Open Access

ARTICLE

Dynamic Instability of Straight Bars Subjected to Impulsive Axial Loads Using the DEM

by Letícia Fleck Fadel Miguel¹, Le,ro Fleck Fadel Miguel², João Kaminski Jr.³

1 Prof. Dr., Department of Mechanical Engineering, UFRGS, Porto Alegre, RS, Brazil. E-mail: letffm@ufrgs.br
2 Prof. Dr., Department of Civil Engineering, UFSC, Florianópolis, SC, Brazil. E-mail: leandro.miguel@ufsc.br
3 Prof. Dr., Department of Structures and Civil Construction, UFSM, Santa Maria, RS, Brazil. E-mail: jkj@ufsm.br

Computer Modeling in Engineering & Sciences 2015, 104(2), 87-104. https://doi.org/10.3970/cmes.2015.104.086

Abstract

Since the half of the XX century, attention was given to the instability of structures under parametric excitation, especially under periodic loads. On the other hand, the instability of bars subjected to axial loads of impulsive type has been little studied, in spite of the practical importance of the topic. Thus, in Engineering Design it is frequently supposed, without tests or additional verifications, that an axial load of short duration can exceed the Euler critical load of the bar without inducing damage in the same.
Within this context, this paper proposes the use of the truss-like Discrete Element Method (DEM) for determining the dynamic response of elastic straight bars subjected to axial loads defined by pulses of short duration. The proposed approach allows the consideration of initial imperfections, as well as large displacements and other non-linear effects. The influence of the pulse duration and other effects in the response of the bar are also evaluated. Initially, the performance of the proposed methodology is verified in static and dynamic instability problems of homogeneous bars without geometrical imperfections, by comparing the DEM results with analytical solutions available in the literature. After that, the DEM is employed to analyze more complex cases, including bars with initial imperfections and non-homogeneous bars, in which material properties, as Young’s modulus and mass density, are assumed to be correlated Gaussian random fields. The proposed methodology has proven to be a useful and easy tool for analysis of dynamic instability of bars and could therefore be used by designers for estimating the dynamic buckling load.

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Keywords

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