Vibration of Fresh Fruits and Vegetables
During Refrigerated Truck Transport
Summary:
In transportation tests with fresh fruits and vegetables, refrigerated trailers equipped with steel - spring suspension systems had highest Power Spectral Density levels at about 3.5 Hz. Other frequencies with high PSD levels were 9, 18, and 25. However, in trailers equipped with an air-ride suspension system, the PSD levels were attenuated at 3.5 Hz and reduced at other frequencies. The highest PSD levels were found at the rear of the trailer, with resonance occurring in the loaded boxes at some frequencies.
Horizontal acceleration was much less than the vertical acceleration. The results may show the less damaging suspension type of produce transport, how to improve either suspension type, or what packaging systems should be designed.
Abstract:
Fresh fruits and vegetables experience losses in the marketplace that are caused by mechanical injuries. Past studies have indicated that transit vibration contributes to this loss, and may be more important than impacts as a source of damage. In cross-country tests of cherries, nectarines, and pears in semi-trailers equipped with steel-spring suspension systems, highest Power Spectral Density (PSD) levels were found at about 3.5 Hz.
In this study, PSD is used to mean acceleration spectral density. Other frequencies with high PSD levels were 9, 18, and 25 Hz. Similar results were found in tests with fresh tomatoes. However, in trailers equipped with an air-ride suspension and loaded with tomatoes, the PSD levels were attenuated at 3.5 Hz., and were reduced at other frequencies. The highest PSD levels were found at the rear of the trailer, with resonance in the loaded boxes occurring at some frequencies. Horizontal acceleration was much less than the vertical acceleration.
Understanding acceleration levels and frequencies that occur during shipment of perishables in refrigerated trailers will help to determine methods that will dampen the vibration energy and reduce the present losses in produce quality.
Introduction:
Fresh fruits and vegetables are subjected to injuries during handling, transportation, and distribution. Cherries, tomatoes, nectarines, and Bartlett pears have demonstrated these losses, ranging from 15 to 68% of their total market losses (Ceponis and Butterfield, 1974, 1981, 1985; and Ceponis and Cappellini, 1985). "The basis for management of quality is the prediction of damage resulting from the susceptibility of the produce to the hazards of distribution" (Schoorl and Holt,1982).
O'Brien et al. (1963) also stated that "Two factors affect the bruising of fruits: the magnitude of the force and number of times this force is repeated at a given location". It has been suggested, however, that vibration may cause more bruising than impacts (Goff and Twede, 1979). Apple bruising was influenced by the quality of the road, shipment distance, and the type of container in which they were packed (Shulte-Pason et al., 1989).
Reducing vibration and rubbing of peaches during transport from the orchard to the packing house reduced surface discoloration (Phillips, 1988). Laboratory tests have shown that table grapes positioned on the top layer of the stack sustained more damage than when they were in the bottom layer. The damage was a result of acceleration levels in the top layer being twice that of the lower ones (Fisher et al., 1989).
The objectives of our study were to: 1) determine the acceleration frequencies and relative amplitudes occurring in loads of fresh fruits and vegetables during commercial cross-country tests in refrigerated trailers with commonly-used steel-spring suspension systems; and 2) compare the vibration levels of refrigerated trailers equipped with steel-spring suspensions or air-ride suspensions.
Vibration of Fresh Fruits and Vegetables
During Refrigerated Truck Transport
Summary:
In transportation tests with fresh fruits and vegetables, refrigerated trailers equipped with steel - spring suspension systems had highest Power Spectral Density levels at about 3.5 Hz. Other frequencies with high PSD levels were 9, 18, and 25. However, in trailers equipped with an air-ride suspension system, the PSD levels were attenuated at 3.5 Hz and reduced at other frequencies. The highest PSD levels were found at the rear of the trailer, with resonance occurring in the loaded boxes at some frequencies.
Horizontal acceleration was much less than the vertical acceleration. The results may show the less damaging suspension type of produce transport, how to improve either suspension type, or what packaging systems should be designed.
Abstract:
Fresh fruits and vegetables experience losses in the marketplace that are caused by mechanical injuries. Past studies have indicated that transit vibration contributes to this loss, and may be more important than impacts as a source of damage. In cross-country tests of cherries, nectarines, and pears in semi-trailers equipped with steel-spring suspension systems, highest Power Spectral Density (PSD) levels were found at about 3.5 Hz.
In this study, PSD is used to mean acceleration spectral density. Other frequencies with high PSD levels were 9, 18, and 25 Hz. Similar results were found in tests with fresh tomatoes. However, in trailers equipped with an air-ride suspension and loaded with tomatoes, the PSD levels were attenuated at 3.5 Hz., and were reduced at other frequencies. The highest PSD levels were found at the rear of the trailer, with resonance in the loaded boxes occurring at some frequencies. Horizontal acceleration was much less than the vertical acceleration.
Understanding acceleration levels and frequencies that occur during shipment of perishables in refrigerated trailers will help to determine methods that will dampen the vibration energy and reduce the present losses in produce quality.
Introduction:
Fresh fruits and vegetables are subjected to injuries during handling, transportation, and distribution. Cherries, tomatoes, nectarines, and Bartlett pears have demonstrated these losses, ranging from 15 to 68% of their total market losses (Ceponis and Butterfield, 1974, 1981, 1985; and Ceponis and Cappellini, 1985). "The basis for management of quality is the prediction of damage resulting from the susceptibility of the produce to the hazards of distribution" (Schoorl and Holt,1982).
O'Brien et al. (1963) also stated that "Two factors affect the bruising of fruits: the magnitude of the force and number of times this force is repeated at a given location". It has been suggested, however, that vibration may cause more bruising than impacts (Goff and Twede, 1979). Apple bruising was influenced by the quality of the road, shipment distance, and the type of container in which they were packed (Shulte-Pason et al., 1989).
Reducing vibration and rubbing of peaches during transport from the orchard to the packing house reduced surface discoloration (Phillips, 1988). Laboratory tests have shown that table grapes positioned on the top layer of the stack sustained more damage than when they were in the bottom layer. The damage was a result of acceleration levels in the top layer being twice that of the lower ones (Fisher et al., 1989).
The objectives of our study were to: 1) determine the acceleration frequencies and relative amplitudes occurring in loads of fresh fruits and vegetables during commercial cross-country tests in refrigerated trailers with commonly-used steel-spring suspension systems; and 2) compare the vibration levels of refrigerated trailers equipped with steel-spring suspensions or air-ride suspensions.