CVN impact data calculation 1

[Elnur250774]

Hi, I have ISO corner fittings with parameters of CVN of 27J at -20 deg. Client requires CVN at -40 deg. What is acceptable figure at -40 deg would be? And also if I am not mistaken there should be some conversion to determine the value at certain temperature having another value for example at -20 deg.

 

[redpicker]

I know of no conversion. As far as I know, you will have to re-test at the lower temperature. Such a conversion would be very helpful, but I haven't seen one in over 25 years.

rp

 

[unclesyd]

How about 50 years.

If it's an AMS material there should be graph or table showing lower temperature tests unless there is some limitation on use at temperatures below -20°.

 

[Guest102023]

Well I am not quite that old, but there is no way to establish CVN @-40 based on data @-20. Even published data for a given material will only give you an idea of pass/fail ... you will need to test it.

Given that it has 27J @-20, your chances @-40 are so-so at best, but it depends on the minimum requirement.

 

[Elnur250774]

Ok, thank you all. Could you tell me what would be expected value at -40 deg?

 

[HgTX]

Lower.

Hg


Eng-Tips policies: faq731-376

 

[Guest102023]

Lower

 

[redpicker]

Don't be too suprised at the glib responses; we've all been asked this question by our bosses (well, I know I have, countless times) and the answer never changes.

You may see a drastic change between -20C and -40. You may see very little change. In some cases, you might see a slight (insignifigant) rise (due only to the natural scatter in the results). The only way to find out is to test the material and see what happens.

But, in reading you question, I am not sure I understand what you are asking.

1) You have a part that currently has average values of 27J at -20C and your client wants to know what the values would be at -40?

2) You have a part that was produced to a standard of 27J minimum average at -20C and your client needs testing at -40. You want to know what a reasonable minimum average would be at the lower temperature?

3) You have a part that was produced to a standard of 27J minimum average @ -20C and you want to know what shold you subtract from the -20C results to indicate whether or not it would meet the 27J at -40?

For 1), all you can do is test at -40 and see if it passes.
For 2), if it was my responsibility, I would insist on 27J minimum average at -40 (if testing at -40 was necessary).
For 3), I would look at the -20C results, nod approvingly, and say "we need to test at -40".

If neither of these match your question, you will need to re-phrase your question.

rp

 

[TomEun]

I believe your client requires the material with minimum 27J at -40 deg.C if they designated the test temperature of -40 deg.C in the P.O. Spec. In this case, you have to do the followings;
(1) Impact test for minimum 27J at -40 deg.C unless you can use any exemption clauses in the applicable codes or
(2) Change the material to a low temperature material.

If you have designed/selected the material with minimum 27J at -20 deg.C under the economic consideration, the impact test (minimum 27J at -40 deg.C ) of the material may not be readily passed.

Thomas Eun

 

[QAFitz]

The higher the hardness, the lower the CVN.
What's the hardness and what's the material?