A phenomenological model for anisotropic creep in a multipass weld metal

Abstract

Creep strength of welded joints can be estimated by continuum damage mechanics. In this case constitutive equations are required for different constituents of the welded joint: the weld metal, the heat-affected zone, and the parent material. The objective of this paper is to model the anisotropic creep behavior in a weld metal produced by multipass welding. To explain the origins of anisotropic creep, a mechanical model for a binary structure composed of fine-grained and coarse-grained constituents with different creep properties is introduced. The results illustrate the basic features of the stress redistribution and damage growth in the constituents of the weld metal and agree qualitatively with experimental observations. The structural analysis of a welded joint requires a model of creep for the weld metal under multiaxial stress states. For this purpose the engineering creep theory based on the creep potential hypothesis, the flow rule, and assumption of transverse isotropy is applied. The outcome is a coordinate-free equation for secondary creep formulated in terms of the Norton-Bailey-Odqvist creep potential and three invariants of the stress tensor. The material constants are identified according to the experimental data presented in the literature.

An anisotropic tertiary creep damage constitutive model for anisotropic materials

“…A number of researchers have developed constitutive models for transversely-isotropic materials; however, most formulations do not accurately model intermediate material orientations (when the longitudinal grains are not parallel or perpendicular to the load direction) [3,28,29]. For anisotropic microstructure materials, the effect of material orientation must be included in the both the creep strain rate and damage evolution equations [30].…”

“…A single weld bead consists of a single columnar solidification microstructure. Multi-pass welding (used on pressure vessels) will produce a transversely-isotropic microstructure [3].…”

Micro‐mechanical analysis of creep behavior in a multipass weld

“…The macroscopic creep properties of equivalent continuum are anisotropic in general case. The symmetry type of equivalent media is determined by geometric structure of multi-pass weld and the creep properties of the microstructure components [3]. Materials of columnar, coarse and fine grained zones are assumed to be isotropic and their creep behavior is described by Norton law.…”

Modeling of Creep for Structural Analysis

“…Simplifying assumptions are made for the behavior of constituents and their interactions, for the type of the representative volume element and for the exerted boundary conditions. [233]. [323,326], crack propagation through a power law creeping multi-grain model, e.g.…”