There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Effect of laser surface texturing on Si3N4/TiC ceramic sliding against steel under dry friction

Nanoscale and microscale textures with different geometrical characteristics were fabricated on the surface of the Al 2 O 3 /TiC ceramic tool, and molybdenum disulfide (MoS 2 ) solid lubricants were burnished into the textures. The effect of the textures on the cutting performance was investigated using the textured self-lubricated tools and conventional tools in dry cutting tests. The tool wear, cutting force, cutting temperature, friction coefficient, surface roughness and chip topography were measured. Results show that the cutting force, cutting temperature, friction coefficient and tool wear of nanoscale and microscale textured self-lubricated tools are significantly reduced compared with the conventional tool, and the developed tool with wavy microscale textures on the rake face is the most effective in improving the cutting performance. The textured self-lubricated tools increase the surface roughness of machined workpiece, while they can reduce the vibration for a stable cutting and produce more uniform surface quality. The chip topography is changed by the textured self-lubricated tools. As a result, the nanoscale and microscale textured self-lubricated tools effectively improve the cutting performance of conventional Al 2 O 3 /TiC ceramic tool, and they are applicable to a stable dry cutting of the hardened steel.

Cutting performance and wear mechanism of nanoscale and microscale textured Al2O3/TiC ceramic tools in dry cutting of hardened steel

Metal forming processes operate in conditions of uncertainty due to parameter variation and imperfect understanding. This uncertainty leads to a degradation of product properties from customer specifications, which can be reduced by the use of closed-loop control. A framework of analysis is presented for understanding closed-loop control in metal forming, allowing an assessment of current and future developments in actuators, sensors and models. This leads to a survey of current and emerging applications across a broad spectrum of metal forming processes, and a discussion of likely developments.

Closed-loop control of product properties in metal forming

Materials in machine tool structures

In this paper, macroscopic textured tool surfaces manufactured by rolling are investigated. Focus is on selective adjustment of friction by local texturing of tool areas to influence the material flow during deep drawing operations. Flat strip drawing tests were performed using friction elements with open textures. The texturing influences the friction conditions and affects the material properties of the stripes. The use of these surfaces results in a significant increase in friction, which allows an additional control of the material flow during sheet drawing operations. The main mechanisms for increased drawing forces are elastic deformation near the area of the texture and local plastic deformation on the sheet surface. Using strips made of mild steel, the texturing leads to an increased roughness of the sheet metal surface and, in the case of high surface pressure, to plastic deformations of the strips. Compared to conventional measures like draw beads, rolled-textured surfaces allow to retard the material flow during sheet drawing operation without excessive strain hardening in the sheet material.

Textured surfaces for deep drawing tools by rolling

This paper focuses on new forming techniques for the improvement of product quality, the reduction of process chains and the saving of our available resources. The presented and discussed technologies cover extrusion of reinforced profiles, bending of profiles, single point incremental forming of polymers, and tool systems made of polymers coated by hard metal as well as re-manufacturing strategies. Beside the process principles and advantages several results from numerical and experimental investigations will be given in order to show the motivation for fundamental and application oriented research in the field of forming technology.

Innovation by forming technology: motivation for research

Processing high strength sheet metal materials causes high tribological loads to the surface of forming tools. To increase the wear resistance and therewith the service time of tools, surface coatings containing hard materials are applied by thermal spraying. In the initial “as sprayed” state, the coatings show a rough surface and porous structure, which is not suitable for sheet forming tools. This article describes the finishing of the coatings by subsequent roller burnishing. By the rolling process surface asperities of the coating are flattened and the contact area between the finished surface and the sheet is increased. Furthermore, residual compressive stresses in the surface zone are generated by the rolling process. The tribological properties of the coated and finished surfaces are analyzed in strip drawing tests with uncoated DP600 sheets varying the contact pressure and drawing velocity. It is shown that the process parameters of the roller burnishing process have a strong influence on the surface topology of the friction elements and their tribological properties. The coated and finished friction elements are compared to conventional grinded steel friction elements, made of C60.

Finishing of Thermally Sprayed Tool Coatings for Sheet Metal Forming Operations by Roller Burnishing

The paper concentrates on investigation results dealing with ultra high performance concrete (UHPC) dies for the use in sheet metal hydroforming. A special mixture of UHPC for these tools with its mechanical properties and its manufacturing is presented. The developed UHPC features a compressive strength of approx. 250 MPa and a Young’s modulus of approx. 50 GPa. Applying internal pressure, the UHPC die (without confinement or reinforcement) failed between 80 and 96 MPa. The forming test proved a good shape accuracy of the sheet metal parts but revealed critical tribological conditions. Drawing foil and already formed sheet metal parts were tested successfully as interlayer and led to an appropriate material flow and surface quality of the sheet metal parts.

Michael Trompeter

Papers

Textured surfaces for deep drawing tools by rolling

Innovation by forming technology: motivation for research

Finishing of Thermally Sprayed Tool Coatings for Sheet Metal Forming Operations by Roller Burnishing

Development of ultra high performance concrete dies for sheet metal hydroforming

High wear resistant deep drawing tools made of coated polymers