In recent years

there have been frequent occurrences of transformer explosions caused by high-energy arc discharges

resulting in serious social impacts. This paper constructs a Johnson-Cook constitutive model and fracture criterion for the Q355B steel of transformer oil tanks under transient impact

providing a reference for the explosion-proof design and theoretical numerical calculation of ultra-high voltage transformer oil tank structures. To this end

a series of experiments are conducted

including tensile tests at room temperature with different strain rates and notch radii

as well as Hopkinson bar dynamic impact tests with strain rates up to 5 346 s−1

and the model and criterion parameters are calibrated based on the experiments and theory. The microstructure of the samples before and after dynamic impact is compared. The results show that the content of small-angle subgrain boundaries within the crystal increase from 13.4% to 89.8%

and the overall local orientation difference also increases; under impact stress

the fracture of large grains led to a reduction in grain size

with the average equivalent circular diameter decreasing from 7.0 μm to 3.1 μm; deformation textures appeare within grains with [111] parallel to the ND direction. At high strain rates

the deformation mechanism of the oil tank base material is that increased subgrain boundaries and dislocation density hinder dislocation movement

causing work hardening and anisotropic material properties; deformation textures also enhance material properties along the texture direction. Therefore

when subjected to high strain rate loading

if the impact stress direction is different from the texture direction

the risk of material failure and fracture will increase the texture direction. When loaded at a high strain rate

if the direction of the impact stress is different from the strengthening and texture directions

the risk of material failure and fracture increases dramatically.