Influence of Rice Variety and Freezing on Flour Properties

Two rice varieties were used to study the effect of freezing and grinding processes on rice flour properties. The freezing and grinding processes followed by sieving mainly affected the particle size distribution, starch damage, and amylose content of flours. In case of both rice varieties, the percentage of fine particles increased in the flours obtained from frozen rice. Freezing caused the increase of the flour yields from 45.5–50.9% to 54.6–56.5% and the decrease of the flour fineness modules. Moreover, the amylose content and starch damage registered changes when grinding frozen rice, but in case of those parameters, the values are influenced additionally by the native starch properties of variety and most probably by the texture of the endosperm. The swelling power, water solubility index, and gelatinization temperature were higher in flour from frozen rice compared to the flour from non-frozen rice. The modifications generated by rice freezing prior to grinding resulted in increased mechanical properties and decreased thermo-mechanical weakening of proteins. The hardness of the gel was directly correlated with the amylose content, while the freezing process led to the increase of the dough breakdown and starch retrogradation.

A case study on the observability of cutting fluid flow and the associated contact mechanics in scaled rough surfaces

In grinding processes, heat is generated by the contact of the grains with the workpiece. In order to reduce damages on the workpiece and the grinding tool, cutting fluids are necessary for most grinding processes. They have the tasks of cooling and lubricating the contact zone and to remove the chips from the contact area. Different types of cutting fluids perform differently regarding these tasks, which can be investigated on a laboratory scale. However, the results of those experiments are limited to certain workpieces and processes and information about the contact mechanics are not available. The experimental investigation of contact mechanics under cutting fluid influence is hardly possible. For this reason, this paper uses a measurement strategy that uses scaled topographies and has already been successfully applied to contact mechanics problems. With such a setup, it is intended that at an early stage in the development of cutting fluids, their characteristics in terms of contact mechanics can be determined very efficiently. To demonstrate this approach, two different cutting fluids were tested with the help of the associated test rig—a water miscible emulsion and a non-water miscible grinding oil. The two fluids showed fundamentally different characteristics regarding their hydrodynamic load bearing effect, their influence on the friction behavior of the contact and their fluid flow in the gap. The properties analyzed here correspond to the practical application of cutting fluids. The results underline the potential of the presented setup for an integration into the development process of cutting fluids.

Development of a Forward-Reverse Rotating cBN Electroplated End Mill Type Tool for Cutting and Grinding CFRP

Currently, the demand for carbon fiber reinforced plastic (CFRP) has increased in various fields. However, there have been few studies investigating the machined surface quality, degradation in CFRP mechanical properties with machining temperature, or machining tool cost. In particular, the machining temperature is considered to affect the machined quality because the CFRP matrix is a resin. In this study, a cubic boron nitride (cBN) electroplated end mill was developed; this novel tool can switch between cutting and grinding without needing to change the tool. To observe the relationship between the amount of abrasive grain in contact with the CFRP and the occurrence of burrs, a grinding test was conducted with different clearance angles of the end mill and different abrasive grain sizes. The temperature during the grinding processes was measured, and the burrs were estimated after the grinding processes. From these results, the contact amount of the abrasive grit suitable for grinding was derived.