A Weibull Stress Model to Predict Effects of Weld Strength Mismatch on Cleavage Fracture Toughness

2011 ◽  
pp. 178-178-16
Author(s):  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Weld Strength ◽  
Stress Model ◽  
Weibull Stress

A Weibull Stress Model to Predict Effects of Weld Strength Mismatch on Cleavage Fracture Toughness

2010 ◽  
Vol 7 (2) ◽  
pp. 102508
Author(s):  
Claudio Ruggieri ◽  
S. Kalluri ◽  
R. M. McGaw ◽  
A. Neimitz ◽  
S. W. Dean
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Weld Strength ◽  
Stress Model ◽  
Weibull Stress

The Weibull Stress Model for Predicting Cleavage Fracture in the Ductile-to-Brittle Transition Region

2008 ◽  
Author(s):  
Xiaosheng Gao ◽  
Jason P. Petti ◽  
Robert H. Dodds
Keyword(s):  
Fracture Toughness ◽  
Transition Region ◽  
Cleavage Fracture ◽  
Model Parameters ◽  
Ferritic Steels ◽  
Stress Model ◽  
Brittle Transition ◽  
Ductile To Brittle Transition ◽  
Constraint Effects ◽  
Weibull Stress

Transgranular cleavage fracture in the ductile-to-brittle transition region of ferritic steels often leads to spectacular and catastrophic failures of engineering structures. Due to the strongly stochastic effects of metallurgical scale inhomogenieties together with the nonlinear mechanical response from plastic deformation, the measured fracture toughness data exhibit a large degree of scatter and a strong dependence on constraint. This has stimulated an increasing amount of research over the past two decades, among which the Weibull stress model originally proposed by the Beremin group has gained much popularity. This model is based on weakest link statistics and provides a framework to quantify the relationship between macro and microscale driving forces for cleavage fracture. It has been successfully applied to predict constraint effects on cleavage fracture and on the scatter of macroscopic fracture toughness values. This paper provides a brief review of the research conducted by the authors in recent years to extend the engineering applicability of the Weibull stress model to predict cleavage fracture in ferritic steels. These recent efforts have introduced a threshold value in the Weibull stress model, introduced more robust calibration methods for determination of model parameters, predicted experimentally observed constraint effects, demonstrated temperature and loading rate effects on the model parameters, and expanded the original Beremin model to include the effects of microcrack nucleation.

A Weibull Stress Approach Incorporating the Coupling Effect of Constraint and Plastic Strain in Cleavage Fracture Toughness Predictions

2014 ◽  
Author(s):  
Claudio Ruggieri ◽  
Robert H. Dodds
Keyword(s):  
Fracture Toughness ◽  
Plastic Strain ◽  
Cleavage Fracture ◽  
Coupling Effect ◽  
Crack Size ◽  
Parameter Analysis ◽  
Pressure Vessel Steel ◽  
Fracture Parameter ◽  
Vessel Steel ◽  
Weibull Stress

This work describes a micromechanics methodology based upon a local failure criterion incorporating the strong effects of plastic strain on cleavage fracture coupled with statistics of microcracks. A central objective is to gain some understanding on the role of plastic strain on cleavage fracture by means of a probabilistic fracture parameter and how it contributes to the cleavage failure probability. A parameter analysis is conducted to assess the general effects of plastic strain on fracture toughness correlations for conventional SE(B) specimens with varying crack size over specimen width ratios. Another objetive is to evaluate the effectiveness of the modified Weibull stress (σ̃w) model to correct effects of constraint loss in PCVN specimens which serve to determine the indexing temperature, T0, based on the Master Curve methodology. Fracture toughness testing conducted on an A285 Grade C pressure vessel steel provides the cleavage fracture resistance (Jc) data needed to estimate T0. Very detailed non-linear finite element analyses for 3-D models of plane-sided SE(B) and PCVN specimens provide the evolution of near-tip stress field with increased macroscopic load (in terms of the J-integral) to define the relationship between σ̃w and J. For the tested material, the Weibull stress methodology yields estimates for the reference temperature, T0, from small fracture specimens which are in good agreement with the corresponding estimates derived from testing of much larger crack configurations.

Evaluation of Fracture Toughness Test Data for Multilayer Dissimilar Joint Welds Using a Weibull Stress Model

2012 ◽  
pp. 357-376
Author(s):  
Yasuhito Takashima ◽  
Mitsuru Ohata ◽  
Masaru Seto ◽  
Yoshitomi Okazaki ◽  
Fumiyoshi Minami
Keyword(s):  
Fracture Toughness ◽  
Test Data ◽  
Dissimilar Joint ◽  
Fracture Toughness Test ◽  
Stress Model ◽  
Toughness Test ◽  
Weibull Stress

Predictions of Cleavage Fracture in Welded Components Incorporating Strength Mismatch Effects: A Weibull Stress Based Approach

2010 ◽  
Author(s):  
Claudio Ruggieri
Keyword(s):  
Cleavage Fracture ◽  
Driving Forces ◽  
Failure Strain ◽  
Pipeline Steel ◽  
Strong Support ◽  
Weld Strength ◽  
J Integral ◽  
X80 Pipeline Steel ◽  
Loading Parameter ◽  
Weibull Stress

This work describes the development of a toughness scaling methodology incorporating the effects of weld strength mismatch on crack-tip driving forces. The approach adopts a nondimensional Weibull stress, σ¯w, as a the near-tip driving force to correlate cleavage fracture across cracked weld configurations with different mismatch conditions even though the loading parameter (measured by the J-integral) may vary widely due to mismatch and constraint variations. Application of the procedure to predict the failure strain for an overmatch girth weld made of an API X80 pipeline steel demonstrates the effectiveness of the micromechanics approach. Overall, the results lend strong support to use a Weibull stress based procedure in defect assessments of structural welds.

A Transferability Model for Cleavage Fracture Toughness in Strength Mismatched Welds Using the Weibull Stress Approach

2010 ◽  
Author(s):  
Claudio Ruggieri
Keyword(s):  
Cleavage Fracture ◽  
Driving Forces ◽  
Failure Strain ◽  
Pipeline Steel ◽  
Strong Support ◽  
Weld Strength ◽  
J Integral ◽  
X80 Pipeline Steel ◽  
Loading Parameter ◽  
Weibull Stress

This work describes the development of a toughness scaling methodology incorporating the effects of weld strength mismatch on crack-tip driving forces. The approach adopts a nondimensional Weibull stress, σw, as a the near-tip driving force to correlate cleavage fracture across cracked weld configurations with different mismatch conditions even though the loading parameter (measured by the J-integral) may vary widely due to mismatch and constraint variations. Application of the procedure to predict the failure strain for an overmatch girth weld made of an API X80 pipeline steel demonstrates the effectiveness of the micromechanics approach. Overall, the results lend strong support to use a Weibull stress based procedure in defect assessments of structural welds.

Sign in / Sign up

Export Citation Format

Share Document