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Modelling and Characterization of Defects in Metals

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (15 December 2016) | Viewed by 16123

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Special Issue Editor

Prof. Dr. Zengtao Chen

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Guest Editor

Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
Interests: characterization of materials; micromechanics modelling; finite element modelling; functionally graded materials; smart materials and structures; composite materials; multifield behaviour; manufacturing engineering; structural integrity; thermoelasticity; electromagnetic materials
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Special Issue Information

Dear Colleagues,

Catastrophic failures of metallic structures cause huge amounts of human and monetary loss each year. For example, a sudden burst of oil refinery facilities leads to shutdown of the system and millions of dollars of revenue loss, and a single derailment causes a large revenue loss of the railway company, let alone to mention the possible human casualty and environmental impact. In almost every case, a metallic structural failure is directly related to defects in metals. Structural and constituent defects such as materials mismatch, impurities, inclusions, cracks, and deformation localization can greatly limit the mechanical behavior of metals. Investigation of defects in metals helps engineers designing better structures to face various service challenges, such as high strain rates, high/low temperatures and fatigue loading, to name a few. Inspection of structural integrity as a routine practice can be time-consuming and correct information on when and where inspections need to be taken is also essential to minimize the cost of such practice, for example, in the transportation and energy industries. This information heavily relies on how to characterize and model the defects in metals.

This Special Issue of Materials will focus on recent advances in characterization and modelling of defects in metallic structures, such as machinery parts, pressure vessels and piping, rails, automotive and aerospace structures, civil structures, and other engineering structures. The objective of this Special Issue is to provide a platform for materials scientists and mechanical engineers to share their research ideas and showcase their achievements in the general area of modelling and characterization of defects in metals.

Prof. Dr. Zengtao Chen
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Fatigue
Deformation localization
Thermal stresses
Fracture
Damage mechanics
Structural integrity
Experimental characterization
Surface roughness
Wear
Dynamic systems
Corrosion
Erosion
Creep
3D printing
Molecular dynamics
Voids
Cracks
Failure analysis
Precision maintenance

Published Papers (3 papers)

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Research

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11281 KiB

Open AccessFeature PaperArticle

Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching

by Nikky Pathak, Cliff Butcher, Michael James Worswick, Erika Bellhouse and Jeff Gao

Materials 2017, 10(4), 346; https://doi.org/10.3390/ma10040346 - 27 Mar 2017

Cited by 68 | Viewed by 5883

Abstract

The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures. Full article

(This article belongs to the Special Issue Modelling and Characterization of Defects in Metals)

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3598 KiB

Open AccessArticle

Improved Formula for the Stress Intensity Factor of Semi-Elliptical Surface Cracks in Welded Joints under Bending Stress

by Yang Peng, Chao Wu, Yifu Zheng and Jun Dong

Materials 2017, 10(2), 166; https://doi.org/10.3390/ma10020166 - 13 Feb 2017

Cited by 9 | Viewed by 5377

Abstract

Welded joints are prone to fatigue cracking with the existence of welding defects and bending stress. Fracture mechanics is a useful approach in which the fatigue life of the welded joint can be predicted. The key challenge of such predictions using fracture mechanics is how to accurately calculate the stress intensity factor (SIF). An empirical formula for calculating the SIF of welded joints under bending stress was developed by Baik, Yamada and Ishikawa based on the hybrid method. However, when calculating the SIF of a semi-elliptical crack, this study found that the accuracy of the Baik-Yamada formula was poor when comparing the benchmark results, experimental data and numerical results. The reasons for the reduced accuracy of the Baik-Yamada formula were identified and discussed in this paper. Furthermore, a new correction factor was developed and added to the Baik-Yamada formula by using theoretical analysis and numerical regression. Finally, the predictions using the modified Baik-Yamada formula were compared with the benchmark results, experimental data and numerical results. It was found that the accuracy of the modified Baik-Yamada formula was greatly improved. Therefore, it is proposed that this modified formula is used to conveniently and accurately calculate the SIF of semi-elliptical cracks in welded joints under bending stress. Full article

(This article belongs to the Special Issue Modelling and Characterization of Defects in Metals)

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Other

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3728 KiB

Open AccessLetter

Evolution Law of Helium Bubbles in Hastelloy N Alloy on Post-Irradiation Annealing Conditions

by Jie Gao, Liangman Bao, Hefei Huang, Yan Li, Jianrong Zeng, Zhe Liu, Renduo Liu and Liqun Shi

Materials 2016, 9(10), 832; https://doi.org/10.3390/ma9100832 - 14 Oct 2016

Cited by 24 | Viewed by 4082

Abstract

This work reports on the evolution law of helium bubbles in Hastelloy N alloy on post-irradiation annealing conditions. After helium ion irradiation at room temperature and subsequent annealing at 600 °C (1 h), the transmission electron microscopy (TEM) micrograph indicates the presence of helium bubbles with size of 2 nm in the depth range of 0–300 nm. As for the sample further annealed at 850 °C (5 h), on one hand, a “Denuded Zone” (0–38 nm) with rare helium bubbles forms due to the decreased helium concentration. On the other hand, the “Ripening Zone” (38–108 nm) and “Coalescence Zone” (108–350 nm) with huge differences in size and separation of helium bubbles, caused by different coarsening rates, are observed. The mechanisms of “Ostwald ripening” and “migration and coalescence”, experimentally proved in this work, may explain these observations. Full article

(This article belongs to the Special Issue Modelling and Characterization of Defects in Metals)

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