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In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of the fracture surface. The crack will continue to grow until it reaches a critical size, which occurs when the stress intensity factor of the crack exceeds the fracture toughness of the material, producing rapid propagation and typically complete fracture of the structure.
In metallurgy, a shape-memory alloy (SMA) is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape when heated. It is also known in other names such as memory metal, memory alloy, smart metal, smart alloy, and muscle wire. The "memorized geometry" can be modified by fixating the desired geometry and subjecting it to a thermal treatment, for example a wire can be taught to memorize the shape of a coil spring.
Hydrogen embrittlement (HE), also known as hydrogen-assisted cracking or hydrogen-induced cracking (HIC), is a reduction in the ductility of a metal due to absorbed hydrogen. Hydrogen atoms are small and can permeate solid metals. Once absorbed, hydrogen lowers the stress required for cracks in the metal to initiate and propagate, resulting in embrittlement. Hydrogen embrittlement occurs most notably in steels, as well as in iron, nickel, titanium, cobalt, and their alloys. Copper, aluminium, and stainless steels are less susceptible to hydrogen embrittlement.
Inconel is a nickel-chromium-based superalloy often utilized in extreme environments where components are subjected to high temperature, pressure or mechanical loads. Inconel alloys are oxidation- and corrosion-resistant. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high-temperature applications where aluminium and steel would succumb to creep as a result of thermally-induced crystal vacancies. Inconel's high-temperature strength is developed by solid solution strengthening or precipitation hardening, depending on the alloy.
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Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance, high/low temperature behaviour or wear resistance. These properties in turn govern the application of these materials in industrial practice.
Zirconium alloys are solid solutions of zirconium or other metals, a common subgroup having the trade mark Zircaloy. Zirconium has very low absorption cross-section of thermal neutrons, high hardness, ductility and corrosion resistance. One of the main uses of zirconium alloys is in nuclear technology, as cladding of fuel rods in nuclear reactors, especially water reactors. A typical composition of nuclear-grade zirconium alloys is more than 95 weight percent zirconium and less than 2% of tin, niobium, iron, chromium, nickel and other metals, which are added to improve mechanical properties and corrosion resistance.
In materials science, slip is the large displacement of one part of a crystal relative to another part along crystallographic planes and directions. Slip occurs by the passage of dislocations on close/packed planes, which are planes containing the greatest number of atoms per area and in close-packed directions. Close-packed planes are known as slip or glide planes. A slip system describes the set of symmetrically identical slip planes and associated family of slip directions for which dislocation motion can easily occur and lead to plastic deformation. The magnitude and direction of slip are represented by the Burgers vector, b.
Alan Needleman is a professor of materials science & engineering at Texas A&M University. Prior to 2009, he was Florence Pirce Grant University Professor of Mechanics of Solids and Structures at Brown University in Providence, Rhode Island.
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Slip bands or stretcher-strain marks are localized bands of plastic deformation in metals experiencing stresses. Formation of slip bands indicates a concentrated unidirectional slip on certain planes causing a stress concentration. Typically, slip bands induce surface steps and a stress concentration which can be a crack nucleation site. Slip bands extend until impinged by a boundary, and the generated stress from dislocations pile-up against that boundary will either stop or transmit the operating slip depending on its (mis)orientation.
Angus J Wilkinson is a professor of materials science based at University of Oxford. He is a specialist in micromechanics, electron microscopy and crystal plasticity. He assists in overseeing the MicroMechanics group while focusing on the fundamentals of material deformation. He developed the HR-EBSD method for mapping stress and dislocation density at high spatial resolution used at the micron scale in mechanical testing and micro-cantilevers to extract data on mechanical properties that are relevant to materials engineering.
Duplex stainless steels are a family of alloys with a two-phase microstructure consisting of both austenitic and ferritic phases. They offer excellent mechanical properties, corrosion resistance, and toughness compared to other types of stainless steel. However, duplex stainless steel can be susceptible to a phenomenon known as 475 °C embrittlement or duplex stainless steel age hardening, which is a type of aging process that causes loss of plasticity in duplex stainless steel when it is heated in the range of 250 to 550 °C. At this temperature range, spontaneous phase separation of the ferrite phase into iron-rich and chromium-rich nanophases occurs, with no change in the mechanical properties of the austenite phase. This type of embrittlement is due to precipitation hardening, which makes the material become brittle and prone to cracking.
David Dye is a Professor of Metallurgy at Imperial College London. Dye specialises in fatigue and micromechanics of aerospace and nuclear materials, mainly Ni/Co superalloys, titanium, TWIP steel, and Zirconium alloys.
Dierk Raabe is a German materials scientist and researcher, who has contributed significantly to the field of materials science. He is a professor at RWTH Aachen University and director of the Max Planck Institute for Iron Research in Düsseldorf. He is the recipient of the 2004 Leibniz Prize, and the 2022 Acta Materialia's Gold Medal. He also received the honorary doctorate of the Norwegian University of Science and Technology.
References
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- ↑ "PWP Messages". www.imperial.ac.uk. Retrieved 2022-10-31.
- ↑ Dunne, F P E; Heppenstall, M (January 1990). "The Effect of Joints on the Transverse Vibration of a Simple Structure". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science. 204 (1): 37–42. doi:10.1243/PIME_PROC_1990_204_073_02. ISSN 0263-7154. S2CID 109537371.
- ↑ Dunne, F. P. E.; Makin, J.; Hayhurst, D. R. (1992-06-08). "Automated procedures for the determination of high temperature viscoplastic damage constitutive equations". Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. 437 (1901): 527–544. Bibcode:1992RSPSA.437..527D. doi:10.1098/rspa.1992.0078. S2CID 135736758.
- ↑ Dunne, F. P. E.; Hayhurst, D. R. (1992-06-08). "Modelling of combined high-temperature creep and cyclic plasticity in components using continuum damage mechanics". Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. 437 (1901): 567–589. Bibcode:1992RSPSA.437..567D. doi:10.1098/rspa.1992.0080. S2CID 135555961.
- ↑ "16 May 1996". gazette.web.ox.ac.uk. Archived from the original on 2022-11-24. Retrieved 2022-11-24.
- ↑ "Professor Fionn Dunne". Hertford College | University of Oxford. Retrieved 2022-10-31.
- ↑ "Materials for fusion & fission power".
- ↑ "Micro-mechanical modelling techniques for forming texture, non-proportionality and failure in auto materials".
- ↑ "Micro-mechanical modelling techniques for forming texture, non-proportionality and failure in auto materials".
- ↑ "Heterogeneous Mechanics in Hexagonal Alloys across Length and Time Scales - UKRI".
- ↑ "MIDAS-UKRI".
- ↑ Dunne, Fionn; Petrinic, Nik (2005-06-09). Introduction to Computational Plasticity. OUP Oxford. ISBN 978-0-19-151380-0.
- ↑ Dunne, F. P. E.; Kiwanuka, R.; Wilkinson, A. J. (2012-09-08). "Crystal plasticity analysis of micro-deformation, lattice rotation and geometrically necessary dislocation density". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 468 (2145): 2509–2531. Bibcode:2012RSPSA.468.2509D. doi: 10.1098/rspa.2012.0050 . S2CID 138764550.
- ↑ McDowell, D. L.; Dunne, F. P. E. (2010-09-01). "Microstructure-sensitive computational modeling of fatigue crack formation". International Journal of Fatigue. Emerging Frontiers in Fatigue. 32 (9): 1521–1542. doi:10.1016/j.ijfatigue.2010.01.003. ISSN 0142-1123.
- ↑ Chen, Bo; Jiang, Jun; Dunne, Fionn P. E. (2018-02-01). "Is stored energy density the primary meso-scale mechanistic driver for fatigue crack nucleation?". International Journal of Plasticity. 101: 213–229. doi:10.1016/j.ijplas.2017.11.005. hdl: 10044/1/61871 . ISSN 0749-6419.
- ↑ Guan, Yongjun; Chen, Bo; Zou, Jinwen; Britton, T. Ben; Jiang, Jun; Dunne, Fionn P. E. (2017-01-01). "Crystal plasticity modelling and HR-DIC measurement of slip activation and strain localization in single and oligo-crystal Ni alloys under fatigue". International Journal of Plasticity. 88: 70–88. doi:10.1016/j.ijplas.2016.10.001. hdl: 10044/1/41121 . ISSN 0749-6419.
- ↑ Dunne, F. P. E.; Rugg, D.; Walker, A. (2007-06-01). "Lengthscale-dependent, elastically anisotropic, physically-based hcp crystal plasticity: Application to cold-dwell fatigue in Ti alloys". International Journal of Plasticity. 23 (6): 1061–1083. doi:10.1016/j.ijplas.2006.10.013. ISSN 0749-6419.
- ↑ Britton, T. B.; Liang, H.; Dunne, F. P. E.; Wilkinson, A. J. (2010-03-08). "The effect of crystal orientation on the indentation response of commercially pure titanium: experiments and simulations". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 466 (2115): 695–719. Bibcode:2010RSPSA.466..695B. doi: 10.1098/rspa.2009.0455 . S2CID 2030079.
- ↑ Gong, Jicheng; Benjamin Britton, T.; Cuddihy, Mitchell A.; Dunne, Fionn P. E.; Wilkinson, Angus J. (2015-09-01). "〈a〉 Prismatic, 〈a〉 basal, and 〈c+a〉 slip strengths of commercially pure Zr by micro-cantilever tests". Acta Materialia. 96: 249–257. Bibcode:2015AcMat..96..249G. doi:10.1016/j.actamat.2015.06.020. hdl: 10044/1/31552 . ISSN 1359-6454.
- ↑ IOM3. "Award winners 2017". www.iom3.org. Retrieved 2022-10-31.
{{cite web}}: CS1 maint: numeric names: authors list (link) - ↑ "Previous winners | Staff | Imperial College London". www.imperial.ac.uk. Retrieved 2022-10-31.
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