1、Designation: F2118 10Standard Test Method forConstant Amplitude of Force Controlled Fatigue Testing ofAcrylic Bone Cement Materials1This standard is issued under the fixed designation F2118; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, 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 amplitude, uniaxial, tensi
3、on-compression uni-form fatigue performance of acrylic bone cement materials.1.2 This test method is relevant to orthopedic bone cementsbased on acrylic resins, as specified in Specification F451 andISO 16402. The procedures in this test method may or may notapply to other surgical cement materials.
4、1.3 It is not the intention of this test method to define levelsof performance of these materials. It is not the intention of thistest method to directly simulate the clinical use of thesematerials, but rather to allow for comparison between acrylicbone cements to evaluate fatigue behavior under spe
5、cifiedconditions.1.4 A rationale is given in Appendix X2.1.5 The values stated in SI units are to 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, if any, associated with its use. It is theresp
6、onsibility 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:2E466 Practice for Conducting Force Controlled ConstantAmplitude Axial Fatigue Tests of Meta
7、llic MaterialsE467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing SystemE1823 Terminology Relating to Fatigue and Fracture Test-ingF451 Specification for Acrylic Bone Cement2.2 ISO Standard:ISO 16402 Flexural Fatigue Testing of Acrylic Resin Ce-ments Used
8、 in Orthopedics33. Terminology3.1 Unless otherwise given, the definitions for fatigue ter-minology given in Terminology E1823 will be used.3.1.1 mean fatigue life at N cyclesthe average number ofcycles to failure at the specified load level. For the purposes ofthis test method, the fatigue life will
9、 be determined at 5 millionload cycles. A rationale for this is provided in X2.4.3.1.2 median fatigue life at a given stress levelthe numberof cycles to failure at which 50 % of the tested samples failedat the specified stress level.3.1.3 runouta predetermined number of cycles at whichthe testing on
10、 a particular specimen will be stopped, and nofurther testing on that specimen will be performed. For thepurposes of this test method, the runout will be 5 million loadcycles.3.1.4 specimen failurethe condition at which the speci-men completely breaks or is damaged to such an extent that theload fra
11、me is no longer able to apply the intended stress withinthe required limits.3.1.5 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.4. Summary of Test Metho
12、d4.1 Uniform cylindrical reduced gage section test specimensare manufactured from acrylic bone cement and mounted 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(
13、PBS). The fatigue loading is continued until the specimen failsor a predetermined number of cycles (run-out limit) is reached.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 Mater
14、ial Test Methods.Current edition approved Dec. 1, 2010. Published January 2011. Originallyapproved in 2001. Last previous edition approved in 2009 as F 2118 03 (2009).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual
15、Book of ASTMStandards volume information, refer to the standards Document Summary page onthe 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,
16、West Conshohocken, PA 19428-2959, United States.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 met
17、hod considers two approaches to evaluatingthe fatigue performance of bone cement:5.2.1 Testing is conducted at three stress 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 can plotted on an S-N
18、 diagram.5.2.2 Another approach is to determine the fatigue life of aparticular cement. The fatigue life for orthopaedic bone cementis to be determined up to 5 million (5 3 106) cycles.5.3 This test method does not define or suggest requiredlevels of performance of bone cement. This fatigue test met
19、hodis 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 application
20、.5.4 It is widely reported that multiple clinical factors affectthe fatigue performance of orthopaedic bone cement; however,the actual mechanisms involves multiple factors. Clinicalfactors which may affect the performance of bone cementinclude: temperature and humidity, mixing method, time ofapplica
21、tion, surgical technique, bone preparation, implant de-sign, anatomical site, and patient factors, among others. Thistest method does not specifically address all of these clinicalfactors. The test method can be used to compare differentacrylic bone cement formulations and products and differentmixi
22、ng methods and environments (that is, mixing tempera-ture, 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 meet
23、s the requirements of section 8.2 ofPractice E466. The alignment should be checked at both themaximum tensile and minimum compressive load to be appliedduring the course of a test program.6.2 Cycle CounterA device capable of counting the num-ber of loading cycles applied to a specimen during the cou
24、rseof a fatigue test.6.3 Load CellA load cell capable of measuring dynamictensile and compressive loads in accordance with PracticeE467.6.4 LimitA device capable of detecting when a testparameter (for example, load magnitude, actuator displace-ment, DC error, and so forth) reaches a limiting value,
25、at whichtime the test is 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 specimen
26、s shall be fabricated from cement that isrepresentative of the final product with regard to materials,manufacturing processes, sterilization, and packaging. Certainsterilization methods have been shown to have an effect onfatigue performance (for example, gamma sterilization of thepowder). Any devia
27、tions of the test cement from the clinicallyused product must be reported.7.2 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 fr
28、acture occurs inthe gage section. A smooth surface of the test specimen in theradius or taper between the specimen ends and gage section isessential to reduce variation in reported fatigue life. Suggestedspecimen dimensions are provided in Fig. 1.FIG. 1 Specimen DimensionsF2118 1028. Specimen Prepar
29、ation8.1 Cement Mixing:8.1.1 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 and liquid
30、 components according tothe manufacturers instructions and begin recording the timeusing a stopwatch when the liquid and powder are initiallymixed. Report any deviations from the manufacturers storageand mixing recommendations.8.1.4 Report the mixing method and any equipment used.The method used for
31、 mixing the cement may affect its fatiguebehavior. See X2.13 for further information.8.2 Specimen FabricationThe cylindrical reduced gagesection test specimens are fabricated using the followingmethod:8.2.1 Direct Molding:8.2.1.1 Inject the mixed cement into a specimen moldduring the dough phase as
32、determined by Specification F451(manufactured from silicone material, see Appendix X3 (sug-gested specimen molding method) with an internal cavitywhich has the same dimensions as the final cement testspecimen. Record the method of cement insertion into the mold(that is, syringe injected). A 150 mL s
33、yringe with an innerdiameter of 38 mm and a nozzle tip diameter of 10 mm shouldbe considered for use. The mold should be placed on a flatsurface. The cement injection should be performed from top tobottom in direction allowing the cement to flow down axiallyto the bottom . The bottom of the mold is
34、placed on a flatsurface as the bone cement is being injected into the moldunixaially from the top down. If air is entrapped and leads toresistance to injection, the mold should be rocked back andforth to release trapped air from the bottom of the mold. Thiswill allow for air to escape from the botto
35、m of the mold. (SeeX3.6 for standard operating procedure for making bone cementspecimens.)8.2.1.2 Place the mold in a container of phosphate bufferedsaline (PBS). The PBS solution should be maintained at 37 62C. After at least1hinthePBSbath, the specimens may beremoved from the mold. Appendix X3 des
36、cribes a suggestedprocedure for molding cement specimens.8.3 Specimen Examination:8.3.1 Visually examine specimens for surface defects. Sur-face defects in the gage or transition sections (radii) shall berejected from testing and discarded. A surface defect is definedas a surface discontinuity great
37、er than 250 mm in majordiameter. All specimens should be photographed to documentsurface finish prior to testing. In addition, the specimensstraightness should be compared to the metal positive blank toensure that the specimen is will not product bending momentsduring the unaxial fatigue testing. St
38、raightness can be assessedby rolling the specimens and determining if there is a visiblewobble as compared to the straight metallic blank used to makethe mold. Specimens with surface defects or deemed not to bestraight shall be rejected from testing and discarded. The totalnumber of specimens reject
39、ed divided by the total number ofspecimens manufactured (rejection rate) shall be reported. Arationale for these rejection criteria is provided in X2.11.8.4 Specimen FinishingIf necessary, lightly polish thegage length of the specimens with 600-grit abrasive paper inthe longitudinal direction until
40、the surface is free of machiningand/or mold marks.8.5 Specimen MeasurementMeasure 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 Spe
41、cimen Conditioning:8.6.1 Place the test specimens in PBS which is maintained ata temperature 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
42、 the test solution so that they do not dryout. Distilled water shall be added to the 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 X2.5 forfurther information.9. Fatigu
43、e Test Procedures9.1 Mount one specimen at a time in a test frame test suchthat a uniaxial load is applied. Collets, Jacobs chucks, orpressurized grips should be used to firmly grip the specimen ateach end. Ensure the longitudinal centerline of the test speci-men is aligned with test machine loading
44、 axis such thatbending moments are minimized. Testing of multiple speci-mens on the same fixture in parallel or series shall not beperformed as this complicated and changes the stress state inthe individual specimens when cracks initiate and propagatethrough the specimen occurs, effectively changing
45、 the modulusof each individual specimen being tested.9.2 Mount an environmental chamber on the load frame andfill with fresh PBS 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. Di
46、stilled water shall be added to the test chamberduring the course of a test to make up for any evaporation loss.The temperature controller should be programmed and acti-vated to heat the test solution to 37C, and then maintain thattemperature within 62C. Fatigue testing should not beginuntil at leas
47、t12 h after the solution temperature has reached37C to ensure equilibration.9.3 Program the test frame controller to apply a fullyreversed sinusoidal cyclic waveform at a constant frequency.When testing at frequencies above 5 Hz, the user should verifythat, for the formulation being tested, the chos
48、en frequency hasa negligible effect on the test results. See X2.6 for furtherinformation.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 X2.10. The
49、 load shall be calculated byF2118 103multiplying the desired stress by the specimens cross-sectionarea, based on each specimens gage diameter as determined in8.5.9.4.1 Report the stress level to the nearest 0.5 MPa.9.4.2 When developing an S-N curve (see 10.1), it isrecommended that testing be conducted at the followingmaximum stress levels: 15, 12.5, and 10 MPa. Other stresslevels may also be appropriate for orthopedic applications suchthe hip and knee. However, stress levels of 5, 7, and 9 MPashould be considered for spinal applications in vertebro
