BS ISO 1143:2021 pdf download – Metallic materials — Rotating bar bending fatigue testing
Experience has shown that a ratio of at least 2:1 between the cross-sectional areas of the gripping regions and the test portion of the specimen is recommended. The grips which do not lead up to large stress-concentration area are recommended. In tests on certain materials, a combination of high stress and high speed may cause excessive hysteresis heating of the specimen. This effect may be reduced by subjecting a smaller volume of the material or by decreasing the test frequency (see 10.3). If the specimen is cooled, the test medium should be reported.
6.2 Dimensions of specimens All the specimens employed in a test series for a fatigue-life determination shall have the same size, shape and tolerance of diameter. For the purpose of calculating the force to be applied to obtain the required stress, the actual minimum diameter of each specimen shall be measured to an accuracy of 0,01 mm. Care shall be taken during the measurement of the specimen prior to testing to ensure that the surface is not damaged. On cylindrical specimens subject to constant bending moment (see Figures 4 and 5), the parallel test section shall be parallel within 0,025 mm. For other forms of cylindrical specimen (see Figure 1), the parallel test section shall be parallel within 0,05 mm. For material property determination, the transition fillets at the ends of the test section should have a radius not less than 3d. For hourglass-type specimens, the section formed by the continuous radius should have a radius not less than 5d. Figure 8 shows the shape and dimensions of a typical cylindrical specimen. The recommended values of d are 6 mm, 7,5 mm and 9,5 mm. The tolerance of diameter should be 0,005d. Figure 9 shows a typical hourglass specimen suitable for fatigue testing at elevated temperature.
7 Preparation of specimens
7.1 General In any rotating bar bending fatigue test program designed to characterize the intrinsic properties of a material, it is important to observe the following recommendations in the preparation of specimens. A possible reason for deviation from these recommendations is if the test program aims to determine the influence of a specific factor (surface treatment, oxidation, etc.) that is incompatible with the recommendations. In all cases, any deviation shall be noted in the test report.
7.2 Selection of the specimen and marking The sampling of test materials from a semi-finished product or a component may have a major influence on the results obtained during the test. It is therefore necessary for this sampling to be recorded and a sampling drawing be prepared. This shall form part of the test report and shall indicate clearly
— the position of each of the specimens removed from the semi-finished product or component,
— the characteristic directions in which the semi-finished product has been worked (direction of rolling, extrusion, etc., as appropriate), and
— the unique identification of each of the specimens.
The unique mark or identification of each specimen shall be maintained at each stage of its preparation. This may be applied using any reliable method in an area not likely to disappear during machining or likely to adversely affect the quality of the test. Upon completion of the machining process, it is desirable for both ends of each specimen to be uniquely marked so that, after failure of a specimen, each half can still be identified.
7.3 Machining procedure
7.3.1 Heat treatment of test material The heat treatment is generally performed on a rough machined specimen. Then final machining followed by polishing should be performed on the specimen to remove any deformation of the specimen due to the heat treatment process. If that is not possible, the heat treatment should be carried out in a vacuum or in inert gas to prevent oxidation of the specimen. Subsequent stress relieving is recommended in this case. The stress relieving treatment shall not alter the micro-structural characteristic of the material under study. The specifics of the heat treatment and machining procedure shall be reported with the test results.BS ISO 1143 pdf download.