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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: 24 August 2012

Koji Takahashi, Hideki Okada and Kotoji Ando

The purpose of this paper is to clarify the effects of shot peening (SP) on the torsional fatigue limit of high‐strength steel specimens containing an artificial small defect.

Abstract

Purpose

The purpose of this paper is to clarify the effects of shot peening (SP) on the torsional fatigue limit of high‐strength steel specimens containing an artificial small defect.

Design/methodology/approach

Specimens containing a drilled hole 0.1‐0.4 mm deep or a semi‐circular slit 0.15 or 0.3 mm deep were subjected to SP. Torsional fatigue tests were then carried out.

Findings

The torsional fatigue limits of specimens containing a drilled hole and those with a semi‐circular slit were increased 25‐64 per cent and 156‐186 per cent by SP, respectively. The torsional fatigue limits of the specimens subjected to SP and containing a drilled hole less than 0.1 mm in depth or a semi‐circular slit less than 0.15 mm in depth were almost equal to those of SP specimens without a defect. Based on these results, it can be concluded that a drilled hole less than 0.1 mm in depth and a semi‐circular slit less than 0.15 mm in depth could be rendered harmless by SP.

Practical implications

The proposed method can be applied to mechanical parts subjected to cyclic torsion, such as coil springs, crank shafts and drive shafts.

Originality/value

This is the first paper to investigate the torsional fatigue limits after SP in materials containing a surface defect. In this paper, the effect of SP on the torsional fatigue limit having a surface defect is investigated.

Details

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

Keywords

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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

Keywords

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Article
Publication date: 30 August 2011

Koji Takahashi, Toshihiko Amano, Kotoji Ando and Fumio Takahashi

The paper's aim is to investigate the effects of shot peening (SP) on the bending fatigue limit of high‐strength steel containing an artificial semi‐circular slit.

Abstract

Purpose

The paper's aim is to investigate the effects of shot peening (SP) on the bending fatigue limit of high‐strength steel containing an artificial semi‐circular slit.

Design/methodology/approach

SP and stress SP (SSP) were conducted on the specimens containing an artificial semi‐circular slit with a depth of a=0.1, 0.2 and 0.3 mm. Then, bending fatigue tests were conducted on the specimens.

Findings

The fatigue limit was improved by SP and SSP. In the case of SP and SSP specimens, the specimens with a semi‐circular slit under a=0.2 mm fractured outside the slit, and they had considerably high fatigue limits. Therefore, a semi‐circular slit with a depth of under a=0.2 mm could be rendered harmless by SP or SSP. It was found that the fatigue limit of specimens with a semi‐circular slit that received SP or SSP was determined by the threshold condition for non‐propagation of fatigue cracks that emanated from outside the slit. 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 range.

Practical implications

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

Originality/value

There are very few examples of evaluations of fatigue limits after SP in materials containing crack‐like surface defects. This study calcifies the effect of SP on the fatigue limit having crack‐like surface defects.

Details

International Journal of Structural Integrity, vol. 2 no. 3
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

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Article
Publication date: 28 July 2020

Govindarajan Narayanan

The purpose of this study is to address the complexity involved in computing the fatigue life of casted structure with porosity effects in aero engine applications. The…

Abstract

Purpose

The purpose of this study is to address the complexity involved in computing the fatigue life of casted structure with porosity effects in aero engine applications. The uncertainty of porosity defects is addressed by introducing probabilistic models.

Design/methodology/approach

One major issue of casted aluminium alloys in the application of aerospace industries is their internal defects such as porosities, which are directly affecting the fatigue life. Since there is huge cost and time effort involved in understanding the effect of fatigue life in terms of the presence of the internal defects, a probabilistic fatigue model approach is applied in order to define the realistic fatigue limit of the casted structures for the known porosity fractions. This paper describes the probabilistic technique to casted structures with measured porosity fractions and its relation to their fatigue life. The predicted fatigue life for various porosity fractions and dendrite arm spacing values is very well matching with the experimentally predicted fatigue data of the casted AS7G06 aluminium alloys with measured internal defects. The probabilistic analysis approach not only predicts the fatigue life limit of the structure but also provides the limit of fatigue life for the known porosity values of any casted aluminium bearing support structure used in aero engines.

Findings

The probabilistic fatigue model for addressing porosity in casting structure is verified with experimental results.

Research limitations/implications

This is grey area in aerospace and automotive industry.

Originality/value

This work is original and not published anywhere else.

Details

International Journal of Structural Integrity, vol. 12 no. 3
Type: Research Article
ISSN: 1757-9864

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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

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Article
Publication date: 1 November 1963

A.D. Hall

THE purpose of this paper is to examine the part that metal fatigue plays in the engineering of the helicopter, and to outline the methods used at present to estimate the…

Abstract

THE purpose of this paper is to examine the part that metal fatigue plays in the engineering of the helicopter, and to outline the methods used at present to estimate the safe fatigue life of the component parts of the helicopter.

Details

Aircraft Engineering and Aerospace Technology, vol. 35 no. 11
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 November 1959

G. Fitzgerald‐Lee

The first example of the use of zinc coatings in the solution of a problem of corrosion fatigue arose when wires for towing paravanes in sea‐water failed after…

Abstract

The first example of the use of zinc coatings in the solution of a problem of corrosion fatigue arose when wires for towing paravanes in sea‐water failed after comparatively short periods of service. These failures were caused by vibrations which set up cyclic stresses in the presence of sea‐water from which the wires were not adequately protected. Later research revealed that the joint effect of repeated stresses and corrosion acting together far exceeds the sum of the two effects taken singly. Not all cases of corrosion fatigue can be dealt with by zinc protection, but most would benefit from such a coating. This article explains the principles of corrosion fatigue, discusses the cathodic protection offered by zinc, and compares results obtained by electroplating, hot‐dip galvanizing, spraying, and painting with heavily zinc‐pigmented paints.

Details

Anti-Corrosion Methods and Materials, vol. 6 no. 11
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 2 January 2020

Zeng Wu, Wei Ma, Hong-xiu Xiao and Jing-kun Zhang

Fastener technology is one of the key technologies of the ballastless track structure, and the spring strip is the key component to realize the fastener function. Based on…

Abstract

Purpose

Fastener technology is one of the key technologies of the ballastless track structure, and the spring strip is the key component to realize the fastener function. Based on the fatigue test of the WJ-7 type fastener of the ballastless track in China, it is concluded that the fatigue damage of an elastic strip is the main reason for the decline of service performance of the fastener. The purpose of this paper is to discuss the fatigue life of the fastener.

Design/methodology/approach

First, a DH3818 static strain tester is used to measure the static strain signal in the elastic strip fatigue test, and then the fatigue limit of the WJ-7 elastic strip is calculated. Finally, the fatigue life of the fastener strip is estimated.

Findings

The findings of the paper are as follows: first, the lowest fatigue life with a survival rate of 99 percent should be taken as a reference for the service times of WJ-7; second, the fatigue life of the modified formula found to be short under the same stress amplitude.

Originality/value

The fatigue test is processed by the authors and the results of elastic strip are obtained based on the test. Meanwhile, the corresponding limit value of the fatigue stress amplitude is calculated based on the tested results.

Details

International Journal of Structural Integrity, vol. 11 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

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