Study on surface asperity flattening during uniaxial planar compression
In order to develop the relationship between surface roughness, friction and texture in the uniaxial planar compression, Al 6061 samples are compressed in a channel-die to conduct plane-strain compression experiments. Molly bond is selected as a lubricant in a group of samples. The other group of samples is compressed without lubrication. The tool is polished smoothly; all the samples are prepared with the same method to retain the same surface roughness. Finite element modelling of the surface asperity flattening is carried out with ABAQUS under the same experimental conditions, original random textures are employed in the two dimensional model. The same surface roughness (Ra) obtained from the experiment is also employed on the top surface of the sample. The constitutive model and time-integration procedure have been implemented into the implicit finite element code ABAQUS using user material subroutine UMAT. Both the calculated results and the experimental results show a same tendency: the lubrication can constrain the process of surface asperity flattening. When the reduction is less than 10%, the effect of lubrication on surface asperity flattening is not significant. If the reduction is 10–40%, the lubrication plays a satisfactory role during the compression. With an increase of reduction, the lubrication will be damaged, and then the sample compressed with and without lubrication keeps a similar tendency of change.