Understanding how shock and vibration can damage high-value assets in transit is a common problem in the world of shipping and transportation.
I recently had the pleasure of attending the “Towards Art in Transit 2.0” symposium at the 2024 AIC annual meeting, where engineers and art conservators discussed these issues and their impact on the art community.
This symposium focused on the methodology of shipping and transporting works of art to ensure their protection from damage. Hearing the leaders of this community speak with strong knowledge and passion about protecting assets that have high monetary value and significant cultural and educational importance was both educational and inspiring. While this symposium specifically addressed how we can protect works of art, the principles discussed can apply to shipping almost anything.
Topics covered include:
A strong theme throughout the symposium was the desire to reduce the industry’s carbon footprint and find more sustainable ways to transport works of art. However, there was also a sense of trepidation about these green transportation materials and methods being as effective as the methods they are replacing. This brings us to an important question:
What data should we look at to evaluate the safety of the assets being transported so we can confidently transport these important cultural artifacts?
The first speakers of the day, Dale Kronkright (Georgia O' Keeffee Musuem), and Bob White, set out to answer that question by giving us an overview of what vibration is and why it is important to understand - in order to protect high-value assets, such as art. We have covered much of this same territory in our past blog (What Happens to Your Package During Shipment), but their presentation highlighted a few points worth reiterating.
It's crucial to remember that vibration consists of both amplitude, the amount of movement, and frequency, how often the vibrations occur. Both measurements are crucial for understanding the true vibration environment. This is because the potential damage caused by vibration can be calculated by considering the interaction between amplitude, frequency, and other factors such as material fatigue and resonant frequencies. When examining damage in this way, it becomes clear that:
low amplitude but high frequency vibration can be just as destructive as high amplitude but low frequency vibration.
We want to minimize both the amplitude and frequency of our vibration, but there is one other factor that we need to consider: the natural frequency of the object. If the object is subjected to white noise vibration, meaning vibration that is the same amplitude at all frequencies, the object will inherently experience a higher amplitude vibration at its natural frequency. Frequencies lower than this natural frequency may not cause significant resonance, while frequencies higher than the natural frequency will result in lower amplitude due to effective isolation. The effectiveness of isolation depends on the system's damping characteristics, which can reduce the amplitude of higher frequency vibrations. We can tune a container to capitalize on this effect by finding the sweet spot where the amplitude at resonance isn’t too high to cause damage, but it still creates isolation to dampen higher frequency vibration.
Now that we’ve discussed what shock and vibration are and how they can be harmful, how do we measure it, and what does it look like in practice?
The next presentation at the symposium was a discussion of crate design by Vincent Laudato Beltran of the Getty Conservation Institute. Vincent began the presentation by discussing how the Getty designs their crates to maximize protection from vibration, but the piece that was most relevant to our interests was the second half of his presentation, where he discussed monitoring several real pieces of artwork during real shipments.
The first example he gave focused on shock and involved sending a painting on a shipment that included segments on a truck and a flight on a plane. Before shipping the painting, he rigged the frame with two accelerometers and an air temperature and relative humidity sensor. He put another accelerometer on the inner crate lid and three more accelerometers on the exterior crate lid. Finally, he put another accelerometer on the floor of the truck to monitor that leg of the shipment and see what kind of acceleration was coming through the truck.
When the painting was traveling in a truck, he measured 2-3Gs of shock events, and the shock was effectively negligible while the shipment was in flight. Interestingly, the most significant shock events occurred while the painting was being handled by people at the airport and loaded onto the plane. Fortunately, it appears that his crate design was effective, and the high G events registered by accelerometers on the outside of the crate during this time at the airport were not picked up by the accelerometers closer to the artwork in the inner crate.
The second example was a sculpture that Vincent shipped on a truck from coast to coast. This sculpture was mounted on a frame with accelerometers on the top, middle, and bottom of the frame, as well as an additional accelerometer on the floor of the truck. He shared a plot of his data, and you can see the isolation that Bob and Dale had discussed in the previous presentation.
The lower frequency vibration matches up almost exactly. You can see some amplification from the natural frequency at about 10 Hz and significant isolation for higher frequency vibration. It is always satisfying when things work in practice the way you expect them to on paper.
This is just scratching the surface of the work that the art conservation community is doing to protect their assets, but it highlights the need to consider vibration when transporting important objects. Data collection and analysis are crucial to ensuring that your high-value assets are protected from shock and vibration during shipping and transit.