Ice598: Standard ice (g.s. 0.2 - 0.6 mm)
Constant (±2%) strain rate. Continue with sample of run 598a. |
| Forward to Ice609 |
| P = 100 MPa, T = 198 K, edot ≈ 6e-7/s | Steps (1a), (1b), (1c), (1d), (1e), 1f) |
Legend: Upper graph of each pair is motor speed V (proportional to edot); lower graph is load (in volts). Translate motor V to edot thus: for 100:1 gearing, V0.05 ≈ 3e-8/s; for 10:1 gearing, V0.05≈3e-7/s. Load to stress translation is 1.28 MPa/mV. Horizontal scale is time. 5000≈14 hrs. |
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e=0.238 | 1234 hrs 5/1. End of step (1f) and of run. Whew! |
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1909 hrs 4/29 | |
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e=0.222 | 0621 hrs 4/29 |
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1847 hrs 4/28 | |
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e=0.209 | 0545 hrs 4/28. Start of step (1f). So why is motor V so high? edot is running about 10% faster here than at start of run. Was there a problem with the force gage zero, perhaps? |
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Step (1f) startup. | |
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End of step (1e). | |
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e=0.195 | 0220 hrs 4/27. |
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e=0.189 | 1511 hrs 4/26. Ditto. |
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e=0.182 | 0116 hrs 4/26. Step (1e) continues. |
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e=0.176 | 1337 hrs 4/25. Step (1e) continues. |
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e=0.168 | 0055 hrs 4/25. Start of step (1e) |
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Nice start to step (1e). Deft manipulation of LabView allows manually controlled motor V to be displayed on the upper chart. Takes barely 10 minutes to resume steady state s and edot. | |
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e≈0.162 | ~1430 hrs 4/24. End step(1d) |
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e=0.156 | 0200 hrs 4/24. Continuing step (1d) |
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e=0.151 | 11731 hrs 4/23. Continuing step (1d) |
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e=0130 | 0130 hrs 4/23. Continuing step (1d) |
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e=0.135 | 1307 hrs 4/22. Continuing step (1d). |
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e=0.128 | 0032 hrs 4/22. Start of step (1d). So what is that worrisome >0.5 mV drop in stress near the beginning of the run? Zero should probably be rechecked as soon as possible? |
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4/21 afternoon sometime. Detail of start of step (1d). Another 3% downward adjustment of motor V to hold constant edot. Note that V0.26 value on the upper chart is misleading. The operator is probably overriding this value manually in background in order to reach s.s. stress level as rapidly as possible. There is a way to display the manual operation on the chart. If the Operator could stop by 54-720 to visit, perhaps we could discuss this... | |
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e=? | 4/21 afternoon sometime. End of step (1c) |
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e=0.119 | 0639 hrs 4/21, step (1c) continues. About time for another zero check, don't you think... |
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e-0.112 | 1904 hrs 4/20. Downward dip in s at ~1000-1100 hrs is recovery from a slow 1 K warming over the previous 6-10 hrs caused by a bad LN tank. |
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e=0.100 | 0804 hrs 4/20, step (1c) continues. |
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e=0.098 | 1913 hrs 4/19. edot decreased another 3% a couple of hours ago. |
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e=0.091 | 0747 4/19 Patriots Day. Step (1c) continues, with more of those odd spikes on the s trace. Might be time to drop motor V another 3% pretty soon... |
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e=0.080 | 1744 hrs 4/18. Beginning moments of step (1c), Sabrina showing stunning mastery of motor speed control to hold constant s during machine transients at start of step. |
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e=0.080 | 1653 hrs 4/18. End of step (1b). Do s gage zero check. |
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e=0.074 | 0709 hrs 4/18. |
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e=0.066 | 1842 hrs 4/17. Another 3% downward correction of edot. What is s doing?? |
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e=0.058 | 0644 hrs 4/17. Note 3% downward correction of edot from V0.030 to 0.029 |
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e=0.050 | 1910 hrs 4/16. We aren't sure what the cause of the spikes is on the load curve, something electronic for sure. |
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e=0.041 | 0632 hrs 4/16. Start of step (1b), continuing after zero check of force gage. |
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e=0.0324 | ~6hrs later, just before unloading for quick zero check of fore gage as well as gear change. Downward drift in s turns out to match offset in unloaded force gage reading. Not sure what that sharp dip is near the end; it is not hugely significant, given the fine scale of the chart. |
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e=0.0280 | 0835 hrs 15 Apr. Expanded stress scale, overlapping a bit with previous, showing a 3-4% drop in stress. Effective edot has increased (by about 2.8% of course), so edot is not the cause. It may be a weak expression of the transient yield phenomenon we used to observe at higher strain rates or (more likely) is just drift in the force gage zero. We will see when Sabrina checks the force gage zero later on today... |
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e=0.022 | 0054 hrs 15 Apr. Stress is about 14 MPa (stress = 0 corresponds to 0.005 V on lower chart). |
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e=0.011 | 14 Apr 0939 hrs. Got started last night. 10:1 gearing. Hopefully this will be swapped for 100:1 so that we may be able to maintain constant edot... |