ASTM F2650-07

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Designation: F2650 − 07 AnAmerican National Standard
Standard Terminology Relating to
1
Impact Testing of Sports Surfaces and Equipment
This standard is issued under the fixed designation F2650; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
height will be less than the actual drop height, due to the effects of
1. Scope
friction in the guidance mechanism.
1.1 This terminology covers terms related to impact test
methods and impact attenuation specifications of sports equip- g, n—(pronounced “gee”) a unit of acceleration equal to
ment and surfaces.
standard gravity. Missile accelerations expressed in ‘g’units
are the ratio of the missile acceleration to standard gravity
1.2 This terminology is appropriate for use in the develop-
and are hence dimensionless.
ment of standards that describe gravity-driven impact test
DISCUSSION—The symbol g is properly written in lowercase and
methodsorspecifyimpactattenuationperformancecriteriaand
italic, to distinguish it from the symbol G (uppercase, used to indicate
which fall under the jurisdiction of ASTM Committee F08 on
the gravitational constant) and g (not italicized) which is an abbrevia-
Sports Equipment and Facilities.
tion of the gram unit.
1.3 This terminology defines common terms that are appli-
g-max, n—maximum acceleration magnitude recorded during
cable to many sports-related impact tests including those used
a single impact, expressed in ‘g’ units.
in the context of sports surfaces, athletic footwear, protective
average g-max, n—arithmetic average of a specified set of
equipment and padding. The use of a common terminology
g-max values.
will promote greater consistency among standards and reduce
the risk of misinterpretation.
head injury criterion (HIC), n—weighted impulse criterion
1.4 The values stated in SI units are to be regarded as the
calculated from a head impact acceleration-time profile and
standard. The values given in parentheses are for information
used to quantify head impact severity. The HIC calculation
only.
results in a severity index that is weighted by both impact
acceleration magnitude and by the time for which high
2. Terminology
magnitude accelerations persist.
2.1 Definitions: DISCUSSION—HIC scores can only be directly referenced to the head
injury risk data on which the criterion is based if the impact
acceleration, n—rate of change of velocity with time.
acceleration-time profile is recorded using a human head or a biofidelic
DISCUSSION—Acceleration is a vector quantity, having both magni-
headform. HIC scores determined using rigid missiles and headforms
tude and direction. Acceleration magnitude is expressed in units of
−2
−2
tend to over estimate head injury risk.
m/s (ft/s ) and direction is defined relative to a Cartesian coordinate
system or other spatial reference frame.
headform, n—missile with mass and geometry approximating
drop height (h), n—height from which a missile is dropped
those of the human head.
during a gravity-driven impact test, measured as the vertical
biofidelic headform, n—headform with elastic properties
distancebetweenthelowestpointoftheelevatedmissileand
approximating those of the human head.
its first point of contact with the impacted surface or anvil.
rigid headform, n—headform fabricated from very stiff
theoretical drop height, n—drop height (h) that, under
materials (for example, steel or aluminum) such that its
standardconditions,wouldresultinanimpactvelocityequalto
deformation during an impact is negligible.
a missile’s measured impact velocity (V ).
0
DISCUSSION—The “standard conditions” assume standard gravity and
impact attenuation, n—reduction of loads produced in the
that friction and air resistance do not affect the fall of the missile. In a
course of an impact by means of a cushioning system or
free-fall impact test the actual drop height will approximate the
device, relative to a load criterion or to the loads produced
theoretical drop height. In a guided impact test, the theoretical drop
by a reference system.
DISCUSSION—Load measures used to quantify impact magnitude
include force, acceleration, stress and pressure and their time deriva-
1
This terminology is under the jurisdiction ofASTM Committee F08 on Sports
tives.
EquipmentandFacilitiesandisthedirectresponsibilityofSubcommitteeF08.80on
Common Terminology, Methods and Laboratory Practices.
missile, n—inagravity-drivenimpacttest,theobjectmassthat
Current edition approved Aug. 1, 2007. Published September 2007. DOI:
10.1520/F2650-07. falls under gravity to produce an impact.
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