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Asset management
Published in Bogumil Ulanicki, Kalanithy Vairavamoorthy, David Butler, Peter L.M. Bounds, Fayyaz Ali Memon, Water Management Challenges in Global Change, 2020
Bogumil Ulanicki, Kalanithy Vairavamoorthy, David Butler, Peter L.M. Bounds, Fayyaz Ali Memon
S-N curves are obtained experimentally applying a zero mean fully alternating stress to a material specimen, i.e., a stress that varies symmetrically from.some positive (tensile) value to a negative (compression) value of the same magnitude. The fatigue process is thought to begin at an internal or surface flaw where the stresses are concentrated, and consists initially of shear flow along slip planes. Over a number of cycles, this slip generates intrusions and extrusions that begin to resemble a crack. The crack grows slowly with subsequent stress cycles and may become large enough to satisfy the energy or stress intensity criteria for rapid propagation, producing a fast fracture.
Ship Structure Fatigue and Life Cycle Risk Management Approaches
Published in Jaap Bakker, Dan M. Frangopol, Klaas van Breugel, Life-Cycle of Engineering Systems, 2017
Karl Stambaugh, Miroslaw Lech Kaminski
In contrast to most civil structures, there is no redundancy (independent load carrying paths) in the longitudinal strength of ship structures. A fast fracture will travel through the structure faster than the speed of sound until either the load is reduced or it reaches material tough enough to arrest the crack. In this extreme case, the risk consequences range from loss of service availability and emergency dry docking to catastrophic loss of the ship.
Design Approaches
Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
Use of fast-fracture data and either a deterministic or probabilistic design approach to determine whether the material will withstand the steady-state and peak stresses imposed by the application
Analysis of Ductile-to-Brittle Transition Characteristics of Reactor Pressure Vessel Steels
Published in Nuclear Technology, 2023
On the other hand, using the functional relation of the 0.2% YS and tensile strength with the strain rate–compensated temperature parameter in the present study, it can be shown that the increase in flow stress due to strain hardening is on the order of only 10% to 20% for exceeding the tensile strength in the temperature ranges corresponding to To. In contrast, the stress amplification due to the presence of notches is greater by an order of magnitude. The fracture transition in terms of DBT determined from the tensile strength parameters is also related to the initiation and propagation of cracks, as in a Charpy or fracture toughness experiment. This is implied from the well-known similarity in the morphology of cleavage fracture observed in the tensile and fracture toughness samples that failed in the transition region. Furthermore, with the development of in situ synchrotron microtomography, it has been shown that the maximum stress during a tensile test marks the onset of an exponential increase in general damage content (voids and cracks) in material,58,59 which provides the driving force for fast fracture.
Failure of the threaded region of rockbolts in underground coal mines
Published in Mining Technology, 2018
Honghao Chen, Hamed Lamei Ramandi, Julian Walker, Alan Crosky, Serkan Saydam
Stress corrosion cracking occurs when a susceptible steel is subject to the application of a sustained load (applied and/or residual) in the presence of a corrosive environment (Ashby and Jones 1992; Villalba and Atrens 2008; Zheng 2008; McCafferty 2010; Vandermaat et al. 2016). This type of failure is known to occur in engineering service of many stressed materials in different corrosive environments (Toribio and Ovejero 2000; Turnbull and Zhou 2004; Loto 2017; Wu et al. 2018). The cracks initiate and propagate at a relatively slow rate, determined by the corrosivity of the environment and the magnitude of the stress (Gamboa and Atrens 2003). Final catastrophic failure of rockbolts occurs by fast fracture once the stress corrosion crack reaches a critical crack length, which is determined by the magnitude of the stress and the fracture toughness of the steel (Erdogan 2000; Shutter et al. 2001). Failure of the rockbolt occurs transverse to the bolt axis and is brittle in appearance (Shutter et al. 2001; Elias et al. 2013).
Fused Filament Fabrication of cellular, lattice and porous mechanical metamaterials: a review
Published in Virtual and Physical Prototyping, 2023
Enrique Cuan-Urquizo, Rafael Guerra Silva
Optical, digital and scanning electron microscopes (SEM) have been typically used for the analysis of fracture surfaces, to identify microscopic failure or damage mechanisms, i.e. delamination and stress whitening. For instance, (de Aquino, Maskery, and Longhitano 2020) reported evidence of crack initiation in SEM images due to debonding between layers in woodpile and gyroid scaffolds, with different fracture behaviors in different load directions, although the same response was not observed in diamond scaffolds. Gautam et al. (2018) observed differences in the failure modes according to load orientation in the fracture surface using SEM, with evidence of a fast fracture and crack propagation under shear stress and debonding between adjacent layers. A similar result was reported in (Kladovasilakis et al. 2021), where authors observed the detachment of layers and diagonal shearing across samples using optical microscopy (Figure 16). Maconachie et al. (2020) also used optical microscopy for the observation of the gyroid lattice specimens, reporting that although cracks typically initiate between layers, they can propagate across layers, which suggests that failure is dominated by lattice geometry and not the FDM process. Stress whitening was also observed near damaged regions. Similarly, in (El Jai et al. 2021), the authors reported the whitening of the thinner sections in lattices during compression tests, with the failure of the amorphous polymers caused by the cavitation phenomena, followed by crazing. (Khan et al. 2019) and (Kucewicz et al. 2019) also reported the presence of stress whitening in optical micrographs near the failure region of struts.