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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 March 2012

Keiji Houjou and Koji Takahashi

The purpose of this paper is to study the crack‐healing mechanism of ZrO2/SiC composite ceramics which have a high crack‐healing ability at low temperature.

Abstract

Purpose

The purpose of this paper is to study the crack‐healing mechanism of ZrO2/SiC composite ceramics which have a high crack‐healing ability at low temperature.

Design/methodology/approach

The effects of dispersed SiC and the environment on crack‐healing behaviour were investigated. The fatigue strength of crack‐healed specimens was also investigated.

Findings

The main conclusions are that for crack‐healing of ZrO2 ceramics, it is necessary to have both a SiC composite and an oxidative environment; and when ZrO2/SiC composite ceramics are heat‐treated in air, a phase transformation attributable to the SiC composite results in crack‐healing and improvement of fracture toughness and bending strength.

Originality/value

An appropriate heat treatment for ZrO2/SiC composite caused not only crack‐healing but also the improvement of fracture toughness, and created a multiplier effect on crack‐healing, bending strength and fracture toughness.

Details

International Journal of Structural Integrity, vol. 3 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 11 November 2014

Keiji Houjou, Koji Takahashi, Kotoji Ando and Hisanori Abe

– The purpose of this paper is to investigate the effect of peening on the fatigue limit of steels for welded structure with a crack in the weld toe zone.

Abstract

Purpose

The purpose of this paper is to investigate the effect of peening on the fatigue limit of steels for welded structure with a crack in the weld toe zone.

Design/methodology/approach

An artificial semi-circular slit was created in the weld toe, and peening was conducted. Then, bending fatigue tests were carried out.

Findings

First, owing to the shot peening, the maximum slit depths that can be rendered harmless were 1.0 and 1.2 mm in SUS316 and SM490, respectively. Second, during the fatigue test, the fracture of a peened specimen originated outside the slit, which indicated that peening eliminated the effect of the slit on the fatigue limit. Third, the fatigue limit of a slit specimen was improved by the enhanced residual stress distribution and the decreased stress concentration due to plastic deformation at the weld toe.

Originality/value

There are very few studies about which a fatigue crack is rendered harmless by residual compressive stress, as a result the structures could be continued to use. Moreover, the study defining the concept about rendering crack harmless and systematic investigation was not able to be found.

Details

International Journal of Structural Integrity, vol. 5 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 5 March 2010

Keiji Houjou, Kotoji Ando and Koji Takahashi

Zirconia ceramics exhibit high strength and fracture toughness. The purpose of this paper is to research a possibility of crack healing in zirconia ceramics.

Abstract

Purpose

Zirconia ceramics exhibit high strength and fracture toughness. The purpose of this paper is to research a possibility of crack healing in zirconia ceramics.

Design/methodology/approach

ZrO2/SiC composite ceramics are sintered and subjected to three‐point bending. A surface crack of 100 μm in diameter is formed on each specimen. The cracks are healed and the specimens are tested under bending.

Findings

The paper finds that ZrO2/SiC composite ceramic material had a high crack‐healing ability at a considerably low temperature. For example, a crack of 100 μm in diameter is healed even at 600°C.

Research limitations/implications

The paper provides a low temperature healing and a new mechanism of crack healing.

Originality/value

The paper shows the healing temperature and the minimum time required to heal showed a good proportional relation on the Arrhenius plot at temperatures of 600‐800°C. Moreover, the crack healing is caused by SiO2 cristobalite produced during the healing.

Details

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

Keywords

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Article
Publication date: 2 March 2012

Keiji Houjou, Koji Takahashi and Kotoji Ando

The purpose of this paper is to describe the effects of stress ratio (R) on the threshold stress intensity factor range (ΔKth) by applied overload and to conduct an…

Abstract

Purpose

The purpose of this paper is to describe the effects of stress ratio (R) on the threshold stress intensity factor range (ΔKth) by applied overload and to conduct an analytical investigation of the effect of the stress ratio.

Design/methodology/approach

Tensile overload was applied to a compact tension specimen, and fatigue tests were performed at R=0.1 or 0.5.

Findings

The value of ΔKth increased as the tensile overload was increased, and the nominal threshold values were given by the equation ΔNKth,R = C+ DKov, where C represents ΔKth, and D is a proportional constant. Experimental results showed that the value of D showed good agreement with theoretical value.

Originality/value

The paper proposes a new model that arrests crack growth or makes cracks harmless by utilizing the overload effect.

Details

International Journal of Structural Integrity, vol. 3 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 5 March 2010

Yasuaki Hashikura, Koji Takahashi, Yuji Miyazaki, Keiji Houjou and Kotoji Ando

The purpose of this paper is to study the effects of overload on the threshold stress intensity factor range (ΔKth) in SUS316.

Abstract

Purpose

The purpose of this paper is to study the effects of overload on the threshold stress intensity factor range (ΔKth) in SUS316.

Design/methodology/approach

The fatigue tests are carried out to determine the resultant threshold stress intensity factor range (ΔKth). The mechanism of the improvement of ΔKth by the tensile overloading is analyzed using the Dugdale model.

Findings

It is clarified that the value of ΔKth increases as increasing the overloading.

Research limitations/implications

The apparent value of ΔKth of stainless steel can be improved by a tensile overload, the fatigue strength of structural members that have a surface crack can be increased by a tensile overload.

Originality/value

As a result, the reliability and safety of structures, such as energy plants, can also be improved.

Details

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

Keywords

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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

Keywords

Content available
Article
Publication date: 30 August 2011

M.M.I. Hammouda

Abstract

Details

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

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