Scale Dependence of Adhesion Behavior under Dry Friction in Progressive Micro-Deep Drawing

Abstract

The present study aims to clarify the scale dependency of progressive adhesion behavior of work material on micro tools under the dry friction in microforming. Scaled progressive deep drawing test up to 300 times is conducted under dry condition in micro-and milli-scale. The process dimensions of 0.97mm and 5.82mm in drawn cup diameter are produced with the stainless steel foils of 0.05mm and 0.3mm in thickness, respectively. The experimental results show that the transition of maximum punch force has different tendencies in each scale. These tendencies are well corresponded to the transition in surface state of tools and drawn cups. While, the strong adhesive wear is observed for the milli-scale, there is a slight change in the surface state of the tools for micro-scale. To investigate this difference in the adhesion behavior of the work material in each scale, a finite element analysis considering surface asperities is conducted. The distribution of the adhesion volume on the die corner radius is evaluated with a semi-empirical wear model in which is calculated with a function of normal pressure and relative velocity between blank and die. The results show the low adhesion volume in micro-scale, due to the short sliding distance during the process. The progressive adhesion behavior of work material and the advantage of tool life in micro-scale metal forming are demonstrated.

Effects of TiO2 nanoparticle lubricant on micro deep drawing performance

“…This phenomenon can be described via the last stroke drawing force, because the punch is squeezed by the micro products at the end of the drawing process, and then the last stroke force is generated. Furthermore, when the more strain energy needs to be released at the end of MDD, more force compresses the punch and is transferred to the force sensor [29,31,32]. The last stroke drawing force in all of conditions is plotted in Fig.…”

Friction related size-effect in microforming – a review

“…The analysis suggests that the relative short sliding length and small variation in surface roughness for the micro scale is responsible for the lower volume of wear of the work material. Thus, with the miniaturization of the process dimensions, the influence of the plowing by the adhered particles on the frictional properties seems to decrease [45]. On the other hand, investigations regarding the tool life show that the punching edge wears out quicker than the rest of the tool for the high contact pressure in a one-stroke micro blanking and deep drawing process used to produce micro-cups in high quantity with an outer diameter of 1 mm.…”

Effects of forming velocity on micro deep drawing performance with different blank thickness

“…However, the principle and theory of conventional plastic forming cannot be directly transferred to the micro scale due to the size effect, which can cause the difference on the stress flow, formability, fracture behaviour, and friction of the material between the macro scale and micro scale [11][12][13][14]. To produce thin walled, hollow, box or cup like products at micro scale, micro deep drawing (MDD) is a fundamental process of the micro plastic forming, and more complex micro products can be produced based on this technology [2,15]. Therefore, it is essential to find a theory to be used in producing high-quality micro parts and explain the frictional behaviour during the MDD [16][17][18][19].…”