All structures large and small are subject to physical forces that affect their performance. From a wind turbine blade vibrating in an offshore gale, an aircraft experiencing turbulence during flight to machinery exposed to self-generated vibration, these forces test the integrity of structures.
Yet, while structures must be resilient and rigid, over-engineering them can be both unnecessary and costly – especially when weight is an issue. And some structures, such as engine mounts, must not be too rigid. They must absorb vibration in order to maximize comfort.
Understanding how structures behave in service enables engineers to optimize their designs, monitor structural integrity, and maximize performance.
Structural dynamics is about the characterization of structural properties and the behaviour of structures. Structural properties are expressed in a set of modal parameters, each consisting of a mode shape with an associated natural (resonance) frequency and damping value. The modal parameters are derived from a mathematical model describing the relationship between the inputs and outputs and can be obtained using classical modal analysis or operational modal analysis (OMA).
In classical modal analysis, the structure is excited using impact hammers or modal exciters (modal shakers), whereas in operational modal analysis, natural excitation is used. In both cases, the response is typically measured using accelerometers.
Determining how shocks affect a structure is a special type of structural characterization. For this purpose, the shock response spectrum (SRS) calculated from transients in the time domain is used.
Structural behaviour is observed using techniques such as operating deflection shapes (ODS) analysis for determining the vibration patterns of structures under various operating conditions or using permanent structural health monitoring (SHM) to follow the structural state continuously and determine the required health management of the structure.
Integrating test and simulation
Structures are often designed using finite element (FE) models, and their geometry models and results predictions are very useful for optimizing the tests. Importing detailed FE models not only allows you to create simpler test models that are highly accurate, but also helps you to define optimal excitation and response DOFs to get the best possible test results. FE predictions can be correlated with the test results, and the test data can be imported back into the simulation tools for updating the FE models.
Recorded webinar: Introduction to Structural Dynamics Measurements and Analysis
Shock Response Spectrum (SRS)
A single transient shock event such as pyroshock or a structural impact can damage components in a structural system.
Classical modal analysis
In classical modal analysis, a model of a structure’s dynamic properties is obtained by exciting the structure with measurable forces and determining the response/excitation ratio.
Operational Modal Analysis (OMA)
Operational modal analysis (OMA) is used instead of classical modal analysis for accurate modal identification under actual operating conditions, and in situations where it is difficult or impossible to artificially excite the structure.
FEA - Test Integration
Finite element analysis (FEA) is a core discipline in structural dynamics. Integrating testing and FEA helps to cut development costs, reduces the number of physical prototypes, and shortens the time from concept to production.
Ground Vibration Testing (GVT)
Aircraft ground vibration testing (GVT) is used to determine the modal parameters of the complete aircraft and is typically performed very late in the development process.
Operating Deflection Shapes (ODS)
Operating deflection shapes (ODS) analysis is a very versatile application for determining the vibration patterns of machinery and structures under various operating conditions.
Structural Health Monitoring (SHM)
As structures degrade over time due to use, harsh environmental conditions and accidental events, Structural Health Monitoring becomes critical.
Structural Dynamics System
Our structural dynamics system enable highly efficient workflows for structural excitation and analysis - enabling you to go from test planning to final report with minimal effort.