Method of Constraint Loss Correction for CTOD Fracture Toughness under Welding Residual Stress Field

2010 ◽  
Vol 638-642 ◽  
pp. 3931-3936 ◽  
Author(s):  
Yoichi Yamashita ◽  
Fumiyoshi Minami
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Plastic Zone Size ◽  
Assessment Method ◽  
Welding Residual Stress ◽  
Residual Stress Field ◽  
Stress Criterion ◽  
Stress Effects ◽  
Ductile Brittle Transition Temperature ◽  
Size Criterion

This paper studied the assessment method for welding residual stress effects and constraint loss effects on brittle fracture of structural component subjected to membrane stress. The methodology of CTOD fracture toughness correction for welded joints is proposed from lower to upper ductile-brittle transition temperature region. The methodology is based on the tensile plastic zone size criterion and the equivalent CTOD ratio derived from the Weibull stress criterion. It has been found that the proposed methodology has given the reasonable fracture assessment results.

Fracture Assessment of Structural Component With Residual Stress on the Basis of the Weibull Stress Criterion

2008 ◽  
Author(s):  
Yoichi Yamashita ◽  
Fumiyoshi Minami
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Structural Component ◽  
Welding Residual Stress ◽  
Fracture Toughness Test ◽  
Stress Criterion ◽  
Conventional Procedure ◽  
Calculation Results ◽  
Fracture Assessment ◽  
Weibull Stress

This paper studies the method for estimating the residual stress effects on brittle fracture of structural component based on the Weibull stress criterion. Experiments show that the critical CTOD and the critical load of wide plate with welding residual stress are apparently smaller than those of wide plate without residual stress. It has been found that the critical CTODs of wide plate with and without residual stress can be predicted from the 3PB fracture toughness test results based on the Weibull stress criterion. Constraint loss effects on CTOD of wide plate with residual stress can be assessed by the equivalent CTOD ratio. The equivalent CTOD ratio β is defined as the ratio, β = δ/δWP, where δ and δWP, are CTODs of the standard fracture toughness specimen and wide plate, respectively, at the same level of the Weibull stress. Calculation results of beta are also shown for various residual stress levels and crack lengh based on the Weibull stress criterion. Fracture assessment results using β are shown within the context of CTOD design curve. An excessive conservatism observed in the conventional procedure is reasonably reduced by applying the equivalent CTOD ratio, β.

Dynamic evolution of welding residual stress field under noncontact electromagnetic force

2010 ◽  
Vol 107 (5) ◽  
pp. 054904
Author(s):  
Da Xu ◽  
Xuesong Liu ◽  
Ping Wang ◽  
Jianguo Yang ◽  
Wei Xu ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Electromagnetic Force ◽  
Welding Residual Stress ◽  
Dynamic Evolution ◽  
Residual Stress Field

Temperature and Residual Stress Fields in an Austenitic Circumferential Pipe Weld

2002 ◽  
Author(s):  
Ruthard Bonn ◽  
Klaus Metzner ◽  
H. Kockelmann ◽  
E. Roos ◽  
L. Stumpfrock
Keyword(s):  
Residual Stress ◽  
Numerical Calculation ◽  
Stress Field ◽  
Quantitative Determination ◽  
Welding Residual Stress ◽  
Stress Fields ◽  
Residual Stress Field ◽  
Circumferential Welds ◽  
The Impact

The main target of a research programme “experimental and numerical analyses on the residual stress field in the area of circumferential welds in austenitic pipe welds”, sponsored by Technische Vereinigung der Großkraftwerksbetreiber e. V. (VGB) and carried out at MPA Stuttgart, was the validation of the numerical calculation for the quantitative determination of residual stress fields in austenitic circumferential pipe welds. In addition, the influence of operational stresses as well as the impact of the pressure test on the residual stress state had to be examined. By using the TIG orbital welding technique, circumferential welds (Material X 10 CrNiNb 18 9 (1.4550, corresponding to TP 347) were produced (geometric dimensions 255.4 mm I.D. × 8.8 mm wall) with welding boundary conditions and weld parameters (number of weld layers and weld built-up, seam volume, heat input) which are representative for pipings in power plants. Deformation and temperature measurements accompanying the welding, as well as the experimentally determined (X-ray diffraction) welding residual stress distribution, served as the basis for the verification of numeric temperature and residual stress field calculations. The material model on which the calculations were founded was developed by experimental weld simulations in the thermo-mechanical test rig GLEEBLE 2000 for the determination of the material behaviour at different temperatures and elasto-plastic deformation. The numeric calculations were carried out with the Finite Element program ABAQUS. The comparison of the calculation results with the experimental findings confirms the proven validation of the developed numerical calculation models for the quantitative determination of residual stresses in austenitic circumferential pipings. The investigation gives a well-founded insight into the complex thermo-mechanical processes during welding, not known to this extent from literature previously.

The Effects of Loadings on Welding Residual Stresses and Assessment of Fracture Parameters in a Welding Residual Stress Field

2011 ◽  
Author(s):  
Liwu Wei ◽  
Weijing He ◽  
Simon Smith
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Path Dependence ◽  
Welding Residual Stress ◽  
Assessment Procedure ◽  
Fe Model ◽  
J Integral ◽  
Residual Stress Field ◽  
Growing Crack

The level of welding residual stress is an important consideration in the ECA of a structure or component such as a pipeline girth weld. Such a consideration is further complicated by their variation under load and the complexity involved in the proper assessment of fracture mechanics parameters in a welding residual stress field. In this work, 2D axi-symmetric FEA models for simulation of welding residual stresses in pipe girth welds were first developed. The modelling method was validated using experimental measurements from a 19-pass girth weld. The modeling method was used on a 3-pass pipe girth weld to predict the residual stresses and variation under various static and fatigue loadings. The predicted relaxation in welding residual stress is compared to the solutions recommended in the defect assessment procedure BS 7910. Fully circumferential internal cracks of different sizes were introduced into the FE model of the three-pass girth weld. Two methods were used to introduce a crack. In one method the crack was introduced instantaneously and the other method introduced the crack progressively. Physically, the instantaneously introduced crack represents a crack originated from manufacturing or fabrication processes, while the progressively growing crack simulates a fatigue crack induced during service. The J-integral values for the various cracks in the welding residual stress field were assessed and compared. This analysis was conducted for a welding residual stress field as a result of a welding simulation rather than for a residual stress field due to a prescribed temperature distribution as considered by the majority of previous investigations. The validation with the 19-pass welded pipe demonstrated that the welding residual stress in a pipe girth weld can be predicted reasonably well. The relaxation and redistribution of welding residual stresses in the three-pass weld were found to be significantly affected by the magnitude of applied loads and the strain hardening models. The number of cycles in fatigue loading was shown to have little effect on relaxation of residual stresses, but the range and maximum load together governed the relaxation effect. A significant reduction in residual stresses was induced after first cycle but subsequent cycles had no marked effect. The method of introducing a crack in a FE model, progressively or instantaneously, has a significant effect on J-integral, with a lower value of J obtained for a progressively growing crack. The path-dependence of the J-integral in a welding residual stress field is discussed.

Quantification of Residual Stresses Induced by Prior Loading at High Temperatures

2011 ◽  
Author(s):  
Ali N. Mehmanparast ◽  
Catrin M. Davies ◽  
Robert C. Wimpory ◽  
Kamran M. Nikbin
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Residual Stresses ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Crack Plane ◽  
Residual Stress Field ◽  
Compression Direction ◽  
Fracture Specimen

High temperature components generally undergo cyclic loading conditions. Prior tensile/compressive loading of a fracture specimen can induce compressive/tensile residual stress fields at the crack tip. These residual stresses will influence the subsequent fracture behaviour of the cracked body. This work forms part of a project to examine the influence of creep induced damage at a crack tip on subsequent fatigue crack growth and fracture toughness properties of austenitic type 316H stainless steel. Creep damage is introduced local to the crack tip of a fracture specimen by interrupting a creep crack growth test, performed at 550 °C. Prior to testing, the material was pre-compressed in order to strain harden the material. The compact tension, C(T), specimen geometry has been considered in this work. Since residual stresses are known to influence fatigue and fracture toughness properties of a cracked body, it is important that the residual stress levels at the crack tip are quantified. Neutron diffraction (ND) measurements have therefore been performed to quantify the extent of residual stress in these samples after initial loading, and compared to finite element model predictions. Two specimens have been considered with the crack plane orientated in parallel and perpendicular to the pre-compression direction. Compressive residual stresses of around 100 MPa have been measured directly ahead of the crack tip. Reasonable predictions of the principal residual stress distributions have been obtained by the simplified FE analysis. Though the tensile properties differ significantly in for specimens orientated parallel and perpendicular to the pre-compression direction, no significant differences in the residual stress field are predicted in the C(T) specimens orientated in both directions.

Evaluation of Residual Stress Effects on Brittle Fracture Strength Based on Weibull Stress Criterion

2008 ◽  
Vol 5 (6) ◽  
pp. 101524 ◽  
Author(s):  
Yoichi Yamashita ◽  
Fumiyoshi Minami ◽  
Richard Neu ◽  
Kim Wellin ◽  
Steven R. Thompson ◽  
...  
Keyword(s):  
Residual Stress ◽  
Brittle Fracture ◽  
Fracture Strength ◽  
Stress Criterion ◽  
Stress Effects ◽  
Strength Based ◽  
Weibull Stress
Sign in / Sign up

Export Citation Format

Share Document