Investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice
Approximately 50% of ice mass loss from ice sheets is due to icebergs breaking off in a process called calving. Icebergs are created through the incremental growth of crevasses, which are large fractures in the ice. Crevasse propagation and iceberg calving predictions within ice sheet models conflic...
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Montana State University - Bozeman, College of Engineering
2021
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ftmontanastateu:oai:scholarworks.montana.edu:1/16234 2023-05-15T13:44:27+02:00 Investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice Alcorn, Derek West Chairperson, Graduate Committee: Edward E. Adams 2021 application/pdf https://scholarworks.montana.edu/xmlui/handle/1/16234 en eng Montana State University - Bozeman, College of Engineering https://scholarworks.montana.edu/xmlui/handle/1/16234 Copyright 2021 by Derek West Alcorn Icebergs Ice Fracture mechanics Forecasting Mathematical models Thesis 2021 ftmontanastateu 2023-02-25T23:40:30Z Approximately 50% of ice mass loss from ice sheets is due to icebergs breaking off in a process called calving. Icebergs are created through the incremental growth of crevasses, which are large fractures in the ice. Crevasse propagation and iceberg calving predictions within ice sheet models conflict with direct observations of crevasse processes. Current ice sheet models assume that a crevasse will propagate until it reaches a depth where the stress intensity factor at the crack tip is less than that of crack initiation, however, this is likely an oversimplification as current models over estimate crevasse depth. A more robust model would also account for the crack arrest fracture toughness, a measure of how well a material can stop an already propagating crack. Here, we calculate crack arrest fracture toughness for samples of laboratory-manufactured polycrystalline ice. These samples were created using a radial freezing technique with a reproducible grain size distribution of 0.95 mm + or - 0.28 mm analyzed by cross-polarized light. Specimens were notched and brought to failure via a short-rod fracture toughness test at controlled temperatures and a constant displacement rate in a commercial mechanical testing apparatus with an environmental chamber. The presented data agrees with short-rod fracture toughness data collected from ice cores at the Filchner- Ronne Ice Shelf in Antarctica, demonstrating quasi-stable crack growth behavior. Results show the crack arrest fracture toughness of laboratory-manufactured polycrystalline ice is approximately 25 - 50% of fracture toughness. Using the crack arrest fracture toughness determined in this study would further increase modeled crevasse depth, indicating more analysis is required. Future studies can incorporate these data to more accurately determine crevasse penetration depth and improve iceberg calving predictions within ice sheet models. Thesis Antarc* Antarctica Filchner Ronne Ice Shelf Filchner-Ronne Ice Shelf Ice Sheet Ice Shelf Ronne Ice Shelf Montana State University (MSU): ScholarWorks Ronne Ice Shelf ENVELOPE(-61.000,-61.000,-78.500,-78.500) |
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Open Polar |
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Montana State University (MSU): ScholarWorks |
op_collection_id |
ftmontanastateu |
language |
English |
topic |
Icebergs Ice Fracture mechanics Forecasting Mathematical models |
spellingShingle |
Icebergs Ice Fracture mechanics Forecasting Mathematical models Alcorn, Derek West Investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice |
topic_facet |
Icebergs Ice Fracture mechanics Forecasting Mathematical models |
description |
Approximately 50% of ice mass loss from ice sheets is due to icebergs breaking off in a process called calving. Icebergs are created through the incremental growth of crevasses, which are large fractures in the ice. Crevasse propagation and iceberg calving predictions within ice sheet models conflict with direct observations of crevasse processes. Current ice sheet models assume that a crevasse will propagate until it reaches a depth where the stress intensity factor at the crack tip is less than that of crack initiation, however, this is likely an oversimplification as current models over estimate crevasse depth. A more robust model would also account for the crack arrest fracture toughness, a measure of how well a material can stop an already propagating crack. Here, we calculate crack arrest fracture toughness for samples of laboratory-manufactured polycrystalline ice. These samples were created using a radial freezing technique with a reproducible grain size distribution of 0.95 mm + or - 0.28 mm analyzed by cross-polarized light. Specimens were notched and brought to failure via a short-rod fracture toughness test at controlled temperatures and a constant displacement rate in a commercial mechanical testing apparatus with an environmental chamber. The presented data agrees with short-rod fracture toughness data collected from ice cores at the Filchner- Ronne Ice Shelf in Antarctica, demonstrating quasi-stable crack growth behavior. Results show the crack arrest fracture toughness of laboratory-manufactured polycrystalline ice is approximately 25 - 50% of fracture toughness. Using the crack arrest fracture toughness determined in this study would further increase modeled crevasse depth, indicating more analysis is required. Future studies can incorporate these data to more accurately determine crevasse penetration depth and improve iceberg calving predictions within ice sheet models. |
author2 |
Chairperson, Graduate Committee: Edward E. Adams |
format |
Thesis |
author |
Alcorn, Derek West |
author_facet |
Alcorn, Derek West |
author_sort |
Alcorn, Derek West |
title |
Investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice |
title_short |
Investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice |
title_full |
Investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice |
title_fullStr |
Investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice |
title_full_unstemmed |
Investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice |
title_sort |
investigation of crack arrest fracture toughness of laboratory-manufactured polycrystalline ice |
publisher |
Montana State University - Bozeman, College of Engineering |
publishDate |
2021 |
url |
https://scholarworks.montana.edu/xmlui/handle/1/16234 |
long_lat |
ENVELOPE(-61.000,-61.000,-78.500,-78.500) |
geographic |
Ronne Ice Shelf |
geographic_facet |
Ronne Ice Shelf |
genre |
Antarc* Antarctica Filchner Ronne Ice Shelf Filchner-Ronne Ice Shelf Ice Sheet Ice Shelf Ronne Ice Shelf |
genre_facet |
Antarc* Antarctica Filchner Ronne Ice Shelf Filchner-Ronne Ice Shelf Ice Sheet Ice Shelf Ronne Ice Shelf |
op_relation |
https://scholarworks.montana.edu/xmlui/handle/1/16234 |
op_rights |
Copyright 2021 by Derek West Alcorn |
_version_ |
1766201749650014208 |