Predicting the effect of constraint on cleavage and ductile fracture toughness using area contour toughness scaling. (December 2017)

• Record Type: Journal Article
• Authors: Seal, C.K.; Sherry, A.H.
• Is Part Of: Engineering fracture mechanics. Volume 186(2017)
• Page Start: 347
• Page End: 367
• Publication Date: 2017-12
• Subjects: Constraint -- Fracture toughness -- Cleavage -- Ductile -- Onset of upper shelf temperature; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2017.09.029
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: A method for predicting the effect of constraint on fracture is proposed. Look-up tables of R6 constraint parameters for cleavage and ductile fracture presented. Parametrised solutions for R6 constraint parameters are presented. The Anderson and Dodds area scaling method has been extended to Rice and Tracey model. Abstract: The influence of constraint on the fracture toughness properties of materials containing defects has long been recognised. To maintain conservative design and assessment principles, lower bound measurements of fracture properties are commonly used. These are measured using test pieces with a high crack tip constraint. With more accurate design processes and tools becoming more widespread, there is a move toward using more representative properties than these lower bound values. The work presented provides a method that can be used to predict the influence of constraint on the cleavage and ductile fracture toughness of a range of ferritic steels, and hence the associated benefit to the onset upper shelf temperature, defined here as the intersection between the fracture toughness loci associated with 5% cleavage fracture and a 50% ductile initiation probability. The Anderson and Dodds toughness scaling procedure, based on the maximum principal stress, has been used with a range of normalised material tensile properties to generate solutions that allow the constraint benefit to cleavage fracture toughness to be predicted for different ferritic steels. A comparison of predictions with published data shows that this results in conservative predictions, similar to those using the Beremin Weibull stress. For the purposes of predicting constraint benefits to ductile initiation toughness, defined at 0.2 mm stable tearing, the scaling method proposed by Anderson and Dodds was extended to the Rice and Tracey model as a way to provide solutions for the same matrix of tensile properties. This approach was validated against literature data for constraint effects on ductile initiation. Finally, a worked example is provided, showing how the influence of crack tip constraint on the onset upper shelf temperature can be predicted using the solutions provided.