EVOLUTION CHARACTERISTICS OF VOIDS WITHIN WELDED STRUCTURE AND ITS MULTI-SCALE MODELING

To explore the behavior of defects from meso- to macro-scale on the toe of a welded structure. A welded specimen with meso-voids on the toe of the weld was taken as experimental objects. During the quasi-static loading and unloading testing, X-CT (Micro focus X-ray Computed Tomography System) was employed to record the tomograms of defects, and the macro-scale response of the specimen was measured synchronously when the specimen was loaded up to failure. The experimental results show that the specimen’s modulus decreases linearly with the deformation on the same time of meso-voids initiation and growth keep happening, and the total volume of meso-voids tends to increase linearly with the plastic deformation. The volume-amount of voids shows typical fractal patterns in different stages of plastic deformation, and the fractal dimension is slowly increasing along with plastic strains of the specimen. According to the relation between macro-scale property and total volume of meso-voids, and combining the significance of fractal behavior, a new multi-scale damage characteristic method is proposed, which was verified by Lemaitre’s damage theories. The results show that the new method for the damage modeling has an explicit physical meaning, and that it can well describe the trans-scale damage evolution process of meso-voids initiation, growth, and the failure development of specimen.