So basically I've been fracture testing all year. Knowing me and the way projects generally work, I've been speed testing about 70% of all the specimens I have to do over the last couple of days, two weeks before the deadline. This is how the last couple of days went.
On Wednesday afternoon, I decided to be on the ball and head downstairs to the basement where they keep the high rate Instron - metal monstrosities of high pressure pipes and actuators, to set up my test rig so I would be able to make a bright breezy start on Thursday morning. Anticipating about an hour of setting up, I happily put on a lab coat and started collecting all the bits, spanners and adapters and what not.
It's always challenging to set up because the steel rig is unbelievably heavy, and you need quite a lot of brute force to make sure everything is screwed in tight. Not wanting to seem uber girly and helpless, I did it myself. Too bad the independent streak is not good for the other parts of my body, namely my wrist and shoulder, which twinged very painfully as I struggled to get it onto the chest-high metal base. This was on top of the random spasms that were already shooting through my arm after 16 hours of notching specimens, using an incredibly advanced set of tools consisting of a wooden hammer, a junior hacksaw, and a very sharp razor blade, for which I also suffered numerous cuts - in fact, it is such a dangerous task that one fellow left a trail of blood all the way across the adhesives lab in search of a sink and a band aid.
Moving along, when I had finally lined up the rig square with the machine and the actuator and bolted it down, set the span of the anvils after much grief and a lot of cursing of men and research in general, I was relatively pleased that I had remembered which part went where and that it looked fairly correct and it had only taken me the better part of an hour. Then I turned to look for the striker and the load cell, which were no where to be found. I spent half an hour searching for a small triangular prism and a load cell no bigger than a knuckle in what can only be described as a metal haystack of bolts, rods, adapters, and more metal bits. Further hell broke loose when I had to enlist the help of a lab technician who is rather fond of a rant or two himself, especially regarding missing bits. We gave up after another hour and I decided to email the head lab technician who knew where it had been hidden all along.
Thursday morning, I found the striker and the load cell sitting pretty with my rig on the test machine. Then it was a small task of connecting that to the actuator arm, hooking the cell up to an amplifier, and setting up the oscilloscope. We ran a couple of dry runs, but the machine kept dumping from high pressure to low pressure at the end of the stroke and refused to return. My heart dropped at the though of possibly having to manually move the ram back to the start position after every test. All seventy-seven of them. It would suck. Thankfully though, we discovered that it was just because the ram didn't like using the entire length of its stroke and seemed a lot happier when the start position was a little lower down. I was finally able to start testing two hours later.
The first specimen broke cleanly, as did the second, the traces showing an absolutely gorgeous triangle for both. I didn't think I'd ever be so excited about a set of lines on a computer screen, but I tell you, that was complete satisfaction. Foolishly, I thought all would be well. On the third, the trace that was recorded on the oscilloscope started to look as if a two-year-old child had sat down and tried to colour inside the lines. A small knot of fear settled in my stomach, but thought maybe it was the hydraulics acting up, decided to continue with the tests thinking it might work itself out. Six destroyed specimens later and eight tests that I would clearly have to repeat, and I was starting to get really upset. Each specimen takes me ten minutes to prepare. I decided to double check everything, which is probably what I should have done after the fourth failed test. As it turns out, the striker was loose. Tightening it, the next specimen broke well. I was back on course.
How stupid was I to think that. Two tests later and the noise came back - crazy scribbles in yellow and blue. Two more tests in the hope it would go back to normal, and I was back in the plastic box checking everything again. Smacked my forehead on the striker while trying to see round the back, and found that the wires from load cell to amplifier weren't tight. Gremlins, I swear, the lab is cursed. The next test was back to normal, thankfully, and before breaking the specimen after that, I checked absolutely everything I could think of, even wiggling the striker to make sure it was on tight, which, given my luck, broke off in my hand. Gayness.
I took it to the lab technician who was in a foul mood and was not helpful. Told me very rudely that the thread was shot and there was nothing he could do about it. He said I'd have to go and make a new striker if I wanted to keep testing, which, given my retarded manufacturing skills would have cost me a week which I did not have. A rainbow of curses ran through my head while I tried to maintain a straight face. I trudged back downstairs with a thunder cloud hanging over me. I was so far past caring, I forced the striker back onto the load cell using a spanner and it actually stuck. A couple more turns cut out a new thread in the soft aluminium and I managed to get the alignment I needed. Ha! I had spat in the face of adversity and walked away laughing.
The last hour of the afternoon came around and I was barely through the first 14 specimens with about half to repeat. Suddenly they weren't sitting nicely - the span was too long or the specimen was too short. I was confused and took out my trusty 50sen Popular ruler and found to my dismay that the span was indeed too long. This discovery had effectively negated any of those precious specimens that did break with a distinguishable and understandable trace, since it wasn't to the Linear Elastic Fracture Mechanics standards. The span was too wide. Grief and hysteria. So I adjusted that.
Footsore and covered in grease but angry as hell, I think the gremlins could feel it, and they knew that I would wrench their furry little heads off if I ever saw one. So the basement can get a little lonely sometimes. Every specimen was loaded with a fervent prayer and every 'perfect' trace was orgasmic.
Now I have to go back over each trace and analyze it carefully. About fifteen minutes to a trace, from previous experience, which means that there goes my entire weekend. The sickest thing about this is that all of these results are going to collapse into a single graph, not much bigger than a third of A4, but behind those pretty points on those extremely straight and aesthetic Excel-generated axes lies the blood, sweat, and tears of almost 100 hours of testing. Now you know.
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