From Defect Origin to Performance Response: Micro-Defect Characterization and Multi-Field Crack Evolution in High-Alumina Porcelain Bushings

Porcelain bushings are critical insulation components of high-voltage equipment, and their in-service failure, often an explosive rupture initiated at pre-existing micro-defects, remains a safety concern. Existing studies treat defect initiation and defect-to-performance mapping separately, rarely on the same material. Here, a high-alumina porcelain is characterized microstructurally and compositionally, simulated by a coupled electro-thermo-mechanical phase-field model, and measured on two parallel response channels. One normal sample, three artificial-defect samples (iron-doped, sawdust-doped, and unsieved), and samples with four thermal-shock levels (0–15 cycles) were prepared. The artificial defects leave the mean flexural strength close to that of the normal sample but broaden its distribution, with the Weibull modulus falling from 5.8 to 2.3–3.7 and the strength at 10% failure probability from 90 to 43–72 MPa. The thermal-shock levels raise the electrical conductivity from 9.0 × 10−12 to 3.1 × 10−8 S/m and lower the thermal conductivity from 4.09 to 3.56 W/(m·K). The simulation places the transition from arrested damage to through-section fracture at a defect depth of 0.03–0.04 mm for the present load state and length scale. The two transport signals move in opposite directions and are read jointly on a qualitative performance plane, which gives a directional outlook for state assessment.