toe grinding 4

[DRW75]

hey folks,
Couldn't find anything on the subject here, so here goes...

I've always heard that when you are having difficulty getting a weldment to work due to fatigue (i.e. endurance limit is reached too early), toe grinding can be employed which improves the fatigue performance of the particular weldment. I am wondering what the mechanism is behind the additional endurance that the weld gets when it has been treated in this fashion? Is it a matter of internal stress relief from the grinding procedure? If so, i would think a post heat treatment would have a similar effect??

thanks

DRW

 

[prohammy]

Have a look at this pdf, see if it helps

http://library.witpress.com/pdfs/abstracts/SURF93/SURF93004AU.pdf

Kevin Hammond

Mechanical Design Engineer
Derbyshire, UK

 

[metengr]

Simply put, removing undercut at weld toes is like eliminating a pre-existing flaw or surface discontinuity. Weld toe undercut results in local stress intensification. Eliminating this stress riser does not specifically increase the endurance limit, what it does is reduce mean stress effects that results in increased fatigue resistance.

 

[unclesyd]

Adding a little to the above posts it highly desirable to have the grinding striations perpendicular plane generated by the weld toe. If it isn't possible to grind it this direction one needs to resort to finest grinding wheel that will do the job.

 

[gtaw]

I believe the British developed a method of improving fatigue performance of fillet welds by remelting the toes of the welds using GTAW. I don't believe they use any filler metal, i.e., autogenous.

The concept is that there are inherent oxides, slag, and small cracks along the toes of the fillet weld. Remelting the area of the fillet weld toe and adjacent base metal, using GTAW, eliminates many of the small cracks, oxides, and slag.

Best regards - Al

 

[DRW75]

Great info there guys - certainly a topic which always mystified me.

 

[unclesyd]

Improvement in fatigue life seen from removing stress risers at the toe of a filet weld can still be improved by making the filet elipitical with the long side on the weaker member.