SUOMEKSI - (English translation below)
Yhdestoista päivä toukokuuta testasimme LOFAR HBA-antennin kantavuutta osana LOFAR tekniikan arktista testausta. Saimme kuormattua elementin päälle n. 7650 kg vetistä lunta ennen antennin romahdusta. Testattu kuorma on kuitenkin yli kolme kertaa tarvittavaa kantavuutta suurempi.
Video näyttää styroksisen antennielementin viimeiset hetket ennen romahdusta liian suuren lumikuorman alla.
ENGLISH
On 11th May 2011, this High-Band Array antenna tile was loaded with approx. 7650 kg of snow and ice as part of Arctic testing. This video (whith both Finnish and English titles) shows the moments at the time of its collapse.
To see all the posts from the 'Destroying LOFAR' series, use the destructive test tag, or click on this link!
Showing posts with label destructive test. Show all posts
Showing posts with label destructive test. Show all posts
Wednesday, 1 June 2011
Monday, 30 May 2011
Destroying LOFAR — The last cell
'The year is 2011 C.E. All of the raised test-tile has succumbed to snow loading. All? Not quite! The indomitable Cell-#0 held out, as strong as ever...'
When the test tile collapsed, every cell in the tile was affected in some way. Either the wall collapsed, the innards were crushed, or the polystyrene was either bent or fractured. However, there was one exception.
This was Cell #0, which was located in the opposite far right corner from the location where the snow was being dumped. When we dismantled the tile, it turned out that both the cell walls and cell contents survived unaffected.
As a result, we carefully removed this unit, packed it, and transported it back to SGO. There is can be used as a reference and test cell.
The only cell to remain intact... just before being loaded into the van.
When the test tile collapsed, every cell in the tile was affected in some way. Either the wall collapsed, the innards were crushed, or the polystyrene was either bent or fractured. However, there was one exception.
This was Cell #0, which was located in the opposite far right corner from the location where the snow was being dumped. When we dismantled the tile, it turned out that both the cell walls and cell contents survived unaffected.
As a result, we carefully removed this unit, packed it, and transported it back to SGO. There is can be used as a reference and test cell.
The only cell to remain intact... just before being loaded into the van.Friday, 27 May 2011
Destroying LOFAR — Removing the frame
The final stage in clearing the area where the raised test tile was, is to get the frame itself out of the way. This also provided a useful test in that we could experiment with the moving of an entire frame using the 15-tonne digger provided by the local Kilpisjärvi contractor.
Markku Postila and Toivo Iinatti attach the lifting straps.
The frame is moved off the edge of the site.
With the frame completely moved, and ground tile also gone, the site is now fully clear ready for the ground preparation work for the complete build.
Ground works will actually start in a few weeks, giving plenty of time for some surface thawing of the ground, making it easier to work with.
Markku Postila and Toivo Iinatti attach the lifting straps.
The frame is moved off the edge of the site.With the frame completely moved, and ground tile also gone, the site is now fully clear ready for the ground preparation work for the complete build.
Ground works will actually start in a few weeks, giving plenty of time for some surface thawing of the ground, making it easier to work with.
Monday, 23 May 2011
Destroying LOFAR — Clear away
Now that the test tile has been destroyed, and the data regarding its structural failure accumulated, we need to clear the debris away so that the site can be prepared for the main build.
Markku Postila pulls fragments from the HBA wreck.
Late into the 'night', the team continue working to get the frame clear.
Markku Postila pulls fragments from the HBA wreck.
Late into the 'night', the team continue working to get the frame clear.Thursday, 19 May 2011
Destroying LOFAR — Post Mortem
With the HBA cleared, we can start to analyse what caused the tile to fail and in what way that failure propagated through the structure.
Looking at the split-point in the tile. The cover was not damaged at all.
Here we've peeled back the cover to reveal the
end column. Cell 11 is split down the middle.
Removing half of the lid shows the destruction inside.
The complete mess inside Cell 11.
With the shards removed from the cell content,
the failure of the cell walls can clearly be seen.
A full catalogue of damages was made, along with hundreds of photographs. Although the analysis of the tile failure is mostly a curiosity for the already-deployed LOFAR network, this is a crucial learning opportunity for the proposed EISCAT_3D system.
Looking at the split-point in the tile. The cover was not damaged at all.
Here we've peeled back the cover to reveal the end column. Cell 11 is split down the middle.
Removing half of the lid shows the destruction inside.
The complete mess inside Cell 11.
With the shards removed from the cell content, the failure of the cell walls can clearly be seen.
A full catalogue of damages was made, along with hundreds of photographs. Although the analysis of the tile failure is mostly a curiosity for the already-deployed LOFAR network, this is a crucial learning opportunity for the proposed EISCAT_3D system.
Wednesday, 18 May 2011
Destroying LOFAR — Removing the last of the snow
Although the digger could remove much of the 7.6-tonnes of snow and ice on the destroyed HBA tile, we did not want to risk disturbing the broken pieces and thus confuse the damage caused by the collapse with additional destruction from the clearing process.
Therefore, the remaining few tonnes were done by hand.
Here is the author digging out the area over the collapsed cells.
As we were clearing, there were numerous places where
melt water was starting to stream off the tile edge.
Markku Postilla clears the final few patches of
ice. Saana Mountain is in the background.
Therefore, the remaining few tonnes were done by hand.
Here is the author digging out the area over the collapsed cells.
As we were clearing, there were numerous places where melt water was starting to stream off the tile edge.
Markku Postilla clears the final few patches ofice. Saana Mountain is in the background.
Tuesday, 17 May 2011
Destroying LOFAR — Starting to remove the snow
Left with a mountain of snow on the collapsed HBA tile, it is now time to clear that snow away again, so that we can dissect the corpse of the deal antenna shell.
The first part of this is to shift the bulk of the ice-mountain. This was done using the 15-tonne digger.
This operation was carried out just as carefully as the initial placement. What we did not want to do was to pack the snow any further, nor generate additional damage by disturbing the now fragile tile pieces with movement from the digger bucket.
Once removed, the snow could be then safely dumped off the edge of the mound which will ultimately be the full HBA site.
The first part of this is to shift the bulk of the ice-mountain. This was done using the 15-tonne digger.
This operation was carried out just as carefully as the initial placement. What we did not want to do was to pack the snow any further, nor generate additional damage by disturbing the now fragile tile pieces with movement from the digger bucket.
Once removed, the snow could be then safely dumped off the edge of the mound which will ultimately be the full HBA site.
Monday, 16 May 2011
Destroying LOFAR — Collapse!
Firstly, we'll start this report with a quick apology for all of those who have been sitting clicking 'refresh' on their browsers for the last couple of days. There have been some technical problems with the web log provider, which have caused some delays in posting the next reports on the LOFAR destruction tests.
However...
When we last left our heroes, they have piled over seven-and-a-half tonnes of icy snow on the raised HBA tile. An ominous crack had been heard and the digger engine was shut off and the team started checking the tile, noting some deformation under one of the cells.
Then, we started hearing clicks and creaks. As the gentle movement of Arctic air played over the mound of ice, the creaking would intensify and then subside. It genuinely sounded like being on an old sailing ship, with its wooden hull and masts flexing in the swell and breeze.
And then, the clicks and snaps and pops and creaks started to pick up pace and with a rush of noise that sounded like a tree being felled, there was splintering sound a sudden crash and most of the tile (and the snow on it) dropped down 20cm or so.
Part of the tile edge, showing the crushed tile.
The tile label and one of the anchor points. As the tile
did not fall through completely, no anchors broke.
As can be seen in this last image, the south-west side seems
to have remained partially intact. This is was, of course,
where the pile of snow was the thinnest, and also on the
opposite side of where the digger was dumping the snow.
What needs to be done now is to carefully clear the snow off the tile and then systematically dismantle the remains. What we want to do is look for not only the extent of the damage, but also the failure modes that triggered during the final milliseconds of this tile's life.
However...
When we last left our heroes, they have piled over seven-and-a-half tonnes of icy snow on the raised HBA tile. An ominous crack had been heard and the digger engine was shut off and the team started checking the tile, noting some deformation under one of the cells.
Then, we started hearing clicks and creaks. As the gentle movement of Arctic air played over the mound of ice, the creaking would intensify and then subside. It genuinely sounded like being on an old sailing ship, with its wooden hull and masts flexing in the swell and breeze.
And then, the clicks and snaps and pops and creaks started to pick up pace and with a rush of noise that sounded like a tree being felled, there was splintering sound a sudden crash and most of the tile (and the snow on it) dropped down 20cm or so.
Part of the tile edge, showing the crushed tile.
The tile label and one of the anchor points. As the tiledid not fall through completely, no anchors broke.
As can be seen in this last image, the south-west side seemsto have remained partially intact. This is was, of course,
where the pile of snow was the thinnest, and also on the
opposite side of where the digger was dumping the snow.
What needs to be done now is to carefully clear the snow off the tile and then systematically dismantle the remains. What we want to do is look for not only the extent of the damage, but also the failure modes that triggered during the final milliseconds of this tile's life.
Thursday, 12 May 2011
Destroying LOFAR — Load #9
Our vendetta against this LOFAR HBA tile continues. Will the polar caps disappear before we find enough snow to crush this thing? Here the digger drives up with another tonne of snow.
The snow goes on and there is no collapse. The total mass on the tile now exceeds seven-and-a-half tonnes.
But wait! Just after the load goes on, there is an ominous 'CRACK'. It was not clear if that was part of the HBA failing, or whether it was the settling of the packed snow. We switch off the digger to wait and listen.
After all the noise of the great machine, there is deathly silence. This part of the world can be so still and tranquil. And yet there is a palpable tension in the air.
Like every load, we check the tile from different angles and take photographs. But now there is a hint that something might have happened.
However, despite the sound the tile looks intact. There is no partial collapse of the wall and the mound looks intact, as if there was no deformation. But then we notice the underside of the tile.
Around the location of Cell 10 and 11 (an HBA tile comprises 16 cells), there is slight bulge that was not there after the application of Load #8. The displacement seems to only be about 5cm, but this is the first deformation that we have seen since the testing started.
The catastrophic failure hadn't happened. But at least were were now seeing some form of distortion due to the loading. It was also noted that the distortion was occurring in a single place, which was more-or-less directly under the location where the digger was placing the snow. As a consequence, this was also the area where the snow had been piling up the highest so it was no surprise that the flexing was only being seen there.
But then what happened next took us all by surprise.
Tune in tomorrow for the report!
The snow goes on and there is no collapse. The total mass on the tile now exceeds seven-and-a-half tonnes.
Load Mass Total
#1 400kg 400kg
#2 550kg 950kg
#3 950kg 1900kg
#4 1050kg 2950kg
#5 850kg 3800kg
#6 1400kg 5200kg
#7 500kg 5700kg
#8 1050kg 6750kg
-100kg 6650kg
#9 1000kg 7650kg
But wait! Just after the load goes on, there is an ominous 'CRACK'. It was not clear if that was part of the HBA failing, or whether it was the settling of the packed snow. We switch off the digger to wait and listen.
After all the noise of the great machine, there is deathly silence. This part of the world can be so still and tranquil. And yet there is a palpable tension in the air.
Like every load, we check the tile from different angles and take photographs. But now there is a hint that something might have happened.
However, despite the sound the tile looks intact. There is no partial collapse of the wall and the mound looks intact, as if there was no deformation. But then we notice the underside of the tile.
Around the location of Cell 10 and 11 (an HBA tile comprises 16 cells), there is slight bulge that was not there after the application of Load #8. The displacement seems to only be about 5cm, but this is the first deformation that we have seen since the testing started.
The catastrophic failure hadn't happened. But at least were were now seeing some form of distortion due to the loading. It was also noted that the distortion was occurring in a single place, which was more-or-less directly under the location where the digger was placing the snow. As a consequence, this was also the area where the snow had been piling up the highest so it was no surprise that the flexing was only being seen there.
But then what happened next took us all by surprise.
Tune in tomorrow for the report!
Destroying LOFAR — Load #8
I don't know why I started this web log series with the title 'Destroying LOFAR'. By this stage we're seriously wondering if LOFAR is actually indestructible and if the 'monoliths' from the Arthur C Clarke book '2001 — A Space Oddessy' were actually in fact some sort of LOFAR HBA tile?
Thinking that the last load was a bit light, we've gone back to one-tonne loads of snow from the digger bucket.
The mound grows ever higher.
However, we also had our first avalanche. It wasn't much, but a few chunks of ice fell away from the back of the tile (opposite the side that the digger was approaching from). We did a check and estimated that the mass of lost material was probably somewhere in the range of 50 to 100 kg. Even so, we're still over six-and-a -half tonnes of snow and ice on our HBA tile.
Still need more snow.
Thinking that the last load was a bit light, we've gone back to one-tonne loads of snow from the digger bucket.
The mound grows ever higher.
However, we also had our first avalanche. It wasn't much, but a few chunks of ice fell away from the back of the tile (opposite the side that the digger was approaching from). We did a check and estimated that the mass of lost material was probably somewhere in the range of 50 to 100 kg. Even so, we're still over six-and-a -half tonnes of snow and ice on our HBA tile.
Load Mass Total
#1 400kg 400kg
#2 550kg 950kg
#3 950kg 1900kg
#4 1050kg 2950kg
#5 850kg 3800kg
#6 1400kg 5200kg
#7 500kg 5700kg
#8 1050kg 6750kg
-100kg 6650kg
Still need more snow.
Destroying LOFAR — Load #7
Surely we must be getting close? Or would our snow-supply have melted away before we finished the task.
Another load (albeit smaller this time) was added to the pile.
This photograph does a good job of showing the problem we're now facing. We've more-or-less covered the entire tile surface. There are still no signs of it collapsing and we are starting to wonder if we need some alternative testing method.
Another load (albeit smaller this time) was added to the pile.
This photograph does a good job of showing the problem we're now facing. We've more-or-less covered the entire tile surface. There are still no signs of it collapsing and we are starting to wonder if we need some alternative testing method.
Load Mass Total
#1 400kg 400kg
#2 550kg 950kg
#3 950kg 1900kg
#4 1050kg 2950kg
#5 850kg 3800kg
#6 1400kg 5200kg
#7 500kg 5700kg
Destroying LOFAR — Load #6
Did we say were were getting serious last time? Hmm... that was nothing.
This time we threw on 1400kg of snow taking the total well beyond the five-tonne mark. This was the heaviest load yet applied, and it came down hard on the tile. However, as you can see, the tile held up just fine.
Just for reference, the frameset is 1.0 metres high and the tile itself is about 0.5 metres or so. The summit of our snow mountain was about 1.5 metres high at this point — some 3 metres off the ground. It was certainly impressive to see.
This time we threw on 1400kg of snow taking the total well beyond the five-tonne mark. This was the heaviest load yet applied, and it came down hard on the tile. However, as you can see, the tile held up just fine.
Just for reference, the frameset is 1.0 metres high and the tile itself is about 0.5 metres or so. The summit of our snow mountain was about 1.5 metres high at this point — some 3 metres off the ground. It was certainly impressive to see.
Load Mass Total
#1 400kg 400kg
#2 550kg 950kg
#3 950kg 1900kg
#4 1050kg 2950kg
#5 850kg 3800kg
#6 1400kg 5200kg
Destroying LOFAR — Load #5
Okay... this is getting serious. Would we actually be able to damage a tile with snow? Undeterred (so far) we press on with another load.
The load is piled on to the tile
And we are now well over three-and-a-half tonnes with no ill-effect.
In fact, the mountain of snow is now so high, that it is getting difficult to reach the top to dump more snow (we didn't expect this eventuality). As a result, we decided to spread the snow out a little bit, to allow us to put even more loading on it. This was done by getting the digger to push the summit of our HBA-snow-mountain out to cover more entire of the tile surface.
This work was the first time we noticed any deformation. As the digger pushed the snow across the pile, there was a lateral movement of the tile, where the base remained fixed to the frame, but the top of the tile would move laterally as the snow was pushed. This lateral movement was small, but it was distinct and we thought for a moment that the vertical loading capacity of the tile would be fine, but that the tile would concede when subjected to a shearing force.
But no.
The tile remained intact... and we went off to get more snow. The score now stands are:
The load is piled on to the tile
And we are now well over three-and-a-half tonnes with no ill-effect.
In fact, the mountain of snow is now so high, that it is getting difficult to reach the top to dump more snow (we didn't expect this eventuality). As a result, we decided to spread the snow out a little bit, to allow us to put even more loading on it. This was done by getting the digger to push the summit of our HBA-snow-mountain out to cover more entire of the tile surface.
This work was the first time we noticed any deformation. As the digger pushed the snow across the pile, there was a lateral movement of the tile, where the base remained fixed to the frame, but the top of the tile would move laterally as the snow was pushed. This lateral movement was small, but it was distinct and we thought for a moment that the vertical loading capacity of the tile would be fine, but that the tile would concede when subjected to a shearing force.
But no.
The tile remained intact... and we went off to get more snow. The score now stands are:
Load Mass Total
#1 400kg 400kg
#2 550kg 950kg
#3 950kg 1900kg
#4 1050kg 2950kg
#5 850kg 3800kg
Destroying LOFAR — Load #4
Could we actually get an entire tonne of snow into the digger bucket? Well, with the HBA tile still sitting there unfazed, we decided that now was the time to try.
Whumpp!
Over a tonne of snow lands on the tile... which doesn't even flinch. The score now, showing the mass of each individual load, and the new cumulative total that it would amount to is as follows:
Wot? More snow needed?
Whumpp!
Over a tonne of snow lands on the tile... which doesn't even flinch. The score now, showing the mass of each individual load, and the new cumulative total that it would amount to is as follows:
Load Mass Total
#1 400kg 400kg
#2 550kg 950kg
#3 950kg 1900kg
#4 1050kg 2950kg
Wot? More snow needed?
Destroying LOFAR — Load #3
With no discernible damage to the tile, it was time to start getting tough. Rather than easing on a few hundred kilogrammes at a time, we decided to place a larger load.
This time the digger scooped up 950kg of snow. This would double the total quantity that was already on the tile. We expectantly waited for the crash...
... nothing happened. The snow fell from the digger bucket, now piling even higher on the tile. We now have a serious weight being applied to this HBA tile.
Still more snow needed!
This time the digger scooped up 950kg of snow. This would double the total quantity that was already on the tile. We expectantly waited for the crash...
... nothing happened. The snow fell from the digger bucket, now piling even higher on the tile. We now have a serious weight being applied to this HBA tile.
Load Mass Total
#1 400kg 400kg
#2 550kg 950kg
#3 950kg 1900kg
Still more snow needed!
Destroying LOFAR — Load #2
During the tests there were numerous members of the team taking photographs. In addition we also had a video camera running ready to catch the moment of collapse.
So, having successfully placed the first load, we then proceeded to put on a second. This time the digger bucket weighed in with a total of 550 kilogrammes of new snow.
Again, the tile withstood the load. So, the score now stands at:
More snow needed!
So, having successfully placed the first load, we then proceeded to put on a second. This time the digger bucket weighed in with a total of 550 kilogrammes of new snow.
Again, the tile withstood the load. So, the score now stands at:
Load Mass Total
#1 400kg 400kg
#2 550kg 950kg
More snow needed!
Destroying LOFAR — Load #1
With the initial preparation work completed, it is time to actually go for it. So, with the area cleared, the digger ready, staff on stand-by, and cameras rolling, the first load of snow was gingerly dropped onto the raised test tile.The digger had picked up four hundred kilogrammes of snow and was going to attempt to drop half of it onto the tile.
We held our breath.
As the sequence shows, the first drop went on just fine. The tile showed no sign of stress or strain and so the remainder of the digger bucket was also put onto the tile. Thus, a 400 kg load was in place and the tile (or at least part of it) was hold it out without any problems. We also didn't have any problems with the snow not leaving the digger bucket or issues to do with the reach of the digger to a suitable drop area. Additionally, all the snow that was in the bucket actually then stayed in a solid pile on the tile, without any sliding or blowing off.
So, the result that we have so far is as follows:
Load Mass Total#1 400kg 400kg
With smiles all around, we sent the digger over to get a second load of about the same size. But the outcome of the next dump of snow will be in the next post, which will be posted up in the next hour or so.
Destroying LOFAR — Preparation
Before starting, we experimented with the digger by scooping up loads of snow and dumping them on the ground. Using the same technique that we used for the ice/snow core samples we checked the density and condition of the material we had to use.
As it turned out, the snow in the area was very dense. It was also icy, bordering on slushy in places. This means that it would pack well and, when piled up compress into an even denser mix. This was not quite what we'd hoped for, as we had anticipated more powdery snow. However, the area had been subjected to some (relatively) warm weather and prolonged sunshine.
In addition to the snow tests, we also used the digger to clear the surrounding area.
This would give us a good view of the frames and underside of the tile and permit easy access.
Coming next... the first load of snow is placed on the tile!
As it turned out, the snow in the area was very dense. It was also icy, bordering on slushy in places. This means that it would pack well and, when piled up compress into an even denser mix. This was not quite what we'd hoped for, as we had anticipated more powdery snow. However, the area had been subjected to some (relatively) warm weather and prolonged sunshine.
In addition to the snow tests, we also used the digger to clear the surrounding area.
This would give us a good view of the frames and underside of the tile and permit easy access.
Coming next... the first load of snow is placed on the tile!
Destroying LOFAR — Introduction
One of the purposes of the winter testing, was to check whether a conventional LOFAR High-Band Array (HBA) tile would withstand the Arctic conditions. Apart from the sustained cold temperatures and the high-winds, the main concern was the loading of snow on the tile.
As we have seen during the last few days, the full site inspection has revealed that both test tiles (the raised tile and the one on the ground) have survived the winter intact.
This is a major relief.
What this means is that the conditions that we incurred over winter were insufficient to damage the tile. But what about the extreme case. And just because it didn't break, doesn't mean that it didn't come even close. Therefore we'd like to do an experiment (umm, what did you expect... we're scientists!)
This is the HBA tile:
It is the raised tile as seen after the surrounding snow had been cleared away, measurements have been done and initial testing completed. So, the idea is to deliberately put some snow on it.
This is the digger:
Over the course of the next few hours, we were going to use this 15-tonne machine to gently put snow onto the tile. The digger has a built-in load measuring system, so we can weight the snow as we pile it on to the HBA tile.
What we are looking for is:
a) What is the breaking point? That is, how many tens, or even hundreds, of kilogrammes of snow can we place on the tile before it collapses?
b) What is the mode of failure? In other words, which part gives way first? Do the lids fail, or the walls, or the timber supporting frame underneath?
If you want to have a guess, do it now... and then stay tuned over the next few hours as we post up the results.
As we have seen during the last few days, the full site inspection has revealed that both test tiles (the raised tile and the one on the ground) have survived the winter intact.
This is a major relief.
What this means is that the conditions that we incurred over winter were insufficient to damage the tile. But what about the extreme case. And just because it didn't break, doesn't mean that it didn't come even close. Therefore we'd like to do an experiment (umm, what did you expect... we're scientists!)
This is the HBA tile:
It is the raised tile as seen after the surrounding snow had been cleared away, measurements have been done and initial testing completed. So, the idea is to deliberately put some snow on it.
This is the digger:
Over the course of the next few hours, we were going to use this 15-tonne machine to gently put snow onto the tile. The digger has a built-in load measuring system, so we can weight the snow as we pile it on to the HBA tile.
What we are looking for is:
a) What is the breaking point? That is, how many tens, or even hundreds, of kilogrammes of snow can we place on the tile before it collapses?
b) What is the mode of failure? In other words, which part gives way first? Do the lids fail, or the walls, or the timber supporting frame underneath?
If you want to have a guess, do it now... and then stay tuned over the next few hours as we post up the results.
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