The nucleation, growth, and coalescence of microscopic voids are induced inside ductile metal when it is subjected to dynamic tension, and this eventually results in a catastrophic fracture of the specimen. In the present work, this failure property is studied by using ultrapure aluminum (99.999%) as a representative candidate for the ductile metal and, further, the micro-void growth behavior (or the damage evolution) before the catastrophic fracture has been investigated. Measurements of the free surface velocity profile and statistical analysis of micro-voids were used to determine the spall characteristic and damage evolution behavior of dynamic tensile fracture in ultrapure aluminum. Through comparison of the differences between the incompletely and completely spalled signals, the spall characteristics of ultrapure aluminum from incomplete to complete spall were analyzed. Moreover, an obvious critical characteristic is found on the basis of the association between the maximum damage caused within samples and the product of peak stress and tensile duration. The damage variable slowly increased in a linear manner in the initial stages but changed to nonlinear growth and rapidly approached a fracture state as the damage variable extended beyond the critical value, which is approximately 0.09. A physical explanation for this transition is discussed and implicates micro-void linkage behavior during the dynamic failure.

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High-performance yarns are widely used to produce protective fabrics, including stab-resistant materials. The most common approach to studying the mechanism of puncture prevention is to use simulation to assist analysis. However, the anisotropy of the yarn is often overlooked during simulation owing to various factors. In fact, there is a marked difference between the axial and radial properties of a yarn. This may lead to large errors in research. In the present study, a composite material with a grid structure for puncture analysis was designed to investigate the influence of yarn anisotropy on the accuracy of simulation results. The present study combined an actual experiment with a simulation. In the actual experiment, Kevlar yarn/epoxy resin was used to prepare a mesh composite with a spacing of 1 mm. In the simulation, a 1:1 simulation model of composite material was established using finite element software. A simulated puncture experiment was conducted based on the actual experimental conditions and material parameters. After considering yarn anisotropy, the simulation results were closer to the actual experimental results. The simulation revealed that the main failure modes of the mesh material were the fracture of the resin and the bending deformation of the yarns at the junctions, while the surrounding areas were almost unaffected.

A new hot-rolled ship plate with high strength and high toughness is successfully developed through chemical composition design and TMCP process. Experimental methods, such as OM, TEM and X-EDS, were used to study the microstructure and precipitates of steel. The primary microstructural constituent is acicular ferrite, quasi-polygonal ferrite with second constituents along grain boundaries. Lath width of acicular ferrite is about 1μm. Cubic particles about several hundreds nanometers and nanometer particles exist in experimental steel. It can be concluded that acicular ferrite is the main reason for high strength and super toughness. precipitation hardening due to dispersed precipitations of carbonitrides can not be overlooked.

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