3 research outputs found
Measurement of the direct damping derivative in roll of the two calibration missile models
U ovom radu opisano je merenje priguÅ”nog derivativa stabilnosti u valjanju u aerotunelu T- 38. Prikazani su rezultati dobijeni na dva kalibraciona modela: Basic Finner Model i Modified Basic Finner Model. UreÄaj za merenje derivativa stabilnosti je ureÄaj sa prinudnim oscilacijama modela i to sa primarnim oscilatornim kretanjem u ravni valjanja. Pobudni moment u valjanju meren je petokomponentnom aerovagom sa mernim trakama. Ova aerovaga je projektovana i izraÄena za dinamiÄka aerotunelska merenja. Amplitude i fazni stavovi pobudnog momenta odreÄeni su u frekventnom domenu primenom kros-korelacione metode. Rezultati dobijeni u aerotunelu T-38 uporeÄeni su sa objavljenim eksperimentalnim rezultatima dobijenim u Arnold Engineering Development Center-von Karman 4ft aerotunelu.Measurement of the direct damping derivative in roll in the T-38 wind tunnel is described in this paper. The T-38 wind tunnel data for the Basic Finner Model and Modified Basic Finner model are shown. The forced oscillation technique was used for these measurements. The roll apparatus for the stability derivatives measurement is a full-model forced oscillation apparatus with primary angular oscillation around a longitudinal axis of the model. The excitation moment in roll was measured with the five- component strain gauge balance. This balance was designed and built for the wind tunnel dynamic measurements. The amplitudes and phase shifts of the excitation moment were calculated in frequency domain by applying cross-correlation technique. The T-38 wind tunnel results are compared with published experimental results of the Arnold Engineering Development Center-von Karman 4ft wind tunnel
Analysis of the possibility of increasing sting stiffness in the T-38 wind tunnel
Aerotunelski model i deformacije držaÄa modela tokom eksperimenata u aerotunelu T-38 imaju znaÄajan utjecaj na toÄnost mjerenja. Radi dobivanja visoke toÄnosti mjerenja poželjno je da deformacije budu Å”to manje. MoguÄnost da se uporabom visokokvalitetnog Äelika za izradu držaÄa modela utjeÄe na razinu naprezanja i deformacija je iscrpljena time Å”to se u aerotunelu T-38 koriste visoko kvalitetni maraging Äelici. Na osnovu velikog broja provedenih eksperimenata utvrÄeno je da je postizanje manjih deformacija moguÄe poveÄanjem krutosti držaÄa modela. U ovom radu se razmatraju kombinacije razliÄitih materijala s maraging Äelikom koji je osnovni materijal za izradu držaÄa modela. Neophodno je odabrati kombinaciju materijala koja daje najveÄu zahtijevanu krutost i dopuÅ”tenu razinu naprezanja u kritiÄnim presjecima držaÄa modela.Wind tunnel model and sting deflections during experiment in the T-38 wind tunnel have a significant influence on the measurement quality. It is necessary to reduce deflections due to higher accuracy of measurements achievement. High quality stainless steel is already widely used in the T-38 wind tunnel so there is no possibility for further influence to sting stress and deflection level. Based on the great number of performed experiments it is established that sting deflection can be reduced by increasing the sting stiffness. In this paper different material combinations with maraging stainless steel, which is base material for sting manufacturing, are considered. It is necessary to select combination of materials which produces the biggest required stiffness and allowed level of stress in critical sections of the sting