Part 1 Fundamentals of Laser Processing ........................ 1
1 Basics of Lasers ............................................. 3
1.1 Introduction ............................................ 3
1.2 Nature of Electromagnetic Radiation ..................... 3
1.3 Laser Operation Mechanism ............................... 6
1.3.1 Population Inversion ............................. 6
1.3.2 Stimulated Emission .............................. 8
1.3.3 Amplification .................................... 9
1.4 Properties of Laser Radiation .......................... 13
1.4.1 Monochromaticity ................................ 13
1.4.2 Collimation ..................................... 15
1.4.3 Beam Coherence .................................. 16
1.4.4 Brightness or Radiance .......................... 17
1.4.5 Focal Spot Size ................................. 17
1.4.6 Transverse Modes ................................ 18
1.4.7 Temporal Modes .................................. 20
1.4.8 Frequency Multiplication ........................ 22
1.5 Types of Industrial Lasers ............................. 23
1.5.1 Solid-State Lasers .............................. 24
1.5.2 Gas Lasers ...................................... 25
1.5.3 Semiconductor Lasers ............................ 27
1.5.4 Liquid Dye Lasers ............................... 31
2 Laser Materials Interactions ................................ 34
2.1 Introduction ........................................... 34
2.2 Absorption of Laser Radiation .......................... 34
2.3 Thermal Effects ........................................ 40
2.3.1 Heating ......................................... 40
2.3.2 Melting ......................................... 43
2.3.3 Vaporization .................................... 45
2.3.4 Important Considerations for Thermal Analysis ... 50
2.4 Vapor Expansion and Recoil Pressures ................... 55
2.5 Plasma Formation ....................................... 59
2.6 Ablation ............................................... 61
Part II Laser Machining ....................................... 67
3 Manufacturing Processes: An Overview ........................ 69
3.1 Introduction ........................................... 69
3.2 Manufacturing Processes ................................ 69
3.2.1 Casting Processes ............................... 70
3.2.2 Forming Processes ............................... 71
3.2.3 Joining Processes ............................... 74
3.2.4 Machining Processes ............................. 75
3.3 Lasers in Manufacturing ................................ 79
3.3.1 Laser Casting ................................... 79
3.3.2 Laser Forming/Shaping ........................... 80
3.3.3 Laser Joining ................................... 83
3.3.4 Laser Machining ................................. 84
3.4 Selection of Manufacturing Processes ................... 85
3.4.1 Properties of Materials ......................... 85
3.4.2 Geometrical Complexity of Product ............... 88
3.4.3 Quality Parameters .............................. 90
3.4.4 Manufacturing Economics ......................... 92
4 Laser Drilling .............................................. 97
4.1 Introduction ........................................... 97
4.2 Laser Drilling Approaches .............................. 98
4.3 Melt Expulsion During Laser Drilling ................... 99
4.4 Analysis of Laser Drilling Process .................... 103
4.5 Quality Aspects ....................................... 117
4.6 Practical Considerations .............................. 124
4.6.1 Effect of Laser Parameters ..................... 125
4.6.2 Effect of Focusing Conditions .................. 128
4.6.3 Effect of Assist Gas Type, Gas Pressure, and
Nozzle Design .................................. 129
4.7 Laser Drilling Applications ........................... 134
4.7.1 Drilling of Cooling Holes ...................... 134
4.7.2 Drilling of Diamonds ........................... 136
4.7.3 Microdrilling .................................. 136
4.8 Advances in Laser Drilling ............................ 137
5 Laser Cutting .............................................. 144
5.1 Introduction .......................................... 144
5.2 Laser Cutting Approaches .............................. 145
5.2.1 Evaporative Laser Cutting ...................... 146
5.2.2 Laser Fusion Cutting ........................... 152
5.2.3 Reactive or Oxygen-Assisted Laser Cutting ...... 158
5.2.4 Controlled Fracture Technique .................. 167
5.3 Quality Aspects ....................................... 171
5.3.1 Striations ..................................... 171
5.3.2 Dross .......................................... 176
5.3.3 Heat-Affected Zone ............................. 179
5.4 Practical Considerations .............................. 183
5.4.1 Effect of Laser Type ........................... 183
5.4.2 Effect of Laser Power .......................... 183
5.4.3 Effect of Optical System ....................... 186
5.4.4 Effect of Nozzle Parameters .................... 187
5.4.5 Effect of Assist Gas Type ...................... 190
5.5 Laser Cutting of Various Materials .................... 193
5.5.1 Metallic Materials ............................. 193
5.5.2 Polymers ....................................... 197
5.5.3 Ceramics and Glasses ........................... 198
5.6 Laser-Cutting Applications ............................ 200
5.7 Advances in Laser Cutting ............................. 200
5.7.1 Laser Cutting Assisted by Additional Energy
Sources ........................................ 200
5.7.2 Underwater Cutting ............................. 201
5.7.3 Laser Cutting of Composites and Laminates ...... 202
6 Three-Dimensional Laser Machining .......................... 207
6.1 Introduction .......................................... 207
6.2 Laser-Assisted Machining .............................. 207
6.2.1 LAM Process .................................... 208
6.2.2 Analysis of LAM Process ........................ 209
6.2.3 LAM Process Results ............................ 215
6.3 Laser Machining ....................................... 225
6.3.1 Machining Using Single Laser Beam .............. 225
6.3.2 Machining Using Intersecting Laser Beams ....... 233
6.4 Applications of Three-Dimensional Laser Machining ..... 243
7 Laser Micromachining ....................................... 247
7.1 Introduction .......................................... 247
7.2 Laser Micromachining Mechanisms ....................... 247
7.2.1 Laser Ablation ................................. 248
7.2.2 Laser-Assisted Chemical Etching ................ 260
7.3 Laser Micromachining Techniques ....................... 265
7.3.1 Direct Writing Technique ....................... 265
7.3.2 Mask Projection Technique ...................... 267
7.3.3 Interference Technique ......................... 268
7.3.4 Combined Techniques ............................ 270
7.4 Laser Micromachining Applications ..................... 271
7.4.1 Microvia Drilling .............................. 271
7.4.2 Drilling of Inkjet Nozzle Holes ................ 272
7.4.3 Resistor Trimming .............................. 273
7.4.4 Laser Scribing and Dicing ...................... 276
7.4.5 Laser Marking and Engraving .................... 277
7.4.6 Biomedical Applications ........................ 280
7.4.7 Thin Film Applications ......................... 282
7.4.8 Fuel Injector Drilling ......................... 283
7.4.9 Stripping of Wire Insulation ................... 285
Part III Laser Fabrication .................................... 289
8 Laser Forming .............................................. 291
8.1 Introduction .......................................... 291
8.2 Laser Forming Processes ............................... 292
8.2.1 Bending or Temperature Gradient Mechanism ...... 294
8.2.2 Buckling Mechanism ............................. 296
8.2.3 Upsetting Mechanism ............................ 299
8.3 Analysis of Laser Forming Processes .................... 299
8.3.1 Temperature Gradient Mechanism ................. 300
8.3.2 Buckling Mechanism ............................. 308
8.4 Practical Considerations .............................. 312
8.4.1 Processing Parameters .......................... 312
8.4.2 Bending Rate and Edge Effects .................. 323
8.4.3 Laser Forming Strategies and Control ........... 329
8.4.4 Microstructure and Properties of Laser-Formed
Components ..................................... 337
8.5 Laser Forming Applications ............................ 341
8.5.1 Correction of Bending Angles ................... 341
8.5.2 Laser Forming of Complex Shapes ................ 341
8.5.3 Rapid Prototyping .............................. 343
8.5.4 Flexible Straightening of Car Body Shells ...... 343
8.5.5 Microfabrication ............................... 344
8.5.6 Laser Forming in Space ......................... 344
8.6 Advances in Laser Forming ............................. 344
8.6.1 Laser Forming of Tubes ......................... 344
8.6.2 Laser Forming with Preload ..................... 347
8.6.3 Laser Forming with Two Beams ................... 348
8.6.4 Laser Forming of Composite Materials ........... 349
9 Laser-Based Rapid Prototyping Processes .................... 353
9.1 Introduction .......................................... 353
9.2 Basics of Rapid Prototyping Processes ................. 353
9.3 Classification of Rapid Prototyping Processes ......... 355
9.3.1 Liquid-Based RP Processes ...................... 356
9.3.2 Powder-Based RP Processes ...................... 357
9.3.3 Solid-Based RP Processes ....................... 358
9.3.4 Concept Modelers ............................... 359
9.4 Laser-Based Rapid Prototyping Processes ............... 359
9.4.1 Stereolithography .............................. 359
9.4.2 Selective Laser Sintering ...................... 379
9.4.3 Laminated Object Manufacturing (LOM) ........... 397
9.4.4 Laser Engineered Net Shaping (LENS) ............ 402
9.5 Applications of Rapid Prototyping Processes ........... 405
9.5.1 Applications in Rapid Prototyping .............. 406
9.5.2 Applications in Rapid Tooling .................. 407
9.5.3 Applications in Rapid Manufacturing ............ 407
9.5.4 Medical Applications ........................... 407
10 Laser Welding .............................................. 412
10.1 Introduction .......................................... 412
10.2 Laser Welding Process ................................. 412
10.3 Analysis of Laser Welding Process ..................... 415
10.4 Quality Aspects ....................................... 427
10.4.1 Porosity ....................................... 427
10.4.2 Cracking ....................................... 429
10.4.3 Heat-Affected Zone ............................. 431
10.4.4 Mechanical Properties of Laser Welds ........... 432
10.5 Practical Considerations .............................. 433
10.5.1 Effect of Laser Parameters ..................... 433
10.5.2 Effect of Focusing Conditions .................. 435
10.5.3 Effect of Shielding Gas ........................ 435
10.5.4 Effect of Welding Speed ........................ 437
10.5.5 Joint Configurations ........................... 437
10.6 Laser Welding of Various Materials .................... 438
10.6.1 Metallic Materials ............................. 438
10.6.2 Ceramics ....................................... 439
10.6.3 Polymers ....................................... 440
10.6.4 Composites ..................................... 440
10.6.5 Dissimilar Materials ........................... 442
10.7 Advances in Laser Welding ............................. 443
10.7.1 Arc-Augmented Laser Welding .................... 443
10.7.2 Multibeam/Dual-Beam Laser Welding .............. 443
10.7.3 Laser Welding of Tailor-Welded Blanks .......... 444
Part IV Special Topics in Laser Processing .................... 449
11 Laser Interference Processing .............................. 451
11.1 Introduction .......................................... 451
11.2 Theory of Interference ................................ 451
11.3 Interferometry for Surface Processing of Materials .... 453
11.3.1 Laser and Materials Aspects .................... 454
11.3.2 Interferometer Design Aspects .................. 456
11.4 Applications of Laser Interference Processing ......... 459
11.4.1 Crystallization and Structuring of
Semiconductor Films ............................ 459
11.4.2 Structuring of Monolayer and Multilayer
Metallic Films ................................. 464
11.4.3 Structuring of Biomaterials .................... 472
12 Laser Shock Processing ..................................... 477
12.1 Introduction .......................................... 477
12.2 Fundamentals of Laser Shock Processing ................ 477
12.3 Analysis of Laser Shock Processing Process ............ 480
12.4 Processing Parameters ................................. 484
12.4.1 Effect of Laser Intensity ...................... 484
12.4.2 Effect of Pulse Duration ....................... 484
12.4.3 Effect of Temporal Pulse Shape ................. 486
12.4.4 Effect of Laser Wavelength ..................... 486
12.4.5 Effect of Spatial Energy Distribution .......... 488
12.4.6 Effect of Coating Material ..................... 489
12.5 Mechanical Effects During Laser Shock Processing ...... 491
12.6 Microstructure Modification During Laser Shock
Processing ............................................ 493
12.7 Applications of Laser Shock Processing ................ 496
13 Laser Dressing of Grinding Wheels .......................... 499
13.1 Introduction .......................................... 499
13.2 Grinding Process and Need of Wheel Dressing ........... 499
13.3 Laser-Based Wheel Dressing Techniques ................. 502
13.3.1 Laser-Assisted Dressing ........................ 502
13.3.2 Laser Dressing ................................. 506
13.3.3 Recent Approaches of Laser Dressing ............ 511
14 Lasers Processing in Medicine and Surgery .................. 522
14.1 Introduction .......................................... 522
14.2 Laser-Tissue Interactions ............................. 522
14.2.1 Photothermal Interactions ...................... 526
14.2.2 Photochemical Interactions (Photoablation) ..... 529
14.2.3 Photodisruptive Interactions ................... 532
14.3 Laser Applications in Medicine and Surgery ............ 534
14.3.1 Lasers in Ophthalmology ........................ 534
14.3.2 Lasers in Dermatology .......................... 540
14.3.3 Lasers in Otolaryngology-Head and Neck
Surgery ........................................ 545
14.3.4 Lasers in Angioplasty .......................... 545
14.3.5 Lasers in Osteotomy ............................ 547
14.3.6 Lasers in Dentistry ............................ 547
Index ......................................................... 555
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