Determining Fatigue Progression in Corrugated Paperboard Containers Subjected to Dynamic Compression

ABSTRACT

During the transportation phase of the distribution cycle, packaged consignments are subjected to random dynamic compressive loads that arise from random vibrations generated by the vehicle. The protective packaging system's ability to withstand these dynamic compressive loads for sufficiently long periods depends on the environmental vibration levels, the nominal stresses as well as the material's characteristics. The research tests the hypothesis that cumulative damage in the packaging system under random dynamic compression will result in a change in the overall stiffness and damping characteristics of the system as well as in the nature of the statistical distribution of the response. These are manifested, respectively, as a shift in the fundamental resonant frequency of the system as well as an increase in the bandwidth of the frequency response function when subjected to random excitation. The paper presents further results from preliminary experiments in which corrugated paperboard container samples were subjected to dynamic compressive loads by means of broad-band random base excitation with a vibration table coupled with a guided dead-weight arrangement. The level of cumulative damage in the sample was estimated by continuously monitoring the Frequency Response Function (FRF) of the system as well as by observation of thermal distribution images captured at regular intervals. The thermal images were used to establish the sensitivity of the method and to determine whether it can be useful in detecting incipient catastrophic mechanical failure of the packaging system. Results show that thermographic images are useful in identifying regions of elevated temperature in corrugated paper samples and that these regions of high temperature are reliable indicators of the location and mode of structural failure. Results indicate that there appears to be a strong correlation between a reduction in the overall stiffness of the system and variations in the distribution of temperature across the sample.