P.Eng., B.A., M.A. (Cambridge), M.S., Ph.D. (Berkeley), Eur. Ing., C.Eng., FCAE, FIMechE, FASME.
|website:||Renewable Resources Laboratory|
- Industrial Residual Stress Measurements
- Full-Field Optical Metrology
- X-Ray CT Log Scanning
Current Research Work
- Industrial Residual Stress Measurements: Residual (or “locked-in”) stresses in engineering components can have a profound effect on service performance, particularly fatigue life. Because of their locked-in nature, residual stresses are difficult to measure and evaluate. This research area is aimed at developing methods for measuring residual stresses that are suitable for industrial use. The work focuses on the hole-drilling method using both optical and strain-gage measurement techniques.
- Full-Field Optical Metrology: Digital images from modern electronic cameras open broad opportunities for a wide range of full-field optical measurements. Of particular interest here is the use of Electronic Speckle Pattern Interferometry (ESPI) and Digital Image Correlation (DIC) to identify material displacements, rotations, strains, surface shape and vibration modes. Such measurements are particularly interesting because they are “non-contact” and every pixel within the measured images provides an independent measurement. Taken together, the pixels simultaneously provide several handred thousand data that reveal fine details throughout the imaged area.
- X-Ray CT Log Scanning: Wood is a natural material that has a great diversity in its physical properties. To maximize the value of the products created in sawmills and to minimize the consumption of an important environmental resource, it is essential to use the available material in the most intelligent and effective way. This can be done by carefully measuring incoming logs, identifying their quality controlling features, and then selecting appropriate processing. Many important quality controlling features lie within the interior of the logs, where they cannot be seen by external inspection. This project focuses on the development of an X-ray CT scanner suitable for identifying these interior features. The scanner is fast to allow real-time operation and rugged for industrial use.
- Mechanics of Materials
- Electronics and Instrumentation
- Mechanical Design
- Y. An and G. S. Schajer, “Coarse-resolution cone-beam scanning of logs using Eulerian CT reconstruction. Part I: Discretization and algorithm,” in Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems, Volume 8, Springer, 2014, pp. 9–19.
- Y. An and G. S. Schajer, “Coarse-resolution cone-beam scanning of logs using Eulerian CT reconstruction. Part II: Hardware design and demonstration,” in Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems, Volume 8, Springer, 2014, pp. 21–29.
- Y. An and G. S. Schajer, “Geometry-based CT scanner for measuring logs in sawmills,” Computers and Electronics in Agriculture, vol. 105, pp. 66–73, 2014.
- G. S. Schajer, “Hole-Drilling Residual Stress Measurements,” Encyclopedia of Thermal Stresses, pp. 2280–2293, 2014.
- L. Bingleman and G. S. Schajer, “ESPI Measurements In the Presence of Large Lateral Displacements,” in Application of Imaging Techniques to Mechanics of Materials and Structures, Volume 4, Springer, 2013, pp. 179–187.
- S. Gao and G. S. Schajer, “ESPI Photoelastic Measurement of All In-Plane Stress Components,” in Imaging Methods for Novel Materials and Challenging Applications, Volume 3, Springer, 2013, pp. 423–432.
- G. S. Schajer and P. S. Whitehead, “Hole Drilling and Ring Coring,” Practical Residual Stress Measurement Methods, pp. 29–64, 2013.
- C. Abraham and G. S. Schajer, “Hole-drilling residual stress measurement in an intermediate thickness specimen,” in Experimental and Applied Mechanics, Volume 4, Springer, 2013, pp. 389–394.
- G. S. Schajer and C. O. Ruud, “Overview of Residual Stresses and Their Measurement,” Practical Residual Stress Measurement Methods, pp. 1–27, 2013.
- G. S. Schajer, Practical Residual Stress Measurement Methods. John Wiley & Sons, 2013.