Session: CS-21-01 Constraint Effects on C&S

Paper Number: 123456

123456 - Fracture Mechanics Assessment of the Steam-Generator Tube-Sheet Plate Through a Modified Global Approach to Consider the Geometrical Effect on Fracture 

Because of the carbon macro-segregation inherent to the large thickness flat component manufacturing, the Fracture Mechanics Assessment (FMA) of the Steam Generator Tube-Sheet (SG-TS) was required for defects postulated close to the primary (and cladded) surface or the secondary (non-cladded) surface in France.

For those assessments, a defect relying two holes is postulated, which represents a singular configuration compared to conventional FMA. Indeed the defect is relatively small in comparison to the plate thickness and the crack length is limited by the distance between two holes. To take benefit of the geometry effect of this configuration, a methodology based on a modified global approach was proposed [1]. Applications of this methodology predict benefits of loss of constraint for several tubesheet configurations as underclad defect or surface defect with mechanical or thermomechanical loading. Significant constraint effect for underclad defect and moderate effect for surface effect are estimated.

To validate the relevance of this approach, two actions are undertaken:

-        In the first one, this methodology is applied on an experimental data base which different constraint effect . This data base contains numerous fracture tests performed by both EDF and Framatome on various specimen geometries extracted from a 18MND5 low alloy ferritic steel plate, in the brittle-to-ductile transition regime. C (T) , SEN (T) , SEN (B) , and non - standard specimens .

-        In the second one, this application rule is validated through the interpretation of fracture tests performed in the brittle to ductile transition temperature range of specimen representative of a defect between two isthmuses.

The results obtained by this application appear accurate, providing very interesting perspectives for the assessment of the SG-TS, but also the assessment of other configurations such as small surface defects configuration encountering constraint loss (loss of constraint called the small defect effect).

 

[1]       O. Ancelet, S. Marie, S. Chapuliot, A. Parrot, Application of the J-Q methodology to consider the geometrical effect on fracture for large steam generator tubesheet, PVP2023-106269, Atlanta, GA, USA

Presenting Author: Olivier Ancelet Framatome

Presenting Author Biography: I started my career in CEA (Saclay) where I made my PhD on thermal fatigue.
I was hired in CEA in 2006 as a research engineer in the Laboratory for Structural Integrity and Standards (thermal and mechanical studies department).
During that time, I made a lot of mechanical testing on laboratory specimen and quasi structure specimen, analyses, Finite Element Modelling, Codes &
Standards developments… as well as expertise for EDF, FRAMATOME and CEA in the field of fatigue, crack initiation, crack growth and fracture mechanics.
I moved to FRAMATOME in July 2018 where I was hired as a senior expert in fatigue and Fracture Mechanics

Authors:

Olivier Ancelet Framatome
Stéphane Marie Framatome
Stéphane Chapuliot EDF
Aurore Parrot EDF