非等壁異形管材內徑旋鍛製程之研究

A Study of Rotary Swaging for the Tubes with Non-Uniform Wall Thickness in Inner Diameters

胡書銘(Shu-Ming Hu)

指導教授 ： 許源泉

國立虎尾科技大學/工程學院/創意工程與精密科技研究所/碩士(2010年)

https://doi.org/10.6827/NFU.2010.00099

摘要

異形管具有運用範圍廣泛與形狀多樣等特色，為了滿足上述條件可利用旋鍛製程進行生產製造。由於目前旋鍛製程研究大多以外徑成形為主，鮮少以內徑成形作為研究方向。故本研究將針對非等壁異形管材內徑旋鍛製程進行探討，以了解更多有關內徑旋鍛製程之特徵與趨勢。
首先以AL-6063進行材料性質分析，接著進行不同壓縮率之壓縮試驗與旋鍛實驗，隨之將壓縮試件與已成型之管件求得其硬度值與分佈狀況；同時藉由有限元素軟體模擬壓縮試驗與旋鍛實驗，並對應硬度分佈相對位置之等效應變值，以建立硬度－等效應變之預測模式；而後進行旋鍛製程模擬之驗證，比較端面與側面兩方向模擬之差異性。又本研究再以入模半角、管厚比與摩擦因子等三項製程參數作為探討對象，並以分析其對異形管之等效應變、硬度、挫曲分析與環向應力等影響，了解各旋鍛製程參數的影響趨勢。
經研究結果發現，本研究成功建立異形管內徑旋鍛之「硬度－等效應變」預測模式，其等效應變適用在0.1~1.8之間，而預測硬度值則稍高於實際硬度值，但在等效應變範圍0.4~1.8內僅有相差約HV2之相對應性。
就製程參數對異形管旋鍛影響而言，在等效應變方面，當入模半角越大，內外壁之等效應變差異越大，且角度以10°以下為較佳角度；摩擦因子越低，外壁應變值則越低，並大於高摩擦因子之內壁應變值，降低摩擦因子對於管材內徑成形是有益的；管厚比越大，對於應變即產生明顯提升，但於外徑達43mm後，應變值已無明顯的提升作用。
在硬度方面，各製程參數的影響趨勢與等效應變相似，但從內壁至外壁之硬度分佈情況來看，硬度範圍約HV80~82之間，相較於等效應變為0.1~1.8，旋鍛對於硬度提升能很均勻的，即可避免硬度集中產生加工硬化之現象。
又在挫曲分析方面，產生挫曲的條件主要為徑向位移量與徑向速度，而製程參數對於這兩項條件的影響中，入模半角越大，徑向位移量與徑向速度隨之明顯的遞增；降低摩擦因子，亦可減緩徑向位移量與徑向速度；而管厚比遞增，對於徑向位移量與徑向速度之影響與降低摩擦因子有著相同作用。
在環向應力方面，因挫曲會導致管外壁的拉應力與壓應力分佈不均，以拉應力的影響，是以入模半角與摩擦因子最為顯著，而壓應力的影響，則以管厚比最明顯。
總之，透過有限元素模擬分析並配合材料基本特性實驗及旋鍛實驗等，能清楚瞭解旋鍛製程參數對於非等壁管材內徑成形之影響趨勢，並節省模具製作成本與時間效益，更對於成形過程中產生的缺陷，進行修正與改善，藉此可提升鍛件品質與減少模具修護次數。

關鍵字

旋鍛 ； 非等壁異形管材 ； 硬度 ； 挫曲

並列摘要

Special-shaped tubes, which feature extensive uses and a variety of shapes, can be achieved with rotary swaging process (RSP). Current studies of rotary swaging process focused largely on the forming of outer diameter, rarely on inner diameter, therefore, this study explored the RSP of the tubes with non-uniform wall thickness in inner diameters, aiming to learn further about the characteristics of and the trends in the RSP of inner diameter.
First, AL-6063 was adopted for material properties analysis. Then, compression tests with different compression ratios and rotary swaging tests were conducted. The hardness value and the distribution between the compression workpiece and the formed tube were obtained. Meanwhile, compression test and the rotary swaging were simulated with the finite element software, in corresponding with the effective strain value of the relative location of hardness distribution, so as to establish the prediction model of hardness and effective strain value. Then, a rotary swaging process simulation was conducted for validation, comparing the differences between the simulations through axial and radial directions. In addition, this study explored the die inlet angle, thickness ratio, and the friction factors, and analyzed their influences on the effective strain value, hardness, buckling and circular stress of the special-shaped tubes, to have deeper understanding about the influences of the RSP parameters.
With the results, the current study successfully established the prediction model of the hardness-effective strain of inner diameter rotary swaging in special-shaped tubes. The range of the effective strain fell between 0.1 ~ 1.8, while the predicted hardness value were slightly higher than the actual hardness value. However, in the effective strain ranging from 0.4 to 1.8, the difference between the predicted and the actual hardness was HV2.
In terms of the influence of the effective strain on the special tube rotary swaging, the larger the die inlet angle was, the bigger the difference between the effective strain of inside and outside walls would be, with the angle of 10° being the better angle. Besides, the lower the friction factor was, the lower the outer strain was, and the outer strain was higher than the inner strain, whose friction factor was high. Therefore, reducing the friction factor is beneficial for the formation of the inner diameter. Finally, higher thickness ratio resulted in higher strain, but when the outside diameter reached 43mm, the impact was limited.
In terms of hardness, the various process parameters have similar influences to those of effective strain. In the hardness distribution from inner to the outer walls, it ranged roughly from HV80 to 82, with the effective strain from 0.1 to 1.8. This showed that rotary swaging could improve the hardness evenly, and avoid the work hardening.
In the buckling analysis, conditions for buckling were mainly the radial displacement and radial velocity. When inlet angle was bigger, the radial displacement and radial velocity increased significantly. Reducing the friction factor could also reduce the radial displacement and radial velocity. If the pipe thickness ratio increased, it had similar influences on the radial displacement, radial velocity and the friction factor.
In the circular stress, buckling will lead to uneven distribution of the tension and compression stresses in outer walls. Besides, die inlet angle and friction had significant impacts on the tension stress, and thickness ratio on compression stress.
In short, through the finite element simulation analysis, tests of the fundamental characteristics of materials, and rotary swaging tests, the influence of the RSP parameters on the formation of inner diameter of tubes with non-uniform wall thickness can be explored. This could not only save the production cost of dies and increase the time effectiveness, but also amend the defects generated in the forming process, so as to enhance the quality and reduce need for die repairment.

並列關鍵字

rotary swaging ； tubes with non-uniform wall thickness ； hardness ； buckling

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