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Data and knowledge on ballistic performance of Inconel-718 (IN718) alloy is critical for evaluating the resistance of turbine blades against foreign object impacts in aeronautical and astronautical industries. Ballistic perforation experiments (impact velocity 480 m s−1 to 1340 m s−1) with TC4 spherical projectiles (5-mm-diameter) are conducted on IN718 target plates (2-mm-thick) in this work, along with high-speed photography. The IN718 plates show multiple deformation and failure modes (bulging, dishing, petaling and plugging). The ballistic limit velocity for the investigated projectile/target combination is 823 m s−1. Postmortem material characterizations (optical photography, scanned electron microscopy and energy dispersive spectrometry) are conducted on recovered projectiles and bullet hole inner walls, and the observations indicate adiabatic shearing, surface melting and abrasion of projectile material. A finite element model based on the Johnson–Cook constitutive model and failure criterion is established, and reproduces the ballistic experiments. Dimensionless analyses are conducted on the dimensions of postmortem projectiles and bullet holes, and the projectile residual velocity/mass. On the basis of experimental observations and theoretical analysis of the projectile dynamics, the whole perforation process is divided into three stages (the entering, cratering and plugging stages). A multi-stage analytical model on perforation is then developed considering the effects of cavity expansion, projectile deformation and abrasion, and can well predict the projectile dynamics during entering and cratering stages. • Ballistic impacts with TC4 projectiles are conducted on Inconel 718 superalloy plates. • Characterizations on recovered projectiles and targets show abundant deformation modes. • The established finite element model well reproduces the experimental observations. • The projectile abrasion is discussed and modeled based on experiments and simulations. • An iteration calculation model is established to describe the projectile dynamics. [ABSTRACT FROM AUTHOR]

Understanding ballistic behavior of structural materials is important for their applications in aeronautical and astronautical industries. We investigate perforation of 2-mm thick Inconel 718 superalloy plates by spherical stainless steel 304 projectiles with high-speed photography at impact velocities ranging from 548 m s−1 to 1360 m s−1. Postmortem target samples are characterized with optical metallography, scanning electron microscopy and electron backscatter diffraction as regards bullet hole morphology and deformation. Grain refinement and shear banding are the main microstructural deformation modes near the bullet holes. Shear dominated deformation and tension–shear dominated deformation of target material occur sequentially in bullet hole along the impact direction. The morphologies of bullet holes and postmortem projectiles are obtained from the experiments and simulations. The effect of projectile deformation on ballistic behavior of the target is investigated. On the basis of dimensional analysis, a quadratic relation is derived between the energy absorption ratio of target and the dimensionless postmortem projectile diameter, along with a phenomenological model that can well predict projectile residual velocities. • Ballistic impacts are conducted on nickel-based Inconel 718 superalloy plates. • Deformation mode transition of target material is observed from fracture morphology. • The energy absorption behavior of target for non-rigid perforation is investigated. • A predicting model of residual velocity for non-rigid perforation is derived. [ABSTRACT FROM AUTHOR]

Ballistic impact experiments are conducted on a CrMnFeCoNi high-entropy alloy (HEA) using spherical steel projectiles, to investigate the penetration behavior in a wide range of impact velocities (∼ 800 to 2300 m s−1). Penetration processes are captured by high-speed camera. Postmortem samples are characterized via three-dimensional laser scanning, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and microhardness tests. Both depth and diameter of impact crater show a nearly linear increase with increasing impact velocity. Penetration induces increased hardness; hardness is the same near the crater bottom and the sidewall, and the peak hardness (∼ 400 Hv 1.0) is independent of impact velocity. The penetration-induced hardening is caused by multiple deformation defects including dislocations, twins and kink bands (KBs). Quantitative analysis further reveals that KB boundaries have a 5–50° misorientation angle, and their density decreases with increasing misorientation angle. KB boundary density is higher near the crater bottom than near the crater sidewall, while this trend is inverse for twinning boundary density. A finite element method model based on measured static and dynamic mechanical properties reproduces experimental observations and is used for interpreting deformation mechanisms. [Display omitted] • Both crater depth and diameter increase linearly with increasing impact velocity. • More kink bands (KBs), but less twins are observed near crater bottom than near sidewall. • KB boundary density decreases with increasing boundary misorientation from 0 to 50°. • Simulation interprets well the different deformation mechanisms in different regions. [ABSTRACT FROM AUTHOR]

Ballistic impact experiments are conducted on a cast Mg-6Gd-3Y-0.5Zr alloy using spherical projectiles under a wide range of impact velocities. Penetration processes are captured by high-speed camera. Postmortem target samples are characterized via three-dimensional laser scanning, metallographic microscopy, scanning electron microscopy and electron backscatter diffraction. Shear bands and twinning dominate the deformation of Mg-6Gd-3Y-0.5Zr near the crater, and texture changes due to compression caused by cavity expansion. For instance, a finite element model based on Johnson–Cook constitutive model and Mie–Grüneisen equation of state is established. Four dimensionless quantities related to craters and projectiles are defined. An analytical model based on dynamic cylindrical cavity expansion model is applied considering projectile deformation, and consistent well with experimental and simulated results over the entire incident velocity range. [Display omitted] • Ballistic impact experiments are conducted on cast Mg-6Gd-3Y-0.5Zr alloy. • Shear bands and twins dominate deformation of Mg-6Gd-3Y-0.5Zr near the crater. • Finite element model is established and consistent with experimental results. • A cylindrical cavity expansion model is derived considering projectile deformation. [ABSTRACT FROM AUTHOR]

This paper investigates a novel structure for the Winograd number theoretic transform algorithm (WNTA) to reduce the computation load. The proposed computing structure exploits the multiple constant multiplication to replace the standard multiplication, then, the multiplication of the WNTA can be realised in a shift-add way, which definitely decreases the complexity of WNTA and maintains the computing accuracy. Typical applications, such as the convolution and the filtering operation, are tested by computer simulations, while the result demonstrates that the proposed scheme is superior to conventional schemes in terms of the trade-off between the complexity. [ABSTRACT FROM AUTHOR]

SUMMARY Representing the channel varying rate and the mobile speed of a mobile terminal directly, Doppler shift is an important parameter in vehicular mobile communications and therefore is widely used in mobile target detection and adaptive applications. Hence, this paper puts forward an accurate Doppler shift estimator in mobile communications with high vehicle speeds, which can also be treated as a vehicular speed estimator due to the well-known relation between the Doppler shift and the mobile speed. Specifically, the proposed estimator is based on the channel level crossing rate, and an iterative process is presented to achieve signal-to-noise ratio (SNR) insensitive estimates in accordance with the level crossing rate estimation error analysis. Moreover, we prove the convergency of the iterative Doppler shift estimator in theory. Computer simulations conducted under a wide range of noise corruption clearly show that the proposed estimator substantially outperforms several existing estimators in terms of accuracy and achieves a good SNR-insensitive performance in a wide range of velocities and SNRs. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The effects of strain rate on mechanical properties, microstructural evolution and underlying deformation mechanisms of two kinds of interstitial CrMnFeCoNi high entropy alloys (HEAs), (CrMnFeCoNi) 99.5 C 0.5 and (CrMnFeCoNi) 99.0 C 1.0 , are investigated under quasi-static and dynamic tension. Dynamic loading is carried out via a split Hopkinson tension bar system. The pre- and post-deformation microstructures are characterized with electron back scatter diffraction and transmission electron microscopy. Both yield strength and work hardening increase remarkably with increasing strain rate. Plastic deformation in both alloys under quasi-static and dynamic loading are dominated by dislocations, stacking faults, kink bands and deformation twins. Twinning is activated easier under dynamic loading, and twin density decreases with increasing carbon content due to the increased stacking fault energy. The Khan-Liu constitutive model can describe the experimental results for these two interstitial HEAs in a wide strain range. • Both volume fraction and size of the carbides increase with the increase of C content. • The increase of C content and strain rate lead to the increase in σ Y and σ UT. • Twin density decreases with increasing C content due to the increased SF energy. • The Khan-Liu constitutive model is used to describe the deformation. [ABSTRACT FROM AUTHOR]

Ballistic impact experiments are conducted to investigate high-speed penetration of polycarbonate by steel spheres at impact velocities ranging from ∼ 600 to 2400 m s−1. High-speed photography is applied to capture the penetration processes, including projectile trajectories and cavity/damage evolution. Postmortem projectiles are characterized with three-dimensional laser scanning, and postmortem targets, with optical imaging and micro computed tomography. The maximum penetration depth varies nonmonotonically with impact velocity v i , and decreases with increasing v i above about 1777 m s−1. With increasing v i , the damage of polycarbonate targets increases significantly in amplitude and volume. The damage networks, consisting of cracks and voids, exhibit fractal features with similar fractal dimensions. At low v i , plate-shaped cracks are formed in the cavity, while needle-shaped cracks along with a large amount of melting-induced small voids, at high v i. Numerical simulations of impact penetration of polycarbonate reproduces well the experimental observations. Considering projectile distortion, a modified Poncelet model is derived to describe the nonmonotonic relation between the maximum penetration depth and v i. [Display omitted] • Ballistic impact experiments and modeling on polycarbonate with steel spheres. • Maximum penetration depth varies non-monotonically with impact velocity. • Damage morphologies and mechanisms vary with impact velocity. • A modified Poncelet model derived considering projectile distortion. [ABSTRACT FROM AUTHOR]