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- since 1996 -

Matec Instrument Companies, Inc.
Ultrasonic test instrumentation and systems for scientific research, quality control inspection and production testing applications.
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Technical Discussions
Eric Chen
Engineering,
GE Aviation, China, Joined Nov 2002, 7

Eric Chen

Engineering,
GE Aviation,
China,
Joined Nov 2002
7
09:26 Apr-14-2008
MT for bearing hardening surface

In the past PT was carried out for the hardening surface of bearing. Now some company change to MT with AC yoke. My question is where is the hardening crack starts from? The interface between the harden layer and the parent material or the hardening crack starts from the bearing surface? If the hardening crack starts from the interface between the parent material and hardening layer, DC would be better than AC.

Can some one explain to me?

Thanks!


 
 Reply 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 304

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
304
03:10 Apr-21-2008
Re: MT for bearing hardening surface
----------- Start Original Message -----------
: In the past PT was carried out for the hardening surface of bearing. Now some company change to MT with AC yoke. My question is where is the hardening crack starts from? The interface between the harden layer and the parent material or the hardening crack starts from the bearing surface? If the hardening crack starts from the interface between the parent material and hardening layer, DC would be better than AC.
: Can some one explain to me?
: Thanks!
------------ End Original Message ------------
For production of bearing parts, the surface is probably the most critical surface, but when the bearings have been in service, failure is most likely to originate at the "Hertzian zone", which is just underneath the raceway ( microns to millimetres depending on bearing size, geometry etc). MT with DC should be considered here, but make sure that you can adequately demagnetize the part, else the residual magnetism will attract ferrous particles which can quickly destroy a bearing.

Godfrey



 
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