Study on J-integral plasticity factor of high-grade pipeline girth welded joints based on SENT specimen

Abstract

The girth welded joint of pipeline is a kind of special structure of high-pressure pipeline, which is extremely easy to crack under the combined action of internal and external loads, defects and stress concentration. It is particularly important to accurately evaluate the fracture toughness of each material area of high-grade pipeline girth welded joints to ensure the structural integrity of pipelines. In this paper, the clamped single edge notch tension (SENT) specimens of high-grade pipeline girth welded joints are taken as the research object. Through theoretical analysis, physical experiments, extensive finite element analysis (FEA) and machine learning (ML) methods, the numerical changes of J-integral plasticity factor of SENT specimens under different geometric parameters (crack length, specimen thickness, weld width) and mechanical properties parameters (strain hardening exponent, weld matching coefficient) are studied. The influence of specimen geometry and material properties on plasticity factor is discussed. A large number of FE calculation results are used as a database, and a ML model with strong nonlinear prediction ability is established through hyperparameter debugging. The model can quickly and accurately obtain the plastic factor values of SENT specimens of high-grade pipeline under 5 input parameters, which provides a reference for the fracture evaluation of high-grade pipeline girth welded joints.