Casting Simulations with STAR-Cast Julian Gänz, CD-adapco
Need for Casting Simulation Processes Permanent Mold Market Overview [Mio tons] Tilt Casting Low Pressure-Casting High Pressure Die 9 19,4 13,6 38,16 Grey Iron Ductile Iron Steel Casting Non Ferrous alloys Continuous Casting... From Modern Casting 2010 world census casting production Lost Mold Sand Casting Precision Casting Centrifugal Bridgeman... Material Cost/tonne [$] Relative Carbon Steel 550 1 Cast Iron 830 1,51 Aluminium/alloys 2220 4,0 Titanium /alloys 17 000 30,9
From Austin Group 2002 Need for Casting Simulation Variety of processes and materials Sophisticated geometries Call for advanced casting processes Simulation can help to meet the different and often contradicting demands Requirements Mold filling with solidification Defect Prediction Design tool 100000 120000 150000 12000 30000 Tool Cost [$]
Strategic Partnership Best of both worlds Provide state of the art of casting simulation solution by combining the engineering experience of two companies which have a long-standing track record in providing CAE solutions and casting processes for over 25 years Established casting solution STAR-Cast
STAR - Cast First released in 2009 Dedicated design and engineering tool for the casting engineer Core -Capabilities Multiphase Resolution of the molten flow and filling front Model phase change Dedicated material database Dedicated User Interface STAR-CCM+ s state of the art meshing
The Process Speaking the language of the casting engineer Quickly adaptable to simulation needs Geometry Any given CAD data 3D-CAD Modeller Mesh Fluid /Solid Interfaces Appropriate meshing models Filling VOF Isothermal- gating design Thermal - cooling/ solidification Particles/ erosion Physics Adapt to simulation goal Expandable Solidification Progress of Solidification Influence on flow Misruns and cold shut Post processing Transient Postprocessing Criteria functions, defect analysis Motion Piston Motion Tilting Rotation
Industrial Challenge - Materials A dedicated Material Database is available in STAR-Cast, pooling all relevant material information for the casting engineer
Industrial Challenge - Solidification Mushy / Slurry Zone Transition from liquid to solid leads to partially solidified areas Carman Kozeny approach Solid - Flow Stop Complete stop of flow in solidified areas Solid Mushy Liquid f L = 0.0 f L = 0.3 f L = 1.0
Industrial Challenge - Defect Prediction Deduct additional information about the solidification process and the overall quality of the cast Gather Temperature gradients, cooling rates and local solidification times Compute criteria functions, such as Niyama or G/v criterion Estimate porosity characteristics centre line porosity Ref: Access, STAR-Cast 1.10
Industrial Challenge - Porous molds Phase selective wall porosities for VOF- Phases Capture the venting effect of a porous mold, core ( i.e. Sand, Investment mold) Porosity to low Calibrated porosity
Industrial Challenge - Complexity Multi region problem... Complex Geometry Fluid Cavity Surrounding Air Different solids ( mold, cooling iron..)... Meshing requirements: Easy surface repair Multi region Volume meshing Prism layers Cell count effective meshing in thin areas
Investment Casting: Shell generation For precision casting Dipping a wax model into a ceramic based slurry Ceramic slurry dries and builds the mold for the casting Wax is removed in an autoclave Automatic shell mold generation
Investment Casting: Shell generation Shell mold generator Mimics a manufacturing process Based on local curvature Investment Casting
Investment Casting Challenges in Investment Casting Thin-walled components with designs at the limit of producibility Late design freeze, thus shorter development cycles New materials New processes Courtesy of Access e.v.
Investment Casting Answers Engineers are seeking Sensitivity analyses for process parameters, running and gating system Geometrical parameter studies Enhancement and conservation of raw materials and reduction of overall manufacturing cost
Example of a mould-filling optimization Crucible Sprue cup Initial setup Optimized setup Courtesy of Access e.v. & CD-adapco
Example of a mold-filling optimization 1 7 Non-optimized Optimized Simulations show that in a non-optimized distributor the liquid metal keeps rotating in the distributor for a longer time before entering the sprue
Investment Casting What kind of Defects are of relevance for Investment Castings: Misruns Porosity Freckles Stray grain formation Segregation Hot tearing
Predictions of misruns in a gravity-cast LPT blade 1 9 Inlet Runner Sprue Blade Shell Mould Schematic diagram of the process Polyhedral Volume Mesh
Comparison of simulation and casting trials Magnitude of velocity Temperature Gravity casting, Access TechCenter Value of secondary dendrite arm spacing was obtained from microstructure measurements Courtesy of Access e.v. & CD-adapco
DS/DX Castings: Stray Grain Formation Stray grains form when corners of the part solidify and there is no connection to the main solidification front. Marked corner will show a stray grain
Looking ahead Enhance accuracy, robustness and ease of use for a wider range of casting processes Include further solidification models Ductile Iron, Grey Iron Composite castings Next STAR-Cast release:» Fully Based on STAR-CCM+
STAR-Cast embedded in STAR-CCM+ : v8.02 Latest solver and meshing capabilities Modern and easy handling All the physics to carry out casting simulations Material Database Shell mold generator Defect prediction Add on module to STAR-CCM+
STAR-Cast embedded in STAR-CCM+: 8.04 Dedicated mesher for investment casting Automated Region generation Prism Layer + Embedded Thin Mesh in thin areas Streamlined Workflow Simple set of input variables
STAR-Cast embedded in STAR-CCM+ : Outlook Process driven GUI for casting applications: New approach to STAR-CCM+ GUI adapts to the selected casting process Best Practices are stored High level of automation Guide the user through process
STAR-Cast embedded in STAR-CCM+ : Outlook Concept Expose only required functionalities Use casting terminology Shorten the learning curve Conditions : reusable Input is stored in an XML file
Casting Simulations with STAR-Cast Julian Gänz, CD-adapco