scholarly journals Ductile damage model based on void growth analysis by unit cell

2019 ◽  
Vol 37 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Takehisa YAMADA ◽  
Mitsuru OHATA
Keyword(s):  
Void Growth ◽  
Growth Analysis ◽  
Damage Model ◽  
Unit Cell ◽  
Ductile Damage ◽  
Model Based

Void Growth and Coalescence in Porous Plastic Solids With Sigmoidal Hardening

2019 ◽  
Vol 86 (9) ◽  
Author(s):  
Padmeya P. Indurkar ◽  
Shailendra P. Joshi
Keyword(s):  
Void Growth ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Unit Cell ◽  
Porous Solid ◽  
Effective Response ◽  
Porosity Evolution ◽  
Aspect Ratios ◽  
Spherical Voids ◽  
Void Growth And Coalescence

Abstract This paper presents an analysis of void growth and coalescence in isotropic, elastoplastic materials exhibiting sigmoidal hardening using unit cell calculations and micromechanics-based damage modeling. Axisymmetric finite element unit cell calculations are carried out under tensile loading with constant nominal stress triaxiality conditions. These calculations reveal the characteristic role of material hardening in the evolution of the effective response of the porous solid. The local heterogeneous flow hardening around the void plays an important role, which manifests in the stress–strain response, porosity evolution, void aspect ratio evolution, and the coalescence characteristics that are qualitatively different from those of a conventional power-law hardening porous solid. A homogenization-based damage model based on the micromechanics of void growth and coalescence is presented with two simple, heuristic modifications that account for this effect. The model is calibrated to a small number of unit cell results with initially spherical voids, and its efficacy is demonstrated for a range of porosity fractions, hardening characteristics, and void aspect ratios.

Proposal of Ductile Damage Model Based on Unit Cell Analysis for Prediction of Ductile Crack Growth Resistance of Cracked Component

2019 ◽  
Author(s):  
Takehisa Yamada ◽  
Mitsuru Ohata
Keyword(s):  
Crack Growth ◽  
Void Growth ◽  
Damage Evolution ◽  
Damage Model ◽  
Growth Behavior ◽  
Unit Cell ◽  
Finite Element Analyses ◽  
Ductile Crack ◽  
Evolution Law ◽  
Ductile Crack Growth

Abstract The aim of this study is to propose the damage model on the basis of the mechanism for ductile fracture related to void growth and applicable to ductile fracture assessment for steels. In order to determine damage evolution law, void growth behavior in the material was investigated by elasto-plastic finite element analyses using unit cell model with an initial void. From the results of the unit cell analyses, it was evident that a void in unit cell grew nonlinearly with increasing applied macroscopic strain. Moreover, the relationships between normalized void volume fraction and normalized strain by each critical value corresponding to crack initiation were independent of stress-strain relationship of material and stress triaxiality state. Based on this characteristic associated with void growth, damage evolution law representing nonlinear damage accumulation was derived. Then, using the damage evolution law, ductile damage model reflecting void growth behavior and ductility of material was proposed. For validation and application of the proposed damage model, ductile crack growth tests using bend specimens with a machined notch or a fatigue pre-crack were conducted for low carbon steel. The proposed damage model was implemented in finite element analyses and ductile crack growth simulations were performed for each bending test. Then, it was shown that the proposed model could accurately predict ductile crack growth resistance from machined notch root and fatigue pre-crack tip (R-curves) and the validity and applicability of proposed damage model to cracked components could be confirmed.

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