Evaluation of Contact Pressure in Bending under Tension Test by a Pressure Sensitive Film

Luis Fernando Folle,Lirio Schaeffer

doi:10.4236/jsemat.2016.64018

Abstract

The contact pressure acting on the sheet/tools interface has been studied because of growing the concern about the wear of tools. Recent studies make use of numerical simulation software to evaluate and correlate this pressure with the friction and wear generated. Since there are many studies that determine the coefficient of friction in sheet metal forming by bending under tension (BUT) test, the contact pressure between the pin and the sheet was measured using a film that has the ability to record the applied pressure. The vertical force applied to pin was also measured. The results indicate that the vertical force is more accurate to set the contact pressure that using equations predetermined. It was also observed that the contact area between the sheet and the pin is always smaller than the area calculated geometrically. The friction coefficient was determined for the BUT test through several equations proposed by various authors in order to check if there is much variation between the results. It was observed that the friction coefficient showed little variation for each equation, and each one can be used. The material used was the commercially pure aluminum, alloy Al1100.

Highlights

For the bending under tension (BUT) test as in a stamping piece, the contact pressure is difficult to measure
1) Evaluation of the Contact Pressure by Pressure Sensor With the intention of measuring the contact pressure which acts on the pin in the BUT test, a polymer film capable of measuring the pressure between two surfaces was used
Regarding the measurement of contact pressure with the Pressurex® film: The Pressurex® film proved to be effective in predicting the pressures associated with contact of the sheet with the pin, which is in full agreement with the results obtained by other authors

Summary

Introduction

For the BUT test as in a stamping piece, the contact pressure is difficult to measure. There are efforts to determine this pressure, but currently only the result given by numerical simulation is known. Schaeffer 202 the contact between the sheet and pin. It was shown that this pressure profile occurs in the same way in the die radius. In 1997, Sniekers and Smits [1] demonstrated through finite element simulation of the BUT test that the contact pressure between the sheet and the pin had an irregular profile and that there were two major peaks of pressure

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Results

Conclusion