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Nonlinear Analysis of Thin Fracture Specimens Using Solid, Isoparametric Finite Elements

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Title: Nonlinear Analysis of Thin Fracture Specimens Using Solid, Isoparametric Finite Elements
Author(s): Matos, C.G.; Dodds, Robert H., Jr.
Subject(s): Finite element analysis 3-D element model M(T) specimens Fracture
Abstract: This report examines the performance of various "solid" finite elements for the analysis of thin shell structures often encountered in nonlinear fracture mechanics studies. Such models require solid elements in the crack front region to capture strong through-thickness effects; modeling of the entire test specimen-structural element with solid elements then proves convenient. Unfortunately, the standard 8-node "brick" element with full integration exhibits strong shear-locking under bending deformations and thus overly stiff behavior. Three alternative elements are examined here: the 8-node element with single-point integration, the 8-node element with enhanced (incompatible) modes and the 20-node (quadratic) element. Element performance is assessed through analyses of a thin M(T) fracture specimen loaded in remote tension. This specimen generates strong compressive (T- )stresses parallel to the crack growth direction which leads to out-of-plane bending in the crack front region (triggered by a small normal force). The displacements obtained with a refined mesh of thin shell elements provide the reference solution for evaluation of the solid element performance. The analyses include large-displacement effects, but linear material response for simplicity, and are performed with Abaqus 5.6 and Warp3D. The results show clearly that both the 8-node element with enhanced modes and the 20-node element with conventional reduced integration provide solutions of accuracy comparable to the thin shell element. Mixed 8 and 20-node element meshes for ductile fracture analyses with transition elements to maintain displacement compatibility are demonstrated to provide an accurate and efficient modeling strategy.
Issue Date: 1997-11
Publisher: University of Illinois Engineering Experiment Station. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report: Civil Engineering Studies SRS-621
Genre: Technical Report
Type: Text
Language: English
Sponsor: NASA-AMES Research CenterNASA-Langley Research CenterContract Nos. NCC 2-5126 and NAG 2-1126
Date Available in IDEALS: 2009-11-16

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