Fatigue Tests of Axially Loaded Butt Welds up to Very High Cycles

To investigate the influence of shot peening (SP) on very high cycle fatigue (VHCF) performance of 2024-T351, the specimens with three surface conditions were performed under ultrasonic fatigue tests: mechanicallypolished without peening (NP), ceramic shot peening (SP1), steel and glass mixed shot peening (SP2). The roughness, microhardness, residual stress, fractography measurement and scanning electron microscopy (SEM) were applied before fatigue test to characterize the effective layer induced by the peening treatment. For the failed specimens, the fracture surface were analysed using SEM to study the mechanisms of fatigue crack propagation. In addition, the fatigue life curve in ultra-high cycle region continuously decreased in the three series of specimens. However, the experimental results revealed that fatigue strength improvement resulting from shot peening treatment was negligible in very high cycle regime. Furthermore, the stress intensity factor for the surface crack initiation (SCI) and interior crack initiation (ICI) was discussed based on quantitative analysis on the fracture surface. The average values of ΔKfish-eye for NP, SP1 and SP2 specimens are about 2.22, 1.48 and 1.61 MPa · m1/2, respectively.

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Ultrasonic fatigue testing under multiaxial loading conditions on a railway wheel

MATEC Web of Conferences ◽

10.1051/matecconf/201930018003 ◽

2019 ◽

Vol 300 ◽

pp. 18003 ◽

Cited By ~ 1

Author(s):

Pedro R. da Costa ◽

Henrique Soares ◽

Luís Reis ◽

Manuel Freitas

Keyword(s):

Stress Ratio ◽

Fatigue Testing ◽

Fatigue Tests ◽

Cycle Frequency ◽

Railway Wheel ◽

Material Specimen ◽

Hydraulic Machines ◽

Wide Range ◽

Ultrasonic Fatigue ◽

Very High

Ultrasonic fatigue testing is a relative recent fatigue methodology that uses resonant principles for the induction of stress cycles in a specific designed material specimen. This experimental method can apply very high cycle frequency, the most common frequency being 20 kHz, and was created with the main purpose of studying material fatigue life in the Very High Cycle Fatigue regime between 107 and 109 cycles with a higher performance of time and energy wise in comparison to conventional servo-hydraulic machines. In this study an improvement of an already built multiaxial ultrasonic fatigue machine in the Instituto Superior Técnico laboratories was carried out to specific designed specimens and afterwards a fatigue study was made for a material of a worn-out railway wheel. The particular design of the specimen was achieved by numerical and experimental analysis based on previous experiments and components. Thermographic imaging and the application of rosette strain gauges to the main throat of the specimens were conducted in order to validate the improved specimen design and to understand the real induced stresses on the specimen. Afterwards fatigue tests were conducted for several specimens for a wide range of stresses with a stress ratio R=-1 and an axial vs shear stress ratio of around 0.58. Results were analysed and fracture analysis was also carried out.

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Very high cycle fatigue tests of high strength steels S355 J0 and S355 J2

Procedia Structural Integrity ◽

10.1016/j.prostr.2019.08.077 ◽

2019 ◽

Vol 17 ◽

pp. 576-581

Author(s):

Jan Klusák ◽

Stanislav Seitl

Keyword(s):

High Cycle Fatigue ◽

High Strength Steels ◽

High Strength ◽

Fatigue Tests ◽

Cycle Fatigue ◽

Very High Cycle Fatigue ◽

Very High

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Investigations on Fatigue Properties of Die Cast Magnesium Alloy AZ91HP at Very High Cycles

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.353-358.235 ◽

2007 ◽

Vol 353-358 ◽

pp. 235-238

Author(s):

Tang Li ◽

Qing Yuan Wang ◽

Q.F. Dou ◽

Chong Wang ◽

M.R. Sriraman

Keyword(s):

Magnesium Alloy ◽

Fatigue Cracks ◽

Ambient Air ◽

Fatigue Tests ◽

Fatigue Properties ◽

Loading Frequency ◽

Die Cast ◽

Cast Magnesium Alloy ◽

Cast Magnesium ◽

Very High

Very high cycle fatigue (VHCF) properties of high-pressure die cast Magnesium alloy AZ91HP have been investigated. Ultrasonic fatigue tests up to 109 cycles were conducted at the loading frequency of 20 kHz, under R=-1 condition and in ambient air. The experimental results show that specimens fail even after 107 cycles although the scatter seems to be large probably due to the presence of materials defects. However, there seems to be a fatigue limit at about 109 cycles. The fractures contain typical brittle features, with the fatigue cracks seen to initiate from the porosity in the material, either from the surface or beneath.

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Interior-Induced Fracture Mechanism of High Cleanliness Spring Steel (JIS SWOSC-V) in Very High Cycle Regime

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.664.209 ◽

2015 ◽

Vol 664 ◽

pp. 209-218 ◽

Cited By ~ 3

Author(s):

Taku Miura ◽

Takayuki Sakakibara ◽

Takanori Kuno ◽

Akira Ueno ◽

Shoichi Kikuchi ◽

...

Keyword(s):

Fatigue Crack ◽

Fatigue Life ◽

Fatigue Fracture ◽

Fracture Mode ◽

Fracture Mechanism ◽

Fatigue Crack Initiation ◽

Fatigue Tests ◽

Spring Steel ◽

Topographic Analysis ◽

Very High

In order to investigate the interior-induced fatigue crack propagation behavior of high cleanliness valve spring steel (JIS SWOSC-V), rotating bending fatigue tests were performed for various kinds of specimens with different hardness or surface finishings. The harder specimen with higher compressive residual stress showed longer fatigue life. The electrochemical polished specimen pre-treated with shot peening showed almost same fatigue life as the shot-peened specimen in spite of the difference in surface roughness. After fatigue tests, fracture surfaces were observed using a scanning electron microscope (SEM) to evaluate the fatigue fracture mechanism. Most specimens failed in surface-induced fracture mode due to high cleanliness; however, some specimens failed in interior-induced fracture mode in the very high cycle regime. Although non-metallic inclusions were not observed at interior fatigue crack initiation sites, 2 types of significant microstructures (with smooth surface or granular surface) were observed. EBSD analysis, profile analysis and computational simulation using a fracture surface topographic analysis (FRASTA) method were performed to investigate the mechanism of the interior-induced fatigue fracture caused by the microstructure at defect without any inclusion.

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Energy Dissipation in Very High Cycle Fatigue for Polycrystalline Pure Copper and Armco Iron

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.664.33 ◽

2015 ◽

Vol 664 ◽

pp. 33-46

Author(s):

Antoine Blanche ◽

Chong Wang ◽

Ngoc Lam Phung ◽

Nicolas Ranc ◽

Véronique Favier ◽

...

Keyword(s):

High Cycle Fatigue ◽

Armco Iron ◽

Pure Copper ◽

Fatigue Tests ◽

Crystallographic Structure ◽

Loading Frequency ◽

Face Centered Cubic ◽

Cycle Fatigue ◽

Very High Cycle Fatigue ◽

Very High

This paper aims at a deeper understanding of microplastic mechanisms leading to crack initiation in ductile metals in Very High Cycle Fatigue (VHCF). Fatigue tests were conducted using an ultrasonic technique at loading frequency of 20 kHz. The microplastic mechanisms are revealed via observations of slip markings at the specimen surface and self-heating measurements due to intrinsic dissipation. Pure copper and Armco iron (which contains a very low amount of carbon) were investigated. Both are single-phase ductile materials but the crystallographic structure of copper is face-centered cubic while it is body centered cubic for Armco iron. A good correlation was found between slip markings initiation and dissipation for both materials. The dissipation for both materials is of the same order of magnitude but the location, the morphology and the evolution over cycles of slip markings were found different.

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Interior crack initiation during the very-high-cycle fatigue of railway wheel steel under axial loading and rolling contact loading

10.22541/au.163828688.85021276/v1 ◽

2021 ◽

Author(s):

Xiao-Long Liu ◽

Pengcheng Gao ◽

Si Wu ◽

Guanzhen Zhang ◽

Tao Cong

Keyword(s):

Crack Initiation ◽

High Cycle Fatigue ◽

Axial Loading ◽

Fatigue Tests ◽

Rolling Contact ◽

Wheel Steel ◽

Contact Loading ◽

Very High Cycle Fatigue ◽

Very High ◽

Railway Wheel Steel

In this paper, a comparative study of the very-high-cycle fatigue (VHCF) behavior of railway wheel steel under axial loading and rolling contact loading was conducted. Fatigue tests were performed with an ultrasonic fatigue test machine under axial loading, and the fracture surfaces from the fatigue tests and shattered rims taken from the failed railway wheels were observed. The wheel steel under axial loading presents a VHCF behavior with Mode I crack, and that under rolling contact loading is a VHCF behavior with mix Mode II-III crack. For the VHCF behavior with Mode I crack ,surface and interior crack initiation occurred with equal probability at both low and high stress levels and produced a dual linear S-N curve since the value of fatigue limits for the surface and interior crack initiation are close. For the VHCF behavior with mix Mode II-III crack, cracks were initiated from the interior Al O inclusion and the fatigue life was beyond 10 cycles. Fatigue bands were observed on the fracture surface under rolling contact loading. The ferrite nanograins formed due to the stress state of shear plastic strain with a large compressive stress. The formed nanograins were softer than the matrix caused by the redistribution of the carbon.

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On the Fatigue at Very High Frequency — Part I: Theoretical and Variational Formulation

Journal of Engineering Materials and Technology ◽

10.1115/1.2903393 ◽

1991 ◽

Vol 113 (2) ◽

pp. 205-209 ◽

Cited By ~ 3

Author(s):

Kong Xiangan ◽

K. Saanouni ◽

C. Bathias

Keyword(s):

High Frequency ◽

Time Integration ◽

Classical Problem ◽

Fatigue Tests ◽

Evolution Problem ◽

Very High Frequency ◽

Thermoelastic Wave ◽

Frequency Space ◽

Endurance Tests ◽

Very High

This first part of our study is concerned with the theoretical and variational formulations of the problem of elastic cyclic loading at very high frequency (or acoustic fatigue). The problem is treated by using the theory of longitudinal thermoelastic wave motion in a finite medium with and without running crack. Two methods are used to formulate the evolution problem: the first one deals with the use of classical time integration schema, and the second uses the Fourier transformation to solve the evolution problem in the frequency space. Comparison of our results with some closed form solutions of some classical problem is presented. In a second paper this method is used to calculate thermo-mechanical fields in specimens used in ultrasonic fatigue tests (endurance tests and crack growth tests).

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