Wöhler curves (S-N-curves) for flat specimens made from cast iron with lamellar graphit and their application for the FKM-code "Strength assessment". B. Hänel, H. Keding, C. Wirthgen
Wöhlerlinien für Flachproben aus Grauguss - Anwenclung für die FKM-Richtlinie "Festigkeitsnachweis"
Wöhler-curves were determined experimentally for the alternating axial fatigue strength. The tests were carried out on unnotched flat specimens made from cast iron with lamellar graphit. The ultimate tensile strength Rm in of material was 210 MPa. The alternating axial fatigue strength sW depends on the shape of the notch and decreases from 70 MPa for the unnotched specimen (fW = (sW/Rm = 70/210 = 0,33) to 36 MPa for a notched specimen with a stress concentration factor Kt= 4.5. The fatigue notch factor of this specimen is Kf= 70/36 = 1.9, with significant ratio Kt/Kf = 2.4. The endurance at knee point of the Wöhler-curves is approximately equal to ND = 106 cycles, the exponent of slope (double logarithmic scale) is k = 7 for fw = 0.33 or, approximately equivalent, k = 5 for fw = 0.30. The sharpness of the notch does not have a significant influence on these values. The test results should be applicable in the FKM-code "Analytical strength assessment for machine components". At the current time, the value used in this code are - like for stee - fw= 0.30 and k = 5.
Publication Source: Materialprüfung, ISSN: 0025-5300
Issue: 2001-10, pp 387-392
Publisher: Carl Hanser Verlag München