The National Academies Press

Currently Skimming:

Pages 110-136

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.

From page 110... ... Because the aggregate foam material has a closed-cell microstructure, it has an inherent resistance to moisture. However, the presence of water during freeze–thaw cycling could present a more aggressive erosion hazard for the material. Read the entire page →
From page 111... ... Aggregate foam arrestor concept. Aggregate Foam Bed Cover Layer of Engineered Turf Arrestor Basin Read the entire page →
From page 112... ... Metamodeling Build Combined Tire/Arrestor Models (LS-DYNA) Batch Simulations for Tire/Arrestor Combinations (LS-OPT) Read the entire page →
From page 113... ... • Effects of confining pressure on strength • Per ASTM D2850 • 6 x 10.5" cylinder • Reduced aggregate size • Pieces graded for 0.4" to 1.0" 0.24%/min compression rate • Maximum compression of 15 to 25% • Confining pressures of 5, 10, 20, 60, and 100 psi 5 psi 10 psi 20 psi 60 psi 100 psi Total: 1 2 2 2 2 9 • Version 1: Original Aggregate Size • Non-standard • Pieces graded for 0.4" to 2.4" • 12.375 x 9.5" confining cylinder • 3 in./min compression rate • Maximum compression of 75% 2 Confined Cylinder Compression Test • Compressive strength (σu) • Compressive stress– strain curve • Extrapolated: volumetric energy capacity • Version 2: Reduced Aggregate Size • Non-standard • Pieces graded for 0.4" to 1.0" • 12.375 x 7.5" confining cylinder • 3 in./min compression rate • Maximum compression of 45% Fresh Conditioned 1 2 • Version 1: Per ATSM C 666/C 666M03 (modified) Read the entire page →
From page 114... ... Confined cylinder test average load histories for aggregate foam material. Compressive Strain (in./in.) Read the entire page →
From page 115... ... Because the hydrostatic specimen data had more scatter than the confined cylinder data, a total of nine tests were conducted. Figure 11-10 compares the hydrostatic triaxial data for the three main material candidates: glass foam block, aggregate glass foam, and hard engineered aggregate. Read the entire page →
From page 116... ... Compressive Stress, p (psi) Glass Foam Block Aggregate Foam - Late Stage Hard Aggregate Trend - Glass Foam Block Trend - Aggregate Foam Early Stage Trend - Aggregate Foam Late Stage Trend - Hard Aggregate Read the entire page →
From page 117... ... 11.3.4. Pendulum Tests The pendulum tests that were conducted for the other candidate arrestor concepts were omitted for the aggregate foam material. Read the entire page →
From page 118... ... . Using this material model, an arrestor bed model was constructed and coupled with tire models for the different aircraft (Figure 11-5, block 4) Read the entire page →
From page 119... ... 11.4.2. Smoothed Particle Hydrodynamics Formulation The aggregate foam arrestor models were developed in LSDYNA, a general-purpose finite element modeling code. Read the entire page →
From page 120... ... As Figure 11-17 shows, the compressed material area extended all the way to the bottom of the arrestor bed, which was in con120 Figure 11-15. confined cylinder model for aggregate foam material calibration. Read the entire page →
From page 121... ... This approach enabled various depths to be rapidly configured within a single arrestor bed model. 121 Arrestor and Tire Model Uses HalfSymmetry Small Pieces of Aggregate Foam Fragment Off of Bed Material Compressed by Tire Tire Penetrates Vertically to a Prescribed Depth Deformable Finite Element Aircraft Tire Model SPH Arrestor Bed Figure 11-16. Read the entire page →
From page 122... ... Adjustable height of aggregate foam arrestor bed. Aircraft Landing Gear Tire Designation Main Gear H29x9.0-15 CRJ-200 Nose Gear R18x4.4 Main Gear H44.5x16.5-21 B737-800 Nose Gear H27x7.7-15 Main Gear H49x19-22 B747-400 Nose Gear H49x19-22 Table 11-4. Read the entire page →
From page 123... ... Bed Depth Bottoming Depth Rut DepthPenetration Depth Tire Deflection Figure 11-20. Depth definitions for aggregate foam bed models. Read the entire page →
From page 124... ... 124 Tire SimulationsConducted Points Used Response RMS Error R 2 Drag 7.10% 0.995 H49 50 50 Vertical 5.96% 0.994 Drag 3.57% 0.999 H44 60 58 Vertical 3.05% 0.998 Drag 16.70% 0.971 H29 60 47 Vertical 7.70% 0.986 Drag 3.39% 0.998 R27 40 40 Vertical 3.78% 0.997 Drag 23.80% 0.948 H18 80 73 Vertical 21.40% 0.943 Table 11-5. Metamodel accuracy summary for aggregate foam arrestor bed. Read the entire page →
From page 125... ... deep aggregate foam arrestor bed. Stronger drag loads (shown as the lower, more negative values) Read the entire page →
From page 126... ... Individual aircraft 70-knot arrestor beds for aggregate foam arrestor system. Nose-Gear Ultimate Load Criterion Bed Dimensions Bed Depth: 36.0 in. Read the entire page →
From page 127... ... For the two other candidate systems, a 50-ft decline distance was sufficient to produce stable arrestors. However, it was found that a 100-ft decline was considerably more stable for the aggregate foam concept due to its relative size with respect to the aircraft wheelbase. Read the entire page →
From page 128... ... Landing Gear Forces - NOSE STRUT Nose Gear Drag Nose Gear Limit Load Nose Gear Ultimate Load Figure 11-22. Limit criterion aggregate foam arrestor design plots for B737-800 showing speed (top) Read the entire page →
From page 129... ... Landing Gear Forces - NOSE STRUT Nose Gear Drag Nose Gear Limit Load Nose Gear Ultimate Load Figure 11-23. Ultimate criterion aggregate foam arrestor design plots for B737-800 showing speed (top) Read the entire page →
From page 130... ... Limit criterion aggregate foam arrestor design plots for B737-800 showing axle and rut depth for the main strut (top) and nose strut (bottom) Read the entire page →
From page 131... ... Landing Gear Forces - NOSE STRUT Figure 11-25. Limit criterion aggregate foam arrestor -- 50-ft ramp -- design plots for B737-800 showing speed (top) Read the entire page →
From page 132... ... . First, the aggregate foam arrestor exhibits a depth-varying strength property that is advantageous for arresting varied aircraft fleets. Read the entire page →
From page 133... ... The site preparation costs were estimated for two cases. The aggregate foam arrestor would use a basin for the arresting materials rather than a flat runway-type surface as is used for the current EMAS design. Read the entire page →
From page 134... ... Many industrial applications of glass foam materials indicate long service life is possible with little degradation, as long as mild protective measures are taken. However, the aggregate foam carries some maintenance issues not present for solid foam block material. Read the entire page →
From page 135... ... 11.8. Summary The aggregate foam arrestor concept was found to have a mechanical response similar to a crushable foam material, except with depth-varying properties. Read the entire page →
From page 136... ... arrestor bed demonstrated 70+ knot exit speeds for the B737400 and CRJ-200 and a 56-knot exit speed for the B747. The reason for the superior performance appears to be the depthvarying nature of the material. Read the entire page →

From page 110...

... Because the aggregate foam material has a closed-cell microstructure, it has an inherent resistance to moisture. However, the presence of water during freeze–thaw cycling could present a more aggressive erosion hazard for the material.