Some observations on the dynamic elastic-plastic buckling of a structural model (original) (raw)
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Computers & Structures, 1989
Analytical studies with the ADINA computer code were performed to determine the Dynamic Load Amplification Factor (DLF) of metal beams and plates subjected to axial in-plane impact compression loading. The results were compared with experimental ones and those yielded by self developed finite differences programs. The influences of initial geometric imperfections, as well as duration of loading on the DLF were evaluated. As anticipated, the DLFs were usually higher than unity. However, in a few cases, in the presence of certain magnitudes of initial geometric imperfection and for loading durations close to the first natural period in bending, DLFs smaller than unity were observed.
Dynamic elastic-plastic buckling phenomena in a rod due to axial impact
International Journal of Impact Engineering, 1996
Dynamic elastic-plastic buckling phenomena which might develop in a rod from an axial impact loading are studied in order to identify the conditions for quasi-static behaviour. A discrete model for dynamic elastic-plastic buckling, which retains the axial and the lateral inertia forces, is proposed, and the relationship between the model parameters and the characteristics of an actual structure is given. Examples of different external loadings and boundary conditions are considered in order to clarify the influence of elastic-plastic axial wave propagation on the buckling process. The critical time for the initiation of buckling is obtained and the post-buckling behaviour of the model is analysed. Particular attention is paid to the role of the striking mass on the characteristics of the buckling process and on the development of the buckling shape. The numerical study reveals that the inertia of the striking mass affects considerably the development of the buckling shape causing different patterns of axial strain distributions at the initiation of buckling. The comparisons which are made between the model predictions and some previously published experimental data show that the buckling process is governed by the impact velocity as well as by the external loading history provided by the experimental technique.
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International Journal of Solids and Structures, 1996
The dynamic elastic-plastic buckling phenomenon is studied using a multi-degrees-offreedom model which retains the influences of axial and lateral inertia and the effects of initial geometrical imperfections. The process of buckling is considered as a quasi-bifurcation of an elasticplastic discrete system together with an analysis of the post-bifurcation behaviour.
On dynamic buckling phenomena in axially loaded elastic-plastic cylindrical shells
International Journal of Non-Linear Mechanics, 2002
Some characteristic features of the dynamic inelastic buckling behaviour of cylindrical shells subjected to axial impact loads are discussed. It is shown that the material properties and their approximations in the plastic range in uence the initial instability pattern and the ÿnal buckling shape of a shell having a given geometry. The phenomena of dynamic plastic buckling (when the entire length of a cylindrical shell wrinkles before the development of large radial displacements) and dynamic progressive buckling (when the folds in a cylindrical shell form sequentially) are analysed from the viewpoint of stress wave propagation resulting from an axial impact. It is shown that a high velocity impact causes an instantaneously applied load, with a maximum value at t = 0 and whether or not this load causes an inelastic collapse depends on the magnitude of the initial kinetic energy. ?
Dynamic elastic–plastic buckling of circular cylindrical shells under axial impact
International Journal of Solids and Structures, 2000
Dynamic axisymmetric buckling of circular cylindrical shells struck axially by a mass is studied in order to clarify the initiation of buckling and to provide some insight into the buckling mechanism as a transient process. It is assumed that the material is elastic±plastic with linear strain hardening and displaying the Bauschinger eect. The deformation process is analysed by a numerical simulation using a discrete model. Particular attention is paid to the in¯uence of stress wave propagation on the initiation of buckling. It is found that the development of the buckling shape depends strongly on the inertia properties of the striker and on the geometry of the shell. The theoretical method is used to clarify some experimental data and good agreement is obtained with results on aluminium alloy tubes. #
Dynamic plastic" and" dynamic progressive" buckling of elastic-plastic circular shells-revisited
2004
Two typical buckling patterns of circular cylindrical shells, which can occur due to axial impact loadings, are discussed. The phenomena of "dynamic plastic" buckling (when the entire length of a cylindrical shell wrinkles before the development of large radial displacements) and "dynamic progressive" buckling (when the folds in a cylindrical shell form sequentially) are analyzed from the viewpoint of stress wave propagation resulting from an axial impact. It is shown that the particular impact velocity, which instantaneously causes stresses that exceed the elastic limit of the material at the proximal end of a shell, and therefore can cause the initial instability pattern within a sustained axial plastic flow, depends on the material properties. The present analysis reveals that "dynamic plastic" buckling can develop for relatively low impact velocity, too provided that a shell has certain inertia characteristics. The latter conclusion is in contrast with the established perception that the high impact velocity is a necessary condition for the initial shell instability within a sustained axial plastic flow. A phenomenological approach is used to predict the buckling mode of a circular shell under axial impact with a given initial velocity.
Dynamic buckling of thin cylindrical shells under axial impact
International Journal of Impact Engineering, 2005
The dynamic buckling of thin isotropic thermoviscoplastic cylindrical shells compressed with a uniform axial velocity prescribed at the end faces is investigated analytically and numerically. In the first part of the paper, the stressed/deformed state of a shell is assumed to have buckled if infinitesimal perturbations superimposed upon it grow. Cubic algebraic equations are derived for both the initial growth rate of the perturbation and its wavenumber. The wavenumber corresponding to the maximum initial growth rate of a perturbation introduced at an axial strain of 0.1 is taken to determine the buckling mode. The computed buckling modes are found to match well with those listed in the available experimental data. A thermoviscoplastic constitutive relation is used to delineate the influence of material parameters on the buckling behavior. In the second part of the paper, the finite element method is used to analyze the collapse of an imperfect circular cylindrical tube with axial velocity prescribed at one of its flat end faces with the other end face kept fixed. The influence of initial randomly located imperfections on the buckling behavior is investigated and discussed. r
Effect of transverse impact on buckling behavior of compressed column
Thin-walled Structures, 2006
We investigated the buckling behavior of a column subjected to a transverse impact during static axial compression in relation to structural energy absorption in an experiment. Either a steel bar or an acrylic bar was collided into an aluminum alloy column to apply different histories of the transverse impact load. The column was buckled by the transverse impact under force lower than axial Euler's buckling force. We found that the critical condition of buckling generation was determined by the kinetic energy of the impactor independent of the impact force history. The velocity of the column deformation increased as the transverse impact velocity increased even when the axial force was low. Therefore, the deformation during postbuckling process can be controlled by the transverse impact.
Transition criteria between buckling modes of circular shells under axial impact
2005
The necessary and sufficient conditions for the development of three typical buckling modes of circular cylindrical shells, which can occur due to axial impact loadings, are discussed. The phenomena of 'dynamic plastic' buckling and 'dynamic progressive' buckling are analyzed from the viewpoint of stress wave propagation resulting from an axial impact while an empirical criterion for the transition between progressive buckling and global bending collapse of relatively long circular shells is formulated. It is shown that the particular buckling mode of a circular shell depends primarily on the speed of the development of the initial local wrinkle.
International Journal of Solids and Structures, 2001
A new concept is presented for the dynamic elastic±plastic axisymmetric buckling of circular cylindrical shells under axial impact. The phenomena of dynamic plastic buckling (when the entire length of the shell wrinkles before the development of large radial displacements) and dynamic progressive buckling (when the shell folds form sequentially) are analysed from the viewpoint of stress wave propagation resulting from an axial impact. The conditions for the development of dynamic plastic buckling are obtained.