The plasto-elastohydrodynamic lubrication (PEHL) model of the greased ellipsoid contact is established and solved numerically. In doing so, the increment theory of the plastic surface is adopted to solve the residual deformation, and the fast Fourier transform (FFT) method is employed to accelerate the deformation and stress calculations. Meanwhile, the effeteness of the PEHL model is verified through the residual stress experiment and finite element method. It is found that the plastic behaviour results in a reduction in the maximum grease film pressure. Under heavy load conditions, the grease with large rheology index, large tangential modulus or high entrainment speed of the lubricant is helpful to reducing the maximum residual deformation and maximum residual stress of the greased ellipsoid contact.

Carbon dioxide phase transition blasting (CO2-PB) technology is an effective and economical technology used for breaking rocks. The use of CO2-PB can significantly reduce the vibration damage to surrounding rocks. There is little research on the shockwave generated by the CO2-PB, and simulation can better show the flow field characteristics. In order to clarify the mechanism of its blasting load process, a theoretical analysis and a numerical model were developed to study the flow-field characteristics and the impact pressure of CO2-PB. Our results show that the CO2 absorbs heat from the surrounding environment, producing a significant low-temperature area. The overpressure is significantly lower than the driving gas pressure to the ambient pressure, limiting the maximum over-pressure that can be obtained. When the pressure in CO2-PB reaches 100 MPa, the shockwave is about 4.25 MPa. As the distance increases, the peak value of the shockwave decays rapidly. As the dimensionless distance increases from 1 to 5, the dimensionless overpressure decreases from 1 to 0.23. Under the same blasting pressure, increasing the filling pressure and increasing the filling volume slightly reduce the initial pressure of the shockwave. In the shock stage, strong compression is formed on the surface of the shockwave, resulting in a higher peak pressure value. Meanwhile, the stable pressure is influenced by the target distance, blasting pressure, and CO2-PB length.

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An improved understanding of the mechanisms of SC-CO2 jet drilling technology is important for the application of this new technology. The flow field structure and dynamic fluctuation of SC-CO2 jets are the key factors affecting the jet erosion performance. To improve the erosion performance of the SC-CO2 jet, it is necessary to study the relationship between the different flow fields of the jet. In this study, a numerical simulation model for SC-CO2 jet drilling technology is established. Based on the modified real-gas model, the pressure distribution and flow field characteristics of the SC-CO2 jet were obtained by the simulation investigation, and the reliability of the model was verified. The results show that the flow field structure of a supercritical CO2 jet has typical compressible flow field characteristics. As the jet is fully expanded, its pressure fluctuation is slight and less affected by the distance between the nozzle and the wall. When the jet is in the state of under-expansion, the flow field structure characteristics have a significant impact on the pressure distribution and peak pressure. At the same time, when the distance is large, when nozzle pressure ratio = 5, the pressure ratio has a more significant impact on the flow field and the pressure peak and distribution. The pressure distribution of different flow fields should be fully considered in the application.

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