Smith diagram for 3CR12 steel

[Irwin]

We have got a fatigue test result serious for T joints. The material was 3CR12. The load was bending.<br>
The result was very strange, because in the case of r=-1 (assimetric ratio) the fatigue strenght limit + mean stress (in this case szigmamean= 0) was higher than in the case of r=0.<br>
Does somebody know similar test results or it is an error?<br>
<br>
Thank you!<br>
<br>
Ervin

 

[Quilter]

I wonder if you might be able to help: I am trying to find details of the construction and interpretation of Smith diagrams. So far all I've been able to ascertain is that they are constant life diagrams along similar lines to Goodman, Gerber and Haigh diagrams, but that's all. Are you able to shed more light on them, or point me to a source of more information?

With grateful thanks for any help that you might be able to provide.

Adam Quilter
AdamQ1@aol.com

 

[Irwin]

Dear Mr. AdamQ1,

Sorry for this late answer! You can find more details about this for example in DIN15018 German Standard.
If you want more about please write me!

Best regards,

Irwin

 

[sfp2002]

Irwin,

I also need information on the Smith diagram. I looked up DIN 15018 and found the following parts:
DIN 15018-1, Cranes; steel structures; verification and analyses
DIN 15018-2, Cranes; steel structures; principles of design and construction
DIN 15018-3, Cranes; principles relating to steel structures; design of cranes on vehicles

Is this the right specification? Which part has an example of how to construct a Smith Diagram? I am looking to see how the Smith diagram differs from a Goodman diagram.

Thanks,
Sean

 

[Irwin]

Hi!

This standard is correct for St37 and ST52 material, but I think it is good for you to understand the process. You can find lots of equestion in different state: welded, notwelded state and in different load conditions (R and N shows us).
In the longest part you can find the equestions!

Other possibility is the internet:

http://www.extra.hu/irwin/ervin.html

Download: Fatigue estimation demo
This software can write some diagram for you.

The simplest way: You know the Smith diagram is a safety area of a material, where x axis is the mean stress axis, the y axis is the max/min stress axis. You need to know the fatigue limit. In this case the mean stress is 0 and this stress is the amplitude stress. This means, you can plot 2 points (a - and a + fatigue stress limit value) on y axle with this value. Next step: Write a 45 degree line beetwen the x and y axis! You know the UTS there for the maximum stress and the mean stress will be the same, because there is no amplitude stress! (static load!) This point will be on this line! From here there are several way and that will be the differenc beetwen Smith, Goodman etc. method. In the Smith diagram you need to know the limit stress, when the the minimum stress is 0, and the amplitude and mean stress are the same! This will be another 2 points of your diagram: x=(szigma(r=0)/2) ; y=0 and x=(szigma(r=0)/2)and y=szigma(r=0)! Now you can connect them.
Example: St37 Material
UTS=370 MPa
Fatigue stress limit = Sd(R=-1)=140 MPa
Fatigue stress limit2 = S1(R=0) =230 MPa

The points of your Smith diagram:
Points x y
1 0 140
2 115 230
3 370 370
4 115 0
5 0 -140

I hope everything was clear! (I used also the Haigh diagram, which is easier for me to use.)

Best regards

Ervin

 

[sheets]

If you'd like, I can fax you some info on how to create the Haigh and Smith diagrams along w/ an example. Just post your fax number.

 

[Grelling]

Hello,

I suggest to investigate the metallographic structure of the T joint. The family of 13% Cr-steel do not have the same stability in structure like a normal carbon steel, mainly because of presence of more or less retained austenite.

regards

P. Grelling

 

[Irwin]

I would see! Plese write on the top of the sheet my name: Ervin Kerekes

Thank you very much!

Fax: +49 2191 950 127

 

[xujunx]

Please help me.
could anybody tell me where to download english vision DIN 15018 files in the internet?

 

[Irwin]

Two things:
1. I think this standard has no english version!
2. Normally uoy can not download German standard! Only some information about the topic!

Best regards,

Irwin

 

I'm from Turkey. I'm a mechanical engineer and still
have been educated to get M.S at construction and
production program.I'm trying to prepare my thesis
which is about comparetive (AWS D1.1) and (DIN 15018
1,2,3 and DIN 18800)and implement project

My problem ;

As I saw DIN 15018 2 standart specified only St 52 and
St 37 steel for loading (B1 -B6)

in this standart all of the permission value for each
loading group according to notch effects

There is a note at below of Table that it defines the
ratio between consecutive loading group for instance
between B3 and B4 ( sperately for w notch effect and K
notch effect)

If We use another steel such as St 44 or another steel
group, then which documentation can we find
permisible value for each loading group from B1 to B6
and How can we calculate the ratio between consecutive
loading group

With best regards
Serdar ATILGAN
KOCAELÝ / TURKEY
GSM : 0532 609 14 36

 

[Irwin]

Hi!

Good question! I think the best way if you try to &quot;estimate&quot; something from the existing data! Sorry but this standard is correct only for these 2 materials!

Best regards,

Irwin