Modal analysis and other forms of vibration analysis are very important in both engineering design and failure analysis. To support this work, Innovative Test Solutions, Inc. has a range of equipment including: accelerometers, electro-dynamic shakers, and a digital holography system.
Digital Holography System
Our Digital Holography System has the capability to perform mode shaping for a wide range of frequencies and components.
The system allows you to identify and characterize vibration modes. The vibration modes show up as fringes on the turbine blade. These fringes are dark bands on the image that read like a topographical map showing areas of excitation. The software supplied with the system allows the operator to peak the amplitudes of the modes and take a snap shot of the mode shape.
The Modal Assurance Criteria (MAC):
Correlation of mode shapes can be achieved through the use of the MAC feature. MAC is a scalar value between zero and one representing the correlation between two mode shapes. A MAC value near one indicates a high degree of correlation or consistency between two mode shapes. In this case, the two mode shapes represent the same motion differing only by a complex modal scaler factor (MSF). The MSF can be used to scale the mode shapes to a common level for subsequent manipulations. This may include differencing the mode shapes to understand the variance or combining the mode shapes to improve the estimate.
The system can measures displacements at right angles to the line of sight. The resulting fringes measure thermal expansion or unidirectional strain. Time-lapse recordings can be used to collect data for stress relaxation studies.
Impact Hammer testing utilizes software to record the resonance response of a component to map modal frequencies. Our system is capable of obtaining modal frequencies up to 40 KHz on a range of different component shapes and sizes.