New Trends in Fracture Mechanics and Fatigue Design

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 10446

Special Issue Editor


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Guest Editor
Department of Chemical Engineering, Materials and Environment, Sapienza University of Rome, 00184 Rome, Italy
Interests: fatigue and fracture behavior of materials; mechanical characterization; structural integrity of conventional and innovative materials
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Special Issue Information

Dear Colleagues,

Fracture mechanics and fatigue design are still very active research fields and, nowadays, new challenges in this field are necessary due to the introduction of new materials and new processes of production. This Special Issue aims to discuss these aspects, giving a clear and complete overview of the state of the art in these fields. New trends in fracture mechanics and fatigue design will be discussed along with the recent developments in innovative materials and innovative processes that are still under investigation. This Special Issue will not only be useful for researchers in these research areas but also for engineers engaged with advanced design problems.

Prof. Filippo Berto
Guest Editor

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Keywords

  • Structural integrity
  • Fatigue design
  • Fracture mechanics
  • Local approaches based on energy criteria
  • Computational mechanics

Published Papers (4 papers)

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Research

18 pages, 9489 KiB  
Article
Effect of Heat Treatment on Microstructure and Creep Behavior of Fe-40Ni-24Cr Alloy
by Maureen Mudang, Esah Hamzah, Hamid Reza Bakhsheshi-Rad and Filippo Berto
Appl. Sci. 2021, 11(17), 7951; https://doi.org/10.3390/app11177951 - 28 Aug 2021
Cited by 7 | Viewed by 2187
Abstract
Iron-nickel-chromium (Fe-Ni-Cr) alloy Haynes HR120 is an iron-nickel-based superalloy, which is extensively used in gas turbines. Hence, the materials for the fabrication of steam turbine blades should present great mechanical characteristics and creep properties. In this study, Fe-40Ni-24Cr was heat-treated at temperatures from [...] Read more.
Iron-nickel-chromium (Fe-Ni-Cr) alloy Haynes HR120 is an iron-nickel-based superalloy, which is extensively used in gas turbines. Hence, the materials for the fabrication of steam turbine blades should present great mechanical characteristics and creep properties. In this study, Fe-40Ni-24Cr was heat-treated at temperatures from 950 to 1250 °C. High temperature creep behavior and microstructure evolution of the selected heat-treated (1050 °C, 1200 °C, 1225 °C and 1250 °C) Fe-40Ni-24Cr alloy were assessed at temperatures of 800 °C and 900 °C under 100 MPa stress. The alloy consisted of titanium and niobium rich precipitates, namely NbC, (Nb,Ti)C, TiN and Ti(C,N) distributed in the matrix grain boundaries, which enhance the creep properties of the alloy. The hardness of heat-treated Fe-40Ni-24Cr alloy decreased with increasing temperature and grain size. The creep strain of the Fe-40Ni-24Cr alloy increased with escalation in the creep time and the temperature being under constant applied stress. Fe-40Ni-24Cr alloy shows a decrease in steady-state creep rate with an increase in grain size from 62 μm to 183 μm due to the grain boundary sliding mechanism and 183 μm to 312 μm due to the occurrence of dislocation climb. This result exhibited that grain size has a significant influence on the alloys’ high temperature creep properties. Full article
(This article belongs to the Special Issue New Trends in Fracture Mechanics and Fatigue Design)
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12 pages, 3817 KiB  
Article
Determination of Stress Intensity Factors under Shock Loading Using a Diffraction-Based Technique
by Matúš Turis, Oľga Ivánková, Peter Burik and Milan Držík
Appl. Sci. 2021, 11(10), 4574; https://doi.org/10.3390/app11104574 - 17 May 2021
Cited by 2 | Viewed by 1482
Abstract
An experimental optical method has been developed for the measurement of opening and sliding notch face movements. The light passing through a thin slit is monitored by a photodiode detector. Two parts of the slit are fixed independently on the notch faces of [...] Read more.
An experimental optical method has been developed for the measurement of opening and sliding notch face movements. The light passing through a thin slit is monitored by a photodiode detector. Two parts of the slit are fixed independently on the notch faces of the simulated crack. Dynamic variations of the notch face movements are recorded as an electric signal by an oscilloscope. The sensitivity of such displacement measurement is comparable with the wavelength of light. Dynamic mixed-mode stress intensity factors under shock loading were evaluated from the data obtained and subsequently compared with a numerical simulation by ANSYS software. As it was approved, the technique has shown sufficient sensitivity, good linearity, and measurement reliability. Due to its non-destructive nature and overall robustness, the arrangement is applicable even for structural component condition determination taking into consideration potentially unknown boundary conditions and the non-linear character of mechanical parameters. Full article
(This article belongs to the Special Issue New Trends in Fracture Mechanics and Fatigue Design)
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13 pages, 2675 KiB  
Article
Using the Equivalent Material Concept and the Average Strain Energy Density to Analyse the Fracture Behaviour of Structural Materials
by Sergio Cicero, Juan Diego Fuentes and Ali Reza Torabi
Appl. Sci. 2020, 10(5), 1601; https://doi.org/10.3390/app10051601 - 28 Feb 2020
Cited by 13 | Viewed by 2775
Abstract
This paper provides a complete overview of the applicability of the Equivalent Material Concept in conjunction with the Average Strain Energy Density criterion, to provide predictions of fracture loads in structural materials containing U-notches. The Average Strain Density Criterion (ASED) has a linear-elastic [...] Read more.
This paper provides a complete overview of the applicability of the Equivalent Material Concept in conjunction with the Average Strain Energy Density criterion, to provide predictions of fracture loads in structural materials containing U-notches. The Average Strain Density Criterion (ASED) has a linear-elastic nature, so in principle, it does not provide satisfactory predictions of fracture loads in those materials with nonlinear behaviour. However, the Equivalent Material Concept (EMC) is able to transform a physically nonlinear material into an equivalent linear-elastic one and, therefore, the combination of the ASED criterion with the EMC (EMC–ASED criterion) should provide good predictions of fracture loads in physically nonlinear materials. The EMC–ASED criterion is here applied to different types of materials (polymers, composites and metals) with different grades of nonlinearity, showing the accuracy of the corresponding fracture load predictions and revealing qualitatively the limitations of the methodology. It is shown how the EMC–ASED criterion provides good predictions of fracture loads in nonlinear materials as long as the nonlinear behaviour is mainly limited to the tensile behaviour, and how the accuracy decreases when the nonlinear behaviour is extended to the material behaviour in the presence of defects. Full article
(This article belongs to the Special Issue New Trends in Fracture Mechanics and Fatigue Design)
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13 pages, 3298 KiB  
Article
Numerical Investigation of Strength Mismatch Effect on Ductile Crack Growth Resistance in Welding Pipe
by Lin Su, Jie Xu, Wei Song, Lingyu Chu, Hanlin Gao, Pengpeng Li and Filippo Berto
Appl. Sci. 2020, 10(4), 1374; https://doi.org/10.3390/app10041374 - 18 Feb 2020
Cited by 5 | Viewed by 2233
Abstract
The effect of strength mismatch (ratio between the yield stress of weld metal and base metal, My) on the ductile crack growth resistance of welding pipe was numerically analyzed. The ductile fracture behavior of welding pipe was determined while using the [...] Read more.
The effect of strength mismatch (ratio between the yield stress of weld metal and base metal, My) on the ductile crack growth resistance of welding pipe was numerically analyzed. The ductile fracture behavior of welding pipe was determined while using the single edge notched bending (SENB) and single edge notched tension (SENT) specimens, as well as axisymmetric models of circumferentially cracked pipes for comparison. Crack growth resistance curves (as denoted by crack tip opening displacement-resistance (CTOD-R curve) have been computed using the complete Gurson model. A so-called CTOD-Q-M formulation was proposed to calculate the weld mismatch constraint M. It has been shown that the fracture resistance curves significantly increase with the increase of the mismatch ratio. As for SENT and pipe, the larger My causes the lower mismatch constraint M, which leads to the higher fracture toughness and crack growth resistance curves. When compared with the standard SENB, the SENT specimen and the cracked pipe have a more similar fracture resistance behavior. The results present grounds for justification of usage of SENT specimens in fracture assessment of welding cracked pipes as an alternative to the traditional conservative SENB specimens. Full article
(This article belongs to the Special Issue New Trends in Fracture Mechanics and Fatigue Design)
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