Study On Ultrasonic Electrorheological Treatment Of Laser Additive Manufactured Surfaces

Additive manufacturing(AM)technology has developed rapidly in recent years and widely used in fields such as aerospace,energy and power,biomedical,ship and automotive industries because of its high efficiency,high quality,and no geometric constraints.The selective laser melting(SLM)technology is one of the most promising processes in metal additive manufacturing.However,powder adhesion and spheroidization will inevitably occur during the manufacturing process,which affect the surface quality of the parts and make them unable to meet practical usage requirements.This problem cannot be directly solved during the manufacturing process,and the subsequent finishing processing is required.The ultrasonic electrorheological treatment studied in this thesis was first proposed to apply to metal additive manufactured surfaces by our lab.During the process,the surface is not always squeezed by the abrasive media like abrasive flow machining,and the abrasive particles can cover any machining area.The size and shape accuracy of the fabricated parts are high.The ultrasonic electrorheological treatment is suitable for polishing various complex irregular shapes,inner holes,and weak rigid structural surfaces.In addition,the dynamic behavior of cavitation bubbles and abrasive particles is controlled through the electrorheological effect,which can improve the polishing process.This study combines numerical simulation calculations and surface treatment experiments to obtain the influence of various processing parameters on the ultrasonic electrorheological treatment of metal laser additive surfaces,and explores the material removal mechanism involved.The main content and results are as follows:(1)A simulation model for ultrasonic cavitation was established,and the effects of the ultrasonic amplitude,working fluid viscosity,and working distance on the flow field were studied.The simulation results show that the larger the amplitude,the smaller the viscosity,and the shorter the working distance,the stronger the cavitation effect and the faster the flow velocity,thereby affecting the material removal process.(2)A simulation model for the impact of the accelerated abrasive particle was built,and the influences of the impact velocity,particle size,and impact angle on the workpiece and the abrasive material state were studied.The simulation results show that the faster the impact velocity and the larger the particle size of the abrasive,the larger the plastic deformation of the materials.The material removal occurred more easily when the abrasive particle impacted the surface at an oblique angle compared to vertical angle.Ultrasonic treatment experiments were also conducted for the laser additive manufacture surfaces,both of the simulation and experimental results show that the wear of abrasive particles was affected by the ultrasonic parameters and the characteristics of the particles themselves,which will further affect the material removal process.(3)The electric field distribution and the force distribution of the abrasive particles after the introduction of the electrorheological effect were calculated through simulations.And the motion behavior of the abrasive particles and the cavitation intensity before and after the application of the electrorheological effect were compared through experiments.Based on the simulation and experimental results,the introduction of the electrorheological effect results in the stable aggregation of abrasive particles in the processing area under the action of dielectric electrophoresis and electrorheological effect,which improves the polishing process.(4)The higher the voltage and the smaller the electrode gap within a certain range,the stronger the electrorheological effect,and the polishing process is further improved.However,when the voltage is too high and the electrode gap is too small,the treatment result will be deteriorated.This is due to the enhancement of the electrorheological effect,the viscosity of the working fluid is increased,and the cavitation is suppressed.The acceleration of the abrasive particle by the cavitation is supposed to be weakened.(5)Ultrasonic electrorheological treatment of metal additive manufactured surfaces were conducted,and the influences of voltage,electrode arrangement,composition and concentration of the slurry,ultrasonic power,and working distance on surface roughness were obtained.The synergy of the cavitation and abrasive particle can be improved by selecting appropriate processing parameters,and which will improve the polishing result.The optimum processing parameters in this study was: ultrasonic power of 600 W,working distance of 1mm,electrode distance of 3 mm,voltage of 2000 V,abrasive particle concentration of 20%,electrorheological fluid concentration of 10%,and abrasive particle mesh size of 2000.