final presentation - mit opencourseware · final presentation 04/28/03 stefano a. alziati warren l....
TRANSCRIPT
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Slide 1
Simulating and Testing Ice Screw Performance in the Laboratory
FinalPresentation
04/28/03
Stefano A. AlziatiWarren L. M. Bennett
Advisors: Dr. Kim BlairDave Custer
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Slide 2
Introduction
� Project Motivation� Statement of Problem� Description of Experiment� Results & Discussion� Conclusion� Questions
Ice screw being pulled from Specimen
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Slide 3
Project Motivation
� The attraction of extreme sports is aiding its rapidly increasing popularity.
� Present safety equipment ineffective more accidents
� Project will be first step towards safer ice protection
� Very little published research available:� Harmston & Luebben Study, 1997
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Slide 4
Primary Hypothesis & Objectives
� Primary Hypothesis:The structure and morphology of different types of ice formations can be characterized and simulated in a lab to provide a �test bed� useful for assessment of ice screws.
� Primary Objective:To develop a repeatable means of reproducing ice in a lab and to characterize this ice using rheological data.
� Success Criteria:a) If hypothesis 1 is true, then success is characterizing the
critical properties of ice.b) If hypothesis 1 is false, then success is identifying why ice
cannot be made successfully.
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Slide 5
Secondary Hypothesis and Objective
� Secondary Hypothesis:If the first hypothesis is true, using the simulated ice, the variables affecting screw placement safety can be determined.
� Secondary Objective:To use laboratory created ice to test simulated falls on ice screws in a manner useful to climbers.
� Success Criteria:If hypothesis 2 is true, then success is the development of a test for ice screw safety that produces consistent and repeatable data for differing ice types.
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Slide 6
Description of Experiment
Stage 1: The characterization of ice� Produced different types of ice using different methods.
� Ice types chosen on ease of production and difference in characteristics
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Slide 7
Apparatus setup for stage 1 Preparing specimen for test
Experiment (cont�d)
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Slide 8
Experiment (cont�d)Stage 2: Testing of ice screws in ice
� Produced the two ice types on a larger scale.
� Placed ice screws at different angles into each specimen and pulled at different load rates.
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Slide 9
Experiment (cont�d)
Stage 2 Test Rig Close-up of Ice Screw/MTS interface
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Slide 10
Results � Stage 1Compressive Tests:� ABS 1:
� Compressive strength: 2203 lbs
� Std Dev: 638 lbs
� ABS 2:� Compressive strength:
1802 lbs� Std Dev: 618 lbs
� F-Stat: 9% chance of ABS1 being different to ABS2
Compressive load on ABS#1-3500
-3000
-2500
-2000
-1500
-1000
-500
00 5 10 15 20 25Time (s )
Compressive load on ABS#2-3500
-3000
-2500
-2000
-1500
-1000
-500
00 5 10 15 20 25Time (s )
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Slide 11
Results � Stage 1 (cont�d)
� Density:� ABS1: 913 kg m-3
� ABS2: 804 kg m-3
� F-Stat: 97% chance of ABS1 being different to ABS2.
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Slide 12
Discussion � Stage 1
� Compressive Test:
� Means are different, however this is not statistically significant
� Qualitatively different after testing� ABS1 still sticks to fingers� ABS2 feels wet to touch
� Graphs are different: � ABS1 peaks sharper� ABS2 peaks more rounded
Compressive load on ABS#1-3500
-3000
-2500
-2000
-1500
-1000
-500
00 5 10 15 20 25Time (s )
Compressive load on ABS#2-3500
-3000
-2500
-2000
-1500
-1000
-500
00 5 10 15 20 25Time (s )
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Slide 13
Discussion � Stage 1
� Density: � Shows definite difference between ABS1 and ABS2.
� Differentiated appearance between ABS1 and ABS2
� Relation to Hypothesis 1:� Valid hypothesis. Structure and morphology of different ice
types were simulated and characterized in the lab successfully.
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Slide 14
Results � Stage 2
� Typical ice screw test data set.
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Slide 15
Results � Stage 2
Previous study�s claim.
Screwangle
- ve 0 + ve
ABS2 (high rate)
ABS2 (low rate)
ABS1 (high rate)
ABS1 (low rate)Load
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Slide 16
Results � Stage 2
Results from the experiment.
Peak Mean Failure Load vs. Screw Placement angle
0
500
1000
1500
2000
2500
3000
-30 -20 -10 0 10 20 30Angle
Failu
re Lo
ad (l
bs)
ABS 1 (low rate)ABS 1 (high rate)ABS 2 (low rate)ABS 2 (high rate)
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Slide 17
Discussion � Stage 2
� Loading rate:
� Loading rate more significant than screw placement angle or ice type.
� Very useful for climbers. � loading rate can be controlled, using ropes that can stretch more and/or
using a friction device for slowing fall.
� No ice screw broken. Possibly due to:� development in ice screws over last six years� the length of screw� Temperature of the ice Screws� Loading rate of MTS machine not sufficient for breakage
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Slide 18
Discussion � Stage 2
� Screw placement:� Not much of an influence on the load taken. In general, zero angle is
the one that will hold the most.
Peak Mean Failure Load vs. Screw Placement angle
0
500
1000
1500
2000
2500
3000
-30 -20 -10 0 10 20 30Angle
Failu
re Lo
ad (l
bs)
ABS 1 (low rate)ABS 1 (high rate)ABS 2 (low rate)ABS 2 (high rate)
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Slide 19
Discussion � Stage 2
� Relation to Hypothesis:� Hypothesis proved.
� Variables affecting screw placement safety identified and tested.
� Ice type, loading rate and screw placement angle all affect safety.
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Slide 20
Conclusion
� Compressive Testing is not necessarily a valid test to differentiate between ice types.
� Fall Rate significantly affects failure load
� Screws safest at zero degrees� Previous work not supported by study
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Slide 21
Further work
� A test for assessing ice screw performance has been developed. Further improvements and developments possible:
� Research on methods for making more different ice types.� Determination of other tests that can characterize ice� Research on the effect of screw length on load.
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Slide 22
Acknowledgements
� Advisors Kim Blair & Dave Custer
� 622 Faculty Staff� Earl Murman, Ed Greitzer & Jennifer Pixley.
� Lab staff: � Dick Perdichizzi, John Kane, Don Wiener, Dave
Robertson & Paul Bauer.
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Slide 23
Questions
?
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Slide 24
Results � Stage 2
21%47229.75-301.0ABS1
32%14244601.0ABS1
68%481708+301.0ABS1
34%4101220-300.01ABS2
3%75237500.01ABS2
30%243810+300.01ABS2
51%276547+301.0ABS24%2569701.0ABS2
68%142211-301.0ABS2
24%3221329+300.01ABS118%294166000.01ABS122%3091394-300.01ABS1
SD/ meanStd. Dev.MeanAngleRateIce Type