Noncontact microstrain measurements in orthodontic wires.
A technique is presented that allows for highly sensitive and highly accurate measurements of microstrain in biomaterials. It is particularly useful for measuring strains in materials where the use of conventional extensometers or strain gauges is impracticable, such as reinforcement fibers and orthodontic wires and in hostile environments. The technique is based on the well known technique of observing translating laser speckle with a linear-array charge-coupled device (CCD) camera. However, it employs a relatively new data processing algorithm involving a two-dimensional frequency transform of the data. Advantages of the technique include: insensitivity to slow surface microstructure changes, insensitivity to zero-mean noise processes, compact design, modest resolution requirements, and the fact that it is truly noncontact. Strain rate measurements were made on an 0.028-gauge round stainless steel orthodontic wire as an example of this technique. The Young's modulus of the wire based on the speckle technique was 2.04 x 10(11) Nm(-2), which is very close to the textbook value.
Kirkpatrick
S J
SJ
Department of Oral Biology, University of Nebraska Medical Center, College of Dentistry, Lincoln 68583-0740, USA.
Duncan
D D
DD
D000465:Algorithms; D005583:Fourier Analysis; D007834:Lasers; D009969:Orthodontic Wires; D013499:Surface Properties; D013718:Tensile Strength