Numerical Study on the Variability of Plastic CTOD

Abstract

This paper presents a numerical study on the influence of material parameters and loading variability in the plastic crack tip opening displacement (CTOD) results. For this purpose, AA7050-T6 was selected as reference material and a middle-cracked tension specimen geometry was considered. The studied input parameters were the Young’s modulus, Poisson’s ratio, isotropic and kinematic hardening parameters and the maximum and minimum applied loads. The variability of the input parameters follows a Gaussian distribution. First, screening design-of-experiments were performed to identify the most influential parameters. Two types of screening designs were considered: one-factor-at-a-time and fractional factorial designs. Three analysis criteria were adopted, based on: main effect, index of influence and analysis of variance. Afterwards, metamodels were constructed to establish relationships between the most influential parameters and the plastic crack tip opening displacement (CTOD) range, based on two types of designs: Face-Centered Central Composite Design and Box-Behnken design. Finally, the metamodels were validated, enabling the expeditious evaluation of the variability in the plastic CTOD range; in addition, the variability in the fatigue crack growth rate was also evaluated.

Fatigue crack growth modeling considering a hybrid propagation strategy

“…On previous works, the authors obtained numerical results in good agreement with experimental data, considering the cyclic plastic strain at the crack tip as the fatigue damage main contributor 8 . The numerical model, based on node releases, was firstly developed to predict the plastic Crack Tip Open Displacement (CTOD p ), which was related with FCGR to produce a crack growth law 9–13 . This parameter proved to be a measure of the crack tip plastic deformation 14 .…”

“…8 The numerical model, based on node releases, was firstly developed to predict the plastic Crack Tip Open Displacement (CTOD p ), which was related with FCGR to produce a crack growth law. [9][10][11][12][13] This parameter proved to be a measure of the crack tip plastic deformation. 14 Additionally, the results shown that crack closure is a fundamental mechanism concerning FCG.…”

Special Issue: Probabilistic Mechanical Fatigue and Fracture of Materials

“…Due to the multidependent character of the fatigue crack growth process with respect to a large variety of variables and factors (variability of the material, loading, geometry, temperature, etc. ), current methods resort to the use of safety factors as a conservative approach, or by means of stochastic analysis, such as the proposal of Prates et al [8]. The authors perform a sensitivity analysis of the fatigue crack growth process based on numerical simulations, with respect to different factors (influence of material parameters and loading variability) in order to quantify their effects, in terms of the variability of the plastic CTOD.…”

Novel Characterizations of Effective SIFs and Fatigue Crack Propagation Rate of Welded Rail Steel Using DIC

“…Marques et al [20] calculated ∆CTOD pl and ∆CTOD el for several instances using the finite element method and established a simple criterion that defines the boundary of the small-scale yielding (SSY) region to avoid the ineffective use of the LEFM parameter ∆K as a characterization parameter for the fatigue crack expansion rate. Andre Prates et al [21] conducted a numerical study of the effect of material parameters and load variability on plastic CTOD results and established a relationship between the most influential parameters and the range of plastic CTOD.…”