Study on Dynamic Properties and Constitutive Model of Graphite Ore

In order to study the dynamic mechanical response characteristics of crystalline graphite ore under the coupling effect of grade and dynamic load, the dynamic compression tests of crystalline graphite ore samples with four grade levels (5.19%, 10.79%, 12.65%, and 15.50%) under different impact pressures were carried out by using a 50 mm diameter split Hopkinson pressure bar test device. The effects of grade and strain rate on the dynamic mechanical properties and energy consumption characteristics of crystalline graphite ore were comparatively analyzed. Furthermore, a dynamic constitutive model for crystalline graphite ore incorporating both grade and strain rate effects was established based on the viscoelastic ZWT model. The test results show that the dynamic compressive strength and peak strain of crystalline graphite ore increase progressively with rising strain rate, while the elastic modulus remains strain-rate-independent. As the ore grade increases, the initial compaction deformation and peak strain of the samples increase, whereas the dynamic elastic modulus, dynamic compressive strength, and their strain-rate sensitivity gradually decrease. Additionally, within a specific strain rate range, the degree of fragmentation of medium- and low-grade ores intensifies with increasing energy consumption density. In contrast, high-grade ores exhibit minimal variation in fragmentation degree. This indicates that ore grade significantly influences the dynamic fragmentation behavior of crystalline graphite ore. A dynamic constitutive model that considers both grade and strain rate was established, and its accuracy and applicability were verified by comparing the model-predicted results with experimentally obtained dynamic stress-strain curves. The model offers theoretical support for investigating the mechanical behavior of crystalline graphite ore under dynamic loading.