Analysis of microstructure effects on edge crack of thin strip during cold rolling

Edge cracks in cold rolling of the thin strip affect the strip quality and productivity significantly. In this study, an experimental and mechanical investigation on microstructures has been carried out to study the edge crack formation during cold rolling of the thin strip. The effects of the feed material microstructures on the edge crack evolution were studied employing optical microscopy and scanning electron microscopy (SEM). Experimental observation indicates that fine grain occurs in hot-rolled microstructure and coarse grain is produced in ferritic rolled microstructure. Different grain sizes affect significantly the formation mechanics of the microcrack, crack initiation, and orientation of crack extension. The grain size and grain boundaries effects on crack retardation are discussed also during edge crack initiation. During the crack growth in coarse grain, most edge crack tips will blunt, which improves the crack toughness by causing less stress concentration. Overall, the fine microstructure shows a good crack initiation resistance, whereas the coarse microstructure has a better resistance to crack propagation. This research provides additional understanding of the mechanism of microstructure influence on edge crack evolution of cold strip rolling, which could be helpful for developing defect-free thin strip

Dynamic electron correlations with charge order wavelength along all directions in the copper oxide plane

In strongly correlated systems the strength of Coulomb interactions between electrons, relative to their kinetic energy, plays a central role in determining their emergent quantum mechanical phases. We perform resonant x-ray scattering on Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, a prototypical cuprate superconductor, to probe electronic correlations within the CuO$_2$ plane. We discover a dynamic quasi-circular pattern in the $x$-$y$ scattering plane with a radius that matches the wave vector magnitude of the well-known static charge order. Along with doping- and temperature-dependent measurements, our experiments reveal a picture of charge order competing with superconductivity where short-range domains along $x$ and $y$ can dynamically rotate into any other in-plane direction. This quasi-circular spectrum, a hallmark of Brazovskii-type fluctuations, has immediate consequences to our understanding of rotational and translational symmetry breaking in the cuprates. We discuss how the combination of short- and long-range Coulomb interactions results in an effective non-monotonic potential that may determine the quasi-circular pattern.Comment: This is a post-peer-review, pre-copyedit version of an article published in Nature Communications. The final authenticated version is available online at: https://doi.org/10.1038/s41467-020-20824-7. Supplementary materials are available through the published version in Nature Communication

First Sagittarius A* event horizon telescope results. II. EHT and multiwavelength observations, data processing, and calibration

Instrumentatio

Biomechanical Research on Plantar Pressure Distribution in Different Landing Condition

With the increase of the difficulty and intensity on competitive movement, the rate of sport injury will happen in training and competing frequently. The metatarsal is one of the most prone to injury part in the human body. The incidence of metatarsal injuries is rising in recently years. In this study, Pedar-X plantar pressure measure system and Novel emed pressure distribution measure plate were used in order to get the dynamics data in normal landing and inverted landing. The research concluded that: metatarsal peak stress had been transferred from the first metatarsal to the fifth metatarsal with increasing of varus angle. When the foot was in inverted state, stress distribution of metatarsal changed significantly. Lateral metatarsal played a major role in supporting function. Also, forefoot pressure distribution changed a lot in different functional sports shoes. The purpose is to provide the reliable correlative theoretical basis for improving sport equipments and security protection recommendations for people to engage in sports.</jats:p