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Copyright of Journal of Northeastern University (Natural Science) is the property of Dongbei Daxue Xuebao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With increasingly severe environmental problems, energy saving and environmental protection have become two important issues to be solved in the automobile industry. Patchwork blank hot-stamping technology can be used to obtain light-weight and high-strength parts and is thus increasingly used in the manufacture of autobody parts. Because the main blank and the patched blank need to be connected through spot welding before forming, the welding spots' arrangement has a great influence on the formability of the part. In this study, a thermal–mechanical coupling finite element analysis model of A-pillar patchwork blanks was established. With the thickness of the patched blank, the distance between the welding spot and the external contour of the patched blank, and the number of welding spots as optimization variables, together with the maximum thinning rate and the maximum welding spot force as objectives, the influence of welding spot arrangement on forming quality was analyzed, and the welding spots' arrangement was optimized using a central composite design (CCD), the response surface method (RSM), and the genetic algorithm (GA). The results showed that when the initial welding spot was located close to the contour of the patched blank, the bending moment was greater when the weld spot passed through the die corner, leading to the rupture of the welding spot or its surrounding base material due to the greater thinning rate. When the patched blank was thicker than the main blank, the main blank cracked during the forming process due to a greater increase in the thinning rate. The optimal solution of the weld spot arrangement on the A-pillar patchwork blanks was a 1.2 mm thick main blank, 0.8 mm thick patched blank, a distance of 29 mm between the weld spot and the contour line of the patched blank, and 16 weld spots. Hot-stamping experiments were conducted using the optimized weld spots' arrangement, and high-quality parts were obtained. [ABSTRACT FROM AUTHOR]

In this work, thermal deep drawing and thermoelectric coupling drawing tests were performed on an annealed ZK60 magnesium alloy sheet to investigate the effect of the pulse current on the formability of the ZK60 magnesium alloy during the drawing process. The effects of thermal deep drawing and the thermoelectric coupling on the forming of drawn parts were studied, and the changes of the thinning rate and hardness were obtained. The results showed that the using of pulse current improved the formability of the ZK60 magnesium alloy and increased the ultimate depth of drawing. The hardness value of the drawn part showed an overall increasing trend, followed by thermoelectric coupling deep drawing, which was significantly higher than the sheet after annealing without deep drawing. The deep-drawn parts had different grain sizes in different places, and dynamic recrystallization occurred to varying degrees in each region. Furthermore, the degree of dynamic recrystallization in the punch fillet and cylinder wall was significantly higher than in other areas. [ABSTRACT FROM AUTHOR]

In this paper, the flexible support mould is designed by using magnetorheological elastomer (MRE) to assist in the deep-drawing of magnesium alloys. Based on the magnesium alloy mechanical tensile test and magnetorheological elastomer regular force experiments, the deep-drawing process of AZ31 magnesium alloy supported by support mould was numerically simulated by finite-element analysis software ABAQUS. By varying the current input to the excitation coil to change the magnetic induction intensity and thus adjust the magnetic normal force of the magnetorheological elastomer, then using magnetic normal force to complete the auxiliary sheet metal deep-drawing. The results show that, compared with the unsupported mould, the supported mould can effectively reduce the maximum thinning rate of magnesium alloy on the original basis, thus effectively increasing the ultimate depth of magnesium alloy deep-drawing. It can replace the original buffer device, effectively solution the problem of pulling and cracking at the bottom of magnesium alloy caused by the original excessive damping force, and improve the yield rate of workpiece. [ABSTRACT FROM AUTHOR]

The design of pressure hull structures plays an essential role in the research and development of underwater operation equipment such as deep-sea submersibles. As a bionic structure, an egg-shaped shell has apparent advantages in the application of an underwater pressure hull. Still, the egg-shaped shell is a positive Gauss surface, so it is difficult to control the manufacturing accuracy and quality. In this paper, the technology of solid particle flexible medium forming and the principle of high-pressure bulging in tubes is proposed to manufacture high-precision egg-shaped shell parts. By optimizing the shape of the punch structure, optimizing the process parameters, improving the stress and strain distribution of the egg-shaped shell, and analyzing the deformation mechanism in the bulging process, we have mastered the deformation and quality control methods of the granular medium flexible bulging of non-equal curvature tubular structures in some aspects. [ABSTRACT FROM AUTHOR]

A Skeleton that is extracted by a skeletonization algorithm from a binary image is useful for object description, matching, recognition and compression. The parallel thinning algorithm, one of the skeletonization algorithms is well known to have computational effciency. The main contribution of this paper is that we proposed a novel fully parallel thinning algorithm based on a comprehensive investigation of the well-known Zhang-Suen (ZS)-series algorithms and the one-pass thinning algorithm (OPTA)-series algorithms, which not only has good performance in terms of (8,4) connectivity preservation and single-pixel thickness, but also has the following qualities: it is more robust to the boundary noise than the OPTA-series algorithms and it is faster than the ZS-series algorithms in terms of thinning speed, as confirmed by the experiments presented in this paper. [ABSTRACT FROM AUTHOR]

To understand the timing of deglaciation of the northernmost marine-terminating glaciers of the Cordilleran Ice Sheet (CIS), we obtained 26 10Be surface-exposure ages from glacially scoured bedrock surfaces in Prince William Sound (PWS), Alaska. We sampled six elevation transects between sea level and 620 m and spanning a distance of 14 to 70 km along ice flow paths. Most transect age–elevation patterns could not be explained by a simple model of thinning ice; the patterns provide evidence for lingering ice cover and possible inheritance. A reliable set of 20 ages ranges between 17.4 ± 2.0 and 11.6 ± 2.8 ka and indicates ice receded from northwestern PWS around 14.3 ± 1.6 ka, thinned at a rate of ~120–160 m/ka, and retreated from sea-level sites at 12.9 ± 1.1 ka at a rate of 20 m/yr. The retreat rate likely slowed as glaciers retreated into northern PWS. These results are consistent with the growing body of reported deglacial constraints on collapse of ice sheets along the Alaska margin indicating collapse of the CIS soon after 17 ka. These data are consistent with paleotemperature data indicating that a warming North Pacific Ocean caused catastrophic collapse of this part of the CIS. [ABSTRACT FROM AUTHOR]

In this paper, the subject of research is the AZ31B magnesium alloy. Aiming at the poor formability of magnesium alloys at room temperature, we have introduced isothermal local loading technology to improve the formability of magnesium alloys. We combined finite element simulations and experiments to study the effects of forming parameters on the forming limit angle and thinning rate of single-point incremental forming under isothermal local loading. The conclusions were further validated by changes in grain size in micrographs. The results showed that the forming limit angle of the AZ31B magnesium alloy sheet increased as the forming temperature increased. Maximum thinning first decreased and then increased, reaching the lowest point at 250 °C. At 250 °C, the grain size is large and evenly distributed, which is the best forming temperature. The radius of the tool head increases, the forming limit angle increases, the maximum thinning rate decreases, and the overall change of the average grain size is relatively small. However, the grain size is more uniform when the radius is 5 mm, and 5 mm is the best tool radius. The feed rate is inversely proportional to the forming limit angle and directly proportional to the maximum thinning rate. Different feed rates have different degrees of compression and elongation of the grains. The forming quality is better when the feed rate is 2 mm. The initial plate thickness is proportional to the limit angle, the maximum thinning rate, and grain size. And 1 mm is the best plate thickness to ensure the forming quality. This paper is important for developing the forming theory of isothermal local loading that can improve the high-performance forming of alloy parts in advanced manufacturing. [ABSTRACT FROM AUTHOR]

Over the last several years, numerous outcrop localities have been revisited to add quantitative detail to submarine lobe facies models that previously focussed on facies relationships in a qualitative sense. This study utilises well‐exposed submarine lobe deposits of the Point Loma Formation in Cabrillo National Monument (San Diego, CA) to provide quantitative and statistical insights into the lateral variability of event‐bed (i.e. turbidite) architecture within and between lobe elements. Within a lobe element (defined as a surface‐bounded, genetically related package), event beds compensationally stack, thinning over subtle sea floor topography created by the previous event bed. Between lobe elements, larger‐scale compensation is observed, with clearly defined stratal surfaces and facies architecture distinguishing the four lobe elements. A lateral facies transition is observed for one lobe element, where sandstone beds pinch out and the element thickness halves over a distance of 100 m. However, architectural parameters of event beds (e.g. bed thickness, thinning rate, fining rate) are not appreciably different between these elements, suggesting that the observed stratal architecture does not readily translate into vertical bed thickness (i.e. stacking) patterns that could be easily recognised in common subsurface data types like borehole‐derived core. While the data derived from this outcrop study are valuable for improving the construction of realistic geological and reservoir models, caution is necessary when interpreting lobe element boundaries from borehole data. The lobe deposits measured in this study have event‐bed thicknesses and thinning rates most similar to semi‐confined proximal lobes, suggesting a more proximal position and more confined than previously interpreted. Based on the relationships between sandstone and mudstone thicknesses and thinning rates, bed and lobe‐element compensation and minimal evidence of erosion, the Point Loma Formation at Cabrillo National Monument is reinterpreted as a medial lobe environment with some degree of lateral and/or frontal confinement. [ABSTRACT FROM AUTHOR]

Point clouds have ability to express the spatial entities, however, the point clouds redundancy always involves some uncertainties in computer recognition and model construction. Therefore, point clouds thinning is an indispensable step in point clouds model reconstruction and other applications. To overcome the shortcomings of complex classification index and long time consuming in existing point clouds thinning algorithms, this paper proposes a point clouds fast thinning algorithm. Specifically, the two-dimensional index is established in plane linear array (x, y) for the scanned point clouds, and the thresholds of adjacent point distance difference and height difference are employed to further delete or retain the selected sample point. Sequentially, the index of sample point is traversed forwardly and backwardly until the process of point clouds thinning is completed. The results suggest that the proposed new algorithm can be applied to different targets when the thresholds are built in advance. Besides, the new method also performs superiority in time consuming, modelling accuracy and feature retention by comparing with octree thinning algorithm. [ABSTRACT FROM AUTHOR]

To address the instability phenomenon caused by the continuous increase in the drum height during the long-distance spinning of ultra-thin cylindrical parts, the evolution and influencing factors of the drum height during the spinning process are studied by combining both theory and experiment. The parameters that can be used to restrain the increase in the drum height are obtained and successfully applied to the long-distance thinning spinning process of ultra-thin cylindrical parts. First, combined with the spinning model, the constraint boundary, metal flow and stress field of the spinning contact zone are analysed, and the formation mechanism and influence parameters of the drum shape during the spinning of the thin-walled cylinder are obtained. Next, by performing a numerical simulation, the influence law of the parameters (thinning rate and feed rate) on the height of the drum is obtained, and an experimental verification is performed. Based on the change rate of the drum height as the selection basis of the parameter interval, the method of reducing the thinning rate of each pass and increasing the spinning pass is selected to suppress the continuous increase in the drum height during the long-distance spinning of thin-walled cylinders. Finally, through the fine-tuning of the parameters, the long-range stability spinning of a thin-walled cylinder with a diameter of φ398 mm is realized (the wall thickness is reduced from 2 to 0.53 mm, and the spinning length is extended from 1030 to 3800 mm). The results show that the thinning rate is the main parameter affecting the change in the drum height when the parameters of the machine tool, mandrel, workpiece and rotating wheel are fixed. The spinning pass and reduction in each pass can be determined with the thinning rate not exceeding 45%, which can effectively control the increase rate of the drum height and prevent the instability phenomenon caused by the continuous increase in the drum height during the long-range spinning of the ultra-thin cylindrical parts. The findings provide theoretical and experimental guidance for the long-distance stability spinning of ultra-thin cylindrical parts. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thinning is one of the most important techniques in the field of image processing. It is applied to erode the image of an object layer-by-layer until a skeleton is left. Several thinning algorithms allowing to get a skeleton of a binary image are already proposed in the literature. This paper investigates several well-known parallel thinning algorithms and proposes a modified version of the most widely used thinning algorithm, called the ZS algorithm. The proposed modified ZS (MZS) algorithm is implemented and compared against seven existing algorithms. Experimental results and performances evaluation, using different image databases, confirm the proposed MZS algorithm improvement over the seven examined algorithms both in terms of the obtained results quality and the computational speed. Moreover, for an efficient implementation (on Graphics Processing Units), a parallel model of the MZS algorithm is proposed (using the Compute Unified Device Architecture, CUDA, as a parallel programming model). Evaluation results have shown that the parallel version of the proposed algorithm is, on average, more than 21 times faster than the traditional CPU sequential version. [ABSTRACT FROM AUTHOR]

Multi-point flexible stretch forming (MPFSF) is a sheet metal forming technology with highly flexible characteristics based on the die and the clamping method. The multi-point die (MPD) surface is composed of many discrete fixed units in MPFSF, and the dimple and stretching ditch will be generated on the formed part surface. Swinging unit multi-point die with discrete elastic cushion can suppress the dimple and stretching ditch, reduce working intensity of elastic cushion removal as well as simplify the process. Two MPFSF finite element numerical models are established for fixed unit with integral elastic cushion (FUIEC) and swinging unit with discrete elastic cushion (SUDEC), respectively. Through detailed numerical simulations and conducting the flexible stretch forming experiments, the results are compared between the two parts formed by FUIEC and SUDEC. According to the results, it is demonstrated that the stress, strain, and thickness distributions are more uniform when forming by SUDEC. Moreover, the stress, strain, and thickness thinning rate values are smaller. In addition, the surface forming quality is improved and the shape accuracy is higher by SUDEC. Therefore, SUDEC can replace FUIEC in a certain extent, and the production efficiency is increased accordingly. [ABSTRACT FROM AUTHOR]

Multi-point stretch forming (MPSF), by replacing the traditional rigid fixed-shape stretching die with the multi-point die (MPD), is an important flexible forming technique in sheet metal forming process. However, the particular dimples will be generated on the formed part surface when forming by MPD. In this paper, we prove that the dimple formation can be suppressed by changing the punch units of MPD arrangement. Therefore, the forming effect can be largely improved. Spherical parts are selected as the study objects. Under the same loading condition, two MPSF finite element numerical models are established for conventional arrangement multi-point die (CAMPD) and staggered arrangement multi-point die (SAMPD), respectively. Through the numerical simulations and the stretch forming experiments, the stress, strain, thickness, springback, and shape accuracy are compared between the two parts formed by CAMPD and SAMPD. The results show that the values of the stress, strain, thickness thinning rate, and springback of the formed part are smaller when forming by SAMPD. Moreover, the distributions of the stress, strain, and thickness are more uniform. Also, the surface forming quality and the shape accuracy are improved. These results provide a valuable guidance during developing the new types of MPD. [ABSTRACT FROM AUTHOR]

Deposits from episode 1 of the 1969-1974 Mauna Ulu eruption of Kīlauea provide an exceptional opportunity to study processes of low intensity Hawaiian fissure fountains. Episode 1 lava flows passed through dense forest that had little impact on flow dynamics; in contrast, the pattern of spatter preservation was strongly influenced by the forest (through the formation of tree molds) and the preexisting topography. A low, near-continuous spatter rampart is present upwind and upslope, on the north side of the fissure. Most of the pyroclastic products, however, fell downwind to the south of the fissure, but little was preserved due to two processes: (1) incorporation of proximal spatter in rheomorphic lava flows 10-20 m from the vents, and (2) the downslope transport of cooler spatter falling on top of these flows beyond 20 m from vent. The lava flow field itself shows a complex history. Initially, discharge from the fissure exceeded the transport capacity of the southern drainage pathways, and lava ponded dynamically to a maximum height of 4 m for 40-120 min, until fountains began to decline. During declining discharge, lava flowed both southward away from the fissure and increasingly back into the vents. There is a clear 'lava-shed' or delineation between where lava drained northwards back into the fissure, and where it continued flowing to the south. The 1969 deposits suggest that care is needed when products of less well-documented eruptions are analyzed, as postdepositional transport of spatter may preclude the formation of classic paired (symmetrical) ramparts. [ABSTRACT FROM AUTHOR]