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1 – 10 of over 1000Leslie Banks‐Sills, Natalie Konovalov and Adi Fliesher
Fracture tests carried out on bimaterial Brazilian disk specimens have been reported elsewhere. Two material pairs are tested in which each of the constituents is linearly…
Abstract
Purpose
Fracture tests carried out on bimaterial Brazilian disk specimens have been reported elsewhere. Two material pairs are tested in which each of the constituents is linearly elastic, isotropic, and homogeneous. For this material type, the crack fields decouple into in‐plane and out‐of‐plane deformation. Hence, a two‐dimensional approach is taken to analyse the tests. The purpose of this paper is to examine the necessity of using a three‐dimensional approach to predict interface fracture when in‐plane loading is applied.
Design/methodology/approach
To this end, the specimens are analysed by means of two‐ and three‐dimensional finite elements. The interaction energy or M‐integral is used to calculate the stress intensity factors.
Findings
The paper shows that the Mode III stress intensity factor KIII is not negligible near the specimen outer surfaces. Nevertheless, a two‐dimensional analysis will be seen to be sufficient to analyse these tests. This has implications for the practical engineer.
Originality/value
The paper offers a comparison between two‐ and three‐dimensional fracture criteria for a crack along the interface between two homogeneous, isotropic, linear elastic materials when in‐plane loading is applied to the body, and assesses the importance of the out‐of‐plane deformation.
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In this paper, elastic analysis for an edge‐cracked plate of functionally graded materials (FGMs) is carried out. The cracked plate is subject to a longitudinal tension. The…
Abstract
In this paper, elastic analysis for an edge‐cracked plate of functionally graded materials (FGMs) is carried out. The cracked plate is subject to a longitudinal tension. The property of FGMs is assumed to be exponential function form in both x‐ and y‐directions. The finite element method is suggested to solve the boundary value problem. An indirect method, the energy release method, is developed to evaluate the stress intensity factors (SIFs) at the crack tip. Under the applied loading, the amount of the release energy from the crack length “a” to “ a + Δa ” can be evaluated from relevant displacements at the top face of plate. The SIFs can be obtained from a relation between the energy release rate and SIF. The obtained result shows that the property of FGMs has a significant influence to the value of SIF at crack tip. Numerical results are given which are useful for engineer to assess the safety of the cracked plate of FGMs.
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Arash Tavakoli, M. Pourseifi and Sara Rezaei
The purpose of this paper is to provide a theoretical analysis of the fracture behavior of multiple axisymmetric interface cracks between a homogeneous isotropic layer and its…
Abstract
Purpose
The purpose of this paper is to provide a theoretical analysis of the fracture behavior of multiple axisymmetric interface cracks between a homogeneous isotropic layer and its functionally graded material (FGM) coating under torsional loading.
Design/methodology/approach
In this paper, the authors employ the distributed dislocation technique to the stress analysis, an FGM coating-substrate system under torsional loading with multiple axisymmetric cracks consist of annular and penny-shaped cracks. First, with the aid of the Hankel transform, the stress fields in the homogeneous layer and its FGM coating are obtained. The problem is then reduced to a set of singular integral equations with a Cauchy-type singularity. Unknown dislocation density is achieved by numerical solution of these integral equations which are employed to calculate the SIFs.
Findings
From the numerical results, the following key points were observed: first, for two types of the axisymmetric interface cracks, the SIFs decrease with growing in the values of the non-homogeneity. Second, the SIFs increase with increases in interface crack length. Third, the magnitude of the SIFs decreases with increases in the FGM coating thickness. Fourth, the interaction between cracks is an important factor affecting the SIFs of crack tips.
Originality/value
New analytical dislocation solution in an FGM coating-substrate system is developed.
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The purpose of this paper is to evaluate hygro-thermo-mechanically induced normalized stress intensity factor (NSIF) of an edge crack symmetric angle-ply piezo laminated composite…
Abstract
Purpose
The purpose of this paper is to evaluate hygro-thermo-mechanically induced normalized stress intensity factor (NSIF) of an edge crack symmetric angle-ply piezo laminated composite plate (PLCP) using displacement correlation method.
Design/methodology/approach
In the present work, the governing equations are solved through conventional finite element method combined with higher order shear deformation plate theory utilizing the micromechanical approach.
Findings
The effects of crack length, the thickness of the plate and piezoelectric layer, stacking sequences, fiber volume fraction, position of piezoelectric layer, change in moisture and temperature, and voltage on the NSIF are examined. The numerical results are presented in the form of a table for the better understanding and accuracy. The present outlined approach is validated with results available in the literature. These results can become a benchmark for future studies.
Research limitations/implications
The mathematical models theoretically have been developed by considering different parameters. The results are generated using MATLAB 2015 software developed by the authors’ side.
Originality/value
The fracture analysis of a single edge crack PLCP with the effect of a piezoelectric layer at the different location of cracked structures, plate thickness, and actuator voltage and hygro-thermo loading is the novelty of research for health monitoring and high-performance analysis.
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Keyvan Kafaei and Rasul Bagheri
In accord with the literature reviews, there is not a promising examination regarding the several straight and curved cracks interaction with arbitrary arrangement in the…
Abstract
Purpose
In accord with the literature reviews, there is not a promising examination regarding the several straight and curved cracks interaction with arbitrary arrangement in the rectangular FGP plane. The purpose of this paper is to consider the effect of crack length, position of the point load, material non-homogeneity constant and also the arrangement of cracks on the resulting field intensity factors.
Design/methodology/approach
First of all, in order to obtain a set of Cauchy singular integral equations, both the dislocation method and the finite Fourier cosine transform technique are applied. Using the corresponding solution to these equations, the dislocation densities on the crack surfaces are then obtained. Considering the results, both the stress intensity factors (SIFs) and electric displacement intensity factors (EDIFs) for a vertical crack and the interaction between two straight and curved cracks, which have an arbitrary configuration, are determined.
Findings
The numerical examples are represented in order to illustrate the interesting mechanical and electrical coupling phenomena induced by multi-crack interactions. At the end, the effects of the material non-homogeneity constant, the crack length and the cracks arrangements on the SIFs and EDIFs are investigated.
Originality/value
The solutions are obtained in series expansion forms which may be considered as Green’s functions in an FGP rectangular plane possessing multiple cracks. The technique of Green’s function provides the ability to analyze multiple cracks having any smooth configuration.
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Stavros K. Kourkoulis, Ermioni D. Pasiou, Christos F. Markides, Andronikos Loukidis, Ilias Stavrakas and Dimos Triantis
The determination of mode-I fracture toughness of brittle structural materials by means of the notched Brazilian disc configuration is studied. Advantage is taken of a recently…
Abstract
Purpose
The determination of mode-I fracture toughness of brittle structural materials by means of the notched Brazilian disc configuration is studied. Advantage is taken of a recently introduced analytical solution and, also, of data provided by an experimental protocol with notched marble specimens under diametral compression using the loading device suggested by International Society for Rock Mechanics (ISRM) and also the three-dimensional digital image correlation (3D-DIC) technique.
Design/methodology/approach
The analytical solution highlighted the role of geometrical factors, like, for example, the width of the notch, which are usually disregarded. The data of the experimental protocol were comparatively considered with those concerning the response of the specific material under uniaxial tensile load.
Findings
This combined study provided interesting data concerning some open issues, as it is the exact crack initiation point and the level of the critical load causing crack initiation. It was definitely indicated that the crack initiation point is not a priori known (even for notched specimens) and, also, that the maximum recorded load does not correspond by default to the critical load responsible for the onset of catastrophic macroscopic fracture.
Originality/value
It was suggested that the load considered critical one for the determination of mode-I fracture toughness KIC is erroneous. At a load equal to about 70% of the maximum one, a process zone is formed (zone of non-reversible phenomena) around the notch's crown, designating termination of the validity of any linear elastic solution used to determine the normalized stress intensity factors (SIFs). Moreover, at a load level equal to about 95% of the macroscopically observed fracture load, crack propagation has already begun. Therefore, the experimental procedure must be monitored with additional equipment, providing an overview of the displacement field developed during loading.
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Behnam Ameri, Fathollah Taheri-Behrooz, Hamid Reza Majidi and Mohammad Reza Mohammad Aliha
The main aim of this study is to investigate the mixed-mode I/II failure and the cracking manner of three-dimensional (3D)-printed components made by the fused deposition modeling…
Abstract
Purpose
The main aim of this study is to investigate the mixed-mode I/II failure and the cracking manner of three-dimensional (3D)-printed components made by the fused deposition modeling technique in an experimental and theoretical manner.
Design/methodology/approach
Acrylonitrile butadiene styrene (ABS) material and a modified printing method (that increases the adhesion and integrity between the layers and strands) are used for manufacturing the semicircular bending (SCB) test samples. In addition to precracking, the effect of additional stress concentration on the stress field is studied by introducing three small holes to the SCB fracture samples. The critical mixed-mode I/II failure loads obtained from the experiments are predicted using different stress/strain-based fracture theories, including maximum tangential stress (MTS), maximum tangential strain (MTSN), generalized form of MTS and MTSN and combination of them with equivalent material concept (EMC). The effects of plastic deformation, as well as the structural stress concentration, are considered for a more realistic prediction of mixed-mode fracture load.
Findings
The stress-based criteria are more suitable than the strain-based theories. Among the investigated fracture models, the EMC–generalized maximum tangential stress theory provided the best agreement with the experimental results obtained from 3D-printed SCB tests.
Originality/value
The influences of stress risers and applicability of different failure theories in cracked layered 3D-printed parts are studied on the fracture behavior of tested specimens under mixed-mode I/II.
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Igor Varfolomeev, Michael Windisch and Gerben Sinnema
The purpose of this paper is to validate the strain-based failure assessment diagram (SB-FAD) approach for surface cracks in components subjected to displacement controlled…
Abstract
Purpose
The purpose of this paper is to validate the strain-based failure assessment diagram (SB-FAD) approach for surface cracks in components subjected to displacement controlled boundary conditions.
Design/methodology/approach
Numerical analyses are performed for several crack geometries and materials representative for aerospace applications. The performance of the SB-FAD is judged by comparing numerically calculated J-integrals to respective analytical estimates, using both Options 1 and 2 approximations.
Findings
In the most cases, both Options 1 and 2 SB-FAD method results in reasonably conservative J-estimates. Exceptions are for surface cracks in a pressurized vessel made of a material with low-strain hardening, for which Option 2 assessment produces non-conservative results. In contrast, Option 1 assessment is conservative for all geometries considered. In general, Option 1 results in a considerable overestimation of the crack driving force, whereas Option 2 produces rather accurate results in many cases.
Originality/value
The results demonstrate both the potential of the SB-FAD method and needs for its further improvements.
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Chiara Bertolin and Filippo Berto
This article introduces the Special Issue on Sustainable Management of Heritage Buildings in long-term perspective.
Abstract
Purpose
This article introduces the Special Issue on Sustainable Management of Heritage Buildings in long-term perspective.
Design/methodology/approach
It starts by reviewing the gaps in knowledge and practice which led to the creation and implementation of the research project SyMBoL—Sustainable Management of Heritage Buildings in long-term perspective funded by the Norwegian Research Council over the 2018–2022 period. The SyMBoL project is the motivation at the base of this special issue.
Findings
The editorial paper briefly presents the main outcomes of SyMBoL. It then reviews the contributions to the Special Issue, focussing on the connection or differentiation with SyMBoL and on multidisciplinary findings that address some of the initial referred gaps.
Originality/value
The article shortly summarizes topics related to sustainable preservation of heritage buildings in time of reduced resources, energy crisis and impacts of natural hazards and global warming. Finally, it highlights future research directions targeted to overcome, or partially mitigate, the above-mentioned challenges, for example, taking advantage of no sestructive techniques interoperability, heritage building information modelling and digital twin models, and machine learning and risk assessment algorithms.
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Amir Hossein Kohsary, Mohammad Fatehi Marji and Hasan Hosseini Nasab
This paper describes progress on the development of theoretical models required for studying failure mechanism, crack initiation and growth around the boreholes driven by…
Abstract
This paper describes progress on the development of theoretical models required for studying failure mechanism, crack initiation and growth around the boreholes driven by hydrofracturing processes in Hot Dry Rock (HDR) reservoirs of geothermal energy. Due to the importance of the stress intensity factor concept (K) in Fracture Mechanics, some advanced modeling techniques for accurate and fast determination of K for relevant problems are proposed. Alternative tools to deal with stress intensity factor determination are developed and assessed from the points of view of accuracy and computational cost. We concentrate on residual strength, crack initiation and crack growth as a means to model and understand experimentally observed behaviors. Several modeling methods such as compounding and weight function techniques, and boundary and finite element modeling for stress intensity factor calculation are discussed. Further to reviews of those techniques, work performed included (i) developing alternative solutions to deal with boundary‐to‐boundary interaction when using the compounding technique, (ii) relating the precision of K calculations with the level of precision of the crack opening displacement of a reference solution, in order to assess the precision of weight function technique, (iii) modeling relevant geometries using the finite element method (FEM), (iv) working on the implementation of direct stress intensity factor K determination in the Higher Order Displacement Discontinuity Method (HODDM), and (v) developing tools to deal with residual stress fields around the boundary of the hydraulically pressurized boreholes.
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