Explosive Welding, Forming and Compaction

The last two decades have seen a steady and impressive development, and eventual industrial acceptance, of the high energy-rate manufact­ turing techniques based on the utilisation of energy available in an explo­ sive charge. Not only has it become economically viable to fabricate complex shapes and integrally bonded composites-which otherwise might not have been obtainable easily, if at all-but also a source of reasonably cheap energy and uniquely simple techniques, that often dispense with heavy equipment, have been made available to the engineer and applied scientist. The consolidation of theoretical knowledge and practical experience which we have witnessed in this area of activity in the last few years, combined with the growing industrial interest in the explosive forming, welding and compacting processes, makes it possible and also opportune to present, at this stage, an in-depth review of the state of the art. This book is a compendium of monographic contributions, each one of which represents a particular theoretical or industrial facet of the explosive operations. The contributions come from a number of practising engineers and scientists who seek to establish the present state of knowledge in the areas of the formation and propagation of shock and stress waves in metals, their metallurgical effects, and the methods of experimental assessment of these phenomena.

1. Introduction to High-energy-rate Metalworking.- 1.1. Background.- 1.2. High-energy-rate Processes.- 1.2.1. Operation Concepts.- 1.2.2. Basic Types of Operations.- 1.2.3. Nature of Load Application.- 1.3. Development of the Field.- 1.3.1. Early Studies.- 1.3.2. Explosive Forming.- 1.3.3. Explosive Hardening.- 1.3.4. Explosive Compaction.- 1.3.5. Explosive Welding.- 1.4. Continued development of the field.- 1.4.1. Cooperative Effort.- 1.4.2. Thoughts for the Future.- References.- 2. Propagation of Stress Waves in Metals.- 2.1. Dynamic Propagation of Deformation.- 2.2. Elastic Waves.- 2.2.1. Introduction.- 2.2.2. Elastic Waves in Isotropic Materials.- 2.2.3. Elastic Waves in Anisotropic Media.- 2.3. Plastic Waves.- 2.3.1. Preliminary Considerations.- 2.3.2. The von Kármán and Duwez Plastic Wave Theory.- 2.3.3. Plastic Shear Waves.- 2.3.4. Additional Considerations on Plastic Waves.- 2.3.5. Adiabatic Shear Bands.- 2.4. Shock Waves.- 2.4.1. Hydrodynamic Treatment.- 2.4.2. More Advanced Treatments and Computer Codes.- 2.4.3. Attenuation of Shock Waves.- 2.4.4. Elastic Precursor Waves.- 2.5. Defect Generation.- 2.5.1. Dislocation Generation.- 2.5.2 Point Defects.- 2.5.3. Deformation Twinning.- 2.5.4. Displacive/Diffusionless Transformations.- 2.5.5. Other Effects.- Acknowledgements.- References.- 3. Metallurgical Effects of Shock and Pressure Waves in Metals.- 3.1. Principal Features of High-strain-rate and Shock deformation in Metals.- 3.2. Permanent Changes: Residual Microstructure-Mechanical Property Relationships.- 3.2.1. Grain Size Effects.- 3.2.2. Shock-induced Microstructures.- 3.2.3. Shock Deformation Versus Conventional Deformation (Cold Reduction).- 3.2.4. Effects of Shock Pulse Duration in Shock Loading.- 3.2.5. Effects of Point Defects, Precipitates and Other SecondPhase Particles.- 3.3. Response of Metals to Thermomechanical Shock Treatment.- 3.3.1. Shock-mechanical Treatment, Stress-cycling and Repeated Shock Loading.- 3.3.2. Microstructural Stability and Thermal Stabilization of Substructure.- 3.4. Summary and Conclusions.- Acknowledgements.- References.- 4. High-rate straining and Mechanical Properties of Materials.- 4.1. Introduction.- 4.2. Testing Techniques at High Rates of Strain.- 4.2.1. Testing Techniques at Intermediate Rates of Strain.- 4.2.2. Testing Techniques at Impact Rates of Strain.- 4.2.3. Attempts to Reach Higher Strain Rates.- 4.3. Mechanical Properties of Materials at High Rates of Strain.- 4.3.1. Theoretical Considerations.- 4.3.2. Strain-rate Dependence of fcc Materials.- 4.3.3. Strain-rate Dependence of hcp and Orthorhombic Materials.- 4.3.4. Strain-rate Dependence of bcc Materials.- 4.3.5. Mechanical Response at Very High Strain Rates.- 4.3.6. Effect of Changing Strain Rate (Strain Rate History).- 4.4. Mechanical Equations of State at High Rates of Strain.- 4.5. Summary.- References.- 5. Basic Consideration for Commercial Processes.- 5.1. Explosive cladding.- 5.1.1. Introduction.- 5.1.2. Cladding Sites and Facilities.- 5.1.3. Range of Products.- 5.1.4. Bonding Parameters.- 5.2. Design of Clad Assemblies.- 5.2.1. General.- 5.2.2. Shell Plates.- 5.2.3. Tube Plates.- 5.2.4. Metal Requirements.- 5.2.5. Extension Bars.- 5.2.6. Temperature of Metals.- 5.3. Assembly of Clads.- 5.3.1. Metal Preparation.- 5.3.2. Assembly.- 5.3.3. Protection of Cladding Plate Surface.- 5.4. Explosives.- 5.4.1. Main Charge.- 5.4.2. Initiation.- 5.5. Double Sided Clads.- 5.6. Multilayer Clads.- 5.7. Post Cladding Operations.- 5.7.1. Preliminary Examinations.- 5.7.2. Stress Relief.- 5.7.3. Levelling.- 5.7.4. Cutting and Trimming.- 5.7.5. Ultrasonic Testing.- 5.8. Destructive Testing.- 5.9. Tubular Components.- 5.9.1. Nozzles.- 5.9.2. Other Tubular Components.- 5.10. Explosive Hardening.- 6. Mechanics of Explosive Welding.- 6.1. Introduction.- 6.2. The Mechanism of Explosive Welding.- 6.3. Parameters of the Explosive Welding Process.- 6.3.1. The Collision Parameters Vp, Vc,?.- 6.3.2. Limiting Conditions for Welding.- 6.4. Interfacial Waves.- 6.4.1. Introduction.- 6.4.2. Mechanisms of Wave Formation.- 6.5. Analysis of Flow in the Collision Region.- 6.5.1. Introduction.- 6.5.2. The Interfacial Pressure Profile.- 6.5.3. The Flow Pattern in the Collision Region.- References.- 7. Explosive Welding in Planar Geometries.- 7.1. Introduction.- 7.2. Material Combinations and Flyer Thicknesses.- 7.3. Basic Welding Geometries.- 7.3.1. Parallel Geometries.- 7.3.2. Inclined Geometries.- 7.3.3. Parallel/Inclined Geometries.- 7.3.4. Double Inclined Geometries.- 7.3.5. Geometries Producing Welding Conditions Transiently.- 7.4. Selection of Bonding Parameters.- 7.4.1. General Considerations.- 7.4.2. Impact Velocity.- 7.4.3. Explosive Loading.- 7.4.4. Collision Angle/Collision Point Velocity.- 7.4.5. Stand-Off Distance.- 7.4.6. Anvil.- 7.4.7. Surface Finish.- 7.5. Direct Measurement of Bonding Parameters.- 7.5.1. Introduction.- 7.5.2. The Dautriche Method.- 7.5.3. Wire and Pin Contactor Methods.- 7.5.4. High Speed Photography.- 7.5.5. Flash Radiography.- 7.5.6. Velocity Probe.- 7.5.7. Slanting Wire Methods.- 7.6. Miscellaneous Welding Geometries for Sheets and Plates.- 7.6.1. Lap Welding of Narrow Plates.- 7.6.2. Seam/Line Welding of Sheets.- 7.6.3. Scarf Welding.- 7.6.4. Butt Welding.- 7.6.5. Spot Welding.- 7.6.6. Patch Welding.- 7.6.7. Channel Welding.- 7.7. Welding of Foils.- 7.7.1. Theoretical Considerations.- 7.7.2. Welding of Single Foils and Simple Multi-Foil Laminates.- 7.7.3. Wire-Reinforced Composites.- 7.8. Applications.- 7.8.1. Introduction.- 7.8.2. Clad Plate.- 7.8.3. Dissimilar Metal Joints.- 7.8.4. Transition Joints.- 7.8.5. Honeycomb.- 7.9. Conclusions.- Acknowledgements.- References.- 8. Welding of Tubular, Rod and Special Assemblies.- 8.1. Introduction.- 8.2. Explosive and Implosive Welding Systems and Bonding Parameters.- 8.2.1. Welding Systems.- 8.2.2. Welding Mechanisms.- 8.3. Welding of Duplex and Triplex Cylinders.- 8.3.1. Development of Welding Techniques.- 8.3.2. Characteristics of the Welded Systems.- 8.3.3. Residual Stresses.- 8.3.4. Conventional Processing.- 8.4. Tube-to-tubeplate Welding.- 8.4.1. Introduction.- 8.4.2. Geometry and Parameters.- 8.4.3. System Characteristics.- 8.4.4. Properties of Joints.- 8.5. Explosive Plugging of Tubes in Tubeplates.- 8.5.1. Applications.- 8.5.2. Plugging Systems.- 8.5.3. Plugs, Materials and Testing.- 8.6. Multilayer Foil Reinforced Cylinders.- 8.6.1. Introduction.- 8.6.2. Implosive Welding System.- 8.6.3. Pressures and Stresses.- 8.6.4. Structural Properties.- 8.7. Interface Wire Mesh Reinforcement.- 8.7.1. Welding Systems.- 8.7.2. Metallurgical Characteristics.- 8.7.3. Mechanical Properties.- 8.8. Transition Joints.- 8.8.1. Applications and Systems.- 8.8.2. The Machined Joint.- 8.8.3. Welding of Tubular Joints.- 8.9. Solid and Hollow Axisymmetric Components.- 8.9.1. Introduction.- 8.9.2. Welding Systems.- 8.9.3. Hydrostatic Extrusion.- References.- 9. Explosive Forming.- 9.1. Introduction.- 9.2. Formability of Engineering Alloys.- 9.3. Mechanical Properties of Explosively formed Components.- 9.4. Air and Underwater Forming Systems.- 9.5. Die and Dieless Forming.- 9.6. Analysis of Final Shapes in Free-Forming.- 9.7. Parameters and Analysis of Die Design.- 9.8. Forming of Domes and of Elements of Spherical Vessels.- 9.9. Forming and Punching of Tubular Components.- 9.10. Miscellaneous Forming Operations.- 9.11. Conclusion.- References.- 10. Powder Compaction.- 10.1 Introduction.- 10.2 Dynamic Compressibility of Powders.- 10.3. Type of Shock Wave and Density Distribution.- 10.4. Temperature and Strain Rate Effects.- 10.5. Phase Transitions in Shock Loading Mixtures.- 10.6. General Mechanical Properties of Compacted Powders.- 10.7. X-ray and Other Methods of Evaluating Residual Stress Distribution.- 10.8. Basic Problems in Fabricating Semi-finished Parts.- 10.9. Static and Dynamic Compaction: A Comparison of Material Properties.- References.