1、Designation: F 2118 03 (Reapproved 2009)Standard Test Method forConstant Amplitude of Force Controlled Fatigue Testing ofAcrylic Bone Cement Materials1This standard is issued under the fixed designation F 2118; the number immediately following the designation indicates the year oforiginal adoption o
2、r, 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 test method describes test procedures for evaluat-ing the constant amplit
3、ude, uniaxial, tension-compression uni-form fatigue performance of acrylic bone cement materials.1.2 This test method is relevant to orthopaedic bone ce-ments based on acrylic resins, as specified in SpecificationF 451. The procedures in this test method may or may notapply to other surgical cement
4、materials.1.3 It is not the intention of this test method to define levelsof performance of these materials. Furthermore, it is not theintention of this test method to directly simulate the clinical useof these materials.1.4 A rationale is given in Appendix X1.1.5 The values stated in SI units are t
5、o be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns associated with its use. It is the responsibilityof the user of this standard to consult and establish appropriatesafety and health practices a
6、nd determine the applicability ofregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 466 Practice for Conducting Force Controlled ConstantAmplitude Axial Fatigue Tests of Metallic MaterialsE 467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial
7、Fatigue Testing SystemE 1823 Terminology Relating to Fatigue and Fracture Test-ingF 451 Specification for Acrylic Bone Cement2.2 ISO Standard:ISO 7206-8 Implants for Surgery, Partial and Total Hip JointProstheses, Part 8Endurance Performance of StemmedFemoral Components with Application of Torsion33
8、. Terminology3.1 Unless otherwise given, the definitions for fatigue ter-minology given in Terminology E 1823 will be used.3.2 median fatigue strength at N cyclesThe maximumstress at which 50 % of the specimens of a given sample wouldbe expected to survive N loading cycles. For the purposes ofthis t
9、est method, the fatigue strength will be determined at 5million load cycles. A rationale for this is provided in theAppendix X1.4.3.3 runoutApredetermined number of cycles at which thetesting on a particular specimen will be stopped, and no furthertesting on that specimen will be performed. For the
10、purposes ofthis test method, the runout will be 5 million load cycles.3.4 stress levelThe value of stress at which a series ofduplicate tests are performed. For the purposes of this testmethod, the stress level is reported as the maximum stressapplied to the specimen.3.5 specimen failureThe conditio
11、n at which the specimencompletely breaks or is damaged to such an extent that the loadframe is no longer able to apply the intended stress within therequired limits.4. Summary of Test Method4.1 Uniform cylindrical reduced gage section test specimensare manufactured from acrylic bone cement and mount
12、ed in auniaxial fatigue frame. The specimen is subjected to fullyreversed tensile and compressive loading in a sinusoidal cyclicmanner at a specified frequency in phosphate buffered saline(PBS). The fatigue loading is continued until the specimen failsor a predetermined number of cycles (runout limi
13、t) is reached.5. Significance and Use5.1 This test method describes a uniaxial, constant ampli-tude, fully reversed fatigue test to characterize the fatigueperformance of a uniform cylindrical waisted specimen manu-factured from acrylic bone cement.5.2 This test method considers two approaches to ev
14、aluatingthe fatigue performance of bone cement:1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved April 1, 2009. Published April 2009.
15、Originallyapproved in 2001. Last previous edition approved in 2003 as F2118 03.2For 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 o
16、nthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2.1 Testing is conducted at three stre
17、ss levels to charac-terize the general fatigue behavior of a cement over a range ofstresses. The stress level and resultant cycles to failure of thespecimens are plotted on an S-N diagram.5.2.2 Another approach is to determine the fatigue strengthof a particular cement. The fatigue strength for orth
18、opaedicbone cement is to be determined at 5 million (5 3 106) cycles.The “two-point method” is the specified procedure for con-ducting fatigue testing to determine fatigue strength (1).45.3 This test method does not define or suggest requiredlevels of performance of bone cement. This fatigue test me
19、thodis not intended to represent the clinical use of orthopaedic bonecement, but rather to characterize the material using standardand well-established methods. The user is cautioned to con-sider the appropriateness of this test method in view of thematerial being tested and its potential applicatio
20、n.5.4 It is widely reported that multiple clinical factors affectthe fatigue performance of orthopaedic bone cement; however,the actual mechanisms involved are not well understood.Clinical factors which may affect the performance of bonecement include: temperature and humidity, mixing method,time of
21、 application, surgical technique, bone preparation,implant design, and patient factors, among others. This testmethod does not specifically address these clinical factors. Thetest method can be used to compare different acrylic bonecement formulations and products and different mixing meth-ods and e
22、nvironments (that is, mixing temperature, vacuum,centrifugation, and so forth).6. Apparatus6.1 Uniaxial Load FrameA testing machine capable ofapplying cyclic sinusoidal tensile and compressive loads.6.1.1 The crossheads of the load frame shall be aligned suchthat the alignment meets the requirements
23、 of 8.2 of PracticeE 466. The alignment should be checked at both the maximumtensile and minimum compressive load to be applied during thecourse of a test program.6.2 Cycle CounterA device capable of counting the num-ber of loading cycles applied to a specimen during the courseof a fatigue test.6.3
24、Load CellA load cell capable of measuring dynamictensile and compressive loads in accordance with PracticeE 467.6.4 LimitA device capable of detecting when a testparameter (for example, load magnitude, actuator displace-ment, DC error, and so forth) reaches a limiting value, at whichtime the test is
25、 stopped and the current cycle count recorded.6.5 Environmental ChamberA chamber designed to im-merse the fatigue specimen completely in a solution. Thechamber should have provisions for maintaining a constanttemperature to an accuracy of 62C.7. Test Specimen7.1 Test specimens shall be fabricated fr
26、om cement that isrepresentative of the final product with regard to materials,manufacturing processes, sterilization, and packaging. Steril-ization methods have been shown to have an effect on fatigueperformance. Any deviations of the test cement from theclinically used product must be reported.7.2
27、Cylindrical reduced gage section test specimens with astraight 5-mm diameter by 10-mm-long gage section shall beused. The diameter of the specimen ends shall be substantiallygreater than the gage diameter to ensure that fracture occurs inthe gage section. A smooth radius or taper between thespecimen
28、 ends and gage section is suggested to ensure the gagesection is subjected to a uniform stress field. Suggestedspecimen dimensions are provided in Fig. 1.4The boldface numbers in parentheses refer to a list of references at the end ofthis standard.FIG. 1 Specimen DimensionsF 2118 03 (2009)28. Specim
29、en Preparation8.1 Cement Mixing8.1.1 Store the liquid and powder portions of the cementaccording to the manufacturers instructions before mixing.8.1.2 Allow the mixing equipment to equilibrate to roomtemperature before mixing. Record the room temperature at theonset of mixing.8.1.3 Mix the powder an
30、d liquid components according tothe manufacturers instructions and begin recording the timefrom this point using a stopwatch. Report any deviations fromthe manufacturers storage and mixing recommendations.8.1.4 Report the mixing method and any equipment used.The method used for mixing the cement may
31、 affect its fatiguebehavior. See X1.13 for further information.8.2 Specimen FabricationThe cylindrical reduced gagesection test specimens are fabricated using one of two methods:8.2.1 Direct Molding:8.2.1.1 Insert the mixed cement into a specimen mold(manufactured from silicone, aluminum, TFE-fluoro
32、carbon, orother suitable material) with an internal cavity which has thesame dimensions as the final cement test specimen. Close themold. Record the method of cement insertion into the mold(that is, pour or inject) and method used to close the mold.8.2.1.2 Place the mold in a container of phosphate
33、bufferedsaline (PBS). The PBS solution should be maintained at 37 62C. After the specimens have polymerized for at least 1 h, thespecimens may be removed from the mold. Appendix X2describes a suggested procedure for molding cement speci-mens.8.2.2 Machining:8.2.2.1 Insert the mixed cement into cylin
34、drical mold(manufactured from aluminum, glass, or TFE-fluorocarbontube). The inside diameter of the molding tube should be a fewmillimetres greater than the final specimen grip diameter.8.2.2.2 Maintain the temperature of the mold at at 37 62C. After the specimens have polymerized for at least 1 h,
35、thespecimens may be removed from the mold.8.2.2.3 Machining should not be performed until at least 24h after initial mixing to ensure that the cement is completelypolymerized.8.3 Specimen Examination:8.3.1 Radiographically examine the fabricated specimensfor internal defects. Visually examine specim
36、ens for surfacedefects. Defects in the gage or transition sections (radii) shallbe rejected from testing and discarded. A surface defect isdefined as a surface discontinuity greater than 250 m in majordiameter. In addition, the specimens shall be examined radio-graphically in two orthogonal planes.
37、Specimens with internaldefects greater than 1 mm in major diameter in the gage sectionshall be rejected from testing and discarded. The total numberof specimens rejected divided by the total number of specimensmanufactured (rejection rate) shall be reported. A rationale forthese rejection criteria i
38、s provided in X1.11.NOTE 1The development of fabrication defects may be related to thetendency of a material to develop porosity during polymerization. Theamount of porosity or fabrication defects in the test specimens may be acharacteristic of the cement being evaluated. The rejection rate may give
39、a general indication of a materials tendency toward porosity formation.8.4 Specimen FinishingIf necessary, lightly polish thegage length of the specimens with 600-grit abrasive paper inthe longitudinal direction until the surface is free of machiningand/or mold marks.8.5 Specimen MeasurementMeasure
40、the diameter of thespecimens at a minimum of three places along the gage lengthof each specimen. The average of these measurements shall beused as the specimens gage diameter for calculation of therequired load.8.6 Specimen Conditioning:8.6.1 Place the test specimens in PBS which is maintained ata t
41、emperature of 37 6 2C.8.6.2 Maintain the specimens in the PBS solution for aminimum of 7 days. The cement specimens shall be maintainedin the PBS solution for 7 to 60 days. The specimens shall becontinually immersed in the test solution so that they do not dryout. Distilled water shall be added to t
42、he soaking chamberduring the soaking period to make up for evaporation loss.Each specimen should be soaked up to the time immediatelybefore its being mounted on the load frame. See X1.5 forfurther information.9. Fatigue Test Procedures9.1 Mount the specimens in a test frame test such that auniaxial
43、load is applied. Collets, Jacobs chucks, or pressurizedgrips should be used to firmly grip the specimen at each end.Ensure the longitudinal centerline of the test specimens arealigned with test machine loading axis such that no bendingmoment may be applied to the specimens.9.2 Mount an environmental
44、 chamber on the load frame andfill with fresh test solution immediately after the specimen ismounted to keep the specimen from drying out. The chambershould be filled to a level such that the entire specimen isimmersed. Distilled water shall be added to the test chamberduring the course of a test to
45、 make up for evaporation loss. Thetemperature controller should be programmed and activated toheat the test solution to 37C, and then maintain that tempera-ture within 62C. Fatigue testing should not begin until at least12 h after the solution temperature has reached 37C to ensureequilibration.9.3 P
46、rogram the test frame controller to apply a fullyreversed sinusoidal cyclic waveform at a constant frequency.When testing at frequencies above 2 Hz, the user should verifythat, for the formulation being tested, the chosen frequency hasa negligible effect on the test results. See X1.6 for furtherinfo
47、rmation.9.4 Program the test frame controller to apply the desiredmaximum stress level and a stress ratio of R = 1, indicatingfully reversed loading. A rationale for using fully reversedloading is provided in Appendix X1.10. The load shall becalculated by multiplying the desired stress by the specim
48、enscross-section area, based on each specimens gage diameterdetermined in 8.5.9.4.1 Report the stress level to the nearest 0.5 MPa.9.4.2 When developing an S-N curve, it is recommendedthat testing be conducted at the following maximum stresslevels: 15, 12.5, and 10 MPa. Other stress levels may also
49、beappropriate. See X1.7 for a rationale regarding the selection ofthe recommended stress levels.F 2118 03 (2009)39.4.3 When determining a fatigue strength, the stress levelsshall be chosen in accordance with the “two-point method” (1).9.5 Number of SpecimensWhen developing an S-N curve,a minimum of fifteen specimens shall be tested at each stresslevel. The desired statistical power of the comparison and thevariability to be expected from the cement formulation(s) beinginvestigated should be considered when determining the ap-propriate sample size.
