Internal structure and paleoecology of the lower Permian Uzunbulak reef complex of the Tarim Basin, Northwest China

The internal construction and biotic communities of the Uzunbulak reef of the northwestern Tarim Basin are studied for the first time. The reef was built during the Sakmarian, while the reef substrate and capping beds are of latest Asselian and earliest Artinskian ages, respectively. The reef substrate beds are composed of skeletal and oncoid grainstone. Those fusulinid-dominated skeletal shoals and oncoid banks indicate a high-energy environment and produced local topographic highs on which the reef grew. Reef framework consists mainly of calcisponge bafflestone, calcisponge-Thartharella framestone, and Tubiphytes, Archaeolithoporella and Girvanella boundstones. Calcisponges were the primary frameconstructors that baffled high-energy currents. Archaeolithoporella, Tubiphytes, Girvanella and possibly microbes acted as the primary binders for the boundstone framework. Fusulinids and brachiopods were common reef dwellers. The interreef facies sediments are composed of skeletal-crinoid wackestone-packstone. Most of bioclasts have thick, micritized envelopes. The back-reef facies deposits consist of alternating skeletal packstone to wackestone and black shale. Sea-level fluctuations were probably accountable for the reef growth and demise.

Of the reefal dwellers, brachiopods are extraordinarily abundant in Uzunbulak. They are assignable to five distinctive associations, one each from the reef substrate, framework and inter-reef facies, respectively, and two from the reef capping facies. The brachiopods in the substrate beds were mostly attached to hard substrates by a pedicle, while a few species rested on soft substrates by support of halteroid spines. Cementation of the ventral valve on hard substrates characterizes attachment of the reef framework brachiopods. All inter-reef species were anchored into the substratum comprising hard material by a strong pedicle. Back-reef brachiopods dominantly rested on the soft substrates by support of halteroid spines. the framework brachiopods had the strongest wave-resistant capability;those from both substrate and inter-reef facies were moderately capable of withstanding agitation; and the backreef species preferred to live in calmwater, organic-rich muddy environments.

Functional morphology of the gastric mills of carnivorous, omnivorous, and herbivorous land crabs

Terrestrial decapods consume a wide variety of plant and animal material. The potential adaptations of carnivorous, omnivorous, and herbivorous terrestrial crustaceans were studied by examining the functional morphology of the gastric mill. Two closely related species from each feeding preference group were examined to identify which features of the mill were due to phylogeny and which were due to adaptation. The morphology of the gastric mill matched the diet well; the gastric mills of the carnivorous species (Geograpsus grayi and Geograpsus crinipes) possessed a blunt, rounded medial tooth and flattened lateral teeth with a longitudinal grinding groove. These features make them well suited to a carnivorous diet of soft animal tissue as well as hard material, such as arthropod exoskeleton. In contrast, the mill of the herbivorous gecarcinids (Gecarcoidea natalis and Discoplax hirtipes) consisted of a medial tooth with sharp transverse ridges and lateral teeth with sharp interlocking cusps and ridges and no grinding surface. These features would efficiently shred fibrous plant material. The morphology of the mill of the omnivorous coenobitids (Coenobita perlatus and Birgus latro) was more generalized toward a mixed diet. However, the mill of B. latro was more adapted to deal with highly nutritious food items, such as nuts and heavily calcified decapods. Its mill possessed lateral teeth with extended ridges, which sat close to the calcified cardiopyloric valve to form a flattened floor. Hard items trapped in the mill would be crushed against this surface by the medial tooth.

Machinability assessment and surface integrity characteristics of Austempered Ductile Iron (ADI) using ultra-hard cutting tools

The application of austempered ductile iron (ADI) is gaining an ever greater share of the worldwide ferrous product market, specifically centering on the aerospace, automotive and shipping industries. ADI is a heat treated cast iron, which exhibits remarkable mechanical properties and provides an attractive material for designers and engineers to displace conventional materials. Previous attempts, however, to machine ADI using carbide or ceramic cutting tools produced poor tool life characteristics due to the relatively poor machinability of the workpiece. This paper presents a research study that has applied the advanced technology of modern ultrahard cutting tools, in an attempt to achieve enhanced machinability performance. This performance was evaluated through the analysis of cutting forces, tool wear, surface finish and roundness.

Advances in tailored hot stamping – innovations in material and local patchwork topology

Hot stamping is now commonplace in the automotive industry. The continuing need by automotive manufacturers to reduce weight while increasing crashworthiness has driven the industry to seek new hot stamping solutions. Tailored hot stamping can be thought to produce a part that has patchwork of hard and soft regions. In this context, patchwork means that there is a relational organization (topology) to the network of hard and soft regions. The next generation of tailored hot stamping will therefore combine new steel grades together into a single part, and secondly will be able to locally tailor material properties to meet detailed engineering targets. The key to meeting engineering demands will be how the patchwork material properties are organized on the part. This paper will briefly outline our latest research in tailoring parts.