Electrical potential drop method for evaluating crack depth

1991 ◽  
Vol 47 (1) ◽  
pp. 25-38 ◽  
Author(s):  
K. Ikeda ◽  
M. Yoshimi ◽  
C. Miki
Keyword(s):  
Crack Depth ◽  
Electrical Potential ◽  
Potential Drop ◽  
Drop Method

Determination of J-R Curves for Dissimilar Metal Welds Using Normalization Method and Compact Tension Specimens

2013 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Do-Jun Shim ◽  
Paul Scott ◽  
David Rudland
Keyword(s):  
Fracture Resistance ◽  
Crack Extension ◽  
Electrical Potential ◽  
Potential Drop ◽  
Compact Tension ◽  
Normalization Method ◽  
Drop Method ◽  
Dissimilar Metal ◽  
Standard Procedures ◽  
Resistance Curves

Normalization method is adopted in this paper to determine fracture resistance curves, i.e. J-R curves for dissimilar metal (DM) welds involved in nuclear reactor pressure vessels. Due to the restriction of material availability, three compact tension (CT) specimens containing a DM weld with a crack were utilized and tested under the guideline of ASTM fracture toughness test standard E1820 [1]. The test data of load versus load-line displacement were recorded during the tests, and directly applied to estimate crack extension using the normalization procedures. The J-R curves are then developed without the need of online crack extension measurement. Three J-R curves of DM welds were obtained using the standard 1T CT specimens and the normalization method. These resistance curves were evaluated through comparison with those obtained from small sized ½T CT specimens via ASTM E1820 standard procedures and those obtained from the electrical potential drop method. The results showed that the normalization method, ASTM E1820 standard procedures, and the electrical potential drop method can determine similar fracture resistance curves for DM welds in a good agreement. Among the three methods, the normalization method is of most attractive because it is the only one that does not need crack extension measurements, and thus test costs are saved.

scholarly journals Measuring the depth of surface cracks using alternating current potential drop technique, with suppression of the influence of the electromagnetic properties of the metal

2021 ◽  
Vol 2091 (1) ◽  
pp. 012047
Author(s):  
P N Shkatov
Keyword(s):  
Crack Depth ◽  
Potential Drop ◽  
Alternating Current ◽  
Measurement Range ◽  
Electromagnetic Properties ◽  
Surface Cracks ◽  
Measuring Techniques ◽  
Drop Technique ◽  
Current Potential

Abstract Traditional measuring techniques often lead to errors due to the need to register signals in both defective and defect-free areas. In this paper, we introduce an alternating current potential drop technique with detuning from the influence of variations in the electromagnetic properties of the metal achieved by registering a signal only at the defective site. We show that, with an appropriate choice of measurement parameters, the use of the proposed technique leads to an increase in sensitivity to the crack depth as well as to an increase in the measurement range.

Four Points Bending Tests on Large Scale Welded Pipes Containing a Through-Wall Defect: Fatigue and Fracture Analysis

2014 ◽  
Author(s):  
M. Bourgeois ◽  
T. Le Grasse ◽  
Y. Kayser
Keyword(s):  
Large Scale ◽  
Structural Integrity ◽  
Atomic Energy Commission ◽  
Electrical Potential ◽  
Potential Drop ◽  
Small Scale ◽  
Butt Weld ◽  
Bending Tests ◽  
Scale Test ◽  
Fracture Tests

Within the framework of European project STYLE (Structural integrity for lifetime management), fracture tests on two large scale pipes containing a through wall crack have been performed. Two Mock-ups have been tested: MU1 is a narrow gap Inconel Dissimilar Metals, provided and designed by AREVA France, and MU2 is a an austenitic steel butt-weld with a thermally aged weld repair austenitic weld, provided by EDF British Energy. The four-points bending tests were carried out by the French Alternative Energies and Atomic Energy Commission (CEA), in order to study the mechanical properties and integrity of component such as welding pipes. A through wall crack was machined in the both pipes. After a fatigue pre-cracking step carried out at RT, the monotonic fracture test was performed (at 300°C on MU1). Optical camera and Electrical Potential Drop Method have allowed following the crack growth during fatigue and final fracture stages. The observations made post-mortem showed ductile tearing of a few millimeters in those pipes. The first part of this paper is devoted to the four-points bending tests. The second part of this paper deals with first numerical analysis related to the Mock-up-1. Previous results concerning the mechanical characterizations of the constitutive materials are discussed. Fracture mechanics small scale specimens are interpreted using FE Analysis to obtain the fracture parameters used in global approaches. First computation is shown on the Mock-up-1 in order to predict the behavior of the large scale test mechanical and fracture behavior.

The Influence of Creep Strain on Crack Length Measurements Using the Potential Drop

2015 ◽  
Author(s):  
K. M. Tarnowski ◽  
C. M. Davies ◽  
K. M. Nikbin ◽  
D. W. Dean
Keyword(s):  
Stainless Steel ◽  
Crack Growth ◽  
Material Properties ◽  
Crack Extension ◽  
Electrical Potential ◽  
Creep Crack Growth ◽  
Potential Drop ◽  
Fe Model ◽  
Creep Properties ◽  
Length Measurements

One of the most common methods for estimating crack extension in the laboratory is electrical potential drop (PD). A key limitation of this technique is that it is sensitive to strains at the crack tip as well as crack extension. When producing J-R curves the onset of crack growth may be identified from a point of inflection on a plot of PD vs. CMOD. For creep crack growth (CCG) tests however, the effects of strain are often ignored. This paper investigates whether a similar method may be applied to CCG testing. A single CCG test was performed on type 316H stainless steel and a point of inflection, similar to that observed during J-R curve testing was identified. A finite element (FE) based approach was used to investigate this phenomenon further. A 3D sequentially-coupled structural-electrical FE model was used to reproduce the experimental PD vs. CMOD plot up to the point of inflection. The model was capable of predicting the general relationship between strain and PD. It predicted the magnitude of the change in PD to within 30%. A simplified 2D FE model was then used to perform a parametric study to investigate whether a similar trend may be expected for a range of materials. Power law tensile and creep properties were investigated with stress exponents of 1, 3 and 10. The results confirm that a point of inflection should be observable for the range of material properties considered.

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