查看更多>>摘要：In the process of launching guided projectile under the conventional system,it is difficult to effectively obtain the precise navigation parameters of the projectile in the high dynamic environment.Aiming at this problem,this paper describes a new system of guided ammunition based on tail spin reduction.After analyzing the mechanism of the ammunition's tail spin reduction,a navigation method of large scale difference tail control simple guided ammunition based on speed constraint is proposed.In this method,the corresponding navigation constraints can be carried out by combining the rotation speed state of the ammunition itself,and the optimal solution of navigation parameters during the flight of the missile can be obtained by Extended Kalman Filter(EKF).Finally,the performance of the proposed method was verified by the simulation environment,and the hardware-in-the-loop simulation test and flight test were carried out to verify the performance of the method in the real environment.The experimental results show that the proposed method can achieve the optimal estimation of navigation parameters for simple guided ammunition with large-scale difference tail control.Under the conditions of simulation test and hardware-in-loop simulation test,the position and velocity errors calculated by the method in this paper converged.Under the condition of flight test,the spatial average error calculated by the method described in this paper is 6.17 m,and the spatial error of the final landing point is 3.50 m.Through this method,the accurate acquisition of navigation parameters in the process of projectile launching is effectively realized.
查看更多>>摘要：Investigating natural-inspired applications is a perennially appealing subject for scientists.The current increase in the speed of natural-origin structure growth may be linked to their superior mechanical properties and environmental resilience.Biological composite structures with helicoidal schemes and designs have remarkable capacities to absorb impact energy and withstand damage.However,there is a dearth of extensive study on the influence of fiber redirection and reorientation inside the matrix of a helicoid structure on its mechanical performance and reactivity.The present study aimed to explore the static and transient responses of a bio-inspired helicoid laminated composite(B-iHLC)shell under the influence of an explosive load using an isomorphic method.The structural integrity of the shell is maintained by a viscoelastic basis known as the Pasternak foundation,which encompasses two co-efficients of stiffness and one coefficient of damping.The equilibrium equations governing shell dy-namics are obtained by using Hamilton's principle and including the modified first-order shear theory,therefore obviating the need to employ a shear correction factor.The paper's model and approach are validated by doing numerical comparisons with respected publications.The findings of this study may be used in the construction of military and civilian infrastructure in situations when the structure is sub-jected to severe stresses that might potentially result in catastrophic collapse.The findings of this paper serve as the foundation for several other issues,including geometric optimization and the dynamic response of similar mechanical structures.
查看更多>>摘要：In this study,austenitic stainless steel(ASS)was additively fabricated by an arc-based direct energy deposition(DED)technique.Macrostructure,microstructure,mechanical characteristics at different spatial orientations(0°,90°,and 45°),and wear characteristics were evaluated at the deposited structure top,middle,and bottom regions.Results show that austenite(γ)and delta-ferrite(δ)phases make up most of the microstructure of additively fabricated SS316LSi steel.Within γ matrix,8 phase is dispersed both(within and along)grain boundaries,exhibiting a fine vermicular morphology.The bottom,middle,and top regions of WAAM deposited ASS exhibit similar values to those of wrought SS316L in the tensile and impact test findings.Notably,a drop in hardness values is observed as build height increases.During SEM examinations of fractured surfaces from tensile specimen,closed dimples were observed,indicating good ductility of as-built structure.Wear test findings show signs of mild oxidation and usual adhesive wear.By depositing a mechanically mixed composite layer,an increase in the oxidation percentage was discovered to facilitate healing of worn surfaces.The findings of this study will help in design,production and renovation of products/components that are prone to wear.WAAM-deposited ASS has remarkable strength and ability to withstand impacts;it can be used in the production of armour plates for defence applications,mainly military vehicles and aircraft.
查看更多>>摘要：As a kind of high-efficiency explosive with compound destructive capability,the energy output law of thermobaric explosives has been receiving great attention.In order to investigate the effects of main components on the explosive characteristics of thermobaric explosives,various high explosives and oxidants were selected to formulate five different types of thermobaric explosive.Then they were tested in both open space and closed space respectively.Pressure measurement system,high-speed camera,infrared thermal imager and multispectral temperature measurement system were used for pressure,temperature and fireball recording.The effects of different components on the explosive characteristics of thermobaric explosive were analyzed.The results showed that in open space,the overpressure is dominated by the high explosives content in the formulation.The addition of the oxidants will decrease the explosion overpressure but will increase the duration and overall brightness of the fireball.While in closed space,the quasi-static pressure formed after the explosion is positively correlated with the temperature and gas production.In addition,it was found that the differences in shell constraints can also alter the afterburning reaction of thermobaric explosives,thus affecting their energy output char-acteristics.PVC shell constraint obviously increases the overpressure and makes the fireball bum more violently.
查看更多>>摘要：The search for new green and efficient stabilizers is of great importance for the stabilization of nitro-cellulose(NC).This is due to the shortcomings of traditional stabilizers,such as high toxicity.In this study,reduced polyaniline(r-PANI),which has a similar functional structure to diphenylamine(DPA)but is non-toxic,was prepared from PANI based on the action with N2H4 and NH3-H2O,and used for the first time as a potential stabilizer for NC.XPS,FTIR,Raman,and SEM were used to characterize the reduced chemical structure and surface morphology of r-PANI.In addition,the effect of r-PANI on the stabilization of NC was characterized using DSC,VST,isothermal TG,and MMC.Thermal weight loss was reduced by 83％and 68％and gas pressure release by 75％and 49％compared to pure NC and NC&3％DPA,respectively.FTIR and XPS were used to characterize the structural changes of r-PANI before and after reaction with NO2.The 1535 cm-1 and 1341 cm-1 of the FTIR and the 404.98 eV and 406.05 eV of the XPS showed that the-NO2 was generated by the absorption of NO2.Furthermore,the quantum chemical calculation showed that NO2 was directly immobilized on r-PANI by forming-NO2 in the neighboring position of the benzene ring.
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