Percorrer por autor "Martins, P.A.F."
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- Assembly of lightweight sandwich panels through joining by formingPublication . Sampaio, R. F. V.; Pragana, J. P. M.; Bragança, I .M F; Martins, P.A.F.This paper is focused on the assembly of lightweight sandwich panels built upon the patented ‘Opencell’ structure concept. The objective is to investigate the possibility of joining the connection members of the core to the adjoining skin sheet by plastic deformation at ambient temperature, instead of welding or adhesive bonding. The methodology draws from earlier developments of the authors in joining by forming using the mortise-and-tenon concept to experimentation and finite element modelling of the assembly process in unit cells that are representative of the sandwich panels. It is shown that replacing welding by joining by forming allows fabricating sandwich panels from sheet materials that are difficult or impossible to weld while preventing thermal cycles that are responsible for causing metallurgical changes, distortions, and residual stresses. Replacing adhesive bonding by joining by forming circumvents the need of surface preparation, time for the adhesive to cure and environmental compliance, among other requirements
- Electric performance of fastened hybrid busbars: An experimental and numerical studyPublication . Sampaio, Rui F. V.; Pragana, João P. M.; Bragança, Ivo; Silva, Carlos M. A .; Nielsen, Chris Valentin; Martins, P.A.F.This paper is focused on fastened hybrid busbars made from copper and aluminium with the purpose of analysing the influence of the steel bolts, of their tightening torque and of the surface condition of the sheets on the electric current flow and electric resistance of the joints. The methodology combines experimentation with unit cells that are representative of the joints and electro-mechanical numerical simulation using a finite element computer program developed by the authors. Results are a step forward in understanding the combined influence of bolts, contact pressure and surface roughness on the electric performance of fastened hybrid busbars. Design guidelines for dimensioning the cross sections of the copper and aluminium sheets and for effectively distributing bolts across the contacting surfaces are also provided.