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Dear Colleagues,

Fatigue failure serves as a crucial issue for load-bearing components in engineering. When it serves at high temperature, the material response turns out to be quite different from that at low temperature. Mechanical responses at elevated temperatures are always accompanied with material microstructure evolutions such as dislocation nucleation, slip and elimination, as well as their interaction with secondary phases and grain boundaries. Moreover, combined fatigue, such as the creep–fatigue interaction, and thermo-mechanical fatigue will be encountered as the loading spectrum becomes more and more complex, necessitating the establishment of novel damage evaluating models and more precise experimental techniques.

Original research reports and review articles on fatigue and fracture mechanics for advanced materials at elevated temperatures are of great interest. Contributions are welcome which address the fatigue and fracture behavior of newly emerging material systems, such as additive manufactured materials, high-entropy alloys and composites. Contributions on developments in the areas of high-temperature fracture mechanics are also welcome, to address the recent discoveries on fatigue and fracture failure mechanisms that were ignored or have not been systematically considered. Meanwhile, we encourage scholars to introduce their newly developed experimental facilities as well as the established experimental technologies which assist mechanism investigation at both macro- and meso-scale.

The Editors especially expect innovative contributions which synthesize experimental and theoretical computational studies that yield results with direct engineering significance. By organizing this Special Issue, we hope to create an open and professional platform for excellent scholars to share their thoughts and understandings on fatigue and fracture at high temperatures and promote some progress in the area of structural integrity of related engineering applications.

Prof. Dr. Dianyin Hu
Guest Editor

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Keywords

fatigue
fracture
creep
additive manufacturing
high-entropy alloys
composites
advanced experimental technologies

Published Papers (2 papers)

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Research

30 pages, 11756 KiB

Open AccessArticle

Airport Cement Concrete with Ceramic Dust of Increased Thermal Resistance

by Małgorzata Linek

Materials 2022, 15(10), 3673; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15103673 - 20 May 2022

Cited by 4 | Viewed by 1107

Abstract

The impact of aircraft on airport pavements is varied and closely related to their operational durability. The article presents the impact of the annealing process related to the forced impact of airplanes on airport pavements. The composition of cement concrete with ceramic dust, which is characterized by increased thermal resistance, has been proposed. Two research cycles were programmed, differentiated by the annealing scheme and the way in which the temperature influences the annealing time. Samples stored at a temperature of 20 ± 2 °C were subjected to testing. The tests were carried out for two diagrams: A and B. The first—diagram A—included the continuous impact of the flue gas stream on the samples for a period of 350 min with a test step every 25 min. For the second—diagram B—the samples were alternately heated (1 min) and cooled (15 min). The influence of the proposed pavement mix on changes in the internal structure of cement concrete and the increase in its resistance to high temperatures was determined. In the microstructure of the CC-1 concrete matrix, it was found that there were plate-granular portlandite crystals up to 10 µm in size and ettringite crystals with a length of 8 µm. In the CC-2 concrete, the ettringite crystals were less numerous and had a length of up to 5 µm, there were also continuous contact zones between the aggregate grains and the cement matrix (diagrams A). The alternating annealing/cooling (diagram B) resulted in the ettringite crystals in the CC-1 matrix being up to 10 µm long, and in the CC-2 concrete up to 7 µm long. The contact zone between the aggregate grain and the matrix in CC-2 concrete was continuous, and the microcracks in CC-1 concrete were up to 8 nm. Regardless of the heating diagram, in the surface zone, there were larger microcracks in the CC-1 concrete than in the CC-2 concrete. For diagram A they were 14 µm and 4 µm and for diagram B they were 35 µm and 5 µm, respectively. It was found that concrete with ceramic dust is characterized by a lower and more stable temperature increase. In scheme A, the average temperature increase on the heated surface ranged from 46 °C to 79.5 °C for CC-1 concrete, and from 33.3 °C to 61.3 °C for CC-2 concrete. However, in scheme B, the temperature after 350 heating cycles for CC-1 concrete increased to 129.8 °C, and for CC-2 concrete to 116.6 °C. After the cooling period, the temperature of CC-1 and CC-2 concrete was comparable and amounted to 76.4 C and 76.3 °C, respectively. CC-2 concrete heats to lower values, and favorable changes in internal structure translate into higher strength and durability (after 350 heating cycles according to scheme A, the strength of CC-1 concrete was 67.1 MPa and of CC-2 concrete 83.9 MPa, while in scheme B, respectively, 55.4 MPa for CC-1 and 75 MPa for CC-2). Full article

(This article belongs to the Special Issue High Temperature, Fatigue and Fracture Mechanics of New Materials: Experiment and Evaluation)

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16 pages, 6110 KiB

Open AccessArticle

A Concise Binomial Model for Nonlinear Creep-Fatigue Crack Growth Behavior at Elevated Temperatures

by Jianxing Mao, Zhixing Xiao, Dianyin Hu, Xiaojun Guo and Rongqiao Wang

Materials 2022, 15(2), 651; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15020651 - 15 Jan 2022

Cited by 1 | Viewed by 1420

Abstract

The creep-fatigue crack growth problem remains challenging since materials exhibit different linear and nonlinear behaviors depending on the environmental and loading conditions. In this paper, we systematically carried out a series of creep-fatigue crack growth experiments to evaluate the influence from temperature, stress ratio, and dwell time for the nickel-based superalloy GH4720Li. A transition from coupled fatigue-dominated fracture to creep-dominated fracture was observed with the increase of dwell time at 600 °C, while only the creep-dominated fracture existed at 700 °C, regardless of the dwell time. A concise binomial crack growth model was constructed on the basis of existing phenomenal models, where the linear terms are included to express the behavior under pure creep loading, and the nonlinear terms were introduced to represent the behavior near the fracture toughness and during the creep-fatigue interaction. Through the model implementation and validation of the proposed model, the correlation coefficient is higher than 0.9 on ten out of twelve sets of experimental data, revealing the accuracy of the proposed model. This work contributes to an enrichment of creep-fatigue crack growth data in the typical nickel-based superalloy at elevated temperatures and could be referable in the modeling for damage tolerance assessment of turbine disks. Full article

(This article belongs to the Special Issue High Temperature, Fatigue and Fracture Mechanics of New Materials: Experiment and Evaluation)

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