Development of an Optical Displacement Transducer for Routine Testing of Asphalt Concrete

Tomer Hamam, Eyal Levenberg, Lihi Zelnik-Manor

Research output: Contribution to journalJournal articleResearchpeer-review


Routine mechanical characterization of asphalt concrete is performed under small-strain levels with on-specimen linear variable displacement transducers (LVDTs) as deformation measuring devices. An optical LVDT was conceptually proposed and evaluated in this study to serve as a viable noncontact alternative to physical LVDTs. The envisioned device consists of a pair of low-end low-resolution grayscale cameras, each monitoring a virtual gauge point, i.e., a small untreated surface area of the tested specimen. The gauge length is the distance between the two virtual gauge points, and the sought-after information is their differential in-plane translation. Digital image correlation techniques were employed for the measurement, operated on the natural material texture without requiring speckle coating. As a first step toward evaluating the concept, the study explored both the precision and the accuracy that may be achieved with one low-resolution image sensor. A calibration scheme was also offered for introducing object-scale dimensions into the analysis. From this predevelopment
study it is concluded that the envisioned optical LVDT is viable, rendering the idea worthy of consideration
Original languageEnglish
JournalJournal of Materials in Civil Engineering
Number of pages11
Publication statusPublished - 2016
Externally publishedYes


  • Asphalt Concrete
  • Material Characterization
  • Linear Variable Displacement Transducer (LVDT)
  • Digital Image Correlation
  • Precision and Accuracy


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