Comparison of spherical and truncated cone geometries for single abrasive-grain cutting

The purpose of the present work was to compare the cutting action of two different abrasive-grain geometries using experimental observations and a validated finite element model. A spherical tool was used to approximate a dull abrasive grain while a truncated cone tool was used to approximate an abrasive grain with a well defined cutting edge. The selected geometries were chosen to represent extreme cases in order to bracket the cutting action of a range of cutting geometries. The results showed that both tools produced similar normal and tangential forces per unit width up to a depth of cut of approximately 3 μm. The improved cutting geometry of the truncated cone tool caused the normal force per unit width to decrease and the tangential force per unit width to increase in relation to the spherical tool. The truncated cone tool was shown to experimentally and numerically be more efficient based on the reduced pile-up heights and improved stress distributions. It was also shown that both geometries converged towards the same specific energy to displace material at suitably large depths of cut, which suggests that there is a minimum specific energy obtainable for a given workpiece material that is independent of the grain geometry. However, specific energies to remove material were higher for the spherical tool as compared to the truncated cone tool. Analysis of the energy components of the finite element model showed that frictional energy contributions were high with the spherical tool and low with the truncated cone tool. Finally, it was found that both tools required approximately the same energy to shear a chip from a workpiece when friction was subtracted from the specific energy for material removal.     

Prozesskette zum stofflichen Recycling von Kunststoffabfällen

The material recycling rate for post-consumer plastic in Austria currently ranges around 25?%, because only post-consumer plastic fractions which are disposed as clean mono-materials are available for material recycling. A significant enhancement of the material recycling rate can be achieved with a process chain consisting of wet mechanical processing and thermochemical conversion. The wet mechanical process step enriches polyolefin and polystyrene from different waste sources, which are used as feedstock for a solvent-based, thermal depolymerisation. Via thermal cracking petrochemical intermediates (i.e. short- and long-chained, aromatic and paraffinic hydrocarbons) are produced, which can be appropriately fed into a conventional crude oil refinery and processed to marketable products. In this way, the material cycle can be closed economically feasible. Both the wet mechanical processing and the thermochemical conversion have been proofed in laboratory scale and are currently transferred to pilot scale.     

The use of nested desirability functions and quality indices for multi-response robust parameter design problems

A multi-response robust parameter design (RPD) problem-solving technique based on desirability functions is presented in which the means and variances of all responses are placed on a level playing field. The proposal allows a decision maker to integrate their preferences for the individual means and variances. It is shown that the ensuing operating point is a system setting that produces a mutually robust set of responses. In addition, this article offers an approach to assess several RPD strategies via quality indices. The measures presented here allow for a more knowledgeable and comprehensive evaluation of the competing RPD strategies.     

Variable heat flux in numerical simulation of grinding temperatures

In this paper, temperature results obtained by numerical simulations based on three different methods of defining the heat flux load distribution are compared to directly measured temperatures acquired using infrared camera measurement techniques. The heat flux calculations are based on recorded instantaneous grinding power, average grinding power, and power calculated by multiplying the measured tangential forces and the cutting velocity (referred to as calculated power). The results show that the method applied to characterize the input flux load in the numerical model has a significant effect on the estimated grinding temperatures and that the calculated power data produce the best temperature results.     

Power-to-X im Kontext der Energiewende und des Klimaschutzes in Deutschland

In order to examine the impact of different Power-to-X technologies on the transformation of the German energy system and meeting the climate change mitigation goals, a cross-sectoral energy system model was developed. The results show that Power-to-X will be essential for a successful energy transition. Especially in applications where high energy densities are required and only few other options for defossilization exist, Power-to-X technologies become essential.