【正文】 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)變集中得到緩解。 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。 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。 圖 2 顯示的本次研究所用的拉深機。但是，如果板料尺寸過大，當(dāng)拉深超過拉深強度時工件將拉裂。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。 拉深成形是一種無折皺 平板過渡成杯形局部變薄的工藝。 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。 Leu, 1997。 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。 Date and Padmanabhan, 1992。 Chen and Sowerby,1996). It is well recognized that a high plastic anisotropy value(rvalue) clearly indicated a better drawability, by inducing a high resistance of a sheet to thinning. But there is no single material parameter which satisfactorily describes the drawing behavior. In this work, the effect of internal pressing on the formability of aluminum sheet is investigated to increase the LOR of aluminum alloys. Figure 1 is a schematic of a cup die, showing the punch, die and blank holder, and a partially formed cup. The punch is on the down stroke and is just beginning to draw the sheetmetal blank into the die cavity. If the blank size has been chosen correctly, the metal will work harden sufficiently to overe the bined strength of the remainder of the blank metal and friction between it and the blank holder and the part will be successfully made. However, if the blank is too large, the part will break when the tensile strength is exceeded. The first deformation of the blank occurs between the die radius and the punchnose radius part, since this is the part that is not supported by friction with the tooling ponents. The metal in this section is increasing in area as it thins out and losing 4 much of its strength. Therefore, the strain concentrations at die radius and punchnose radius part have been the main cause of early failure. If the strain concentration in this critical area can be released, the load carrying capacity will be increased and breakage can be avoided. One possible way to do this is airpressing the internal surface of the blank by using specially designed punch. Because the airpressing can reduce the local strain concentration and thus retard an early failure. The test methods and results are described in this article. 2. Experimental Procedure Material and equipment Commercially available Al1050 aluminum sheet with a thickness of mm is used for the blank material. Tensile property of the AI1050 is shown in Table I. 5 Preliminary experiments show that blanks with diameters of less than 70mm are drawn without failure. Therefore blank diameters are progressively increased by I mm from the blank diameters of 70 mm. When failure of blank occurs, experiments proceed with the diameter increasing or decreasing I mm to ascertain the maximum diameter of the blank sheet without failure in cupdrawing for estimating the LDRvalue. Figure 2 shows the deep drawing machine that is used in this investigation. It is a hydraulic press with a maximum load capacity of 50 Ton and a variable punch speed of I mm/sec15 rum/sec. In this press, the punch is mounted on the lower shoe and the die on the upper shoe of the machine. The punching and blankholding forces and the punch stroke can be measured separately by indicators those are provided on the machine. Proper tool steel with appropriate mechanical properties and hardening treatment is used for