Experimental investigation on the influence of the lubricant type in the punch stretching of extra deep-drawing steel

• Autor(a) principal: Tigrinho,Luiz Maurício V.
• Data de Publicação: 2008
• Outros Autores: Santos,Ricardo Adriano dos, Chemin Filho,Ravilson Antonio, Marcondes,Paulo Victor P.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Society of Mechanical Sciences and Engineering (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1678-58782008000400004
• topic: hemispherical punch-stretching; lubrication and extra deep-drawing steel

In sheet metal stamping, several variables must be taken into account such as the material's mechanical properties, the tool's geometry, interface lubrication between punch and sheet metal and deformation rate, among others. This paper reports on a study of the lubricant's influence on the stretching forming process. The lubricants used ranged from liquid, such as mineral and vegetable oils with extreme pressure additives and synthetic fluids to solid PVC (polyvinyl chloride) and polyurethane films. In this work, the main objective was to study a minor strain profile as an alternative method to analyze the influence of solid and liquid lubricants on stretching forming of high stampability steels (DC 06). The minor true strain distribution profile was obtained, from the die radius to the punch pole, from stamping tests with stretching characteristics. Analyses of the strain distribution profile and of the fracture position allow an evaluation of the lubrication efficiency. Of the five lubricants studied, the results indicated that the solid polyurethane film yielded the best performance, promoting a more homogeneous distribution profile of the minor true strain (ε2), increasing from the die radius to the punch pole, where tearing of the metal sheet occurred.