in high temperature water was compared to that in the air at room temperature. It is found that the fatigue life in water at 300 °C was shorter than that in air, and it decreased with the decreasing strain rate from 0.4% to 0.004%/s. The ductile striations having streamed down features were observed at the strain rate of 0.004%/s, indicating that Z3CN20.09M austenitic stainless steel experienced anodic dissolution. The fatigue life obtained in the present experiment was consistent with that using prediction models.

Fatigue Life of 6061 Aluminium Alloy Welding Samples both in Atmosphere and Water

Abstract 6061-O and 6061-T4 aluminum alloy sheets with 0.04 inch (1.02 mm) nominal thickness are widely used in the aviation industry. After argon arc welding, the sheets were subjected to a solution heat treatment followed by a quenching and tempering treatment (T62 treatment), afterwards fabricated to specimens. The fatigue tests were carried out at 60 Hz, stress ratio of 0.1 both in atmosphere and water at room temperature, and loading direction was perpendicular to welding bead. The fracture morphologies were examined by scanning electron microscopy (SEM). The results show that the fatigue life in water is considerably decreased, and fatigue striation is not so clear compared with that in atmosphere, which might be attributed to the fact that the oxygen content on the fracture surface tested in water after dry treatment is much higher than that in atmosphere.

Effect of Surface Texture and Humidity Environment on High Cycle Fatigue Property of Wrought Magnesium Alloys AZ31 and AZ61

Rotating bending fatigue tests on AZ31 and AZ61 wrought magnesium alloys were carried out in order to investigate the effects of specimen surface texture and the humidity environment of experiment. Specimen surface texture was varied by using an emery paper of a different roughness or by buff polishing to mirrored surface in final finish of specimen surface treatment. The conditions of environment in which fatigue tests were conducted were the laboratory's air, the dry air, the humid air and the water. As a result, the fatigue life of a specimen with a rough surface was shorter than that with a smooth surface. But the fatigue life of a specimen with mirrored surface was shorter than that with a little rougher surface by an emery polishing. It is attributed to that the effect of work-hardened layer on the fatigue life exists. And then the fatigue life is predicted by the √area parameter model in which a depth of surface roughness is regarded as a size of defect. The effect of surface roughness was more apparent in the case that a specimen is polished in the circumferential direction which is parallel to the crack propagation direction compared with the case that a specimen is polished in the axial direction. The fatigue strength in the region of a long fatigue life in water was smaller than that in the other environments; however this feature is not so apparent in the region of the short life. Except for in the water environment, the fatigue life became shorter in the descending order of the dry air, the laboratory's air and the humid air.

Influence of Strain Ratio and Environment on Bending Fatigue Life and Form of Fracture Surface in TiNi Shape-Memory Alloy Wire.

The fatigue properties of a TiNi shape-memory alloy wire were investigated by both a rotating-bending test and a pulsating-bending test. The influence of strain amplitude, strain ratio, frequency and environment upon fatigue life was discussed. The results are summarized as follows. (1) The fatigue curves in the rotating bending and the pulsating bending intersect. In the region of low-cycle fatigue, the slope of the fatigue curve and the number of cycles to failure in rotating-bending are smaller than those in pulsating-bending. (2) The fatigue crack initiates at a certain part on the surface of a wire and grows with the number of cycles, resulting in final rupture. The larger the strain amplitude, the smaller the ratio of a fatigue fracture surface and the higher the average fatigue-crack growth rate. (3) In the pulsating-bending test, the smaller the strain ratio, the shorter the fatigue life. The smaller the strain ratio, the larger the ratio of a fatigue fracture surface and the higher the average fatigue-crack growth rate. (4) In the rotating-bending test, the fatigue life in water and in silicone oil is longer than that in the air.

Fatigue Properties of TiNi Shape Memory Alloy

The rotating-bending fatigue tests on a TiNi shape-memory alloy wire were carried out in air and in water and low-cycle fatigue was investigated. The fatigue life in water shortened with increasing temperature but did not depend on frequency. The temperature of the wire in air increased with increasing frequency and the fatigue life shortened. The fatigue equation was proposed to describe the fatigue life depending on strain amplitude, temperature and frequency. The fatigue life was estimated well by the proposed equation. The shape memory processing temperature did not affect the fatigue life.

Fatigue Properties of TiNi Shape Memory Alloy

The rotating-bending lowcycle fatigue tests on a TiNi shape-memory alloy wire were carried out in air and in water. The fatigue life in water shortened with increasing temperature but did not depend on frequency. The temperature of the wire in air increased with increasing frequency and the fatigue life shortened. The fatigue equation was proposed to describe the fatigue life depending on strain amplitude, temperature and frequency. The fatigue life was estimated well by the proposed equation. The shape memory processing temperature did not affect the fatigue life.

Effects of LWR Coolant Environments on Fatigue Lives of Austenitic Stainless Steels

Fatigue tests have been conducted on Types 304 and 316NG stainless steels to evaluate the effects of various material and loading variables, e.g., steel type, strain rate, dissolved oxygen (DO) in water, and strain range, on the fatigue lives of these steels. The results confirm significant decreases in fatigue life in water. Unlike the situation with ferritic steels, environmental effects on Types 304 and 316NG stainless steel are more pronounced in low-DO than in high-DO water. Experimental results have been compared with estimates of fatigue life based on a statistical model. The formation and growth of fatigue cracks in air and water environments are discussed.

Low-Cycle Fatigue of TiNi Shape Memory Alloy and Formulation of Fatigue Life.

The rotating-bending fatigue tests on a TiNi shape-memory alloy wire were carried out in air and in water, and low cycle fatigue was investigated. The fatigue life in water shortened with increasing temperature but did not depend on frequency. The temperature of the wire in air increased with increasing frequency and the fatigue life shortened. The fatigue equation was proposed to describe the fatigue life depending on strain amplitude, temperature and frequency. The fatigue life was estimated well by the proposed equation. The shape memory processing temperature did not affect the fatigue life.

Cyclic Deformation and Fatigue of a TiNi Shape-Memory Alloy Wire Subjected to Rotating Bending

The cyclic deformation and fatigue of a TiNi shape-memory alloy wire were studied by carrying out rotating-bending fatigue tests at various strain amplitudes, temperatures, and rotational speeds in air and in water. The results were summarized as follows: (1) for strain amplitudes in the rhombohedral-phase transformation region, the fatigue life was longer than 107 cycles and the deformation properties did not change under cyclic deformation; (2) for the strain amplitudes in the martensitic transformation region, the fatigue life was shorter than 105 cycles and the higher the temperature, the shorter was the fatigue life; (3) the rotational speed did not affect the fatigue life in water but a higher rotational speed led to a shorter fatigue life in air.

Cyclic Deformation and Rotating-Bending Fatigue of a TiNi Shape-Memory Alloy Wire.

In order to investigate cyclic deformation and fatigue of a TiNi shape-memory alloy wire, rotating-bending fatigue tests were carried out at various strain amplitudes, temperatures and rotational speeds in air and in water. The results were summarized as follows. (1) If strain amplitude was found in the rhombohedral-phase transformation region, the fatigue life was longer than 107 cycles. The deformation properties did not change under cyclic deformation. (2) If strain amplitude was found in the martensitic transformation region, the fatigue life was shorter than 105 cycles. The higher the temperature, the shorter the fatigue life. (3) The rotational speed did not affect the fatigue life in water. The higher the rotational speed, the shorter the fatigue life in air.