extended postprocessing for casting simulations
TRANSCRIPT
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WHY EXTENDED POSTPROCESSING?
Better utilisation of simulation results
The appropriate design of a casting is determined significantly faster using computer aided development methods. An ideal layout of cavity and gating avoids costly mould changes and the postprocessing operations involved. Thus casting simulation reduces development time, costs and increases competitiveness.
The success of the simulation depends on the interpretation of the calculation results and how easily it can be transferred to the casting process. Particularly for complex processes like mould filling, the simulation results can only partly be interpreted directly and extensive experience is needed. In order to take advantage of casting simulation results to full extent with respect to mould construction and the design of casting processes, NMF develops postprocessors which facilitate this task. Especially for the evaluation of mould filling in casting, a product has been created which is an integral part of our modelling process: FlowViz, which visualizes mould filling processes in different and advantageous ways.
HOW DOES FlowViz WORK
Calculation of flow paths
Commercial casting simulation programs typically calculate and describe the mould filling based on the Eulerean approach, i.e. the process is described by stationary vector fields, which reflects the real material flow only indirectly. Hence FlowViz has been developed, which calculates the actual flow paths from the casting simulation results and analyses them regarding to their lengths (flow length). Thus the caster has a visualisation of
l the flow lengths,
the distribution of
l the flow times
and
l the filling pattern of the component
at his disposal for evaluating the mould filling and finding the ideal mould design. The filling pattern is visualized by the trajectories or pathlines of the mould, the velocity is given in different colors.
Extended Postprocessing for Casting Simulations
A mould filling calculation of an automatic gearbox housing evaluated with FlowViz: filling pattern (left) and flow length distribution (right); (courtesy of Georg Fischer GmbH, Munich and ZF Friedrichshafen AG, Friedrichshafen).
Evaluation and comparison of a calculation with experimental observations illustrated by a simple step plate. The filling pattern and the flow length distribution indicate areas with casting defects.
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WHICH CONCluSIONS CaN BE DRaWN FOR THE CaST PaRT?
Quantification of mould filling
The mould filling of components should occur homogeneously and with short flow paths, in order to avoid casting defects already during the filling process. Apart from that, experience has shown that materials with a strong mixture of various flow lengths or flow times very often show flaws like entrapped gases. Also, in areas where significantly different flow lenghts or flow times meet, discontinuities (pores, cold flow) can occur. The filling pattern shows the velocity and the direction of the metal inside the mould. Critical spots of high (wear!) or low velocities (congestion) can be identified immediately. These criteria make it possible for the operator to compare different designs of casting moulds and to classify them. He can base his decision on static pictures and is not confined to video sequences which depict the filling process. Information is concentrated, quantifiable and easy to compare.
HOW CaN CaSTING SImulaTION BE aPPlIED IN THE DEVElOPmENT STaGE?
modelling accompanies innovation
NMF works on the innovative application of simulation technology in the casting industry. Currently, investigations and development on the following topics are carried out:
l Further development of criteria for a better evaluation of how casting defects form and finding strategies to avoid those
l Reduction of mould wear and increase of mould lifetimev
l Description of the rheology of thixotropic metal melts and modelling of Thixomolding
®
l Automatic optimisation of casting moulds
WHaT CaN WE DO FOR YOu?
You design – we do the virtual testing!We at NMF carry out casting simulations for optimising processes and components and offer you our wide range of services:
l Consultancy and information about the possibilities and application of modelling methods
l Calculations for mould filling, solidification and cycles for low and high pres
sure die casting as well as permanent mould casting of both aluminium and magnesium. Further casting methods and materials on request.
l Calculation of the residual stresses and deformations in cast parts
l Virtual trials of casting processes and components to assure ideal design
l Special evaluations on demand of the customer
NMF is fully equipped with all necessary tools (multiple simulation plattforms, thermophysical databases, CAD) which are constantly expanded by the development of special software tools, e.g. FlowViz. CAD files of all standard systems can be processed.
Investigation and evaluation of different gatings for a casting (steering support pump bracket) based on fill pattern and flow length distribution (courtesy of BMW AG, Munich)
Contact
www.nmfgmbh.de
Neue Materialien Fürth GmbHDr.MackStraße 8190762 Fürth
EMail: [email protected]