Observation for the High-Speed Oblique Collision of Metals

In explosive welding, it is known well that the collision angle and collision velocity are the important parameters to achieve good welding. In addition, generations of a metal jet and the interfacial waves are important for the explosive welding conditions. To know the parameters and the collision conditions, the optical observation and the numerical simulation for the oblique collision using a powder gun were done by the authors. A metal jet was observed clearly by using a powder gun and wavy interface was generated without the intermetallic layer for the reactive materials by controlling the welding conditions. In this investigation, the results of the optical observations and the numerical analysis for similar and dissimilar material combinations were reported. Introduction Explosive welding technique is known well as the welding method to weld strongly for the two metal plates of similar and/or dissimilar material combinations. In explosive welding technique, a metal flyer plate is accelerated by the detonation of explosive and is collided to another metal plate (base plate) with a certain angle at high velocity. A good welding is achieved with generating the interfacial waves in the welded interface and the metal jet at the collision point when the velocity and the angle collided are within the suitable range [1, 2]. Therefore, to achieve the optimal welding conditions for the difficult-to-weld materials, it is necessary to know the parameters and the collision phenomena, such as the metal jet generations and the interfacial waves. The mechanism of interfacial waves and the metal jet generation have been studied theoretically and/or numerically by many researchers [3-5]. Onzawa et al. [6] reported about the characteristics of metal jet generated by the collision of similar and dissimilar metals set on parallel and angular arrangement using a high-speed streak camera. The observation for the metal jet generation is difficult by the optical observation system because the detonation gas spreads out rapidly with the high velocity which is faster than the flying velocity of metal. From the weldability window proposed by Wittman [7] and Deribas [8], claddings same as explosive welding can be obtained when a metal plate collides obliquely at high velocity. To know the inclined collision, same as the phenomena of explosive welding, a powder gun was applied to observe the high-speed oblique collision, which is same as the phenomena of explosive welding, without the influence of detonation gas. And the numerical simulation using SPH solver in ANSYS AUTODYN software was used to understand the material behavior in the high-speed oblique collision, comparing with the experimental results. Explosion Shock Waves and High Strain Rate Phenomena Materials Research Forum LLC Materials Research Proceedings 13 (2019) 74-78 https://doi.org/10.21741/9781644900338-13 75 Experimental Procedure Experimental setup to observe the high-speed oblique collision is shown in Figure 1. A powder gun set on Institute of Pulsed Power Science in Kumamoto University was used to accelerate the metal plate. A pure copper and magnesium alloy AZ31, which diameter were 32 mm and thickness was 3 mm or 5 mm, were applied as the flyer and target plate. The flyer plate was combined the sabot made by Ultra high molecular weight polyethylene (UHPE) as the projectile. The projectile was set in the barrel of the powder chamber side. The copper weight-control plate was placed behind the flyer plate to control the flying velocity of projectile. The target plate put into a PMMA target holder was arranged on the target stand with an inclined angle (θ = 7, 10, 15, 20) in the target chamber. For the optical observation of the oblique collision, High-speed video camera (HPV-1, Shimadzu corp., capable of recording up to 1 million fps) was placed at the side of the target chamber and was located in the opposite side of the light across the target chamber. Smokeless and the black gunpowder were set in the powder chamber. After the target chamber was in a vacuum, the black gunpowder was ignited. Numerical Analysis Explicit dynamics software ANSYS AUTODYN was used and the 2-dimensional planer symmetry was applied to know the detail of the oblique collision at high velocity numerically. A target plate and a projectile were modeled by two solvers, which were the Smoothed Particle Hydrodynamics (SPH) solver and the Lagrangian solver. The 60% thickness part on the collision side of the metal plate was modeled by the SPH solver, and the remaining 40% was applied by the Lagrangian. The particle size of SPH solver and the mesh size of Lagragian solver were fixed at 0.05 mm and 0.03 mm when the thickness of metal plates was 5 mm and 3 mm respectively. The Mie-Grüneisen form shock equation of stat and the Johnson-Cook strength model were applied for each material. The material parameters for each equation are referred from the reports [9, 10]. 6000 mm Flyer metal plate Trigger pin φ32 mm φ40 mm Sabot Barrel Target plate Target holder Target stand θ Controller High-speed video camera Light