Abstract
Friction at the interface between strips and dies is an important factor influencing the formability of strip or sheet forming. In this study, the frictional behaviors of strips at variant speeds were investigated using a self-developed strip friction test machine with a dual tension mechanism. This friction test machine, stretching a strip around a cylindrical friction wheel, was used to investigate the effects of various parameters, including sliding speeds, contact angles, strip materials, and lubrication conditions on friction coefficients at the strip–die interface. The friction coefficients at the strip–die interface were calculated from the drawing forces at the strip on both ends and the contact angle between the strip and die. A series of friction tests using carbon steel, aluminum alloy, and brass strips as the test piece were conducted. From the friction test results, it is known that the friction coefficients can be reduced greatly with lubricants on the friction wheel surface and the friction coefficients are influenced by the strip roughness, contact area, relative speeds between the strip and die, etc. The friction coefficients obtained under various friction conditions can be applied to servo deep drawing or servo draw-bending processes with variant speeds and directions.
Highlights
Friction conditions between the workpiece and die influence the deformed sheet or strip material properties significantly
Tamai et al [1] proposed a friction test apparatus, in which two identical compressive forces act on the test piece surfaces and a drawing force is imposed at one end of the test piece
Tamai et al [4] developed a nonlinear friction coefficient model that considers contact pressure, sliding velocity, and sliding length to improve the accuracy of predictions of the formability of steel sheets
Summary
Friction conditions between the workpiece and die influence the deformed sheet or strip material properties significantly. They found that the friction coefficients of the steel sheet with the pins increased with the strip strain. Kim et al [8] measured the friction coefficient to investigate the friction characteristics of a coated metal and found that tool steel STD11 and copper alloys AMPCO have better surface roughness and formability than other metals. Lemu and Trzepiecinski [9] explored the friction behavior of steel, brass, and aluminum alloys with a self-developed friction test apparatus and discussed the effects of the deformation strains on the friction coefficient under dry and lubricated conditions. The experimental results showed that the friction coefficient decreased with the increase of sliding speed and normal load for aluminum sheets.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
