The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB2 and B4C ceramic reinforcement particles. Surface composites with different weight fractions of TiB2 and B4C particles...The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB2 and B4C ceramic reinforcement particles. Surface composites with different weight fractions of TiB2 and B4C particles were processed by friction stir processing. Micro-hardness and depth of penetration tests were carried out to evaluate the ballistic properties of the surface composites. The surface hardness of the composite was found to be nearly 70 HV higher than base alloy. The depth of penetration of the steel projectile was 20e26mm in the composites as compared to 37mm in the base alloy. Ballistic mass efficiency factor of the surface composite was found to be 1.6 times higher than base alloy. This is mainly attributed to the dispersion strengthening from the reinforcement particles.展开更多
Tactical Ballistic Missile(TBM) class target neutralization by the fragment spray of a Fragment Generator Warhead(FGW) calls for quantification of fragment projection angle scatter to finalize the end game engagement ...Tactical Ballistic Missile(TBM) class target neutralization by the fragment spray of a Fragment Generator Warhead(FGW) calls for quantification of fragment projection angle scatter to finalize the end game engagement logic.For conventional axi-symmetric warhead,dispersion is assumed to be normal with a standard deviation of 3~O.However,such information is not available in case of FGW.Hence,a set of experiments are conducted to determine the dispersion of fragments.The experiments are conducted with a specific configuration of FGW in an identical arena to quantify the scatter and then verified its applicability to other configurations having a range of L/D and C/M ratios,and contoured fragmenting discs.From the experimental study,it is concluded that the scatter in projection angle follows normal distribution with a standard deviation of 0.75° at Chi-square significance level of 0.01(x_(0.99)~2).展开更多
La_2 O_3 doped(Na0.495 K0.455 Li0.05)(Nb0.95 Ta0.05)O_3 ceramics are prepared using modified milling process, and the influences of La2 O3 on ferroelectric behaviour, ageing characteristics, thermal stability, electri...La_2 O_3 doped(Na0.495 K0.455 Li0.05)(Nb0.95 Ta0.05)O_3 ceramics are prepared using modified milling process, and the influences of La2 O3 on ferroelectric behaviour, ageing characteristics, thermal stability, electrical stability, crystal structure, microstructure, dielectric and piezoelectric properties were reported. La_2 O_3 addition improved the ferroelectric characteristic substantially, and obtained remnant polarization(Pr) and maximum strain(Smax) around 34.3 C/cm^2 and 0.13% respectively.La_2 O_3 doped ceramics improved the thermal stability and were stable up to 180 ℃ compared to undoped ceramics(120 ℃). The Rietveld refinement along with the high-temperature X-ray diffraction studies suggested the presence of monoclinic phase in La doped compositions, which is responsible for their idiosyncratic behaviour. The maximum values were obtained around 179 pC/N and 0.385 for piezoelectric constant(d33) and electromechanical coupling factor(kp) respectively in La_2 O_3 doped samples(0.02 wt%), which also exhibited the lowest ageing rate and stable electrical fatigue behaviour.展开更多
基金supported by Defence Institute of Advanced Technology(DIAT),Pune(DIAT-In house Project)
文摘The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB2 and B4C ceramic reinforcement particles. Surface composites with different weight fractions of TiB2 and B4C particles were processed by friction stir processing. Micro-hardness and depth of penetration tests were carried out to evaluate the ballistic properties of the surface composites. The surface hardness of the composite was found to be nearly 70 HV higher than base alloy. The depth of penetration of the steel projectile was 20e26mm in the composites as compared to 37mm in the base alloy. Ballistic mass efficiency factor of the surface composite was found to be 1.6 times higher than base alloy. This is mainly attributed to the dispersion strengthening from the reinforcement particles.
文摘Tactical Ballistic Missile(TBM) class target neutralization by the fragment spray of a Fragment Generator Warhead(FGW) calls for quantification of fragment projection angle scatter to finalize the end game engagement logic.For conventional axi-symmetric warhead,dispersion is assumed to be normal with a standard deviation of 3~O.However,such information is not available in case of FGW.Hence,a set of experiments are conducted to determine the dispersion of fragments.The experiments are conducted with a specific configuration of FGW in an identical arena to quantify the scatter and then verified its applicability to other configurations having a range of L/D and C/M ratios,and contoured fragmenting discs.From the experimental study,it is concluded that the scatter in projection angle follows normal distribution with a standard deviation of 0.75° at Chi-square significance level of 0.01(x_(0.99)~2).
文摘La_2 O_3 doped(Na0.495 K0.455 Li0.05)(Nb0.95 Ta0.05)O_3 ceramics are prepared using modified milling process, and the influences of La2 O3 on ferroelectric behaviour, ageing characteristics, thermal stability, electrical stability, crystal structure, microstructure, dielectric and piezoelectric properties were reported. La_2 O_3 addition improved the ferroelectric characteristic substantially, and obtained remnant polarization(Pr) and maximum strain(Smax) around 34.3 C/cm^2 and 0.13% respectively.La_2 O_3 doped ceramics improved the thermal stability and were stable up to 180 ℃ compared to undoped ceramics(120 ℃). The Rietveld refinement along with the high-temperature X-ray diffraction studies suggested the presence of monoclinic phase in La doped compositions, which is responsible for their idiosyncratic behaviour. The maximum values were obtained around 179 pC/N and 0.385 for piezoelectric constant(d33) and electromechanical coupling factor(kp) respectively in La_2 O_3 doped samples(0.02 wt%), which also exhibited the lowest ageing rate and stable electrical fatigue behaviour.
