We might think that the best way to simulate a transportation process with the purpose of getting to know how our cargo behaves is to put our cargo on a truck and drive tens, hundreds or thousands of kilometres with it.
However, this technique only allows us to analyze the behaviour of our load for that specific route, at that specific moment, with that specific truck and with that specific driver. Too specific, right?
This method does not let us predict the real behaviour for different packaging alternatives, means of transportation or routes, as one would in a laboratory testing. This is because it does not allow for repeatability, which is necessary to be able to predict the real behaviour of different packaging options.
Another widespread idea is that of recording a specific route a single time, and then reproducing it second-by-second in a laboratory testing, for example in vibration test systems. This alternative does allow for repeatability that we would not obtain using the previous solution. However, we still have the same problem regarding the fact that only a specific route at a specific moment is being reproduced, for a specific driver and truck.
The solution to the repeatability problem is, therefore, the vibration tester – a system that allows for the reproduction of vertical vibrations and angular motions generated during transportation in a laboratory testing, at least when using our patented Vertical Vibration + Pitch & Roll system.
Power Spectral Density (PSD)
Reproducing those vertical vibrations and pitch & roll motions, and eliminating the problem of reproducing a single route under the same conditions time and again, requires the use of what is known as PSD.
Power Spectral Density (PSD) is the energy variation within a vibrating signal, measured as frequency per unit of mass. In the packaging industry, Power Spectral Density analysis is used to measure how vibrations can affect goods.
Once data is obtained for a certain route using a data recorder such as innRecord, which allows us to record all the vibrations and angular motions during transportation, we can obtain the PSD for that trip. This PSD is simply our signal transformed from the time domain to the frequency domain; it indicates the different levels of intensity for each of the frequencies that are present in the vibrations transferred by a transport.
When we introduce these PSDs into a vibration table, it combines these different intensities and frequencies in order to generate a random vibration with normalized deviations. This allows us to statistically simulate what usually takes place in the recorded route at the laboratory testing with the purpose of reproducing statistically verifiable trips for the recorded and analyzed trip. In other words, thanks to this PSD, you will not only reproduce that specific moment, but other signals are generated that can also statistically take place for that route by increasing or decreasing the intensity of the vibration across different frequencies.
Using this, we can predict what can actually be experienced by our load during transportation under the specified conditions.
What happens if you don’t have a specific route for optimizing your package?
For that, there are international standards that are widely used around the world, such as ASTM, ISO, EN and ISTA procedures, which offer us a ready-made calculation, providing us with the PSDs mentioned above so that we can enter them directly into the innWave vibration machine of our laboratory testing.
For example, these are some of the ISTA procedures that use vibration systems:
- Vertical vibration machine: Procedure 1A, Procedure 1B, Procedure 1C, Procedure 1D, Procedure 1E, Procedure 1G, Procedure 1H, Procedure 2A, Procedure 2B, Procedure 2C, Procedure 3A, Procedure 3B, Procedure 3E, Procedure 3F, Procedure 3H, Project 3K, ISTA 4 Series, 6-FEDEX-A, 6-FEDEX-B, Project 6-AMAZON.COM-SIOC, Project 6-AMAZON.COM-Over Boxing and Project 6-SAMSCLUB.
- Vertical + Pitch & Roll machine: Procedure 3A and ISTA 4 Series.
Keep learning about ASTM with this post: ASTM standards for goods transportation
With other regulations, in order for vibration tests to be compliant, a series of established guidelines must be followed, such as UNE-EN ISO 2247:2000 or EN 15552: 2008.
Advantages of the vibration tables by Safe Load TT
Safe Load TT’s innWave product family offers a great variety of solutions to optimize not only your packaging, but also all products that are exposed to vibrations.
Our systems are tailored to the needs of the client and also have an intuitive control system developed by vibration experts of Victoria University of Melbourne, Australia, which makes innWave products the best packaging vibration simulation solution.
Keep reading: Safe Load TT vibration table: how does it work?
Would you like to know which the best vibration tester for your laboratory testing is? Get in touch with us and we will advise you so that you can find the right transport simulation equipment for you.