Non-direct similitude technique applied to the dynamic axial impact of bonded crush tubes

The use of lightweight materials in vehicle structures requires appropriate joining techniques, among them adhesive bonding. Testing full-scale structures such as vehicle crush tubes can be prohibitive in terms of cost and appropriate facilities may not be available, so it is often desirable to test sub-size structures. To address this need, the suitability of scaling to accurately describe the behavior of bonded crush tube structures during axial impact scenarios was investigated. A numerical simulation was validated using literature sources and experimental testing, and then used to investigate scaling. The predictions for structures constructed out of a single material, in terms of stress distributions and deformations were in good agreement between the numerical simulations of the model (experiment modified in size by a scale factor) and the prototype tubes (actual size experiment). When considering bonded structures with the possibility for joint separation, the Non-Direct Similitude technique was applied to scale the structure and the results showed a small departure between the predictions of the model and the prototype. For bonded crush tubes, where the presence of a second material in the form of an adhesive layer was small, the scaling method provides acceptable results. The limitations of the scaling technique were discussed.