skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Application of a Novel DCPD Adjustment Method for the J-R Curve Characterization: A study based on ORNL and ASTM Interlaboratory Results

Abstract

Material fracture toughness in the fully ductile region can be described by a J-integral vs. crack growth resistance curve (J-R curve). As a conventional J-R curve measurement method, the elastic unloading compliance (EUC) method becomes impractical for elevated temperature testing due to relaxation of the material and friction induced back-up shape of the J-R curve. One alternative solution of J-R curve testing applies the Direct Current Potential Drop (DCPD) technique for measuring crack extension. However, besides crack growth, potential drop can also be influenced by plastic deformation, crack tip blunting, etc., and uncertainties exist in the current DCPD methodology especially in differentiating potential drop due to stable crack growth and due to material deformation. Thus, using DCPD for J-R curve determination remains a challenging task. In this study, a new adjustment procedure for applying DCPD to derive the J-R curve has been developed for conventional fracture toughness specimens, including compact tension, three-point bend, and disk-shaped compact specimens. Data analysis has been performed on Oak Ridge National Laboratory (ORNL) and American Society for Testing and Materials (ASTM) interlaboratory results covering different specimen thicknesses, test temperatures, and materials, to evaluate the applicability of the new DCPD adjustment procedure for J-R curve characterization.more » After applying the newly-developed procedure, direct comparison between the DCPD method and the normalization method on the same specimens indicated close agreement for the overall J-R curves, as well as the provisional values of fracture toughness near the onset of ductile crack extension, Jq, and of tearing modulus.« less

Authors:
 [1];  [1];  [1];  [2]
  1. ORNL
  2. National Institute of Standards and Technology (NIST)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1356913
DOE Contract Number:
AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 17th International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics, Toronto, Canada, 20170510, 20170512
Country of Publication:
United States
Language:
English
Subject:
J-R curve; DCPD; unloading compliance; normalization method; fracture toughness

Citation Formats

Chen, Xiang, Sokolov, Mikhail A, Nanstad, Randy K, and Lucon, Enrico. Application of a Novel DCPD Adjustment Method for the J-R Curve Characterization: A study based on ORNL and ASTM Interlaboratory Results. United States: N. p., 2017. Web.
Chen, Xiang, Sokolov, Mikhail A, Nanstad, Randy K, & Lucon, Enrico. Application of a Novel DCPD Adjustment Method for the J-R Curve Characterization: A study based on ORNL and ASTM Interlaboratory Results. United States.
Chen, Xiang, Sokolov, Mikhail A, Nanstad, Randy K, and Lucon, Enrico. Sun . "Application of a Novel DCPD Adjustment Method for the J-R Curve Characterization: A study based on ORNL and ASTM Interlaboratory Results". United States. doi:.
@article{osti_1356913,
title = {Application of a Novel DCPD Adjustment Method for the J-R Curve Characterization: A study based on ORNL and ASTM Interlaboratory Results},
author = {Chen, Xiang and Sokolov, Mikhail A and Nanstad, Randy K and Lucon, Enrico},
abstractNote = {Material fracture toughness in the fully ductile region can be described by a J-integral vs. crack growth resistance curve (J-R curve). As a conventional J-R curve measurement method, the elastic unloading compliance (EUC) method becomes impractical for elevated temperature testing due to relaxation of the material and friction induced back-up shape of the J-R curve. One alternative solution of J-R curve testing applies the Direct Current Potential Drop (DCPD) technique for measuring crack extension. However, besides crack growth, potential drop can also be influenced by plastic deformation, crack tip blunting, etc., and uncertainties exist in the current DCPD methodology especially in differentiating potential drop due to stable crack growth and due to material deformation. Thus, using DCPD for J-R curve determination remains a challenging task. In this study, a new adjustment procedure for applying DCPD to derive the J-R curve has been developed for conventional fracture toughness specimens, including compact tension, three-point bend, and disk-shaped compact specimens. Data analysis has been performed on Oak Ridge National Laboratory (ORNL) and American Society for Testing and Materials (ASTM) interlaboratory results covering different specimen thicknesses, test temperatures, and materials, to evaluate the applicability of the new DCPD adjustment procedure for J-R curve characterization. After applying the newly-developed procedure, direct comparison between the DCPD method and the normalization method on the same specimens indicated close agreement for the overall J-R curves, as well as the provisional values of fracture toughness near the onset of ductile crack extension, Jq, and of tearing modulus.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2017},
month = {Sun Jan 01 00:00:00 EST 2017}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • Material ductile fracture toughness can be described by J-integral versus crack extension relationship (J-R curve). As a conventional J-R curve measurement method, unloading compliance (UC) becomes impractical in elevated temperature testing due to relaxation of the material and a friction induced back-up shape of the J-R curve. In addition, the UC method may underpredict the crack extension for standard disk-shaped compact (DC(T)) specimens. In order to address these issues, the normalization method and direct current potential drop (DCPD) technique were applied for determining J-R curves at 24 C and 500 C for 0.18T DC(T) specimens made from type 316L stainlessmore » steel. For comparison purchase, the UC method was also applied in 24 C tests. The normalization method was able to yield valid J-R curves in all tests. The J-R curves from the DCPD technique need adjustment to account for the potential drop induced by plastic deformation, crack blunting, etc. and after applying a newly-developed DCPD adjustment procedure, the post-adjusted DCPD J-R curves essentially matched J-R curves from the normalization method. In contrast, the UC method underpredicted the crack extension in all tests resulting in substantial deviation in the derived J-R curves manifested by high Jq values than the normalization or DCPD method. Only for tests where the UC method underpredicted the crack extension by a very small value, J-R curves determined by the UC method were similar to those determined by the normalization or DCPD method.« less
  • The potential benefit of a cyclic postirradiation annealing and reirradiation procedure is investigated as a means of mitigating the progressive embrittlement with irradiation of commercial rector vessel steels. Material characterizations include two representative A533-B weld deposits, each containing a high copper impurity level which is associated with a high sensitivity to radiation. Assessments made on the basis of the J-R curve and tearing modulus show that intermediate annealing at 399 degree C has resulted in a recovery of half of the toughness which was lost with the first irradiation. Subsequent reirradiations, to a total fluence of twice that of themore » initial irradiation, have resulted in no additional loss in toughness, thereby suggesting a concept of embrittlement arrest associated with the annealing procedure.« less
  • The J-R curve behavior of irradiated nuclear pressure vessel steels is characterized in the ductile upper-shelf regime in order to provide a materials basis with which to assess the margin of safety against fracture for water reactor vessels exhibiting a low upper-shelf C /SUB v/ energy. With the single specimen compliance technique, the R-curve is shown to follow a power-law behavior for small crack extension, and this phenomenon has led to a proposed new indexing procedure for J /SUB Ic/. In addition, a specimen size dependence of the R-curve has been suggested by the results of similar compact tension specimensmore » up to 100 mm thick and which have sufficiently deep side grooves to produce a straight crack-front extension. R-curve data are presented in terms of a J versus T instability diagram which couples material and structural parameters, thereby permitting an analysis to be made of the margin against failure in terms of J. Also, a correlation has been suggested between the R-curve parameters and C /SUB v/ shelf energy; this could enhance the structural significance of C /SUB v/ reactor surveillance data.« less
  • The direct current potential drop (DCPD) technique has been applied to derive the J-integral vs. crack growth resistance curve (J-R curve) for fracture toughness characterization of structural materials. The test matrix covered three materials including type 316LN stainless steels, Ni-based alloy 617, and one ferritic-martensitic steel, three specimen configurations including standard compact, single edge bending, and disk-shaped compact specimens, and temperatures ranging from 20 C to 650 C. When compared with baseline J-R curves derived from the ASTM normalization method, the original J-R curves from the DCPD technique yielded much smaller Jq values due to the influence of crack blunting,more » plastic deformation, etc. on potential drop. To counter these effects, a new procedure for adjusting DCPD J-R curves was proposed. After applying the new adjustment procedure, the average difference in Jq between the DCPD technique and the normalization method was only 5.2% and the difference in tearing modulus was 7.4%. The promising result demonstrates the applicability of the DCPD technique for the J-R curve characterization especially in extreme environments, such as elevated temperatures, where the conventional elastic unloading compliance method faces considerable challenges.« less
  • The experimental development is described of a key curve for compact specimens of A533B steel and the use of this experimental key curve to generate the J-Resistance curve directly from the load displacement records without obtaining crack length estimates from unloading compliance, ultrasonics, electric potential or other techniques. Two complete key curve functions were developed, the first using subsized fatique precracked specimens, the second using subsized but machine notched specimens. In each case eight 1/2 T compact specimens with crack lengths from a/W = 0.5 to 0.9 were used to generate a series of digital load displacement records which weremore » assembled in a computer file as the key curve for geometrically similar compact specimens. This key curve can be thought of as defining the locus of load displacement records expected for geometrically similar compact specimens of this material for similar loading conditions if no crack extension were to take place. Deviations between the key curve function and the load displacement record for a particular specimen can then be attributed to crack extension and a calculation for the amount of crack extension can be made. The key curve also allows corrections to be made to J values to account for effects of this crack extension.« less