Accuracy of Gmax / HIC Measurements

John I. Dunlop/Hans J. Kolitzus

11-Feb-2002

Round Robin - g-max and HIC

One of the stated aims of the ISSS is the assessment and standardisation of test methods for sports surfaces. To this end we have conducted a round Robin of impact testing equipment and techniques used for soft fall material testing.

Time frame

During the period November 2000 to November 2001 samples were circulated to 6 testing laboratories for impact testing.

Trial Controller:                       H.J. Kolitzus

Samples

The 2 samples circulated for testing were:

Sample 1          PUR Bound Rubber Fibres (Tile) roughly 61 mm thick

Sample 2          PUR Bound Rubber Fibres (Tile) roughly 41 mm thick

Testing Regime

The laboratories were requested to conduct impact tests on the samples under the following conditions:

Sample temperature - reported ambient after conditioning for at least 24 hr

Base - thick concrete of thickness in excess of 100 mm, with smooth finish

Drop Heights - 4, 5 and 6 feet

Determined values of g-max and HIC for the first drop were to be reported for each of these drop heights for each sample.

Laboratories/Equipment

Acousto-Scan, Sydney, Australia 5 kg ISO J head
CST, London, England  10 lb EN1177 hemi head
IST, Eschenz, Switzerland  10 lb EN1177 hemi head
Labosport, Le Mans, France 10 lb EN1177 hemi head
North West Testing Laboratory, Seattle, USA 10 lb EN1177 hemi head 
USSL, Hopewell, VA, USA 10 lb EN1177 hemi head

 

Two of the laboratories tested the samples twice, once early in the trial and again at the end of the trial (eg. Lab02-2 in 2001 and Lab03-2 in2002) to check on changes to the samples.

Results

The results of the testing (laboratories coded) are summarized in Fig. 1 and 2.

These figures show the deviations from the global average of each of the laboratory's tests.

Comments

The results indicate a remarkable consistency of test results considering the range of laboratories, testing and equipment.

The consistency within each laboratory's results is very high showing a small range of variability. The variations between laboratories indicate systematic differences in their equipment and techniques. However this should be viewed in terms of the general uncertainty of the measurements. Acousto-Scan has calculated the uncertainty of its g-max determination at 4 % and of its HIC at 5 % using the methods outlined in the ISO publication Guide to the Expression of Uncertainty in Measurements, 1993

HJK+JID

Nov 02