本文選題：光學玻璃 + 超聲振動磨削　； 參考：《哈爾濱工業(yè)大學》2017年碩士論文

【摘要】：光學玻璃具有穩(wěn)定的物理、化學性能及高度光學均勻性,因此廣泛應用于相關工程領域,但其高脆性、低斷裂韌性的特點降低了光學玻璃的可加工性能,傳統(tǒng)磨削技術極易在已加工的亞表面引入各類損傷,對加工質量及效率等都產生不利影響。降低加工零件亞表面損傷程度,有助于減少零件后續(xù)研拋時間,提高零件的整體加工效率。超聲振動輔助磨削加工技術具有降低平均切削力、減少加工微裂紋、提高材料去除率等優(yōu)勢。但目前超聲振動作用對光學玻璃亞表面微裂紋擴展的影響尚未明確,對超聲振動作用下光學玻璃亞表面損傷形成及預測的研究還不完善。因此開展超聲振動磨削中光學玻璃亞表面損傷的研究對實現(xiàn)該類材料精密低損傷加工具有重要理論意義和實用價值。超聲振動作用對光學玻璃材料亞表面微裂紋擴展的影響分析是亞表面加工損傷研究的基礎。本文分析了超聲振動效應對單顆磨粒運動軌跡及動力學特征的影響。通過準靜態(tài)印壓實驗,建立了BK7光學玻璃在準靜態(tài)載荷作用下的內部應力場分布模型,分析了應力場驅動下微裂紋成核與擴展機制,結果表明,磨粒運動軌跡重疊及超聲效應的引入造成的中位裂紋屏蔽作用是使裂紋擴展深度出現(xiàn)下降的主要原因。通過超聲振動輔助旋轉刻劃實驗,分析了沖擊載荷對光學玻璃材料脆性斷裂過程的影響,結果表明由于磨粒慣性沖擊力的作用,使得BK7光學玻璃材料動態(tài)力學性能發(fā)生變化,內部裂紋更容易成核,微裂紋閉合導致的材料脆性斷裂成為材料去除的主要原因。上述研究為后續(xù)光學玻璃超聲振動磨削亞表面損傷規(guī)律和預測的研究提供理論基礎。超聲振動磨削加工中砂輪多磨粒作用和高頻振動效應都會對亞表面損傷產生重要影響。本文進行了超聲振動磨削加工實驗,采用掃描電子顯微鏡對光學玻璃加工亞表面裂紋微觀形貌進行了檢測,分析了多磨粒、多種載荷作用下亞表面裂紋損傷的特征及其形成機制,結果表明,磨粒加載方向及材料動態(tài)性能變化是造成BK7玻璃亞表面裂紋形態(tài)變化的原因。在此基礎上,通過實驗研究獲得了磨削加工參數(shù)及砂輪參數(shù)對亞表面裂紋最大深度的影響規(guī)律,為后續(xù)亞表面裂紋最大深度預測模型的建立提供依據(jù)。對亞表面裂紋最大深度實現(xiàn)有效的預測是減少零件后續(xù)研磨和拋光時長、提高加工效率、改善磨削加工質量的關鍵。根據(jù)前述分析結論和研究,本文分別采用最小二乘支持向量機及高斯過程回歸方法建立了超聲振動磨削加工BK7光學玻璃的亞表面裂紋最大深度預測模型,在此基礎上,通過磨削加工實驗對兩種預測模型的有效性進行了驗證,并對預測精度進行了比較。為實現(xiàn)光學玻璃材料超聲振動磨削加工工藝參數(shù)的優(yōu)選提供了基礎和依據(jù)。
[Abstract]:Optical glass has stable physical and chemical properties and high optical uniformity, so it is widely used in related engineering fields, but its high brittleness and low fracture toughness reduce the processability of optical glass. Traditional grinding technology is easy to introduce various kinds of damage to the machined subsurface, which has adverse effects on the quality and efficiency of machining. Reducing the degree of sub-surface damage of machining parts is helpful to reduce the time of subsequent polishing and improve the overall machining efficiency of the parts. The ultrasonic vibration assisted grinding technology has the advantages of reducing the average cutting force, reducing the machining microcracks and improving the material removal rate. However, the effect of ultrasonic vibration on the crack propagation of optical glass subsurface is not clear, and the research on the formation and prediction of subsurface damage of optical glass under ultrasonic vibration is not perfect. Therefore, it is of great theoretical significance and practical value to study the subsurface damage of optical glass in ultrasonic vibration grinding. The analysis of the effect of ultrasonic vibration on the crack propagation of optical glass is the basis of the research on the damage of subsurface processing. In this paper, the effect of ultrasonic vibration on the motion trajectory and dynamic characteristics of a single abrasive particle is analyzed. The internal stress field distribution model of BK7 optical glass under quasi-static loading is established by quasi-static stamping experiment. The mechanism of microcrack nucleation and propagation is analyzed. The main reasons for the decrease of crack propagation depth are the overlap of the motion trajectories of abrasive particles and the median crack shielding caused by the introduction of ultrasonic effect. The effect of impact load on brittle fracture process of optical glass material is analyzed by ultrasonic vibration assisted rotating characterization experiment. The results show that the dynamic mechanical properties of BK7 optical glass material are changed due to the effect of inertia impact force of abrasive particles. The internal crack is easier to nucleate, and the brittle fracture caused by micro-crack closure is the main reason for material removal. The above research provides a theoretical basis for the study of the subsurface damage and prediction of ultrasonic vibration grinding of optical glass. In ultrasonic vibration grinding, the effects of multi-abrasive and high-frequency vibration on the subsurface damage are very important. In this paper, ultrasonic vibration grinding experiments were carried out, and the micro-morphology of sub-surface cracks in optical glass processing was detected by scanning electron microscope (SEM), and the multi-abrasive particles were analyzed. The characteristics of subsurface crack damage and its formation mechanism under various loads show that the change of subsurface crack morphology of BK7 glass is caused by the change of the loading direction of abrasive particles and the dynamic properties of the material. On this basis, the effects of grinding parameters and grinding wheel parameters on the maximum depth of subsurface cracks are obtained through experimental research, which provides a basis for the establishment of a prediction model for the maximum depth of subsurface cracks. Effective prediction of the maximum depth of subsurface cracks is the key to reduce the length of subsequent grinding and polishing of parts, improve machining efficiency and improve grinding quality. Based on the above analysis conclusion and research, the prediction model of maximum depth of subsurface crack in ultrasonic vibration grinding BK7 optical glass is established by using least square support vector machine and Gao Si process regression method respectively. The validity of the two prediction models is verified by grinding experiments, and the prediction accuracy is compared. It provides the foundation and basis for optimizing the technological parameters of ultrasonic vibration grinding of optical glass materials.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ171.68

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