Ballistic performance of spherical fragments penetrating PCrNi3MoV target plates

PCrNi3MoV steel is a medium-carbon,low-alloy quenched and tempered steel that finds its applications in military gun barrels due to the high wear resistance and ablation resistance.To study the penetration and failure modes of PCrNi3MoV plates impacted by tungsten spheres,tungsten spheres of various diameters(5 mm,8 mm,and 10 mm)were used to impact PCrNi3MoV steel plates with thicknesses of 6 mm,9 mm,and 14 mm.The penetration performance of the spheres was analyzed for different velocities,and the ultimate penetration velocity of the plate was obtained.It was found that the primary failure modes of the PCrNi3MoV plate were compression pitting failure and shear failure.Using the dimensional analysis method,a relationship between the bulge height of the steel plate and the fragment velocity,an equation for the ultimate penetration velocity,and a relationship between the target penetration energy and the fragment velocity were obtained.Then,a projectile-target action index was proposed to describe the process of tungsten spheres with different velocities impacting target plates.The results suggested that under the same thickness of the target plate,a larger-diameter fragment required more kinetic energy to obtain the same ultimate penetration effect as a smaller-diameter fragment.The equations obtained through dimensional analysis predicted values that agreed well with experimental values,indicating that these equations can be applied to engineering applications.

Experimental and Theoretical Study on the Self-Weight Penetration Velocity of Suction Anchor Foundations in Sand

The application of the wellhead suction anchor in the second production test of natural gas hydrates(NGHs)in the South China Sea(SCS)was met with success.This design incorporates a central conductor guide pipe,which distinguishes it from traditional suction foundations.However,this addition resulted in a relatively high penetration resistance and a shallower penetration depth at the self-weight penetration stage.To mitigate this issue,the current study proposes an optimized design where the end of the suction foundation is sharpened.The installation characteristics of the traditional suction foundation and new suction foundation during self-weight penetration into sand are studied through laboratory tests and theoretical analysis.The flat and sharpened bottom shapes are considered in the traditional and new suction models.The effects of the initial penetration velocity on the initial penetration depth and soil plug and impact cavity characteristics are systematically studied.The results show that the self-weight penetration depth of the foundation with a sharpened bottom is 44.5%deeper than that of the foundation with a flat bottom.There are cavities around the foundation at the self-weight penetration stage,and the penetration depth is overestimated by 15%-30%.Finally,a model for predicting the penetration depth of the new suction foundation is proposed.

Analytical models for the penetration of semi-infinite targets by rigid,deformable and erosive long rods

A theoretical study is presented herein on the pen- etration of a semi-infinite target by a spherical-headed long rod for Yp 〉 S, where Yp is the penetrator strength and S is the static target resistance. For Yp 〉 S, depending upon initial impact velocity, there exist three types of penetration, namely, penetration by a rigid long rod, penetration by a deforming non-erosive long rod and penetration by an erosive long rod. If the impact velocity of the penetrator is higher than the hydrodynamic velocity （VH）, it will penetrate the target in an erosive mode; if the impact velocity lies between the hydrodynamic velocity （VH） and the rigid body velocity （VR）, it will penetrate the target in a deformable mode; if the impact velocity is less than the rigid body velocity （VR）, it will penetrate the target in a rigid mode. The critical conditions for the transition among these three penetration modes are proposed. It is demonstrated that the present model predictions correlate well with the experimental observations in terms of depth of penetration （DOP） and the critical transition conditions.

Influence of the attitude of cylindrical tungsten alloy fragment on the ability of penetrating thin metal target plate

The cylindrical tungsten alloy fragment is often prefabricated in the directional warhead to improve the killing ability or interception ability of the warhead.To study the influence of the attitude of fragments on the ability to penetrate thin metal target plates,theoretical calculation,and numerical simulation are used to study the ultimate penetration velocity of cylindrical tungsten alloy fragments with different aspect ratios impacting thin metal target plates vertically with a different attitude.The angle between the axis of a cylindrical tungsten alloy fragment and the normal direction of the target plate is defined as the attitude angle of the fragment perpendicular to the target plate.It is found that when the attitude angle changes from 0°to 90°,the ultimate penetration velocity of fragments increases first and then decreases.When the length-to-diameter ratio of fragments is 1.0,1.2,and 1.5,the relative errors between the minimum and maximum values of the ultimate penetration velocity are about 11.99%,15.75%,and 14.35%,respectively.The ultimate penetration velocity of fragments increases with the increase of the projection area of fragments on the target plate.

Flow field analyses of a porous membrane-separated,double-layered microfluidic chip for cell co-culture

Organs-on-chips composed of a porous membrane-separated,double-layered channels are used widely in elucidating the effects of cell co-culture and flow shear on biological functions.While the diversity of channel geometry and membrane permeability is applied,their quantitative correlation with flow features is still unclear.Immersed boundary methods(IBM)simulations and theoretical modelling were performed in this study.Numerical simulations showed that channel length,height and membrane permeability jointly regulated the flow features of flux,penetration velocity and wall shear stress(WSS).Increase of channel length,lower channel height or membrane permeability monotonically reduced the flow flux,velocity and WSS in upper channel before reaching a plateau.While the flow flux in lower channel monotonically increased with the increase of each factor,the WSS surprisingly exhibited a biphasic pattern with first increase and then decrease with increase of lower channel height.Moreover,the transition threshold of maximum WSS was sensitive to the channel length and membrane permeability.Theoretical modeling,integrating the transmembrane pressure difference and inlet flow flux with chip geometry and membrane permeability,was in good agreement with IBM simulations.These analyses provided theoretical bases for optimizing flow-specified chip design and evaluating flow microenvironments of in vivo tissue.