A Refined Friction Modeling for Lubricated Metal Forming Process

Abstract

In spite of the existence of a well-developed realistic friction model, it has only been applied to the simple geometric problems, such as the axisymmetric and plane strain conditions, where the formulations of lubricant transport can be decomposed into two characteristic equations. Accordingly, a unified procedure of combining the current lubrication/friction model and finite element code of metal forming has been developed in this article for either steady or unsteady three-dimensional process including both axisymmetric and plane strain cases. In the part of the lubrication analysis, a finite element method is derived for the average Reynolds equation that is appropriated for 3-D metal forming process, and regardless of whether the tooling/workpiece surfaces are in contact or not. With regard to the theory of asperity contact, in addition to the well-known smoothing and roughening effects, significant deformation of asperities could be caused by the elastic microwedges on the tool surface. The availability of the new friction model was proved by a published problem and an axisymmetric stretch forming process was therefore adopted as a benchmark. Numerical results showed that the present analysis provides a good agreement with the measured strain distributions. Keywords Friction model Á Finite element method Á Lubrication Á Asperity contact Nomenclatures A contact area ratio (fractional contact area) ¶A increasing rate of contact area ratio; dA/dt ¶A I component of ¶A induced by indentation effect ¶A M component of ¶A induced by microwedge effect ¶A R component of ¶A induced by roughening effect B geometric matrix C coefficient of microwedge model C R coefficient of surface roughening model dA 0 differential undeformed area D material matrix E t tangent modulus E w

Frictional Conditions of AA5251 Aluminium Alloy Sheets Using Drawbead Simulator Tests and Numerical Methods

“…The quality of the products and the efficiency of the drawing process depend on several parameters. Friction regimes encountered during deep drawing in particular are known to be extremely complex [1] and [2]. This is as a result of the inherent factors, such as the contact pressure, sliding velocity, surface roughness at sheet metal and tool interface, material properties of the tool and the blank, and the properties of the lubrication.…”

Prediction of surface topography in lubricated sheet metal forming

“…The values of H t , A and p n in the work zone can be determined from the above lubrication/friction analysis, regardless of whether the tooling/workpiece surfaces are in contact. Yang [16] further described the procedure of lubrication/ friction analysis during the stretch forming process. The surface roughness in the free deformation region of the workpiece (R qf ) is given by Eq.…”

“…Numerical results showed that the inclusion of microwedge in the analysis provides a good agreement with the experimental measurements. Yang [16] and Yang [17] developed a unified procedure of combining a new tribological model and finite element code of metal forming for either steady or unsteady process. The availability of the new friction model was proved by an axisymmetric stretch forming process.…”

“…Strain distribution for middle speed condition[16]. (The finite element lubrication analysis and the asperity deformation theory that takes account of flattening, roughening and tool elastic microwedge effects on workpiece surface used in Yang[16].)…”

“…(The finite element lubrication analysis and the asperity deformation theory that takes account of flattening, roughening and tool elastic microwedge effects on workpiece surface used in Yang[16].) Strain path for different lubrication condition…”