Meaning
Material constants within the Ogden hyperelastic strain energy density function define the non-linear stress-strain behavior of rubbery materials and elastomeric polymers. In plastic processing simulations, accurate Ogden model parameters are required to predict the deformation and force requirements of thermoformed or blow-moulded components.
Model Calibration
Determining these constants requires fitting experimental data from multiple loading modes such as tension, compression and shear. Incorrect Ogden model parameters can lead to highly inaccurate simulations of polymer melt stretching during thermoforming. Obtaining high-quality experimental curves ensures that the FEA software correctly predicts the localized thinning of the heated sheet.
This calibration is particularly important for complex geometries with deep draw ratios, where simple linear elastic assumptions fail completely.
Thinning Prediction
Uneven wall thickness in formed parts is a common defect that compromises product performance. Using verified Ogden model parameters allows the simulation to pinpoint regions of high localized strain where the part might fail. This prediction enables moulders to adjust the starting sheet thickness or modify the pre-stretch bubble to achieve a more uniform wall distribution.
Process Optimization
Tooling adjustments and process parameter changes are costly when performed on the factory floor. Relying on simulations powered by precise Ogden model parameters reduces the need for trial-and-error tooling modifications. This saves substantial development cost and speeds up the production startup for complex elastomer parts.
