Comparison of DIC and LDV for practical vibration and modal measurements

Abstract

We compare laser Doppler vibrometry (LDV) and digital image correlation (DIC) for use in full-field vibration and modal testing. This was done using a simultaneously measured 3D displacement field on a flat 7-inch corner-supported metal plate using pseudorandom excitation via a shaker. We complete a detailed comparison between the techniques and discuss the pros and cons of each. The results show that either technique can be used for quantifying the modal information with the LDV providing better out-of-plane displacement resolution and equivalent in-plane resolution. The strain calculation is considered better in the DIC approach due to the direct tie to the surface displacements. While the LDV does not lose its place as the gold standard for modal testing, DIC has introduced a new and competitive approach that will have significant advantages in certain testing regimes.

A Space-Time PGD-DIC Algorithm:

“…The disadvantage is that the measurement resolution is, in general, not comparable with that of the tools mentioned above [18,5,32]. Special attention must therefore be paid to reducing measurement uncertainties when attempting to develop a new DIC method in this context.…”

“…Specifically, the authors generally use SDIC with high-speed cameras to analyze dynamic tests with a harmonic excitation [34,38,15], a shock [34,18] or a random excitation [34,18,39,5,32]. From full field displacement measurements, different mode shapes are extracted by using e.g.…”

“…From full field displacement measurements, different mode shapes are extracted by using e.g. Fourier analysis and modal curve fitting [34,32] or using lock-in amplifiers [15] in a post-processing phase. In [38], the authors use an a posteriori sinusoidal fitting method to increase the accuracy of the displacement measurement of fatigue crack growth tests.…”

Structural Low-Level Dynamic Response Analysis Using Deviations of Idealized Edge Profiles and Video Acceleration Magnification

“…Without additional mass on the surface of the measurement target, vision-based measurement devices rarely affect the natural properties of flexible or lightweight objects. Moreover, vision-based devices often have a flexible composition and provide relatively high spatial resolution in an efficient and automated manner [10].…”

Structural dynamic response analysis using deviations from idealized edge profiles in high-speed video

“…Compared with common noncontact methods, such as laser Doppler vibrometer, vision-based devices have flexible composition and provide relatively high spatial resolution. 7 The emergence of high-speed imaging sensors has increased the sampling frame rate of cameras considerably, providing more advantage in structural high frequency information observation than common commercial cameras. [8][9][10][11] Noises from frame interpolation are technically avoided from the source benefiting from a relatively high sampling rate, and subtle motion details can be recorded in a high-speed video file.…”