III. NUMERICAL SIMULATION
An attempt is made to simulate the semisolid metal process using finite element simulation software. The following simulations were carried out on Aluminum alloy A356 to determine the effect of initial temperature of the billet on the forging load. The simulations were carried out at different temperatures between the solidus and liquidus temperature range of the alloy.
The position of the billet on the bottom die was determined by placing it in different positions and also for various temperatures. The present location was finalized after studying the aspect of under filling of die cavity and also dimensional accuracy of the component. Initially the dies and the work piece were modeled in Solid Works and were exported...
The material chosen for the work piece is A356 and for the dies AISI H – 26. A top die speed of 10mm/sec and a friction coefficient of 0.3 between the work piece and billet were chosen. The dies and billet were modeled to exchange heat with the ambient surroundings. The initial size of the billet was taken as 75L X 60 H X 75W. A simple shaped stepped component is to be achieved at the end of simulation. Initially the billet was placed in different positions in the die cavity and the process was simulated. After a few trials the position of the billet was finalized.
Fig. 1 Position of Dies and Billet at the Fig. 2 2D drawing of the stepped component
start of the process
The study was carried out by varying the temperature of the billet and keeping all the other parameters constant. Fig 1 shows the initial position of the billet in between the top die and bottom die. The final shape of the aluminum component is shown in fig.2. The simulation was carried out with the initial temperatures of the billet at 560oC, 580 oC, 600 oC and 620 oC. The parameters of loads applied and the displacement of die were observed at the simulation progressed.
Figure 3 Billet at the end of simulation Figure 4 Location of points where the temperature profile was...
As the value of solid fraction reduced in the material the load that needs to be applied for the same displacement decreased. There is a slight increase in the applied load when the billet temperature increased to 620 oC. This could be attributed to the increased displacement of top die.
With increase in temperature of the billet there was a reduction in the displacement of the top die. The variation in the load was uniform as the simulation progressed. The variation in the applied load vs. displacement of die at different initial temperatures of billet is plotted as shown in fig. 5. Graphs are plotted to study the variation in temperatures across the billet as the simulation progressed. Fig. 4 represents the plot between temperature and time when the initial temperature of the billet was 580 oC. However when the billet temperature was 620 oC, the die displacement has increased. The billet temperatures at the end of the simulation were also in conformity to the general understanding of the...
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