ASTM F2650-13

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Designation: F2650 − 13 An American National Standard
Standard Terminology Relating to
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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.
1. Scope theoretical drop height, n—drop height (h) that, under
standardconditions,wouldresultinanimpactvelocityequalto
1.1 This terminology covers terms related to impact test
a missile’s measured impact velocity (V ).
0
methods and impact attenuation specifications of sports equip-
DISCUSSION—The “standard conditions” assume standard gravity and
ment and surfaces.
that friction and air resistance do not affect the fall of the missile. In a
free-fall impact test the actual drop height will approximate the
1.2 This terminology is appropriate for use in the develop-
theoretical drop height. In a guided impact test, the theoretical drop
ment of standards that describe gravity-driven impact test
height will be less than the actual drop height, due to the effects of
methodsorspecifyimpactattenuationperformancecriteriaand
friction in the guidance mechanism.
which fall under the jurisdiction of ASTM Committee F08 on
g, n—(pronounced “gee”) a unit of acceleration equal to
Sports Equipment and Facilities.
standard gravity. Missile accelerations expressed in ‘g’units
1.3 This terminology defines common terms that are appli-
are the ratio of the missile acceleration to standard gravity
cable to many sports-related impact tests including those used
and are hence dimensionless.
in the context of sports surfaces, athletic footwear, protective
DISCUSSION—The symbol g is properly written in lowercase and
equipment and padding. The use of a common terminology
italic, to distinguish it from the symbol G (uppercase, used to indicate
will promote greater consistency among standards and reduce
the gravitational constant) and g (not italicized) which is an abbrevia-
the risk of misinterpretation.
tion of the gram unit.
1.4 The values stated in SI units are to be regarded as the
g-max, n—maximum acceleration magnitude recorded during
standard. The values given in parentheses are for information
a single impact, expressed in ‘g’ units.
only.
average g-max, n—arithmetic average of a specified set of
g-max values.
2. Terminology
gravity-driven impact test, n—an impact test in which the
2.1 Definitions:
missile is accelerated by gravity alone, during a period of
acceleration, n—rate of change of velocity with time.
free-fall.
DISCUSSION—Acceleration is a vector quantity, having both magni-
tude and direction. Acceleration magnitude is expressed in units of
head injury criterion (HIC), n—weighted impulse criterion
−2
−2
m/s (ft/s ) and direction is defined relative to a Cartesian coordinate
calculated from a head impact acceleration-time profile and
system or other spatial reference frame.
used to quantify head impact severity. The HIC calculation
assisted impact test, n—an impact test in which the missile is results in a severity index that is weighted by both impact
acceleration magnitude and by the time for which high
accelerated by means other than gravity alone, for example,
by an actuator. magnitude accelerations persist.
DISCUSSION—HIC scores can only be directly referenced to the head
drop height (h), n—height from which a missile is dropped
injury risk data on which the criterion is based if the impact
during a gravity-driven impact test, measured as the vertical acceleration-time profile is recorded using a human head or a biofidelic
headform. HIC scores determined using rigid missiles and headforms
distancebetweenthelowestpointoftheelevatedmissileand
tend to over estimate head injury risk.
its first point of contact with the impacted surface or anvil.
headform, n—missile with mass and geometry approximating
those of the human head.
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This terminology is under the jurisdiction ofASTM Committee F08 on Sports
biofidelic headform, n—headform with elastic properties
Equipment, Playing Surfaces, and Facilities and is the direct responsibility of
approximating those of the human head.
Subcommittee F08.80 on Common Terminology, Methods and Laboratory Prac-
tices.
rigid headform, n—headform fabricated from very stiff
CurrenteditionapprovedJune1,2013.PublishedJuly2013.Originallyapproved
materials (for example, steel or aluminum) such that its
in 2007. Last previous edition approved in 2007 as F2650 – 07. DOI: 10.1520/
F2650-13. deformation during an impact is negligible.
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