Page 56 - Prosig Catalogue 2005

SOFTWARE PRODUCTS
FATIGUE & DURABILITY TESTING - HOW DO I DO IT?

Training & Support The software does however retain the time versus angle travelled data Figure 2: Strain gauge mounted on component under test

Figure 10 Order Analysis of Synchronous Swept Sine

in another signal so that in practice no information is lost. This is shown
below in Figure 11.

P8000 portable data acquisition system. The vehicle was driven around a
test track and data from the strain gauges acquired with the P8000 data
acquisition unit. The data capture and signal processing procedure can be
seen and followed from start to finish.
Figure 2 shows an example of a strain gauge attached to the component
Condition Monitoring Because the rate of change of speed was a constant, then the time vs must be filled in such as signal names, signal types and so on. For the
under test by adhesive. In this case the gauge is a two wire device.
After launching the Prosig Data Acquisition software various setup fields

purposes of clarity in this application note only one strain gauge is being
used and it is operating in a quarter bridge completion configuration. It
angle travelled curve is of the form time = k*sqrt(angle).
is a 120 Ohm gauge and an excitation of 10VDC has been selected to be
applied as shown in Figure 3.
Fatigue & Durability

Testing - How Do I Do

It?

The following application note describes the test and measurement
Software process for the fatigue testing and development cycle of an automotive
suspension component, specifically a tie rod. The component had been
known to fail at various intervals. An estimate of the predicted fatigue
life of the component was required in order to assess the feasibility
of its continued use and to see if a design change was required. The
component under test is shown in Figure 1. The testing was carried out
by a major automotive manufacturer. Strain gauges were used to monitor
the strain levels. Figure 3: Acquisition setup screen

Hardware

Figure 1: Vehicle suspension under test Figure 4: Real time display of data
System Packages post shaker rig that simulates actual road conditions. Particular sections of Next the Prosig P8000 and associated acquisition software are used to
First, the vehicle was instrumented and data acquired whilst the vehicle
was on a test track. The vehicle under test was then mounted on a four-
capture the strain data from the vehicle as it driven around the test track.
the actual test run from the test track could be replicated for much longer
The real time display, Figure 4, shows the micro strain and the oscillatory
periods than otherwise would be possible, additionally this could all be
nature of the data as it is being captured.
done in the controlled conditions of the test laboratory.
On completion of the data capture stage, the next step was to return to
This article will focus on the capture of the strain data and the processing
the testing laboratory and use the vehicle shaker test rig. The DATS signal
of such data using ‘Stress Life’ and ‘Fatigue Life Prediction’ methods to
processing software was used to identify significant frequencies and
predict the expected life of the component.
amplitudes of strain data that the vehicle had been subject to on the test
56 Initially, the vehicle was instrumented with strain gauges using a Prosig track. The analogue output facility of the P8000 was then used to ‘replay’
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