A Study of the Application of Low Frequency Oscillations to Multi-Tool Drawing Processes

Abstract

Within the last decade a number of researchers have
investigated the effects of applying vibrations to the
tooling when forming metals. Sane of these investigations
indicate that vibrations may modify the state of stress in
the body of the de forming metal and/or change the fricional
boundary conditions between the tools and the workpiece.

The first part of this thesis describes and discusses
the research so far conducted in this field of metalworking,
and attempts to isolate the areas of possible benefit to
industrial practice. The remainder of this thesis describes
the progress, and presents and discusses the results of a
two-part investigation into the application of low frequency
‘axial vibrations (O to 100 Hz) to the tandem wire and fixed
plug tube drawing processes.

The investigation was conducted on a 2000 lbf horizontal
bull block, the tools being oscillated by two electrohydraulic
vibrators, Mild steel wire and medium carbon
steel tube were selected for the workpieces, and sodium
stearate, as the lubricant.

Results show that when wire is drawn through two dies
in tandem which are oscillated axially and in anti-phase; or
when tube is drawn through the annular gap between a die and
a fixed plug which are oscillated axially in antiphase:
(a) The workpiece moves relative to the tools for a
short period on every cycle.
(b) During the remainder of the cycle the drawn product
is elastically off-loaded and loaded by the motion
Of the tooling,
(c) The workpiece moves alternately over each tool.
(d) The peak load in the drawn product is reduced
by oscillations, since the product never
experiences the force necessary for movement
relative to both tools simultaneously.
(e) There is no indication of a reduction in yield
stress or frictional coefficient produced by the
application of oscillations,
(f) The reduction in peak drawing force is most
marked for high frequencies and amplitudes, and
low drawing speeds.

A theoretical analysis was conducted for single die
oscillatory wire drawing to establish the basic mechanics of
the process. This analysis was extended to cover the tandem
wire drawing process which produced predictions of the upper
and lower limits of the peak drawing force reductions.
Experimental data was found to fall within these predicted
limits.

The results of the investigation are discussed and
suggestions for further work are presented

Date of Award	1972
Original language	English