Plastic collapse load prediction and failure assessment diagram analysis of cracked circular hollow section T-joint and Y-joint

2013 ◽  
Vol 37 (3) ◽  
pp. 314-324 ◽  
Author(s):  
S. T. Lie ◽  
T. Li ◽  
Y. B. Shao
Keyword(s):  
Plastic Collapse ◽  
Collapse Load ◽  
Load Prediction ◽  
Hollow Section ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Circular Hollow Section ◽  
Diagram Analysis

Plastic Collapse Load Investigation for Safety Assessment of Cracked Square Hollow Section (SHS) T-, Y- and K-Joints

2010 ◽  
Author(s):  
Seng Tjhen Lie ◽  
Baofeng Zhang
Keyword(s):  
Critical Role ◽  
Fatigue Tests ◽  
Plastic Collapse ◽  
Collapse Load ◽  
Tubular Structures ◽  
Axial Loads ◽  
Element Analysis ◽  
Hollow Section ◽  
Failure Assessment ◽  
Collapse Behavior

The plastic collapse load play a critical role in the entire procedure of constructing Failure Assessment Diagrams (FADs) of cracked tubular structures. In this study, the models of square-to-square hollow section (SHS) T-, Y- and K-joints with the actual 3D surface cracks obtained from previous fatigue tests are generated, and their general plastic collapse behavior has been studied carefully using the elastic-plastic finite element analysis. Based on the extensive FE analyses, the fully plastic collapse load solutions for the cracked SHS joints under brace end axial loads are proposed and derived. The load-displacements curves are plotted for predicting the plastic collapse loads based on the twice-elastic compliance criterion. Compared with formulae proposed in BS7910 [1], it was found that a conservative plastic collapse load for the SHS joints under brace end axial loads is produced using the proposed formulae. Future works are recommended for validation of BS7910 [1] FADs for damaged SHS T-, Y- and K-joints based on the numerically calculated plastic collapse load.

Finite Element Validation Studies of BS7910 FAD Method Applied to Welded SHS Joints

2007 ◽  
Author(s):  
Zhengmao Yang ◽  
Seng Tjhen Lie ◽  
Wie Min Gho
Keyword(s):  
Finite Element ◽  
Offshore Structures ◽  
Reduction Factor ◽  
Plastic Collapse ◽  
Surface Cracks ◽  
Collapse Load ◽  
T Joints ◽  
Hollow Section ◽  
Wide Range ◽  
Circular Hollow Section

The failure assessment diagram (FAD) has now been widely accepted and used for the assessment of defects found in metallic structures. In BS7910 (2005), the use of this method for offshore structures has been validated for a range of joint geometries. But these validations are only applicable for circular hollow section (CHS) welded joints. For rectangular or square hollow section (RHS or SHS) joints, there are very few references available in the literature. In this paper, systematic investigations have been carried out for the validation and verification of the FAD curves for SHS T-joints. FAD curves for a wide range of welded SHS T-joints containing surface cracks have been established using the fracture mechanics data generated from the finite element analyses. The range of β ratio of these joints is from 0.3 to 0.8. Therefore, the failure mode is constrained in the chord face yielding. The influence of residual stresses on the plastic collapse load and the FAD curves has also been analyzed. The reduction factor used to calculate the plastic collapse load of the SHS T-joints containing cracks have been quantitatively examined, and the use of the BS7910 (2005) Level 2A FAD for SHS joints containing surface cracks has been validated accordingly.

scholarly journals Failure assessment diagram analysis of creep crack initiation in 316H stainless steel

2003 ◽  
Vol 80 (7-8) ◽  
pp. 541-551 ◽  
Author(s):  
C.M. Davies ◽  
N.P. O'Dowd ◽  
D.W. Dean ◽  
K.M. Nikbin ◽  
R.A. Ainsworth
Keyword(s):  
Stainless Steel ◽  
Crack Initiation ◽  
Failure Assessment Diagram ◽  
Creep Crack ◽  
Failure Assessment ◽  
Diagram Analysis

A Procedure for the Assessment of the Structural Integrity of Nuclear Pressure Vessels

1983 ◽  
Vol 105 (1) ◽  
pp. 28-34 ◽  
Author(s):  
J. M. Bloom
Keyword(s):  
Structural Integrity ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Plastic Collapse ◽  
Failure Assessment Diagram ◽  
Linear Elastic ◽  
Failure Assessment ◽  
Deformation Plasticity ◽  
Margin Of Safety ◽  
Two Parameters

This paper presents a simple engineering procedure that the utility industry can use to assess the integrity of typical nuclear-grade pressure vessels. The procedure recognizes both brittle fracture and plastic collapse and is based on a set of proposed failure assessment curves which make up a safety/failure plane. The plane is defined by the stress intensity factor/fracture toughness ratio as the ordinate and the applied stress/reference plastic collapse stress ratio as the abscissa. The failure assessment procedure is based in part on the British Central Electricity Generating Board’s R-6 failure assessment diagram and the deformation plasticity solutions of the General Electric Company. Two parameters, a plastic collapse parameter (Sr′) and linear elastic fracture mechanics parameter (Kr′) are calculated by the user. The point (Sr′, Kr′) is plotted on the appropriate failure assessment diagram. If the point lies inside the respective curve, the structure is safe from failure. Moreover, for a given pressure and a postulated or actual flaw size, the margin of safety of the structure can be simply determined. Consistent with Appendix A of Section XI, (Division 1) of the ASME Boiler and Pressure Vessel Code the procedure presented in this paper is limited to ferritic materials 4 in. (102 mm) and greater in thickness. Details of the derivation of the proposed set of failure assessment curves are provided along with a sample problem illustrating the use of these curves.

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