Scaling of dynamic bending response of metal tube under impact loading considering strain rate effects

ABSTRACTSince good constitutive laws are required to model correctly the behaviour of concrete under impact loading, it is necessary to determine the complete stress-strain response of concrete at varying strain rates. Conflicting evidence emerges about whether the critical compressive strain (defined as the strain observed at maximum stress) increases or decreases with an increasing strain rate. In this paper, a comprehensive description is given of the brittle fracture process for plain concrete under static and impact loading. The strain rate dependance of tensile microcrack growth is used to explain both the increase in strength and the increase in critical compressive strain that can occur at high strain rates. More extensive experimental results are required to determine the fundamental changes in behaviour that occur as the loading rate is increased and, thus, facilitate the development of a more precise failure model for concrete.

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Material modelling of tensile steel component under impulsive loading

International Journal of Structural Integrity ◽

10.1108/ijsi-05-2014-0026 ◽

2016 ◽

Vol 7 (2) ◽

Cited By ~ 4

Author(s):

Joao Ribeiro ◽

Aldina Santiago ◽

Constança Rigueiro

Keyword(s):

Strain Rate ◽

Impact Loading ◽

Design Methodology ◽

Ductile Damage ◽

Fe Model ◽

Strain Rate Effects ◽

Displacement Capacity ◽

Numerical Predictions ◽

Fracture Simulation ◽

Rate Effects

Purpose Characterization and modelling of the material properties, as well as the fracture simulation needed for the numerical analysis of bolted T-stub connection under impulsive loads. The strain rate effects are considered on the material law; fracture simulation is explored following “element deletion” technique for a given level of ductile damage. Design/methodology/approach The T-stub model is used in Eurocode 3 – part 1.8 as part of the “component method” for the representation of steel connection’s tension zone and is usually responsible for providing ductility to the connection. Looking forward to establish the “T-stub’s” maximum displacement capacity under impact loading, i) fracture simulation of steel elements is here explored following “element deletion” technique for a given level of ductile damage; ii) material softening and triaxial stress state dependency are assessed by finite element analysis of common uniaxial tension tests, and iii) strain rates effects are used based on results from Split-Hopkinson Bar tests, through the incorporation of the Johnson-Cook’s elevated strain rate law for material strain-hardening description. Numerical predictions of the model describing the “T-stub” behaviour and displacement capacity are compared against experimental results. Findings The FE model developed was found reliable in the description of the T-stub response subject to static and impact loads. Particularly, the strain rate sensitive material hardening following a calibrated Johnson-Cook law proved accurate in the description of the enhancement of the material strength. It was observed that when subject to impact loading regimes, the force-displacement response of T-stubs is: i) enhanced due to elevated strain rate effects, avoiding rupture when subject to a load equal the maximum static; ii) less ductile plastic failure modes in deformable T-stubs are expected, whilst the development of higher strains in the bolt may lead to a reduction in its ductility capacity. Originality/value A non-linear dynamic FE model of simple T-stub configuration using a strain rate effect on the material law and fracture simulation, providing insight of stress, strain, strain rate and damage contours developments, when exposed to impact loading.

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Modeling of Dynamically Loaded Open-Cell Metallic Foams: Yielding, Collapse, and Strain Rate Effects

Journal of Applied Mechanics ◽

10.1115/1.4000386 ◽

2010 ◽

Vol 77 (3) ◽

Cited By ~ 6

Author(s):

Pedro A. Romero ◽

Winston O. Soboyejo ◽

Alberto M. Cuitiño

Keyword(s):

Strain Rate ◽

Impact Loading ◽

Unit Cell ◽

Metallic Foams ◽

Cell Level ◽

Effective Response ◽

Strain Rate Effects ◽

Open Cell ◽

Rate Effects ◽

Dynamically Loaded

Open-cell metallic foams exhibit properties desirable in engineering applications requiring mitigation of the adverse effects resulting from impact loading; however, the history dependent dynamic response of these cellular materials has not been clearly elucidated. This article contributes an approach for modeling the response of dynamically loaded open-cell metallic foams from ligament level to unit cell level to specimen level. The effective response captures the localized chaotic collapse phenomena through ligament reorientation at cell level while maintaining the history of plastic deformation at ligament level. First, the phenomenological elastoplastic constitutive behavior of the ligaments composing the unit cell is modeled. Then, using the constitutive ligament model, the effective unit cell response is obtained from a micromechanical model that enforces the principle of minimum action on a representative 3D unit cell. Finally, the macroscopic specimen response is predicted utilizing a finite element analysis program, which obtains the response at every Gauss point in the mesh from the microscopic unit cell model. The current communication focuses on the ability of the model to capture the yielding and collapse behaviors, as well as the strain rate effects, observed during impact loading of metallic foams.

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