ASTM F2118-14(R2020) pdf free download
ASTM F2118-14(R2020) pdf free download.Standard Test Method for Constant Amplitude of Force Controlled Fatigue Testing of Acrylic Bone Cement Materials
5. Significance and Use
5.1 This test method describes a uniaxial, constant amplitude, fully reversed fatigue test to characterize the fatigue performance of a uniform cylindrical waisted specimen manu- factured from acrylic bone cement. 5.2 This test method considers two approaches to evaluating the 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 of stresses. The stress level and resultant cycles to failure of the specimens can be plotted on an S-N diagram. 5.2.2 Another approach is to determine the fatigue life of a particular cement. The fatigue life for orthopaedic bone cement is to be determined up to 5 million (5 × 10 6 ) cycles. 5.3 This test method does not define or suggest required levels ofperformance ofbone cement. This fatigue test method is not intended to represent the clinical use oforthopaedic bone cement, but rather to characterize the material using standard and well-established methods. The user is cautioned to con- sider the appropriateness of this test method in view of the material being tested and its potential application. 5.4 It is widely reported that multiple clinical factors affect the fatigue performance of orthopaedic bone cement; however, the actual mechanisms involves multiple factors. Clinical factors which may affect the performance of bone cement include: temperature and humidity, mixing method, time of application, surgical technique, bone preparation, implant design, anatomical site, and patient factors, among others. This test method does not specifically address all of these clinical factors. The test method can be used to compare different acrylic bone cement formulations and products and different mixing methods and environments (that is, mixing temperature, vacuum, centrifugation, and so forth).
6. Apparatus
6.1 Uniaxial Load Frame—A testing machine capable of applying cyclic sinusoidal tensile and compressive loads. 6.1.1 The crossheads ofthe load frame shall be aligned such that the alignment meets the requirements of section 8.2 of Practice E466. The alignment should be checked at both the maximum tensile and minimum compressive load to be applied during the course of a test program. 6.2 Cycle Counter—A device capable of counting the num- ber of loading cycles applied to a specimen during the course of a fatigue test. 6.3 Load Cell—A load cell capable of measuring dynamic tensile and compressive loads in accordance with Practice E467. 6.4 Limit—A device capable of detecting when a test pa- rameter (for example, load magnitude, actuator displacement, direct current (DC) error, and so forth) reaches a limiting value, at which time the test is stopped and the current cycle count recorded. 6.5 Environmental Chamber—A chamber designed to im- merse the fatigue specimen completely in a solution. The chamber should have provisions for maintaining a constant temperature to an accuracy of 62°C.
7. Test Specimen
7.1 Test specimens shall be fabricated from cement that is representative of the final product with regard to materials, manufacturing processes, sterilization, and packaging. Certain sterilization methods (for example, gamma sterilization of the powder) have been shown to have an effect on fatigue performance. Any deviations of the test cement from the clinically used product must be reported. 7.2 Cylindrical reduced gage section test specimens with a straight 5-mm diameter by 10-mm-long gage section shall be used. The diameter of the specimen ends shall be substantially greater than the gage diameter to ensure that fracture occurs in the gage section. A smooth surface of the test specimen in the radius or taper between the specimen ends and gage section is essential to reduce variation in reported fatigue life. Suggested specimen dimensions are provided in Fig. 1.
