Polymer-bonded explosive (PBX) is used widely in weapon systems. Failure of PBX caused by mechanical damage is one of the sources of accidental ignitions. A brittle crack of PBX produces local heating, creating a 'hot spot' finally. Investigation into the tensile fracture behaviour of PBX is one of the main works to determine the failure mechanism. Although many researchers have carried out the quasi-static Brazilian test to understand the damage evolution of PBX, the fracture feature of PBX under dynamic impact is rarely reported. In this article, dynamic Brazilian tests were conducted. A single-pulse loading apparatus was used to ensure that specimen was loaded only once during a dynamic Brazilian test. High-speed camera, digital image correlation and micro-observation techniques were adopted for strain measurement and microfracture observation. All the dynamic tensile crack exhibits transgranular fracture, which indicates more heat would released by the propagation of crack and more friction between fractured crystal surfaces. On the basis of the theories of interface debonding and transgranular fracture, larger crystals are more prone to crack, whereas smaller crystals simply debond with neighbouring binders. Discrete element method simulation results show that specimen with interface debonding microcracks was able to sustain additional load until transgranular fracture begins.
Eddy current is presented in electric coil when it approaches metallic conductor. Different metals have different conductivity and permeability. Therefore, the equivalent impedances of the electric coil are also different. Based on the principle, a Steel material sorting instrument was made to detect the steel permeability level, through the permeability level, combined with the central processing circuit steel hardness values reflect iron parts, materials and the carbon content of steel, mixing nondestructive sorting.
Zirconium rich corner’s isothermal section of the Zr-Sn-Nb system at 450°C was determined by using X-ray diffraction. Experiment results showed that this isothermal section consisted of 2 three-phase region: ((βNb) + Zr4Sn + (αZr)) and (Zr4Sn + (βNb) + Zr5Sn3), 3 two-phases region: ((βNb) + (αZr)), (Zr4Sn + Zr5Sn3) and (Zr4Sn + (αZr)), and 4 single-phase region: (βNb), (αZr), Zr4Sn, Zr5Sn3.
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