Gary Schajer

Gary Schajer

Professor

P.Eng., B.A., M.A. (Cambridge), M.S., Ph.D. (Berkeley), Eur. Ing., C.Eng., FIMechE, FASME.

phone: (604) 822-6004
email: schajer@mech.ubc.ca
website:  Renewable Resources Laboratory
office: CEME 2055

Research Interests

  • 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.

Teaching Interests

  • Mechanics of Materials
  • Electronics and Instrumentation
  • Mechanical Design

Selected Publications

Papers:

  • Schajer, G.S. “Circumferential Rosette Design for Extended Depth Hole-Drilling Residual Stress Measurements”. Experimental Mechanics, Vol.60, No.9, pp.1265–1274, 2020.
  • Schajer, G.S. “Compact Calibration Data for Hole-Drilling Residual Stress Measurements in Finite-Thickness Specimens. Experimental Mechanics, Vol.60, No.5, pp.665–678, 2020.
  • Heikkinen, J.J., Schajer, G.S. “A Geometric Model of Surface Motion Measurement by Objective Speckle Imaging”. Optics and Lasers in Engineering, Vol.124, 2020.
  • Pan, Q., Schajer, G.S. “Linear Sensor Arrangement for Softwood Grain Angle Measurements by Directional Reflection”. ASME Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems, Vol.2, No.1, pp 011003-011003-6, 2019.
  • Pokharna, H., Schajer, G.S. “Quasi Single-frame Measurements with Phase-stepped ESPI”. Optics and Lasers in Engineering, Vol.121, pp.181-188, 2019.
  • Pan, Q., Schajer, G.S. “Two-line Spatial Reflection Method for Measuring Wood Grain Direction”. Forest Products Journal, Vol.68, No.4, pp.459-464, 2019.
  • Schajer, G.S. and Whitehead, P.S. “Hole-Drilling Method for Measuring Residual Stress.” Morgan & Claypool, Vermont, USA. 186pp, 2018.
  • Angus, E., An, Y., Schajer, G.S. “Computed Tomography of Logs with Motion Compensation”. ASME Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems, Vol.1, No.3, pp. 031002-031002-9, 2018.
  • Heikkinen, J.J., Schajer, G.S. “Low-Coherence Light Source Design for ESPI In-plane Displacement Measurements”, Optics and Lasers in Engineering, Vol.100, pp.77-81, 2018.
  • Ma, T. Schajer, G.S., Inagaki, T., Pirouz, Z., Tsuchikawa, S. “Optical Characteristics of Douglas fir at Various Densities, Grain Directions and Thicknesses Investigated by Near-infrared Spatially Resolved Spectroscopy (NIR-SRS)”. Holzforschung, Vol.72, No.9, pp.789-796, 2018.
  • Heikkinen, J.J., Schajer, G.S. “Full-Field High-Strain Gradient Evaluation from Wrapped ESPI Data Using Phasors”, Experimental Mechanics, Vol.57, No.5, pp.665–674, 2017.
  • Harrington, J.S., Schajer, G.S. “Measurement of Structural Stresses by Hole-Drilling and DIC”, Experimental Mechanics, Vol.57, No.4, pp.559-567, 2017.
  • Gubbels, W.L., Schajer, G.S. “Development of 3-D Digital Image Correlation Using a Single Color-Camera and Diffractive Speckle Projection”, Experimental Mechanics, Vol.56, No.8, pp.1327-1337, 2016.
  • Schajer, G.S., Sutton, D.B. “Identification of 3D Wood Grain Angle by Directional Reflection Measurement”, Wood Material Science and Engineering, Vol.11, No.3, pp.170-175, 2016.
  • Schajer, G.S. “Wood Machining: Past Achievements, Present Capabilities, Future Opportunities”, Wood Material Science and Engineering, Vol.11, No.3, pp.127-134, 2016.
  • Schajer, G.S., “IWMS Special Issue”, Wood Material Science and Engineering, Vol.11, No.3, p.126, 2016.
  • Richoz, G.L., Schajer, G.S “Simultaneous Two-axis Shearographic Interferometer Using Multiple Wavelengths and a Color Camera”, Optics and Lasers in Engineering, Vol.77, pp.143-153, 2016.
  • Richoz, G.L., Schajer, G.S. “Simultaneous Phase-Stepping Shearography Measurements Using Multiple Wavelengths and a Color Camera”, Experimental Mechanics, Vol.55, No.6, pp.1165-1174, 2015.
  • An, Y., Schajer, G.S. “Cone-Beam Feature-Specific CT Log Scanning”, Experimental Mechanics, Vol.55, No.3, pp.509-518, 2015.
  • Schajer, G.S., Zhang, Y., Melamed, S. “In-plane ESPI using an achromatic interferometer with low-coherence laser source”, Optics and Lasers in Engineering, Vol.67, pp.116-121, 2015.
  • An, Y., Schajer, G.S. “Cone-Beam Feature-Specific CT Log Scanning”, Experimental Mechanics, Vol.55, No.3, pp.509-518, 2015.
  • An, Y., Schajer, G.S. “Geometry-based CT scanner for measuring logs in sawmills”, Computers and Electronics in Agriculture, Vol.105, p.66-73, 2014.
  • Schajer, G.S., Abraham, C. “Residual Stress Measurements in Finite-Thickness Materials by Hole-Drilling”. Experimental Mechanics, Vol.54, No.9, pp.1515-1522, 2014.
  • An, Y., Schajer, G.S. “Feature-Specific CT Measurements for Log Scanning: Theory and Application”, Experimental Mechanics, Vol.54, No.5, pp.753-762, 2014.
  • Schajer, G.S. “Practical Residual Stress Measurement Methods.” Wiley, Chichester, UK, 320pp., 2013.

Books:

  • G.S. Schajer, and Whitehead, “Hole-drilling method for measuring residual stresses,” Synthesis SEM Lectures on Experimental Mechanics, 1(1), pp.1-186, 2018.
  • G. S. Schajer, Practical Residual Stress Measurement Methods. John Wiley & Sons, 2013.
  • S. Bossuyt, G.S. Schajer, and A. Carpinteri, Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems, Volume 9: Proceedings of the 2015 Annual Conference on Experimental and Applied Mechanics. Springer, 2015.

For a more extensive list of publications, please visit:
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