Estimation of C* Integral for Mismatched Welded Compact Tension Specimen

The C* integral for the compact tension (CT) specimen is calculated using the estimation equation in ASTM E1457-15. This equation was developed based on the assumption of material homogeneity and is not applicable to a welded CT specimen. In this paper, a modified equation for estimating the C* integral for a welded compact tension (CT) specimen under creep conditions is proposed. The proposed equation is defined on the basis of systematically conducted extensive finite element (FE) analyses using the ABAQUS program. A crack in the welded CT specimen is located in the center of the heat-affected zone (HAZ), because the most severe type IV cracks are located in the HAZ. The results obtained by the analysis show that the equation for estimating the C* integral in ASTM E1457-15 can underestimate the value of the C* integral for creep-soft HAZ and overestimate for creep-hard HAZ. Therefore, the proposed modified equation is suitable for describing the creep crack growth (CCG) of welded specimens.

A peridynamic damage-cumulative hybrid model for fatigue cracking

A new peridynamic fatigue damage-cumulative hybrid model is developed in this study, which is modeled by Kinetic Theory of Fracture(KTF) and Paris formula. The compact tension specimen and modified compact tension specimen are used to study the convergence of the fatigue crack growth path and fatigue life. Then constant amplitude cyclic loading and variable amplitude cyclic loading of the specimens are simulated. By comparing with the experimental results, the accuracy of the model is verified. Compared with the fatigue model that only uses KTF, the hybrid model predicts the fatigue crack growth rate more accurately. The model is based on the stress damage criterion in the fatigue crack initiation stage, which can be a basis for fatigue prediction and safety design of components in complex stress state in actual engineering.

ATLAS+ European Project: Prediction of Large Ductile Tearing in Austenitic Piping Using Local Approach

In the frame of the European ATLAS+ project it was decided to evaluate if a continuum damage model can simulate a four-points bending test on an austenitic pipe (316L type) with an aged welded joint. In this paper, the theoretical background is presented. Then, based on finite elements analyses, the GTN model damage parameters are defined by simulating laboratory tests on Notched Tensile specimens and Compact Tension specimen. Finally, the four points bending test simulation is also presented.

A study on the matching of constraint between steam turbine blade and laboratory specimens

The matching of constraint between laboratory specimens and actual cracked structures is a key problem of the accurate structure integrity assessment. Different laboratory specimens and the steam turbine blade with different constraints were selected, the matching of constraint between steam turbine blade and laboratory specimens was investigated. The results shown that the steam turbine blade with 2 c = 50 mm, a/2 c = 0.20 has a matching constraint with single edge-notched bend specimen with a/ W = 0.6 and single edge-notched tensile specimen with a/ W = 0.3. The steam turbine blade with 2 c = 50 mm, a/2 c = 0.25 has a matching constraint with single edge-notched bend specimen with a/ W = 0.7. The steam turbine blade with 2 c = 50 mm, a/2 c = 0.30 has a matching constraint with single edge-notched bend specimen with a/ W = 0.5 and single edge-notched tensile specimen with a/ W = 0.1. The steam turbine blade with 2 c = 50 mm, a/2 c = 0.35 has a matching constraint with single edge-notched bend specimen with a/ W = 0.4, compact tension specimen with a/ W = 0.3 and central-cracked tension specimen with a/ W = 0.7. The steam turbine blade with a = 15 mm, a/2 c = 0.30 has a matching constraint with compact tension specimen with a/ W = 0.7 and single edge-notched tensile specimen with a/ W = 0.5. The steam turbine blade with a = 15 mm, a/2 c = 0.40 has a matching constraint with compact tension specimen with a/ W = 0.4. The steam turbine blade with a = 15 mm, a/2 c = 0.50 has a matching constraint with single edge-notched bend specimen with a/ W = 0.5.

NUMERICAL EVALUTION OF STRESS INTENSITY FACTOR AND STRESS BIAXIALITY FOR COMPACT SPECIMEN BASED ON GRAPH MODEL OF ELASTIC SOLID

The paper presents the results of numerical calculation of the stress intensity factor and the biaxiality factor for a compact tension specimen. A singular element of the graph model of an elastic solid is used to analyze the stress state near a crack.