Modal Analysis and Operation Deflection Shape (ODS)
In addition to its vibration analysis and balancing capabilties, the VIBXPERT features Modal Analysis and Operation Deflection Shape (ODS).
Standard data collection serves as an excellent base for identifying developing machinery faults. However modal measurements are typically used to investigate the natural frequencies of machinery and supporting structures. Modal analysis measures the natural frequencies, mode shapes and damping of structural natural frequencies. Where vibration analysis only measures the response of the machine or structure to unknown forces, modal analysis can be used to determine these dynamic forces.
A high percentage of machinery and structural vibration problems are caused by natural frequencies excited to resonate by rotating machinery.
A modal test involves measuring the test structure or machine’s response to a controlled input force. The force is typically applied with an instrumented hammer also called a modal hammer (available as an option). The response of the test structure is measured with accelerometers at various points on the structure. For large tests, several accelerometers are used and moved to the many test points on the structure. After acquisition the data can be exported to optionally available software programs to develop a mathematical model which describes the dynamic properties of the test structure. Finite elements can then be used to calculate the effect of adding or removing mass, adding plate stiffeners, damping, tuned vibration absorbers, etc.
Vibration data is measured at various points on the structure or machine in operation and then the data can be mapped to a 3D computer model to test the structure. There are programs available where the model can be animated at any of the frequencies at which the test structure was vibrating. The animation allows examination of how the structure or it components are vibrating or moving. This motion may include flexing, bending, twisting or relative motion across interfaces such as bolted or riveted joints. The data can also be animated in the time domain.
Optionally available for:
Example of an ODS animation: Maximum displacement of a mounting platform.