Assessment of damage model and strain rate effects on the fragile stress/strain response of ice material

• Damage model for elastic fragile behaviour of high velocity ice impactors.
• Asymmetric, strain rate dependant damage evolution law.
• Delay effect (limited growth rate) to prevent numerical localisation.
• Solid SPH formulation to capture the dynamic fragmentation pattern.
• Validation with respect to experimental dynamic load levels and impulse.

The present study concerns the modelling of fragile high velocity ice impactors with the aim of better representing the dynamic load (including impulse) applied to impacted structures. This is achieved by taking into account well-known differences between the tension and compression behaviours of ice, and the influence of the strain rate on its fragile material response. The proposed model is then based on an asymmetric tension-compression elastic damage law, which includes delay effects to prevent numerical mesh sensitivity and control the damage growth rate. This model still needed to be improved to obtain numerical results in better agreement with the dynamic tests. This was achieved by adding an explicit effect of the strain rate on the impact peak force through the damage model (initiation threshold and evolution law). The behaviour law has been implemented and assessed in the explicit EUROPLEXUS code (using a solid smooth particle hydrodynamics formulation), after having been identified from dynamic mechanical tests on ice performed with ONERA hydraulic jacks.

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