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Teletest
Teletest Focus+ was the first system to use long-range guided wave ultrasonic testing to detect corrosion in pipelines.
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Technical Discussions
XiangYan
XiangYan
06:51 Sep-05-2008
coercive force

is the coercive force depend on the shape ? Provided two samples are made of the same material but different shape, you measure their coercive force could you end up with different results ?



    
 
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Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 847

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
847
07:24 Sep-05-2008
Re: coercive force
In one word, YES! The lower the L/D Ratio (Length to Diameter), greater is the Coercive Force required to demagnetise the item. But shape is not the only factor. You also have to take into account such properties as heat treatment and alloying.

Cheerio's
Michel

----------- Start Original Message -----------
: is the coercive force depend on the shape ? Provided two samples are made of the same material but different shape, you measure their coercive force could you end up with different results ?
------------ End Original Message ------------




    
 
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Catalin Mandache
Catalin Mandache
06:03 Sep-08-2008
Re: coercive force
The coercive force depends on so many micro structural factors that is very unlikely to have the same values for two identically shaped and alloyed samples.

----------- Start Original Message -----------
: is the coercive force depend on the shape ? Provided two samples are made of the same material but different shape, you measure their coercive force could you end up with different results ?
------------ End Original Message ------------




    
 
 Reply 
 
David Mackintosh
Engineering,
Acuren Group Inc., Canada, Joined Feb 2011, 85

David Mackintosh

Engineering,
Acuren Group Inc.,
Canada,
Joined Feb 2011
85
09:36 Sep-23-2008
Re: coercive force
----------- Start Original Message -----------
: is the coercive force depend on the shape ? Provided two samples are made of the same material but different shape, you measure their coercive force could you end up with different results ?
------------ End Original Message ------------

The coercive force, Hc, is the applied field required to demagnetize a material after saturation. It is a material property. (See for example http://www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/HysteresisLoop.htm and http://en.wikipedia.org/wiki/Coercive_force.) The magnetic H-field required to demagnetize a specific object depends on the material properties, the shape of the object, and the method of applying the field, among other things. Hc for the material and the demagnetizing force required for a specific object are related, but it is not always easy to calculate one from the other.

David



    
 
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