轮胎破片冲击机身的非等比例相似模型研究

In order to reduce the cost for the impact test of the full-size airframe structures, an incomplete similar model was established by the similarity theory. Based on dimensional analysis, the correction relation for the Johnson-Cook linear strain-rate function was formulated. Due to the limitation of manufacturing technology, the effect of the incomplete similar model with distorted thickness on similarity behaviors should be taken into account, so an exponential function was adopted to establish the correction formula for the distorted thickness model. The validity of the simulation model was then verified by comparisons relevant to the deformation on the fuselage, the strain-time curves of target plates and the final deformation profile. In addition, the influences of fragment angle, material property, distortion thickness and light weight on the deformation behavior of the fuselage structure were analyzed. The following main results were obtained. (1) Under the impact velocity of 150 m/s, the most severe impact conditions appear at the impact angle of 90° and the fragment attitude of 180º; by considering various factors, the 3.5-mm-thickness titanium alloy plate is regarded as the best choice for fuselage structures, and it is used as a full-size prototype to verify the similar method. Besides, it’s worth noting that an unconventional phenomenon takes place at the impact angle of 30º, while a reasonable explanation is given. (2) The effect of strain rate on the impact of tire fragments on the fuselage structure is not notable, so the incomplete similar model is in good agreement with the prototype results. (3) The incomplete scaled-down model corrected by this method can effectively predict the deformation behavior of prototype fuselage subjected to the impact of tyre fragments. Although there is a certain deviation between the model and the prototype on the time scale, on the spatial dimensions, the incomplete scaled-down model can effectively correct the prediction error for the maximum center deformation caused by the distortion thickness, and the corrected maximum error is less than 5.1%, indicating that the method can effectively guide the design for airframe structures.