Relevant bibliographies by topics / Crack tip plasticity

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Crack tip plasticity'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Crack tip plasticity"

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Liu, Wen Hui, Hao Huang, Zhi Gang Chen, and Da Tian Cui. "Simulation of Crack Tip Plasticity Using 3D Crystal Plasticity Theory." Advanced Materials Research 291-294 (July 2011): 1057–61. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1057.

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To investigate the plasticity distribution of microstructurally small crack tip in FCC crystals, the crack tip opening displacment(CTOD), crack tip plastic zone and maximum plastic work for stationary microstructurally small cracks were calculated with the three dimensional crystal plasticity finite element theory, which was implemented in the finite element code ABAQUS with the rate dependent crystal plasticity theory code as user material subroutine. Results show that crystallographic orientation has significant influence on CTOD and maximum plastic work. The CTOD and maximum plastic work in hard orientation are larger than that in soft orientaion under the displacement controlled boundary condition, which means that crack in hard orientation is more likely to extend than that in soft orientaion. The high-angle grain boundary shows a tendency to reduce crack extension, and the dislocation ahead of the crack tip becomes blocked by high-angle grain boundary.
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El-Emam, Hesham, Alaaeldin Elsisi, Hani Salim, and Hossam Sallam. "Fatigue Crack Tip Plasticity for Inclined Cracks." International Journal of Steel Structures 18, no. 2 (April 26, 2018): 443–55. http://dx.doi.org/10.1007/s13296-018-0016-z.

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Hartmaier, Alexander, and Peter Gumbsch. "Scaling relations for crack-tip plasticity." Philosophical Magazine A 82, no. 17-18 (November 2002): 3187–200. http://dx.doi.org/10.1080/01418610208240432.

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Mataga, P. A., L. B. Freund, and J. W. Hutchinson. "Crack tip plasticity in dynamic fracture." Journal of Physics and Chemistry of Solids 48, no. 11 (1987): 985–1005. http://dx.doi.org/10.1016/0022-3697(87)90115-6.

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Zhang, J. Z., Xiao Dong He, X. Song, and Shan Yi Du. "Elastic-Plastic Finite Element Analysis of the Effect of the Compressive Loading on the Crack Tip Plasticity." Key Engineering Materials 324-325 (November 2006): 73–76. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.73.

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An elastic-plastic finite element analysis of the effect of the compressive loading on crack tip plasticity is presented. Two center-cracked panel specimens with different crack lengths are analysed under tension-compression loading. The size and shape of the crack tip reverse plastic zone, the crack opening profiles of the crack tip for short (0.1 mm) and long crack (2 mm) have been studied. The analysis shows that the compressive loading has a significant contribution towards the crack tip plasticity.
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Liu, Ran, Hui Huang, Jia Ju Liu, Wei Wang, Li Rong, and Zuo Ren Nie. "Finite Element Analysis on the Effect of the Texture to the Crack Tip Plasticity in Aluminum Alloy." Materials Science Forum 850 (March 2016): 328–33. http://dx.doi.org/10.4028/www.scientific.net/msf.850.328.

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Plasticity zone at crack tip of aluminum alloy with fcc structure is investigated in order to analyze the effect of crystal orientation to the plasticity distribution on crack tip, as well as the effect to CTOD and J-integral, which is implemented using finite element code in Abaqus with a rate dependent crystal plasticity theory. The results show that the crack tip plasticity, stresses and CTOD are significantly affected by grain orientations. When the grains have single textures, Cube and S orientations have a strong ability to against crack propagation. However, when the grains combine textures, the increasing of misorientation enhances the resistance for crack growth. And when the tilt angle is higher, the crack deflection is promoted to reduce the crack propagation rate.
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Farkas, Diana. "Atomistic Studies of Intrinsic Crack-Tip Plasticity." MRS Bulletin 25, no. 5 (May 2000): 35–38. http://dx.doi.org/10.1557/mrs2000.71.

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One of the most interesting unsolved problems in fracture mechanics is the precise understanding of the energy-dissipation mechanisms that occur as a crack advances. In most cases, this energy-release rate is many times the surface energy created. One of the main reasons for this difference is the fact that plastic deformation can occur in the crack-tip region as dislocations nucleate and are emitted from the crack tip. Experimental studies provide little insight into the precise mechanisms for this process because they cannot reach the atomistic scale. For example, a crack that may seem experimentally sharp, and therefore indicative of brittle fracture, may not be sharp at the atomic level. Continuum mechanics has a similar limitation, since the assumptions of elasticity theory usually break down in the crack-tip region. Atomistic simulation studies provide researchers an opportunity to obtain precise atomic configurations in the crack-tip region under various loading conditions and to observe the basic energy-dissipation mechanisms.
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Tomlinson, Rachel A., Ying Du, and Eann A. Patterson. "Understanding Crack Tip Plasticity – a Multi-Experimental Approach." Applied Mechanics and Materials 70 (August 2011): 153–58. http://dx.doi.org/10.4028/www.scientific.net/amm.70.153.

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Crack tip plasticity has been investigated using thermoelastic stress analysis (TSA) and digital image correlation (DIC). The plastic zone size at the tip of a propagating fatigue crack was measured using both techniques. At longer crack lengths, the results compared well with Dugdale’s and Irwin’s models for crack tip yielding. The TSA methodology requires careful observation of the adiabatic assumption.
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Sadananda, K., and D. N. V. Ramaswamy. "Role of crack tip plasticity in fatigue crack growth." Philosophical Magazine A 81, no. 5 (May 2001): 1283–303. http://dx.doi.org/10.1080/01418610108214441.

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Ramaswamy, K. Sadanandaa, Dorai-Nirmal V. "Role of crack tip plasticity in fatigue crack growth." Philosophical Magazine A 81, no. 5 (May 1, 2001): 1283–303. http://dx.doi.org/10.1080/01418610110033876.

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Dissertations / Theses on the topic "Crack tip plasticity"

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Hartmaier, Alexander. "Modeling of crack-tip plasticity in Tungsten single crystals." [S.l. : s.n.], 2000. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9444852.

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Blomerus, P. M. "The application of distributed dislocations to the modelling of plane plastic flow." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268175.

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Shinko, Tomoki. "Experimental Characterization of Influence of Gaseous Hydrogen on Fatigue Crack Propagation and Crack Tip Plasticity in Commercially Pure Iron." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2019. http://www.theses.fr/2019ESMA0003/document.

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L’objectif de cette étude est de caractériser expérimentalement la propagation de fissures de fatigue affectée par l’hydrogène (Hydrogen-Affected Fatigue Crack Growth, HAFCG) dans diverses conditions et de clarifier le mécanisme impliqué en se concentrant sur la plasticité en pointe de fissures. Pour cet objectif, dans une première étape, l’influence de l’hydrogène sur la déformation plastique a été étudiée à l’aide d’essais de traction effectués sur un fer commercialement pur, le fer Armco, sous hydrogène gazeux. Les résultats ont montré que l’effet de l’hydrogène sur la propagation des fissures après apparition de la striction est plus important que celui sur la déformation plastique uniforme. Le HAFCG a ensuite été étudié au moyen d’essais de fissuration pour diverses valeurs de l’amplitude de facteur d’intensité de contrainte ΔK, de pression d’hydrogène (PH2 = 3,5 et 35 MPa) et de fréquence de chargement (f = 0,02 - 20 Hz). Il a été révélé que les vitesses de propagation dans un régime à ΔK élevé étaient fortement augmentées par l'hydrogène, jusqu'à 50 fois plus élevé que celles dans l'air. Le mode de rupture est une rupture intergranulaire fragile dans un régime de propagation à faible ΔK, alors qu’on observe une rupture transgranulaire de type quasi-clivage dans un régime à ΔK élevé. La valeur de ΔKtr (valeur de ΔK déclenchant l'augmentation de la vitesse de fissuration) diminue en augmentant la pression PH2. En outre, la vitesse augmente en diminuant la fréquence f. Une fois que la fréquence devient inférieure à une valeur critique, la vitesse de fissuration diminue considérablement jusqu'au même niveau que celle sous azote. La plasticité en pointe de fissure a été analysée à plusieurs échelles par microscopie optique, par mesure de déplacement hors plan et par microscopie électronique à balayage par transmission de la structure de dislocation située immédiatement sous la surface de rupture (FIB/STEM). Aucune modification claire de la zone plastique monotone en pointe de fissure sous hydrogène n’a été observée, alors qu’une réduction drastique de la plasticité cyclique associée à l'augmentation de la vitesse a été identifiée. Sur la base des observations expérimentales, des modèles de mécanisme de fissuration intergranulaire induit par l'hydrogène impliquant la coalescence des micro-vides le long de joints de grain et de mécanisme de fissuration transgranulaire induit par l'hydrogène impliquant un clivage cyclique dû à la réduction de la plasticité en pointe de fissure ont été proposés. Trois critères caractéristiques de fissuration assistée par hydrogène (ΔKtr, gradient d'hydrogène (PH2 × f)1/2 et limite supérieure de vitesse de fissuration) ont été établis. Ces critères devraient être utiles pour améliorer la conception en fatigue et la fiabilité des équipements exposés à l'hydrogène gazeux
The objective of this study is to experimentally characterize Hydrogen-Affected Fatigue Crack Growth (HAFCG) behavior under various conditions and clarify the mechanism by focusing on crack tip plasticity. For this objective, as a first step, the influence of hydrogen on plastic deformation has been investigated by means of tensile tests in a commercially pure iron, Armco iron, under gaseous hydrogen. The results of the tests pointed out that the hydrogen effect on crack propagation is more important than that on uniform plastic deformation. Then, the HAFCG was investigated by means of FCG tests under various conditions of crack tip stress intensity ΔK, hydrogen gas pressure (PH2 = 3.5 and 35 MPa) and loading frequency (f = 0.02 – 20 Hz). It has been revealed that the FCGRs in a high ΔK regime were highly enhanced by hydrogen up to 50 times higher than the one in air. The fracture mode was a brittle intergranular fracture in a low ΔK regime, while it is a brittle transgranular quasi-cleavage one in a high ΔK regime. The value of ΔKtr (value of ΔK triggering the FCGR enhancement) decreases by increasing the pressure PH2. Besides, the FCGR enhancement increases by decreasing the frequency f. Once f becomes lower than a critical value, the HAFCG rate significantly decreases down to the same level as in nitrogen., The crack tip plasticity was analyzed in a multiscale approach by means of optical microscopy, out-of-plane displacement measurement, and scanning transmission electron microscopy of dislocation structure immediately beneath the fracture surface (FIB/STEM). As a result, no clear modification of monotonic crack tip plasticity by hydrogen was observed, while a drastic reduction of cyclic crack tip plasticity associated with the FCGR enhancement was identified. Based on the experimental evidences, models of the hydrogen-induced intergranular FCG mechanism involving microvoid coalescence along grain boundary and the hydrogen-induced transgranular FCG mechanism involving cyclic cleavage due to crack tip plasticity reduction have been proposed. Three characteristic criteria of HAFCG (ΔKtr, hydrogen gradient (PH2 × f)1/2 and upper limit of FCGR) have been established. These criteria are expected to be useful for improving fatigue design and reliability of hydrogen-related equipment
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Walker, Anthony E. "The effects of notch parameters and crack tip plasticity on AC potential drop used in high frequency crack monitoring." Thesis, Sheffield Hallam University, 1987. http://shura.shu.ac.uk/20483/.

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The ACPD method is probably the most versatile of all the commercially available NDE techniques. However as applications of such systems increase so does the awareness of serious limitations in present ACPD knowledge. In particular high local crack and notch tip strains can have a marked effect on ACPD response leading to substantial errors in estimates of crackdepth and growth rates. In the present study an investigation has been undertaken into the influence of elastic/plastic notch tip strain on the response of ACPD crack monitoring systems. Experimental work has been undertaken to produce data on the ACPD response observed in two magnetically contrasting materials (EN1A mild steel, NE8 aluminium alloy) using a series of V and U notched bend specimens. An extensive elastic/plastic finite element analysis was conducted to accurately determine the different notch tip strain fields for both materials. A fundamental study was also undertaken into the influence of strain on the electrical resistivity and relative magnetic permeability, the two material parameters governing the ACPD response. The information obtained from the investigations together with results from the FE analysis has made it possible to understand and quantify the influence of elastic/plastic deformation on ACPD response. An electric field model has been successfully developed to explain and predict the effect of increasing strain on the ACPD response in materials where the skin effect is strong. Results have also shown the inapplicability of the compensation method of crack monitoring when levels of plasticity are appreciable and an alternative method has been proposed.
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Hartmaier, Alexander [Verfasser]. "Modeling of crack-tip plasticity in tungsten single crystals / Max-Planck-Institut für Metallforschung, Stuttgart. Vorgelegt von Alexander Hartmaier." Stuttgart : Max-Planck-Inst. für Metallforschung, 2000. http://d-nb.info/962399469/34.

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Lu, Xuekun. "Characterisation of the anisotropic fracture toughness and crack-tip shielding mechanisms in elephant dentin." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-the-anisotropic-fracture-toughness-and-cracktip-shielding-mechanisms-in-elephant-dentin(5f0a739b-e30a-401e-905a-b38e9224ac0a).html.

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Teeth trauma has become one of the most serious physical problems that people are suffering from in the past years. Early diagnosis and management are desperately needed to improve tooth survival, functionality and avoid the tooth loss. However, the diagnosis of cracked tooth could be challenging due to the small size of the crack. Therefore, a mechanics understanding of the tooth fracture is demanding from the perspective of developing a framework for failure prediction in clinical research and bio-mimetic restorative materials. This study focuses on characterising the anisotropic fracture behaviour and the crack shielding mechanisms in elephant dentin. This is often used as a structural analogue for human dentin due to the similarities in microstructure and chemical composition, in order to avoid the test-piece size restrictions, given the larger size of ivory than human teeth. Compact tension test-pieces were extracted from different locations on the ivory tusk so as to have different crack growth directions relative to the microstructure to inspect the fracture anisotropies. The fracture toughness as a function of the crack extension was assessed in terms of fracture resistance curves (R-curve). The accumulative crack-tip strain fields were also measured for the first time in dentin using digital image correlation technique (DIC) to investigate the capability of crack-tip elastic/plastic deformation before material failure. Investigation of crack morphologies, the interaction between crack and the microstructures, the fracture surfaces using both 2-D and 3-D techniques could provide with insights into extrinsic shielding mechanisms. Surface and volume crack opening displacement (COD) were measured for the first time optically and by X-ray computed tomography to investigate the effect of extrinsic crack-tip shielding. The displacement fields around the crack-tip obtained by DIC were fitted using Westergaard’s analytical solution to extract the effective stress intensity factor, by comparing this to the applied load, the efficiency of the crack-tip shielding could be evaluated. A novel cohesive element model (traction-separation law) was then established based on the COD results to simulate the physical process of crack-tip shielding. It is the first time the cohesive model has been adapted to studying the direct crack behaviour measured by in-situ experiment to predict the crack growth. This model was then validated using the crack-tip strain field and R-curve obtained from the experiment measurement.
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Newman, John Andrew. "The Effects of Load Ratio on Threshold Fatigue Crack Growth of Aluminum Alloys." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29418.

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The integrity of nearly all engineering structures are threatened by the presence of cracks. Structural failure occurs if a crack larger than a critical size exists. Although most well designed structures initially contain no critical cracks, subcritical cracks can grow to failure under fatigue loading, called fatigue crack growth (FCG). Because it is impossible or impractical to prevent subcritical crack growth in most applications, a damage tolerant design philosophy was developed for crack sensitive structures. Design engineers have taken advantage of the FCG threshold concept to design for long fatigue lives. FCG threshold (DKth) is a value of DK (crack-tip loading), below which no significant FCG occurs. Cracks are tolerated if DK is less than DKth. However, FCG threshold is not constant. Many variables influence DKth including microstructure, environment, and load ratio. The current research focuses on load ratio effects on DKth and threshold FCG. Two categories of load ratio effects are studied here: extrinsic and intrinsic. Extrinsic load ratio effects operate in the crack wake and include fatigue crack closure mechanisms. Intrinsic load ratio effects operate in the crack-tip process zone and include microcracking and void production. To gain a better understanding of threshold FCG load ratio effects (1) a fatigue crack closure model is developed to consider the most likely closure mechanisms at threshold, simultaneously, and (2) intrinsic load ratio mechanisms are identified and modeled. An analytical fatigue crack closure model is developed that includes the three closure mechanisms considered most important at threshold (PICC, RICC, and OICC). Crack meandering and a limited amount of mixed-mode loading are also considered. The rough crack geometry, approximated as a two-dimensional sawtooth wave, results in a mixed-mode crack-tip stress state. Dislocation and continuum mechanics concepts are used to determine mixed-mode crack face displacements. Plasticity induced crack closure is included by modifying an existing analytical model, and an oxide layer in the crack mouth is modeled as a uniform layer. Finite element results were used to verify the analytical solutions for crack-tip stress intensity factor and crack face displacements. These results indicate that closure for rough cracks can occur at two locations: (1) at the crack-tip, and (2) at the asperity nearest the crack-tip. Both tip contact and asperity contact must be considered for rough cracks. Tip contact is more likely for high Kmax levels, thick oxide layers, and shallow asperity angles, a. Model results indicate that closure mechanisms combine in a synergistic manner. That is, when multiple closure mechanisms are active, the total closure level is greater than the sum of individual mechanisms acting alone. To better understand fatigue crack closure where multiple closure mechanisms are active (i.e. FCG threshold), these interactions must be considered. Model results are well supported by experimental data over a wide range of DK, including FCG threshold. Closure-free load ratio effects were studied for aluminum alloys 2024, 7050, and 8009. Alloys 7050 and 8009 were selected because load ratio effects at FCG threshold are not entirely explained by fatigue crack closure. It is believed that closure-free load ratio mechanisms occur in these alloys. Aluminum alloy 2024 was selected for study because it is relatively well behaved, meandering most load ratio effects are explained by fatigue crack closure. A series of constant Kmax threshold tests on aluminum alloys were conducted to eliminate fatigue crack closure at threshold. Even in the absence of fatigue crack closure load ratio (Kmax) effects persist, and are correlated with increased crack-tip damage (i.e. voids) seen on the fatigue crack surfaces. Accelerated FCG was observed during constant Kmax threshold testing of 8009 aluminum. A distinct transition is seen the FCG data and is correlated with a dramatic increase in void production seen along the crack faces. Void production in 8009 aluminum is limited to the specimen interior (plane-strain conditions), promoting crack tunneling. At higher values of Kmax (+_ 22.0 MPaà m), where plane-stress conditions dominate, a transition to slant cracking occurs at threshold. The transition to slant cracking produces an apparent increase in FCG rate with decreasing DK. This unstable threshold behavior is related to constraint conditions. Finally, a model is developed to predict the accelerated FCG rates, at higher Kmax levels, in terms of crack-tip damage. The effect of humidity (in laboratory air) on threshold FCG was studied to ensure that environmental effects at threshold were separated from load ratio effects. Although changes in humidity were shown to strongly affect threshold FCG rates, this influence was small for ambient humidity levels (relative humidity between 30% and 70%). Transient FCG behavior, following an abrupt change in humidity level, indicated environmental damage accumulated in the crack-tip monotonic plastic zone. Previous research implies that hydrogen (a component of water vapor) is the likely cause of this environmental damage. Analysis suggests that bulk diffusion is not a likely hydrogen transport mechanism in the crack-tip monotonic plastic zone. Rather, dislocation-assisted diffusion is presented as the likely hydrogen transport mechanism. Finally, the (extrinsic) fatigue crack closure model and the (intrinsic) crack-tip damage model are put in the context of a comprehensive threshold model. The ultimate goal of the comprehensive threshold model is to predict fatigue lives of cyclically loaded engineering components from (small) crack nucleation, through FCG, and including failure. The models developed in this dissertation provide a basis for a more complete evaluation of threshold FCG and fatigue life prediction. The research described in this dissertation was performed at NASA-Langley Research Center in Hampton, Virginia. Funding was provided through the NASA GSRP program (Graduate Student Researcher Program, grant number NGT-1-52174).
Ph. D.
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Hiwarkar, Vikrant. "Nonlinear dynamics of cracked structures for non-destructive evaluation." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6712.

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The power plant and aerospace industries have been facing a huge loss, due to structural failure. The structural failure occurs due to the presence of the crack in it. Hence, it becomes necessary to monitor the structural health under operating condition. Most of the techniques, for structural health monitoring are used for a specific purpose. Some of these techniques require structure dismantling, which is very much expensive and time consuming. So the vibration based structural health monitoring is advantageous, compared to other techniques. Most of the vibration based Structural Health Monitoring (SHM) approaches, use linear vibration theory. But, these linear vibration based procedures, have inherently low sensitivity to crack. Since crack introduces nonlinearities in the system, their merits in damage detection need to be investigated for SHM. In this thesis, the problem is focused on studying nonlinear dynamics of cracked structures for Structural Health Monitoring. For this, simulations and experiments are performed. The new procedure for the simulation is developed using Matlab-Simulink. It uses the numerical approximation for dynamic compliance operators and a nonlinear model of cracks contact faces interaction to study the dynamic behaviour of the cracked bar. Furthermore, the finite element model of the cracked cantilever bar with crack- tip plasticity is developed and the dynamic behaviour of the elasto-plastic bar is studied. Additionally, numerous experiments are performed to study the dynamics of cantilever bar with the fatigue crack in it. The results from Matlab-Simulink simulation shows the distribution of higher harmonics generated along the bar length, as a function of distance from the crack. In finite element simulation, comparison is made between the resonance frequency of cracked cantilever bar with and without crack-tip plasticity. It is found that, there is decrease in resonance frequency of the cracked bar with cracked tip plasticity, when compared with the resonance frequency of cracked bar without crack-tip plasticity. This reduction in resonance frequency is due to the crack-induced plasticity near the crack tip which affects the overall stiffness of bar. In experiments, the response is measured at four different points on the cracked cantilever bar at a given resonant frequency of excitation at lower and higher vibration amplitude. For lower vibration amplitude, it is found that the response obtained near the vicinity of the crack shows the presence of higher harmonics of resonant frequency, which disappears in the response obtained far away from the crack. For higher vibration amplitude, it is found that the response obtained near the vicinity of the crack shows the presence of higher harmonics along with the low frequency component. This low frequency component causes modulation, which leads to the generation of side band frequencies near the resonant frequency. The occurrence of low frequency component and side band frequencies is due to the vibro-impact behaviour of crack. The amplitude of these side band frequencies and higher harmonics are reduced in the response obtained far away from the crack. This indicates that crack-induced nonlinearity has a localized effect on the dynamics of bar. It is also observed that the magnitude of low frequency component is proportional to the magnitude of resonant frequency of excitation. This indicates that crack behaves like a signal modulator, detector of low frequency component and amplifier as the magnitude of low frequency component is proportional to the magnitude of resonant frequency excitation. From the Matlab-Simulink simulation and experimental results, it is concluded that crackinduced nonlinearity affects the dynamic behaviour of the cracked bar significantly, which will be effective in structural health monitoring. Keywords: vibro-impact, crack, dynamic compliance, harmonics, modulator, detector, amplifier, crack-tip plasticity, resonance frequency, structural health monitoring.
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Baccar, Manel. "Etude de l'endommagement et du comportement en fatigue des aciers à outils." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2014. http://www.theses.fr/2014EMAC0001/document.

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Les outillages de mise en forme à chaud sont soumis à des sollicitations thermomécaniques transitoires. Ils sont donc confrontés à la fissuration par fatigue. Le but de ce travail est d'étudier le comportement et la durée de vie en fatigue des aciers d'outillage, notamment leurs résistances à la propagation de fissure. Dans un premier temps, les chargements thermiques imposés aux outillages de fonderie sous pression de magnésium et d'emboutissage à chaud ont été évalués. Ensuite, le comportement et la durée de vie de l'acier à haute conductivité thermique HDC1 ont été étudiés et comparés à l'acier AISI H11 (acier de référence) en fonction de la température. L'acier HDC1 présente un adoucissement cyclique stable à 20°C et 300°C. Par contre, l'intensité d'adoucissement est plus importante à hautes températures. La durée de vie a été étudiée en utilisant les lois de Manson-Coffin et de Basquin. A hautes températures, l'oxydation devient un mécanisme d'endommagement primordial pour l'acier HDC1 et provoque des durées de vie plus courtes que celles observées sur l'acier AISI H11. La résistance à la propagation de fissure de fatigue a été déterminée dans des aciers à la température ambiante par le biais de critères : l'amplitude de facteur d'intensité de contrainte (∆K) et l'amplitude d'ouverture en pointe de fissure (∆CTOD). La méthode de corrélation d'images a permis de mesurer (∆COD) et d'évaluer (∆CTOD). L'ensemble de ces résultats a permis de mettre en évidence l'effet de fermeture de fissure et le comportement plastique en pointe de fissure. ∆CTOD présente un bon critère pour rationaliser la propagation de fissure dans les aciers étudiés.Enfin, la simulation numérique de la propagation de fissure en fatigue a été menée dans l'acier AISI H11 à 600°C par la méthode de relâchement des nœuds en éléments finis. L'effet des modèles de comportement monotone (élastoplastique) et cyclique (élastoviscoplastique) a été étudié sur le calcul de l'ouverture de fissure et la plasticité en pointe de fissure. L'influence du modèle de comportement est faible sur le calcul de l'amplitude d'ouverture de fissure ∆COD, du fait d'une plasticité confinée en pointe de fissure. Alors que, le modèle de comportement cyclique est mieux adapté pour décrire la plasticité en pointe de fissure
Hot metal forming tools are subjected to cyclic thermomechanical loading and damage by complex fatigue/wear/oxidation interactions. Thermal solicitations were measured on high pressure die casting and hot stamping processes. Based on thermal measurements, the isothermal fatigue behaviour and lifetime of a new high conductivity steel HDC1 were investigated at different temperatures and strain amplitude then compared to AISI H11 steel. As AISI H11, continue cyclic softening was observed in HDC1 at all temperatures. The Manson-Coffin and Basquin laws were used for life prediction models under different temperatures. It was observed that the fatigue/oxidation interaction was a principal damage mechanism of the HDC1 steel at high temperature. Fatigue crack propagation in steels was investigated at room temperature in SENT specimens. A digital image correlation technique was used to evaluate crack opening (∆COD) and crack tip opening displacement (∆CTOD) ranges. Crack growth rate were investigated using ∆K (Paris law) and ∆CTOD criteria. It was observed that the cyclic crack tip plasticity control the crack propagation resistance. Crack closure could be evaluated by ∆CTOD.Finite element method by debond technique was used to model the crack propagation of AISI H11 at 600°C using both monotonic elasto-plastic (EP) and cyclic elasto-viscoplastic (EVP) constitutive laws materials. The comparison of ∆COD calculated and measured had shown that monotonic EP and cyclic EVP had no significant effect on the ∆COD, mainly due to the small-scale yielding conditions. It is however observed that the cyclic constitutive law was the best suitable model for the crack tip plasticity effect
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Taleb, Wissam. "Influence de l'historique du chargement sur la fermeture induite par la plasticité et la forme d'une fissure de fatigue." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2021. http://www.theses.fr/2021ESMA0003.

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L'objectif de cette étude est de fournir un outil numérique prédictif tridimensionnel de l'évolution de la courbure du front de fissure lors de la propagation d'une fissure de fatigue en tenant compte de la fermeture de fissure induite par la plasticité. Des tests ciblés effectués sur une éprouvette CT-50 d'acier inoxydable austénitique 304L ont donné la forme stabilisée du front de fissure pour une fissure longue pour différents rapports de charge R et différentes amplitudes ΔK du facteur d'intensité de contrainte (FIC). Afin d'éviter toute influence de l'historique de chargement, une valeur constante de ΔK a été appliquée. Un modèle 3D, utilisant ABAQUS® et le langage de programmation PYTHON a été développé Un contact sans frottement est placé sur le plan de la fissure pour prendre en compte le phénomène de fermeture.Plusieurs forces motrices de fissure ont été étudiées, selon des hypothèses de mécanique de la rupture élastique linéaire ou élastoplastique. Dans un premier temps, deux calculs parallèles sont effectués (élastique et plastique), afin de mesurer, sur chaque nœud du front de fissure courant, la valeur de l’amplitude effective locale du facteur d’intensité de contraintes, amplitude considérée comme force motrice dans ce premier cas. Dans ce cadre, plusieurs méthodes de calcul du facteur d'intensité de contraintes local le long du front de fissure ont été mises en œuvre, car une étude précédente [1] avait clairement montré que la méthode Shih et Asaro utilisée par ABAQUS® ne permet pas de rendre compte correctement des effets de bord libre. Il ressort qu’un calcul du facteur d’intensité de contraintes se basant sur le champ de contraintes au voisinage de la fissure conduit à des résultats plus précis le long du front de fissure et présente surtout l’avantage considérable de ne faire aucune hypothèse d'évolution de l'état de contraintes sur toute l'épaisseur de l'éprouvette. De plus, d'autres forces motrices élastoplastiques sont également étudiées: l’ouverture plastique en fond de fissure, et le facteur d'intensité de déformation.La propagation du front de fissure est obtenue numériquement par des avancées successives en chaque nœud du front, le long de l'épaisseur, à l'aide de lois de propagation associées à ces différentes forces motrices. Une procédure de remaillage est alors mise en place, et de nombreuses étapes sont effectuées, avec reconstruction à chaque étape du sillage plastique. Différentes conditions de stabilisation sont introduites, permettant une comparaison des formes de front de fissures stabilisées expérimentales et prédites pour les différentes forces motrices. La discussion qui en découle souligne les améliorations apportées, mais également les limitations, ce qui amène naturellement l’auteur à proposer des perspectives
The objective of this study is to provide a three-dimensional predictive numerical tool of the evolution of the curvature the crack front during the propagation of a fatigue crack, taking into account the plasticity induced crack closure. Targeted testing performed on a CT-50 austenitic 304L stainless steel specimen monitored the stabilized crack front shape for a long crack for different load ratios R and different amplitudes ΔK of the stress intensity factor (FIC). In order to avoid any influence of the loading history, a constant value of ΔK has been applied. A 3D model, using ABAQUS® and PYTHON programming language has been developed. A contact without friction is placed on the plane of the crack to take into account the phenomenon of closure.Several driving forces of crack were studied, according to assumptions of linear elastic or elastoplastic fracture mechanics. Initially, two parallel simulations are carried out (elastic and plastic), in order to measure, on each node of the current crack front, the value of the local effective range of the stress intensity factor considered as the driving force in this first case. In this context, several methods of calculating the local stress intensity factor along the crack front were implemented because a previous study [1] had clearly shown that the Shih and Asaro method used by ABAQUS® does not allow to correctly account for free surface effects. It appears that the calculation of the stress intensity factor, based on the stress field in the vicinity of the crack leads to more precise results along the crack front and above all, has the considerable advantage of not making any assumption d evolution of the stress state over the entire thickness of the test specimen. In addition, other elastoplastic driving forces are also studied: the plastic opening displacement at the crack tip, and the strain intensity factor.The propagation of the crack front is obtained numerically by successive advances on each node of the front, along the thickness, using propagation laws associated with these different driving forces. A remeshing procedure is then implemented, and many steps are performed, with reconstruction at each step of the plastic wake. Different stabilization conditions are introduced, allowing a comparison of experimental and predicted stabilized crack front shapes for the different driving forces. The ensuing discussion highlights the improvements made, but also the limitations, which naturally leads the author to propose further perspectives
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Book chapters on the topic "Crack tip plasticity"

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Perez, Nestor. "Crack Tip Plasticity." In Fracture Mechanics, 187–225. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-24999-5_5.

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Hartmaier, Alexander, and Peter Gumbsch. "Discrete Dislocation Dynamics Simulation of Crack-Tip Plasticity." In Continuum Scale Simulation of Engineering Materials, 413–27. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527603786.ch19.

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Venkatakrishnaiah, S., M. W. Kennett, R. A. Dupuy, and L. R. Dharani. "Crack Tip Plasticity in Unidirectional Metal Matrix Composites." In Fracture of Engineering Materials and Structures, 153–58. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3650-1_20.

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Van Der Giessen, E., and J. Lai. "Temperature Effects on Crack Tip Plasticity in Polymers." In Solid Mechanics and its Applications, 167–76. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/0-306-46936-7_16.

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Tomlinson, Rachel A., and Eann A. Patterson. "Examination of Crack Tip Plasticity Using Thermoelastic Stress Analysis." In Thermomechanics and Infra-Red Imaging, Volume 7, 123–29. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4614-0207-7_16.

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Pantelakis, Sp, and P. Papanikos. "Fatigue Crack Growth Following a Single Overload Based on Crack-Tip Plasticity." In Problems of Fracture Mechanics and Fatigue, 575–77. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-2774-7_125.

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Higashida, Kenji, and Masaki Tanaka. "HVEM/AFM Studies on Crack Tip Plasticity in Si Crystals." In Solid Mechanics and its Applications, 153–62. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-1-4020-2111-4_15.

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Hirsch, P. B. "Crack-Tip Plasticity and Quasi-Brittle Fracture of Single Crystals." In Plastic Deformation of Ceramics, 1–19. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4899-1441-5_1.

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Michot, G., H. Azzouzi, N. Maloufi, M. A. Loyola Oliveira, C. Scandian, and A. George. "Possible Mechanisms for Dislocations Multiplication at, or Close to, a Crack Tip." In Multiscale Phenomena in Plasticity: From Experiments to Phenomenology, Modelling and Materials Engineering, 117–26. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4048-5_9.

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Zhang, Yang, and Vikas Tomar. "Characterization of Crack Tip Plasticity in IN-617 Using Indentation and Nano-Mechanical Raman Spectroscopy." In Fracture, Fatigue, Failure and Damage Evolution, Volume 7, 13–18. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-62831-8_3.

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Conference papers on the topic "Crack tip plasticity"

1

Jing, Peihua, Tariq Khraishi, and Larissa Gorbatikh. "Analytical Solutions of Crack Tip Plasticity Zone Shape for a Semi-Infinite Crack." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-2059.

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In this work, closed-form analytical solutions for the plasticity zone shape at the lip of a semi-infinite crack are developed. The material is assumed isotropic with a linear elastic-perfectly plastic constitution. The solutions have been developed for the cases of plane stress and plane strain. The three crack modes, mode I, II and III have been considered. Finally, prediction of the plasticity zone extent has been performed for both the Von Mises and Tresca yield criterion. Significant differences have been found between the plane stress and plane strain conditions, as well as between the three crack modes’ solutions. Also, significant differences have been found when compared to classical plasticity zone calculations using the Irwin approach.
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Kong, Guangming, Xuexia Gao, Xudong Li, Zhitao Mu, and Tao Liu. "Fatigue small crack propagation analysis of aero-aluminium alloy considering crack tip plasticity." In 2015 International Conference on Materials, Environmental and Biological Engineering. Paris, France: Atlantis Press, 2015. http://dx.doi.org/10.2991/mebe-15.2015.161.

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Glaessgen, Edward, Erik Saether, Jacob Hochhalter, and Vesselin Yamakov. "Modeling Near-Crack-Tip Plasticity at Nano- to Micro- Scales." In 51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
18th AIAA/ASME/AHS Adaptive Structures Conference
12th. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-2733.

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Terfas, Osama A. "Crack Tip Constraint for a Surface Crack Under Fully Plastic Conditions." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77371.

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The development of the crack shape in a thick wall pressure vessel is important in fitness-for-service evaluations such as leak-before-break. In this work the crack tip stress field for surface cracks in a thick plate is investigated using 3-D finite element analyses. The mean stress around the crack from the deepest point to the free surface is investigated for a semi-circular surface breaking crack. A new empirical procedure is developed that allows ductile crack growth to be modelled on the basis of standard deep and shallow cracked fracture toughness test data. In conjunction with this procedure the results show that the crack growth will be suppressed at the deepest segments and the crack will preferentially grow in direction of 45°–70° measured from the deepest point in full plasticity.
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Martin, A. N. "Crack Tip Plasticity: A Different Approach to Modelling Fracture Propagation in Soft Formations." In SPE Annual Technical Conference and Exhibition. Society of Petroleum Engineers, 2000. http://dx.doi.org/10.2118/63171-ms.

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Vaziri, A., H. Nayeb-Hashemi, and H. R. Hamidzadeh. "The Effects of the Crack Surfaces Interaction and the Crack Tip Plasticity on the Dynamic Response of the Circumferentially Cracked Turbo Generator Shafts." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42520.

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Turbo generator shafts are often subjected to complex dynamic torsional loadings, resulting in generation and propagation of circumferential cracks. These cracks can severely affect the vibration characteristics of the shafts. The effects of a circumferential crack, its size and location on the torsional dynamic response of a shaft is obtained, considering the local energy loss at the crack tip due to the cyclic plasticity and the crack surfaces interaction. The crack is taken to be normal to the shaft axis and the shaft is subjected to a harmonic torsional load. The shaft material is assumed to be elastic perfectly plastic. The local flexibility is calculated by evaluating the resistance of the un-cracked region of the shaft to the rotational displacement. The effective damping constant is evaluated by considering the frictional energy loss due to the crack surfaces interaction and energy loss due to the plasticity at the crack tip. The energy loss due to the crack surfaces interaction is evaluated by assuming a pressure distribution between mating fracture surfaces. The pressure distribution parameters are obtained by considering the fracture surface roughness (asperities height and width), and crack opening displacements in Modes I and III. The Energy loss due to the plasticity at the crack tip is related to the plastic zone size. The effects of the applied Mode III stress intensity factor on the energy loss due to the friction and the energy loss due to the plasticity at the crack tip are investigated. The results show that depending on the amplitude of the applied Mode III stress intensity factor, one of these energy losses may dominate the total energy loss. The results further indicate that the vibration characteristics of the shaft are significantly affected by considering these two sources of the local energy loss.
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Reinhardt, Wolf, and Don Metzger. "Comparison of Strip Yield and Net Section Plasticity Models for a Bar in Bending With a Single Edge Crack." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-66238.

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The strip yield model is widely used to describe crack tip plasticity in front of a crack. In the strip yield model the stress in the plastic zone is considered as known, and stress and deformation fields can be obtained from elastic solutions using the condition that the crack tip stress singularity vanishes. The strip yield model is generally regarded to be valid to describe small scale plasticity at a crack tip. The present paper examines the behavior of the strip yield model at the transition to large-scale plasticity and its relationship to net section plasticity descriptions. A bar in bending with a single edge crack is used as an illustrative example to derive solutions and compare with one-sided and two-sided plasticity solutions.
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Noronha, Silvester J., and Heshan P. Gunawardane. "A Dislocation Simulation Approach to Physical Basis of Master Curve." In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61059.

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Discrete dislocation simulations of crack-tip plasticity are used to study the sharp increase in fracture toughness around ductile-brittle transition temperature of ferritic steels. The model used composed of a macrocrack with a microcrack ahead of it in its crack plane. The microcrack represents potential fracture sites at internal inhomogenities, such as brittle precipitates. The simulation has two stages: at first the fracture stress of microcrack, σF is calculated from dislocation simulation of microcrack-tip plasticity. In the next stage the fracture toughness is estimated by the macrocrack tip plasticity simulation; the fracture toughness is applied stress intensity at the macrorack when the tensile stress at the microcrack position attains σF. The brittle-ductile transition curve is obtained by determining the fracture toughness at various temperatures. Factors that contribute to the sharp upturn in fracture toughness with increasing temperature are found to be the increase in dislocation mobility, the decrease in tensile stress ahead of the macrocrack tip due to blunting and increase in mircocrack fracture stress due to increase in plasticity at the microcrack tips. The shape of the curve obtained is similar to the Master Curve.
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Di Carolo, F., R. De Finisi, D. Palumbo, J. M. Vasco-Olmo, F. A. Díaz, and U. Galietti. "Study of the plasticity effect at the crack tip in Titanium by using thermal signal analysis." In 2020 Quantitative InfraRed Thermography. QIRT Council, 2020. http://dx.doi.org/10.21611/qirt.2020.097.

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Chattopadhyay, Somnath. "Fatigue Crack Initiation in Pressure Vessel Steels Using a Distance Parameter." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-2192.

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The propagation behavior of short cracks cannot be studied by linear elastic methods because of large plastic region near the crack tip, as well as a breakdown in correlation of the stress intensity factor with the fatigue crack growth rates. The proposed fatigue design approach incorporates a distance parameter in conjunction with linear elastic fracture mechanics and effectively integrates long and short crack growth test data. This distance parameter is a material constant that allows for the effects of (a) large-scale plasticity, (b) crack closure and (c) fatigue crack threshold. Furthermore, this parameter can be used to successfully predict fatigue crack growth behavior of short cracks. The practical application of this method to study fatigue crack initiation in pressure vessels rests on the concept that initiation occurs only when the material ahead of the crack tip is damaged enough by cyclic straining.
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