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- Title
Cumulative nonlinearity as a parameter to quantify mechanical fatigue.
- Authors
Hirschberg, Valerian; Wilhelm, Manfred; Rodrigue, Denis
- Abstract
The cumulative nonlinearity (Qf) is proposed as a new parameter to quantify mechanical fatigue. The parameter Qf represents the (cycle number) integral of the ratio of the third harmonic to the fundamental one (I3/1), obtained via Fourier transform of the stress (torque), normalized by the square of the strain amplitude (γ0). The validation is performed on different polymers: polystyrene (PS) with different molecular weights, styrene‐acrylonitrile (SAN), polymethylmethacrylate (PMMA), and polytertbuthylmethacrylate (PtBMA) under strain controlled fatigue tests in a torsion rectangular set‐up. A power‐law correlation between the number of cycles to failure (Nf) and the cumulative nonlinearity was found for Nf > 1000 cycles, and the results were compared with well‐established failure criteria such as the cumulative stress and the dissipated energy density. It was found that the cumulative nonlinearity has superior prediction ability since it can quantify material changes during a test.
- Subjects
MATERIAL fatigue; MOLECULAR weights; ENERGY density; POLYMETHYLMETHACRYLATE; FOURIER transforms; ACRYLONITRILE butadiene styrene resins
- Publication
Fatigue & Fracture of Engineering Materials & Structures, 2020, Vol 43, Issue 2, p265
- ISSN
8756-758X
- Publication type
Article
- DOI
10.1111/ffe.13120