A local approach to cleavage fracture modeling: An overview of progress and challenges for engineering applications

Ruggieri, Cláudio; Dodds, Robert H.

doi:10.1016/j.engfracmech.2017.12.021

Cited by 31 publications

(18 citation statements)

References 81 publications

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“…The K q obtained were 29.51, 30.47 and 29.99 MPa.m 1/2 for samples 1 to 3 respectively according ASTM399 standard for fracture toughness. Results show correspondence with those of Rosenthal [34], which were 30.4 MPa.m 1/2 after stress relieving. These results show that even though the stress relieving profile use in this case resulted in a decline in strength, it increased the fatigue life of the samples as presented in Figure 8.…”

Section: Fracture Toughness and Fatigue Crack Growth Rate Analysissupporting

confidence: 78%

The Effect of Stress Relief on the Mechanical and Fatigue Properties of Additively Manufactured AlSi10Mg Parts

Mfusi

Mathe

Tshabalala

et al. 2019

Metals

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The heating and cooling profiles experienced during laser additive manufacturing results in residual stresses build up in the component. Therefore, it is necessary to perform post build stress relieving towards the retention and improvement of the mechanical properties. However the thermal treatments for conventional manufacturing do not seem to completely accommodate these rapid heating and cooling cycles of laser processing techniques such as powder bed fusion. Characterizations such as density measurements on the samples were performed employing the Archimedes principle; hardness testing was performed on the Zwick micro/macro (Hv) hardness tester, SEM and Electron backscatter diffraction (EBSD). Fracture toughness and crack growth was conducted on a fatigue crack machine. All characterization was done after stress relieving of Selective Laser Melting (SLM) produced samples at 300 °C for 2 hrs was performed in a furnace. The mechanical properties appear to be rather compromised instead of being enhanced desirably. As-built SLM produced tensile specimens built in different directions exhibited significantly favorable mechanical properties. However, post stress relieve thermal treatment technique deteriorated the strength while increasing the ductility significantly. Nonetheless, fatigue crack growth and fracture toughness illustrated positive outcome in terms of fatigue life on SLM produced AlSi10Mg components in application.

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Section: Fracture Toughness and Fatigue Crack Growth Rate Analysissupporting

confidence: 78%

The Effect of Stress Relief on the Mechanical and Fatigue Properties of Additively Manufactured AlSi10Mg Parts

Mfusi

Mathe

Tshabalala

et al. 2019

Metals

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“…The Beremin model [ 8 ] was the first local approach to cleavage fracture, that is based on the weakest-link assumption, according to which the macroscopic cleavage event depends on the failure of a single cleavage initiating microcrack. This approximation is considered reasonable for the physical cleavage process, which consists of three main stages—firstly, microcracks initiate at randomly distributed second phase particles, assisted by the plastic deformation of the surrounding matrix; next, some microcracks propagate across the particle-matrix interface (alternatively, they can form voids, determined by the local mechanical conditions); and finally, cleavage occurs when a single microcrack propagates across the matrix without being arrested at a grain boundary [ 19 , 20 ]. From a statistical point of view, the cleavage process is represented as an inhomogeneous spatial Poisson point process [ 21 ] with points corresponding to the cleavage initiators (CI).…”

Section: Methodsmentioning

confidence: 99%

Incorporation of Obstacle Hardening into Local Approach to Cleavage Fracture to Predict Temperature Effects in the Ductile to Brittle Transition Regime

2021

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Ductile-to-brittle-transition refers to observable change in fracture mode with decreasing temperature—from slow ductile crack growth to rapid cleavage. It is exhibited by body-centred cubic metals and presents a challenge for integrity assessment of structural components made of such metals. Local approaches to cleavage fracture, based on Weibull stress as a cleavage crack-driving force, have been shown to predict fracture toughness at very low temperatures. However, they are ineffective in the transition regime without the recalibration of Weibull stress parameters, which requires further testing and thus diminishes their predictive capability. We propose new Weibull stress formulation with thinning function based on obstacle hardening model, which modifies the number of cleavage-initiating features with temperature. Our model is implemented as a post-processor of finite element analysis results. It is applied to analyses of standard compact tension specimens of typical reactor pressure vessel steel, for which deformation and fracture toughness properties in the transition regime are available. It is shown that the new Weibull stress is independent of temperature, and of Weibull shape parameter, within the experimental error. It accurately predicts the fracture toughness at any temperature in the transition regime without relying upon empirical fits for the first time.

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“…Therefore, the fracture resistance of the material and the shape, size, and direction distribution of carbide particles or impurities in the material determine the failure probability of the material. 14,15 For this reason, the Weibull stress s w is proposed by Beremin group and defined as the two-parameter cumulative failure probability of the driving stress of crack tip extension in the usual sense 7,16…”

Section: Weibull Stress Modelmentioning

confidence: 99%

“…The local crack driving force couples the (local) fracture stress with remote loading (such as the J-integrity) in terms of the Weibull stress s w as a probabilistic fracture parameter directly connected to the statistics of microcracks. Ruggieri and Dodds 7 summarized recent advances in the local approach to cleavage fracture modeling, illustrated by selected examples of application to predict constraint effects on cleavage fracture toughness for typical pressure vessel steels. Qian et al 8 compared crack tip constraints in different specimens and structures with global and local approaches under uniaxial and biaxial loadings.…”

Section: Introductionmentioning

confidence: 99%

Weibull stress analysis for the corner crack in reactor pressure vessel nozzle

Jin

Wang

et al. 2019

Advances in Mechanical Engineering

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The nozzle region of a reactor pressure vessel experiences higher and more complex stresses than the remaining part of the reactor pressure vessel. If a corner crack is postulated in the nozzle region, it is necessary to consider the potential strong influence of constraint on fracture behavior due to inelastic deformations of crack tip. In accordance with the requirement of probabilistic fracture mechanics, Weibull stress in local approach to fracture is analyzed with the consideration of constraint effect. Conventional fracture analysis is also carried out using a three-dimensional crack model, and the fracture driving forces ( KI and J) and T-stress are obtained. Weibull stress along the crack tip is also computed by three-dimensional models. The modified boundary layer model with plastic correction is developed for a corner crack in the reactor pressure vessel nozzle. Under the J- T stress field from three-dimensional models, Weibull stress values obtained using the modified boundary layer model are compared and discussed with that by three-dimensional models. It is found that the modified boundary layer model can effectively predict the Weibull stress under the J- T stress field, which simplified the Weibull stress calculation process for complex structures.

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A local approach to cleavage fracture modeling: An overview of progress and challenges for engineering applications

Cited by 31 publications

References 81 publications

The Effect of Stress Relief on the Mechanical and Fatigue Properties of Additively Manufactured AlSi10Mg Parts

The Effect of Stress Relief on the Mechanical and Fatigue Properties of Additively Manufactured AlSi10Mg Parts

Incorporation of Obstacle Hardening into Local Approach to Cleavage Fracture to Predict Temperature Effects in the Ductile to Brittle Transition Regime

Weibull stress analysis for the corner crack in reactor pressure vessel nozzle

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