A Constitutive Model for In Situ Comminuted Silicon Carbide

Cylindrical hot-pressed silicon carbide (SiC) ceramic targets were predamaged before ballistic testing. The SiC was thermally shocked to introduce noncontiguous cracks, then additional damage was induced by load–unload cycling in an MTS machine while the ceramic specimen was confined in a 7075-T6 aluminum sleeve. Long gold rod penetration was measured as a function of impact velocity v _p over the approximate range of 1–3 km/s, with most data between 1.5 and 3 km/s. Penetration as a function of time was measured using multiple, independently timed flash X-rays. It was assumed that the penetration response of the damaged SiC could be represented by a Drucker–Prager constitutive model. Numerical simulations were used to estimate the constitutive constants. It was found that simulations could not be used to determine a unique set of constitutive constants within experimental data scatter.     

Short PCPPs verifiable in polylogarithmic time with O(1) queries

In this paper we show for every pair language $L\subseteq \{0,1\}^*\times\{0,1\}^*$ in ${\ensuremath{\mathsf{NTIME}}}(T)$ for some non-decreasing function $T:{{\mathbb Z}}^+\rightarrow {{\mathbb Z}}^+$ there is a ${\ensuremath{\mathsf{PCPP}}}$ -verifier such that the following holds. In time poly (|x|,log|y|,logT(|x|?+?|y|)) it decides the membership of a purported word (x,y) by reading the explicit input x entirely and querying the implicit input y and the auxiliary proof of length T(|x|?+?|y|)·poly log T(|x|?+?|y|) in a constant number of positions.     

Determination of Coherency and Rigidity Temperatures in Al-Cu Alloys Using In Situ Neutron Diffraction During Casting

The rigidity temperature of a solidifying alloy is the temperature at which the solid phase is sufficiently coalesced to transmit tensile stress. It is a major input parameter in numerical modeling of solidification processes as it defines the point at which thermally induced deformations start to generate internal stresses in a casting. This temperature has been determined for an Al-13 wt.% Cu alloy using in situ neutron diffraction during casting in a dog-bone-shaped mold. This setup allows the sample to build up internal stress naturally as its contraction is not possible. The cooling on both sides of the mold induces a hot spot at the middle of the sample that is irradiated by neutrons. Diffraction patterns are recorded every 11 s using a large detector, and the very first change of diffraction angles allows for the determination of the rigidity temperature. We measured rigidity temperatures equal to 557°C and 548°C depending on the cooling rate for grain refined Al-13 wt.% Cu alloys. At a high cooling rate, rigidity is reached during the formation of the eutectic phase. In this case, the solid phase is not sufficiently coalesced to sustain tensile load and thus cannot avoid hot tear formation.     

Mine blast loading experiments

A comprehensive review of the literature related to mine blast is provided. Then, a series of mine blast loading experiments are described where the soil moisture content, plate standoff, and plate shape (flat and V-shaped) were varied. Three experiments were conducted for each test configuration to quantify repeatability of the experiments. The primary experimental diagnostic was the initial velocity imparted to the plate, as inferred from the maximum height that the plate displaced. The experimental results, besides being of value in their own right, provide a set of data for numerical simulations/validation.