Query: stainless steel fatigue 304

title: EXPERIMENTAL STUDY OF 304 STAINLESS STEEL FATIGUE LIFE CONSIDERING MATERIAL PRE STRAIN HARDENING EFFECT
abstract: 304 stainless steel( 304 SS) strain hardening pressure vessels are widely used to store and transport liquefied gas. It is important to investigate the fatigue properties of strain hardening pressure vessels. In this paper,low cycle fatigue tests under strain controlled of 304 SS pre strain hardening materials are performed. In the test,the pre strain are 10% and 15%,and the total strain amplitudes range from 0. 3 to 0. 7% According to the test results,the S N curves of pre strain hardening material are obtained,and then compared with the design curves in ASME BPVC VIII 2 code. It can be found that the designed fatigue life can be improved when the equipments are evaluated with the pre strain hardening fatigue life design curve.

title: Improvement of AISI 304 austenitic stainless steel low cycle fatigue life by initial and intermittent deep rolling
abstract: In the current study, deep rolling treatment was applied to enhance low cycle fatigue behavior of the AISI 304 stainless steel. Desirability function approach was applied to determine the process parameters offering the optimal surface roughness and hardness as these surface characteristics are supposed to control the fatigue cracks initiation and growth. The enhancement of the low cycle fatigue behavior was investigated using strain controlled fatigue tests applied to machined and deep rolled specimens associated to experimental evaluation of surface topography, microhardness, and residual stress. Findings of this work show that an increase of the fatigue lifetime of the AISI 304 components can be achieved by the application of deep rolling to machined surfaces. Moreover, the application of an intermittent deep rolling leads to a significant extension of service life especially when it is performed at low strain amplitudes. The improvement of the residual lifetime of deep rolled components is explained based on evaluations of the surface texture changes, residual stresses, cold work hardening, and strain induced martensite transformation.

title: Effect of torsional pre strain on low cycle fatigue performance of 304 stainless steel
abstract: Uniaxial tensile tests and low cycle fatigue tests were performed on 304 stainless steel treated with different torsional pre strains. The relationship between torsional pre strain and mechanical properties is established. Furthermore, the changes in the amount of martensite phase transitions are measured during low cycle fatigue tests and after specimen fracture are observed. This is mainly because martensitic transformation is a frequent phenomenon during plastic deformation, which is closely related to the mechanical properties. In this study, it is found that torsional pre strain increases yield strength and reduces elongation. The ductility of 304 stainless steel decreases with the increase of torsional pre strain, while its fatigue life does not. As the amplitude of torsional pre strain increases, the fatigue life of the material changes in s type. In particular, the fatigue life increases when the torsional pre strain is between 5% and 8% From the analysis of the microcosmic distribution of the martensite, it is found that the fatigue life is affected by the combined action of martensite transformation and ductility. The test results suggest that it should skip the relatively dangerous small strain area when improving mechanical properties of 304 stainless steel by way of changing shear pre strain.

title: Young's modulus and fatigue investigation of aluminum nitride films deposited on 304 stainless steel foils using micro fabricated cantilevers
abstract: Aluminum nitride based (AlN based) piezoelectric vibration energy harvesters (PVEHs) have been received much attention in the power generation for the device in microelectromechanical systems (MEMS) During the long time vibration, PVEHs are suffering cyclically dynamic stress. This may result in the defect of the materials, and finally cause the failure of the device. To achieve a reliable design of the device that can work for a long time without failure, the investigation on the mechanical properties of Young's modulus and fatigue were conducted for AlN films deposited on 304 stainless steel (SUS 304) foils in this study. Two kinds of materials were tested, SUS 304 foils with a thickness of 50 mm (SUS 304 (50 mm) and a composite material of AlN films deposited on both sides of SUS 304 foils (AlN (1 mm) SUS 304 (50 mm) AlN (1 mm) structure) The samples were micro fabricated to cantilevers. Young's modulus was measured by the micro cantilever resonance method. The resonant bending fatigue testing method was used to investigate the fatigue properties of the materials. The displacement amplitude of the samples was recorded during the tests. A new criterion by using the change of amplitude versus number of cycles was proposed to define the fatigue life. As results, the Young's modulus was 184.9 and 342.9 MPa, for SUS 304 foil and AlN film, respectively. Stress cycle (S N) curves were plotted by using the proposed criterion successfully. The fatigue strength of SUS 304 foils and the material with AlN/ SUS 304/ AlN structure was estimated to be 294 and 327 MPa, respectively. Fatigue failures of stable crack, intrusions and extrusions, and slip bands, appeared on the surface of SUS 304 foils after the long time vibration. No fatigue failure or surface defect was observed on AlN films.

title: Corrosion fatigue behavior of 304 stainless steel notched specimen in high temperature pressurized water
abstract: Fatigue behavior of 304 stainless steel notched specimen was investigated in room temperature (RT) air, 280 degC and 325 degC pressurized water at varying average strain rates. Fatigue life of the notched specimen in RT air is longer than that of the smooth specimen due to the stress gradient on the section of notch root. Fatigue life of the notched specimen in 325 degC water is longer than that in 280 degC water due to the combination of different corrosion rates and dynamic strain aging at different water temperatures.

title: Statistical Modeling of Wire and Arc Additive Manufactured Stainless Steel 304: Microstructure and Fatigue
abstract: Single bead walls were fabricated using stainless steel (SS) 304 wire and arc additive manufacturing (WAAM) The primary objective is to statistically characterize critical material properties of the build to make comparisons with wrought material. The quality of the build is demonstrated by the size distribution and spatial location of porosity in the build. Deviations in the thermal history as a function of the location in the build, especially as the vertical height of the build increases, cause differences in material properties which are statistically investigated. The material behavior and statistical variances along the horizontal direction of the build compared to perpendicular differences in location is significant. Optical microscopy and electron back scatter diffraction are used to estimate statistically key geometric properties of grains. A preliminary investigation for fatigue using the strain life approach has been conducted to evaluate the effect of the build process and the location dependence on life. A generalized Weibull distribution is proposed to model the statistical variability of fatigue life data.

title: Evaluation of fatigue life and fatigue limit of circumferentially notched Type 304 stainless steel in air and hydrogen gas based on crack growth property and cyclic stress strain response
abstract: Fatigue tests were performed using circumferentially notched, round bar specimens with a stress concentration factor, Kt, of 6.6 for Type 304, metastable, austenitic stainless steel. The tests were carried out in ambient air and in 0.7 MPa hydrogen gas at room temperature. In a relatively higher stress amplitude regime (i.e. the amplitude resulting in Nf 105) it appeared that fatigue life did not differ between air and hydrogen gas. It was also confirmed that the fatigue limit appeared not have been degraded in the hydrogen environment though there was a slight difference between the data obtained in two environments. The fatigue life curve and fatigue limit were predicted by assuming that the notch was equivalent to a circumferential crack. Consequently, there was a significant disparity between the prediction and the experimental results. As a result of microscopic observations of the fracture process in combination with elastic plastic finite element analyses, these discrepancies were attributed to (i) complex cyclic plastic deformation behavior under large and small scale yielding conditions within the vicinity of the notch root, (ii) the retardation of crack initiation in the finite life regime, and (iii) the absence of non propagating cracks at the fatigue limit, all of which are typical characteristics of metastable austenitic stainless steel.

title: Fatigue and cyclic deformation behavior of non and boronized austenitic stainless steel AISI 304 at room and elevated temperatures
abstract: A thermochemical surface treatment, the powder packed boronizing process was optimized and then performed on an austenitic stainless steel, AISI 304. Afterwards, boronized specimens were cyclically loaded at ambient and elevated temperatures (350, 550 and 650 degC) Then the results were compared with the behavior in non boronized condition. Nonstatistically evaluated S N curves and cyclic deformation curves were investigated and are discussed. It was found that the boronizing process only improved the high cycle fatigue (HCF) properties of the austenitic stainless steel AISI 304 at room temperature. An endurance limit of about 340 MPa was observed in the boronized condition, whereas a fatigue strength of about 300 MPa was detected for the non boronized condition. However, at elevated temperatures boronizing was not associated with enhanced fatigue performance of this steel.

title: Effects of a' martensite and deformation twin on hydrogen assisted fatigue crack growth in cold/warm rolled type 304 stainless steel
abstract: The effects of a' martensite and deformation twin on hydrogen assisted fatigue crack growth (FCG) were investigated in cold/warm rolled type 304 stainless steel in 5 MPa hydrogen and argon gas atmosphere. The rate of FCG is reduced in argon gas, while greatly enhanced in hydrogen gas after cold rolling. The FCG rates of warm rolled specimens, no matter tested in hydrogen gas or argon gas, are reduced comparing with as received specimens. After cold rolling, a' martensite formed around the grain boundary promotes hydrogen assisted crack initiation and propagation. The deformation twin plays an important role during FCG besides a' martensite after warm rolling, and hydrogen assisted cracking along the twin boundary and slip band can enhance the FCG rate during cycle loading.

title: Observations of fatigue crack behaviour in proton irradiated 304 stainless steel