Reconstructing Load Histories Using Finite Element Results
One of the most important design considerations an analyst or designer must take into account is the in-service loading that the component will see. In a typical FE analysis, the in-service load history is known and applied to the FE model to predict the component’s stress and strain history to enable design decisions.
For some components, especially those with complex operating environments, the in-service load history can be very difficult to directly measure or accurately predict. For example, fitting a load transducer to the component can take a significant amount of time and money and, more importantly, it can physically alter the component by changing its mass, stiffness, and load path. These physical changes could produce inconsistent results between the measured loads and the actual loads.
nCode DesignLife and finite element modeling can solve this problem by establishing a relationship between input loads and the resulting strain response – the strain transfer matrix. Once calculated for unit load cases on the FE model, the strain transfer matrix is used in conjunction with measured physical strain gauge histories to reconstruct in-service load histories. Doing this effectively turns the entire component into its own load transducer. These predicted load histories can then be used as realistic inputs to the FE model - even as designs change - or as loading profiles for laboratory testing.
At the release of nCode 9.0, DesignLife can now reconstruct load histories from measured strain histories and unit load FEA stresses - at no additional cost. This new analysis technique calculates the strain transfer matrix by using DesignLife’s Virtual Strain Gauge, a standard DesignLife feature that recovers the strains on an FE model that result from input loads. These virtual gauges are positioned on the model to simulate the physical strain gauges. The overall method enables the component to act as a load transducer.
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