Ehlenz T (2020)
Publication Language: German
Publication Type: Thesis
Publication year: 2020
Publisher: Shaker
City/Town: Düren
As part of a cooperative doctorate between the Friedrich-Alexander University of Erlangen
Nuremberg and the University of Applied Sciences Trier, cables and transmission lines that
users primarily perceive as electrical components have been researched similar to the
established failure and dimensioning scheme of a machine element. The current work deals
with the investigation of mechanically stressed cables and lines. Their use should get more
reliable and the point of time for exchange of permanently moved lines be optimized. Cables
in moving applications have highly complex electrical and mechanical requirements that are
currently under-researched or insufficiently standardized. As it is common with other machine
elements, operating time cannot be calculated. Especially with regard to Industry 4.0,
unscheduled machine downtimes could become critical. With accelerated aging tests,
manufacturers and users try to test their products in an increasingly shorter time-to-market.
They use the alternating bending test, described in DIN EN 50396 to verify the cables’
conformance. The research shows that the requirements of the standard are insufficiently
described. After improvements of the test operations, which focused on the reproducibility, the
alternating bending test defines the starting point of the multiphysical lifetime tests. Based on
the findings of the parameter studies, a proposed standard for improving the test standard DIN
EN 50396 was submitted to the responsible parent body. With the multiphysical recording of
the course of damage during endurance tests, relevant wear patterns for moving lines can be
identified. They form a novel phase model of the service life of mechanically dynamic loaded
cables. The investigations show that structural changes and surface roughness of the copper
material occur under prolonged mechanical stress before fracturing of the probands. Changes
in the edge regions of the electrical material can be measured, making use of the skin effect. In
conductors that are carrying high-frequency currents, the current density concentrates at the
peripheric region of the conductor. An incipient roughness of the conductor leads to a change
in the attenuation of a signal to be transmitted. In the run-up to empirical experiments,
corresponding electrodynamical simulations on modelled conductors confirm the assumption.
They show the increased current density at the peripheric area of a correspondingly aged, rough
conductor. In subsequent empirical tests, an exchange time of test lines can be detected with insitu
high-frequency attenuation measurement. The high-frequency measurement is a
nondestructive, in-situ diagnostic option for mechanical cable wear. The measurement method
is suitable for the commercial use of a later cable monitoring system, in which lines can be
evaluated during their operation with regard to estimated remaining lifetime. The research
results contribute to a predictable product life of the mechanically loaded electrical lines and
thus to increased reliability in many industries.
APA:
Ehlenz, T. (2020). Multiphysikalische Betrachtung von Kabeln und Leitungen unter mechanisch-dynamischer Belastung (Dissertation).
MLA:
Ehlenz, Tobias. Multiphysikalische Betrachtung von Kabeln und Leitungen unter mechanisch-dynamischer Belastung. Dissertation, Düren: Shaker, 2020.
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