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OCR for page 111
111
Figure 11-1. Aggregate foam material: pile of aggregate (left) and close-up of microstructure (right) (43).
which was sufficient for a concept-level evaluation. The sub-
sequent modeling approach for the aggregate foam material
was comprehensive in nature, and the outcome was a cali-
brated numerical model for predicting arrestment loads.
The testing and modeling approach for the aggregate foam
concept is illustrated by Figure 11-5. Five major stages are
illustrated by the larger process bubbles of the chart:
1. Arrestor Material Testing and Modeling. Laboratory
testing generated test data, and computer models of the
material were calibrated to match it.
2. Tire Modeling. Aircraft tire models for the three test air-
craft were built and calibrated to match manufacturer
performance specifications.
3. Aircraft Modeling. A generalized aircraft model was devel-
Figure 11-2. Typical aggregate foam fragments. oped to predict the suspension response of the plane and
its deceleration during a ground roll. This model was then
· Effect of aggregate size,
incorporated into an APC for determining stopping dis-
· Rate dependence of the material, and
tances and landing gear loads when an aircraft is driven
· Durability to freezethaw exposure.
through an arrestor bed. A library of aircraft definitions
was created to represent the three test aircraft.
4. Metamodeling. The arrestor material and tire models were
11.2. Testing and combined to produce an overrun model for determin-
Modeling Approach ing the loads exerted on the different aircraft tires by the
arrestor bed. Large data sets were generated using simula-
11.2.1. Overview
tion batches for each tire and arrestor combination. These
The goal for the performance evaluation was to undertake data sets were then accessible by the arrestor prediction
testing that would allow calibration of high-accuracy com- code (next step).
puter models of the aggregate foam concept. The testing 5. Performance Predictions. The preceding four develop-
approach evaluated several characteristics of the material, ment stages culminated in the final, bottom-most process
Cover Layer of Engineered Turf
Aggregate Foam Bed
Arrestor Basin
Figure 11-3. Aggregate foam arrestor concept.
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Drainage Approach Waterproof Approach on the figure. The APC was used to predict arresting dis-
tances, landing gear loads, and ideal arrestor bed designs
for the different aircraft.
The subsequent sections of this chapter will focus on areas
(1), (4), and (5). Special attention will be given to the aggregate
Layers of Plastic Keep
Precipitation Drains
Aggregate Dry foam material testing that was conducted and the calibration
Through Bed
of the computer models to match the tests. The development
Figure 11-4. Aggregate bed methods for of the tire models (2) and aircraft model (3) will be reserved for
handling precipitation and drainage. Appendix F and Appendix G, respectively.
(1) Arrestor Material (2) Tire Modeling (3) Aircraft Modeling
Testing/Modeling
Conduct Material Manufacturer Tire Manufacturer Aircraft
Tests Data Data
Build Tire Model Develop Estimated
Test Data
(LS-DYNA) Aircraft Parameters
Build Models Calibrate Tire Model
Replicating Tests to Match Data Aircraft Library
(LS-DYNA) (LS-OPT)
Calibrate Model to Develop Arrestor
Match Test Data Final Tire Models Prediction Code
(LS-OPT) (APC) (MATLAB)
Final Material Model
(4) Metamodeling
Build Combined
Tire/Arrestor Models
(LS-DYNA)
Batch Simulations for
Tire/Arrestor Combinations
(LS-OPT)
Metamodel Data
(5) Performance Predictions
Predict Arresting Performance for
Test Aircraft (APC/MATLAB)
Figure 11-5. Testing and modeling process for aggregate foam arrestor
evaluation.
