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The buckling of a gold thin film deposited on a rigid substrate has been numerically investigated by means of static molecular dynamics simulations. Three different regimes of deformation have been identified depending on the values of the adhesion energy of the film on its substrate (Γ int). For low adhesion energy, the buckling and gliding through dislocation emission into the interface have been observed. For intermediate values of Γ int , the dissociation of the interfacial dislocations into the film leads to the formation of a Lomer–Cottrell lock that stops the buckle extension, promoting thus the propagation of a crack accompanied by the emission of dislocations. It results in the formation of a twin. For large values of Γ int , the kinking of the interfacial crack has been evidenced along with dislocation nucleation at its tip leading to twins again. Finally, the different evolutions of the film have been summarized in a "behavior" diagram displayed in the plane of applied strain and adhesion energy variables. [ABSTRACT FROM AUTHOR]

Abstract: The unsymmetrical discharge of a granular solid from a thin-walled cylindrical metal silo is well known to be a potential prelude to catastrophic buckling failure. The mechanics of this structure have only been very slowly unraveled in recent years with the help of powerful nonlinear finite element analyses. The associated buckling collapse is now known to be caused by localized axial membrane compression and occurs under predominantly elastic conditions. However, such high compressive stress concentrations are also known to produce significantly less imperfection sensitivity than uniform compression. For this reason, the search for an appropriately detrimental imperfection form under eccentric discharge has been quite a long one. This study presents and explores a novel form of long-wave imperfection using a superellipse to parametrise the entire shell geometry. This imperfection, termed ‘superelliptical flattening’, is judged to be potentially present in practical silo construction, and is shown to cause significant decreases in the nonlinear buckling strength of an imperfect slender silo under eccentric discharge. [Copyright &y& Elsevier]

This paper is concerned with the problem of comparison of two non-probabilistic set-theoretical models for dynamic response and buckling failure measures of bars with unknown-but-bounded initial imperfections. Two kinds of non-probabilistic set-theoretical models are convex models and interval analysis models. In convex models and interval analysis models, the uncertain quantities are considered to be unknown except that they belong to given sets in an appropriate vector space. In this case, all information about the dynamic response and buckling failure measures of bars is provided by the set of dynamic responses and buckling failure measures consistent with the constraints on the uncertain quantities. The dynamic response estimate is actually a set in appropriate response space rather than a single vector. The set estimate is the smallest calculable set which contains the uncertain dynamic response, but it is usually impractical to calculate this set. Two set estimate methods are developed which can calculate the time varying box or hyperrectangle, i.e. interval vector in the response space that contains the true dynamic response. Comparison between convex models and interval analysis models in mathematical proofs and numerical calculations shows that, under the condition of the outer enclosed ellipsoid from a hyperrectangle or an interval vector, the set dynamic response predicted by interval analysis models is smaller than that yielded by convex models; under the condition of the outer enclosed hyperrectangle or an interval vector from an ellipsoid, the dynamic response set calculated by convex models is smaller than that obtained by interval analysis models. [Copyright &y& Elsevier]