【正文】 the punch and die, especially their profile radii, are the major variables in deep drawing processes. It has been shown [8] that for a punch nose radius, rp, that is less than twice the thickness of the blank, to, the cups fail due to tearing, while for punch nose radius that is Larger than 10 to stretching may be introduced. In addition, within the region 439。 Johnson and Mellor, 1983). To establish the geometry of a part that can be successfully and economically fabricated from a given material, it is essential to know the limit to which the part material can be formed without reaching failure. 3 This forming limit depends, in addition to the shape change and process conditions, on the ability of a material to deform without failure. The 39。 Date and Padmanabhan, 1992。 1 Deep Drawing With Internal AirPressing to Increase The Limit Drawing Ratio of Aluminum Sheet Young Hoon Moon*t, Yong Kee Kang, Jin Wook Park, Sung Rak Gong Engineering Research Center for Net Shape and Die Manufacturing, Pusan National University The effects of internal airpressing on deep draw ability are investigated in this study to increase the deep drawability of aluminum sheet. The conventional deep drawing process is limited to a certain limit drawing ratio(LDR) beyond which failure will occur. The intention of this work is to examine the possibilities of relaxing the above limitation through the deep drawing with internal airpressing, aiming towards a process with an increased drawing ratio. The idea which may lead to this goal is the use of special punch that can exert high pressure on the internal surface of deforming sheet during the deep drawing process. Over the ranges of conditions investigated for AI1050, the local strain concentration at punch nose radius area was decreased by internal airpressing of punch, and the deep drawing with internal airpressing was proved to be very effective process for obtaining higher LDR. Keywords: Deep Drawing, Internal AirPressing, Limit Drawing Ratio(LDR), AI1050 1. Introduction Aluminum alloy sheets are inferior in press formability pared to the mild steel sheets. Most of the aluminum alloys have an rvalue(plastic anisotropy value) between and , even though the rvalues for the aluminum alloys are only about half of steel(Roger, 1991), they show, under the right circumstances, quite satisfactory drawing 2 behavior. Among the aluminum alloys some noticeable differences in forming behavior on the stamping shop floor have been observed(Roger, 1991。 Revised January 30, 2020) The design and control of a deep drawing process depends not only on the workpiece material, but also on the condition at the toolworkpiece interface, the mechanics of plastic deformation and the equipment used. The equipment and tooling parameters that affect the success or failure of a deep drawing operation are the punch and die radii, the punch and die clearance, the press speed, the lubrication and the type of restraint to metal flow(Hrivnak and Sobotoba, 1992。 Kawai et al., 1992。 Leu, 1997。39。 對于超出 1050 號鋁的拉深極限，在拉深凸模內(nèi)通空氣壓以降低在凸模半徑范圍局部應(yīng)變以及使用內(nèi)部空氣壓獲得更高的拉深極限比是非常有效的方法的證明。然而，即使對于 r 值鋁合金大約只有鋼的一半（ Roger， 1991），在正常情況下，它們表現(xiàn)出令人滿意的拉深效果。 拉深成形是一種無折皺 平板過渡成杯形局部變薄的工藝。 Yossifon and Tisosh, 1991。除了形狀的變化和工藝條件，對材料的變形能力，還有有無故障這都取決于成形極限。 第一 Awhor ?通訊作者， 電子郵箱： 電話： +82515102472 傳真： +82515121722 工程凈成形及模具制造，釜山國立大學(xué)，釜山 609735，韓國研究中心。但是，如果板料尺寸過大，當(dāng)拉深超過拉深強(qiáng)度時工件將拉裂。 由于空氣壓可減少局部應(yīng)變集中，從而延緩了早期失效。 圖 2 顯示的本次研究所用的拉深機(jī)。在凸模通孔與高壓空氣管連接，通入高壓空氣，在這項中使用最大的空氣壓力為 110MPa。 實驗過程 在拉深過程中拉深速度是一個重要因素，過大的速度可能會導(dǎo)致拉深件的起皺或模具損傷斷裂；速度不足從而降低了生產(chǎn)速度。由空氣壓的 影響可以判斷板料最大尺寸可以成形拉深件，因為板料的尺寸大小決定了拉深的高度并更加準(zhǔn)確的加以衡量。 上述數(shù)字表明了，高拉深極限比是在高的內(nèi)部空氣壓力獲得的圖 5 解釋來為什么高氣壓能獲得高的拉深極限比。換句話說， 8 內(nèi)部空氣壓本身并沒有改變變形，而是改變板料成形的變形抗力，有效的疏導(dǎo)了凸模圓角半徑對板料的效應(yīng)和提高了板料的拉深極限比。對于本實驗研究的基礎(chǔ)上進(jìn)行，用高空氣壓保證了高拉深極限比，拉深極限比的提高在于凸模圓角半徑出板料應(yīng)變集中得到