Measurement of the direct damping derivative in roll of the two calibration missile models

U ovom radu opisano je merenje prigušnog derivativa stabilnosti u valjanju u aerotunelu T- 38. Prikazani su rezultati dobijeni na dva kalibraciona modela: Basic Finner Model i Modified Basic Finner Model. Uređaj za merenje derivativa stabilnosti je uređaj 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 izrađena za dinamička aerotunelska merenja. Amplitude i fazni stavovi pobudnog momenta određeni su u frekventnom domenu primenom kros-korelacione metode. Rezultati dobijeni u aerotunelu T-38 upoređeni 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 držača modela tokom eksperimenata u aerotunelu T-38 imaju značajan utjecaj na točnost mjerenja. Radi dobivanja visoke točnosti mjerenja poželjno je da deformacije budu što manje. Mogućnost da se uporabom visokokvalitetnog čelika za izradu držača modela utječe na razinu naprezanja i deformacija je iscrpljena time što se u aerotunelu T-38 koriste visoko kvalitetni maraging čelici. Na osnovu velikog broja provedenih eksperimenata utvrđeno je da je postizanje manjih deformacija moguće povećanjem krutosti držača modela. U ovom radu se razmatraju kombinacije različitih materijala s maraging čelikom koji je osnovni materijal za izradu držača modela. Neophodno je odabrati kombinaciju materijala koja daje najveću zahtijevanu krutost i dopuštenu razinu naprezanja u kritičnim presjecima držača 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