Optical Methods
Fundamental issues in engineering, manufacturing, medical, and other fields are now being addressed and solved by automated and user-friendly optical methods. Optical methods can provide full-field displacement and deformation fields of structures under s
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Archie A.T. Andonian
Fundamental issues in engineering, manufacturing, medical, and other fields are now being addressed and solved by automated and userfriendly optical methods. Optical methods can provide full-field displacement and deformation fields of structures under static or dynamic conditions. Because of their noncontact nature, optical methods do not alter the response of the objects being studied. Thus, results obtained by optical methods represent reality and can be used to validate computational models. This chapter contains many examples drawn from research applications and has been prepared to give an overview of optical methods frequently used in industry and academia.
29.1 Photoelasticity ..................................... 824 29.1.1 Transmission Photoelasticity.......... 824 29.1.2 Reflection Photoelasticity .............. 827
29.2.2 Quantification of Dynamic 3-D Deformations and Brake Squeal ......................... 829 29.3 Shearography and Digital Shearography . 830 29.4 Point Laser Triangulation ...................... 831 29.5 Digital Image Correlation ...................... 29.5.1 Measurement of Strains at High Temperature ...... 29.5.2 High-Speed Spin Pit Testing .......... 29.5.3 Measurement of Deformations in Microelectronics Packaging ........
832 832 832
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29.6 Laser Doppler Vibrometry ...................... 834 29.6.1 Laser Doppler Vibrometry in the Automotive Industry ........... 834 29.6.2 Vibration Analysis of Electron Projection Lithography Masks ....................... 834 29.7 Closing Remarks ................................... 835
29.2 Electronic Speckle Pattern Interferometry 828 29.2.1 Calculation of Hole-Drilling Residual Stresses ... 828
29.8 Further Reading ................................... 836
Sending and retrieving light signals to convey information probably dates back to prehistoric times. The use of light in optical metrology, however, can be traced back to Thomas Young’s experiments in the early 1800s in which he demonstrated that very small dimensions can be measured by the interference of two coherent rays of light [29.1]. Over a period of two centuries numerous optical methods were developed based on fundamental principles of interferometry. Not many appreciated the importance of interferometry as a tool of metrology until Theodore Maiman demonstrated the first laser in 1960 [29.2]. For several decades optical methods were developed and used by scientists, primarily in academia and industrial laboratories. Many advances in the opti-
cal methods have been stimulated by the requirements of engineering research and challenging problems in areas such as fracture mechanics, materials science, nondestructive inspection, manufacturing, biomechanics, and miniaturized structures and sensors. Although, much of the development of new optical methods have been carried out by scientists in well-equipped laboratories, most of the applications are currently performed by engineers who are not specialized in optics but own the problems to be solved in their fields.
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