Testing of corrugated box components for compressive creep strength in the variable humidity environment of a given coolstore could be expected to depend on reproducing in the laboratory exactly the humidity changes found within the coolstore. These variations are typically complex and sometimes random. Results obtained from testing using the coolstore as the test environment can be extremely variable as a result. The work reported in this paper, shows that various cycles of humidity can be described by their humidity impulse -the area under a humidity/time curve - and that the effect reaches a maximum with increasing severity of impulse. The consequences of this are that any coolstore can be represented (in its effect on creep strength) by testing in a worst-case defined laboratory humidity regime. Such a regime substitutes the variability of the coolstore for a controlled and reproducible cyclic pattern using an environmental cabinet and will still produce the same "worst-case" result, but with significantly less variability. Detailed comment and comparison of the Ensis Papro hyperbolic creep model and the safety factor model employed by others is made in the paper to aid in the understanding of creep measurement and response.
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