REALISTIC RIOT HELMET IMPACT TESTING
Cathie L. Kessler, Ismail El Maach, Jean-Philippe Dionne, Steve Truttmann, Aris Makris
Med-Eng Systems Inc., Ottawa, Ontario, Canada
E-mail: [email protected] Web: www.med-eng.com
INTRODUCTION
Helmet standard testing [CSA, 2002] is
performed with a drop tower, with either
helmeted headforms dropped on fixed
anvils, or with stationary helmets being hit
by an impactor. Neither case is
representative of typical threats for which
the helmet was intended, in which the
wearer would be moved bodily upon impact,
absorbing a fraction of the energy through
inertia. In the current testing, a more
realistic case of a mannequin wearing a Riot
Helmet being hit by a baseball bat is
considered.
several relays and a solenoid-operated
pneumatic cylinder (Fig. 1). As the bat
swung, a lever passed through an optical
sensor, triggering both the release
mechanism and the data acquisition. Impacts
were aimed at three locations (crown, sellion
and tragion, Fig. 1), with the mannequin
either unprotected (no helmet) or protected.
In the unprotected case, five impacts were
performed at each location. For the
protected case, each site was impacted three
times (only one helmet used throughout).
All impacts were delivered with a bat
angular velocity of 28.8 rad/s (or 16.8 m/s).
METHODS
All testing was performed on a Hybrid II
mannequin representing the 50th percentile.
Baseball bat blows were generated with a
blunt impactor simulator [Dionne et. al,
2002], which consists of a pneumaticallydriven cam swinging the baseball bat in an
arc. One accelerometer (PCB Piezotronic
350A03) was installed on the baseball bat
(plane of motion) and three were located in
the head of the mannequin (oriented with its
Frankfort plane horizontal), positioned along
the axes of a right-handed coordinate
system. The origin of the coordinate system
was at the nasal root. Data was collected
through a computerized data acquisition
system at a rate of 10 kHz.
The mannequin was hung from a crane by a
yoke between the shoulder blades connected
to a quick-release mechanism, consisting of
1
3
2
Figure 1: Experimental apparatus and
impact sites: 1) Crown, 2) Sellion 3) Tragion
The Head Injury Criterion (HIC) was used
to assess the probable level of injury due to
head acceleration [Versace, 1971]. The HIC
is calculated as follows:
2.5

t 2
 

−1.5
HIC = (t 2 − t1 )  ∫ a(t )dt  
 t1
 

max
where t1 and t2 are chosen to maximize the
HIC parameter. This value was then used to
calculate the scores for the Abbreviated
SUMMARY
A free-falling mannequin was impacted in
the head, with and without head protection.
The head injuries sustained from these
blows were estimated using the Head Injury
Criterion (HIC) and the Abbreviated Injury
Scale (AIS), and a comparison was made
between unprotected and protected injuries.
The results show that for impacts from all
directions tested, wearing a helmet makes
100
Protected
90
Unprotected
AIS 2
0
AIS 1
10
Fatal
Severe
AIS 5
20
Serious
30
AIS 4
Moderate
40
AIS 3
50
Minor
60
Critical
70
AIS 6
80
No Injury
Values of the peak acceleration, HIC, and
average AIS are shown in Table 1. For the
unprotected impacts, the average of the five
impacts and the standard deviation are
shown. For the protected cases, values are
given for all three impacts, showing that the
results did not change significantly, despite
using the same helmet for all impacts.
Figure 2 shows the full set of AIS values for
the protected and unprotected cases of
impacting the mannequin directly in the face
(sellion). Without head protection, there was
a 40% probability of sustaining a critical
injury (AIS 5) and a 21% chance of
sustaining a fatal injury (AIS 6), whereas
wearing a helmet provided enough
protection to ensure a 100% probability of
no injury (AIS 0).
AIS 0
RESULTS AND DISCUSSION
the difference between sustaining a
potentially lethal injury and remaining
virtually unharmed. These tests differ from
those required by most helmet standards, in
that an unrestrained mannequin was used,
thereby accounting for imparted inertia.
Further, a realistic impact was generated.
These, together, make the testing much more
representative of actual use, and also make
comparisons with the unprotected case
possible.
Probability [% ]
Injury Scale (AIS), which gives the
probability of the injury falling into various
levels of severity [Prasad et. al, 1985]. A
weighted average of the AIS values obtained
for the given HIC was also calculated.
Figure 2: Injury levels for protected and
unprotected impacts in the face (sellion).
REFERENCES
1. Canadian Standards Association (2002),
Standard Z611-02
2. Dionne, J.P. et al. (2002). Proceedings
of European Society of Biomechanics,
Wroclaw, Poland
3. Versace, J. (1971). Proceedings of 15th
Stapp Car Crash Conference, 771-796
4. Prasad P, Mertz HJ (1985), Society of
Automobile Engineers, SAE Paper
Number 85-1246
Table 1: Results for Impacts of Protected and Unprotected Mannequin Heads
Impact
Site
Tragion
Sellion
Crown
Unprotected – Average of 5 (± SD)
Avg. Peak
Avg.
Avg.
Acc. (g’s)
HIC
AIS
500 (10)
1854 (67)
4.4
502 (15)
1946 (180)
4.7
538 (27)
2115 (187)
5.1
Protected
Peak Acc.
(g’s)
60
58
42
35
87
97
HIC
57
48
95
41
34
129
Avg. AIS
41
18
140
37
29
144
0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0