where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -

GE Inspection Technologies
Inspection Technologies, a business of the Baker Hughes, a GE company (BHGE IT), is one of the world's leading suppliers of nondestructive testin ...
458 views
Technical Discussions
John Kitzmiller
John Kitzmiller
09:55 Nov-06-2000
magnetic fields!

Does D.C. currrent pick up surface discontinuities as well as
A.C. current? If not then what is the differential?


    
 
 Reply 
 
dave ronson
dave ronson
02:11 Nov-06-2000
Re: magnetic fields!
: Does D.C. currrent pick up surface discontinuities as well as
: A.C. current? If not then what is the differential?

Sure it does. However, AC will find surface indications must easier since it
>is a less penetrating current. Whereas DC has the ability to penetrate the
>material much easier due to the current being Direct and not alternating as
>in AC. The alternating aspect of AC allows the particles to "dance" on the
>surface allowing the particles to attract to a discontinuity much easier.





    
 
 Reply 
 
Michael Trinidad
Consultant,
LMATS Pty Ltd , Australia, Joined Jan 2003, 138

Michael Trinidad

Consultant,
LMATS Pty Ltd ,
Australia,
Joined Jan 2003
138
07:15 Nov-07-2000
Re: magnetic fields!
: : Does D.C. currrent pick up surface discontinuities as well as
: : A.C. current? If not then what is the differential?

AC current passing through a conductor reverses its direction of flow at a regular frequency so that the electron movement is restricted to the surface of the conductor. The higher the frequency at which the current alternates then the greater will be the “skin effect”. As a consequence the magnetic field associated with AC flow is confined at or near the surface of the material.

DC current flows in a constant direction through a conducting material so that the electrons are moving throughout its cross section and length, although the movement is practically negligible at its centre becoming more pronounced as the surface is neared. The effect of passing DC through a conductive material is that the density of the resulting magnetic field is greatest at the surface of the conductor and becomes progressively weaker in a linear manner, as it penetrates towards the centre.

Kindest Regards


Michael Trinidad



    
 
 Reply 
 

Product Spotlight

Sci Aps Z-Series Portable Handheld Analysers

The world’s only handheld analyzer that measures carbon content in stainless (yes even L-grades),s
...
teels, and cast irons. Also accepted for low Si analysis for sulfidic corrosion analysis, and is widely used in the power industry for Cr analysis, for flow accelerated corrosion applications.
>

Navic - Steerable Modular Automated Scanner

The Navic is a modular, motorized, steerable scanner designed to carry multiple attachments used
...
in various scanning and inspection applications. The Navic is capable of weld scanning (girth welds and long seam welds), automated corrosion mapping, and tank scanning.
>

NEW! The PragmaPro Instrument Platform

The PragmaPro is based on a modular cartridge technology and supports various NDT instrument modal
...
ities such as UT, PAUT, ECT and many more. This new platform is based on a machined, powder-coated aluminum frame for shock-proofness, best sealing qualities and maximum heat dissipation. This is practical to extend the outdoor temperature range and/or to extend the power injected in the transducers. The PragmaPro is aiming at a very wide range of applications, such as weld scanning, corrosion mapping and composite testing.
>

HD-CR 35 NDT Computed Radiography System

Portable high-resolution CR scanner for all radiography applications - weld testing, profile images
...
and aerospace. No matter what type of radiographic testing you are performing, the unique TreFoc Technology of the HD-CR 35 NDT imaging plate scanner always guarantees the highest image quality.
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window