Design of multi-step dies for sheet metal forming using a workpiece-performance-based approach: A preliminary study

Deep-drawn components are predominantly manufactured using multistep operations, e.g., in a progressive or transfer dies. Currently, intermediate die design is geometry-based and often neglects the influence of workpiece plastic flow during forming on the final part's mechanical performance. This approach results in non-homogeneous material deformation, inefficient material utilisation, wrinkling defects, and an increased risk of service failures. This study proposes an alternative workpiece-performance-based die-design approach for deep drawing, emphasising the critical role of material flow in determining the component's geometrical accuracy and mechanical properties. The strategy was experimentally tested on S420MC steel (1.8 mm thickness) square cups using two-step process chains: (1) a conventional method where the blank was partially drawn into a square cup, followed by full drawing, and (2) an alternative method starting with a circular blank partially drawn into a circular cup before full drawing to the square shape. Numerical analysis in AutoForm evaluates the evolution of effective plastic strain throughout the steps. The results demonstrate significant improvements, including more uniform strain distribution, a 7% wall thinning reduction, elimination of ironed wrinkles, and components with threefold increased strength and enhanced ductility. These findings highlight the potential of performance-based die design to improve material efficiency and structural reliability

First Appearance Datums (FADs) of selected acritarch taxa and correlation between Lower and Middle Ordovician stages

First Appearance Datums (FADs) of selected, easily recognizable acritarch morphotypes are assessed to determine their potential contribution to correlation between Lower and Middle Ordovician stages and substage divisions along the Gondwanan margin (Perigondwana) and between Perigondwana and other palaeocontinents. The FADs for 19 genera, species and species groups are recorded throughout their biogeographical ranges. The taxa investigated fall into three groups. Some have FADs at about the same level throughout their biogeographical ranges and are useful for long‐distance and intercontinental correlation. Among these are Coryphidium, Dactylofusa velifera, Peteinosphaeridium and Rhopaliophora in the upper Tremadocian Stage; Arbusculidium filamentosum, Aureotesta clathrata simplex and Coryphidium bohemicum in the lower–middle Floian Stage; Dicrodiacrodium in the upper Floian Stage; Frankea in the Dapingian–lower Darriwilian stages; and Orthosphaeridium spp., with FADs in the Dapingian–lower Darriwilian stages of Perigondwanan regions and at about the same level in Baltica. Other taxa, however, have diachronous (or apparently diachronous) FADs, and this needs to be taken into account when using them for correlation. A second group of genera and species, comprising Striatotheca, the Veryhachium lairdii group and the V. trispinosum group, have a recurring pattern of FADs in the Tremadocian Stage on Avalonia and in South Gondwana and West Gondwana, but in the Floian Stage of South China and East Gondwana. The third group, consisting of Arkonia, Ampullula, Barakella, Dasydorus, Liliosphaeridium and Sacculidium, have FADs that are markedly diachronous throughout their biogeographical ranges, although the global FADs of Arkonia, Ampullula, Liliosphaeridium and Sacculidium are apparently in South China and/or East Gondwana. It is possible that diachronous FADs are only apparent and an artefact of sampling. Nevertheless, an alternative interpretation, suggested by recurring patterns, is that some as yet undetermined factor controlled a slower biogeographical spread over time, resulting in diachroneity

Biogeography of early to mid Palaeozoic (Cambrian-Devonian) marine phytoplankton

Early to mid Palaeozoic marine phytoplankton are represented by acritarchs and associated forms, which had a global distribution from the early Cambrian to the early Carboniferous (Mississippian). Palaeozoic phytoplankton assemblages show varying degrees of cosmopolitanism and endemism through time. A high degree of cosmopolitanism was evidently characteristic of the Cambrian and much of the Late Ordovician, Silurian and Devonian, but provincialism was more marked in the Early Ordovician and Hirnantian (latest Ordovician), the latter at a time of major palaeoenvironmental perturbations. Distribution patterns of Palaeozoic phytoplankton are attributed to a number of interacting factors, including palaeolatitude, palaeotemperature, oceanic circulation patterns, the disposition of continents, differentiation between oceanic and cratonic (distal–proximal) assemblages, and sedimentary environments and facies. There are indications that biogeographical ranges of taxa shift over time. Moving our understanding of Palaeozoic phytoplankton biogeography forward requires (1) targeted investigation of regions and time periods for which no or little data exist, (2) quantitative analysis of data to investigate how similarity between regions varies through time and how this might correlate with other datasets such as carbon isotope stratigraphy or sea-level, and (3) rigorous application of well-defined time slices to compare coeval assemblages, at least within the limits of resolution

Reprint of ‘Eighty years of chitinozoan research: From Alfred Eisenack to Florentin Paris’

In the early 1930s Alfred Eisenack first reported unknown, bottle-shaped, organic-walled microfossils that he had discovered in erratic boulders from the south-eastern shores of the Baltic Sea. Eisenack erected the new group Chitinozoa to classify these strange microfossils of unknown biological affinity. From the 1930s to the 1950s, a few publications appeared reporting new findings and providing descriptions of these fossil organisms. It was only since the 1960s, with the development of the oil industry and the intensive biostratigraphical use of organic-walled microfossils, that publications dealing with chitinozoans became more numerous and that the description of new genera and species rapidly increased. The peak of description of new species was reached in the 1960s, but the number of publications remained high into the late 1990s. Since the 1990s the research activities on chitinozoans are conducted by a much smaller number of scientists. One of the major driving forces of chitinozoan research in the last forty years was Florentin Paris at the University of Rennes (Brittany, France). He first established a high-resolution chitinozoan biostratigraphy of the Ordovician of southern Europe and played an active role in bringing all scientists together for the development of global biostratigraphical schemes and palaeobiogeographical scenarios of the Ordovician, Silurian and Devonian. It was also Florentin Paris, together with his Estonian colleague Jaak Nõlvak, who suggested the now widely accepted biological interpretation that Chitinozoa are most probably egg cases of a planktonic organism unknown from the fossil record. F. Paris was also the first to collaborate w ith experts to use biogeochemical analyses and the C isotope signal of the chitinozoans to better understand their biological affinity and detect biogeochemical changes in Palaeozoic oceans