Dynamic response of Sn over the temperature range 115–503 K

Planar impact experiments were performed with high purity (99.9985 %) and commercial purity (99.8 %) tin over the temperature range 115 to 503 K. The free surface velocity histories of 2-mm tin samples impacted by 0.5-mm copper flyer plates having velocity of about 350 m/s were recorded with the VISAR. The impact response of the coarse-grain samples of both the tins is associated with relatively large scattering of the Hugoniot elastic limit, the plastic wave rise time, and the spall strength. The dynamic tensile (spall) strength of both the alloys show weak growth with temperature with exception of the close, 15–20 K vicinity of the tin melting point where the spall strength of both the alloys experiences an abrupt two-fold drop. The dynamic shear stresses show obvious trend to grow or at least do not decrease with the increasing temperature. The free surface velocity histories and the spall data obtained below 286 K do not show any peculiarities which could be associated with the β–α transition in tin

Evidences of ductile and brittle responses of ceramics under shock wave loading

Compressive failure strength of brittle solids increases rapidly with the confining pressure whereas the yield stress of ductile materials is much less sensitive to the confinement. The presented experimental technique utilizes this difference in the effect of the confinement in order to reveal the mode of ceramics behavior under shockwave compression. A controlled confining pressure on the lateral surface of the disk-like ceramic specimen was produced by fixing the specimen into a shrink-fit metal sleeve. The effect of such confinement on the Hugoniot Elastic Limit should differ by a factor of about 2.5 for the materials whose ductile yielding is governed by Von Mises criterion and those obeyed the Griffith's criterion of brittle failure. Results of the tests performed exhibit unambiguously the ductile response of the alumina ceramics whereas the response of the boron carbide ceramics is certainly brittle

Impact response of titanium alloys at elevated temperatures

The paper presents results of investigations of temperature effect on dynamic yield stress and spall strength of high-purity titanium, commercial grade titaniurn, and $\alpha+\beta$ altoy Ti-6Al-2Sn-2Zr-2Cr-2Mo-Si at submicrosecond durations of shock-wave loading. The high-purity titanium exhibited anomalous growth of the yield stress whereas the behaviors of commercial titanium and titanium alloy are similar to that under normal conditions. In comparison with the yield stress the spall strength of the studied materials is much less sensitive to their composition and the test temperature. The measurements confirmed the polymorphous transformation in high-purity titanium, although both the transformation pressure and it temperature dependence differ from known data

1-D and 2-D modeling of U-Ti alloy response in impact experiments

Dynamie response of a U-0.75wt%Ti alloy bas been studied in planar (disk-on-disk), reverse (disk-on-rod) and symmetric (rod-on-rod) ballistic impact experiments performed with a 25 mm light-gas gun. The impact velocities ranged between 100 and 500 m/see and the samples were softly recovered for further examination, revealing different degrees of spall fracture (planar impact) and of adiabatic shear bands (ballistic experiments). The back (planar experiments) and the lateral (ballistic experiments) surface velocities were continuously monitored by VISAR. The velocity profiles and the damage maps were simulated using a 2-D AUTODYN$^{\rm TM}$ Lagrangian finite differences code. Simulations of the planar experiments were performed with special attention to the compressive path of the loading cycle in order to calibrate a modified Steinberg-Cochran-Guinan (SCG) constitutive model. The Bauschinger effect and a single-parameter spall model were added to describe the unloading and tensile paths. The calibrated SCG model was then employed to simulate the ballistic experiments. An erosion AUTODYN built-in subroutine with a threshold value of plastic strain was chosen to describe the failure in the ballistic impact experiments. The results of the suggested experimental-numerical technique can be taken into account in estimating the different contributions to the shock-induced plastic deformation and failure

Design of online spheroidization process for 1.0C-1.5Cr bearing steel and microstructure analysis

Using thermo-mechanical control process, the online spheroidization annealing process of 1.0C-1.5Cr bearing steel was designed. Apart from intercritical online spheroidization (IS), a novel subcritical online spheroidization (SS) process was proposed, which is characterized by water-cooling to around 773 K (500 A degrees C) after the final rolling pass, and then directly reheating to 973 K (700 A degrees C) for isothermal holding. Compared with the results from the traditional offline spheroidization (TS) process, the size of spheroidized carbides is similar in both the TS and IS processes, whereas it is much smaller in the SS process. After spheroidization annealing, microstructure evolution during austenitization and quenching treatment was examined. It is shown that the refining of spheroidized carbides accelerates the dissolution of carbides during the austenitizing process, and decreases the size of undissolved carbides. In addition, the SS process can obtain finer prior austenite grain after quenching, which contributes to the enhancement of final hardness. (C) The Minerals, Metals & Materials Society and ASM International 201811sciescopu