The objective of this study was to analyze the results obtained from tests done by simulating the crash landing of a rotary wing unmanned air vehicle with a skid type landing gear. The experimental and computational methods were used in the simulation tests. In the rst portion of the test; namely with the experimental method, the impact loads induced by the simulated crash landing and the stresses, strains, deformations generated by these loads, were recorded by drop test apparatus. In the second portion of the test with the computational method, free falling of the skid type landing gear was modeled and crash landing test was simulated numerically by using ANSYS code. Experimental methods were applied on four skid landing gear specimens with dierent shapes. Each of the test samples used in the following test was evolved because each sample was developed and redesigned based on the feedback results obtained from the former test. The rst three test specimens were manufactured from 2024 T3, 7075 T6 and 6061 T6 aluminum alloys respectively and all of them were curved in Π-form with a solid cross section. The last and fourth specimen was also manufactured from 6061 T6 aluminum alloy and it was curved in a hollow semi-circle form (∩-form). It is concluded that the last and fourth developed specimen was the best in absorbing the impact energy and enduring the crash.
This study is mainly focused on the 3D mechanical cell deformations of 20 × 20 × 60 mm sized softwood specimens under 35-40 MPa compression loading at room temperature of 20˚C. The moisture content of the specimens was 6%-7%. The data of microscopic images were measured and compared in terms of the permanently degenerated individual cell structures each in micro-scale () μm. 3D cell deformations of tissues were observed with a magnification of (×100)-(×1500) and in the range of 3.0-5.0 kV voltage under the SEM microscope. The specimens were examined under magnification and photographed before and after the compression loading applied parallel to the grain angles to the wood samples. Specimens were painted with gold liquid (12 × 12 × 12 mm sized specimens) in obtaining the SEM images. Under the SEM, these specimens were photographed and lengths between the cell walls ranged between 15 to 40 micrometers. In this study, relative deformations of pinewood cells were determined statistically considering the percentage permanent deformation under the compression loading. It was performed by using knowledge of structural mechanics, considering the measurement of permanent deformation in honeycomb-pinewood structure material.
In this paper, thin rectangular steel plates with stiffeners are examined under compressive loading. Consequently, nonlinear buckling finite element analysis (FEA) solutions are obtained by using ANSYS®. The local and global buckling patterns of stiffened steel plate geometries with simply supported boundary conditions are generated and critical buckling stresses are studied. Geometrically nonlinear buckling analyses are compared in order to evaluate the distributions of compressive stresses versus in-plane contractions and compressive stresses versus out-of plane deflections. Hence, it is concluded that there are critical load intervals. It is also observed that for critical loads, segments between stiffeners may switch from stable to unstable configurations under compressive stresses.
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