## Smith diagram for 3CR12 steel

## Smith diagram for 3CR12 steel

(OP)

We have got a fatigue test result serious for T joints. The material was 3CR12. The load was bending.

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.

Does somebody know similar test results or it is an error?

Thank you!

Ervin

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.

Does somebody know similar test results or it is an error?

Thank you!

Ervin

## RE: Smith diagram for 3CR12 steel

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

Adam Quilter

AdamQ1@aol.com

## RE: Smith diagram for 3CR12 steel

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

## RE: Smith diagram for 3CR12 steel

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

## RE: Smith diagram for 3CR12 steel

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

## RE: Smith diagram for 3CR12 steel

## RE: Smith diagram for 3CR12 steel

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

## RE: Smith diagram for 3CR12 steel

Thank you very much!

Fax: +49 2191 950 127

## RE: Smith diagram for 3CR12 steel

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

## RE: Smith diagram for 3CR12 steel

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

## RE: Smith diagram for 3CR12 steel

dik(visitor)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

## RE: Smith diagram for 3CR12 steel

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

Best regards,

Irwin