the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 03 Jan 2024
Research of mechanical model based on characteristics of facture mechanics of ice cutting for scientific drilling in polar region
Abstract. Scientific drilling in polar regions plays a crucial role in obtaining ice cores and using them to understand climate change and to study the dynamics of the polar ice sheet and its impact on global environmental changes (sea level, ocean current cycle, atmospheric circulation, etc.). Mechanical rotary cutting is a widely used drilling method that drives the cutter to rotate to cut and drill through ice layers. It is necessary to conduct in-depth research on the brittle fracture behavior of ice and mechanical model, and analyze the factors and specific mechanisms (cutter’s angle, rotation speed of the drill bit, and cutting depth) affecting cutting force for the rational design of ice-core drill system, improving the efficiency of ice-core drilling, and ensuring the drilling process smoothly. Therefore, in this paper, the process of ice cutting was observed, the fracture mechanics characteristics of ice cutting process wad analyzed, the formation process of ice chips was divided into three stages, and the mathematical model for the cutting force was established based on the observation results. It describes the damage conditions of ice failure and points out the influencing factors and specific influencing laws on cutting force. Furthermore, the cutting force generated under various experimental conditions was tested. Based on typical real-time data curves of cutting force, the characteristics of cutting force were analyzed during the cutting and drilling process. Based on the comparison results of the average cutting force, the influence mechanism of various parameters on the cutting force is obtained. This proves the correctness of the mathematical model of the cutting force and provides a theoretical reference for the calculation of cutting force during ice cutting and drilling in polar regions.
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RC1: 'Comment on egusphere-2023-2985', Anonymous Referee #1, 10 Mar 2024
The investigation collected some useful information, but I believe it fell short of exploring significantly novel findings. The geometry of the bit remained within existing design and ice properties were neglected. The setup should have been used to explore beyond the range of what is currently used in ice drills to expand into novel territory and give evidence to drive changes to current technology.
- The most interesting finding to me was seen in Figure 9 and discussed in lines 246 to 254; the low frequency oscillations from the formation and clearing of ice chips. I would like to see this concept expended – inherently all ice drills deflect under load so is it possible the oscillating cutting force creates a harmonic in the drill? Does this effect core quality? Can the oscillation be mitigated? Or could the drill be tuned to minimize cutting power by harnessing the momentum created with the ice fractures?
- I would like to see the effect of ice properties explored against the cutting force. We know that the ice properties change significantly with grain size and temperature (Petrovic, J.J., 2003) but this was not included in the study, although a robust drill design must work in a variety of conditions.
- The range of rake angle was from 20° to 40°, which doesn’t even include the range of existing drills. Plots, such as Figure 10, indicated that the cutting force will continue to decrease with increasing rake angle. I would have liked to see that explored, at least until a physical limit was approached (e.g. the rake angle intersected with the relief angle). Then future designers could pursue better blade design and weight it against durability.
- Same with depth of cut – it would be useful continue the trend to a maximum or asymptote.
Overall, I would like to see the paper discuss a novel finding. The range of variables could be expanded, so the data enters new territory that has not already been proven with drills in operation. Alternatively, a discovery such as the force oscillation could be the focus. To my knowledge, this is a new finding that has not been published in connection with ice drilling.
Petrovic, J.J., 2003. Review mechanical properties of ice and snow. Journal of materials science, 38, pp.1-6.
Citation: https://doi.org/10.5194/egusphere-2023-2985-RC1 - AC2: 'Reply on RC1', Rusheng Wang, 04 Apr 2024
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RC2: 'Comment on egusphere-2023-2985', Anonymous Referee #2, 13 Mar 2024
This paper investigates a few basic variables that influence ice cutting force, but the experiment lacks focus to develop a novel understanding of ice cutting mechanics. Differences in ice properties are briefly mentioned in the introduction, but not discussed further in the context of study. The range of experimental parameters was limited and is not representative of typical ice coring equipment deployed in polar regions. Evidence for brittle fracture is shown with the high-speed camera for one set of parameters, but there is no discussion on how cutting depth or rake angle could influence failure mode.
Specific comments follow:
- How were the cutters sharpened for this study? Was the rake surface polished? I expect cutter sharpness and rake surface finish to impact cutting performance and cutting force.
- I would like to see a wider range of rake angles investigated that include existing drills. Negative rake angles are not discussed in this paper but could provide an interesting comparison.
- I would like to see a more detailed analysis of how the ice fracture mechanics change with depth of cut. High speed imagery is only provided for one set of parameters. At a minimum, I would like to see a comparison of imagery between different depths of cut.
- The force diagrams in Figure 7. does not account for the presence of a cutter shoe which limits depth of cut. During cutting, I expect Fp to shrink to zero once the shoes are fully contacting the bottom of the borehole behind the cutter.
- I would like to see a comparison of the cutting force trace (Figure 9) for different depths of cut. It would be interesting to compare the resulting frequency as chip size changes.
I would like to see this study revisited to focus on developing a novel understanding of ice cutting mechanics. Focusing on force oscillation or how cutting mechanics vary with depth of cut could yield a novel finding.
Citation: https://doi.org/10.5194/egusphere-2023-2985-RC2 - AC1: 'Reply on RC2', Rusheng Wang, 04 Apr 2024
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