Experimental investigation on forming limit curve at elevated temperature through dome and biaxial test

The characteristics of metal and materials are veryimportant to design any component so that it should not fail inthe life of the service. The properties of the materials are alsoan important consideration while setting the manufacturingparameters which deforms the raw material to give the designshape without providing any defect or fracture. For centuriesthe commonly used method to characterize the material is thetraditional uniaxial tension test. The standard has been createdfor this test by American Standard for Testing Materials(ASTM)-E8. This specimen is traditionally been used to testthe materials and extract the properties needed for designingand manufacturing. It should be noted that the uniaxial tensiontest uses one axis to test the material i.e., the material is pulledin one direction to extract the properties. The data acquiredfrom this test found enough for manufacturing operations ofsimple forming where one axis stretching is dominant. Recentlya sudden increase in the usage of automotive vehicles results insudden increases in fuel consumption which results in anincrease in air pollution. To cope up with this challenge federalgovernment is implying the stricter environmental regulation todecrease air pollution. To save from the environmentalregulation penalty vehicle industry is researching innovationwhich would reduce vehicle weight and decrease fuelconsumption. Thus, the innovation related to light-weighting isnot only an option anymore but became a mandatory necessityto decrease fuel consumption. To achieve this target, theindustry has been looking at fabricating components from highstrength to ultra-high strength steels or lightweight materials.This need is driven by the requirement of 54 miles per gallon by2025. In addition, the complexity in design increased wheremultiple individual parts are eliminated. This integratedcomplex part needs the complex manufacturing forming operation as well as the process like warm or hot forming formaximum formability. The complex forming process will inducethe multi-axial stress states in the part, which is found difficultto predict using conventional tools like tension test materialcharacterization. In many pieces of literature limiting domeheight and bulge tests were suggested analyzing these multiaxial stress states. However, these tests limit the possibilities ofapplying multi-axial loading and resulting stress patterns dueto contact surfaces. Thus, a test machine called biaxial test isdevised which would provide the capability to test the specimenin multi-axial stress states with varying load. In this paper, twoprocesses, limiting dome test and biaxial test wereexperimented to plot the forming limit curve. The forming limitcurve serves the tool for the design of die for manufacturingoperation. For experiments, the cruciform test specimens wereused in both limiting dome test and biaxial test and tested atelevated temperatures. The forming limit curve from both testswas plotted and compared. In addition, the strain path,forming, and formability was investigated and the differencebetween the tests was provided.