基于分子动力学的振动辅助磨削对镍基高温合金加工硬化行为的影响OA

Nickel-based high-temperature alloys are widely used in key fields such as aerospace engines,gas turbines,and high-end energy equipment due to their excellent high-temperature strength,oxidation resistance,and corrosion resistance.However,these materials have high strength,high hardness,low thermal conductivity,and a significant tendency for work hardening.During traditional grinding processes,problems such as high grinding force,high grinding temperature,severe subsurface damage,and difficulty in controlling the surface integrity often occur.Vibration-assisted grinding,as a new precision processing method,can improve the material removal behavior through periodic loading-unloading and intermittent contact effects.However,the influence mechanism of vibration-assisted grinding on the work hardening of nickel-based high-temperature alloys,especially the microscopic regulation laws under different process parameter conditions,has not yet been systematically studied.Therefore,this paper aims to reveal the influence laws and internal mechanisms of vibration-assisted grinding process parameters on the work hardening behavior of nickel-based high-temperature alloys at the atomic scale. Using the molecular dynamics simulation method,a model for single abrasive particle vibration-assisted grinding of nickel-based high-temperature alloys is established,and a systematic study is conducted around two key process parameters:amplitude and vibration frequency.During the modeling process,the basic structures such as abrasive particles,workpiece,boundary layer,and constant temperature layer are constructed to simulate the interaction process between the abrasive particles and the workpiece material under vibration-assisted conditions;at the same time,the stress response,temperature evolution,dislocation density changes,and dislocation structure evolution behaviors of the workpiece during the grinding process are combined to characterize the material's work hardening characteristics under different parameter conditions.Based on the dislocation theory and the work hardening mechanism,the influence of vibration-assisted grinding on the plastic deformation and work hardening behavior of the material's surface layer is further analyzed from aspects such as dislocation nucleation,proliferation,migration,entanglement,clogging,and the formation of barrier structures. Studies show that the work hardening of nickel-based high-temperature alloys during vibration-assisted grinding essentially results from the obstruction of dislocation movement.The degree of this hardening is closely related to the internal dislocation density of the workpiece and the evolution of dislocation barrier structures.The higher the internal dislocation density of the workpiece,the more complex the dislocation entanglement,dislocation accumulation,stair-rod dislocations,Hirth dislocations,and Frank dislocations and other barrier structures are.The resistance that the material needs to overcome during subsequent plastic deformation is greater,and the hardening phenomenon is more significant.The influence laws of different process parameters on work hardening are significantly different.As the amplitude increases,the periodic separation effect between the abrasive particles and the workpiece is enhanced,and the local stress concentration in the grinding zone is weakened.Although the local temperature increases,the temperature rise promotes dislocation migration and rearrangement,reducing the overall internal dislocation density and the number of barrier structures in the workpiece,thereby weakening the hardening phenomenon.As the vibration frequency increases,the periodic interaction times of the abrasive particles with the workpiece per unit time increase,the dynamic loading-unloading effect becomes more significant,the stress release in the grinding zone becomes more sufficient,and the thermal activation effect is enhanced.Dislocations are more likely to undergo migration,annihilation,and reconstruction,so the internal dislocation density of the workpiece decreases,dislocation entanglement and dislocation accumulation and other barrier structures are reduced,and the degree of work hardening decreases accordingly.