機(jī)械類(lèi)、模具類(lèi)外文翻譯----在拉深件內(nèi)使用空氣壓提高鋁板的拉深極限比-模具設(shè)計(jì)-文庫(kù)吧
2025-04-16 23:52 本頁(yè)面
【正文】 nducing 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 the materials of the punches and dies. The tools are ground to an appropriate surface finish and a final hardness of 60HRC. schematically shows punch and die set used in this study. For the airpressing, 6 the punch has been bored out and high pressure air line was connected. This arrangement was used to produce internal airpressure of maximum 110 kgf/cm2. The geometry of 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。 to rp 10 to the radius does not significantly affect the limiting drawing ratio(LOR). Therefore, according to the thickness of the blank, the most suitable shoulder radii for the dies and punches were selected to be 6mm with a constant punch diameter of . Test procedure A proper drawing speed is importan
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