The use of electric potential drop techniques to detect delamination in a melt‐infiltrated SiC‐based composite

2021 ◽  
Author(s):  
Ankita Gupta ◽  
Yogesh P. Singh ◽  
Gregory N Morscher
Keyword(s):  
Electric Potential ◽  
Potential Drop

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.

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.

Electric Mars: A large trans‐terminator electric potential drop on closed magnetic field lines above Utopia Planitia

2017 ◽  
Vol 122 (2) ◽  
pp. 2260-2271 ◽  
Author(s):  
Glyn Collinson ◽  
David Mitchell ◽  
Shaosui Xu ◽  
Alex Glocer ◽  
Joseph Grebowsky ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Potential ◽  
Potential Drop ◽  
Field Lines

Insight Into Electric Potential Distribution Within Mesoporous Titanium Dioxide Films

2003 ◽  
Vol 68 (9) ◽  
pp. 1596-1604 ◽  
Author(s):  
Renata Solarska ◽  
Robin Morand ◽  
Jan Augustynski
Keyword(s):  
Electric Potential ◽  
Potential Distribution ◽  
Three Dimensional ◽  
Potential Drop ◽  
Band Gap Energy ◽  
Semiconductor Films ◽  
General Observation ◽  
Titanium Dioxide Films ◽  
Wide Debate ◽  
Hole Scavenger

Charge transport and potential distribution in mesoporous semiconductor films operating in an electrolyte, especially those composed of TiO2 nanoparticles, are still the subject of wide debate. Herein we describe a series of experiments, performed under band-gap energy illumination of nanostructured TiO2 films, intended to shed new light on the actual electric potential profile across such three-dimensional electrode. Our approach stems from quite a general observation that addition of various electron acceptors to a solution containing an efficient hole scavenger (e.g., methanol, formic acid) results in a marked drop of the maximum photocurrent at the mesoporous TiO2 film electrodes whatever the applied anodic bias might be. We have chosen an electron acceptor, MV2+ dication, which-due to its negative redox potential, more negative than that of the bottom of conduction band of TiO2 in acidic media - causes a drop of the photooxidation current only in alkaline but not in acidic solutions of hole scavengers. Measurements of the incident photon-to-current efficiencies as a function of wavelength show that the drop of the photocurrent after the MV2+ addition, observed in alkaline formate solution extends practically over the whole range of wavelengths. As the optical penetration depth in TiO2 for the wavelengths close to its band edge is expected to match approximately the chosen film thickness, we can conclude that major part of the electric potential drop in the TiO2 electrode occurs actually close to the back contact.

Effect of Potential on SCC Initiation for Pipeline Steel in near-Neutral PH Solution

2011 ◽  
Vol 239-242 ◽  
pp. 2091-2095
Author(s):  
Zhi Ying Wang ◽  
Jian Qiu Wang ◽  
En Hou Han ◽  
Wei Ke
Keyword(s):  
Strain Rate ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Electric Potential ◽  
Pipeline Steel ◽  
Potential Drop ◽  
Applied Potential ◽  
Neutral Ph ◽  
Rate Testing ◽  
Initiation Stress

The effect of applied potential on the stress corrosion cracking (SCC) initiation of X-70 pipeline steel in near-neutral pH solution has been investigated by using a slow strain rate testing (SSRT) apparatus and electric potential drop (EPD) method. It was found from the SSRT results that the initiation stress decreased with the decrease in the potential from -790mVSCE to -950mVSCE. But the initiation stress increased when the applied potential was at -1100mVSCE and then decreased at -1200mVSCE. The initiation stress also decreased when the anodic potentials were applied to the samples. SEM observations favored the above SSRT results.

Determination of J-R Curves for A285 Carbon Steel Using Normalization Method

2006 ◽  
Author(s):  
X. K. Zhu ◽  
Y. J. Chao ◽  
P. S. Lam
Keyword(s):  
Carbon Steel ◽  
Crack Length ◽  
Electric Potential ◽  
Potential Drop ◽  
Normalization Method ◽  
Resistance Curve ◽  
Drop Method ◽  
Basic Procedure ◽  
Crack Tip Constraint

The normalization method is adopted and extended in this paper to develop J-R curves for standard and nonstandard specimens directly from load versus load-line displacement test data without the need for online crack length measurement. A set of single edge notched bend (SENB) specimens with different crack lengths for an A285 carbon steel are tested according to the guideline of ASTM standard E1820, and the ability of normalization method is then demonstrated in determination of crack-tip constraint-dependent J-R curves for the SENB specimens. The results show that the normalization method can be used to determine J-R curves for the standard as well as nonstandard specimens. The resistance curve procedure and the basic procedure specified in ASTM E1820 are evaluated, and a modified basic procedure is also presented for determining the J-integral. Comparisons of the resulting J-R curves indicate that the modified basic procedure can be equivalent to the resistance curve procedure. To validate the normalization method, the conventional electric potential drop method is used to monitor crack growth and to determine the J-R curves for the A285 steel. Two equations used in the potential drop method, i.e. linear and nonlinear relationships between the crack length and the electric potential, are employed to determine the crack length during the fracture testing. It shows that the J-R curves determined with the normalization method are in good agreement with those based on the potential drop methods for all specimens considered.

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