本文選題：純鐵　切入點：薄壁球殼　出處：《南京航空航天大學》2016年博士論文

【摘要】：具有高尺寸精度、高表面質(zhì)量和極高壁厚均勻性要求的純鐵薄壁球殼是某試驗中的關(guān)鍵零件,但純鐵切削時切屑變形大且極易形成積屑瘤、切削力大、刀具磨損嚴重,使得純鐵薄壁球殼的制造精度難以有效保證,迫切需要對影響并制約純鐵薄壁球殼加工精度的基礎(chǔ)科學問題和關(guān)鍵技術(shù)進行深入研究和試驗驗證,從而推動純鐵薄壁球殼工藝技術(shù)的進步。本文主要研究工作包括:(1)采用直角切削試驗對比研究了純鐵、10鋼和45鋼的切削加工性,分析了純鐵切屑形成機理及工藝參數(shù)對切屑變形的影響規(guī)律。結(jié)果表明,純鐵屬于典型的高塑性、高韌性類難加工材料,具有切削力大、切屑變形嚴重、刀-屑接觸長度大等特征,并呈現(xiàn)顯著的剪切滑移變形,采用高切削速度、水冷方式和大前角刀具有利于改善純鐵材料的切削加工性。(2)采用分離式Hopkinson壓桿和材料試驗機進行了純鐵材料動態(tài)及準靜態(tài)力學性能試驗,獲取了高溫(20-800℃)、高應(yīng)變率(104-5×104-1s)下的應(yīng)力-應(yīng)變曲線,建立了基于Power-Law模型的本構(gòu)方程。根據(jù)實測的純鐵材料熱物理屬性和刀-屑平均摩擦系數(shù),并對本構(gòu)方程中應(yīng)變強化參數(shù)進行修正,建立了純鐵材料切削仿真模型。切削力和切屑形態(tài)的仿真與試驗結(jié)果對比表明,仿真模型能夠用于純鐵粗加工階段的工藝參數(shù)的優(yōu)化。(3)研究了純鐵車削過程冷卻潤滑方式和工藝參數(shù)對非涂層刀具耐用度的影響規(guī)律。結(jié)果表明,微量潤滑方式有利于提高刀具耐用度,刀具磨損形式以后刀面磨損和主、副切削刃處的溝槽磨損為主,擴散磨損、氧化磨損和黏結(jié)磨損是其主要磨損機理。分析了冷卻潤滑方式對刀具耐用度的影響機制,提出了采用K313+WS2和KC5010涂層刀具并結(jié)合MQL方式可有效提高純鐵精加工過程的刀具耐用度。(4)從切削過程力-熱耦合角度研究了工藝參數(shù)對工件表面完整性的影響規(guī)律。結(jié)果表明,純鐵已加工表面產(chǎn)生撕裂、溝槽、碎屑、凹坑、鱗刺、塑性和側(cè)向流動等缺陷;實測表面粗糙度遠大于理論值,且表面加工硬化現(xiàn)象嚴重,表層晶粒呈扭曲、拉伸狀塑性變形;工件表面切向和軸向均呈殘余拉應(yīng)力,且切向應(yīng)力大于軸向應(yīng)力。(5)分析了影響純鐵薄壁球殼加工精度的關(guān)鍵因素,探討了刀具對刀誤差及刀尖半徑輪廓誤差對球面輪廓精度的影響規(guī)律及控制措施。結(jié)合有限元方法,研究了裝夾力、端面平面度誤差和切削力對工件變形的影響,優(yōu)化了裝夾方法、切削工藝參數(shù)并提出平面度誤差控制方法,加工的純鐵薄壁球殼尺寸精度、表面質(zhì)量均滿足設(shè)計要求。
[Abstract]:The thin wall spherical shell of pure iron with high size accuracy, high surface quality and high wall thickness uniformity is the key part in a certain test. However, chip deformation is large and chip nodules are easily formed in pure iron cutting, and the cutting force is large and the tool wear is serious.It is difficult to guarantee the manufacturing accuracy of pure iron thin wall spherical shell effectively. It is urgent to study and test the basic scientific problems and key technologies that affect and restrict the machining accuracy of pure iron thin wall spherical shell.So as to promote the technological progress of pure iron thin-wall spherical shell.In this paper, the chip-forming mechanism of pure iron chip and the influence of technological parameters on chip deformation are analyzed.The results show that pure iron is a kind of typical high plasticity and high toughness refractory material. It has the characteristics of large cutting force, serious chip deformation, large contact length of cutter and chip, and obvious shear slip deformation, and adopts high cutting speed.Water cooling method and large front angle cutter are beneficial to improve the machinability of pure iron material. (2) the dynamic and quasi-static mechanical properties of pure iron material are tested by separate Hopkinson compression bar and material testing machine.The stress-strain curves at high temperature (20-800 鈩，

本文編號：1720057