Laser Material Processing

Transcription

1 William M. Steen Jyotirmoy Mazumder Laser Material Processing 4th Edition yq. Springer

2 Contents Prologue 1 References 8 1 Background to Laser Design and General Applications Basic Principles of Lasers Stimulated Emission Phenomenon Basic Components of a Laser Physics of the Generation of Laser Light Relationship Between the Einstein Coefficients Lifetime Broadening Transition Rates for Monochromatic Waves Amplification by an Atomic System The Laser: Oscillation and Amplification Laser Construction Concepts Overall Design Types of Laser Gas Lasers Solid-state Lasers Dye Lasers Free-electron Lasers Applications of Lasers Powerful Light Alignment Measurement of Length Velocity Measurement Holography Speckle Interferometry Measurement of Atmospheric Pollution and Dynamics Inspection Analytical Technique Recording Communications Heat Source Medical Uses Printing Isotope Separation Atomic Fusion Stimulated Radioactive Decay? 74 IX

3 1.5 Market for Laser Applications 74 References 76 Basic Laser Optics The Nature of Electromagnetic Radiation Interaction of Electromagnetic Radiation with Matter Nonlinear Effects Reflection or Absorption Effect of Wavelength Effect of Temperature Effect of Surface Films Effect of Angle of Incidence Effect of Materials and Surface Roughness Refraction Scattering Interference Diffraction Laser Beam Characteristics Wavelength Coherence Mode and Beam Diameter Polarisation Focusing with a Single Lens Focused Spot Size Depth of Focus Optical Components Lens Doublets Depolarisers Collimators Metal Optics Diffractive Optical Elements - Holographic Lenses Laser Scanning Systems Fibre Delivery Systems Liquid Lenses Graded-index Lenses Conclusions 127 References 128 Laser Cutting, Drilling and Piercing Introduction The Process - How It Is Done Laser Drilling and Piercing Introduction Drilling Process Variations Percussion and Single- or Double-shot Drilling Drilling Ceramic-coated Material 149

4 3.3.5 Trepanning Helical Trepanning Applications of Laser Drilling Monitoring the Drilling Process Methods of Cutting Vaporisation Cutting/Drilling Fusion Cutting - Melt and Blow Reactive Fusion Cutting Controlled Fracture Scribing Cold Cutting Laser-assisted Oxygen Cutting - the LASOX Process Theoretical Models of Cutting Practical Performance Beam Properties Transport Properties Gas Properties Material Properties Practical Tips Examples of Applications of Laser Cutting Die Board Cutting Cutting of Quartz Tubes Profile Cutting Cloth Cutting Aerospace Materials Cutting Fibre Glass Cutting Kevlar Prototype Car Production Cutting Alumina and Dielectric Boards Furniture Industry Cutting Paper Flexographic Print Rolls Cutting Radioactive Materials Electronics Applications Scrap Recovery Laser Machining Shipbuilding The Laser Punch Press Manufacture of Bikes and Tubular Structures Cutting and Welding of Railcars Costed Example Process Variations Arc-augmented Laser Cutting Hot Machining Future Developments Higher-powered Lasers 191 sfi

5 Additional Energy Sources Improved Coupling Smaller Spot Size Increased Drag Increased Fluidity Worked Example of Power Requirement 192 References 193 Laser Welding Introduction Process Arrangement Process Mechanisms - Keyholes and Plasmas Operating Characteristics Power Spot Size and Mode Polarisation Wavelength Speed Focal Position Joint Geometries Gas Shroud and Gas Pressure Effect of Gas Pressure - Due to Velocity and Environment Effect of Material Properties Gravity Process Variations Arc-augmented Laser Welding Twin-beam Laser Welding Walking and Spinning Beams Laser Welding of Plastics Applications for Laser Welding in General Costed Example 244 References Theory, Mathematical Modelling and Simulation Introduction What is a Model? Derivation of Fourier's Second Law Analytical Models with One-dimensional Heat Flow Analytical Models for a Stationary Point Source The Instantaneous Point Source The Continuous Point Source Sources Other than Point Sources Analytical Models for a Moving Point Source Alternative Surface Heating Models The Ashby-Shercliffe Model: The Moving Hypersurface Line Source 264

6 5.6.2 The Davis et al. Model: The Moving Gaussian Source Analytical Keyhole Models - Line Source Solution Line Source on the Axis of the Keyhole Line Source Around the Surface of a Cylinder: One-dimensional Transient Model for Cylindrical Bodies Analytical Moving Point-Line Source Three-dimensional Models Three-dimensional Model for a Semi-infinite Plate Three-dimensional Transient Model for Finite Slabs Numerical Modelling Three-dimensional Thermal Model Flow Within the Melt Pool - Convection Pool Shape Some Model Results Effect of Flow on Surface Deformation Model for Flow with Vaporisation Mass Additions - Surface Alloying and Cladding Modelling Laser Ablation Semiquantitative Models Conclusions 288 References 292 Laser Surface Treatment Introduction Laser Heat Treatment Heat Flow Mass Flow by Diffusion Mechanism of the Transformation Process Properties of Transformed Steels Laser Surface Melting Solidification Mechanisms Style of Solidification Laser Surface Alloying Process Variations Applications Laser Cladding Laser Cladding with Preplaced Powder Blown Powder Laser Cladding Applications Particle Injection Laser-assisted Cold Spray Process Surface Texturing Enhanced Electroplating Laser Chemical Vapour Deposition Laser Physical Vapour Deposition Noncontact Bending 335

7 6.13 Magnetic Domain Control Laser Cleaning and Paint Stripping Surface Roughening Scabbling Micromachining Laser Marking Shock Hardening Conclusions 342 References 342 Rapid Prototyping and Low-volume Manufacture Introduction Range of Processes Styles of Manufacture Classification of Rapid Prototyping Techniques by Material Computer Aided Design File Manipulation Layered Manufacturing Issues General Stair Stepping Layer Thickness Selection Accuracy Part Orientation Support Structures Individual Processes Stereolithography Selective Laser Sintering Laminated-object Manufacture Laser Direct Casting or Direct Metal Deposition (DMD) Rapid Manufacturing Technologies Silicone Rubber Moulding Investment Casting Sand Casting Laser Direct Casting Rapid Prototyping Tooling Applications Conclusions 367 References 368 Laser Ablative Processes - Macro- and Micromachining Introduction Basic Mechanisms During Short Radiant Interactions Thermal.Models Nonthermal Models Case 2: Nanosecond Pulse Impact Case 3: Ultrashort Pulses Applications 379

8 8.5.1 Low-energy Pulses (Less than 150 nj) Medium-energy Pulses ( nj) High-energy Pulses (More than 500 nj) Summary 385 References Laser Bending or Forming Introduction The Process Mechanisms The Thermal Gradient Mechanism The Point Source Mechanism The Buckling Mechanism The Upsetting Mechanism Laser-induced Shock Bending Theoretical Models Models for the Thermal Gradient Mechanism The Buckling Mechanism Model The Upsetting Mechanism Model Operating Characteristics Effect of Power Effect of Speed - "Line Energy" Effect of Material Effect of Thickness - Thickening at the Bend Effect of Plate Dimensions - Edge Effects Effect of the Number of Passes Applications Conclusions 413 References Laser Cleaning Introduction Mechanisms of Laser Cleaning Selective Vaporisation Spallation Transient Surface Heating Evaporation Pressure Photon Pressure Ablation (Bond Breaking) Dry and Steam Laser Cleaning Angular Laser Cleaning Laser Shock Cleaning An Overview of the Laser Cleaning Process Practical Applications 436 References 437

9 11 Biomedical Laser Processes and Equipment Introduction Interaction of Laser Radiation with Biological Tissue Optical Properties of Biological Tissue Thermal Properties of Tissue Mechanical Properties of Tissue Tissue Heating Effects - Nonablative Heating Tissue Heating Effects - Ablation Tissue Heating - Nonlinear Interactions with a Laser Beam Medical Applications of Lasers Ophthalmology Surgical Applications Medical Diagnostics Absorption Techniques Spectral Techniques Visualisation Techniques Laser Manufacture of Medical Devices Laser Cutting Marking Wire Stripping Laser Welding Nanomedicine Scaffolds for Tissue Engineering Conclusion 480 References Laser Automation and In-process Sensing Automation Principles In-process Monitoring Monitoring Beam Characteristics Monitoring Worktable Characteristics Monitoring Process Characteristics In-process Control In-process Power Control In-process Temperature Control "Intelligent" In-process Control Conclusions 515 References Laser Safety The Dangers The Standards The Safety Limits Damage to the Eye Damage to the Skin Laser Classification 523

10 13.5 Typical Class 4 Safety Arrangements Where Are the Risks in a Properly Set Up Facility? Electrical Hazards Fume Hazards Conclusions 525 References 526 Epilogue Power Intensity Power Transmission Power Shaping Automation Beam Coherence Beam Spectral Purity Multiphoton Events Frequency-related Events Equipment Developments Unthought-of Concepts 532 Index 535