Investigation of Nailed Timber Connections Using the Laser Interferometry Method

The paper presents an adapted methodology of laser holographic interferometry for an investigation of the stress-strain state of nailed timber connections. During the study the possibility of detecting local deformations in the connection were verified. The optimum conditions for fixing the samples and the loading ranges to ensure an optimal interference pattern were determined. An investigation of the peculiarities of the interaction between the elements and the stress-strain behavior of nailed timber connections was performed. The experimental data obtained on the stress-strain behavior of a nailed timber connection using the laser holographic interferometry method have sufficient repeatability between different series and can also be used as a criterion verification for a finite-element model.

Laser Interferometry Hologram Registration for Three-Dimensional Precision Measurements

A hologram registration method is developed for the laser holographic interferometry measurement of the 3D surface profile of objects which are larger than the field of view (FOV). The theory of laser holographic interferometry, including the phase-shifting and multiwavelength tuning, is described. The hologram registration without using targets is elaborated. The cross-correlation analysis is used to find the translation and overlapped regions, which determine the tilt and shift correction for data registration. The proposed method is validated using two examples with different approaches. The first example, a wheel hub, is smaller than the FOV and demonstrates only 0.1μm discrepancy of the surface flatness between the registered and standard measurements. The second example, an engine combustion deck surface, is larger than the FOV. The registered surface measurements are compared to that of coordinate measurement machine (CMM) with only 2.5% discrepancy of the peak-to-valley flatness. This data registration method enables the sub-μm precision and large depth of field (several centimeters) measurement of large size objects.

Laser Interferometry Hologram Registration for Three-Dimensional Precision Measurements

Laser holographic interferometry is an advanced precision measurement technology with sub-μm accuracy and large, over 17 mm, depth-of-field. The limitation of current laser holographic interferometry is the limited measurement area, which cannot be larger than the field of view (FOV). A hologram registration method without using targets is developed to overcome this problem. The theory of laser holographic interferometry, including the phase-shifting and multi-wavelength tuning, is described. The cross-correlation analysis is used to find the translation and overlapped regions, which determine the tilt and shift correction for data registration. The proposed method is validated using two examples with different approaches. The first example, a wheel hub, is smaller than the FOV and demonstrates only 0.1 μm discrepancy of the surface flatness between the registered and standard measurements. The second example, an engine combustion deck surface, is larger than the FOV. The registered surface measurements are compared to that of coordinate measurement machine (CMM) with only 2.5% discrepancy of the peak-to-valley flatness. This data registration method enables the sub-μm precision and large depth of field (several centimeters) measurement of large size objects.