The influence of die geometry and workpiece mechanical properties in T-Shape friction test

Abstract

a b s t r a c tIn this study, T-Shape friction test was redesigned to make it more suitable for application to microforming processes. Workpiece with aspect ratio (length/diameter) of 5 was proposed in order to ease workpiece handling. The die geometry was also modified from the original test to improve friction sensitivity especially within the range of friction factors commonly observed in metal forming. Geometric deviation of the die was simulated using Deform-2D to establish the acceptable tolerance for the fabrication. The effect of variation in workpiece mechanical properties on the test behavior was also investigated through Deform-2D simulation. Based on simulations on a 1 mm diameter copper workpiece, a tolerance of 0.01 mm (1% of workpiece diameter) was found to be the most suitable for the die fabrication. In addition, it was shown that variations in workpiece mechanical properties of up to 10% do not significantly influence the friction test results. Ultimately, T-Shape test experiment was conducted using copper workpieces to examine how the test complied with the friction behavior observed in the experiment.

On the influence of workpiece material on friction in microforming and lubricant effectiveness

“…Nevertheless, Taureza et al (2012) presented a contradicting example and showed that the friction calibration curves in T-Shape test are non-sensitive to up to 10 percent flow stress deviation.…”

Friction Effects During Open-die Micro-forging/Extrusion Processes: An Upper Bound Approach

“…There is a large variety of tests for friction coefficient determination; although, only a few of them are applicable to scaling experiments (Taureza et al, 2012). A conventional method to study the effect of miniaturization on friction (friction size effect) is the ring compression test, for which an increase in friction is reported by scaling down .…”

Optimization of a progressive microforming process and in-process material behavior

“…Finite element (FE) simulation is a tool that can assist greatly in this effort. However, FE simulation of microforming processes has always been a challenge due to different types of size effects occurring in such length scale [21,55,102,136,137,179]. One such challenge is to define the correct friction factor, so that FE simulation results can match the experimental results.…”

“…There is a large variety of tests for friction coefficient determination; although, only a few of them are applicable to scaling experiments [28,76,101,102]. A conventional method to study the effect of miniaturization on friction (friction size effect) is the ring compression test, for which an increase in friction is reported by scaling down [28,41,103].…”

“…In micro-forming processes, it is preferred not to use lubricants, due to their complex behavior in micro-scale [114]. Nevertheless, this made the topic attractive to the scientific society and has led to a vast number of related reports about lubrication size effects [102,107,120,198].…”