Aircraft Landing Gear Dynamic Loads Induced by Soil Landing Fields. Volume II. Soil Tests and Soil Response Studies.

摘要

This report contains the results of the construction and maintenance of the buckshot clay test bed used for tandem and single wheel high speed landing gear tests conducted at the NASA Langley Landing Loads Track. The test bed was constructed to a CBR strength of 2.7, moisture content of 32.5 percent, dry density of 86.0 pcf, degree of saturation of 91.7 percent, and airfield penetration resistance of 1.7 to 1.8. Analysis of dynamic soil behavior indicated that wave propagation velocities in the soil and soil inertia effects become significant at forward velocities greater than 60 knots. Strain-rate effects are significant at all velocities for buckshot clay and cause 50 to 60 percent increases of shear strength at a forward velocity of 50 knots. Strain-rate effects on sand are insignificant except when pore pressures are developed. The wheel will 'outrun' the bow wave or shear wave propagating ahead of the wheel at forward velocities greater than the 150 to 250 knot range.