Sigurd Støren

The theory of extrusion—Advances and challenges

Abstract Plane-strain slip-line field theory, upper bound analysis and the visioplasticity technique form the basis for the mechanics of extrusion. Bishop [ Metall. Rev. 2, 361 (1957)] pointed out in 1957 that to make the theory useful in practice, one had to use the mechanics of extrusion to quantify phenomena that were primarily metallurgical, such as speed-limit phenomena, flow resistance, the evolution of microstructure and properties of the extrudate. Time has shown that the gap between the metallurgy of extrusion and the mechanics of extrusion was of such a character that only in recent years, by the full impact of computer simulation with thermomechanical coupling and realistic constitutive formulation of thermoviscoplastic solids, has one seen that the mechanics and metallurgy of extrusion have begun to emerge into a unified theory of extrusion. The main challenge is now to develop the theory of plasticity and constitutive models that can handle metallurgical reactions and the development of microstructure in the sharp rates and gradients of strain rate and temperature observed in extrusion. Another important challenge to the theory of extrusion is to transform basic knowledge about extrusion and the subsequent manufacturing processes into a form that is useful in product design engineering. The practical part of this review focusses on unlubricated extrusion of aluminium alloys and on product and process development related to aluminium extrusions.

Sustainable Product Design — Is there more to it than Science, Systems and Computers?1

The conditions are examined through which a company can take an active part in the evolutionary process towards ecologically sustainable societies. Productivity measures, quality perceptions, ecological performance and critical contradictions between business targets have to be identified, based on systematic retrieval and structuring of information of product, processes and practices. It is important that the company selects ecological performance parameters and sets performance targets which show the way towards ecologically sound products, processes and practices and at the same time secure its competitiveness in todays market. It is suggested that an extended quality function deployment process (QFD) can be used for this purpose. By combining this information structure with the modelling possibilities of products, processes and practices that are available in modern computer assisted engineering software (CAE), consequences and feasibilities of new ideas and creative solutions can be checked out continuously. New ideas and creative solutions that really will lead the way towards ecologically sustainable societies, seem to require development- and design-teams that are getting inspiration, visions and wisdom from other areas than the conventional business and university environment. Close cooperation should be encouraged between industry and the universities for building up such inspired environments.

Role of temperature on sliding response of aluminum on steel of a hot extrusion

In the present investigation, a series of sliding and tensile tests were conducted to simulate interactions at the bearing surface. A spherical tipped aluminum pin was slid against a polished steel ring. Results showed that the friction coefficient at all test temperatures of sliding exhibited a near similar pattern of peak followed by a gradual drop and stabilization. The steady state friction coefficient was 0.2 for temperatures up to 423 K, and greater than 1.0 for temperatures above 423 K. The transfer layer evolution was dependent on friction force. The ultimate tensile strength decreased at temperatures higher than 423 K.

Hot Metal Extrusion

The paper focuses on the main scientific problems related to hot metal extrusion of thin walled tube, strip and sections, covering analytical approach, 2D- and 3D-numerical simulation and experimental validation. The main physical phenomena and parameter estimation related to thermo-mechanical constitutive equations, shear localization, bearing channel, dry hot friction and metal flow stability in extrusion is treated. The scientific, generic insight and knowledge of these extrusion phenomena should be considered as precompetitive. In industry this knowledge must be integrated with practical experiences and skills in order to be able to predict and control dimensional, surface and microstructure variability during a press cycle, and inspire to innovations in the field of extrusion and its down stream processes such as tube drawing, cold forging, bending and hydroforming.

Optical Measurement Technology For Aluminium Extrusions

Optical measurement techniques such as laser scanning, structured light scanning and photogrammetry can be used for accurate shape control for aluminum extrusion and downstream processes. The paper presents the fundamentals of optical shape measurement. Furthermore, it focuses on how full‐field in‐ and off‐line shape measurement during pure‐bending of aluminum extrusions has been performed with stripe projection (structured light) using white light. Full field shape measurement is difficult to implement industrially, but is very useful as a laboratory tool. For example, it has been clearly shown how moderate internal air pressure (less than 5 bars) can significantly reduce undesirable cross‐sectional shape distortions during pure bending, and how buckling of the compressive flange occurs at an early stage. Finally, a stretch‐bending set‐up with adaptive shape control using internal gas pressure and optical techniques is presented.

Aluminum Rod Extrusion and Material Modeling

The article presents an outline of a scientific approach for testing constitutive relations for the aluminum extrusion process. By comparing ram force, container friction, die face pressure, outlet temperature measurement during rod extrusion with corresponding simulated data, inferences can in principle be drawn with respect to the validity models. The paper indicates that simulation results from the 2D ALMA2π program are in fair agreement with measurements during extrusion of AA6060, but more work needs to be done to control thermal conditions during extrusion.

NORDLIST LCA, Lifecycle Assesment in Product Development

The goal for the NORDLIST LCA-project was to develop methodologies and tools for Life Cycle Assessment (LCA) to visualise ecological consequences of product modifications and product redesign for the designer. The NORDLIST LCA-project developed in 1996 a prototype version of an LCA-software suite, for evaluating the ecological consequences of a product through its lifespan.