Photoacoustic Characterization of Materials
The basic principles of photoacoustic generation of ultrasonic waves and applications to materials characterization of solid structures are discussed in this chapter. Photoacoustic techniques are a subset of ultrasonic methods wherein stress waves are use
- PDF / 2,590,490 Bytes
- 32 Pages / 547.087 x 685.984 pts Page_size
- 93 Downloads / 256 Views
Photoacousti
27. Photoacoustic Characterization of Materials
The basic principles of photoacoustic generation of ultrasonic waves and applications to materials characterization of solid structures are discussed in this chapter. Photoacoustic techniques are a subset of ultrasonic methods wherein stress waves are used to obtain information about structural and material properties. In photoacoustic techniques, the ultrasound is typically generated using lasers, thereby enabling noncontact nondestructive characterization of the material properties of structures. Photoacoustic techniques have found application over a wide range of length scales ranging from macrostructures to nanometer-sized thin films and coatings. In this chapter, the basics of photoacoustics primarily as they relate to nondestructive characterization of solid materials are discussed. In Sect. 27.1, the basics of stress waves in solids is outlined. In Sect. 27.2, the process of photoacoustic generation is described. The major techniques of optical detection of ultrasound are then described in Sect. 27.3. The final section of this chapter is then devoted to some representative recent applications of photoacoustic characterization of materials. The objective here is to describe the basic principles involved, and to provide illustrative applications which take specific advantage of some of the unique features of the technique.
Photoacoustics (also known as optoacoustics, laser ultrasonics, etc.) deals with the optical generation and detection of stress waves in a solid, liquid or gaseous medium. Typically, the technique uses modulated laser irradiation to generate high-frequency stress waves (ultrasonic waves) by either ablating the medium or through rapid thermal expansion. The resulting stress
27.1 Elastic Wave Propagation in Solids ......... 27.1.1 Plane Waves in Unbounded Media . 27.1.2 Elastic Waves on Surfaces .............. 27.1.3 Guided Elastic Waves in Layered Media ......................... 27.1.4 Material Parameters Characterizable Using Elastic Waves
770 771 772 774 776
27.2 Photoacoustic Generation ..................... 27.2.1 Photoacoustic Generation: Some Experimental Results............ 27.2.2 Photoacoustic Generation: Models . 27.2.3 Practical Considerations: Lasers for Photoacoustic Generation ........
777
27.3 Optical Detection of Ultrasound ............. 27.3.1 Ultrasonic Modulation of Light ....... 27.3.2 Optical Interferometry................... 27.3.3 Practical Considerations: Systems for Optical Detection of Ultrasound .
783 783 785
777 780 783
789
27.4 Applications of Photoacoustics............... 789 27.4.1 Photoacoustic Methods for Nondestructive Imaging of Structures ................................ 789 27.4.2 Photoacoustic Methods for Materials Characterization ........ 793 27.5 Closing Remarks ................................... 798 References .................................................. 798
wave packets are also typically measured using optical probes. Photoacoustics therefore provides a noncontact way of
Data Loading...
