Effect of low-speed waterjet pressure on the rock-breaking performance of unsubmerged cavitating abrasive waterjet

Unsubmerged cavitating abrasive waterjet(UCAWJ)has been shown to artificially create a submerged environment that produces shear cavitation,which effectively enhances rock-breaking performance.The shear cavitation generation and collapse intensity depend on the pressure difference between the intermediate high-speed abrasive waterjet and the coaxial low-speed waterjet.However,the effect of the pressure of the coaxial low-speed waterjet is pending.For this purpose,the effect of low-speed waterjet pressure on rock-breaking performance at different standoff distances was experimentally investigated,and the effects of erosion time and ruby nozzle diameter on erosion performance were discussed.Finally,the micromorphology of the sandstone was observed at different locations.The results show that increased erosion time and ruby nozzle diameter can significantly improve the rock-breaking performance.At different standoff distances,the mass loss increases first and then decreases with the increase of low-speed waterjet pressure,the maximum mass loss is 10.4 g at a low-speed waterjet pressure of0.09 MPa.The surface morphology of cavitation erosion was measured using a 3D profiler,the increase in both erosion depth and surface roughness indicated a significant increase in the intensity of the shear cavitation collapse.At a low-speed waterjet pressure of 0.18 MPa,the cavitation erosion surface depth can reach 600μm with a roughness of 127μm.

同轴水射流辅助激光加工效率及锥度实验研究

对液体环境条件下的同轴水射流辅助激光加工技术及其加工机理进行了初步研究,并建立了加工实验装置,分别研究了加工效率和加工锥度随激光能量、水射流流速、喷口与工件间隙的变化规律。实验结果表明:同轴水射流辅助激光加工效率随着激光能量、水射流流速的增加而提高,当喷口与工件间隙约为3 mm时加工效率较高;加工微孔的锥度随着激光能量、水射流流速的增加而减小、随着喷口与工件间隙的增加而增大,当间隙大于5 mm时锥度基本保持不变。最终,利用优化的工艺参数,加工出锥度约为2°且无热影响层、再铸层和微裂纹的表面完整性好的微孔。