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Further developments in a micromechanics model for brittle fracture and applications to the master curve methodology

Grant number: 12/13053-2
Support type:Regular Research Grants
Duration: September 01, 2012 - February 28, 2015
Field of knowledge:Engineering - Mechanical Engineering - Mechanics of Solids
Principal researcher:Claudio Ruggieri
Grantee:Claudio Ruggieri
Home Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil


Single-parameter and two-parameter fracture mechanics methodologies have some well-recognized limitations which motivate development of probabilistic approaches to brittle fracture. Such approaches can be extended in straightforward manner to analyze the mechanical integrity of structural components subjected to more complex loading conditions. In particular, probabilistic procedures incorporating local failure criteria (micromechanics model for brittle fracture) coupled do the finite element method describe the conditions for global structural failure in terms of a (local) probabilistic fracture parameter; these methodologies are most often termed local approaches. To describe brittle fracture driven by transgranular cleavage, a number of models explicitly adopt the "weakest link" theory to derive statistical functions incorporating the local (opening) stresses well at the crack-tip region. Here, the "Weibull stress", Sigma_w, then emerges as an effective crack-tip driving force controlling fracture. This research focuses on the extension and, more importantly, new developments of structural integrity assessment procedures based upon a micromechanics (local) model. A central objective is to develop a more robust procedure for mechanical integrity and fracture analysis of structural materials, including nuclear structural components and reactor pressure vessels, using the Weibull stress (Sigma_w) as the effective crack driving force. However, despite some recent advances in the methodology to characterize fracture toughness in ferritic steels based upon the Weibull stress parameter, several open questions still remain related to its effective application to defect assessment procedures and life extension programmes for in-service structures. Within such context, this research will have particular emphasis on the correlation and prediction of toughness values measured using small-sized precracked Charpy (PCVN) bend specimens to accurately determine the reference temperature, T0, using the Master Curve methodology. (AU)

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Scientific publications (7)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
SARZOSA, DIEGO F. B.; RUGGIERI, CLAUDIO. A numerical investigation of constraint effects in circumferentially cracked pipes and fracture specimens including ductile tearing. INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING, v. 120, p. 1-18, . (13/01139-2, 12/00094-2, 12/13053-2)
RUGGIERI, CLAUDIO; SAVIOLI, RAFAEL G.; DODDS, JR., ROBERT H.. An engineering methodology for constraint corrections of elastic-plastic fracture toughness - Part II: Effects of specimen geometry and plastic strain on cleavage fracture predictions. ENGINEERING FRACTURE MECHANICS, v. 146, p. 185-209, . (12/13053-2)
RUGGIERI, CLAUDIO; DODDS, JR., ROBERT H.. A Modified Weibull Stress Approach to Determine the Reference Temperature in a Pressure Vessel Steel. MATERIALS PERFORMANCE AND CHARACTERIZATION, v. 5, n. 3, p. 260-279, . (12/13053-2)
DE SOUZA, RODOLFO F.; RUGGIERI, CLAUDIO. Revised eta-Factors and J-CTOD Relationships for SE(B) Fracture Specimens Including 3D Effects and Implications for Fracture Toughness Measurements. MATERIALS PERFORMANCE AND CHARACTERIZATION, v. 4, n. 2, SI, p. 34-54, . (12/13053-2)
RUGGIERI, C.; HIPPERT, JR., E.. Delamination effects on fracture behavior of a pipeline steel: A numerical investigation of 3-D crack front fields and constraint. INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING, v. 128, p. 18-35, . (12/13053-2)
SAVIOLI, RAFAEL G.; RUGGIERI, CLAUDIO. Experimental Study on the Cleavage Fracture Behavior of an ASTM A285 Grade C Pressure Vessel Steel. JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME, v. 137, n. 2, . (12/13053-2)

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