Showing papers by "Gerhard Hirt published in 2009"

Strategies to improve the geometric accuracy in asymmetric single point incremental forming

Abstract: Asymmetric incremental sheet forming (AISF) is a manufacturing process for the small batch production of sheet metal parts. In AISF, a sheet metal part is formed by a forming tool that moves under CNC control. AISF currently has two dominant process limits: sheet thinning and a limited geometric accuracy. This paper focuses on the latter limit. It is shown with a pyramidal part that multi-stage forming can yield an increased accuracy compared to single-stage forming. However, due to residual stresses induced during forming, the accuracy of the as-formed part can be lost if the part is trimmed after forming. A case study with a car fender section shows that the geometric accuracy of the final part can be improved compared to single-stage forming by a combination of multi-stage forming and stress-relief annealing before trimming.

Thixoforming : semi-solid metal processing

Abstract: Preface SEMI-SOLID FORMING OF ALUMINIUM AND STEEL ' INTRODUCTION AND OVERVIEW Introduction Early Work on Flow Behaviour and Technology Development Today's Technologies of Semi-Solid Metal Forming PART I: Material Fundamentals of Metal Forming in the Semi-Solid State METALLURGICAL ASPECTS OF SSM PROCESSING Introduction Temperature Sensitivity S* and Solid-Liquid Fraction Slurry Formation in the Rheo- and Thixo-Routes Proneness to Segregation and Hot Tearing Impact of Variations in Alloy Composition Conclusion MATERIAL ASPECTS OF STEEL THIXOFORMING Introduction Background Alloying Systems Structural Parameter Development and Material Selection Melting Behaviour Microstructure Analysis and Material Properties Conclusions DESIGN OF Al AND Al-Li ALLOYS FOR THIXOFORMING Production of Raw Material for Thixoforming Processes Chemical Grain Refinement of Commercial Thixoalloys Fundamentals of Aluminium-Lithium Alloys Development of Aluminium-Lithium-Alloys for Semi-Solid Processing Consideration of the Forming Pressure on Thixoalloy Development Preparation of Principle Components from Al-Li Thixoalloys Production of Al-Li Demonstrators by Rheocasting Recycling of Aluminium-Lithium Alloys from Thixoforming Processes THERMOCHEMICAL SIMULATION OF PHASE FORMATION Methods and Objectives Calculations for the Tool Steel X210CrW12 Calculations for the Bearing Steel 100Cr6 Calculations for the High-Speed Steel HS6-5-2 PART II: Modelling the Flow Behaviour of Semi-Solid Metal Alloys MODELLING THE FLOW BEHAVIOUR OF SEMI-SOLID METAL ALLOYS Empirical Analysis of the Flow Behaviour Numerical Modelling of Flow Behaviour Simulation of Cooling Channel A PHYSICAL AND MICROMECHEMICAL MODEL FOR SEMI-SOLID BEHAVIOUR Introduction Basic Concepts of Micromechanical and Homogenization Modelling Semi-Solid Behaviour Results and Discussion Conclusion PART III: Tool Technologies for Forming of Semi-Solid Metals TOOL TECHNOLOGIES FOR FORMING OF SEMI-SOLID METALS Introduction ' Suitable Tool Concepts for the Thixoforming Process Thin-Film PVD/PECVD Coating Concepts for Die Materials PVD and PECVD Coating Technologies Multifunctional PVD Composites for Thixoforming Moulds Developing Al2O3 PECVD Coatings for Thixoforming Moulds Bulk Ceramic Forming Tools Conclusions and Perspectives PART IV: Forming of Semi-Solid Metals RHEOCASTING OF ALUMINIUM ALLOYS AND THIXOCASTING OF STEELS Casting of Semi-Solid Slurries SSM Casting Processes Thixocasting of Steel Alloys Rheoroute Assessment and Outlook THIXOFORGING AND RHEOFORGING OF STEEL AND ALUMINIUM ALLOYS Introduction Forging in the Semi-Solid State Heating and Forming Operations Simulation of the Thixoforming Process Conclusion THIXOEXTRUSION Introduction State of the Art Tool Concepts Isothermal Thixoextrusion Non-Isothermal Thixoextrusion Conclusion

Comprar Thixoforming: Semi-solid Metal Processing | Gerhard Hirt | 9783527322046 | Wiley

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Analysis of semi-solid extrusion products made of steel alloy X210CRW12

Abstract: The bar extrusion process is characterised by extruding a billet through a forming die with a punch. Compared to conventional bar extrusion other tool concepts are required for semi-solid extrusion processes because forming has to take place in the semi-solid state, followed by a solidification step [1]. Under variations of the main process parameters like press velocity, extrusion channel length and die as well as the press channel geometry semi-solid extrusions are performed. The bars are characterised by a limited length due to insufficient solidification in the extrusion channel. Analyses concerning chemical composition, pore formation, microstructure and mechanical properties discover properties independent of the chosen process parameters. The chemical composition is constant over the bar length. It differs between globulites and eutectic. In the homogeneous microstructure few pores can be found. The determination of the mechanical properties shows a wide range of values because of the pores included in the bars.

Comparison of some Final Part Geometrical Characteristics of Cylindrical Cups Manufactured by Deep-Drawing and Two-Point Incremental Sheet Forming

Abstract: Asymmetric incremental sheet forming (AISF) is a new sheet metal forming process in which sheet metal parts are produced by CNC-controlled movements of a simple ball-headed forming tool Despite its flexibility and successful application in many cases, AISF has not yet been established in an industrial context due to some still existing process limits such as severe thinning, which strongly depends on the inclination of the part surface, as well as a limited geometric accuracy due to springback Furthermore, there is little knowledge available about the properties of parts produced by AISF, especially in comparison to deep-drawn parts The aim of the present paper is to compare cylindrical cups manufactured by deep-drawing and AISF regarding the resulting strain and thickness distribution For AISF, different forming strategies were applied Comparisons of the wall thickness and surface strain distributions show similar results for the cup produced by deep-drawing and the best cup produced by AISF, but the surface strains and the sheet thinning in the parts formed by AISF were larger than in the deep-drawn part

Semi-solid forging and joining of steel components and their properties

Abstract: This paper shows the possibility of producing demonstrating components by combining the forming operation with a simultaneous insertion of additional components. With this technology it is possible to shorten conventional process chains and to create a new generation of components. As base materials two different steel alloys are used, the low melting cold forming tool steel X210CrW12 and the bearing steel 100Cr6. As insert materials steel alloys as well as copper based alloys are considered. Consequently, the main challenges for this technology are the embedding of the inserts into the semi-solid matrix without destroying the geometry due to deforming or remelting. To characterise the produced components concerning their microstructure development and resulting material properties optical and mechanical testings were carried out. As result it could be shown that the die filling and the embedding of the inserts were feasible. The development of the microstructure of the solidified material was influenced by the geometrical conditions which also cause differences in the mechanical properties. Furthermore, there could be shown design restrictions which have to be considered in future to avoid the damaging of the inserted components.