When acrylic aquariums fail (2018) | Hacker News Reader

When acrylic aquariums fail (2018)

plasticstoday.com

37 pointsjacquesm12 comments

Very fascinated by this topic. Plenty of examples of failures and their cause, but nothing about how to inspect, detect and prevent. Any followup links?

Most recent fail: https://www.cbsnews.com/news/aquarium-berlin-hotel-radisson-...

This is most likely the reason for this post

I've found a video [1] on youtube, describing the failures listed in the article in plasticstoday. When i watch the videos seem several of them to fail at the bond between elements of the construction.

[1] https://www.youtube.com/watch?v=tsOvppPL2qU

So these aquariums have a design factor of safety of 11?? And still regularly fail?

To me, that shows something majorly wrong in the design/build process... Clearly some failure modes are not well understood/modelled.

Planes, the safest transportation vehicle by far, have a design factor of safety of 1.5 for example. And even then, failures due to material stress are rather rare.

I'm surprised that ultrasonic transducers cannot be used to search for cracks or developing imperfections. Can one launch surface-localized waves at one place, pick them up relatively far away on the surface?

Having used acrylic for various projects... It's a hard to use material.

It loves to crack - especially around drill holes and sharp corners, even when not much external load is applied due to internal stresses.

Tl;dr stress concentrations such as scratches and gouges can lead to sudden failures in acrylic structures under pressure.

That was, for me, the least interesting of the failure modes mentioned, the most alarming being:

> The phenomenon behind this is called creep rupture—the disentanglement of the molecules of plastic over time, at a stress level significantly below the yield strength—yes, below the yield strength—of the plastic.

Also known as crack propagation, but yes interesting to see in non metals.

It is standard for high pressure equipment and welds to get xray tested. Should be the same for these structures too especially as they age.

What would be the method and tooling involved to xray such large and unique structures? Is there a US company specialising in the service or who typically does it?

Here's an example :

https://www.mistrasgroup.com/how-we-help/field-inspections/a...

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