Summary
Matched samples of chipboard were loaded in four-point bending under either a 7 hours loaded/17 hours unloaded cycle, a 17 hours loaded/7 hours unloaded cycle, or constant load in order to asses the effect of cyclic loading on creep deformation. Tests were carried out at three humidity levels (30, 45 and 90% RH) and at three stress levels (30, 45, and 60% of the short term strength). The creep rate of samples under constant load was greater than under cyclic load, with the 7 hours loaded/17 hours unloaded samples giving the lowest creep rate. Analysis of the data on an accumulated time-under-load basis showed that the law of superposition did not apply to the 7 hours loaded/17 hours unloaded samples at the 30% and 45% stress levels, with these samples giving lower deflection than for the other loading conditions. The 17 hours loaded/7 hours unloaded samples also did not appear to obey the law of superposition, although the difference between them and the constantly loaded samples was slight. Considerable scatter in data accumulated at the 60% stress level did not allow any differences in the superposition analysis of cyclic and constant loaded samples to become apparent. Increasing the stress level applied to samples produced an almost linear increase in relative creep for all loading regimes. The 7 hours loaded/17 hours unloaded samples gave consistently lower relative creep values at all levels of stressing, but particularly at the 30 and 45% stress levels. Increasing the relative humidity from 30% to 65% RH had an almost negligible effect on relative creep of all samples, but increasing the humidity to 90% RH caused a marked increase in relative creep.
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References
Bonfield, P. W.; Ansell, M. P. 1991: The fatigue properties of wood in tension, compression and shear. J. Mat. Sci., 26 (17)
Bonfield, P. W.; Ansell, M. P. 1991: Fatigue testing of wood composites for aerogenerator rotor blades. Part VI. Spectrum fatigue loading, life prediction and damage rates. In Wind Energy Conversion 1991, Eds. Garrad, A., Quarton, D. and Fenton, V. Pub. Mechanical Engineering Publications Ltd.
Dinwoodie, J. M.; Paxton, B. H.; Pierce, C. B. 1981: Creep in Chipboard. Part 3: Initial assessment of the influence of moisture content and level of stressing on rate of creep and time to failure. Wood Sci. Technol. 15: 125–144
Dinwoodie, J. M.; Paxton, B. H.; Pierce, C. B. 1984: Creep in Chipboard. Part 4: The influence of temperature and moisture content on the creep behaviour of a range of boards at a single stress level. Wood Sci. Technol. 18: 205–224
Dinwoodie, J. M.; Robson, D. J.; Paxton, B. H.; Higgins, J. 1991: Creep in Chipboard. Part 8: The effect of steady-state moisture content, temperature and level of stressing on the relative creep behaviour and creep modulus of a range of boards. Wood Sci. Technol. 26: 225–238
Dinwoodie, J. M.; Higgins, J.; Paxton, B. H.; Robson, D. J. 1992: Creep in Chipboard. Part 11: The effect of cyclic changes in moisture content and temperature on the creep behaviour of a range of boards at different levels of stressing. Wood Sci. Technol. 26: 429–448
Gressel, P. 1984: Kriechverhalten von Holtz und Holzwerkstoffen-Auswirkungen auf den Formänderungsnachweis. Ingenierholzbau in Forschung und Praxis, Bruderverlag, Karlsruhe
Grossman, P. U. A.; Nakai, T. 1987: Deflection of wood under intermittent loading. Part 2: Cycles of two days and of 14 minutes. Wood Sci. Technol 21: 349–360
Hacker, C. L.; Ansell, M. P.; Bonfield, P. W. 1992: High Frequency Loading of Chipboard. Final Report, Bath University, February
Nakai, T.; Grossman, P. U. A. 1983: Deflection of wood under intermittent loading, Part 1. Fortnightly cycles. Wood Sci. Technol. 17: 55–67
Pierce, C. B.: Dinwoodie, J. M.; Paxton, B. H. 1979: Creep of Chipboard. Part 2: The use of fitted response curves for comparative and predictive purposes. Wood Sci. Technol. 13: 265–282
Pierce, C. B.; Dinwoodie, J. M.; Paxton, B. H. 1985: Creep of Chipboard. Part 5: An improved model for creep prediction. Wood Sci. Technol. 19: 83–91
Sekino, N.; Okuma, M. 1985: Performance over time of construction particleboard I. Fatigue behaviour in bending. Mokuzai Gakkaishi, 30 (10): 801–806
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Dinwoodie, J.M., Paxton, B.H., Bonfield, P.W. et al. Fatigue and creep in chipboard. Wood Sci.Technol. 29, 64–76 (1995). https://doi.org/10.1007/BF00196932
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DOI: https://doi.org/10.1007/BF00196932