On the Wave Formation in Explosive Bonding
1972 Volume 41 Issue 4 Pages 446-455
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1972 Volume 41 Issue 4 Pages 446-455
The interface between explosively bonded metals exhibits a wave-like form, but the theory of formation of wave has not been fully studied. In this paper the relation between wavelength and collision angle was investigated by using the semi-cylinder method and angular method, and an attempt to explain the mechanism of wave formation was made. The results obtained are as follows.
1. The wavelength increased continuously with the collision angle until a critical angle, beyond which the wave-like profile vanished and a linear interface was observed. For a given value of collision angle, the wavelength increased with the plate thickness. However the collision velocity at the critical angle was constant independently of plate thickness.
In angular method, the wave tended to grow in the direction of bonding and none was observed for the distance of 20-30 mm from starting to bond.
2. The wave amplitude increased with the collision angle but the ratio of amplitude to wavelength was constant.
3. The material near the interface suffered extreme plastic deformation and the folw configuration, in particular wave-like profile, resembled the stream pattern in a fluid having a Karman vortex street, so the authors considered that a wavy interface resulting from Kármán vortex street occurred in the vicinity of collision point and they tried to calculate the wavelength λ. The following equation was used.
For a symmetric collision shown in Fig. 12 (a) : collision angle 2γ, λ=20h (1-cosγ)
For an asymmetric collision shown in Fig. 12 (b) : collision angle γ, λ=10h (1-cosγ) where h: the thickness of flyer plate.
The values calculated by using these equations agreed generally with measured values.
4. An increase in hardness at interface, when the collision velocity exceeded 1800 m/sec, was observed in bonding an iron flyer plate to a mild steel semi-cylinder. This fact might be attributed to martensite marking of the pressure-induced tranformation that appeared at a pressure more than 130 Kbar in iron.
