Finite Element Modeling
Finite Element Analysis (FEA) is a process of using mathematical models to simulate displacement, stresses, strains and other parameters to predict the performance and limits of a design. FEA models are used extensively in the aerospace, automotive and medical device industries. In addition to helping engineers understand when and if a design will break, FEA helps demonstrate how a structure will deform and where load concentrations occur. The models reduce the amount of prototypes necessary during product development and are essential in the design process.
The Challenge of Validation
FEA models rely on statistical assumptions to determine how a design will behave in a real-world environment, but reality often does not match the scenario assumed by models. There are many reasons for these discrepancies. Minute differences in the machining process, tiny cracks in the material, retrofitting situations and unexpected environmental impacts can cause loads to be distributed across the design differently than a model predicted. Unanticipated discrepancies can lead to catastrophic malfunctions later in a product’s lifecycle, which in turn cost millions of dollars, waste months of design-development time and are often safety hazards that could cause serious injury.
One of the biggest challenges to designing high-quality safe products with long life cycles is model validation. For a model to be validated, a prototype must be built and tested to see if reality matches the predictions of the model. When conducting physical tests to measure stresses and strains, engineers focus on critical points identified by the original FEA model. Strain gauges are applied, and information about the critical points is collected. This process lends itself easily to only monitoring for expected problems, which can create serious blind spots in the testing process. Without a comprehensive analysis of real-world data, prototype testing can be costly and inaccurate.
Existing monitoring technologies such as strain gauges cannot provide a full picture of the stresses and strains of a structure. Strain gauges can provide reliable data for a few critical points, but are not able to provide any information about the important spaces between critical points. For example, while strain gauges will monitor specified points around a crack in a structure, it is essential to know how loads are redistributed throughout the prototype as a result of the crack. Using strain gauges and their limited data collection forces engineers to depend on the ability of models to accurately identify critical points. This is problematic since, as described above, there are multiple reasons how and why reality can differ from a model.
Solutions Using FOS
Access to spatially continuous, real time data can help validate a model faster and much more precisely. While strain gauges are limited to reporting information about critical points, fiber optic sensing (FOS) obtains data along the entire length of the fiber. In addition to collecting data for critical points, FOS technology accurately measures activity between these points. For example, Sensuron’s FOS platforms have over 2,000 sensors on a single fiber. Each fiber on the system is monitored simultaneously in real time, providing vast amounts of data during a physical test by monitoring up to tens of thousands of sensing locations.
Although there are thousands more sensing points than strain gauges, Sensuron’s fiber can be installed in significantly less time. Sensuron’s technology has been used to find embedded by-products from manufacturing, as well as folding, and wrinkling of composite materials. These systems have also been utilized in locating and tracking crack propagation in fatigued wind energy blades, and even determining the degree of unforeseen plastic deformation in critical load bearing aircraft components. Distributed FOS equips engineers with the data necessary to confidently validate their models and avoid costly failures after production has begun.
Fiber optic sensing is a simple, elegant and sophisticated solution to the data shortage that occurs when using legacy technology like strain gauges and thermocouples. The flexibility of the fiber optic cables, ease of installation, amount of sensing capability, real-time monitoring and ability to measure multiple parameters, make Sensuron’s platforms the right choice for endless applications. Visit our case studies page for more information on particular use cases or complete the form below to download our white paper on the benefits of distributed strain and temperature measurements.