Anmeldelser, bekendtgjort i Statstidende i februar måned.

Anmeldelser, bekendtgjort i Statstidende i februar måned

The Weser Estuary : a study on heavy metal behaviour under hydrographic and water quality conditions

In continuation of fixed anchor stations the behaviour of heavy metals was also studied in longitudinal sections in the bottom sediments (Calmano et al. 1982) and in the water (this paper). There are changes in concentrations of dissolved metals in water and changes in contents of metals in seston (suspended matter) in dependence on tides (Duinker et al. 1982 b). These changes can be related to the passing of different water bodies and different seston types, respectively, at the place of observation. In addtition, more changes were found at various hydrographically defined "stretches" along the whole length of the estuary. These changes were attributed to dilution of estuarine water by coastal seawater in the lower estuary; but in the mud reach in the central estuary they were attributed to the interchange with mud (alternating settling and resuspension of loose sediment particles through tides). In the central and the upper estuary they could be attributed to the influence of very low salinity, to the predominance of either organic matter or clay or quartz in seston, to the state of aggregation of seston particles which depends on salinity, the nearness to the mud reach and perhaps the amount of the particles in water; and the changes could further be attributed to emissions from industrial sites, sewage outfalls and the dumping of dredge spoil. Relation to organic water quality criteria were not found. The bioavailability of particulate metals is discussed: it is comparatively high in Cd, Zn and Mn (80-95%) and lower in other elements

Dredging of contaminated sediments in the Weser Estuary : chemical forms of some heavy metals

Concentration and chemical forms of metals in bottom sediments and dredged mud of the Weser Estuary were studied. The sediments with the highest metal contents are found in the harbour basins of Bremen and in the mud shoal near Nordenham. Association types of the metals can be divided into 2 groups: metals with relatively high potential of mobilization, such as Cd, Zn, Mn, and Ni and those that are strongly bound on particles - Cr, Cu, Pb and Fe. An estimation of the bioavailability of these metals based on chemical extraction studies is relevant to problems encountered during disposal of dredged materials

Prevention of over-dimensioning in light-weight structures by control of uncertainties during production

A load adapted dimensioning of constructive parts is aspired in order to achieve the goal of lightweight-design motivated material reduction. To prevent oversizing, uncertainties in product properties, like geometry and strength, which are caused by fluctuating properties of semi-finished parts, must be controlled 1. Narrow tolerances in semi-finished part specification lead to an increase in costs and testing effort. The alternative approach is to control uncertainties by a feedback or adaptive control system. Therefore, several flexible and adaptive forming processes are designed and evaluated. As an example, a bending process for the flexible production of a heat dissipater shows, that geometric properties like the bending angle can be achieved reproducibly, despite material and sheet-thickness related spring-back. The process is conducted on the 3D Servo Press, a novel servo press with 3 degrees of freedom of the ram. It consists of an implemented material and sheet thickness detection and thus can adapt to actual semi-finished part properties 2. This approach is to be transferred to forging processes in the future. By using the three degrees of freedom of the 3D Servo Press, the potential to influence incremental processes, like rotary forging of thick-walled tubes or billets, is under evaluation

Mit Industrie 4.0 wenig zu tun?

Prozesssteuerung und -überwachung ist Inline-Sache, die Simulation von Umformabläufen eher Offline-Angelegenheit. Noch gehören die beiden Welten nicht zwingend zusammen. Aber es gibt Gemeinsamkeiten, die sich verbinden und ausbauen ließen. Oder anders gesagt: Industrie 4.0 kommt auf Dauer kaum um den Kurzschluss herum

Evaluation of control strategies in forming processes

Products of forming processes are subject to quality fluctuations due to uncertainty in semi-finished part properties as well as process conditions and environment. An approach to cope with these uncertainties is the implementation of a closed-loop control taking into account the actual product properties measured by sensors or estimated by a mathematical process model. Both methods of uncertainty control trade off with a financial effort. In case of sensor integration the effort is the cost of the sensor including signal processing as well as the design and manufacturing effort for integration. In case of an estimation model the effort is mainly determined by the time and knowledge needed to derive the model, identify the parameters and implement the model into the PLC. The risk of mismatch between model and reality as well as the risk of wrong parameter identification can be assumed as additional uncertainty (model uncertainty). This paper evaluates controlled and additional uncertainty by taking into account process boundary conditions like the degree of fluctuations in semi-finished part properties. The proposed evaluation is demonstrated by the analysis of exemplary processes