scholarly journals G031031 Direct-Current Electric Potential Field Analysis of Plate with Local Wall Thinning of Semi-Ellipsoidal Shape

2013 ◽  
Vol 2013 (0) ◽  
pp. _G031031-1-_G031031-4
Author(s):  
Manabu NOHARA ◽  
Naoya TADA ◽  
Makoto UCHIDA
Keyword(s):  
Direct Current ◽  
Electric Potential ◽  
Potential Field ◽  
Field Analysis ◽  
Ellipsoidal Shape ◽  
Wall Thinning ◽  
Electric Potential Field ◽  
Local Wall Thinning

Analysis of 4” Schedule 160 Pipe With a Wall Thinning Subject to Torsion, Bending and Pressure Loads

2012 ◽  
Author(s):  
Bostjan Bezensek
Keyword(s):  
Pressure Vessel ◽  
Axial Loads ◽  
Modes Of Failure ◽  
Ellipsoidal Shape ◽  
Wall Thinning ◽  
Planar Wall ◽  
Planar Crack ◽  
Current Guidance ◽  
Bending Loading ◽  
Local Wall Thinning

Pipes with local wall thinning can be simultaneously subject to multi-axial loads such as the internal pressure loads, axial loads, bending and torsion (twist) moments. Continued operation of such items makes use of fitness-for-service assessments using codes such as the ASME Boiler and Pressure vessel Code, Section XI. Currently the non-mandatory Appendix C of the Code gives guidance for performing assessment for various modes of failure. However in the current guidance there is no provision for inclusion of the torsion loads for either planar (crack) or non-planar (wall thinning) type flaws under predominant membrane and bending loading. This paper is a continuation of the study reported at the earlier PVP conferences, whereby the intent is to provide guidance on inclusion of small amounts of torsion with the dominant pressure and bending loading for a pipe containing a wall thinning. In this paper the results are reported for a 4″ (100mm) nominal diameter Schedule 160 pipe. Two shapes of the wall thinning are examined; a cylindrical with round edges and an ellipsoidal shape. These are chosen to span a range of real shapes. The limits on the applicability of the equivalent moment, defined as the root of the sum of the squares (RSS) in construction codes is presented in terms of the wall thinning dimensions.

scholarly journals Sunspot Magnetic Fields and High Energy Electrons in Flares

1971 ◽  
Vol 43 ◽  
pp. 390-396
Author(s):  
Tatsuo Takakura
Keyword(s):  
Magnetic Fields ◽  
Electric Potential ◽  
Potential Field ◽  
Large Scale ◽  
Plasma Waves ◽  
High Energy ◽  
Ohmic Loss ◽  
X Ray ◽  
High Energy Electrons ◽  
Electric Potential Field

A balloon observation of an impulsive hard X-ray burst on September 27, 1969 showed the size of the source to be one arc minute or less. It was remarkably smaller than the associated Hα flare with a size of 3 arc min.The efficient acceleration of electrons and the trigger of the flares are suggested to be attributed to a large scale electric potential field caused by a gas motion near the photosphere. The primary cause of the onset of flares would be the acceleration of electrons. The electrons excite plasma waves which make the conductivity lower by several orders, so that the electromagnetic energy I2L stored before the onset of the flare would be suddenly converted into the heat due to the ohmic loss.

Evaluation of semi-ellipsoidal wall thinning on back surface of plate by direct-current potential difference method

2015 ◽  
Vol 6 (6) ◽  
pp. 714-724 ◽  
Author(s):  
Naoya Tada ◽  
Manabu Nohara
Keyword(s):  
Electric Field ◽  
Direct Current ◽  
Difference Method ◽  
Front Surface ◽  
Potential Difference ◽  
Back Surface ◽  
Content Type ◽  
Wall Thinning ◽  
Current Potential ◽  
Local Wall Thinning

Purpose – Local wall thinning is one of serious problems in aged power generating plants. As the thinning grows inside the pipes, it is difficult to detect and evaluate it from the outer surface of pipe. The purpose of this paper is to evaluate the method of semi-ellipsoidal wall thinning geometry on the back surface of flat plate by direct-current potential difference method (DC-PDM) was proposed as a preliminary research for the pipe wall thinning evaluation. The evaluation was performed for the potential difference numerically obtained by finite element method and the results were discussed. Design/methodology/approach – A number of electric field analyses are necessary to evaluate the geometry of local wall thinning. In this study, defect-current modification method (DCMM), which is very fast analysis method based on the formulated solution for the similar thinning geometry, was used. The DCMM enabled the repeated electric field analyses necessary for the evaluation. Findings – The potential difference on the front surface of plate was higher than the other part because of the electric current disturbance by a wall thinning on the back surface. In addition, the distribution depended on the geometry of the wall thinning. In this study, the shape of the thinning was assumed to be ellipsoid, and the width, depth, and length of the thinning were successfully evaluated based on the potential difference distribution on the front surface. Originality/value – Evaluation of local wall thinning geometry was carried out by repeated analyses using DCMM, and the results were successful. This fact suggests that the evaluation of local wall thinning is possible by DC-PDM. The proposed method is going to be extended to the local wall thinning on the inner surface of pipe by geometrical conversion.

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