Civil Engineering Reference
In-Depth Information
loads. This examination focused on the surface roughness under both elastic and
plastic loadings, over the entire apparent area of the specimen. The following are a
list of conclusions about the EAF/contact area research:
• The post-formed surface roughnesses at the die/workpiece interfaces become
worse as a higher magnitude of applied electricity is used.
• There is a clear trend in that, as the applied static load is increased for a given
amount of current, the overall temperature of the specimen will decrease.
However, this was found to only be valid within the elastic regime on the
specimen. For the enhanced asperity specimens, where the plastic regime was
reached in the asperity region, the temperature from the stationary electrical
tests did not change.
• The EEC proiles from the same EAF tests run on surface ground specimens
and specimens with enhanced asperities were very similar, thus indicating that
the contact area does not have much of an effect on effectiveness of EAF out-
side of the elastic region. Hence, this is possibly why there is such a focus on
contact area for electrical connectors, where all components are in the elastic
region.
• When attempting to model the EAF technique for a forging process, the contact
area is insignificant because the manufactured part will always be in the plastic
region since it is being deformed.
9.2 Tribological Effect on EAF Effectiveness
This section will contain an exploration into the effects of applied electricity on
tribology within an EA-Forging process [
13
,
14
]. Specifically, (a) the general
effects of the electricity on tribological conditions will be explained, (b) the exper-
imental setup and procedure for this section will be described, (c) the method by
which the friction calibration curves were determined will be given, (d) test pro-
cedures will be stated, (e) candidate metal forming lubricants will be introduced,
(f) experimental results and discussion will be detailed, (g) an evaluation of the
lubricants based on the reduction in the forming load will be noted, (h) tempera-
ture measurements will be provided, and (i) the section will be summarized with
conclusions.
Because most metal forming operations incorporate some type of lubricant, it
is necessary to understand how different lubricant compositions/types react while
used in an EAF compression test. Although there is no true record that traces
lubricant use to a particular time period, it can be assumed that lubricants were
being used to assist metal deformation as early as fifth century B.C. Until the
mid-1940s, lubricants remained relatively unrefined, consisting of seed or animal
oils/greases. Around the later part of the twentieth century, increasing demands
from the aerospace, chemical, and electronic industries led to the development of
new exotic metals with which ordinary lubricants were not sufficient. These new
