Influence of shear sensitivities of steel projectiles on their ballistic performances

In ballistic penetration, a main failure mode for a projectile is adiabatic shear localization which results in macro cracks developing along ASBs which lead to the fracture of projectile. In this paper, the adiabatic shear sensitivity and ballistic performances of two high strength steels, 30CrMnSi and 35CrWMo, with similar static mechanical properties were investigated. Split Hopkin- son Pressure Bar （SHPB） for compression loading and ballistic experiments above the velocity of 1 000 m/s against thick concrete targets were performed. The SHPB and ballistic experimental results showed that the 30CrMnSi steel exhibits more adiabatic shear sensitivity, compared with the 35CrWMo steel. Even though these two steels have similar static mechanical properties, the 35CrWMo steel projectile exhibits better penetration performance than the 30CrMnSi projectile due to different adiabatic shear sensitivities.

Windtunnel studies of surface shear stress vector distribution measurement using shear sensitive liquid crystal coatings

Shear sensitive liquid crystal coating (SSLCC) can measure surface shear stress vector distribution efficiently with a high spa-tial resolution. The purpose of the present paper is to modify and extend the surface shear stress measurement technique de-termined by Reda et al. to wind tunnel studies. All the facilities employed in the technique are very common and simple. The measurement technique is applied to surface flow beneath a tangential jet and surface flow in a turbulence wedge generated by a small cylinder in windtunnel flow. Spatially resolved shear stresses over planar surface are obtained, although the magnitude is not fully calibrated.

Shear Induced Morphological Transformation of Large Compound Micelles Formed by Glutathione End-capped Poly（4-vinylpyridine）

Here we report novel shear-sensitive polymeric large compound micelles （LCMs） formed by self-assembly of glutathione end-capped poly（4-vinylpyridine） （GP4VP） in water containing 4 vol% methanol. The amphiphile prefers to form the kinetieally stabilized LCMs due to the small length ratio of the hydrophilic part to the hydrophobic part; the encapsulation of the hydrophilic part within LCMs causes only a small enthalpy loss from a thermody- namic view. Sheared by vortex flows generated by vigorous stir, the LCMs evolve to thick wall vesicles, thin wall vesicles, broken vesicles and ＂pearl-necklace＂ structures consecutively. The high flexibility of the LCMs and the internal tension caused by the encapsulation of the hydrophilic part are responsible for the high shear sensitivity of the LCMs.

Effects of strain rates on dynamic deformation behavior of Cu-20Ag alloy

Copper alloy is widely used in high-speed railway,aerospace and other fields due to its excellent electrical conductivity and mechanical properties.High speed deformation and dynamic loading under impact load is a complex service condition,which widely exists in the field of national defense,military and industrial application.Therefore,the dynamic deformation behavior of the Cu-20Ag alloy was investigated by Split Hopkinson Pressure Bar(SHPB)with the strain rates of 1000-25000 s^(-1),high-speed hydraulic servo material testing machine with the strain rates of 1-500 s^(-1).The effect of strain rate on flow stress and adiabatic shear sensitivity was analyzed.The results show that the increase of strain rate will increase the flow stress and critical strain,that is to say,the increase of strain rate will reduce the adiabatic shear sensitivity of the Cu-20Ag alloy.The Cu-Ag interface has obvious orientation relationship with;(111)_(Cu)//(111)_(Ag):(^(-)111)_(Cu)//(^(-)111)_(Ag):(^(-)200)_(Cu)//(^(-)200)_(Ag) and [0^(-)11]_(Cu)//[0^(-)11]_(Ag) with the increase of strain rate.The increase of strain rate promotes the precipitation of Ag and increases the number of interfaces in the microstructure,which hinders the movement of dislocations and improves the stress and yield strength of the Cu-20Ag alloy.The concentration and distribution density of dislocations and the precipitation of Ag were the main reasons improve the flow stress and yield strength of the Cu-20Ag alloy.