AZ31Magnesium Alloy Sheet High Temperature Forming Limit Diagram Theory To Obtain

Compared with other structural materials, magnesium alloys have manyadvantages. e.g. low density, high ratio of strength and stiffness to mass, no pollution,easy recycle and so on. They have wide application in the fields of automotive,aerospace and3C. However, due to hexagonal close-packed structure (HCP), whichleads to a poor forming capacity at room temperature, the processing of magnesiumalloys has to be focused on die casting, general casting and plastic forming ofcomponents with simple shape. the plastic forming of magnesium alloys has not beengradually applied in industy until hot stamping technology is developed these years.Forming limit diagram (ab. FLD) is one of important tools used for stampingtechnology of sheets, its data usually comes from punch bulging test. But in order toobtain FLD under high temperature, it is not only affected by man-made factors andconsume large amounts of material,but aslo needs to equipped with independentheating device for ensuring the forming conditions, there is a longer testing cycle atthe same time. So people are more comfortable with theory method for forming limitdiagram. But there is no system and accurate theory method for predicting FLD thathas rate of relevant material up to now. Based on this problem, this paper adopts theAZ31magnesium alloy material, around the theoretical derivation and the finiteelement simulation method to study the forming limit diagram. This paper is dividedinto five chapters, The article main content is as follows:At first, I have found the most suitable temperature and strain rate condition formagnesium alloy materials by uniaxial tensile test that has done under differentconditions, and calculate some basic performance parameters that is preparation forthe subsequent theoretical analysis and the finite element simulation. The materialschosen by experiments are AZ31sheet material, and whose grain size reached100μm,it is very representative of what we used in the industry.Second, because of theoretical method for forming limit diagram is mainly basedon the material’s yield criterion, plastic constitutive equation，and combined with theinstability criterion to determine the material fracture. the paper used in Rossardviscoplastic equation and Hosford yield criterion, according to the theory of M-Kgrooves, Application of computer software Matlab write the corresponding code andcalculate the ultimate strain under different stress paths, Resulting in magnesium alloy under high temperature forming limit diagram, and were compared with the testcurve.Finally, the paper apply the finite element software—Dynaform to simulateNakazima hemispherical punch bulging test. However, due to the finite elementsimulation itself can’t show material’s necking or uneven deformation process ofmaterial, and the embedded forming limit diagram calculation formula with the realcurve are much differents. So the paper give four different ways which is use forjudgment of instability according to the state of stress and strain in the process ofcalculation, then obtained the ultimate strain by calculation which put into use thosetwo kinds of methods.In this paper through the theoretical method comparison successfully predictedthe high temperature environment of magnesium alloy sheet forming limit diagram, itcan be used for the actual production process to provide theoretical guidance, and alsocan be used as a judgment of extreme conditions in finite element simulation. Moreimportantly, this paper used the theoretical prediction methods for high-temperaturerate-sensitive material forming limit diagram, which including the M-K the groovestheory and finite element analysis method, for the further complex forming processresearch provides valuable thinking.