- 學位論文
不同型式螺旋流道在流體研磨加工的研究
Study on the Effects of Helical Passageways in Abrasive Flow Machining
摘要
流體研磨加工(Abrasive Flow Machining；AFM)是種有效率的表面拋光方法，尤其是可快速移除放電加工面的再鑄層，但是在孔洞經由流體研磨在拋光時，因過程受限於其上下單一方向作動的加工方法，使得工件表面粗糙度拋光效果較不均勻。因此，本研究設計特殊形式的螺旋流道，使流體在拋光時產生多方向的拋光路徑，達到均勻拋光的目的。 在研究過程中，可分為模擬與實驗兩種階段，先利用CFD-ACE+軟體模擬磨料在螺旋模仁中流動的情形，瞭解磨料流速分佈和剪應變率的變化，可推斷在孔洞中添加不同型式螺旋模仁後會產生多向性流動，且能夠有效的改善軸向表面粗糙度不均勻性。最後，實驗過程中，設計各種不同型式及尺寸的模仁，探討螺旋槽數、間距、槽寬以及圈數對於孔洞研磨拋光的影響，相對於無模仁表面粗糙度改善率是61％，由實驗結果發現，模仁螺旋槽數為4槽、槽寬0.5mm、間距為0.5mm及螺旋圈數為1圈的設計條件，對孔洞表面粗糙度改善效果最佳，其改善率可達到76％。
並列摘要
Abrasive Flow Machining(AFM) is a efficient method of surface polishing, especially it can quickly remove recasting layers which made by wire electrical discharge machining (WEDM). However, AFM methods have difficulty achieving uniform roughness of an axial distribution in circular hole polishing due to limited unitary axial motion of abrasive media. Therefore, this study design a special mechanism of the helical flow passageway to perform multiple flowing paths of an abrasive medium, then the fluid produced in the polishing of multi-directional path to achieve the purposes of uniform polishing. For this investigation, we consider the comparisons both simulation and experiment method. Above all, CFD-ACE+ numerical software was used in the simulation of abrasive flow in the helical mold core to understand the behaviors of abrasive velocity distribution and shear strain rate changes. Analytical results indicate that the design of helical passageway will obviously produce multi-directional flowing path, and we can infer it effectively improve the axial uniformity of surface roughness by the deviation of shear strain rate changes. Finally, Experiment proceeding designed a variety consists of different type and different size of mold cores to verify the effectiveness of helical passageway in AFM polishing, such as the number of helical grooves, the gap between work-piece surface and helical edge, the thickness of helical slot and the number of turns. Based on the experiment results, it showed that the helical passageway is superior to circular passageway in reducing roughness improvement rate (RIR) by roughly 76% compared with RIR 61% for the circular passageway, which design conditions including for four helices groove, 0.5 mm gap, 0.5 mm thickness of helical slot and one helical turn.