An electric potential drop technique for characterizing part-through surface cracks

1992 ◽  
Vol 191-194 ◽  
pp. 1038-1041 ◽  
Author(s):  
M. Enmark ◽  
G. Lucas ◽  
G.R. Odette
Keyword(s):  
Electric Potential ◽  
Potential Drop ◽  
Surface Cracks ◽  
Drop Technique

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.

DC Potential Drop Technique Selecting Probes Distances Properly for Sizing Deep Surface Cracks

2005 ◽  
Author(s):  
Fumio Takeo ◽  
Masumi Saka ◽  
Seiichi Hamada ◽  
Manabu Hayakawa
Keyword(s):  
Power Plants ◽  
Potential Drop ◽  
Small Crack ◽  
Surface Cracks ◽  
Structural Components ◽  
Deep Surface ◽  
Close Proximity ◽  
Current Input ◽  
Quantitative Nde ◽  
Drop Technique

D-C potential drop (DCPD) technique is a powerful tool for quantitative NDE of cracks. The technique using four probes which are in close proximity to each other has been proposed for NDE of surface cracks; that is the closely coupled probes potential drop (CCPPD) technique. It has been shown that the sensitivity of CCPPD technique to evaluate a small crack is enhanced significantly in comparison with the usual method. On the other hand, since CCPPD technique has been developed to evaluate a small crack sensitively, it is not fit to evaluate deep cracks which are sometimes found in the structural components of power plants. The objective of this study was to enhance the sensitivity of evaluating deep surface cracks. By extending the distance between current input and output probes, the change in potential drop with the change in the depth of deeper crack becomes large. But the voltage of potential drop becomes small to measure, because the current density in the material becomes low. The voltage of the potential drop can be increased by increasing the applying current, but the current would also be limited by the equipment or contacting probes. Then the way to select the appropriate distances between probes from the viewpoints of the sensitivity and the required current has been shown.

General Rule of Method for Measurement of Thickness and Crack Size by Electric Potential Drop Technique: Outline of the NDIS3426:2008

2009 ◽  
Author(s):  
Yang Ju ◽  
Seiichi Hamada
Keyword(s):  
Fatigue Crack ◽  
Electric Potential ◽  
General Rule ◽  
Potential Drop ◽  
Crack Size ◽  
Pulsed Direct Current ◽  
Measurement Of Thickness ◽  
Drop Technique ◽  
Direct Current Potential Drop ◽  
Current Potential

The Japanese Society for Non-Destructive Inspection (JSNDI) published general rule of method for measurement of thickness and crack size by Electric Potential Drop Technique as the Standard of JSNDI (NDIS3426) in January, 2008. NDIS3426 was established based on the researches for many years including the round robin tests conducted as the academic activities in JSNDI, and the previous technical guideline and standard ASTM E-647-05 ANNEX A6 and BS ISO 12108:2002 established for the measurement of fatigue crack growth in specimens. In this paper, the outline and the background of NDIS3426 was described. The electric potential drop technique is one of the promising methods to monitor or measure the thickness and crack size for the practical use in many industries. For the inspection of the surface deep fatigue crack in the steam turbine casing, the advanced crack depth indicator based on the potential drop technique has been applied. For the monitoring the creep damage accumulated in the seam-welded power piping, the commercialized tool based on the pulsed direct current potential drop technique has been used. For the pipe wall thinning measurement in the operating thermal power plant, the pulsed direct current potential drop technique was applied. This paper shows the present condition of the practical use and the future prospect of the potential drop technique.

Selecting Suitable Probes Distances for Sizing Deep Surface Cracks Using the DCPD Technique

2006 ◽  
Vol 129 (1) ◽  
pp. 205-210 ◽  
Author(s):  
Fumio Takeo ◽  
Masumi Saka ◽  
S. Reaz Ahmed ◽  
Seiichi Hamada ◽  
Manabu Hayakawa
Keyword(s):  
Three Dimensional ◽  
Potential Drop ◽  
Surface Cracks ◽  
Deep Surface ◽  
Input And Output ◽  
Wide Range ◽  
Current Input ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
The Way

In this study, the way to enhance the sensitivity of evaluating deep surface cracks by DCPD technique using four probes is considered. The potential drops across two-dimensional cracks having different depths are analyzed by the three-dimensional finite-element method. The effect of the distance between current input and output probes and the distance between measuring probes on the change in potential drops are analyzed for a wide range of crack depths. By extending the distance between current input and output probes, the change in potential drop with the change in the depth of deeper crack becomes large. But the voltage of potential drop becomes small to measure. Finally, the way to select the appropriate distances between the probes for the measuring sensor is shown from the viewpoints of sensitivity and the required current.

Electric Potential Drop Method for Evaluating Crack Initiation and Crack Propagation: The Help of FE Simulation

2019 ◽  
Author(s):  
Patrick Le Delliou
Keyword(s):  
Electrical Resistivity ◽  
Plastic Strain ◽  
Electric Potential ◽  
Thermal Conduction ◽  
Voltage Drop ◽  
Potential Drop ◽  
Metallic Materials ◽  
Ductile Tearing ◽  
Practical Applications ◽  
Plastic Case

Abstract The electric potential drop (EPD) method is a laboratory technique to monitor the initiation and the propagation of a crack, mainly in the field of fatigue research. It can also be used in fracture experiments, involving plasticity and large deformations. The size of a crack in a metallic member is predicted by applying a constant d.c. (direct current) or a.c. (alternating current) to the member and by measuring an increase in electric resistance due to the crack. Practically, several pairs of probes are attached to the specimen crossing over the crack and the voltage drop is measured periodically along the test. The main difficulty is to correlate the EPD changes to the crack extension. Thanks to the analogy between the thermal conduction problem and the electrical conduction problem, a classical thermo-mechanical finite element solver can be used to predict the EPD along a crack, given the electrical resistivity of the material, the current intensity and the geometry of the structure and of the crack. This technique works well for fatigue studies, where the structure remains elastic and whose shape is unchanged. However, in fracture experiments, the change in geometry and the possible effect of the plastic strain on electrical resistivity make the problem much more complex. The paper presents the principle of the EPD method, a work on the effect of the plastic strain on the electrical resistivity, FE computations for the elastic case (for fatigue pre-cracking) and for the plastic case (for ductile tearing experiments). Several practical applications will be presented on various metallic materials.

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