ASTM_F_2650_-_13.pdf

Designation:F265013An American National StandardStandard Terminology Relating toImpact Testing of Sports Surfaces and Equipment1This standard is issued under the fixed designation F2650;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This terminology covers terms related to impact testmethods and impact attenuation specifications of sports equip-ment and surfaces.1.2 This terminology is appropriate for use in the develop-ment of standards that describe gravity-driven impact testmethods or specify impact attenuation performance criteria andwhich fall under the jurisdiction of ASTM Committee F08 onSports Equipment and Facilities.1.3 This terminology defines common terms that are appli-cable to many sports-related impact tests including those usedin the context of sports surfaces,athletic footwear,protectiveequipment and padding.The use of a common terminologywill promote greater consistency among standards and reducethe risk of misinterpretation.1.4 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.2.Terminology2.1 Definitions:acceleration,nrate of change of velocity with time.DISCUSSIONAcceleration is a vector quantity,having both magni-tude and direction.Acceleration magnitude is expressed in units ofm/s2(ft/s2)and direction is defined relative to a Cartesian coordinatesystem or other spatial reference frame.assisted impact test,nan impact test in which the missile isaccelerated by means other than gravity alone,for example,by an actuator.drop height(h),nheight from which a missile is droppedduring a gravity-driven impact test,measured as the verticaldistance between the lowest point of the elevated missile andits first point of contact with the impacted surface or anvil.theoretical drop height,ndrop height(h)that,understandard conditions,would result in an impact velocity equal toa missiles measured impact velocity(V0).DISCUSSIONThe“standard conditions”assume standard gravity andthat friction and air resistance do not affect the fall of the missile.In afree-fall impact test the actual drop height will approximate thetheoretical drop height.In a guided impact test,the theoretical dropheight will be less than the actual drop height,due to the effects offriction in the guidance mechanism.g,n(pronounced“gee”)a unit of acceleration equal tostandard gravity.Missile accelerations expressed in g unitsare the ratio of the missile acceleration to standard gravityand are hence dimensionless.DISCUSSIONThe symbol g is properly written in lowercase anditalic,to distinguish it from the symbol G(uppercase,used to indicatethe gravitational constant)and g(not italicized)which is an abbrevia-tion of the gram unit.g-max,nmaximum acceleration magnitude recorded duringa single impact,expressed in g units.average g-max,narithmetic average of a specified set ofg-max values.gravity-driven impact test,nan impact test in which themissile is accelerated by gravity alone,during a period offree-fall.head injury criterion(HIC),nweighted impulse criterioncalculated from a head impact acceleration-time profile andused to quantify head impact severity.The HIC calculationresults in a severity index that is weighted by both impactacceleration magnitude and by the time for which highmagnitude accelerations persist.DISCUSSIONHIC scores can only be directly referenced to the headinjury risk data on which the criterion is based if the impactacceleration-time profile is recorded using a human head or a biofidelicheadform.HIC scores determined using rigid missiles and headformstend to over estimate head injury risk.headform,nmissile with mass and geometry approximatingthose of the human head.biofidelic headform,nheadform with elastic propertiesapproximating those of the human head.rigid headform,nheadform fabricated from very stiffmaterials(for example,steel or aluminum)such that itsdeformation during an impact is negligible.1This terminology is under the jurisdiction of ASTM Committee F08 on SportsEquipment,Playing Surfaces,and Facilities and is the direct responsibility ofSubcommittee F08.80 on Common Terminology,Methods and Laboratory Prac-tices.Current edition approved June 1,2013.Published July 2013.Originally approvedin 2007.Last previous edition approved in 2007 as F2650 07.DOI:10.1520/F2650-13.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 impact attenuation,nreduction of loads produced in thecourse of an impact by means of a cushioning system ordevice,relative to a load criterion or to the loads producedby a reference system.DISCUSSIONLoad measures used to quantify impact magnitudeinclude force,acceleration,stress and pressure and their time deriva-tives.im