8/3/2019 Katsumi Tanaka- Numerical Studies on the Explosive Welding by Smooth Particle Hydrodynamics (SPH)

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NUMERICAL STUDIES ON THE EXPLOSIVE WELDING BY

SMOOTHED PARTICLE HYDRODYNAMICS (SPH)

Katsumi Tanaka

National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8568, JAPAN

Abstract. A particular characteristic of an explosively produced weld is that the profile of the weld

interface often has a regular wavy appearance. Effects of detached shock wave and jetting on the metal

interface of explosive welding has been considered by SPH. Numerical results show wavy interface

which is observed in several experiments. A high speed jet between interface and Karman vortex after

oblique impact of a flyer plate to a parent plate were major mechanism of explosive welding.

Keywords: SPH, Explosive Welding, Karman Vortex, Oblique Impact

PACS: 47.55.Ca, 47.55.dd, 82.33.Vx

INTRODUCTION

Theoretical and experimental studies on the

explosive welding have been extensively

reported[1-14]. Numerical studies of explosive

welding by hydrocode [9,10] showed jetting at

collision point of flyer and parent metal plate butwavy structure is not reproduced clearly. Eulerian

CFD study [12] reproduced wavy structure of bi-

metallic interface but detailed mechanism is not

still cleared. Euler computation can be applicable

to plate impact problems but it has several

difficulties for historical change of pressure,

velocity and other physical properties in materials.

Euler computation requires special algorithm for

multi-materials system. While Lagrangian

computation is desirable, numerical analysis of the

plate impact accompanying metal jet gives tangled

mesh. SPH is the one of method of gridless

Lagrangian hydrodynamics using particles and hasbeen applied to the astronomical science, high

velocity impact phenomena, metal jet formed by

shaped charge or collapsing void and phenomenon

with large deformation. SPH is applied to study the

mechanism of the explosive welding in this work.

Impact angle and velocity of flyer plate are

important factor and these are controlled by

detonation of high explosive charge which is

mostly non-ideal explosive with detonation

velocity lower than shock velocity in both metal

plate. Flyer plate acceleration by detonation of

non-ideal explosive is considerably complicated

mechanism. The effect of mechanical properties,

impact angle, velocity of flyer plate near the

boundary between flyer plate and parent plate are

discussed based on SPH results.

NUMERICAL MODEL OF SPH

The particle used in the SPH represents the

point of mass of Lagrangian motion. Governing

equations of derivatives of conservation laws are

discretized by integral form given bellow,

'),'()'()(

'),'()'()(

2

2

2

2

dxhxxWxfxf

dxhxxWxfxf

h

h

h

h

>==