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Article
Publication date: 30 August 2011

Yu‐Kui Gao

The purpose of this paper is to estimate the bending fatigue strengths/limits of smooth specimens and to quantitatively analyze the effects of residual stresses caused by…

Abstract

Purpose

The purpose of this paper is to estimate the bending fatigue strengths/limits of smooth specimens and to quantitatively analyze the effects of residual stresses caused by surface enhancements.

Design/methodology/approach

Rotating bending and three‐point bending fatigue tests were employed to investigate the effects of surface enhancements including shot peening and laser peening on fatigue strengths/limits of smooth specimens. The fatigue sources were determined by scanning electron microscopy (SEM).

Findings

The two new concepts of surface fatigue strength/limit and subsurface fatigue strength/limit were proposed based on experimental results and the relationship of surface fatigue strength/limit to subsurface fatigue strength/limit was built.

Research limitations/implications

This paper provides the estimation that fatigue strengths/limits of surface‐enhanced specimens is 1.34‐1.42 times that of un‐surface‐strengthened specimens for smooth ones without stress concentration.

Originality/value

Based on the present investigation and analysis, an analysis for fatigue strengths/limits of surface‐enhanced smooth specimens can be used to design engineering components, particularly in the applications of aircraft industry.

Details

International Journal of Structural Integrity, vol. 2 no. 3
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 24 May 2013

Keiji Houjou, Koji Takahashi and Kotoji Ando

The purpose of this paper is to investigate the effect of shot peening (SP) on the fatigue limit of high‐tensile‐strength steel containing a crack in the stress concentration zone.

Abstract

Purpose

The purpose of this paper is to investigate the effect of shot peening (SP) on the fatigue limit of high‐tensile‐strength steel containing a crack in the stress concentration zone.

Design/methodology/approach

An artificial semi‐circular slit was introduced into the bottom of notch, and SP was performed. Bending fatigue tests were then carried out.

Findings

First, the fatigue limits of specimens containing a slit of 0.2 or 0.3 mm in depth were improved up to approximately twice their original values. Second, in the case of shot‐peened specimens with a crack of 0.2 mm in depth, the fractures occurred from outside the slit. Moreover, the specimens recovered to fatigue limits up to those of non‐slit specimens. Finally, the effect of stress concentration (Kt=1.9) on the slit size could be rendered harmless by SP was not found in the fatigue test.

Originality/value

There are very few examples of evaluations of the fatigue limit of materials containing crack‐like surface defects after SP has been performed in the stress concentration zone. The study elucidated the effect of SP on the fatigue limit in such materials, compared with that of a smooth zone.

Details

International Journal of Structural Integrity, vol. 4 no. 2
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 30 April 2020

Xingyang Chen, Linlin Ma, Haoping Xie, Fengting Zhao, Yufeng Ye and Lin Zhang

The purpose of this paper is to present a crack initiation mechanism of the external hydrogen effect on type 304 stainless steel, as well as on fatigue crack propagation…

Abstract

Purpose

The purpose of this paper is to present a crack initiation mechanism of the external hydrogen effect on type 304 stainless steel, as well as on fatigue crack propagation in the presence of hydrogen gas.

Design/methodology/approach

The effects of external hydrogen on hydrogen-assisted crack initiation in type 304 stainless steel were discussed by performing fatigue crack growth rate and fatigue life tests in 5 MPa argon and hydrogen.

Findings

Hydrogen can reduce the incubation period of fatigue crack initiation of smooth fatigue specimens and greatly promote the fatigue crack growth rate during the subsequent fatigue cycle. During the fatigue cycle, hydrogen invades into matrix through the intrusion and extrusion and segregates at the boundaries of α′ martensite and austenite. As the fatigue cycle increased, hydrogen-induced cracks would initiate along the slip bands. The crack initiation progress would greatly accelerate in the presence of hydrogen.

Originality/value

To the best of the authors’ knowledge, this paper is an original work carried out by the authors on the hydrogen environment embrittlement of type 304 stainless steel. The effects of external hydrogen and argon were compared to provide understanding on the hydrogen-assisted crack initiation behaviors during cycle loading.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 3
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 November 2010

F.J.P. Reis, L. Malcher, F.M. Andrade Pires and J.M.A. César de Sá

The purpose of this paper is to perform a numerical assessment of two recently proposed extensions of the Gurson‐Tveegard‐Needleman ductile damage constitutive model under…

Abstract

Purpose

The purpose of this paper is to perform a numerical assessment of two recently proposed extensions of the Gurson‐Tveegard‐Needleman ductile damage constitutive model under low stress triaxiality.

Design/methodology/approach

One of the most widely used ductile damage models is the so‐called Gurson‐Tveegard‐Needleman model, commonly known as GTN model. The GTN model has embedded into its damage formulation the effects of nucleation, growth and coalescence of micro‐voids. However, the GTN model does not include void distortion and inter‐void linking in the damage evolution. To overcome this limitation, some authors have proposed the introduction of different shear mechanisms based on micromechanical grounds or phenomenological assumptions. Two of these constitutive formulations are reviewed in this contribution, numerically implemented within a quasi‐static finite element framework and their results critically appraised.

Findings

Through the analysis of the evolution of internal variables, such as damage and effective plastic strain, obtained by performing a set of numerical tests using a Butterfly specimen, it is possible to conclude that the extended GTN models are in close agreement with experimental evidence.

Research limitations/implications

Even though the results obtained with the modified GTN models have shown improvements, it can also be observed that both shear mechanisms have inherent limitations in the prediction of the location of fracture onset for some specific stress states.

Originality/value

From the results reported, it is possible to identify some shortcomings in the recently proposed extensions of the GTN model and point out the direction of further improvements.

Details

International Journal of Structural Integrity, vol. 1 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

Content available
Article
Publication date: 2 August 2019

Yazhou Mao, Yang Jianxi, Xu Wenjing and Liu Yonggang

The purpose of this paper is to investigate the effect of round pits arrangement patterns on tribological properties of journal bearing. In this paper, the tribological…

Abstract

Purpose

The purpose of this paper is to investigate the effect of round pits arrangement patterns on tribological properties of journal bearing. In this paper, the tribological behaviors of journal bearing with different arrangement patterns under lubrication condition were studied based on M-2000 friction and wear tester.

Design/methodology/approach

The friction and wear of journal bearing contact surface were simulated by ANSYS. The wear mechanism of bearing contact surfaces was investigated by the means of energy dispersive spectrum analysis on the surface morphology and friction and wear status of the journal bearing specimens by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS). Besides, the wearing capacity of the textured bearing was predicted by using the GM (1,1) and Grey–Markov model.

Findings

As the loads increase, the friction coefficient of journal bearing specimens decrease first and then increase slowly. The higher rotation speed, the lower friction coefficient and the faster temperature build-up. The main friction method of the bearing sample is three-body friction. The existence of texture can effectively reduce friction and wear. In many arrangement patterns, the best is 4# bearing with round pits cross-arrangement pattern. Its texturing diameters are 60 µm and 125 µm, and the spacing and depth are 200 µm and 25 µm, respectively. In addition, the Grey–Markov model prediction result is more accurate and fit the experimental value better.

Originality/value

The friction and wear mechanism is helpful for scientific research and engineers to understand the tribological behaviors and engineering applications of textured bearing. The wear capacity of textured bearing is predicted by using the Grey–Markov model, which provides technical help and theoretical guidance for the service life and reliability of textured bearing.

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Article
Publication date: 18 October 2019

Gabriel Ferri, Leonardo Dias, Ruan de Carvalho and Henara Costa

Surface texturing can improve the tribological performance of contacting sliding surfaces under different contact and lubrication conditions, which has been proved both…

Abstract

Purpose

Surface texturing can improve the tribological performance of contacting sliding surfaces under different contact and lubrication conditions, which has been proved both numerically and experimentally. This study aims to suggest a new methodology to evaluate the tribological behavior of textured surfaces using an adapted pendular scratch tester.

Design/methodology/approach

A Charpy-type tester was adapted to meet conditions that are relevant for sliding surfaces. The test rig was used to evaluate low carbon steel textured surfaces produced via maskless electrochemical texturing. The textures were composed of 100 pockets with an average diameter of 200 µm of and variable average depths (1.5, 3.5 and 7 µm). The tests were performed under dry and lubricated conditions for smooth and textured surfaces. The lubricated tests simulated a starved condition by applying a drop of lubricant.

Findings

For starved lubrication, surface texturing reduced the sliding energy when compared with smooth surfaces. This was attributed to the pocket’s ability to provide an additional supply of lubricant, as well as a reduced amount of plastic deformation around the pockets during sliding of the indenter. However, under dry sliding conditions, no significant effect of surface texturing was detected.

Originality/value

A new evaluation methodology was proposed, using single-pass pendular sliding of a spherical indenter to measures the energy absorbed during sliding, which was referred to as sliding energy. The measurements are repeatable and can detect sliding energy differences between smooth and textured surfaces.

Details

Industrial Lubrication and Tribology, vol. 72 no. 9
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 11 March 2014

Jun Yasuda, Koji Takahashi and Hideki Okada

The purpose of this study is to clarify the influence of stress ratio (R) on the effects of shot peening (SP) on the fatigue limit of high-strength steel containing an…

Abstract

Purpose

The purpose of this study is to clarify the influence of stress ratio (R) on the effects of shot peening (SP) on the fatigue limit of high-strength steel containing an artificial small defect.

Design/methodology/approach

SP was subjected on the specimens with a semi-circular slit with a depth of a=0.1, 0.2 and 0.3 mm. Then, bending fatigue tests were carried out under R=0.4.

Findings

The fatigue limits of specimens with a semi-circular slit were improved by SP under R=0.4. The fatigue limits of the SP specimens with a semi-circular slit under a=0.2 mm fractured outside the slit, and they had considerably high fatigue limits equal to specimens without a slit. Therefore, a semi-circular slit with a depth of under a=0.2 mm could be rendered harmless by SP under R=0.4. Compared to the results of R=0, the increasing ratios of fatigue limits under R=0.4 were lower than those under R=0. However, the size of semi-circular slit that could be rendered harmless by SP was same. In addition, it was found that whether the semi-circular slit is rendered harmless or not is decided by the relationship between the stress intensity factor range of semi-circular cracks and the threshold stress intensity factor regardless of stress ratio.

Practical implications

The proposed method can be applied to mechanical parts used in vehicles, aircraft and trains.

Originality/value

This is the first paper to investigate the fatigue limits after SP in materials containing a surface defect under positive stress ratio. In this study, the authors investigated the influence of stress ratio on the effects of SP on the fatigue limit containing a surface defects.

Details

International Journal of Structural Integrity, vol. 5 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 23 August 2013

Keiji Houjou, Koji Takahashi and Kotoji Ando

The purpose of this study was to investigate the effect of overload (bending moment with plastic deformation: Mp) on three point bending specimen at the fatigue limit of…

Abstract

Purpose

The purpose of this study was to investigate the effect of overload (bending moment with plastic deformation: Mp) on three point bending specimen at the fatigue limit of high-tensile-strength steel containing a crack in the stress concentration zone.

Design/methodology/approach

An artificial semi-circular slit was introduced and Mp was applied after which bending fatigue tests were carried out.

Findings

The relationship between the level of Mp and the fatigue limit (σw) was proportional; the fatigue limits of specimens containing 0.2- and 0.3-mm-deep slits are improved by the Mp process as much as twice the original values; the slit size that can be rendered harmless by the Mp process is a=0.05 mm in depth; and all non-propagating cracks appeared around the artificial slit.

Originality/value

Very few studies have been conducted on the fatigue limit of materials containing crack-like surface defects after overload in the stress concentration zone. This study elucidated the effect of Mp on the fatigue limit.

Details

International Journal of Structural Integrity, vol. 4 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 2 August 2019

Fupeng Cheng, Jinglong Cui, Shuai Xu, Hongyu Wang, Pengchao Zhang and Juncai Sun

The purpose of this paper is to improve the surface electrical conductivity and corrosion resistance of AISI 430 stainless steel (430 SS) as bipolar plates for proton…

Abstract

Purpose

The purpose of this paper is to improve the surface electrical conductivity and corrosion resistance of AISI 430 stainless steel (430 SS) as bipolar plates for proton exchange membrane fuel cells (PEMFCs), a protective Nb-modified layer is formed onto stainless steel via the plasma surface diffusion alloying method. The effect of diffusion alloying time on electrochemical behavior and surface conductivity is evaluated.

Design/methodology/approach

In this work, the surface electrical conductivity and corrosion resistance of modified specimen are evaluated by the potentiodynamic and potentionstatic polarization tests. Moreover, the hydrophobicity is also investigated by contact angle measurement.

Findings

The Nb-modified 430 SS treated by 1.5 h (1.5Nb) presented a lower passivation current density, lower interfacial contact resistance and a higher hydrophobicity than other modified specimens. Moreover, the 1.5 Nb specimen presents a smoother surface than other modified specimens after potentionstatic polarization tests.

Originality/value

The effect of diffusion alloying time on electrochemical behavior, surface conductivity and hydrophobicity of modified specimen is evaluated. The probable anti-corrosion mechanism of Nb-modified specimen in simulated acid PEMFC cathode environment is presented.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 1 September 1973

J. Brettle and S. Orman

Introduction The ever increasing demands made on materials by advanced technology has led, in recent years, to a greater awareness of the importance of mechano‐chemical…

Abstract

Introduction The ever increasing demands made on materials by advanced technology has led, in recent years, to a greater awareness of the importance of mechano‐chemical behaviour. These may be defined as the synergistic effect of mechanical forces and chemical reactions on the material. Although possibly interrelated, three classes of mechano‐chemical reactions have been identified as; stress‐corrosion (SCC), corrosion fatigue (CF) and hydrogen embrittlement. SCC has become one of the ‘in’ subjects of corrosion science during the last decade, while the importance of CF has emerged comparatively recently. In a review of the national corrosion and protection scene in 1970, it was revealed that 62 postgraduate research workers, representing 21% of the total effort in the corrosion and protection field, were involved in mechano‐chemical corrosion studies1. The bulk of these were working on SCC. This large research effort has not resulted in a standardisation of test methods nor, despite several attempts, in a unifying theory for SCC2. The newcomer to the field is faced with a bewildering variety of tests of varying complexity and validity. The supporters of each type of test tend to make exaggerated claims particularly when the test they are advocating is the only one which has caused a particular alloy‐environment system to exhibit SCC.

Details

Anti-Corrosion Methods and Materials, vol. 20 no. 9
Type: Research Article
ISSN: 0003-5599

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