Investigation on ablation mechanism and model of EPDM insulator under high acceleration condition (I) - Analysis of ablation mechanism

The influence of particle concentration, impacting speed and angle on ablation characteristic of EPDM insulator were investigated based on test facility which can adjust particle concentration, impacting speed and angle. Different ablation rates of insulator material were obtained under different state parameters of particle erosion. Structures of carbonization layers were analyzed by scanning electron microscopy. Base on the structure of cavity, insulator mechanism of EPDM under high acceleration condition was discussed. The results show as follows: (1) By analyzing the influence law of carbonized ablation rates affected by different particle concentrations, impacting velocities and angels, it is found that a critical speed exists. When impacting speed is below the critical value, carbonized ablation rate changes slowly with speed and angle respectively. But if exceeding it, concave pits appear on the surface of carbonized layers. Carbonized ablation rates rise up sharply and the effects of angels cannot be ignored. (2) There are huge discrepancies in the surface and cross section of insulation layer, erosion modes and destroy mechanisms of different particle erosion condition. Compact/loose structures was formed in carburization layer of EPDM insulator. (3) In observing the structures of carbonized layers of basic formula by scanning electron microscope, three typical surface morphologies of the ablation were discovered with the increase of particle erosion speed.(4) The coupling relationship between thermochemistry ablation and parcile erosion is established through analyzing the abalation process of EPDM insulator under different parcile erosion conditions.