Simulation of Vibration Damage in Produce Transportation

MODUS operandi of measuring, recording and synthesizing transportation vibration environments for produce damage simulation in the laboratory is described. Based on measurements of typical produce transport routes, realistic simulation of damage in containers and unit loads of fresh produce may be achieved in a fraction of the real journey's time, by reproducing maxi-max envelope peak acceleration spectra. A semi open loop control strategy, for an electrohydraulic vibration testing machine was developed, utilizing commonly available and relatively inexpensive analog instrumentation and components, while digital hardware and software is implemented on a microcomputer. Once a control signal, simulating a given transport environment is developed, for a particular brand and type of vibration machine, it can be stored on FM analog magnetic cassette tape. Copies of this tape may be played back, as command signals on similar machines, for simulating that environment, hence further reducing cost and complexity. Simulation experiments are reported, wherein columns of containers filled with dummy fruit and oranges, were subjected to a typical maxi-max acceleration envelope spectrum. These show, that the highest acceleration levels are encountered in the bottom tier containers, whether the load is strapped down or not. The low frequency end of the spectrum is significantly amplified in the top tier containers, when the column is strapped down. The high frequency end of the spectrum is generally attenuated from the bottom to the top tier containers.