1、1）QuantorForm Ltd., Moscow, Russia2） MICAS Simulations Ltd., UK3）IUIT, Beijing, ChinaAbstractThe paper presents the experience of aluminium profile extrusion simulation using QForm-Extrusion program. Due to non-uniform material flow the profile that leaves the orifice may bend, twist or buckle. The
2、goal of the simulation is to predict this undesirable shape deterioration and to find ways to minimize it. The program has special interface for fastest die geometry import. The program automatically finds bearing zones and converts them into parametric form allowing modification of bearing design w
3、ithout return to original CAD model. Alterations and optimization can be done by using a special module “Bearing Editor”. In turn with simulations the user can modify die design to achieve the most uniform distribution of longitudinal velocity. The simulation also provides comprehensive analysis of
4、the tool stresses and deflection taking into accounts all the components of the tool assembly. Coupled mechanical simulation mode allows to analyse the influence of the die deflection on the material flow and to compensate this effect. To take into consideration the gradient of the temperature acros
5、s the die and mandrel during the entire process cycle a transient coupled thermo-mechanical model has been built on the basis of QForm-Extrusion program. The software is in use at many die making and extrusion companies showing its high economic efficiency.Keywords: Extrusion, aluminum, profiles, di
6、es, FEM, simulation.IntroductionQForm-Extrusion is a special-purpose program for aluminium profile extrusion simulation that has been developed by QuantorForm Ltd. It shares postprocessor with the versatile metal forming simulation program QForm3D but is actually a stand-alone application. The extru
7、sion model is based on Lagrange-Euler approach 1. The model also includes the assumption that the tool set is completely filled with the material prior to the beginning of the simulation thus the solution is to be found in the domain that is inside of the tooling set. On the other hand the free end
8、of the profile increases in length very quickly after passing through the orifice. Due to non-uniform material flow the profile that leaves the orifice may bend, twist or buckle. The simulation is capable of predicting this undesirable shape deterioration and finding ways to minimize it. Validation
9、of the model has been performed for prediction of load, material flow pattern, profile temperature and die deformation using special model experiments and numerous industrial case studies 2. Comprehensive analysis of the program accuracy has been also done within the International Extrusion Benchmar
10、k Tests in 2007, 2009 and in 2011 （see, for example, 3, 4） by means of comparison of the simulation results with precisely measured experimental data. The numerical formulation of the model as well as methods of solving coupled problem are described in our works 5-7.Verification of the model using l
11、aboratory experimentsThe numerical model described above has been tested to find out the influence of the die deformation on the material flow. Die deflexion is difficult to measure thus especially dedicated laboratory tests are to be performed. One of such tests has been done as a case study for th
12、e Extrusion Conference and Benchmark ICEB 2009 and it has been reported in 8 where the data summary and experimental results can be found. Using these source data we have done the simulation for two cases considering the assumption of rigid and deformable dies. The profiles sketch and the tooling se
13、t drawing are shown in （Fig. 1）.As seen from the drawings both profiles are identical and are placed using rotational symmetry on the die plate. Thus there are no reasons for the material to flow differently through both orifices except it may be caused by different deformation of the die within the
14、m. This may happen because one of the tongues intentionally has been done with longer support than the other. In （Fig. 1, b） these two tongues are marked as “less supported” and “fully supported” ones. The experiment has shown the difference in the displacement of the tongues about 0.5 mm with respe
15、ct to each other that potentially may cause the difference in material flow 8. The displacement distribution on the die surface obtained by our simulation using the presented model is in （Fig. 2）. It is clearly seen that both tongues deform differently. Moreover, each tongue has different displaceme
16、nt on its container side that is close to bearing area comparing to its outlet side where the experimental measurement of the deflection has been actually done. Meanwhile overall deflection of the die is probably less important than local distortion of the bearing that actually controls the material
17、 flow （Fig. 2 c）. Opposite sides of the bearing have different displacement and they slightly shift with respect to each other. The result of this deformation is variation of the bearing angle and change of “effective” bearing length. This alteration of actual bearing shape may influence the materia
18、l flow conditions in both channels that in our case are different due to different tongue support.To check how effectively the coupled numerical model of extrusion may detect the influence of the die deformation on the material flow the test described above has been simulated two times, i.e. once us
19、ing the rigid die and secondly with elastically deformable die using the coupled model. In the first case with the rigid die both profiles flow similarly with just slight bent towards each other. It is important to notice that in this case there is no bend of the profile in its symmetry plane （see F
20、ig. 3 a）. a. b. Fig 1. The scheme of the profiles used for the test （a） and crosscut of the die done through the tongues showing different support conditions （b）. Both pictures are taken from 8. a. b.c.Fig. 2. The axial displacement of the die in mm shown from the container side （a） and from the out
21、let side （b） and local displacement of the bearing area （c）. Colour scale shows the value of the displacement while pink contour in （c） is the deformed shape of the bearing magnified for better visibility.When the simulation has been performed using the deformable die the profile with less supported
22、 tongue bents in the plane parallel to its legs towards its bridge （Fig. 3 b）. The same bending direction of the profile going from the orifice with less supported tongue has been reported by the authors of the experimental work 8 （compare pictures on Fig. 3 b and c） even though it is difficult to e
23、stimate their correspondence quantitatively because no information about the bending radius is available. Nevertheless we can conclude that die deformation may cause some effect on material flow and taking it into account in simulation by means of coupled modeling provides higher accuracy of the num
24、erical results. a. b. c.Fig. 3. Simulation of the test extrusion: with the rigid die both profiles go straight （a）; with deformable die one profile bends in direction parallel to its legs （b）; photo of the experiment 8 with one profile bending （c）.The die deformation and material flow in industrial
25、case studyTheeffect of die deflection on material flow may not always be significant and probably in many cases the simulation with the assumption that the die is rigid provides sufficient accuracy for practice. Meanwhile in cases when the die has long tongues or it is designed for complex hollow pr
26、ofiles when mandrels are supported by narrow and relatively flexible bridges the die deformation may be critical. In such cases it is impossible to achieve the accuracy required by practice without use of coupled modelling as it is illustrated by the following industrial case study.Let us consider e
27、xtrusion through the die shown on （Fig. 4）. Thisis profilewithrectangularcentralholeandtwostructural stepped open sides. a. b. Fig. 4. The die for production of the profile shown from container （a） and exit （b） sides. The simulation model as it is seen in the program is shown on （Fig. 5）. It include
28、s the material flow simulation domain and then respectively the die, the mandrel and the bolster assembled together. Fig. 5. The simulation setup in QForm-Extrusion with the die set while no container is shown. The material flow domain consists of 341405 nodes while tool set model consists of 241071
29、 nodesThe simulation has been done for two variants, firstly, using “rigid” dies and, secondly, using coupled simulation when the dies deformation may influence the material flow. Extruded material was AA6060, ram speed 8 mm/s, initial billet temperature 480oC, the die temperature 400oC. Thematerial
30、flowthroughthe “rigid” dieisshownon （Fig.6）. The central rib goes slower than the opened sides of the profile. This materials flow causes to considerable bending of the profile that is shown in the Fig. 6c.a. b. c.Fig. 6. Sequential steps of the material flow simulation in case of “rigid” dies. The
31、beginning of the process （a）, intermediate stage （b） and formation of the profile front tip （c）. The experimental observation didnt confirm the material flow pattern that was obtained in the variant of simulation with “rigid” dies. The most probably the deformation of the dies was the reason of such
32、 discrepancy. Simulation of the tool set has indicated the considerable displacement of the central part of the mandrel in the extrusion direction.Thespiderdisplacementreaches0.575 mm in the extrusion direction Z （Fig.7）. The movement of the spider in Z and Y directions become the reason of the inclining of the bearing walls. So in some aria we have
