Date of Award

12-2025

Degree Name

Master of Science in Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Daniel Kujawski Ph.D.

Second Advisor

Muralidhar K Ghantasala Ph.D.

Third Advisor

Javier M Montefort-Sanchez Ph.D.

Keywords

1/Nf, 17-4PH, fatigue, medical, stainless steel, staircase

Access Setting

Masters Thesis-Open Access

Abstract

This study compares two methods for estimating the fatigue limit of 17-4 PH stainless steel (H900): the Dixon–Mood staircase and Kujawski 1/Nf linear method. Tests were conducted on an MTS Acumen 3 kN system under axial tension–tension loading at R = 0.1 and 50 Hz, following the standard practice defined in ASTM E466-15. Flat specimens were fabricated by water-jet cutting and polished. Tensile tests verified mechanical properties consistent with published data for the H900 condition. Fifteen specimens tested by the staircase method yielded a mean fatigue limit of 1138 MPa. The 1/Nf analysis using four specimens produced 1159 MPa, 2 % higher than the staircase result. When seven failures from the staircase tests were added, the predicted limit became 1140 MPa, only 0.2 % higher. All results were within the MMPDS (R = 0.1) range of about 1100 MPa for 17-4 PH H900. The findings show that the Kujawski 1/Nf method reproduces the statistically derived endurance limit while requiring fewer specimens and less test time, offering an efficient approach for fatigue-limit determination in engineering materials and medical-device applications.

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