Search results

1 – 10 of over 2000
Article
Publication date: 14 December 2023

Adem Karci, Veysel Erturun, Eşref Çakir and Yakup Çam

This study aims to investigate the fatigue crack propagation behavior of SiC particle-reinforced 2124 Al alloy composites under constant amplitude axial loading at a stress ratio…

Abstract

Purpose

This study aims to investigate the fatigue crack propagation behavior of SiC particle-reinforced 2124 Al alloy composites under constant amplitude axial loading at a stress ratio of R = 0.1. For this purpose, it is performed experiments and comparatively analyze the results by producing 5, 10, 15 Vol.% SiCp-reinforced composites and unreinforced 2124 Al alloy billets with powder metallurgy (PM) production technique.

Design/methodology/approach

With the PM production technique, SiCp-reinforced composite and unreinforced 2124 Al alloy billets were produced at 5%, 10%, 15% volume ratios. After the produced billets were extruded and 5 mm thick plates were formed, tensile and fatigue crack propagation compact tensile (CT) samples were prepared. Optical microscope examinations were carried out to determine the microstructural properties of billet and samples. To determine the SiC particle–matrix interactions due to the composite microstructure, unlike the Al alloy, which affects the crack initiation life and crack propagation rate, detailed scanning electron microscopy (SEM) studies have been carried out.

Findings

Optical microscope examinations for the determination of the microstructural properties of billet and samples showed that although SiC particles were rarely clustered in the Al alloy matrix, they were generally homogeneously dispersed. Fatigue crack propagation rates were determined experimentally. While the highest crack initiation resistance was achieved at 5% SiC volume ratio, the slowest crack propagation rate in the stable crack propagation region was found in the unreinforced 2124 Al alloy. At volume ratios greater than 5%, the number of crack initiation cycles decreases and the propagation rate increases.

Originality/value

As a requirement of damage tolerance design, the fatigue crack propagation rate and fatigue behavior of materials to be used in high-tech vehicles such as aircraft structural parts should be well characterized. Therefore, safer use of these materials in critical structural parts becomes widespread. In this study, besides measuring fatigue crack propagation rates, the mechanisms causing crack acceleration or deceleration were determined by applying detailed SEM examinations.

Details

Aircraft Engineering and Aerospace Technology, vol. 96 no. 2
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 13 October 2022

Xianghong Fan and Yuting He

The flexible eddy current array sensor has the characteristics of lightweight and flexibility, which has a great application prospect in the field of fatigue crack monitoring. But…

50

Abstract

Purpose

The flexible eddy current array sensor has the characteristics of lightweight and flexibility, which has a great application prospect in the field of fatigue crack monitoring. But the exciting layout and feature signal extraction have a great influence on the crack monitoring characteristics of the sensor. This paper aims to propose a method using crack disturbed voltage as sensitivity to characterize crack propagation.

Design/methodology/approach

Flexible eddy current array sensors with reverse and codirectional exciting layout are proposed, and the advantages and disadvantages of three characterization methods based on the change of trans-impedance amplitude, the change of the trans-impedance’s real and imaginary part and the crack disturbed voltage are compared and analyzed by finite element simulation. Finally, the fatigue crack monitoring experiment is carried out.

Findings

The crack disturbed voltage and the change of trans-impedance’s imaginary part can effectively characterize the crack propagation for sensors with different exciting layouts. The codirectional exciting layout sensor has better crack identification sensitivity than the reverse exciting layout sensor, especially the induction coil 2. When the distance between the exciting coil and the induction coil is 0.1, 0.2 and 0.3 mm, it is increased by 372.09%, 295.24% and 231.43%, respectively.

Originality/value

Crack disturbed voltage can effectively characterize the crack propagation for sensors with two different exciting layouts.

Article
Publication date: 1 July 1995

K.S. Kim

A numerical procedure is described for the elastic—plastic finiteelement analysis of crack propagation with branching. Constraint equationsare used to model crack closing and…

Abstract

A numerical procedure is described for the elastic—plastic finite element analysis of crack propagation with branching. Constraint equations are used to model crack closing and sliding. Constraint conditions are imposed by using a penalty method for the self‐similar crack propagation and an elimination method for the off‐axis propagation. The contact condition is examined during plasticity iterations. The use of multiple constraints at the crack branching point to determine the mode of contact is discussed in detail. The method is then applied to (i) the self‐similar crack growth in a single‐edge notch specimen, (ii) the self‐similar propagation followed by interfacial splitting in a center‐cracked 0° composite plate, and (iii) the bifurcation of a crack in a compact tension specimen.

Details

Engineering Computations, vol. 12 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 8 February 2016

Mathias Linz, Franz Walzhofer, Stefan Krenn, Andreas Steiger-Thirsfeld, Johannes Bernardi, Horst Winkelmann and Ewald Badisch

The purpose of this paper is to investigate the driving mechanisms for crack propagation regarding the related microstructures. Cracks in white etching layers have been found at…

Abstract

Purpose

The purpose of this paper is to investigate the driving mechanisms for crack propagation regarding the related microstructures. Cracks in white etching layers have been found at the surface of submerged steel blades subjected to frictional sliding conditions.

Design/methodology/approach

In-situ monitoring revealed a fluctuation between mixed lubrication and hydrodynamic lubrication conditions. One lamella including a crack tip was prepared for transmission electron microscopy (TEM) using focused ion beam milling. Transmission electron microscope analysis was performed with the aim to understand the characteristics of the crack propagation, especially considering the influence of the microstructural configuration (grain refinement, carbides, martensite and ferrite grains).

Findings

The investigations have shown a grain-refined plastically deformed layer (friction martensite with grain sizes of < 100 nm) which influences the propagation direction of cracks introduced at the frictionally stressed surface. Thereby, the crack propagation is dominantly parallel to the margin of the grain-refined martensitic layer at the surface and the base material. Cracks were split into side cracks what mostly appears at present carbides. In this case, the crack propagation might strike through the carbide or separate it from the matrix due to the mechanical misfit.

Originality/value

For obtaining the results of this paper, a very special preparation of tribologically stressed samples was performed. Accordingly, specific findings of the crack propagation behavior under such conditions were achieved and are documented in the presented work. Moreover, the described crack propagation process is a combination of several mechanisms which occur in very limited region underneath the surface and are investigated by high-resolution TEM.

Details

Industrial Lubrication and Tribology, vol. 68 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 March 1967

D. Broek and J. Schijve

Clad 2024‐T3 and 7075‐T6 sheet specimens were loaded at three different load amplitudes and three different mean loads. It turned out that the mean stress had an important…

Abstract

Clad 2024‐T3 and 7075‐T6 sheet specimens were loaded at three different load amplitudes and three different mean loads. It turned out that the mean stress had an important influence on the crack propagation rate. The crack growth rate in the 7075 specimens was three to four times as large as in the 2024 specimens.

Details

Aircraft Engineering and Aerospace Technology, vol. 39 no. 3
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 16 November 2012

Mohammad Hadi Hafezi, N. Nik Abdullah, José F.O. Correia and Abílio M.P. De Jesus

Fatigue crack growth models based on elastic‐plastic stress‐strain histories at the crack tip region and strain‐life damage models have been proposed. The UniGrow model fits this…

Abstract

Purpose

Fatigue crack growth models based on elastic‐plastic stress‐strain histories at the crack tip region and strain‐life damage models have been proposed. The UniGrow model fits this particular class of fatigue crack propagation models. The residual stresses developed at the crack tip play a central role in these models, since they are applied to assess the actual crack driving force. This paper aims to assess the performance of the UniGrow model based on available experimental constant amplitude crack propagation data, derived for several metallic materials from representative Portuguese bridges. It also aims to discuss key issues in fatigue crack growth prediction, using the UniGrow model, in particular the residual stress computation and the suitability of fatigue damage rules.

Design/methodology/approach

The UniGrow model is assessed using data derived by the authors for materials from Portuguese riveted metallic bridges. Strain‐life data, from fatigue tests on smooth specimens, are used to propose a convenient fatigue damage model. Predicted crack growth rates are compared with experimental crack propagation data obtained by authors using fatigue tests on compact tension specimens. Since the UniGrow model is a residual stress‐based propagation model, elastoplastic finite element analysis is proposed for comparison with the analytical approach implemented in the original UniGrow model.

Findings

The use of the Smith‐Watson‐Topper damage parameter overestimates the stress R‐ratio effects on crack propagation rates, mainly if the material shows crack propagation rates with small to moderate sensitivity to stress R‐ratio, which is the case of the materials under investigation in this paper. Alternatively, the application of the Coffin‐Manson damage law leads to consistent fatigue crack growth predictions for the investigated range of positive stress R‐ratios. The stress R‐ratios effects may be solely attributed to the residual stresses. Their estimation, using an analytical approach, may lead to inconsistent results, which is demonstrated by an alternative elastoplastic finite element analysis.

Originality/value

Contributions for more accurate predictions of fatigue crack propagation rates, for several stress ratios, using a strain‐based approach is proposed. This approach is valuable since it may be used to reduce the time consuming and costly fatigue crack propagation tests. Furthermore, the proposed approach shows potential for an unified crack initiation and propagation approach.

Details

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

Keywords

Article
Publication date: 25 May 2012

José A.F.O. Correia, Abilio M.P. de Jesus and Alfonso Fernández‐Canteli

Recently, a new class of fatigue crack growth models based on elastoplastic stress‐strain histories at the crack tip region and strain‐life fatigue damage models have been…

Abstract

Purpose

Recently, a new class of fatigue crack growth models based on elastoplastic stress‐strain histories at the crack tip region and strain‐life fatigue damage models have been proposed. The fatigue crack propagation is understood as a process of continuous crack initializations, over elementary material blocks, which may be governed by strain‐life data of the plain material. The residual stresses developed at the crack tip play a central role in these models, since they are used to assess the actual crack driving force, taking into account mean stresses and loading sequential effects. The UniGrow model fits this particular class of fatigue crack propagation models. The purpose of this paper is to propose an extension of the UniGrow model to derive probabilistic fatigue crack propagation data, in particular the derivation of the P–da/dN–ΔK–R fields.

Design/methodology/approach

An existing deterministic fatigue crack propagation model, based on local strain‐life data is first assessed. In particular, an alternative methodology for residual stress computation is proposed, based on elastoplastic finite element analysis, in order to overcome inconsistencies found in the analytical approximate approaches often used in literature. Then, using probabilistic strain‐life fields, a probabilistic output for the fatigue crack propagation growth rates is generated. A new probabilistic fatigue field is also proposed to take mean stress effects into account, using the Smith‐Watson‐Topper (SWT) damage parameter. The proposed models are assessed using experimental data available for two materials representative from old Portuguese bridges.

Findings

A new method to generate probabilistic fatigue crack propagation rates (P–da/dN–ΔK–R fields) is proposed and verified using puddle iron from old Portuguese bridges, usually characterized by significant scatter in fatigue properties. Also, a new probabilistic fatigue field for plain material is proposed to deal with mean stress effects.

Originality/value

A relation between the P–ε–N and the P–da/dN–ΔK–R fields is firstly proposed in this research. Furthermore, a new PSWTN field is proposed to deal with mean stress effects.

Details

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

Keywords

Article
Publication date: 22 November 2011

Julia Bierbaum and Peter Horst

The purpose of this paper is to present the first results of tests where cracks lie in the tension field of a shear forced aluminium panel. The paper's main focus is on the crack…

Abstract

Purpose

The purpose of this paper is to present the first results of tests where cracks lie in the tension field of a shear forced aluminium panel. The paper's main focus is on the crack propagation behavior and possible 3D‐effects caused by the bending of the plate. A simplified numerical approach is presented to confirm the observed phenomena.

Design/methodology/approach

Experiments have been performed to investigate the influence of buckling on accidental damages. A simplified numerical approach is presented and compared to the experimental results.

Findings

It can be shown that the crack propagates due to buckling of the plate. The principal stress of the neutral axis of the plate has significant influence on the crack propagation.

Originality/value

Investigations of stability problems and damage tolerance behavior of metallic structures have been realized but mainly separately. This paper shows that cracks propagate due to buckling and that both phenomena influence one another considering accidental damages. The paper presents the first experimental and numerical results of cracked aluminium panels subjected to cyclic shear load.

Details

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

Keywords

Article
Publication date: 15 November 2013

Julia Bierbaum and Peter Horst

In former work, test results of cracks in aluminium panels under cyclic shear buckling showed that cracks in the tensile stress field of a buckle propagate. The main influencing…

Abstract

Purpose

In former work, test results of cracks in aluminium panels under cyclic shear buckling showed that cracks in the tensile stress field of a buckle propagate. The main influencing factor for the crack growth rate is the maximum principle stress. A simplified approach for crack propagation analyses based on this finding showed limitations for application on larger cracks because it disregarded the increasing out-of-plane deformation for larger cracks as well as stress redistributions. The purpose of this paper is to improve the results of the simplified approach with the help of finite element method (FEM).

Design/methodology/approach

An approach for crack propagation based on FEM is presented taking into account the mutual interaction of cracks and buckling. The finite element (FE) model, which is described in detail, respects the boundary conditions of the test-set-up. Different initial crack positions, loads and panel thicknesses are analyzed. Results of the stress intensity factors KI calculated by the ABAQUS® FE model provide a function which is used to run a crack propagation analysis based on Forman law.

Findings

The results of the FE-based crack propagation solution are in good agreement with test results and improve the prediction of the simplified approach. It is not restricted in terms of panel thickness, crack position or applied shear load.

Research limitations/implications

Limitations of the FE-based crack propagation solution compared to the experimental results are discussed. These are, the sensitivity of crack propagation analyses to initial crack length and deviations of the experimental settings from the ideal FE model.

Originality/value

The interaction of cracks and buckling in aluminium shells is mainly disregarded both in research and industrial work, but can be of interest considering, accidental damages in fuselage side shells. Cracks propagate under shear load as it was shown in former work. The FE modeling of the tests presented in this paper proves the mutual interactions of crack propagation and buckling deformation.

Details

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

Keywords

Article
Publication date: 12 September 2023

Min Zhan, Yajun Dai, Chang Liu, Xiangyu Wang, Lang Li, Yongjie Liu, Chao He and Qingyuan Wang

The purpose of this paper is to determine (1) the relationship between microstructure and fatigue cracking behavior and (2) effect of rolling on the process of crack initiation…

Abstract

Purpose

The purpose of this paper is to determine (1) the relationship between microstructure and fatigue cracking behavior and (2) effect of rolling on the process of crack initiation and propagation in FeCrAl alloys.

Design/methodology/approach

The qualitative and quantitative fracture studies were performed using scanning electron microscopy and the non-contact optical measurement system (IFMG5).

Findings

The results show that the formation of facets, rough facets and parallel stripes in the crack initiation and early crack propagation zones are closely related to the sensitivity of crack behavior to the microstructure of the material. Besides, the rolling process has a significant influence on the small crack initiation and propagation behavior. Quantitative analysis demonstrates that the size of the stress intensity factor and plastic zone size in the rough zone is associated with the rolling process.

Originality/value

The findings of this study have the potential to enhance the understanding of the microstructural crack formation mechanisms in FeCrAl alloys and shed light on the impact of rolling on the long-term and ultra-long fatigue behavior of these alloys. This new knowledge is vital for improving manufacturing processes and ensuring the safety and reliability of FeCrAl alloys used in nuclear industry applications.

Details

International Journal of Structural Integrity, vol. 14 no. 5
Type: Research Article
ISSN: 1757-9864

Keywords

1 – 10 of over 2000