Impact testing resources

Date 03-03-2015 21:52

I'm not sure a chart is a good idea. Reason: usually the applicable code and/or the Contract Documents/Job Specifications are going to call out the Charpy numbers, not necessarily strictly the material in use. To make a chart gives the test operator room for error. Each specimen should be tested against a unique work order based upon customer PO for the job specs, NOT from a standard chart.

He Is In Control, Have a Great Day, Brent

By MRWeldSoCal (***)

Date 03-03-2015 22:14

I need a chart more for setting the scale of the machine. It has ranges and I would not want to test a part and the scale goes off the chart.

By js55

Date 03-06-2015 18:50

If you can even do such a thing its going to end up a really big chart and not too accurate. There are a lot of materials, and a lot of conditions, and a lot of test temperatures available.

By MRWeldSoCal (***)

Date 03-11-2015 15:50

There has to be some resource for somewhat common impact properties. I just need it say for I am testing CVN's with some HY80, to have the numbers that it roughly breaks at would be helpful in knowing our charpy swing is somewhat accurate. It just hard to find those numbers, even for an estimate.

Jordan

By js55

Date 03-11-2015 16:07

You might try ASM Handbooks Vol 1 and 2
Though they're pricey.

By MRWeldSoCal (***)

Date 03-11-2015 21:45

Ok Brent I have a math question and I dont want to seem like an idiot here but bear with me. Ok so we have an old Charpy here at my work and were trying to calibrate it. Now out max drop height is 48", and we got an average of 170 pounds of force @ -40F on HY100 steel charpys. So to check our machine, we sent out samples to a big time testing lab to run the same test. They however got different results, they averaged 152 pounds of force per 5 samples. I call the company and ask what their drop height is and turns our its more than ours. They are dropping at 60" which would give them lower number due to the higher velocity of the impact. So how can I do a reverse extrapolation of that data just to simply see if we @ 48" are still getting the same number they are at 60"?

By js55

Date 03-12-2015 12:06

MR,
How do you know the charpy samples provide properties consistent enough to do that?

By MRWeldSoCal (***)

Date 03-13-2015 20:23

The only consistency I have is based on the 20 samples I cut and tested. I just figured since at a certain degree we had 5 samples that were very close, and they had samples that were close at the same temp, we could figure if they were comparable. They dropped at 5 feet and ours was at 4. As for calibration, this is an old charpy machine, and is all mechanical and basic. We found another lab that has the same machine as we do so we are send them 5 new sample to break and see if were in the ball park as far as calibration goes.

Thanks for the input though. I was just trying to see if there was in fact a formula to predict velocity to see if there was a relation between drop heights.

Jordan

By js55

Date 03-16-2015 12:01

If what you are looking for is ballpark verification you are fine. My only point is that no matter what you do Charpy impact testing is not exact. There are too many variables.
Not the least of which are:
Microstructural variations (locations of laminations and carbides, etc.).
Notch radius.
Machining speed.
Speed and consistency in physical transfer from the bath to the anvil.
Ambient temperature.

By js55

Date 03-12-2015 12:11

Isn't there an ASTM standard by which you calibrate these machines?
And I would guess you can't do it with charpy samples. There is too much variance in the testing process.

By welderbrent (*****)

Date 03-12-2015 13:57

Charpy tests, tensile pulls, and many other of the tests that labs do beyond the guided bends for welder quals are not to be entered into without much forethought, planning, QC Manual provisions, operator training, and a multitude of reference materials from ASTM, ASNT, AWS and any other applicable organization.

Our AWS Section here in AZ just had a shop tour of PNL Testing Labs in Phoenix. The reference books for what some think is a simple test prove otherwise when it comes to documentation of the test and the resultant report documenting all aspects of the findings. And the training their people have to be able to handle the various departments is not an overnight audio tape to be learned in one's sleep.

It appears you are jumping the gun and need more than just suggestions from those in the know on this forum or a single reference book.

Sorry, you are wanting to know things that are outside my sphere of application, training, and experience.

Brent

By fschweighardt (***)

Date 03-13-2015 22:21

You can call these dudes and buy some known samples

https://www-s.nist.gov/srmors/detail.cfm
Costs a ton but there you go.