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研究生:王敬仁
研究生(外文):Jin-Jen Wang
論文名稱:磨削加工之熱變形與表面平坦度之探討
論文名稱(外文):Investigation on Thermal Deflections and Flatness on a Ground Surfece
指導教授:蘇侃蘇侃引用關係
口試委員:林原慶單秋成楊宏智黃佑民劉正良廖運炫
口試日期:2011-06-10
學位類別:博士
校院名稱:國立臺灣大學
系所名稱:機械工程學研究所
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2011
畢業學年度:99
語文別:中文
論文頁數:103
中文關鍵詞:磨削火花消失表面變形熱變形
外文關鍵詞:GrindingSpark-outSurface DeformationsThermal Deflections
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磨削是精密加工中常見的加工方式,通常被用來製作高精密度與品質的產品。在製造高精密產品時,尺寸精密度與幾何精密度的控制都是很重要的目標,因為這會影響產品的功能與品質。然而,在一般金屬磨削過程中,會因為金屬切削與磨擦而產生大量的熱量,這會使得加工表面發生明顯的溫度上升現象,進而使加工表面發生嚴重的熱變形。在表面磨削加工過程中,熱變形通常會令加工表面在冷卻後產生凹陷變形;切削力則會造成砂輪與工件表面的彈性變形,如果在加工時不增加磨削深度(depth of cut)的情況下,則彈性變形部份會逐漸回復。因此在某些加工場合中,彈性回復的現象會被利用來改善尺寸精密度,一般將這種加工方式稱作火花消失加工(spark-out)。

本文中以磨削過程中的表面熱變形與彈性變形量來計算實際的磨削深度,並以此來模擬加工表面在磨削後的表面變形情形。一般而言,熱變形會使得實際切除深度增加,但是砂輪與工件之彈性變形則會減少實際切除量,因此在火花消失加工階段的模擬中,如果某次加工中彈性回復量與當時的熱變形量所造成的切削深度超過先前切削的深度,則判斷會發生磨削並且最終切除深度會增加至該次加工的切削深度。透過這個計算過程則可模擬加工後之表面形狀。

本研究也做了一系列磨削實驗,用來驗證模擬結果的正確性。在一般磨削加工部分,我們分別以10μm與20μm兩種磨削深度對工件表面做了一至四次的磨削加工。火花消失加工則分別做了三組實驗:磨削深度影響、砂輪性質影響與切削液影響的實驗。將這些實驗結果與模擬結果做比較後,顯示模擬結果只有在砂輪切削方向上與大磨削深度的條件下,可以做出較準確的預測。另外,由實驗結果中顯示,在乾磨削條件下,若以較小的磨削深度則可能在第八次火花消失加工後得到最小的表面凹陷。在濕磨削條件下,加工表面在第四次火花消失加工後則會發生表面由凹陷變形轉為凸起變形。因此最好的表面平坦度可以在濕磨削的第四次火花消失加工後達成。


Grinding is a common process used for high quality part production. The dimensional and geometrical precision is the major concern to such parts. In metal grinding, enormous heat is generated due to the material removal and friction as well, this usually leads to prominent temperature rise on a ground surface. The thermal deformations on the ground surface usually lead to concave distortion. The cutting forces also cause elastic deformations on wheel and workpiece surfaces, which will recover gradually if there is no increase in depth of cut. The elastic recovery is also used to improve the dimensional accuracy in some grinding process, and such process is called spark-out.

In this study, an analytical model is proposed to simulate the distortions in dry grinding by taking both thermal deformation in workpiece and elastic deformations on wheel and workpiece into consideration. The thermal deformation usually causes overcut and the elastic deformations will decrease the depth of cut. In the simulations of spark-out process, the cut will be made only when the sum of the thermal deformation and elastic deformations are greater than the cutting depth made by previous passes, and then the new cutting depth is found. By this mechanism, the surface profiles after grinding and spark-out will be found.

The grinding experiments were also conducted for the depth of cut of 10μm and 20μm for up to 4 rounds on a surface. The experiments for spark-out were conducted with different depth of cut, wheel types and coolant application methods. The results were compared with the analytical results, and it showed the analytical prediction was only good for the profiles along the grinding direction and with larger depth of cut. The experiments showed the smallest concavity was obtained after 8 spark-out passes when small depth of cut and a softer wheel were used. It also showed the distortion on ground surface were concave in dry grinding and might turn convex after 4 spark-out passes in wet grinding. Thus, the best flatness in wet grinding may be achieved for 4 spark-out passes.


目錄

論文審定書………………………………………………………………………………I
誌謝……………………………………………………………………………………II
中文摘要………………………………………………………………………………III
英文摘要………………………………………………………………………………V
目錄…………………………………………………………………………………VII
表目錄………………………………………………………………………………IX
圖目錄………………………………………………………………………………IX
符號列表………………………………………………………………………………XII
第一章 緒論…………………………………………………………………………1
1-1 研究動機……………………………………………………………………1
1-2 文獻回顧……………………………………………………………………2
1-3 加工表面性質……………………………………………………………10
1-4 研究方向與論文架構……………………………………………………11
第二章 實驗設備與方法……………………………………………………………13
2-1 實驗設備…………………………………………………………………13
2-2實驗方法…………………………………………………………………14
2-2-1模擬參數的設定………………………………………………………14
2-2-2 實驗過程………………………………………………………………15
2-2-3火花消失加工的條件…………………………………………………16
2-2-4粗度儀測量範圍………………………………………………………17
第三章 理論與分析………………………………………………………………18
3-1 乾磨削之溫度分佈分析…………………………………………………18
3-1-1溫度分佈的模擬……………………………………………………………18
3-1-2磨削熱的估計………………………………………………………………21
3-1-3接觸熱傳導係數的計算……………………………………………………22
3-1-4熱對流係數的計算…………………………………………………………23
3-2 熱變型的分析……………………………………………………………23
3-3 局部彈性變形……………………………………………………………24
3-4 分析方法與磨削量的計算………………………………………………25
3-5 表面歪曲變形量之定義…………………………………………………27
第四章 分析與實驗結果……………………………………………………………28
4.1 模擬參數的設定…………………………………………………………28
4-2 模擬分析結果……………………………………………………………29
4-3 實驗結果…………………………………………………………………31
第五章 結果討論……………………………………………………………………37
5-1 分析模型的適用性………………………………………………………37
5-2 磨削熱變形對表面輪廓的影響…………………………………………39
5-3 加工條件對表面在火花消失加工後的影響……………………………42
第六章 結論與建議…………………………………………………………………47
6-1 結論………………………………………………………………………47
6-2 建議………………………………………………………………………48
參考文獻……………………………………………………………………………50








表目錄

表 2-1. 砂輪編號與性質……………………………………………………………56
表 2-2. 大同YK-30高碳鋼(JIS SKS-93)之合金成分……………………………56
表3-1. 分析中所用到之參數………………………………………………………57
表4-1. 分析結果之最大溫度與Jaeger移動熱源理論之計算結果比較…………57
表4-2. 模擬中採用的磨削力………………………………………………………58
表4-3. 表面曲線凹陷量之模擬值與測量值之比較………………………………58
表4-4. 火花消失階段表面凹陷量之模擬值與測量值之比較……………………59
表 5-1. 模擬計算中的彈性回復量與X=-24mm處的熱變形量變化……………59


圖目錄

圖1-1. 磨削量對加工表面扭曲變形的影響………………………………………60
圖1-2. 砂輪顆粒切削加工表面的過程……………………………………………60
圖 1-3. 噴嘴位置……………………………………………………………………61
圖1-4. 加工表面的測量結果………………………………………………………61
圖1-5. 表面起伏與粗糙度對平坦度的影響………………………………………61
圖2-1. KENT KGS-200型平面磨床……………………………………………62
圖2-2. 動力計(KISTLER 9257BA型)……………………………………………62
圖2-3. 測量磨削力時的實驗設備安裝方式………………………………………63
圖2-4. 類比/數位資料轉換卡(AXIOM 5210H)…………………………………63
圖2-5. 粗度儀(HOMMELWERKE T4000)………………………………………64
圖 2-6. 正向磨削力的測量結果(d=10μm)…………………………………………64
圖 2-7. 切線方向磨削力的測量結果(d=10μm)……………………………………65
圖2-8. 試片在實驗中的加工情形…………………………………………………66
圖2-9. 分析中模擬的曲線位置……………………………………………………66
圖2-10. 濕磨削實驗中切削液噴嘴的安裝位置……………………………………67
圖3-1. 分析中試片變形的邊界條件………………………………………………68
圖3-2. 分析模型的網格分割(mesh)………………………………………………68
圖3-3. 表面磨削量之計算流程圖…………………………………………………69
圖3-4. 表面扭曲變形量的定義……………………………………………………69
圖4-1. 磨削與火花消失過程中的正向力( , d=10μm)…………………………70
圖4-2. 磨削與火花消失過程中的切線方向之磨削力( , d=10μm)………………70
圖4-3. 加工面下方1.25mm處由熱電耦測量到的溫度變化(d=5μm)…………71
圖4-4. 加工面下方1.25mm處由熱電耦測量到的溫度變化(d=10μm)………71
圖4-5. 加工面下方1.25mm處由熱電耦測量到的溫度變化(d=50μm)………72
圖4-6. ANSYS有限元素分析結果……………………………………………73
圖4-7. 模擬中加工表面熱變形隨時間的變化……………………………………74
圖4-8. 加工過程中的變形(Overcut)對表面歪曲(Concave)的影響………………75
圖4-9. 表面扭曲在磨削與火花消失處理後的變化………………………………76
圖4-10. 在d=10μm時,第一與第二輪磨削後的表面曲線模擬結果……………77
圖4-11. 在d=10μm時,第三與第四輪磨削後的表面曲線模擬結果……………79
圖4-12. 在d=20μm時,第一與第二輪磨削後的表面曲線模擬結果……………81
圖4-13. 第一輪磨削後的實驗與模擬結果比較……………………………………83
圖4-14. 第二輪磨削後的實驗與模擬結果比較……………………………………84
圖4-15. 實驗中第一至四輪磨削後的表面曲線 (a)磨削方向……………………85
圖4-15. 實驗中第一至四輪磨削後的表面曲線 (b)橫向進給方向………………86
圖4-16. 火花消失過程中的實驗與模擬結果比較…………………………………87
圖4-17. 以不同磨削深度加工在火花消失實驗中的表面曲線 (a) d=10μm……88
圖4-17. 以不同磨削深度加工在火花消失實驗中的表面曲線 (b) d=5μm……89
圖4-17. 以不同磨削深度加工在火花消失實驗中的表面曲線 (c) d=20μm……90
圖4-18. 以不同磨削深度加工對火花消失實驗後的結果影響……………………91
圖4-19. 以不同性質的砂輪加工時在火花消失實驗中的表面曲線(d=10μm) (a) WA46K8V……………………………………………………………………………92
圖4-19. 以不同性質的砂輪加工時在火花消失實驗中的表面曲線(d=10μm) (b) WA60K8V……………………………………………………………………………93
圖4-19. 以不同性質的砂輪加工時在火花消失實驗中的表面曲線(d=10μm) (c) WA80J8V………………………………………………………………………………94
圖4-20. 不同性質的砂輪加工對火花消失實驗後的結果影響(d=10μm)…………95
圖4-21. 在不同噴嘴位置條件下在火花消失實驗中的表面曲線(d=10μm) (a) 砂輪後方……………………………………………………………………………………96
圖4-21. 在不同噴嘴位置條件下在火花消失實驗中的表面曲線(d=10μm) (b) 砂輪前方……………………………………………………………………………………97
圖4-21. 在不同噴嘴位置條件下在火花消失實驗中的表面曲線(d=10μm) (c) 砂輪兩側………………………………………………………………………………98
圖4-22. 不同噴嘴位置對火花消失實驗後的結果的影響(d=10μm)………………99
圖4-23. 以WA46K8V砂輪d=5μm加工時在火花消失實驗中的表面曲線……100
圖4-24. d=5μm在砂輪前方加切削液條件下在火花消失實驗中的表面曲線…101
圖4-25. 以WA46K8V與WA80K8V在d=5μm與10μm時的加工結果比較…102
圖4-26. d=5μm與10μm時在砂輪前方加切削液條件下的加工結果比較………103


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