Session: HT-01-01 Design, Analysis and Life Prediction of High-Pressure Vessels and Equipment

Paper Number: 155615

155615 - Proposal of New Fatigue Evaluation Method in Kd-3 of Asme Section Viii Division 3 

Abstract: 

The current fatigue evaluation in KD-310 through KD-330 of Division 3 is based on maximum shear stress (Tresca’s theory). The fatigue evaluation procedure using elastic-plastic analysis is not described in KD-3 of current Division 3 except fatigue penalty factor Ke in KD-323. On the other hand, the fatigue evaluation using elastic-plastic analysis and equivalent strain range based on Mises’s theory are specified in 5.5.4 of Division 2. The stress amplitude based on elastic analysis and Tresca’s theory of Division 3 is greater than that based on elastic-plastic analysis and Mises’s theory of Division 2. Therefore, the current fatigue evaluation in KD-310 through KD-330 of Division 3 is more conservative than that of Division 2.

The current stress amplitude and mean stress are obtained using Tresca stress intensity. The fatigue evaluation procedure using elastic-plastic analysis and equivalent strain range in 5.5.4 of Division 2 is appropriate. Therefore, I propose changes to use Mises equivalent stress amplitude and equivalent mean stress.

Current Fatigue evaluation in KD-3 of Division 3 for high strength carbon and low alloy steels in Figure KD-320.1 and that for 17-4 PH/15-5 PH stainless steel in Figure KD-320.4 are as below. The design fatigue curves of Figure KD-320.1 and Figure. KD-320.4 do not include correction of mean stress. The equivalent stress amplitude is obtained using the stress amplitude and mean stress of evaluation point obtained by analysis, and this is applied to the design fatigue curve to obtain the allowable fatigue life. Therefore, the equivalent stress amplitude becomes larger than stress amplitude if the mean stress is tension. On the other hand, it becomes smaller if mean stress is compression. This method of determining the equivalent stress amplitude using the actual mean stress is more appropriate than the method of conservatively correcting the mean stress effect for the design fatigue curve of Division 2. The design fatigue curves of Figure KD-320.2 for carbon and low alloy steels, Figure KD-320.3 for series 3XX high alloy steel and Figure KD-320.7 for aluminum alloy which were incorporated from Division 2, are also changed to those before the correction of the effect of mean stress, and I propose changes to correct the mean stress using the equivalent stress amplitude. Since the high tensile mean stress due to tightening is applied, the design fatigue curve of Figure KD-320.5 for high strength steel bolting will not be changed as it is now.

This paper provides proposal of new fatigue evaluation method as below.

1. Change design fatigue curves without mean stress correction.

2. Change stress amplitude based on Mises equivalent stress from Tresca stress intensity.

3. Change mean stress correction method.

4. Compare with new method and current method using some examples.

Presenting Author: Susumu Terada Kobe Steel, Ltd.

Presenting Author Biography: I graduated from Osaka University (graduate school) and took a M.S. degree of welding engineering in 1977. I have worked for Kobe Steel since 1977. I am a senior engineer of design section for high pressure vessels and my duties are supervision and checking of structural design, analysis and strength evaluation for pressure vessel and heat exchangers. I took Ohio’s Professional Engineer license in 1985 and Kentucky’s Professional Engineer in 2022. I have been an ASME fellow member since 2012.
I have been the chair of subcommittee of code and standard for high pressure vessels in the High Pressure Institute of Japan (HPI) since 1998 and a member of ASME BPV VIII committee on pressure vessels since 2009 and Subgroup on high pressure vessels committee since 2003.

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