In today’s engineering practice, Finite Element Models are used to simulate the behavior of structures, and to analyse and solve real life engineering problems. For example, the goal can be to investigate vibration levels of a structure, to get insight in what causes an excessive dynamic response, and to modify the structure’s dynamic characteristics to attenuate the response at problematic frequencies. The value of these simulations and analyses is determined mainly by the quality of the Finite Element Models.
Before a product is physically build, a CAD model is created - defining the products dimensions – which is used later on to build a Finite Element Model. This modelembodies a topology (nodes, elements), properties and boundary conditions. With this information, dynamic characteristics such as mode shapes and resonance frequencies can be derived. Modifications to the Finite Element Model can then be applied to look for design changes that result in a better simulated behavior of the structure.
At some point during the product development process,prototypes are built and reference measurement data can be obtained through tests carried out on physical parts or the full assembly. The dynamic characteristics are typically expressed in mode shapes or transfer functions (FRF: Frequency Response Functions). To ensure the geometric and dynamic resemblance of the Finite Element model with respect to the test structure, correlation techniques are used. The correlation tools available in LMS Virtual.Lab Correlation allow for qualitative and quantitative correlation analysis. They also deliver updating capabilities to obtain a better match between the Finite Element model and the test model. During this updating process, best likelihood values for uncertain parameters are derived. These are typically parameters of the elements and properties: ranging from shell element thickness, material mass density, bar element parameters, stiffness and damping of connection elements.
This application note describes the process of validating Finite Element Models using correlation techniques and updating the Finite Element Models to obtain the best possible correspondence (i.e. correlation) with the test structure, being the reference structure. The dynamic information captured in a test is used as a target for the Finite Element Model.
Information can also flow in the reverse direction: FE modal information is used in the preparation phase of a physical test to obtain a good set of test measuring points (sensor locations) and excitation points on the structure.
