Papers by Giorgio Zavarise
Il Bollettino, Jul 21, 2015
Computer Methods in Applied Mechanics and Engineering, 2022
It is well known that the classical one-pass node-to-segment algorithms for the enforcement of co... more It is well known that the classical one-pass node-to-segment algorithms for the enforcement of contact constraints fail the contact patch test. This implies that solution errors may be introduced at the contacting surfaces, and these errors do not necessarily decrease with mesh refinement. The previous research has mainly focused on the Lagrange multiplier method, but the situation is even worse with the penalty method. In a recent study, the authors proposed a modified one-pass node-to-segment algorithm which is able to pass the contact patch test also in conjunction with the penalty method. In a general situation, the pressure distribution transferred across a contact surface is non-uniform. Hence, even for a contact element which passes the contact patch test under a uniform distribution of the contact pressures, the transfer of a non-uniform state of stress may give rise to disturbances related to the discretization, which affect the accuracy of the analysis. This paper, following up to the previous study, develops an enhanced node-to-segment formulation able to pass a modified version of the contact patch test whereby a linear distribution of pressures has to be transmitted across the contact surface. The proposed formulation is illustrated and some numerical examples demonstrate the good patch test performance of the enhanced contact element.
Curran Associates eBooks, 2005
Instability phenomena occurring in the microstructure of composite materials are investigated. To... more Instability phenomena occurring in the microstructure of composite materials are investigated. To this aim, a complete description of the mechanical behavior of bi-material interfaces in composite materials requires the definition of both a cohesive law involving damage for the debonding stage, and a contact model during the closure of the interface. Both formulations are herein presented and implemented in the FE code FEAP. Numerical examples showing the transition from a snap-back instability to a stable mechanical response are presented.
2018 IEEE 4th International Forum on Research and Technology for Society and Industry (RTSI), 2018
This paper presents a non-local interface mechanical model to describe aortic dissection. In this... more This paper presents a non-local interface mechanical model to describe aortic dissection. In this regard, the mode-I debonding problem based on a cohesive zone modeling is endowed with non-local terms to include long-range interactions that are present in multi-layered biological tissue. Such non-local effects are related to the collagen fibers that transmit forces between non-adjacent elements. Numerical simulations are provided with different values of the non-local parameters in order to show the effect of the non-locality during the debonding processes.
This study provides an efficient way to perform the dynamic analysis of multi-degree-of-freedom (... more This study provides an efficient way to perform the dynamic analysis of multi-degree-of-freedom (MDOF) systems ruled by coupled motion equations with fractional derivatives. Specifically, coupled fractional-derivative terms are force-displacement relations, which may suitably model the mechanical behavior of several structures and structural elements, e.g. civil structures with vibration isolators, continuous beams of viscoelastic materials, biological tissues, bones, etc. The proposed method is based on a proper fractional-order state variable analysis in conjunction with a complex modal transformation that allows to decouple the equations of motion. As the number of the degrees of freedom increases, computational efforts are reduced by a numerical approximation based on an appropriate truncation of the complex modal expansion. It is shown that the proposed approach ensures a good level of the approximation and a relevant reduction of the computational efforts. In the numerical app...
IEEE Transactions on Plasma Science
Ottavo Convegno Italiano di Meccanica Computazionale, GIMC, AIMETA, 1994
Brick and Block Masonry, 2016
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Papers by Giorgio Zavarise