Evaluation of Environmentally Assisted Cracking of a High Strength Steel Using Elastic-Plastic Fracture Mechanics Techniques

2008 ◽  
pp. 512-512-30 ◽  
Author(s):  
EM Hackett ◽  
PJ Moran ◽  
JP Gudas
Keyword(s):  
Fracture Mechanics ◽  
High Strength Steel ◽  
High Strength ◽  
Elastic Plastic ◽  
Environmentally Assisted Cracking

Fracture Mechanics Assessment of Hydrogen Storage Vessel

2021 ◽  
Author(s):  
Xiaoliang Jia ◽  
Zhiwei Chen ◽  
Fang Ji
Keyword(s):  
High Pressure ◽  
Fracture Mechanics ◽  
Hydrogen Storage ◽  
High Strength Steel ◽  
High Strength ◽  
Linear Elastic Fracture Mechanics ◽  
Storage Vessel ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Hydrogen Storage Vessel

Abstract High strength steel is usually used in fabrication of hydrogen storage vessel. The fracture toughness of high strength steel will be decreased and the crack sensitivity of the structures will be increased when high strength steels are applied in hydrogen environment with high pressure. Hence, the small cracks on the surface of pressure vessel may grow rapidly then lead to rupture. Therefore, this paper makes a series of research on how to evaluate the 4130X steel hydrogen storage vessel with fracture mechanics. This study is based on the assumption that there is a semi-elliptic crack on internal surface of hydrogen storage vessel. First of all, based on linear elastic fracture mechanics, the stress intensity factors and crack tolerance of 4130X steel hydrogen storage vessel have been calculated by means of finite element method based on interaction integral theory and polynomial-approximated approach from GB/T 34019 Ultra-high pressure vessels. Then, a comparative study has been made from the results of above methods to find out the difference between them. At last, the fatigue life of a 4130X steel hydrogen storage vessel has been predicted based on linear elastic fracture mechanics and Paris formula. The calculation methods and analysis conclusion can be used to direct the design and manufacture of hydrogen storage vessel.

scholarly journals Elastic–Plastic and Inelastic Characteristics of High Strength Steel Sheets under Biaxial Loading and Unloading

2010 ◽  
Vol 50 (4) ◽  
pp. 613-619 ◽  
Author(s):  
Mohammad Omar Andar ◽  
Toshihiko Kuwabara ◽  
Shigeru Yonemura ◽  
Akihiro Uenishi
Keyword(s):  
High Strength Steel ◽  
Biaxial Loading ◽  
High Strength ◽  
Elastic Plastic ◽  
Steel Sheets ◽  
Loading And Unloading

Mooring Line Components With Semi-Brittle Behavior: Verification of Fitness for Purpose

2011 ◽  
Author(s):  
Tom Lassen
Keyword(s):  
Fracture Mechanics ◽  
Service Life ◽  
High Strength Steel ◽  
Crack Depth ◽  
High Strength ◽  
Ultimate Limit State ◽  
Critical Surface ◽  
Fitness For Purpose ◽  
Load Spectrum ◽  
Extreme Load

Low impact energy for Charpy V Notch (CVN) specimens and associated low Crack Tip Opening Displacement (CTOD) values have occurred on several occasions in high strength steel offshore mooring components. In the present work an Engineering Critical Assessment (ECA) for shackles has been carried out to demonstrate fitness for purpose. Typical values for CVN and CTOD are 17 Joules and 0.01 mm respectively at design temperature. The purpose of the present work is to demonstrate that even in the case where normal quality requirements are not met, the shackles may still have enough structural integrity and fatigue durability to withstand the load spectrum in the field during the planned target service life of typically 20 years. The ECA is based on applied fracture mechanics as outlined in the BS7910 document. Shackles made of QR4 high strength steel with different geometries and loading modes are analyzed. Extreme load cases and fatigue load spectra are treated and fracture mechanics modelling is discussed. A CTOD value as low as 0.01 mm may give critical surface crack depth close to 1% of the diameter in an ultimate limit state condition. For normal ductile steel behaviour the critical crack depth is usually close to 15% of the diameter. However, under the assumption that the pre-existing crack depth is 0.25 mm, the predicted fatigue life based on fracture mechanics analysis is still over 100 years. For a target service life of 20 years this corresponds to a Design Factor Fatigue (DFF) of 5. This is close to the requirement given by DNV for mooring chains. Based on the present analysis it can be concluded that the shackles are fit for purpose as manufactured even under unfavourable and unlikely assumptions.

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