1. POSSIBILITY OF LINEAR WELDING OF THIN METAL PLATE BY UNDERWATER EXPLOSIVE WELDING Akihisa Mori*, Kazumasa Shiramoto, Masahiro Fujita Faculty of Engineering, Sojo University *E-mail: makihisa@mec.sojo-u.ac.jp EPNM2012

2. Introduction Underwater explosive welding; A welding method using underwater shock wave generated by the detonation of explosive in the water. （ Advantage ） ・ Easy to control the pressurizing conditions by only changing the distance between the explosive and the flyer plate. ・ A flyer plate is accelerated at a high-velocity immediately with in a small stand-off distance. Schematic of the underwater shockwave welding method when the high-explosive is used. Flyer plate Base plate Possible to weld a thin plate which is difficult to weld by the conventional explosive welding method.

3. The method to weld partially be developed to make a large-size sample, when the size of thin plate is limited. The underwater explosive welding technique is suitable to weld the whole thin plate. Motivation Thin plate/foil (size is limited, brittle materials) Amorphous film,etc.

4. Detonating code Detonating code (fuse): / flexible code with an explosive core / detonation velocity: 6310m/s / diameter: 5.4mm / common usage; ignition of explosive Core: Pentaerythritol tetranitrate (PETN) Covering materials: Thread, paper, asphalt (for waterproof) KAYAKU JAPAN Corp.

5. Welding of lap joints ( Welding of lap joints (Ref: B. Crossland, Explosive welding of metals and its application) In the past report, no welding area is generated when the line explosive is set on the flyer plate. Because the flyer plate is collided to base plate without an angle or with a small angle in this area.

6. Weldability window proposed by Wittman and Deribas Ref. M.A.Meyers, Dynamic Behavior of Materials Horizontal collision point velocity, V c Collision angle,  (1) (2) (3) (4) Relation of the collision velocity Vp, the collision angle β and the horizontal collision velosity Vc       2 V2V cp  sin  To obtain the good welding in explosive welding, the collision angle β and the horizontal collision velocity Vc, or the collision velocity, Vp are in the area enclosed with four boundary lines shown the upper figure.

7. Setup of underwater explosive welding technique using detonating code Base plate Reflector Anvil Explosive holder Flyer plate Detonating code Spacer Front of the underwater shock wave Distance from the center of detonating code to the sample Thickness of spacer = Stand off distance Width of gap The front of underwater shock wave Detonating direction （ 6km/s ） Detonating code(D.C.)

8. Sample setup l = 0 mm, 9 mm, 14mm w=5 mm, 10mm 11 mm Stand-off x = 0 mm Welding direction Flyer: Al (0.3mm) 304ss (0.1mm) Base: Cu (0.3mm) hc hc: distance from the center of explosive to the surface of sample l : distance from the explosive holder to the edge of gap

9. Experimental assembly Reinforcement Water Bottom plate Reflector Guide Bottom plate Reflector Anvil Base plate Spacer Flyer plate Detonating code 50 mm 70 mm Explosive holder 50 mm

10. Experimental results Flyer : Al (0.3mm) Base: Cu(0.3mm) gap w =10mm x 10 x5x5 50 μm Spacer (304SS) Al Cu Spacer Al Cu x 10 = 0.0 mmx 10 = 5.0 mmx 10 = 10.0 mm x 5 = 0.0 mm x 5 = 2.4 mmx 5 = 4.8 mm Trapped metal jet w =5mm l = 9 mm Standoff : 0.1mm (stainless steel) hc = 6.3 mm

11. Experimental results x 10 x5x5 50 μm Spacer Al Cu Spacer Al Cu x 10 = 0.0 mmx 10 = 2.3 mmx 10 = 4.6 mm x 5 = 0.0 mm x 5 = 2.7 mmx 5 = 4.9 mm Trapped metal jet Spacer l = 9 mm gap w =10mmw =5mm Flyer : Al (0.3mm) Base: Cu(0.3mm) Standoff : 0.1mm (stainless steel) hc = 9.3 mm

12. 200μm Experimental results l = 9.0 mm, w = 5 mm 200μm Flyer : Al (0.3mm) Base: Cu(0.3mm) Standoff : 0.038mm (amorphos film) hc = 6.3 mm

13. 200μm100μm Experimental results l = 9.0 mm, w = 5 mm Flyer : 304 stainless steel (0.1mm) Spacer : 304 stainless steel (0.1 mm) hc = 6.3 mm

14. 200μm100μm Experimental results l = 9.0 mm, w = 5 mm Flyer : 304 stainless steel (0.1mm) Spacer : Aluminum foil (0.011 mm) hc = 6.3 mm 50μm

15. Experimental setup Base plate Reflector Anvil Explosive holder Cover plate Detonating code Spacer Front of the underwater shock wave Distance from the center of detonating code to the sample Thickness of spacer = Stand off distance Width of gap Amorphous

16. Amorphous film/ copper combination Amorphous (MBF20, 38μm) Cu(0.3mm) l = 9.0 mm, w = 5 mm, Cover: Al, standoff: 0.038mm Cu(0.3mm) l = 0.0 mm, w = 10 mm, Cover: 304SS (0.1mm), standoff: 0.011mm Welded length (without cracks ) : about 1.2 mm Amorphous (MBF20, 38μm)

17. Numeical model materialssolver (1)WaterEuler (2) Reflector （ 304SS ） Euler (3)Detonating codeEuler (4) Base plate （ Cu ） Lagrange (5) Cover plate （ Al ） Lagrange (6) Spacer （ Al 0.1mm ） Lagrange (7) Flyer （ Amorphous film ） Shell (1) (6) (5) (4) (3) (2) Starting point of detonation (7) gap x = 0 mmx = 10 mm

19. Numerical results X Lower limit *) standoff distance = 0.1mm

20. Numerical results *) standoff distance = 0.1mm

21. Summary In this study, experimental and numerical results of for the underwater explosive welding method using the detonating code are introduced. By the observation using the optical microscope, the good welding was achieved in case of a thin aluminum plate and a thin copper plate combination, even if the standoff if the standoff was extremely short. In the materials combination of amorphous film and a copper plate, the welding was succeeded although cracks were generated.

22. 200μm20μm Future plan

23. Research center for advances in impact engineering, SOJO University TEM Water tank in explosion room Experimental devise to detonate explosives in vacuum Thank you for your attention

26. Setup of underwater explosive welding technique using detonating code Plan view The front of underwater shock wave Top view Propagating direction of underwater shock wave (welding direction) Reflector Explosive holder Flyer plate Base plate Spacer Anvil Detonating direction （ 6km/s ） gap In this setup, an underwater shock wave acts for the flyer plate diagonally. Then, the welding is achieved in the limited area because the flyer plate is collided with a certain angle D.C. Detonating code(D.C.)

27. Simulation model 60mm 35mm 11mm 10mm15mm 9mm Φ5.5mm

28. ゲージ設定 Simulation model(Gauge) x =0mm 0.5mm ゲージ間隔 :0.5mm

30. Experimental results x 10 x5x5 50 μm Al Cu Al Cu x 10 = 0.6 mmx 10 = 4.1 mmx 10 = 7.7 mm x 5 = 0.5 mm x 5 = 2.1 mmx 5 = 4.7 mm Flyer : Al (0.3mm) Standoff : 0.3mm hc = 9.3 mm l = 9 mm gap w =10mmw =5mm

31. Cu(0.3mm) Amorphous film/ copper combination l = 0.0 mm, w = 10 mm, Cover: 304SS (0.1mm), standoff: 0.011mm Welded length (without cracks ) : about 1.2 mm Amorphous (MBF20, 38μm)

32. 200μm20μm

33. Numerical analysis(AUTODYN-2D) Al 1100-H12 PVC DF Water S.S. 304 Explosive holder Void Spacer (PVC or S.S. 304) Flyer (Al1100-H12) Starting area of detonation *) Excluding the base plate Measuring point (0.5mm-interval)

34. Numerical analysis(AUTODYN-2D)

35. Parameters with horizontal position (A2, A4) Parameters, such as the horizontal collision point velocity, collsion angle, with horizontal position are shown in the upper figure. As shown in this figure, parameters are changing linearly with the horizontal position, excluding the position slightly far from the spacer and around the end side.

36. Weldablity window obtained by numerical results Numerical results agree well with the experimental results ( A2: welded length = 5.7mm, welding conditions become same values, compared with the 0.3mm- standoff case.