Fatigue of structural plywood under cyclic shear through thickness I: fatigue process and failure criterion based on strain energy |
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Authors: | Takanori Sugimoto Yasutoshi Sasaki Mariko Yamasaki |
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Institution: | (1) Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan;(2) Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan |
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Abstract: | The fatigue behavior of plywood specimens under shear through thickness was examined on the basis of strain energy to obtain
common empirical equations for the fatigue process and failure criterion under various loading conditions. Specimens were
cut from commercial plywood panels of 9-mm thickness. Loading conditions were set as follows: a square waveform at a loading
frequency of 0.5 Hz, a triangular waveform at 0.5 Hz, and a triangular waveform at 5.0 Hz. Peak stress applied was determined
to be 0.5, 0.7, and 0.9 of static strength, that is, stress levels of 0.5, 0.7, and 0.9. The stress-strain relationships were
measured throughout the fatigue test, and the strain energy was obtained at each loading cycle. Loading conditions apparently
affected the relationship between stress level and fatigue life. On the other hand, the relationship between mean strain energy
per cycle and fatigue life was found to be independent of loading conditions. Mean strain energy per cycle obtained as the
fatigue limit was 5.85 kJ/m3 per cycle. Assuming that the accumulation of strain energy is a fatigue indicator, the fatigue process and failure criterion
for the plywood specimens under the three loading conditions were commonly expressed by the relationship between cumulative
strain energy and loading cycles. |
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Keywords: | Loading waveform Loading frequency Strain energy Shear through thickness Plywood |
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