76 research outputs found
Implementation and applications of a finite-element model for the contact between rough surfaces
Combined sticking: a new approach for finite-amplitude Coulomb frictional contact
Engineering-level accuracy of discretization methods for frictional contact originates from precise representation of discontinuous frictional and normal interaction laws and precise discrete contact techniques. In terms of discontinuous behavior in the quasi-static case, two themes are of concern: the
normal interaction (i.e. impact) and the jumps in tangential directions arising from high frictional values. In terms of normal behavior, we use a smoothed complementarity relation. For the tangential behavior, we propose a simple and effective algorithm, which is based a stick predictor followed by corrections to the tangential velocity. This allows
problems with impact and stick-slip behavior to be solved with an implicit code based on NewtonâRaphson iterations. Three worked examples are shown with comparisons with published results. An extension to node-to-face form in 3D is also presented
Numerical simulation of 2D steady granular flows in rotating drum: On surface flows rheology
13 pages, 14 figures, 61 references, submitted to Phys. FluidsThe rheology of 2D steady surface flow of cohesionless cylinders in a rotating drum is investigated through {\em Non Smooth Contact Dynamics} simulations. Profile of volume fraction, translational and angular velocity, rms velocity, strain rate and stress tensor were measured at the midpoint along the length of the surface flowing layer where the flow is generally considered as steady and homogeneous. Analysis of these data and their inter-relations suggest the local inertial number - defined as the ratio between local inertial forces and local confinement forces - to be the relevant dimensionless parameter to describe the transition from the quasi-static part of the packing to the flowing part at the surface of the heap. Variations of the components of the stress tensor as well as the ones of rms velocity as a function of the inertial number are analysed within both the quasi-static and the flowing phases. Their implications are discussed
Numerical modeling of the thermal contact in metal forming processes
Heat flow across the interface of solid bodies in
contact is an important aspect in several engineering applications.
This work presents a finite element model for the
analysis of thermal contact, which takes into account the
effect of contact pressure and gap dimension in the heat
flow across the interface between two bodies. Additionally,
the frictional heat generation is also addressed, which
is dictated by the contact forces predicted by the mechanical
problem. The frictional contact problem and thermal
problem are formulated in the frame of the finite element
method. A new law is proposed to define the interfacial heat
transfer coefficient (IHTC) as a function of the contact pressure
and gap distance, enabling a smooth transition between
two contact status (gap and contact). The staggered scheme
used as coupling strategy to solve the thermomechanical
problem is briefly presented. Four numerical examples are presented to validate the finite element model and highlight
the importance of the proposed law on the predicted
temperature.The authors gratefully acknowledge the financial
support of the Portuguese Foundation for Science and Technology
(FCT) under the project PTDC/EMS-TEC/1805/2012 and by
FEDER funds through the program COMPETE Programa Operacional
Factores de Competitividade, under the project CENTRO-07-0224-
FEDER-002001 (MT4MOBI). The second author is also grateful to the
FCT for the postdoctoral grant SFRH/BPD/101334/2014. The authors
would like to thank Prof. A. Andrade-Campos for helpful contributions
on the development of the finite element code presented in this work.info:eu-repo/semantics/publishedVersio
Numerical and experimental analysis of wrinkling during the cup drawing of an AA5042 aluminium alloy
The recent trend to reduce the thickness of metallic sheets used in forming processes strongly increases the likelihood of the occurrence of wrinkling. Thus, in order to obtain defect-free components, the prediction of this kind of defect becomes extremely important in the tool design and selection of process parameters. In this study, the sheet metal forming process proposed as a benchmark in the Numisheet 2014 conference is selected to analyse the influence of the tool geometry on wrinkling behaviour, as well as the reliability of the
developed numerical model. The side-wall wrinkling during the deep drawing process of a cylindrical cup in AA5042 aluminium alloy is investigated through finite element simulation and experimental measurements. The material plastic anisotropy is modelled with an advanced yield criterion beyond the isotropic (von Mises) material behaviour. The results show that the shape of the wrinkles predicted by the numerical model is strongly affected by the finite element mesh used in the blank discretization. The accurate modelling of the plastic anisotropy of the aluminium alloy yields numerical results that are in good agreement with the experiments, particularly the shape and location of the wrinkles. The predicted punch force evolution is strongly influenced by the friction coefficient used in the model. Moreover, the two punch geometries provide drawn cups with different wrinkle waves, mainly differing in amplitude.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) under project PTDC/EMS-TEC/1805/2012. The first author is also grateful to the FCT for the Postdoctoral grant SFRH/BPD/101334/2014 and P.D. Barros is grateful to the FCT for the PhD Grant SFRH/BD/98545/2013info:eu-repo/semantics/publishedVersio
Bi-First: A simple and efficient algorithm to identify dissipated energy in impact problems
A mixed formulation for frictional contact problems prone to Newton like solution methods
- âŠ