ADR-Auto Range
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9901X0215 Issue 5
4.6.2.8 Failure Threshold
The definition of the Failure Threshold parameter depends on the form of pace
control selected, and if either the ACV (Aggregate Crushing Value) or TFV (Ten
Percent Fines Value) sample test modes have been selected. The parameter is
always entered as a load in the units defined for display. The following describes
each form of pace control and how the Failure Threshold is used.
Automatic
When automatic pace control is selected, the Failure Threshold parameter defines
the load at which the ADR-Auto starts looking for a failure. The machine ignores any
failures below this level and continues to apply load and control the pace rate. The
default setting is a percentage of the frame range, i.e. 8 kN for a 2000 kN load frame.
The actual percentage depends on the frame type. The threshold should be
increased if the sample under test can exhibit a false failure early on in the loading
cycle, as can happen when testing bricks capped with plywood.
If an ACV or TFV test has been selected when selecting the sample type, the Failure
Threshold has the same meaning, i.e. failures are not detected below the threshold
value, but in these two cases, the ADR-Auto stops pacing when the load attains the
level set in the Failure Threshold parameter. Note that the ADR-Auto sets a default
pace rate and threshold for ACV tests, but these must be user entered for TFV tests.
Manual
The same as automatic pace control.
Board
When Board pace control is selected, the Failure Threshold is automatically
determined by the ADR-Auto. Any value entered is ignored in Board control mode.
To update the Failure Threshold displayed, enter a new load using the numeric
keypad and then press the
Enter
key. If the
Enter
key is not pressed, the value will
not be updated. Use the
Clear
key to erase the entire entry.
4.6.2.9 Failure Detection (%)
The ADR-Auto detects a sample failure by measuring the peak load sustained by the
sample and waiting until the load has fallen by a defined percentage of this peak load.
Use the numeric keypad to change the default value. Increasing the percentage
means that the ADR-Auto continues to try to maintain the loading rate for a longer
time as the sample fails.
4.6.2.10 Zero Suppression Range
The ADR-Auto displays a load value of zero until the load exceeds the value in the
Zero Suppression Range entry. Use the numeric keypad to change the default value.
Set the value to zero if this facility is not required.
4.6.3 Selecting the Sample Type and Size
Having selected the operating mode and setup any options required for the mode, the
sample type and size should be selected. The ADR-Auto has a large database of
predefined sample types and sizes, and Appendix 1 lists those available along with
their associated pace rates. If the sample under test is not in the database, the
required pace rate and sample dimensions can be entered before the test is run.
Note that because the number of sizes and dimensions depend on the display
units selected, the display units (eg. kN) must be selected prior to choosing the
sample type and size.
