ASTM_E_1049_-_85_2011e1.pdf

Designation:E104985(Reapproved 2011)1Standard Practices forCycle Counting in Fatigue Analysis1This standard is issued under the fixed designation E1049;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.1NOTEReference(12)was editorially corrected in October 2011.1.Scope1.1 These practices are a compilation of acceptable proce-dures for cycle-counting methods employed in fatigue analysis.This standard does not intend to recommend a particularmethod.1.2 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E912 Definitions of Terms Relating to Fatigue Loading;Replaced by E 1150(Withdrawn 1988)33.Terminology3.1 Definitions:3.1.1 constant amplitude loadingin fatigue loading,aloading in which all of the peak loads are equal and all of thevalley loads are equal.3.1.2 cyclein fatigue loading,under constant amplitudeloading,the load variation from the minimum to the maximumand then to the minimum load.NOTE1In spectrum loading,definition of cycle varies with thecounting method used.3.1.3 mean crossingsin fatigue loading,the number oftimes that the load-time history crosses the mean-load levelwith a positive slope(or a negative slope,or both,as specified)during a given length of the history(see Fig.1).3.1.3.1 DiscussionFor purposes related to cycle counting,a mean crossing may be defined as a crossing of the referenceload level.3.1.4 mean load,Pmin fatigue loading,the algebraicaverage of the maximum and minimum loads in constantamplitude loading,or of individual cycles in spectrum loading,Pm5Pmax1Pmin!/2(1)or the integral average of the instantaneous load values orthe algebraic average of the peak and valley loads of a spec-trum loading history.3.1.5 peakin fatigue loading,the point at which the firstderivative of the load-time history changes from a positive toa negative sign;the point of maximum load in constantamplitude loading(see Fig.1).3.1.6 rangein fatigue loading,the algebraic differencebetween successive valley and peak loads(positive range orincreasing load range),or between successive peak and valleyloads(negative range or decreasing load range);see Fig.1.NOTE2In spectrum loading,range may have a different definition,depending on the counting method used;for example,“overall range”isdefined by the algebraic difference between the largest peak and thesmallest valley of a given load-time history.3.1.6.1 DiscussionIn cycle counting by various methods,it is common to employ ranges between valley and peak loads,or between peak and valley loads,which are not necessarilysuccessive events.In these practices,the definition of the word“range”is broadened so that events of this type are alsoincluded.3.1.7 reversalin fatigue loading,the point at which thefirst derivative of the load-time history changes sign(see Fig.1).NOTE3In constant amplitude loading,a cycle is equal to tworeversals.3.1.8 spectrum loadingin fatigue loading,a loading inwhich all of the peak loads are not equal or all of the valleyloads are not equal,or both.(Also known as variable amplitudeloading or irregular loading.)3.1.9 valleyin fatigue loading,the point at which the firstderivative of the load-time history changes from a negative to1These practices are under the jurisdiction of ASTM Committee E08 on Fatigueand Fracture and are the direct responsibility of Subcommittee E08.04 on StructuralApplications.Current edition approved Oct.1,2011.Published October 2011.Originallyapproved in 1985.Last previous edition approved in 2005 as E104985(2005).DOI:10.1520/E1049-85R11E01.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 a positive sign(also known as trough);the point of minimumload in constant amplitude loading(see Fig.1).3.2 Definitions of Terms Specific to This Standard:3.2.1 loadused in these practices to denote force,stress,strain,torque,acceleration,deflection,or other parameters ofinterest.3.2.2 reference loadfor spectrum loading,used in thesepractices to denote the loading level that represents a steady-state condition upon which load variations are superimposed.The reference load may be identical to the mean load of thehistory,but this is not required.3.3 For other defini