Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Use of Stress Gradient Factor for Welded Structures
Submission Author:
Antonio Carlos de Oliveira Miranda , DF
Co-Authors:
Antonio Carlos de Oliveira Miranda, Paulo Oliveira Júnior
Presenter: Antonio Carlos de Oliveira Miranda
doi://10.26678/ABCM.COBEM2023.COB2023-0514
Abstract
The objective of this study is to develop the stress gradient factor based on Stress Intensity Factor (SIF), Kgr, to estimate the lives of metallic elements subjected to welding. Recent research has shown that modifying the residual stresses induced by welding can improve the fatigue performance of structural mechanical components. One technology is the High Frequency Mechanical Impact treatment (HFMI), which was investigated by Ghahremani in 2015 by comparing experimental data life of welded specimens with the estimated ones using Strain Based Fracture Mechanics (SBFM). Elasto-plastic stress gradient factors ahead of notch tips are used to evaluate actual notch effects in fatigue strength. Considering that local plasticity around notch tips plays a significant role in the growth behavior of cracks within the notch plastic zone, a sound mechanical methodology is proposed to account for the effects of elasto-plastic stress and strain fields. Two-dimensional finite element analyses are conducted to compute stress intensity factors of smooth and notched specimens. Ramberg-Osgood model and Neuber’s rule are used to achieve approximations for strain-based intensity factors. The Kgr solution, which takes into account both the nominal and residual stresses, is computed using Weight Functions, finite difference method and SBFM. With the Kgr solution, as a local equation of SIF, the life of a welded component could be estimated by classical da/dN method. For methodology validation, numerical predictions are compared to experimental stress-life data of 350W steel weld presented by Ghahremani to validate the proposed word. These welded components have residual stress range of -0.22·σy (lower limit) to +0.30·σy (upper limit) with non-linear stress distributing through thickness component. The results of Kgr show a significant effect of SIF for different residual stress distribution. However, because it was within the presented range, showing good model validation, and that it does not show large variations in the investigated range. The model described in this work can estimate the fatigue of welded parts and cruciform welded joints treated with HFMI under varied loading conditions using the Kgr equations. Numerical predictions are compared with other approaches and with experimental data, showing good agreement between the predictions of the methodology proposed and the experimental data.
Keywords
Stress Gradient Factor, welded structures, Mechanical Impact treatment
