scholarly journals Extended Investigation of Test Specimen Thickness (TST) Effect on the Fracture Toughness (Jc) of a Material in The Transition Temperature Region as a Difference in the Crack Tip Constraint–what is a loss in Constraint in the TST Effect on Jc?

2014 ◽  
Vol 3 ◽  
pp. 57-62
Author(s):  
Toshiyuki Meshii ◽  
Kai Lu ◽  
Yuki Fujiwara
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Temperature Region ◽  
Test Specimen ◽  
Crack Tip ◽  
Specimen Thickness ◽  
Crack Tip Constraint

Framework to Correlate Test Specimen Thickness Effect on Fracture Toughness With T33-Stress

2011 ◽  
Author(s):  
Toshiyuki Meshii ◽  
Tomohiro Tanaka
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Temperature Region ◽  
Test Specimen ◽  
Crack Tip ◽  
Thickness Effect ◽  
Specimen Thickness ◽  
Out Of Plane ◽  
Elastic Crack ◽  
Crack Tip Constraint

This paper considered the test specimen thickness effect on the fracture toughness of a material Jc, in the transition temperature region, for CT and 3PB specimen. Framework to correlate test specimen thickness effect on fracture toughness with T33-stress, which is the out-of-plane elastic crack tip constraint parameter, was proposed. The results seemed to indicate a possibility of improving the existing methods to correlate the fracture toughness obtained by test specimen with the toughness of actual cracks found in the structure, in use of T33–stress.

Shallow Flaws Under Biaxial Loading Conditions—Part I: The Effect of Specimen Size on Fracture Toughness Values Obtained From Large-Scale Cruciform Specimens1

2000 ◽  
Vol 123 (1) ◽  
pp. 10-24 ◽  
Author(s):  
Wallace J. McAfee ◽  
B. Richard Bass ◽  
Paul T. Williams
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Temperature Region ◽  
Large Scale ◽  
Biaxial Loading ◽  
Crack Tip ◽  
Specimen Size ◽  
Biaxial Stress ◽  
Lower Transition ◽  
Crack Tip Constraint

A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed. This technology is for application to the safety assessment of RPVs containing postulated shallow-surface flaws. It has been shown that relaxation of crack-tip constraint causes shallow-flaw fracture toughness of RPV material to have a higher mean value than that for deep flaws in the lower transition temperature region. Cruciform beam specimens developed at Oak Ridge National Laboratory (ORNL) introduce far-field, out-of-plane biaxial stress components in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock (PTS) loading of an RPV. The biaxial stress component has been shown to increase stress triaxiality (constraint) at the crack tip, and thereby reduce the shallow-flaw fracture toughness enhancement. The cruciform specimen permits controlled application of biaxial loading ratios, resulting in controlled variation of crack-tip constraint. An extensive matrix of intermediate-scale cruciform specimens with a uniform depth surface flaw was previously tested and demonstrated a continued decrease in shallow-flaw fracture toughness with increasing biaxial loading. This paper describes the test results for a series of large-scale cruciform specimens with a uniform depth surface flaw. These specimens were all of the same size with the same depth flaw and were tested at the same temperature and biaxial load ratio (1:1). The configuration is the same as the previous set of intermediate-scale tests, but has been scaled upward in size by 150 percent. These tests demonstrated the effect of biaxial loading and specimen size on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. For specimens tested under full biaxial (1:1) loading at test temperatures in the range of 23°F (−5°C) to 34°F (1°C), toughness was reduced by approximately 15 percent for a 150-percent increase in specimen size. This decrease was slightly greater than the predicted reduction for this increase in specimen size. The size corrections for 1/2T C(T) specimens did not predict the experimentally determined mean toughness values for larger size shallow-flaw specimens tested under biaxial (1:1) loading in the lower transition temperature region.

Validating the Mechanical Nature of the Test Speicmen Thickness Effect on Fracture Toughness in the Transition Temperature Region

2013 ◽  
Author(s):  
Toshiyuki Meshii ◽  
Kai Lu ◽  
Ryota Takamura
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Temperature Region ◽  
Standard Test ◽  
Thickness Effect ◽  
Specimen Thickness ◽  
Weakest Link ◽  
Standard Specimens ◽  
Out Of Plane ◽  
Crack Tip Constraint

This paper considered the test specimen thickness (TST) effect on the fracture toughness of a material Jc, in the transition temperature region, for 3PB (i.e., SE(B) for ASTM standard) specimens. Fracture toughness tests and elastic-plastic finite element analyses (FEA) with non-standard test specimens, on the point that the specimen thickness to width to ratio B/W was varied in the range of 0.25 to 1.5, were conducted. Based on these tests and FEA results, it was demonstrated that Jc showed tendency to saturate to some lower bound for B/W = 1.5. This tendency was similar with that predicted by our previous work, which assumed the TST effect on Jc as an out-of-plane crack-tip constraint issue. Because the TST effect on Jc (such as Jc ∝ B(−1/2)) together with Jc’s bounding nature for large B could not be predicted by the weakest link model but out-of-plane constraint assumption worked, it was concluded that the TST effect is mainly mechanical in nature.

Formulating Test Specimen Thickness Effect on Fracture Toughness With T33-Stress: Case of 3PB Test Specimen

2010 ◽  
Author(s):  
Tomohiro Tanaka ◽  
Toshiyuki Meshii
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Carbon Steel ◽  
Test Specimen ◽  
Thickness Effect ◽  
Specimen Thickness ◽  
Out Of Plane ◽  
Elastic Crack ◽  
Experimental Expression ◽  
Crack Tip Constraint

This paper considered the test specimen thickness effect on the fracture toughness of a material, in the transition temperature region, for 3PB specimen. Then, the thickness effect on the T33-stress, which is the out-of-plane elastic crack tip constraint parameter, was studied. Finally, an experimental expression on the thickness effect on the fracture toughness by using T33-stress was proposed for 0.55% carbon steel S55C. The results seemed to indicate a possibility of improving the existing methods to correlate the fracture toughness obtained by test specimen with the toughness of actual cracks found in the structure, in use of T33-stress.

scholarly journals Application ofT33-Stress to Predict the Lower Bound Fracture Toughness for Increasing the Test Specimen Thickness in the Transition Temperature Region

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Kai Lu ◽  
Toshiyuki Meshii
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Lower Bound ◽  
Temperature Region ◽  
Test Specimen ◽  
Specimen Thickness ◽  
Vessel Steel ◽  
Out Of Plane ◽  
New Finding ◽  
Ductile To Brittle Transition

This work was motivated by the fact that although fracture toughness of a material in the ductile-to-brittle transition temperature regionJcexhibits the test specimen thickness (TST) effect onJc, frequently described asJc∝(TST)-1/2, experiences a contradiction that is deduced from this empirical formulation; that is,Jc= 0 for large TST. On the other hand, our previous works have showed that the TST effect onJccould be explained as a difference in the out-of-plane constraint and correlated with the out-of-planeT33-stress. Thus, in this work, the TST effect onJcfor the decommissioned Shoreham reactor vessel steel A533B was demonstrated from the standpoint of out-of-plane constraint. The results validated thatT33was effective for describing theJcdecreasing tendency. Because the Shoreham data included a lower boundJcfor increasing TST, a new finding was made thatT33successfully predicted the lower bound ofJcwith increasing TST. This lower boundJcprediction withT33conquered the contradiction that the empiricalJc∝(TST)-1/2predictsJc= 0 for large TST.

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