The Determination of Single Edge-Notched Bend Specimen Load Line Displacement from Remotely Located Sensors in Elastic-Plastic Fracture Testing

J-Integral is the main effective and commonly used tool for cracked elastic-plastic material resistance assessment. Determination of fracture toughness under impact loading conditions is related with problems of crack length measurement. Nevertheless, current experimental techniques restrict the specimen’s geometry taking into account span and height ratio, which is equal to four. Evaluation of fracture toughness estimation method which requires only experimental load-line displacement curve of single specimen is research object of dynamic fracture mechanics. This article proposes an approach of impact fracture toughness determination of elastic-plastic steel from single any size specimen test. Load-line displacement data obtained from three-point-bending tests of rectangular cross section specimens with V form single edge notch was used for J-integral calculation. Five series of specimens with different geometry were manufactured from ductile steel and tested.

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Applicability of J Estimation Procedures for Overmatched SE(T) Fracture Specimens

ASME 2010 Pressure Vessels and Piping Conference: Volume 6, Parts A and B ◽

10.1115/pvp2010-25121 ◽

2010 ◽

Author(s):

Lenin M. Paredes ◽

Henrique S. S. Carvalho ◽

Claudio Ruggieri

Keyword(s):

Primary Objective ◽

Weld Strength ◽

Evaluation Procedure ◽

Single Edge ◽

Load Line ◽

Load Line Displacement ◽

Edge Notch ◽

Η Factor ◽

Fracture Specimens ◽

J Estimation

This work focuses on the evaluation procedure to determine the elastic-plastic fracture toughness J-integral based upon the η-method for welded SE(T) fracture specimens. The primary objective of this investigation is to address the significance of the η-factor on accurate and robust estimates of J clamped single edge notch tension (SE(T)) specimens using load-displacement records. Very detailed non-linear finite element analyses for plane-strain models provide the evolution of load with increased load-line displacement to define the applied load as a separable function dependent upon crack geometry, strength mismatch level and specimen deformation. The analyses reveal that η-factors for clamped SE(T) fracture specimens based on load-line displacement (LLD) records and plastic area are relatively insensitive to weld strength mismatch.

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Determination of J-Integral Using the Load-COD Record for Circumferential Through-Wall Cracked Pipes

Journal of Pressure Vessel Technology ◽

10.1115/1.2967830 ◽

2008 ◽

Vol 130 (4) ◽

Cited By ~ 3

Author(s):

Nam-Su Huh ◽

Yun-Jae Kim

Keyword(s):

Crack Opening ◽

Estimation Method ◽

J Integral ◽

Opening Displacement ◽

Element Analysis ◽

Load Line ◽

Load Line Displacement ◽

Η Factor ◽

J Estimation

The present paper provides experimental J estimation equation based on the load-crack opening displacement (COD) record for testing the circumferential through-wall cracked pipe under combined tension and bending. Based on the limit analysis and the kinematically admissible rigid-body rotation field, the plastic η-factor for the load-COD record is derived and is compared with that for the load-load line displacement record. Comparison with the J results from detailed elastic-plastic finite element analysis shows that the proposed method based on the load-COD record provides reliable J estimates even for shallow cracks (small crack angle), whereas the conventional approach based on the load-load line displacement record gives erroneous results for shallow cracks. Thus, the proposed J estimation method could be recommended for testing the circumferential through-wall cracked pipe, particularly with shallow cracks.

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Experimental Determination of Elastic and Plastic LLD Rates During Creep Crack Growth Testing

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2017-65685 ◽

2017 ◽

Author(s):

K. M. Tarnowski ◽

C. M. Davies ◽

K. M. Nikbin ◽

D. W. Dean

Keyword(s):

Finite Element ◽

Crack Growth ◽

Creep Crack Growth ◽

Current Method ◽

Creep Crack ◽

Load Line ◽

Load Line Displacement ◽

Final Failure ◽

Complex Crack

Elastic and plastic load line displacement (LLD) rates are often ignored when analyzing Creep Crack Growth (CCG) tests due to difficulties in accurately determining their value for complex crack morphologies typical of creep. Instead, the total LLD rate is assumed to be entirely due to creep. This simplistic approach overestimates the crack tip characterizing parameter C* which is non-conservative. This paper presents a review of the current method of interpreting CCG test data in ASTM E1457 and proposes an improved approach which accounts for the elastic and plastic LLD rates. Estimations of the elastic and plastic LLD rate are obtained from a partial unload immediately after load-up and a full unload, at the end of the test, prior to final failure. Some finite element validation of this method is presented. Implementing this approach will facilitate more realistic CCG laws.

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Relation Between Front-Face and Load-Line Displacements on a C(T) Specimen by Elastic-Plastic Analysis

Volume 1B: Codes and Standards ◽

10.1115/pvp2015-45499 ◽

2015 ◽

Cited By ~ 1

Author(s):

Naoki Miura ◽

Yasunori Momoi ◽

Masato Yamamoto

Keyword(s):

Conversion Factor ◽

Direct Determination ◽

Front Face ◽

Surveillance Program ◽

Irradiation Embrittlement ◽

Element Analysis ◽

Razor Blade ◽

Elastic Plastic ◽

Load Line ◽

Load Line Displacement

The use of miniature C(T) specimens makes it possible for the direct determination of the reference temperature of reactor pressure vessel steels, because they can be taken from the broken halves of the Charpy specimens used for surveillance program to monitor neutron irradiation embrittlement. Fracture toughness tests using C(T) specimens usually need the measurement of load-line displacement, however, it is difficult to mount a clip gauge inside the miniature specimen due to the limitation of the specimen size. A pair of knife edges is machined at the front face of the miniature C(T) specimen to mount a clip gauge with razor blade tips, and the front-face displacement is translated to the load-line displacement. When front-face displacement measurements are made, the load-line displacement can be inferred by multiplying the measured values by the constant 0.73. This conversion factor has been simply derived from the assumption of the linear deformation around a supposed point of rotation. In this study, the conversion factor was directly evaluated by using a three-dimensional elastic-plastic finite element analysis for the miniature C(T) specimens, and the adequacy of the conversion factor was investigated.

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