Different modeling technologies of hydraulic load simulator for thrust vector control actuator

Hidraulički simulatori su posebice važni u procesu verifikacije aktuacijskog sustava za kontrolu leta. Fleksibilni mlaznik ima niz specifičnosti u odnosu na druge komande leta, jer se opterećenje ne može opisati na klasičan način preko zglobnog momenta. Pored toga, klasičan hidraulički simulator, na bazi cilindra koji simulira opterećenje, nije dovoljan za potpunu simulaciju realnog opterećenja. Potrebno je napraviti mehaničko njihalo na koje deluje hidraulički cilindar i koje se oslanja na dva elastična oslonca kako bi se mogle simulirati i dopunske pojave koje postoje kod fleksibilnog mlaznika, a koji ne postoje kod drugih upravljačkih površina. Preko njihala se može zadati impulsna sila koja postoji u realnosti, a koju nije moguće generirati standardnim hidrauličkim simulatorom. U članku se pokazuje da se modeliranjem elastičnog opterećenja preko bond grafova simulator može projektirati bez preciznog razmatranja smjerova i pravaca sila u elastičnoj strukturi, već se samo energetski promatra unošenje sile u fleksibilnu strukturu preko mjesta djelovanja aktuacijske sile. Simulator s hidrauličkim cilindrom je pogodan u slučaju kad treba razmotriti rizik od vlastitih vibracija fleksibilne veze i mlaznika, to jest definirati takozvani notch filter. Tada hidraulički cilindar simulatora opterećenja može generirati oscilatorno gibanje, frekvenciju i amplitudu koje odgovaraju ovom dinamičkom slučaju opterećenja aktuatora fleksibilnog mlaznika koje je svedeno na njegovu klipnjaču, a da ne postoji rizik oštećenja fleksibilne strukture koja postoji u konstrukciji simulatora s njihalom.Hydraulic simulators are extremely important in the flight control actuator system’s verification process. Flexible nozzle has a number of specifics, comparing to other flight controls, because the load cannot be described, classically, by the hinge moment. Additionally, classical hydraulic simulator, in which the cylinder simulates the load, is not sufficient for performing a complete simulation of the real load. Building a mechanical pendulum, to which a hydraulic cylinder acts, and that rests on two elastic supports, enables simulation of additional phenomena that exist in flexible nozzle, but not in other control surfaces. Force from impulse that exists in reality, and which is impossible to be generated by standard hydraulic simulator, can be realized through the pendulum. This paper demonstrates that a simulator can be designed through modelling of the elastic load using bond graph, without a precise elaboration of direction of forces in elastic structure, just by observing, on energy level, the input of force in flexible structure over the point in which actuator force acts. Simulator with hydraulic cylinder is convenient to be used when there is a need for considering the risk of self-oscillation of flexible joint and nozzle, i.e. for defining the so-called notch filter. Then, the hydraulic cylinder of load simulator can generate the oscillation, frequency and amplitude that match this dynamic case of flexible nozzle actuator’s load that is being reduced to its piston rod, without a risk of damaging the flexible structure that exists in the construction of a simulator with pendulum

Nanoindentation study of nickel manganite ceramics obtained by a complex polymerization method

The chemical synthesis of nickel manganite powder was performed by a complex polymerization method (CPM). The obtained fine nanoscaled powders were uniaxially pressed and sintered at different temperatures: 1000-1200 degrees C for 2 h, and different atmospheres: air and oxygen. The highest density was obtained for the sample sintered at 1200 degrees C in oxygen atmosphere. The energy for direct band gap transition (Eg) calculated from the Tauc plot decreases from 1.51 to 1.40 eV with the increase of the sintering temperature. Indentation experiments were carried out using a three-sided pyramidal (Berkovich) diamond tip, and Young's modulus of elasticity and hardness of NTC (negative temperature coefficient) ceramics at various indentation depths were calculated. The highest hardness (0.754 GPa) and elastic modulus (16.888 GPa) are exhibited by the ceramics sintered at highest temperature in oxygen atmosphere