Session: MF-02-01 Materials for Hydrogen Service (Joint with CS-02 and HT-07) - Evaluating Component Life

Paper Number: 105506

105506 - A Model for Estimating the Autofrettage Pressure in Type 2 Pressure Vessels for Storing Hydrogen at High Pressures 

Autofrettage is used in the pressure vessel industry to enhance the fatigue life of vessels for containing hydrogen at high pressures. In this application,  high pressure in the range of 400 to 1000 bar are necessary to increase the volumetric energy density of stored hydrogen. As the storage pressures increase, the amplitude of circumferential fatigue stress also increases, shortening the fatigue cycle of the vessel. Autofrettage is used to enhance the fatigue life of the vessel by locking high compressive stresses from the inside diameter (ID) to the outside diameter (OD) of the vessel liner. Presence of high compressive stresses via the autofrettage process not only decreases the amplitude of tensile fatigue stress, but also decreases the stress ratio of the fatigue cycle, improving the environment assisted fatigue crack growth  lives.

This paper describes a model to estimate the autofrettage pressure necessary to introduce a consistent and desirable residual stress pattern in the liner wall from the ID to OD. The autofrettage pressure is a function of the material stress-strain behavior, the wall thickness of the liner and a host of other variables. The proposed model is verified by conducting elastic-plastic finite element analyses in an automated parametric study in which these variables are systematically varied.  Equations are derived to estimate the distribution of the residual stresses across the liner wall and the integrity of the composite wrap reinforcing the liner.  

Several finite element cases were run in the range of wall thickness, t, from 22.9 to 25.2 mm and the yield strength, Sy, from 482.5 to 703.5 MPa. An equation was developed to estimate the autofrettage pressure for any wall thickness and yield strength combination in the above intervals. The estimated autofrettage pressure compares very well with those calculated from finite element analysis. Residual stress distribution in the liner were calculated after the pressure was released and brought to ambient. The residual stress magnitudes at the ID are insensitive to thickness but depend significantly on the yield strength of the liner material. The magnitude of the residual stress is the lowest for the material with the lowest yield strength. The equations for estimating the residual stress at the ID and the OD were also derived as a function of the yield strength.

Presenting Author: Tsz Ling Elaine Tang Siemens Technology

Presenting Author Biography: Dr. Tsz Ling Elaine Tang is a Senior Key Expert at Siemens Corporation, Technology, Princeton, NJ.
She received her Ph.D. degree in Chemical Engineering from Georgia Institute of Technology in 2015. Her research interests and expertise includes multi-physics simulations, design space exploration and optimization.
Her expertise has been applied to the development of novel design and simulation tools for additive manufacturing and other industrial applications.
She has also been the key contributor on several government-funded and industry research projects (e.g. DOE, DARPA, MxD).

Authors:

Tsz Ling Elaine Tang Siemens Technology
Letchuman Sripragash Siemens Technology
Santosh B Narasimhachary Siemens Technology
Ashok Saxena WireTough Cylinders, LLC