Papers by Keyword: Limit Drawing Ratio (LDR)

Abstract: The current work investigates anisotropy and forming characteristics of ZE10 Mg alloy. Anisotropic effects are measured by analysing tensile tests data for the specimens from 0o, 45o and 90o rolling directions of thin sheet of 0.8 mm thickness. The effects of temperature and strain rates are also included in anisotropic analyses. The mechanical properties of ZE10 alloy are affected by the physical conditions like temperature and strain rates. The effect is significant on yield strength, UTS and fracture strain while small variation is observed in case of Young’s modulus. Deep drawing experiments have been done to investigate the effects of temperature on forming characteristics and limit drawing ratio (LDR) of an alloy. Forming investigation shows that it is difficult to produce a good or unfractured part at 100 oC, but it can be produce at 150 oC or higher with different combinations of blank holder force and drawing ratio. Also, LDR and blank holder force also effects required punch force.

Abstract: The effect of forming temperature on the deep drawability (limit drawing ratio (LDR)) of AZ31 magnesium alloy sheet was studied both numerically and experimentally by the use of finite element analysis software DYNAFORM and specially designed warm deep drawing die set. The simulation model was built by SolidWorks 2009, 3-Parameter_Barlat model with BT shell unit was adopted as material model. The constitutive relation of the material was provided by uniaxial isothermal tension tests at different temperatures. After being set, all parameters were referred to famous explicit dynamic solver LS-DYNA. The simulation results showed that the LDR of the AZ31 magnesium alloy sheet is increased with the increase of the temperature initially, but after the temperature reached 423K, the LDR reached the maximum, and then decrease with the increase of temperature in the temperature range studied (room temperature-673K). PTEF was used as lubricant in the experiment. Experimental results showed same trend as numerical simulation results in the studied range of temperature, and LDR reached the maximum of 3.0 at 423K. It is shown that the results of numerical simulation have a good agreement with that of the experiment. By analyzing the microstructure of the drawn-cup walls at different temperatures, it is found that grains were stretched along the direction of tension at temperatures lower than 423K. And there appeared a large number of fine recrystallized grains when forming temperature is 423K showing that dynamic recrystallization occurred during forming process. Dynamic recrystallization conducted completely when forming temperature increased higher than 423K, but the material softening would aggravate with the increase of temperature and on the contrary would do harm to the deep drawing of AZ31 magnesium alloy sheet, resulting the decrease of LDR.

Abstract: Deep drawing processes are widely utilized in mechanical industries for producing several typologies of products ranging from computer industry to automotive components, from house products to furniture products. The goal of this study is to verify experimentally the warm deep drawing process assisted with hydraulic counter pressure as a suitable alternative to conventional deep drawing as a means for producing defect-free sheet metal parts. Using specific process parameters like blank holding pressure, blank diameter and temperature, wrinkle-free parts with deeper draws could be produced. An enhancement in LDR from 2.06 in conventional deep drawing to 2.16 in warm deep drawing with a lower blank holding pressure is achieved. The lower blank holding pressure leads to lesser thickness variation in the product this reducing the occurrence of fracture at the punch radius. The hydraulic counter pressure helps in reduction of wrinkles and enhancement of formability. The improvement in the LDR was observed around 200°C for warm deep drawing. This process reduces the forming restrictions of many materials, can produce complicated shapes and reduces the costs of material and die.

Abstract: Titanium and its alloys are difficult-to-form materials due to limited slip system and plastic anisotropy. Titanium is also prone to change in color due to oxidation at high temperatures. It is thus advisable to conduct deep drawing of titanium and its alloys at temperatures below 600°C. In this study, the drawability of Ti-6Al-4V sheet is evaluated in respect to the process parameters such as forming temperature, forming speed, and blank holding force at elevated temperatures. It is shown that the limit drawing ratio (LDR) increases with increasing temperature, but varies insignificantly with forming speed. The development of residual stresses in the wall of drawn cups during deformation was evaluated.