Advanced Method Revealed for Non-Contact Measurement of Mechanical Vibrations and Displacements Using Deferred Moiré Patterns

A groundbreaking technique for measuring mechanical vibrations and displacements without physical contact has been introduced in a recent paper published in “Advances in Mechanical Engineering.” Termed “deferred moiré patterns,” this method captures vibrations using a video record rather than simultaneous observation during field measurements. The innovation lies in filming a vibrating grid attached to an object, enabling subsequent analysis.
Central to this approach are two principles: moiré magnification and moiré phase. The magnification ensures the precise measurement of minute quantities, even below pixel level. At the same time, the phase of a periodic function corresponds to its displacement along an axis. By assessing phase differences, this technique effectively measures longitudinal displacement, magnified through the physical properties of moiré patterns.
The method utilizes a planar, periodical grid with black and white bands, often several millimeters or centimeters wide. Typically printed on paper or engraved on metal, this grid is affixed to the vibrating object for measurement purposes.
What sets this method apart is its reliance on regular photographic equipment; moiré patterns aren’t directly photographed during fieldwork. Calibration isn’t necessary during field measurements, as only photographs or videos of the grid attached to the object are taken. The measurements are conducted in the laboratory, generating moiré fringes and calculating phase differences.
The practical implications of this innovation extend to structural analysis. Cracks are created by structural elements over time, which change the natural vibration of the structure. Abnormal structural conditions can be identified by comparing the frequency of these vibrations and the decay rate. This comparison is essential during the construction phase and allows the detection of deviations from the required stability before completion. This research addresses a primary challenge: the distinction between normal and abnormal vibrations.
This research will be an essential step forward for non-contact measurement techniques in structural analysis, the novelty of which has been confirmed in conferences, and this invention has been patented. You can have access to the paper through link bellow.