Fatigue Life Properties and Anomalous Macroscopic Fatigue Fracture Surfaces of Low Carbon Steel JIS-SM490B in High-Pressure Hydrogen Gas Environment

Tension-compression fatigue tests using smooth specimens of low carbon steel JIS-SM490B were carried out in air and hydrogen gas environment under the pressure of 0.7 and 115 MPa at room temperature. In 0.7 MPa hydrogen gas, fatigue life curve was nearly equivalent to that in air. On the other hand, in 115 MPa hydrogen gas, fatigue life was significantly degraded in the relatively short fatigue life regime (e.g. Nf < 105). To clarify the effect of hydrogen environment on fracture process, fracture surfaces of these specimens were observed. In general, fatigue fracture process of steels with low or moderate strength is macroscopically divided into 3 stages. In the first stage (stage I), fatigue cracks initiate in some crystalline grains. In the second stage (stage II), the cracks propagate stably on a cycle-by-cycle basis. In the final stage (stage III), a tilted fracture surface, shear-lip, is formed by ductile tearing. In SM490B steel, this general fracture process was confirmed in air and 0.7 MPa hydrogen gas. In contrast, in 115 MPa hydrogen gas, there was no tilted portion in the stage III region, and the fracture surface was totally flat. Observation with scanning electron microscope revealed that dimples were formed by ductile tearing in the tilted fracture region in air and 0.7 MPa hydrogen gas. On the other hand, only a quasi-cleavage fracture surface existed in the final fracture region in 115 MPa hydrogen gas. To understand the cause of this peculiar fracture morphology, we conducted elasto-plastic fracture toughness tests in each environment, and investigated the fracture morphology. As a result of fracture toughness tests, crack growth rate in air and 0.7 MPa hydrogen gas was approximately equal to each other, and both the fracture surfaces were covered by dimples. This fracture morphology was in accordance with that of stage III morphology in fatigue specimen tested in air and 0.7 MPa hydrogen gas. However, in 115 MPa hydrogen gas, the crack growth was significantly accelerated, and the whole fracture surface was covered by quasi-cleavage. In this paper, firstly, the similarity of fracture surface between two test methods, i.e. fatigue test and fracture toughness test, is investigated. And then, the formation mechanism of the flat fracture surface is discussed by paying attention to the crack-growth acceleration in high-pressure hydrogen gas.

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X-Ray Residual Stress Measurement on Stress Corrosion Fracture Surfaces

Advances in X-ray Analysis ◽

10.1154/s0376030800019170 ◽

1992 ◽

Vol 36 ◽

pp. 543-549

Author(s):

Masaaki Tsuda ◽

Yukio Hirose ◽

Zenjiro Yajima ◽

Keisuke Tanaka

Keyword(s):

Fracture Toughness ◽

Residual Stress ◽

Fracture Surface ◽

Stress Corrosion ◽

Stress Measurement ◽

High Strength Steels ◽

High Strength ◽

X Ray Diffraction ◽

X Ray ◽

Fracture Surfaces

X-ray fractography is a new method utilizing the X-ray diffraction technique to observe the fracture surface for the analysis of the micromechanisms and mechanics of fracture. X-ray residual stress has been confirmed to be a particularly useful parameter when studying the fracture surfaces of high strength steels. The method has been applied to the fracture surface of fracture toughness and fatigue specimens.

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Analysis on Low Cycle Fatigue Life and Fatigue Fracture Surface Morphology of TC25 Titanium Alloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.697.652 ◽

2016 ◽

Vol 697 ◽

pp. 652-657

Author(s):

Rong Guo Zhao ◽

Yi Yan ◽

Yong Zhou Jiang ◽

Xi Yan Luo ◽

Qi Bang Li ◽

...

Keyword(s):

Titanium Alloy ◽

Fatigue Crack ◽

Fatigue Life ◽

Fracture Surface ◽

Crack Growth ◽

Fatigue Fracture ◽

Low Cycle Fatigue ◽

Observation System ◽

Cycle Fatigue ◽

Stress Strain

At room temperature, the low cycle fatigue tests for smooth specimens of TC25 titanium alloy under various stress ranges are operated at a CSS280I-20w Electro Hydraulic Servo Universal Testing Machine with a microscopic observation system, and the low cycle fatigue lifetimes are measured. Based upon the analysis of stress-strain hysteresis loop of low cycle fatigue of TC25 titanium alloy, a simplified Manson-Coffin formula is derived according to both the experimental characteristics and the stress-strain constitutive model, the fatigue lifetimes are plotted against stress ranges, and a stress-fatigue life curve for TC25 titanium alloy is obtained by the linear regression analysis method. Finally, the fracture surface morphologies of TC25 specimens are investigated using a JSM-6360 Scanning Electron Microscopy, and the fatigue fracture mechanisms of low cycle fatigue are studied. It shows that the plastic deformations are mainly formed at the accelerated fracture stage, and various shear lips can be observed on the fracture surfaces, which demonstrates that the shear stress results in the final rupture of TC25 titanium alloy. During the fracture of low cycle fatigue, the cleavage nucleation leads to the formation of fatigue crack initiation region, the fatigue crack growth exhibits a mixed transgranular and intergranular crack growth mode, and in the final rupture region, the fracture surface of low cycle fatigue of TC25 titanium alloy appears as a typical semi-brittle fracture mode.

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Research on Rock Fracture Surface Morphology Characterization under Brazilian Test

Abstract and Applied Analysis ◽

10.1155/2014/434898 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Zhigang Feng ◽

Xuezai Pan ◽

Guoxing Dai ◽

Hongguang Liu

Keyword(s):

Fracture Surface ◽

Rock Fracture ◽

Fracture Morphology ◽

Brazilian Test ◽

Variation Method ◽

Fracture Surfaces ◽

Modulus Maximum ◽

Loading Modes ◽

Morphology Characterization ◽

Maximum Method

In order to test the differences in the morphology characterization of rock fracture surfaces under different loading directions and rates, the following three steps are operated. Firstly, using Brazilian test, the Brazilian discs are loaded to fracture under different loading modes. Secondly, each rock fracture surface is scanned with a highly accurate laser profilometer and accordingly the coordinates of three lines on every rock fracture surface and three sections of every line are selected to analyze their fracture morphology characterization. Finally, modulus maximum method of wavelet transform, including a new defined power algorithm and signal to noise ratio, and fractal variation method are used to determine the differences in rock fracture surfaces’ morphology characterization under different loading directions and rates. The result illustrates that both modulus maximum and fractal variation method can detect anisotropy of rock fracture failure. Compared to modulus maximum method, fractal variation method shows stronger sensitivity to the change of loading rates, which is more suitable to differentiate the rock fracture surface’s morphology characterization under different loading modes.

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Effective Stress Intensity Factor in Mode III Crack Growth in Round Shafts

Recent Advances in Mechanics of Solids and Structures ◽

10.1115/imece2003-43478 ◽

2003 ◽

Cited By ~ 1

Author(s):

A. Vaziri ◽

H. Nayeb-Hashemi

Keyword(s):

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Fracture Surface ◽

Crack Growth ◽

Effective Stress ◽

Mode Iii ◽

Mode Iii Crack ◽

Fracture Surfaces ◽

Effective Stress Intensity Factor

Turbine-generator shafts are often subjected to a complex transient torsional loading. Such transient torques may initiate and propagate a circumferential crack in the shafts. Mode III crack growth in turbo-generator shafts often results in a fracture surface morphology resembling a factory roof. The interactions of the mutual fracture surfaces result in a pressure, and a frictional stress field between fracture surfaces when the shaft is subjected to torsion. This interaction reduces the effective Mode III stress intensity factor. The effective stress intensity factor in circumferentially cracked round shafts is evaluated for a wide range of applied torsional loadings by considering a pressure distribution in the mating fracture surfaces. The pressure between fracture surfaces results from climbing the rought surfaces respect to each other. The pressure profile not only depends on the fracture surface roughness (height and width (wavelength) of the peak and valleys), but also depends on the magnitude of the applied Mode III stress intensity factor. The results show that the asperity interactions significantly reduce the effective Mode III stress intensity factor. However, the crack surfaces interaction diminishes beyond a critical applied Mode III stress intensity factor. The critical stress intensity factor depends on the asperities height and wavelength. The results of these analyses are used to find the effective stress intensity factor in various Mode III fatigue crack growth experiments. The results show that Mode III crack growth rate is related to the effective stress intensity factor in a form of the Paris law.

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Mechanical Properties of a New Nitrogen-Strengthened Stainless Steel With Reduced Amount of Ni and Mo in High Pressure Gaseous Hydrogen

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2013-97656 ◽

2013 ◽

Author(s):

Kazuhisa Matsumoto ◽

Shinichi Ohmiya ◽

Hideki Fujii ◽

Masaharu Hatano

Keyword(s):

High Pressure ◽

Stainless Steel ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

High Strength ◽

Hydrogen Gas ◽

Fracture Surfaces ◽

Growth Properties ◽

Pressure Hydrogen

To confirm a compatibility of a newly developed high strength stainless steel “NSSC STH®2” for hydrogen related applications, tensile and fatigue crack growth properties were evaluated in high pressure hydrogen gas up to 90MPa. At temperatures between −40 and 85°C, no conspicuous deterioration of tensile properties including ductility was observed even in 90 MPa hydrogen gas at −40°C while strength of STH®2 was higher than SUS316L. Although a slight drop of reduction of area was recognized in one specimen tested in 90 MPa hydrogen gas at −40°C, caused by the segregation of Mn, Ni and Cu in the laboratory manufactured 15mm-thick plate, it was considerably improved in the large mill products having less segregation. Fatigue crack growth rates of STH®2 in high pressure hydrogen gas were almost the same as that of SUS316L in air. Although fatigue crack growth rate in air was considerably decelerated and lower than that in hydrogen gas at lower ΔK region, this was probably caused by crack closure brought by oxide debris formed on the fracture surfaces near the crack tip by the strong contact of the fracture surfaces after the fatigue crack was propagated. By taking the obtained results into account, it is concluded that NSSC STH®2 has excellent properties in high pressure hydrogen gas in addition to high strength compared with standard JIS SUS316L.

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Fracture Surfaces in 3D Fuse Networks

MRS Proceedings ◽

10.1557/proc-409-377 ◽

1995 ◽

Vol 409 ◽

Author(s):

V. I. Räisänen ◽

M. J. Alava ◽

R. M. Nieminen

Keyword(s):

Fracture Surface ◽

Fracture Process ◽

Energy Surface ◽

Minimum Energy ◽

Quenched Disorder ◽

Nanometer Scale ◽

Directed Percolation ◽

Fracture Surfaces ◽

Final Fracture ◽

Roughness Exponent

We study a 3D random fuse network model with computer simulations. The breaking thresholds are distributed randomly, corresponding to quenched disorder. We find for the roughness exponent of the final fracture surface ζ = 0.47 ± 0.19, which is close both the minimum energy surface value and the directed percolation depinning model value in 2+1 dimensions. It is also similar to results from measurements of fracture surfaces at nanometer scale, and from experiments in which the fracture process occurs slowly as in fatique. The traditional measure of damage, the number of broken bonds grows faster than the area effect (nb ˜ L2.28), with no signs of a trivally brittle regime.

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A frequency dependent embrittling effect of high pressure hydrogen in a 17-4 PH martensitic stainless steel

MATEC Web of Conferences ◽

10.1051/matecconf/201816503005 ◽

2018 ◽

Vol 165 ◽

pp. 03005

Author(s):

Jean-Gabriel Sezgin ◽

Junichiro Yamabe

Keyword(s):

Fatigue Life ◽

Crack Growth ◽

Upper Bound ◽

Stress Amplitude ◽

Tensile Tests ◽

Hydrogen Gas ◽

Relative Reduction ◽

Lower Stress ◽

Acceleration Ratio ◽

Cycle Dependent

The effects of hydrogen on tensile and fatigue-life properties of 17-4PH H1150 steel have been investigated by using a smooth, round-bar specimen for tensile tests and circumferentially-notched specimen for fatigue-life tests. The specimens were precharged by an exposure to 35-100 MPa hydrogen gas at 270°C for 200 h. For the 100 MPa hydrogen exposure, the steel showed a significant degradation in ductility loss, translated by a relative reduction in area, RRA, of 0.31. The fatigue-life test of the present notch specimen (stress concentration factor of 6.6) reflects the fatigue crack growth (FCG) for long cracks. The fatigue limit of the non-charged and H-charged notched specimens, defined by the threshold of non-propagation for long cracks, was not affected by hydrogen. At a higher stress amplitude, the H-charged specimen showed a significant FCG acceleration ratio compared to the non-charged specimen. Although, an upper bound of the FCG acceleration seemed to exist, this ratio was approximately 100. The fracture surface of the H-charged specimen was covered with quasi-cleavage (QC) at a lower stress amplitude and with a mixture of QC and intergranular (IG) facets at higher stress amplitudes. It has been suggested that a cycle-dependent crack growth accompanied by QC occurs at a lower stress amplitude, whereas a mixture of cycle-dependent crack growth (accompanied by QC) and time-dependent crack growth (accompanied by IG) occurs otherwise. This mixture justifies the 100 times FCG acceleration ratio in spite of the existence of the upper bound.

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Fatigue Crack Growth Behavior and Fracture Toughness of EH36 TMCP Steel

Materials ◽

10.3390/ma14216621 ◽

2021 ◽

Vol 14 (21) ◽

pp. 6621

Author(s):

Qingyan Zhu ◽

Peng Zhang ◽

Xingdong Peng ◽

Ling Yan ◽

Guanglong Li

Keyword(s):

Fracture Toughness ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Propagation ◽

Crack Growth ◽

Fatigue Crack Propagation ◽

Growth Behavior ◽

Crack Growth Behavior ◽

Fatigue Crack Growth Behavior ◽

Fracture Surfaces

The fatigue crack growth behavior and fracture toughness of EH36 thermo-mechanical control process (TMCP) steel were investigated by fatigue crack growth rate testing and fracture toughness testing at room temperature. Scanning electron microscopy was used to observe the fracture characteristics of fatigue crack propagation and fracture toughness. The results indicated that the microstructure of EH36 steel is composed of ferrite and pearlite with a small amount of texture. The Paris formula was obtained based on the experimental data, and the value of fracture toughness for EH36 steel was also calculated using the J-integral method. The observations conducted on fatigue fracture surfaces showed that there were a lot of striations, secondary cracks and tearing ridges in the fatigue crack propagation region. Additionally, there existed many dimples on the fracture surfaces of the fracture toughness specimens, which indicated that the crack was propagated through the mechanism of micro-void growth/coalescence. Based on the micromechanical model, the relationship between the micro-fracture surface morphology and the fracture toughness of EH36 steel was established.

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Mixed Mode I/II Fracture and Fatigue Crack Growth Along 63Sn-37Pb Solder/Brass Interface

10.1115/imece2000-1258 ◽

2000 ◽

Author(s):

H. Nayeb-Hashemi ◽

Pinghu Yang

Keyword(s):

Fracture Toughness ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Fracture Surface ◽

Crack Growth ◽

Mixed Mode ◽

Mode I ◽

Mode Ii ◽

Mixed Mode Loading ◽

Solder Layer

Abstract Solder joints are extensively used in electronic packaging. They provide critical electrical and mechanical connections. Single edge notched sandwich specimens, which were made of two blocks of brass joined with a 63Sn-37Pb solder layer, were prepared for fatigue and fracture study of the joint under mixed mode loading. Mode I and mixed mode I/II fracture toughness, fatigue crack thresholds, and fatigue crack growth rates (FCGR) were measured at room temperature using a four point bending test setup. It was found that the fracture toughness of the joint increased and FCGR decreased upon the introduction of mode II component. The interface fracture toughness was higher than that of reported for pure solder. The data of FCGR correlated well with the power law relation of da / dN = C* (ΔG)m. It was also observed that both fracture toughness and FCGR were a function of thickness of solder layer. When the solder layer thickness increased from 0.1mm to 1.0mm, the fracture toughness decreased substantially and FCGR increased slightly. For mode I loading, fatigue crack propagated inside the solder layer. However, for mixed mode loading, once a crack initiated, it changed its direction toward the interface and then propagated along the interface. These observations were related to local mode I and mode II stress fields. Fracture surface showed sign of rubbing under mixed mode loading with elongated cavities at the crack tip. However, under mode I loading, fracture surface was covered with equi-ax voids.

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