寬度與厚度縮率對矩形材抽製之影響分析

An Investigation of the Influence of Width and Thickness Reductions in Drawing Rectangular Shapes

張勝奇(Sheng-Chi Chang)

指導教授 ： 林恆勝

國立虎尾科技大學/工程學院/機械與機電工程研究所/碩士(2009年)

摘要

矩形材是線性滑軌或滑塊之類零件輪廓的簡化形狀，但是矩形材也較等邊形材抽製複雜，必須考慮矩形材寬度與厚度的合理縮率組合，及採用不同眼模半角的組合條件下，以獲得矩形材最低抽製應力與最佳成形均勻度的眼模設計規範。
本文首先藉由有限元素法套裝軟體DEFORM-3D模擬矩形材抽製，探討不同眼模半角與面積縮率對抽製應力的影響，並以多餘變形因子來估算工件的變形不均勻度；再進一步驗證矩形材抽製成形的眼模設計法則，針對不同寬厚比之矩形材，以不同縮率組合，進行不同眼模半角組合之最佳眼模半角選用範圍之預測，另外也評估在不同寬度與厚度縮率組合所造成變形不均勻程度的影響。結果顯示，部份縮率組合最佳眼模半角值均在法則預測範圍區間內；部份案例超出範圍但偏差值仍屬少量。矩形材抽製之最佳眼模半角所對應之多餘變形因子區間，皆落在預測範圍內。
第二部份則針對10%與15%二種面積縮率為例，寬度與厚度方向使用相同眼模半角的條件下，寬度與厚度縮率組合對於抽製應力與工件多餘變形的影響，尋求是否存在最佳縮率組合，使得抽製應力為最低，或者得到最佳成形均勻度。結果顯示，在寬度方向施加較少的縮減率，或是在厚度方向施加較多的縮減率時，整體的抽製應力會下降。當寬度與厚度縮率組合之比，等於其寬厚比之反比時，可得到最低的多餘變形因子，亦即最佳的變形均勻度。

關鍵字

矩形材 ； 眼模半角 ； 抽製應力 ； 多餘變形因子

並列摘要

Rectangular shapes are the simplified geometries of linear rails or sliders. But the theory behind drawing with rectangular shapes is more complicated with drawing with shapes of equal-lateral sides. In order to obtain minimum drawing stress or homogeneity, additional parameters such as reasonable combinations of width and thickness reductions as well as die semi-angles along the two directions have to be considered.
This work starts with evaluating the influence of die semi-angle and reduction of area on drawing stress with the aid of FEM software DEFORM-3D. Redundant deformation factor was utilized to estimate workpiece’s deformation inhomogeneity. The data base was further used to verify the guideline in selecting optimum die semi-angles in drawing rectangular shapes with unequal width and thickness reductions. The corresponding redundant deformation factor was also evaluated. The results showed that some cases had good agreement with the guideline while some results fell out of the predicted range. However the error was minimal. The corresponding redundant deformation factors were well predicted with the guideline.
The second part focuses on drawing with 10 and 15% reductions of area. The optimum combination of width and thickness reductions was evaluated under the condition of drawing with same die semi-angle in the width and thickness directions. The results showed that drawing stress could be reduced with less reduction in the width direction. The minimum redundant deformation factor could be obtained when the ratio of width to thickness reduction equal to the inverse of the shape’s width-to-thickness ratio.

並列關鍵字

rectangular shape ； die semi-angle ； drawing stress ； redundant deformation factor

參考文獻

[1]W. Steuff, R. Kopp, “Estimation of designing methods for drawing of section rods and wire”, Wire J. International, Vol. 28, No. 3 (1995), 104-109.

[2]M. Kobayashi, “The present situation of cold drawn special sections, Journal of the JSTP”, Vol. 39, N0. 447 (1998) 335-337.

[3]H.S. Lin, Y.C. Hsu, C.C. Keh, “Inhomogeneous deformation and residual stress in skin-pass axisymmetric drawing”, Journal of Materials Processing Technology 201 (2008) 128-132.

[4]曾竹毅，矩形材淺抽成形之眼模半角選定與其變形不均分析，國立虎尾科技大學碩士論文，民國97年。

[5]B.B. Basily, D.H. Sansome, “Some theoretical considerations for the direct drawing of section rod from round bar”, International Journal of Mechanical Science, 18 (1976) 201-208.