A novel approach for microscale dry contact stiction and friction assessment: Experimentation and analysis

Abstract

Accurate and quantitative evaluation of friction is of fundamental interest for materials science and manufacturing. Driven by the trend towards miniaturization, micro metal forming techniques with characteristic forming dimensions approaching a few microns have developed rapidly over the past two decades. In contrast, the assessment of microscale friction is lagging. Here, we present a novel test, compression molding and demolding test (CMDT), to assess stiction and friction at the microscale. CMDT was conducted via in-situ instrumented molding and demolding of an Al specimen with cylindrical tool steel and Ti alloy punches. High-rate data acquisition enabled direct measurements, for the first time, of microscale stiction and friction forces during disengagement between the punches and the molded Al under dry contact conditions. Stiction and friction stresses were then deduced and analyzed. The average friction coefficient was estimated by combining the cavity expansion model and finite element method analysis. Examinations suggest that punch geometry and surface finish, together with the accuracy of estimating the sidewall contact pressure, influence the obtained friction coefficient values. CMDT exhibits merits such as high operation simplicity and measurement accuracy and offers an alternative approach to providing new experimental evidence for a range of microscale friction problems.

Keywords

• Micro metal forming
• Compression molding and demolding test
• Measurement of stiction and friction forces
• Microscale friction coefficient estimation