Influence of Surface Topographical Interaction between Tool and Material in Micro-Deep Drawing

Abstract

In the miniaturization of dimensions for sheet metal forming, the relative ratio of the surface asperities of tools and blanks to the outside dimensions becomes larger than that in the case of the conventional macroscale process. This means that the surface asperities may affect frictional behavior, so that it would also affect processing characteristics and accuracy of products. In this report, micro-deep drawing for producing cups of 700µm diameter and 20µm thickness is conducted using microtools and stainless steel foils with different surface conditions. To evaluate the effects of surface properties on micro-formability and micro-forming accuracy, punch force, surface accuracy, and the thickness strain distribution of microcups are experimentally investigated. Additionally, using a finite element (FE) model that considers surface roughness, the effect of surface roughness on formability is analyzed under different tool and material surface conditions. Results show that the global forming behavior in microforming is subjected much more intensely to tribological contact behavior, which is caused by the difference of surface asperities, than that in the case of the macroscale region. Moreover, it is shown that predominant factor over this local tribological behavior is the interaction of both tool/material surface asperities that depends on the normal load condition.

Impact of Surface Topography of Tools and Materials in Micro-Sheet Metal Forming

“…Thus, the difference in the effect of tool surface properties on friction is markedly observed. Fig.16 shows the surface images of the upper and the lower sides of the microcup wall of outer surface (Shimizu et al, 2009). The surface of the microcup has a large difference, as shown in the figure.…”

“…This surface model is constructed on whole surface elements of blank and tools. Some of the virtues to consider the surface asperity in the FE model are as follows (Shimizu et al, 2009):…”

“…It is possible to represent the local deformation of surface asperity caused by contact between the tool and the material. shows the distribution of equivalent plastic strain during the process with a surface roughness model (Shimizu et al, 2009). As shown in Fig.…”

“…Blank surface geometry (Shimizu et al, 2009). The curve obtained for the rough tool indicates the higher punch forces than those of the smooth tool.…”

Microdeep drawing of C1100 microsquare cups using microforming technology

“…Chen et al [9] confirmed that thickness, grain size, and foil thickness to grain diameter greatly influenced the LDR in microdeep drawing. Shimizu et al [10,11] reported that the surface asperities greatly affected the microformability and microforming accuracy in microdeep drawing. Geng et al [12] simulated microdeep drawing of copper single crystal by using crystal plasticity theory, and the results were similar to the experiments.…”