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Up Topic Welding Industry / Technical Discussions / Who wants to talk Charpy?
- - By MRWeldSoCal (***) Date 12-01-2014 23:21
Getting into Charpy V notch impact testing, been using E23-07 to get the basics along with lots of other readings.  When it comes to set drop heights where do I look for information?  Anyone out there care to share with helpful pointers and tips?

Maxwell
Parent - - By js55 (*****) Date 12-02-2014 15:58
Not sure what you mean by drop heights.
Parent - - By MRWeldSoCal (***) Date 12-02-2014 17:14
The Charpy Can adjust from 24 inches to 48 inches, Im pretty sure 48" is the magic number for all of it but Im trying to find people with experience in this type of weld testing.  Looking like a ghost town in the Charpy department of the forum.

J Max
Parent - By js55 (*****) Date 12-02-2014 17:42
What does E-23 say pertaining to this?
And keep in mind the intent of the CVN is to measure 'rapid' fracture conditions. Given this the 48 inch would seem to me a more rapid fracture.
Parent - - By S J (**) Date 12-02-2014 20:47
Do you have access to a current copy of the ASTM test method specification as well as the welding code you must certify to?  The ASTM website lists the PDF price at around $65.

Typically, welding codes specify the certification technical requirements, and test specifications specify the methods and procedures for examination of the weld certification test specimens.

That said, for some codes and/or materials, the V-notch impact tests might require low temperature tests -to certify impact resistance which decreases at lower temperatures.

However, js55 offers a wise reply in stating that 48" would be a more severe test than 24" - but, you are only obligated to certify to the minimum engineering technical requirements.

Also, in years past, some V-notch tests were conducted by using a swinging pendulum to impact the test specimens.  Are you using a swinging pendulum or a vertical drop weight onto a horizontal specimen?  The second method is new for some of us, so you would be wise to consult the ASTM publication for guidance as well as a certified test lab and/or some test equipment vendors.
Parent - - By MRWeldSoCal (***) Date 01-06-2015 00:00
been on vacation for the last 3 week traveling.  Yes is a swinging weighted arm much like an IZOD test but the specimen is laid horizontally in an anvil.  We picked up the ASTM spec, But was wondering if any of you have any time behind it and can share some tips.

Jordan
Parent - - By js55 (*****) Date 01-06-2015 17:06
Can't help much with the machine aspects however the most critical variable for the success of CVN's is notch radius.
Parent - - By fschweighardt (***) Date 01-07-2015 03:37
Somewhere around here, I had an article that discussed the results of a Charpy test, comparing the effects of fly-cuting the notch vs broaching.  If I remember, fly-cut samples went about 5-10% lower on energy absorbed.  Gotta look for that, may even be online somewhere
Parent - - By js55 (*****) Date 01-07-2015 18:53
Let us know.
Parent - By fschweighardt (***) Date 01-07-2015 19:20
Turns out I was wrong, as usual.  The article compares grinding the notch to broaching.  also, the variation is slight, and probably not statstically significant.

https://books.google.com/books?id=Pqcesk8iZzMC&pg=PA92&lpg=PA92&dq=charpy,+grinding,+broaching&source=bl&ots=AMTL40Vdis&sig=A4T6D9lBNmfviZ6C-bZDxTEkUDQ&hl=en&sa=X&ei=loWtVMauMIr7yATurIDAAg&ved=0CEgQ6AEwAw#v=onepage&q=charpy%2C%20grinding%2C%20broaching&f=false

And some infor from NIST
5.3.2 Machining requirements
The dimensional requirements for NIST verification
specimens, given in Table 6, meet or exceed the
ASTM E 23 specifications. This minimizes variations
in impact energy due to physical variations in the
specimens. Also, the notch centering and the length
tolerance for NIST specimens are equivalent to the ISO Standard 164, which permits the specimens
to be used in impact machines with end-centering devices. The NIST requirement for
surface finish is also equivalent to the ISO 164 requirement. All of these dimensional requirements
can be met with standard machining practices.
Specimen notches are form ground on a surface grinder (machining with a fly cutter or multitooth
cutter is not permitted). To avoid "burning" or cold working the material at the base of the
notch, the next to the last cut is required to remove more than 0.25 mm and less than 0.38 mm
and the final cut must not remove more than 0.12 mm. When the specimens are finished and
ready for shipment, they are given a protective coating of oil.
Up Topic Welding Industry / Technical Discussions / Who wants to talk Charpy?

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