Constrained Flow Passage Design Of Abrasive Flow Precisionpolishing Based On DPM Model

The artificial joint is a kind of artificial organ implanted into human body to replace bones.It has some specific functions such as eliminating joint pain,restoring the normal function of joint.The market requirement is huge.With better features in biocompatibility,corrosion resistance,Elastic modulus and density,titanium alloy is often used as the material of artificial joints.However,due to the complex structure and the poor thermal conductivity,it’s difficult for artificial joint to reach limit in shape accuracy,dimensional accuracy,surface roughness and integrity by traditional precision machining methods.Therefore the soft abrasive flow precision processing method is proposed.With the good shape adaptability and ultra low machining temperature,this method greatly meets the polishing needs of artificial titanium alloy joints.But during the processing with soft abrasive flow,linear loss and local loss,which cause the uneven distribution of flow characteristics,need to be further studied and optimized.For this,based on the soft abrasive flow processing theory and boundary layer separation theory,the paper presented a theory of constraint channel design during the soft abrasive flow precision processing.:First,based on the Mooney Viscosity formula,abrasive mass-volume formula and combined with the abrasive flow constraint channel,we obtained the correspondence between viscosity and path curvature,by which the hydrodinamical model,Relizable k-? turbulence model and DPM model were modified.Second,according to the above,we built four models of constraint channel of soft abrasive flow and took a numerical simulation in Fluent.The conclusions show:(1)The selected texture structures added on the surface of constraint component could improv e the drag reduction effect and the uniformity of abrasive flow characteristic in the whole cons traint channel.Among the texture structures,the herringbone texture and the triangle texture h ad the most prominent effect.As we know,texture structures can change tracks of the particle.With the triangle texture,the effective collision times between particles and machining surfac e are increased obviously.(2)The depth,density and angle of texture structures have a great influence on the uniformity of the flow characteristics.The texture structure has a significant influence on the flow characteristics of the flow yield near the texture structure.(3)The optimal texture structures parameters were determined by orthogonal test,and the parameters were used in the polishing experiment.Third,the observation has shown that texture structures could improve the disorder of the particle motion and increase the machining uniformity and verified the correctness of the design theory of constraint channel and the simulation results.The polishing experiment results show: the surface roughness of the processed surface with texture structure drops 40% form original constraint channel and the surface appearance is more uniform,which verified the feasibility and effectiveness of texture structure on regulating flow condition and reducing drag in the constraint channel.This method provides a reference for improving the effectiveness of flow regulation.