Mathematical formulation of a dynamical system with dry friction subjected to external forces

We consider the response of a one-dimensional system with friction. S.W. Shaw (Journal of Sound and Vibration, 1986) introduced the set up of different coefficients for the static and dynamic phases (also called stick and slip phases). He constructs a step by step solution, corresponding to an harmonic forcing. In this paper, we show that the theory of variational inequalities provides an elegant and synthetic approach to obtain the existence and uniqueness of the solution, avoiding the step by step construction. We then apply the theory to a real structure with real data and show that the model is quite accurate. In our case, the forcing motion comes from dilatation, due to temperature

Selection of massive bone allografts using shape-matching 3-dimensional registration

Background and purpose Massive bone allografts are used when surgery causes large segmental defects. Shape-matching is the primary criterion for selection of an allograft. The current selection method, based on 2-dimensional template comparison, is inefficient for 3-dimensional complex bones. We have analyzed a 3-dimensional (3-D) registration method to match the anatomy of the allograft with that of the recipient

Modélisation multiphasique appliquée au calcul d’ouvrages en sols renforcés par inclusions rigides

Une modélisation des sols renforcés par inclusions rigides, qualifiée de multiphasique, est proposée, permettant de prendre explicitement en compte les phénomènes d’interaction entre le sol et les inclusions, qui gouvernent la façon dont les charges appliquées à l’ouvrage se transmettent aux renforcements et conditionnent l’efficacité des ces derniers. On montre en particulier dans cet article, comment l’identification de coefficients relatifs aux interactions latérale et en tête d’inclusion, réalisée à partir de simulations numériques sur une configuration simple de référence, permet la mise en œuvre d’un tel modèle dans le cadre d’un code par éléments finis. L’outil de calcul ainsi mis au point est alors appliqué à l’analyse du tassement d’un sol compressible consécutif à l’édification d’un remblai, et à la réduction considérable de ce tassement pouvant résulter d’une solution de renforcement par inclusions rigides

Improvement of massive bone allograft selection using 3D-CT-registration

Massive bone allograft selection is generally based on radiographs comparison of the allograft with those of the patient. Some mismatch can persist, leading to poor host-allograft contact or poor reconstruction stability with potential non-union or fracture. A method based on registration is presented to optimize the matching between allograft and patient's bone. CT-based 3D-registration was used in six cases to help the surgeon in the choice of the best massive allograft. Good matching was obtain in five cases and only suboptimal matching in the sixth due to the lack of allograft availability. In all cases good primary stability of the construct was obtained and allowed early weight bearing of the patient. Preoperative registration of available bone allografts and patient's host bone is a promising tool in limb reconstruction surgery