Enzyme‐induced ferrification of hydrogels for toughening of functional inorganic compounds

Enzyme-induced mineralization (EIM) has been shown to greatly enhance the mechanical properties of hydrogels by precipitation of calcium salts. Another feature of such hydrogels is their high toughness even when containing finely nanostructured mineral content of ≈75 wt%. This might be useful for bendable materials with high content of functional inorganic nanostructures. The present study demonstrates that EIM can form homogeneous nanostructures of water-insoluble iron salts within hydrogels. Crystalline iron(II) carbonate precipitates urease-induced within polyacrylate-based hydrogels and forms platelet structures that have the potential of forming self-organized nacre-like architectures. The platelet structure can be influenced by chemical composition of the hydrogel. Further, amorphous iron(II) phosphate precipitates within hydrogels with alkaline phosphatase, forming a nanostructured porous inorganic phase, homogeneously distributed within the double network hydrogel. The high amount of iron phosphate (more than 80 wt%) affords a stiffness of ≈100 MPa. The composite is still bendable with considerable toughness of 400 J m−2 and strength of 1 MPa. The high water content (>50%) may allow fast diffusion processes within the material. This makes the iron phosphate-based composite an interesting candidate for flexible electrodes and demonstrates that EIM can be used to deliberately soften ceramic materials, rendering them bendable

Simulation based prediction of compliance induced shape deviations in internal traverse grinding

Internal traverse grinding (ITG) using electroplated cBN tools in high-speed grinding conditions is a highly efficient manufacturing process for bore machining in a single axial stroke. However, process control is difficult. Due to the axial direction of feed, changes in process normal force and thus radial deflection of the tool and workpiece spindle system, lead to deviations in the workpiece contour along the length of the bore, especially at tool exit. Simulations including this effect could provide a tool to design processes which enhance shape accuracy of components. A geometrical physically-based simulation is herein developed to model the influence of system compliance on the resulting workpiece contour. Realistic tool topographies, obtained from measurements, are combined with an FE-calibrated surrogate model for process forces and with an empirical compliance model. In quasistatic experimental investigations, the spindle deflection is determined in relation to the acting normal forces by using piezoelectric force measuring elements and eddy current sensors. In grinding tests with in-process force measurement technology and followed by measurement of the resulting workpiece contours, the simulation system is validated. The process forces and the resulting characteristic shape deviations are predicted in good qualitative accordance with the experimental results

Prozessoptimierung für das innenrundschälschleifen

Abstract in German:Das Hochleistungs-Innenrundschälschleifen mit galvanisch gebundenen CBN-Schleifwerkzeugen ist ein hocheffizientes Fertigungsverfahren für die Innenbearbeitung von gehärteten Futterbauteilen wie Zahnrädern und Lagerringen. Die konturierten Schleifwerkzeuge, welche mit einer konischen Schrupp- und zylindrischen Schlichtzone versehen sind, kombinieren in einem einzelnen Axialhub ein effizientes Abtragsverhalten mit einer hohen Oberflächengüte. Unter Hochgeschwindigkeitsbedingungen zeigt sich das Potential dieses Verfahrens besonders deutlich. Den Vorteilen des Verfahrens stehen jedoch, bedingt durch die komplexen Eingriffsverhältnisse, Herausforderungen entgegen, die durch den Einsatz eines mehrskaligen Simulationssystems beherrscht werden können