Abstract
In order to study the dynamic response of tungsten heavy alloy materials under explosive loading, two kinds of typical tungsten alloys for explosively formed projectile (EFP) liner and one kind of existing EFP liner were tested in a flash X-ray experiment, with copper liner as a reference. Results showed that copper liner could form a coherent EFP, while 90W–9Ni–Co and W–25Re liners fractured to different extents. The microscopic features of the three kinds of metals were examined and compared with the original liner, and the microstructure evolutions under explosive loading were analyzed with the fracture model and mechanism of the two kinds of tungsten alloys’ fracture determined. Associated with the stress and strain conditions by numerical simulation, the fracture mechanism of tungsten heavy alloys can be analyzed. The crack-tip plastic zones of 90W–9Ni–Co and W–25Re are much smaller than copper, and due to the severe stress concentration at the tip of cracks, it is easy for cracks to propagate and trigger the cleavage in tungsten alloys. The value of a crack-tip plastic zone r(θ) can be used to explain the fracture phenomenon in explosive loading, which can be an alternative guideline for the material selection criteria of the EFP liner. The research results are significant in understanding the dynamic forming, microstructure evolution, and fracture mechanism of tungsten heavy alloys.
Highlights
According to the shaped-charge mechanism, the explosively formed projectile (EFP) makes full use of explosive blasting to form the liner into a preferred penetrator without breaking [1,2,3]
As two kinds of typical tungsten alloy with good plasticity, 90W–9Ni–Co and W–25Re alloy have much higher density and yield stress compared with copper (OFHC, oxygenfree high-conductivity copper)
The dynamic recrystallization and ductile fracture surface observed in the microstructure of copper explain the dynamic formation of a copper EFP under explosive loading, while the micro-cracks and cleavage observed in the 90W–9Ni–Co and W–25Re alloy which indicate the occurrence of brittle fracture are the predominant fracture mechanism and microstructure evolution of the two kinds of tungsten heavy alloy under explosive loading
Summary
According to the shaped-charge mechanism, the explosively formed projectile (EFP) makes full use of explosive blasting to form the liner into a preferred penetrator without breaking [1,2,3]. Whether liners of tungsten and its alloys could form EFPs and the dynamic response of tungsten liner under explosive loading have not yet been studied in experiments. The liner of tungsten alloy could form complete EFPs with low solidity in the numerical simulation. Their numerical simulation results have not yet been validated in experiments. The radiograph of the X-ray experiment and soft recovered tungsten alloy penetrators from the tests clearly showed the fracture characteristics with charge structure for severe deformation. Flash X-ray experiment was carried out to observe the dynamic response and formation characteristic of liners.
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