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題 名 | The Behaviors of Sand Flow in Flask for the Expendable Pattern Casting Process=消失模製程振砂之流動特性 |
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作 者 | 張在源; 施登士; 蕭述三; | 書刊名 | 中國機械工程學刊 |
卷 期 | 20:4 1999.08[民88.08] |
頁 次 | 頁335-343 |
分類號 | 472.2 |
關鍵詞 | 消失模製程振砂; 流動; EPS; Acceleration level; Liquefaction; Interlocking; |
語 文 | 英文(English) |
中文摘要 | 在消失性模鑄造的造模過程中,模砂的流動模式對於鑄件品質與模穴設計扮演著 支配性的影響,由於砂顆粒間強烈摩擦力及互銷作用,以致往往無法將鑄砂順利地輸送至保 麗龍模型四週,太過於強制砂的流動則可能導致模型變形,本實驗探討振動條件對於鑄造用 乾砂流動性的影響及砂體流動的機制,研究結果顯示:單純的水平方向振動對於砂體流動作 用不顯著,振動之主要作用在於使砂體呈液狀態,以減少砂顆粒間之有效應力,再藉著水平 向的驅動,此時砂的流動效果較為顯著, 在砂層表面以下 5 ∼ 20 公分之區城其流動性最 大,會形成一流動區,底層區之部份由於砂箱之振幅不均勻性及砂粒間的接觸力隨深度增加 而變大等因素,其流動性逐漸降低,二維振動時由於兩軸向間的相位差,在振動時會起共振 作用,對於砂體流動形態會產生很大的作用,在二維大振幅時會起汽泡現象,亦將在本文中 加以探討。 |
英文摘要 | In the expendable pattern casting (EPC) molding process, sands were properly transported and compacted around the coated patterns by means of vibration. Difficulty arose for the case when it was necessary to transport molding sands into long horizontal cavities to form sand cores. The significant resistance and interlocking among sand particles often cause faults in casting due to incomplete compaction, while an over drastic vibration might cause distortion of the replicas. The behavior of sand motion in flask thus played an important role in designing mold cavities and in making decisions regarding molding conditions. The velocities and directions of sand motion in flask were different from point to point, depending on vibration conditions and the geometry of the flask. As the vibration processed, a layer of sand with a certain thickness near the surface flowed from the center outward to the flask wall, while in the region of 5 to 20 cm beneath surface, sands contracted inward to the center. At further depth, sand settled down steadily to the bottom along the wall. There existed an optimum stratum depth, at which the motion of sand in the horizontal direction approached a maximum value, and thus might meet the needs of sand transported into long cavities. The object of this paper is to investigate the behavior of sand flow in flask. Experimental results indicated that twodimensional vibration, including the vertical direction, at resonance frequencies might greatly increase the fluidity of sand. The strength of sand flow depended on the acceleration level and the frequencies of the vibration system. With 2-and/or 3-dimensional vibration with sufficiently large gaps between sand and flask wall, air may be entrapped and form bubbles, these bubbles fluctuating drastically in the region near the free surface and blast out. The formation of bubbling is described in this paper. |
本系統中英文摘要資訊取自各篇刊載內容。