Structural health monitoring
As per WH Monitoring philosophy, any oscillation within an object generates an energy wave, which passes through the object’s structure. This principle is similar to wave generation as per fluid mechanics when offshore waves are generated due to the energy transferred from wind or earthquakes. Each wave consists of many sinusoidal waves of various periods and phases. All waves will spread in all directions with different phases.
Similarly, the energy wave in structures spreads over an object and reaches measurement point with some time lag (i.e. it takes time for the wave to travel from source to the measurement point). Energy distribution within structure, magnitudes of kinetic, potential and total energies at the point of interest will depend on the following aspects:
- Location and magnitude of the oscillation;
- Material properties and geometry of the structure where the energy wave passes.
WH Monitoring believes that the energy distribution within the structure can be used as extremely powerful tool to assess performance of the engine and condition of the structure (e.g. risk of corrosion or fatigue).
Kinetic and potential energy are directly proportional to the acceleration. On the other hand, total energy would be equal to the sum of kinetic and potential energy. WHM technology allows measuring each type of the energy separately.
If structure is intact, the total energy remains the same for constant magnitude of the oscillation (e.g. power of the engine). However, distribution and direction of the kinetic and potential energies would indicate offsets in source location.
If the total energy changes for constant magnitude of oscillation, it would indicate that the structure is not intact (e.g. the defect started occurring).
Besides that, the three-dimensional response characteristics can be used to calculate the stresses in three dimensions at the measurement point using Hook’s Law with appropriate Poisson’s coefficient. The stress calculation approach adopted by WH Monitroing provides with a full picture of structural response in three-dimensions which cannot be obtained with traditional measurement and post-processing methods. This data can be presented as:
- Stress-strain vectors;
- Plots showing response, kinetic and potential energy;
- Tabulated or graphical stress-strain amplitudes for different excitation frequencies;
- Three-dimensional stress-strain mesh models, similar to those produced by FE software.