Outer Arc Research Articles

Research Mechanism of Formation on Transverse Corner Cracks in the Continuous Casting Slab of Peritectic Steel

To figure out the formation mechanism of transverse corner cracks at the inner and outer arc of peritectic steel slab, the metallurgical microscope, scanning electron microscope with energy‐dispersive X‐ray spectroscopy, and electron probe‐X‐ray microanalysis, are used to study cracks. High‐temperature mechanical properties and the stress distribution of the outer arc of the bending section under different roll gap schemes are studied and simulated. The outer arc cracks expand along the grain boundary, while the inner arc cracks not only extend along the grain boundary but also traverse along the grains. The outer arc cracks are mainly generated at the bending section and are formed and expanded along the ferrite film. The inner arc cracks' cracking temperature is higher than the temperature of austenite transformation to ferrite. The third brittle temperature ranges are 650–850 °C, and the transverse corner crack sensitivity zone is 680–837 °C. The inner arc cracks are generated because of the element segregation and low temperature of the corner and then extended at the straightening section, and new cracks exist. The weakened cooling intensity and bending earlier at the bending section help to reduce the equivalent stress on the slab. The optimized experiments are conducted, and the transverse corner cracks are reduced significantly.

Seismic performance of braced frame structure with double-cylinder arc energy dissipator

A new type of braced frame structure with a double-cylinder arc energy dissipator is proposed in this paper. The energy dissipator is composed of an inner cylinder, an outer cylinder, and a stiffener fabricated and connected to a steel beam and column by welding, and the double cylinder arc energy dissipator is connected to a steel beam and steel column by welding. The seismic performance of the braced frame structure with a double-cylinder arc energy dissipator was analyzed by Abaqus. The results indicated that seismic energy could be dissipated through the deformation of the outer cylinder, inner cylinder, and rib plate. However, the double-cylinder arc energy dissipator could avoid the out-of-plane buckling deformation of the brace. Further, it exhibited properties similar to those of concentrically and eccentrically braced frames. The deformation of the braced frame with a double-cylinder arc energy dissipator mainly occurred on the dissipator and energy-dissipating beam (between the dissipator and column). During the loading process, the stiffener, outer and inner cylinders, and beam gradually yield. The height, thickness, and spacing of the stiffener of the double-cylinder arc energy dissipator were observed to significantly influence the seismic performance of the proposed braced frame. In contrast, the effect of the thicknesses of the inner and outer cylinder arcs on performance was negligible.

A novel arc plasma generating method by coaxial hybrid a ring arc to constraint arc: Principle and progress

Controlling of arc pressure in an arcing system is a critical and basic issue for welding application. A novel arcing torch is proposed to improve the controllability, a ring tungsten cathode is coaxial embedded into the water-cooling copper plasma arc nozzle. In the arcing process, the arc current flows into a single arc after it heats the anode and breaks into two branches to earth into the two separated cathodes: the center path works as the ordinary plasma arc and flows into the inner tungsten, the outer bypass free arc surrounds the center arc and flows into the ring tungsten. In this way, a coaxial hybrid arc forms based on a high-density plasma arc and a less-density ring free arc. Serial experiments were done to observe and measure the arc properties, including the arc column shape, arc pressure and anode state. It is observed that the outer arc can be fully absorbed into the inner arc to form a stable single hybrid arc. The hybrid arc properties are related to the two paths of arc current; the outer ring arc current has smaller pressure/current ratio than the central constraint plasma arc current. With such a version torch model, the employing current level of the ring arc is limited and lower than 40A to obtain stable hybrid arc. The results show the proposed arcing torch model is promising to control the output arc pressure with increased accuracy.

Performance investigation of a Savonius rotor by varying the blade arc angles

Wind energy is a promising source of renewable energy due to its availability. Savonius turbine is a vertical axis wind turbine that converts kinetic energy from the wind to mechanical energy. The current research investigates the performance of the conventional Savonius turbine by varying the position of the endpoints based on varying the blade arc angle. In addition, the outer blade arc angle of a modified configuration, which generated by varying the gap ratio, is also investigated. The ANSYS-Fluent package is used to perform the numerical simulation of the turbine to solve the equations of the unsteady Reynolds Averaged Navier–Stokes (RANS). The flow characteristics through the turbine are resolved by using the SST k-ω turbulence model. The numerical result of the conventional configuration is validated by using previous numerical and experimental research works. The current investigation proved that varying the outer and inner blade arc angles to 160° and 20° enhanced the maximum power coefficient by 4.5% and 12.9%, respectively. Furthermore, the maximum power coefficient of the modified Savonius rotor at a gap ratio of 0.1333 and an outer blade angle of 180° increased by 13.6% compared to the conventional profile.

An elastic organic single crystal with bending and high pressure-induced fluorochromism properties

The mechanically tunable flexible fluorochromic elastic organic single crystals are extremely rare. Fortunately, we prepared a needle-like elastic crystal (TPABA) with bending and high pressure-induced fluorochromism properties. With the reversible change of hydrostatic pressure, the crystal fluorescence underwent reversible red-shift and blue-shift (wavelength change greater than 100 nm). Interestingly, upon bending, the inner and outer arcs on the (002) and (200) surfaces of the crystal exhibited distinct fluorochromic effects by spatially resolved μ-PL measurements. Upon bending, the fluorescence emission of the inner and outer arcs on the (002) face of the crystal was red-shifted and blue-shifted by 26 nm and 4 nm, respectively. Different from (002) face, the inner arc and outer arc of the crystal (200) plane were only blue-shifted and red-shifted by 2 nm and 3 nm, respectively. Theoretical calculations indicated that, on the one hand, with the reversible bending of the crystal, the intermolecular interaction force distance in the crystal would change reversibly, and the corresponding inner and outer arc fluorescence emission wavelengths of the crystal plane would reversibly change. On the other hand, the number of π-π interactions on each face of the crystal had an important effect on the bending-induced fluorochromism of the crystal. This paper provided new idea for the preparation of the multi-faceted bending fluorochromism flexible crystals.

Effect of Bending Process on Microstructure, Mechanical Properties and Crack Formation of 5% Ni Steel

The 5% Ni steel is often used to make steel storage tanks to store liquefied natural gas (LNG). Herein, the microstructure and mechanical properties of 5% Ni steel samples during bending were studied through combining scanning electron microscopy, energy dispersive spectroscopy, optical microscopy, X-ray diffraction, and electron backscattered diffractometer methods with tensile tests. The outer and inner arcs underwent tensile and compressive stress, respectively, resulting in a severely deformed microstructure with a high density of dislocation, improving both the tensile and yield strengths. The ductility of the 5% Ni steel samples decreased significantly after bending due to the work hardening and dislocation accumulation. During bending, the shear bands occurred at the surface or subsurface, which were caused by strain localization. Amounts of “harder” grains with high TF and more orange and red KAM areas with high local strain at the outer and inner arcs produced a greater stress concentration than that of the mid-thickness, which can induce crack initiation and propagation due to the large deformation during bending.

Dual-Resonant Wideband Microstrip Annular Sector Patch Antenna With Increased Backfire Radiations

A novel design approach to wideband, dual-resonant microstrip annular sector patch antenna (MASPA) is proposed. As mathematically revealed by the dominant eigen-equation, MASPA with increased backfire radiation can be evolved from a truncated microstrip leaky-wave antenna. Then, the general relationships between the ratios of outer/inner radii, flared angles, and operational modes are deduced. The outer arc of the annular sector patch is set as a magnetic wall or open-circuited while the inner one is set as an electric wall or short-circuited, such that the patch’s size could be accordingly reduced by 13% to the circular sector case. As finally validated, a dual-resonant MASPA with a flared angle of 150°, outer/inner radii ratio of 3.0, and backfire gain up to 4.0 dBi can be implemented on single-layered air substrate with a height of 0.043-wavelength at the center frequency. Therefore, the advanced design approach can effectively realize patch miniaturization, wide band, and increased backfire radiation without inquiring extra multiple radiators and incorporating any additional reactance compensation techniques.

Tectonic Fabric in the Banda Arc‐Australian Continent Collisional Zone Imaged by Teleseismic Receiver Functions

AbstractThe convergent plate boundary in eastern Indonesia and Timor‐Leste captures an active oblique collision between the Banda Arc and the Australian plate. We analyzed ∼5 years' worth (2014–2019) of radial and tangential teleseismic Ps receiver functions (RFs) observed at 30 temporary broadband seismic stations across the area. Azimuthal variations in RF arrivals are observed throughout the region, indicative of the presence of oriented tectonic fabrics (dipping contrasts or plunging axis anisotropy) from a variety of crustal depths. The two main strikes of these fabrics are roughly parallel to the orogen and the plate convergence across the outer arc islands, likely associated with orogenic and strike‐slip structures. We observe distinct double polarity‐reversal arrivals with opposite polarity that reflect an anisotropic layer with orogen‐parallel strikes in the shallow crust beneath Timor and Savu, interpreted as metamorphic rocks. Fabrics oriented E‐W are imaged beneath the Flores and Lomblen that host active volcanoes, where we find interesting correlations with magmatic structures. NNW‐SSE striking fabric is imaged at ∼13 km depth beneath central Flores, which relates to a connected dike magmatic system that feeds the aligned cinder cones exposed on the surface. Finally, we identify convergence‐parallel fabrics on the volcano‐extinct islands of Alor and Atauro, consistent with one main fabric orientation imaged in Timor. We suggest all convergence‐parallel fabrics might accommodate strike‐slip motion generated by the overall NNE convergence of the Australian plate with respect to Eurasian plate and contribute to strain partitioning between the trough and backarc resulting from the collision.

Long-term Variability of Class I Methanol Masers in the High-mass Star-forming Region DR21(OH)

High-mass stars play an important role in the interstellar medium, but much remains to be known about their formation. Class I methanol masers may be unique tracers of an early stage of high-mass star formation, and a better understanding of such masers will allow them to be used as more effective probes of the high-mass star-forming process. We present an investigation of the long-term variability of Class I methanol masers at 44 GHz toward the high-mass star-forming region DR21(OH). We compare observations taken in 2017 to observations from 2012, and also to 2001 data from the literature. A total of 57 maser spots were found in the 2017 data, with center velocities ranging between −8.65 to +2.56 km s−1. The masers are arranged in a western and an eastern lobe with two arcs in each lobe that look like bow shocks, consistent with previous observations. The general trend is an increase in intensity from 2001 to 2012, and a decrease from 2012 to 2017. Variability appears to be more prevalent in the inner arc of the western lobe than in the outer arc. We speculate that this may be a consequence of episodic accretion, in which a later accretion event has resulted in ejection of material whose shock reached the inner arc at some point in time after 2001. We conclude that class I methanol masers are variable on long timescales (of the order of 5–10 yr).

Optimization of processing conditions in equal channel angular pressing for superior structure and properties

In the past 25 years, much interest has been paid to the production of ultrafine-grained (UFG) materials due to their superior structure and properties. Equal channel angular extrusion or pressing (ECAE or ECAP) is one of the severe plastic deformation (SPD) technique used to produce UFG materials. Compared to other SPD process, higher strain per pass and higher total productive strain after ‘n’ number of passes is possible in this technique. ECAP process is affected by various processing conditions or parameters. These processing conditions mainly affects the structure and properties produced through this technique. In this article, an effort has been made to provide the effect of each processing parameter on the structure and properties developed through this technique. Various processing conditions like- processing route, channel angle, outer arc of curvature, pressing speed, load and friction, processing temperature and application of back-pressure are critically discussed and effect of these parameters are summarized.

Distribution of Nonmetallic Inclusions in Slab for Tinplate

Tinplate is widely used in food packaging and chemical packaging. Industrial production continues to reduce the thickness of tinplate steel, which puts higher requirements on the control of inclusions. In this study, compared with traditional detection methods, the Ultrasonic Detection method can analyze the distribution of nonmetallic inclusions in larger size samples, which is closer to the actual production process. The numerical simulation model is established to analyze the flow, heat transfer and solidification behavior of molten steel. The results show: There are two nonmetallic inclusion bands in the sample at the edge of the slab, one is the inner and outer arc side of the sample, and the other is the 1/8 to 1/4 slab thickness region of the inner arc side in the sample. The inclusions in the thickness direction of the slab edge within the range of 1/8 to 1/4 are captured in areas 800 mm to 1400 mm below the meniscus. The solidification of the inner and outer arcs is not symmetrical, which leads to the asymmetrical distribution of inclusions in the inner and outer arcs. This study can provide a reference for improving the tinplate production process.

K-Ar DATING OF SELECTED IGNEOUS SAMPLES FROM THE SIBOLGA BASIN, MEULABOH AND SIMEULUE ISLAND, WESTERN SUMATRA

As part of a general study of the sedimentation, structure and tectonic evolution of the northern part of the Sumatranforearc basin samples of igneous rock were collected for K-Ar dating from the eastern margin of the Sibolga Basin, and from the outer arc island of Simeulue.

Changes in microstructure and mechanical properties during the bending process of NM450 wear-resistant steel

Bending deformation is a typical forming method in the manufacturing process of mechanical equipment. NM450 wear-resistant steel with high strength is vulnerable to bending failure, thus decreasing the bendability. The changes in microstructure and mechanical properties of NM450 wear-resistant steel during the bending process were studied by scanning electron microscopy, energy dispersive spectroscopy, optical microscopy, transmission electron microscopy, electron backscattered diffractometer methods, and tensile test. The inner and outer arcs around the bending axis underwent compressive stress and tensile stress, respectively, causing an obvious bending deformation of the martensite laths with a high dislocation density. The tensile strength around the inner- and outer-arc of samples exceeded that at the mid-thickness. During the bending process, the microsized TiN inclusions nearby the outer arc were subjected to tensile stress and multiple microcracks/cavities perpendicular to the outer arc were formed. However, the microsized TiN inclusions nearby the inner arc underwent compressive stress, initiating the occurrence of divergent microcracks.

Mechanism Design of a Transformable Crawling Robot and Feasibility Analysis for the Unstructured Environment

The better application of crawl robots depends on their ability to adapt to unstructured environments with significant variations in their structural shape and size. This paper presents the design and analysis of a novel robot with different locomotion configurations to move through varying environments. The leg of the robot, inspired by insects, was designed as a multi-link structure, including the Hoekens linkage and multiple parallel four-link mechanisms. The end trajectory was a symmetrical closed curve composed of an approximate straight line and a shell curve with a downward opening. The special trajectory allowed the robot to share drives and components to achieve structural deformation and locomotion. The structural characteristics of the crawl robot on the inner and outer arcs were obtained based on the working space. The constraint relationship between the structure size, the radius of the arc, and the coefficient of static friction with which the robot could crawl on the arc were established. The feasible support posture and support position of the robot under different arc radii were obtained. The simulation tested the locomotion of the robot on the plane, arc, and restricted space. The robot can be used for detection, search, and rescue missions in unstructured environments.

Effect of microstructure and texture on the mechanical properties in high strength pipeline bend

This paper focuses on the effect of microstructure and micro-texture on the mechanical properties in high strength pipeline bend. The transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD) were performed on the microstructure and texture observation. Tensile tests and Charpy V-notch impact tests were used to measure the strength and impact toughness, respectively. After hot induction bending, the microstructure of both the inner arc side and the neutral axis position has some polygonal ferrite (PF) grains. High-density dislocations, M/A constituents in the bainite laths, and high frequency of high Taylor factor in the outer arc side result in the toughness lower than the other specimens. In addition, dynamic recovery and partial recrystallization occurred during hot induction bending, the recrystallized grains are small and scattered distribution in the inner arc side and the outer arc side. The results indicated that the mechanical properties of the outer arc side have anisotropy along with the longitudinal and transversal directions. Micro-texture results obtained by EBSD measurement show that the main texture components in the experimental specimens are Cube, Goss, Brass, Copper, R-cube, and {331} <1–10> possibly because of the same mother pipe. However, the Brass and {112} <110>component might be the major factor of the anisotropy for the experimental bend.

Structured light-based dynamic 3D measurement system for cold-formed steel hollow sections

In the cold-formed steel hollow section manufacturing process, one of the key stages is forming an inspection to check whether it meets the requirement. In this paper, a dynamic 3D measurement system based on low-cost structured light was presented, which can be used to measure the dimensions of a cold-formed steel hollow section in real-time. The system is mainly composed of four sets line-structured light inspection device. A temporary coordinate is proposed to assist in solving multi the calibration of structured light plane. An optimisation method of L-M algorithm is proposed to solve the problem of stitching accuracy of point cloud contour. A point cloud simplification processing method is proposed for solving main parameters. The side length measurement error of the system is within ±0.05 mm, and the outer arc radius measurement error is within ±0.45 mm. All parallelisable tasks can achieve an acquisition rate of up to 25 fps.

Structural Reservoir Characterization of Akkas Gas Field, Western Iraq: Implications for Hydrocarbon Recovery

Akkas Field is a structural trap with a sandstone reservoir that contains proven gas condensate. The field is a faulted anticline that consists of the Ordovician Khabour Formation. The objective of this research is to use structural reservoir characterization for hydrocarbon recovery. The stratigraphic sequence of the Silurian and older strata was subjected to an uplift that developed a gentle NW-SE trending anticline. The uplifting and folding events developed micro-fractures represented by tension cracks. These microfractures, whether they are outer arc or release fractures, are parallel to the hinge line of the anticline and perpendicular to the bedding planes. The brittle sandstone layers of the reservoir are interbedded with ductile units of shale. The sandstone layers accommodate the formation of micro fractures that play a major role to increase the secondary porosity. The gas and condensate have been stored mainly through the micro fractures. Two types of drilling have been used for experimental gas production, vertical and horizontal. Horizontal drilling was parallel to both hinge line of the anticline and micro fracture surfaces that was conducted and doubled the gas production of the vertical well multiple times. However, if used the third type of drilling, directional, that is perpendicular to the hinge line and parallel to the beddings of both flanks of the anticline gas production will increase more than the horizontal drilling. The directional drilling will become perpendicular to the fracture surfaces and allow the gas and the condensate to flow into the well from all directions. Additionally, it will reduce the effect of both semi – liquid hydrocarbon condensate and vertical sediment barriers.

The Effects of Micro-vessel Curvature Induced Elongational Flows on Platelet Adhesion

The emerging profile of blood flow and the cross-sectional distribution of blood cells have far reaching biological consequences in various diseases and vital internal processes, such as platelet adhesion. The effects of several essential blood flow parameters, such as red blood cell free layer width, wall shear rate, and hematocrit on platelet adhesion were previously explored to great lengths in straight geometries. In the current work, the effects of channel curvature on cellular blood flow are investigated by simulating the accurate cellular movement and interaction of red blood cells and platelets in a half-arc channel for multiple wall shear rate and hematocrit values. The results show significant differences in the emerging shear rate values and distributions between the inner and outer arc of the channel curve, while the cell distributions remain predominantly uninfluenced. The simulation predictions are also compared to experimental platelet adhesion in a similar curved geometry. The inner side of the arc shows elevated platelet adhesion intensity at high wall shear rate, which correlates with increased shear rate and shear rate gradient sites in the simulation. Furthermore, since the platelet availability for binding seems uninfluenced by the curvature, these effects might influence the binding mechanics rather than the probability. The presence of elongational flows is detected in the simulations and the link to increased platelet adhesion is discussed in the experimental results.

Early Results of Eastern Indonesia P-wave Tomography Study Using Regional Events

The tectonic system of Eastern Indonesia is controlled by several major and minor plates, such as Indo-Australian, Australian plate, and Pacific plates. This area is known for its complexity, and high seismic activity. This study tries to image the complex structures beneath this region by employing regional events data and seismic tomography methods. We used five years of regional events catalog provided by the Indonesian Agency of Meteorology, Climatology, and Geophysics. We have sorted 7336 events recorded between 120° – 136° longitude and 0° – 13°(-) latitude consisting of 46446 P and 15467 S wave arrival data. Relocated hypocenter map shows a better constrain location on seismicity along outer Bandar Arc. A dipping pattern of seismicity is seen that is going deeper to the Banda Sea. The seismicity map also images a steep angle pattern of seismicity that could be related to the subduction slab roll-back model at North of Wetar island. Interestingly, we spotted a seismicity gap in West Seram that could be linked with slab tear zone. The checker-board test suggests a proper resolution is still reliable to a depth of 200 km with a less interpretable model at a depth of 300 km. P-wave tomographic models image the high velocity dipping down going slab. The Banda slab is seen to subduct from south Timor Island to the north, from east Tanimbar and Aru Island to west part, and from north Seram Island to south. We observed the down-going slab meet from all directions at about 300 km beneath the Banda sea. P wave tomogram also shows the Timor Island slab has a steeper dip that agrees with the seismicity pattern. Near the Seram island, we identify a low-velocity anomaly zone infiltrate the Banda slab beneath the shallow part of West Seram, which was previously interpreted as slab tear zone. This study also noticed a higher velocity tomogram model at North of Wetar island that might indicate a back-arc thrust. Lastly, a low-velocity band is also exposed at a shallow depth close to the volcano chain along that Banda volcanic arc.

Adakites and associated granitoids from the Serra da Prata Arc: Evidence for a Tonian subduction setting within the Araçuaí-Ribeira orogenic system (AROS), SE Brazil

Within deeply eroded orogenic belts, the geochemical signatures of metamorphosed igneous rocks can be used to constrain modern-like tectonic models operating in Precambrian times. One important aspect of this discussion is the presence or not of pre-collisional arc-related rocks that would represent the magmatic product of subduction processes imprinted on the upper plate of the convergent setting. New detailed geological and geochemical data of the northern segment of the Tonian to Cryogenian juvenile Outer Arc of the Araçuaí-Ribeira Orogenic System (AROS) are presented. Results were combined with recently published U–Pb and Hf data to contribute to a comprehensive tectonic model. The arc-related rocks (Serra da Prata Complex), transformed in foliated orthogneisses, are interlayered with dolomitic marbles, amphibolites, and psammo-pelitic paragneisses (Italva Group). This association is similar to the one described in the southern part of the orogenic system, pointing to the extension of the Outer Arc system until the Rio Doce River, in the transition zone between the Araçuaí and Ribeira segments of the AROS. New geochemical analyses together with reinterpreted published data indicate the presence of typical adakites that, together with normal calc-alkaline expanded series, island arc tholeiitic series, and A-type granitoids, corroborate with a modern style plate tectonic model. The envisaged model started in the Tonian, with E-verging subduction that resulted in the production of very juvenile arc-related rocks and associated fore-to back-arc basins filled with carbonatic rocks, meta-volcanic rocks, and MORB-like basaltic rocks. The typical adakites are considered the result of partial melting of young and hot oceanic lithosphere under moderate to high pressures in which garnet was an important stable residue. Potassic C-type adakitic rocks formed by the partial melting of thickened lower crust occur associated with the typical adakites. The occurrence of both adakites, together with A-type granitoids, characteristic of the investigated terminal sector of the Serra da Prata arc, is interpreted to result from a slab window gap, either associated with slab tearing/ridge subduction or slab roll-back, hampering an intracontinental model for the Ribeira orogen.