Issue link: https://cp.revolio.com/i/989729
OBSERVATIONS AABBAA Stacking Pattern After the first two impacts during the mid-test, the unit loads experienced slight deformation to both impacted faces. The top cases on the unit load had the greatest amount of offset due to the shock loading from impact. The last two impacts across the replicates rendered significantly greater offsets than the first two. Figure 13 shows the average offset measurements for the five replicates by Layer as well as average across all Layers. It was observed that the offsets became larger from the bottom to the top Layers and were observed to be significantly higher for the faces along the pallet length in comparison to faces along the pallet width. AAAABB Stacking Pattern After completing the second impact during the mid-test, all unit loads experienced extensive offsets rendering them unsafe to proceed with to the next stage of the testing (Figure 14). Subsequently, further testing was discontinued and the trials were recorded as having failed. Conclusions This study was undertaken to address the present need for establishing test methodologies towards observing a unit load's overall stability during transportation and handling related activities commonly experienced in the distribution environment. ISTA's Load Stability Testing Workgroup supported this study towards exploring relatively low level, short duration shocks using the modified inclined-impact tester as well as determining how well a unit load would stay contained (stable) when experiencing the gravitational forces created by truck acceleration, truck braking and truck turning. Towards addressing this, test methodologies as well as apparatus/measuring tool for tilt and incline impact tests were also developed. Collectively, these provide valuable insight and test procedures towards understanding a unit load's response to shocks and shifts commonly experienced during distribution related activities. With regards to the tilt test, the unit load with the AAAABB stack pattern demonstrated significantly lower stability as compared to the AABBAA configuration. The AAAABB stack pattern also exhibited handling related safety issues due to excessive offsets during the experimentation related activities such as fork lift handling, stretch wrapping, and measurements. Altering the unit load to four or five tiers, stack pattern to ABABAB as well as the stretch wrap material and/or pattern may potentially increase the overall stability of the unit loads. Testing with smaller increments of tilt angles up to 15 is also recommended. As related to the incline impact testing, the unit load with the AABBAA stack pattern demonstrated significant stability and containment of the cases through all five replicate tests. For the AAAABB stack pattern, the four consecutive layers of column stacked cases appeared to be a key factor in the failure of the unit loads. Based on the observations and results of this study, the AAAABB configuration would not be safe to use in a distribution environment where the unit load was likely to experience shocks such as those demonstrated in this research. Testing at various speeds such as 0.40, 0.50, 0.60 and 0.70 mps, towards evaluating the unit load stability, is recommended for future work. The findings of these tests should contribute to potential new methods for International Safe Transit Association's (ISTA) Procedures 3B and 3E testing requirements. Packaging engineers should be able to appropriately develop and/or validate unit loads of packaged goods utilizing the new test methods. 26 ista views • May 2018 • www.ista.org Evaluation of Stability of Unit Loads for Tilt and Shock Events During Distribution > CONTINUED FROM PAGE 25 Figure 13: Incline Impact Total Offset Results for Stacking Pattern AABBAA (cm) Figure 14: Mid-Test Failure After Second Impact for Stack Pattern AAAABB Unit Loads