1 Extension of Terrestrial Excavation Mechanics to Lunar Soil Jason R. Florek, M.S. Rutgers...
-
date post
19-Dec-2015 -
Category
Documents
-
view
213 -
download
0
Transcript of 1 Extension of Terrestrial Excavation Mechanics to Lunar Soil Jason R. Florek, M.S. Rutgers...
1
Extension of Terrestrial Extension of Terrestrial Excavation Mechanics Excavation Mechanics to Lunar Soilto Lunar Soil
Jason R. Florek, M.S.Rutgers UniversityDepartment of Mechanical and Aerospace EngineeringJune 5, 2007
2J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
MotivationMotivation
Nearly all lunar base designs call for some form of regolith shielding.
Moving regolith also necessary for paving roads and collecting natural resources.
Digging and excavating forces must be well understood for first generation design.
Forces directly related to required power and size, weight and cost of equipment.
3J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Design of EquipmentDesign of Equipment
Grader with extended frame
Combination grader blade Smooth roller
Hemispherical dome wheel
All from Banks et al. (1990).
4J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Modeling Required Modeling Required Cutting ForcesCutting Forces Analytical Models
Two-Dimensional Three-Dimensional Static Dynamic
Finite Element Models Empirical Models
5J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Experiments on Experiments on Lunar Soil SimulantsLunar Soil Simulants
W. W. Boles, W. D. Scott, and J. F. Connolly, Excavation forces in reduced gravity environment. J. Aerospace Engng. 10(2) 99-103 (1997).
Scaled experiment aboard KC 135 aircraft to predict force to fail JSC-1 simulant .
Required force in reduced gravity did not scale by factor of 1/6.
Proposed using results at 1/6 g and 1 g as lower and upper bounds of force.
6J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Experiments on Experiments on Lunar Soil SimulantsLunar Soil Simulants
B. M. Willman and W. W. Boles, Soil-tool interaction theories as they apply to lunar soil simulant. J. Aerospace Engng. 8(2) 88-99 (1995).
Measured average required drawbar forces: 192 N, 522 N and 825 N, respectively.
Values compared to four predictive models. One model: 627 N, 1157 N and 1639 N. Average of other models: 35 N, 112 N, 187 N. All predictive models rejected. Not all necessary parameters provided.
7J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Cutting and Excavating Cutting and Excavating the Lunar Soilthe Lunar Soil
A. Wilkinson and A. DeGennaro, Digging and pushing lunar regolith: Classical soil mechnaics and the forces needed for excavation and traction. J. Terramech. 44(2) 133-152 (2007).
S. Blouin, A. Hemami, and M. Lipsett, Review of resistive force models for earthmoving processes. J. Aerospace Engng. 14(3) 102-111 (2001).
Numerous models for needed digging (drawbar) forces, each with varying complexities.
Authors hold back recommendation until after experimental validation.
Reducing failure plane angle to between 10.4-11.5 deg. creates a match between Gill model and Willman experimental data.
8J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Logarithmic Spiral Logarithmic Spiral Failure PlaneFailure Plane
Locate spiral center.
Moment balance about center.
d2 most difficult distance to calculate.
Minimize pushing forces.
Failure model of Osman (1964).
9J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Cutting ParametersCutting Parameters
Depth Cohesion Surcharge Adhesion
From Blouin et al. (2001).
Fundamental earthmoving equation from Reece (1964).
From Luengo et al. (1998).
10J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Parameter NotationsParameter Notations
[5]-Willman & Boles (1995), [7]-Wilkinson & DeGennaro (2007), [11]-Luengo et al. (1998), [13]-Osman (1964)
11J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Horizontal Force vs. Horizontal Force vs. Tool DepthTool Depth
Depth and tool-soil terms most important. Cutting force in Gill Model arbitrary.
12J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Horizontal Force vs. Horizontal Force vs. Rake AngleRake Angle
Depth and tool-soil terms most important. Negative tool-soil contribution possible for
Swick model.
13J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Horizontal Force vs. Horizontal Force vs. GravityGravity
Depth and tool-soil terms most important for Gill Model.
Only depth term important for Swick model.
14J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Horizontal Force vs. Horizontal Force vs. Cohesion & Internal Cohesion & Internal FrictionFriction
Depth and tool-soil terms most important when changing friction angle.
Cohesion only important for high values.
15J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Horizontal Force vs. Horizontal Force vs. Density & SurchargeDensity & Surcharge
Depth and tool-soil terms most important. Surcharge, cohesion and kinetic terms can in
most cases be neglected.
16J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Depth vs. Soil Depth vs. Soil Density vs. Density vs. Cohesion vs. Cohesion vs. Friction AngleFriction Angle
17J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Parameter Parameter DependenciesDependencies
Failure plane angle is a function of all other angles—rake angle and two friction angles.
Cohesion, friction angles and density are all related to soil depth.
Major problem in determining values for input to equations.
18J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Depth-Varying DensityDepth-Varying Density
Assumed constant density of 1.68 g/cm3 [7]. First model matches density at 9 cm. Second model matches density at 30 cm.
19J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
Effect of Density Effect of Density Change with DepthChange with Depth
Assumed constant density of 1.68 g/cm3 (Wilkinson). First model matches density at 9 cm. Second model matches density at 30 cm.
20J. R. Florek. Extension of Terrestrial Excavation Mechanics to Lunar Soil. 6/5/07.
ConclusionsConclusions
Required forces do not scale by 1/6 in reduced gravity.
Although some Earth based models correlate poorly with experimental results, others compare surprisingly well.
Depth and tool-soil terms appear to be most important.
Parameter dependencies should be accounted for in model.