The effect of reactive plasticizer on viscoelastic and mechanical properties of solid rocket propellants based on different types of HTPB resin

Conventional plasticizers deteriorate mechanical and viscoelastic properties of the propellants due to their migration upon aging and long-term storage,which affects reliability and safety properties during exploitation.To address this issue,conventional plasticizer,dioctyl adipate(DOA),is replaced by reactive one,castor oil(CO).In addition,three different types of HTPB were used to obtain propellants with designed viscoelastic and mechanical properties.The CO increased propellants viscosity,without a significant impact on the propellant processability,regardless to the type of prepolymer.Conversely,mechanical properties were different depending on the type of resin,which were further analyzed by gel permeation chromatography(GPC).Addition of CO formed a denser polymer network and shifted T_(g) to higher values,compared to the compositions with DOA.The tensile strength of CO-containing propellants was lower at +20℃ and +50℃ compared to the reference compositions,while the strain at maximum load and strain at break were significantly increased with pronounced plastic deformation,especially for samples at -30℃.The inclusion of CO in the propellants composition gives more room for adjusting a wide range of mechanical properties.

Influence of FSW parameters on formation quality and mechanical properties of Al 2024-T351 butt welded joints

The influence of R/v ratio on joint quality in 2024-T351 aluminum alloy was studied. Specimens were subjected to friction stir welding with the rotation rates of 750, 950 and 1180 r/min and welding speed between 73 and 190 mm/min, providing R/v ratio between 5.00 and 10.27. The welded joints were tested by means of both non-destructive （visual, penetrant and X-ray inspection） and destructive （metallographic, tension and hardness） testing. In all specimens typical zones are revealed, with corresponding differences in grain size. Tensile efficiency of the joints obtained is in the range of 52.2%to 82.3%. The results show that the best quality is obtained at R/v ratio of 8.06, 10.17 and 10.27. This behavior is attributed to the assumption that the material flows around the pin with an optimal speed, i.e. sufficient amount of material is available to fill the gap and prevent tunnel formation. R/v ratio also showed influence on hardness distribution, onion features and crack initiation/propagation zones.

Deformation behaviour and microstructure evolution of AlMg6Mn alloy during shear spinning

Deformation behavior and microstructure of AlMg6Mn alloy subjected to shear spinning were studied by means of mechanical characterization, optical and SEM＋EDS microscopy. Specimens were shear spun on an industrial spinning machine using different mandrels, providing reductions of wall thickness of 30%, 50% and 68%. The grain structure developed during shear spinning refines gradually. The grains elongate in axial direction with increase of reduction, and also stretches along circumferencial direction. Optimal combination of strength and elongation is observed. This is attributed to grain refinement and dislocation reactions with particles and atoms of Mg and Mn in solid solution.

Development of dynamic-mathematical model of hydraulic excavator

This work deals with analysis of dynamic behaviour of hydraulic excavator on the basis of developed dynamic-mathematical model.The mathematical model with maximum five degrees of freedom is extended by new generalized coordinate which represents rotation around transversal main central axis of inertia of undercarriage.The excavator is described by a system of six nonlinear,nonhomogenous differential equations of the second kind.Numerical analysis of the differential equations has been done for BTH-600 hydraulic excavator with moving mechanism with pneumatic wheels.

Improvement of VIS and IR camouflage properties by impregnating cotton fabric with PVB/IF-WS_(2)

In order to examine the possibility to improve its camouflage properties standard cotton fabric with camouflage print was impregnated with poly(vinyl butyral),PVB and fullerene-like nanoparticles of tungsten disulfide,PVB/IF-WS_(2).FTIR analysis excluded any possible chemical interaction of IF-WS_(2) with PVB and the fabric.The camouflage behavior of the impregnated fabric has been examined firstly in the VIS part of the spectrum.Diffuse reflection,specular gloss and color coordinates were measured for three different shades(black,brown and dark green).Thermal imaging was applied to examine the camouflage abilities of this impregnation in IR part of the spectrum.The obtained results show that PVB/IF-WS_(2) impregnation system induced enhacement of the materials camouflage properties,i.e.that IF-WS_(2) have a positive effect on spectrophotometric characteristics of the fabric.

Quality Management of Aeronautical Surfaces Manufacturing

Wind tunnel testing is experimental support of research and development during the design phase of aircraft and missile projects. The paper presents the developed method of manufacturing management by providing the required quality and accuracy of the wind tunnel models. The price of the wind tunnel model is several hundred thousand dollars and for this reason a manufacturing defect is not allowed. Additionally, any delays in the production process cause delay of testing in the wind tunnel. The costs of the delay are very high, because the wind tunnel laboratory is extremely expensive. All the foregoing is why the issue of the model＇s production is very important. Manufacturing of wind tunnel model within the contracted deadline and the required quality define tasks and objectives of production process management： identification of critical machining operations and activities; minimizing the time of coordinate inspections between cutting operations; identifying the main parameters of quality （shape, position in space, and angular relations）; and material management for all other machining operations that follow. Specially developed methods of coordinate metrology are crucial for the management of the manufacturing process. Worldwide used specialized coordinate inspection programs have no option to measure the flaps deflection angles and wing dihedral angle. This paper introduces the originally developed coordinate inspection methods for determining the angular relations between lift and control surfaces. The methods presented in this paper have been confirmed in several international projects. The quality and accuracy of the models for wind tunnel testing are conditio sine qua non.

Diode Pumped High Peak Power Quasi Q-Switched and Passively Q-Switched Nd:YVO₄Lasers at 1064 nm and 532 nm using Cr:YAG and KTP crystals

Diode end-pumped solid-state lasers have the potential to yield high quality laser beams with high efficiency for laser range finding and warning receiver applications as well as day and night military laser designation systems. In this paper we presents theoretical calculations using Advanced Dynamics Professional LASCAD software and experimental studies for a high power pigtailed fiber diode laser module of 8 W operating at 808 nm with a specially designed high efficiency cooling system, end pumped high-efficiency Nd:YVO4 laser of 3 × 3 × 10 mm rod and overall cavity length of 44 mm. To the best of our knowledge a self Q-switching effects was generated in Nd:YVO4 laser by changing the cavity dimensions and the position of the intracavity KTP crystal at certain regime of operation for the first time, in which the cavity length is reduced to be 30 mm and the distance between Nd:YVO4 rod and KTP crystal is only 1mm. Self Q-switched laser pulse at 532 nm with high peak power of 96 W, pulse width of 88 ns at FWHM and repetition rate of 400 kHz was achieved. Experimental studies of a passive Q-switched Nd:YVO4 laser using Cr:YAG crystal with three different transmissions of 30%, 40% and 70% were investigated. Passive Q-switched laser pulse at 1064 nm and narrow line width of less than 1.5 nm with highest peak power of nearly 18 kW, short pulse width of less than 4 ns at FWHM and higher repetition rate of 45 kHz using Cr:YAG with transmission of 30% was achieved for the first time.

HB-2 high-velocity correlation model at high angles of attack in supersonic wind tunnel tests

Responding to a need for experimental data on a standard wind tunnel model at high angles of attack in the supersonic speed range, and in the absence of suitable reference data, a series of tests of two HB-2 standard models of different sizes was performed in the T-38 trisonic wind tunnel of Vojnotehnickˇi Institut(VTI), in the Mach number range 1.5–4.0, at angles of attack up to+30°. Tests were performed at relatively high Reynolds numbers of 2.2 millions to 4.5 millions(based on model forebody diameter). Results were compared with available low angle of attack data from other facilities, and, as a good agreement was found, it was assumed that, by implication, the obtained high angle of attack results were valid as well. Therefore, the results can be used as a reference database for the HB-2 model at high angles of attack in the supersonic speed range, which was not available before. The results are presented in comparison with available reference data, but also contain data for some Mach numbers not given in other publications.