Jet formation in explosion welding
Laminar fluid flow (low collision-point velocity and low Reynolds numbers) was correlated with direct bonding and a very flat bond interface. For subsonic collisions, the elastic strength of the metal must be exceeded before jetting will occur. In both cases, jetting is described by a hydrodynamic flow of the metal surfaces.
- An experimental technique as reported to evaluate both the critical angle for jetting and the morphological changes in explosion bonds resulting from changes in collision angle.
- The experimental setup consisted of the normal flyer plate arrangement used in the parallel gap technique, but with the base plate replaced by a half cylinder.
- Each bonding trial produced continuously changing flayer plate collision angles that resulted in surface deformation and bond morphology variations.
- This analysis expands upon the work of previous researchers by evaluating the geometry of fluid flow, jetting, and their effects on bond morphology.
Laminar fluid flow(low collision-point velocity and low Reynolds numbers) was correlated with direct bonding and a very flat bond interface. Turbulent fluid flow was separated into two regimes:
· AT INTERMEDIATE COLLISION-POINT VELOCITIES, THE FLOW WAS DESCRIBED BY VORTICE FORMATION INTO A VON KARMAN VORTEX STREET AND THE PRODUCTION OF A WAVY BOND INTERFACE
· AT HIGH COLLISION-POINT VELOCITIES, THE FLOW WAS DISTURBED BY A DISORDERING OF THE JET WAKE, WHICH LED TO A MOLTEN LAYER BOND INTERFACE.
Selection of Bonding Parameters
The preceding discussion introduced the primary variables used to predict explosive bonding parameters. The following four conditions are used to define a window of acceptable bonding parameters:
· CRITICAL ANGLE FOR JETTING
· CRITICAL FLOW TRANSITION VELOCITY
· MINIMUM FLYER PLATE IMPACT FOR JETTING, BASED ON ANALYSIS OF THE STRESS REQUIRED TO CAUSE FLOW
· MAXIMUM FLYER PLATE IMPACT FOR THE LIMITATION OF WELD DEFECTS, BASED ON JET ENTRAPMENT
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