LOAD CONSTRUCTION
With the LOAD CONSTRUCTION tool it is possible to calculate real loads acting on the structure on the basis of true stress measurements.
It is sufficient to create a 'digital twin' FEM of the structure being tested in real operating conditions. The FEM is loaded with 'unit' load cases at the relevant load introduction points.
From the strain gauge reading at a selection of locations, real introduced loads can be derived.
In the example below a time history of loads (in three directions) and the ground contact point of a car suspension can be derived from the time histories of the strain gauges.
The procedure is the following.
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Create a digital twin FEM of the structure being assessed.
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Identify the relevant load introduction points and create 'Unit Load' subcase.
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Run the FEM with the Unit Load cases.
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Import in LIFING the FEM and the Unit Load case results.
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Identify, by engineering judgement, good locations for strain gauges. Be aware that these must be enough in number (more than the number of Unit Load cases).
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Put strain gauges in the real structure and measure operative stress sequences.
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Import the strain gauge readings in LIFING.
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LIFING calculates the Unit Load coefficients which best match the operative stress sequences.
This technique is particularly effective for the setup of a Fatigue test, where loads at the actuators must be defined such to reproduce the real operating conditions.
The digital twin becomes then a tool for the definition of critical areas in the structure, requiring optimizations, or for the definition of crack initiation life at hot spots.
Moreover, in case of new operating loads (for example different usage of the structure), the digital twin can be used instead of multiple real, expensive, tests to redesign the structure or to calculate the new Life.
Typical application: Life extension of an airframe.
