楔横轧无料头辊剪制坯成形机理研究

为了解决楔横轧生产工艺中的料头缺陷,运用DEFORM-3D软件建立了无料头辊剪制坯的有限元模型,并通过网格法阐明了辊剪制坯工艺的成形机理。通过改变轧辊的旋转速度改善了堆料情况,提高了坯料端面的成形质量。在工艺参数允许的情况下,堆料值随着旋转速度的减小而减小。此外,提高辊剪过程的稳定性,防止坯料轴向窜动,也是解决堆料问题的方法之一。研究结果能为无料头楔横轧生产提供理论依据。

楔横轧无料头辊剪制坯端部质量研究

为解决辊剪工艺中的端面堆料缺陷,实现楔横轧无料头轧制,运用DEFORM-3D软件建立了辊剪制坯的有限元模型,通过位移法阐明了辊剪过程中堆料缺陷的产生机理,并通过改变工艺参数和创新模具设计的方法来抑制堆料,提高坯料端面的成形质量.结果表明:在设备功耗范围内,堆料值随着轧辊旋转速度的减小而减小,随着进给速度的增大而降低;在模具外圆周处添加挡块能有效地消除堆料缺陷.该研究结果为完善辊剪制坯工艺,实现楔横轧无料头轧制提供了技术支持和理论依据.

楔横轧辊剪制坯力的研究

为了阐明无料头楔横轧辊剪制坯工艺的变形机理,基于DEFORM-3D软件建立了它的刚塑性有限元模型,分析了辊剪制坯过程中应力应变变化情况以及工艺参数对力的影响规律,得到了辊剪制坯的应力应变场以及辊剪制坯展宽段变形规律。结果表明,随着旋转速度增大,径向力和切向力降低;随着进给速度增大,径向力和切向力也增大。结果能为完善辊剪制坯工艺、实现无料头楔横轧提供技术支持和理论依据。

无料头楔横轧辊剪制坯端面预估准则

辊剪制坯能有效抑制端面凹心,解决料头问题。通过有限元模拟得到了不同工艺参数下的轧件凹心值。利用端面移动计算程序得到了相应的拟合函数。通过体积守恒原则求得坯料外端相应的辊剪长度,建立坯料初始端面尺寸的预估准则,极大地提高楔横轧的生产效率,为辊剪模具与工艺设计提供理论支持。

鱼皮画的发展与制作

鱼皮画是赫哲族一种传统的艺术,有其独特的形成原因与生产工艺,随着社会的发展鱼皮画在其艺术形式与价值方面都有了很大的发展。

Shear deformation and plate shape control of hot-rolled aluminium alloy thick plate prepared by asymmetric rolling process

Asymmetric rolling （ASR）, as one of severe plastic deformation （SPD） methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achieved by adjusting the diameters of the upper roll and the bottom roll and was used to prepare hot-rolled thick plate of 5182 aluminium alloy. The shear deformation and plate shape control were experimentally studied. The experimental results show that asymmetrical rolling has a significant effect on metal deformation stream and can somehow refine microstructure and improve the uniformity of microstructure and properties. The asymmetrical rolling process can also reduce the rolling force. However, bending of rolling plate often happens during asymmetrical rolling process. The factors affecting the bending were discussed.

Effects of rolling parameters of snake hot rolling on strain distribution of aluminum alloy 7075

The realization way of snake rolling was introduced. Flow velocity, strain and stress distribution of 7075 aluminum alloy plate during snake rolling and symmetrical rolling were analyzed in Deform 3D. Effects of velocity ratio, offset distance between two rolls and pass reduction on the distribution of equivalent strain and shear strain were analyzed. The results show that flow velocity and equivalent strain on the lower layer of the plate are larger than those of the upper layer because of the larger velocity of the lower roll and the gap is increased with the increase of velocity ratio and pass reduction. The shear strain of roiling direction in the center point is almost zero during symmetrical rolling, while it is much larger during snake rolling because of the existence of rub zone. The shear strain is increased with the increase of velocity ratio, offset distance and pass reduction. This additional shear strain is beneficial to improve the in_homogeneous strain distribution.

发动机缸体裂纹的一种修补方法

在我国北方,冬季异常寒冷,稍有疏忽,水冷式发动机冷却系统的某些部件就会被冻裂。各型发动机缸体的裂纹部位常常在它的薄弱处。例如,495A和4100型发动机的主水道如果产生裂纹,部位多在发动机右侧第2缸和第3缸之间,距离缸体上平面10mm左右处。

Microstructure and texture evolution of AZ31 magnesium alloy during large strain hot rolling

Commercial AZ31 magnesium alloy sheets were rolled by nearly 70% thickness reduction in one rolling pass at 823 K. The results show that ultrafine grains are distributed in both shear bands and surfaces of the rolled sheets. The grain size of the refined grain in the shear bands is 0.4-1 μm. The outstanding grain refinement is attained by dynamic recrystallization due to flow localization. The texture in middle layer of the sheet is basal texture with little change in intensity throughout the rolling process, while the texture on surface becomes a double-peak texture with basal poles splitting in the transverse direction（TD）. The relative intensity of the double-peak texture is 26.6, which is quite higher than that of the texture in the middle layer. The inhomogeneous strain distribution is responsible for the exceptional grain refinement and texture evolution.

Phase field lattice Boltzmann model for non-dendritic structure formation in aluminum alloy from LSPSF machine

The formation of non-dendritic structures in the primary phase of an aluminum alloy solidified using low superheat pouring with a shearing field(LSPSF) machine was investigated by numerical simulation.The growth and motion of a dendrite during solidification was simulated by a combination of the lattice Boltzmann method and the phase field method.The simulation results indicated that enough shear flow helped homogenize the concentration fields,rotate crystals and altere microstructures from dendritic to non-dendritic.The interaction of grains was also discussed.A fragmentation criterion was established based on partial remelting of dendrite arms;fragmentation was enhanced by a strong shear flow and larger inclined angles.The simulation results were verified experimentally.

MobileNet network optimization based on convolutional block attention module

Deep learning technology is widely used in computer vision.Generally,a large amount of data is used to train the model weights in deep learning,so as to obtain a model with higher accuracy.However,massive data and complex model structures require more calculating resources.Since people generally can only carry and use mobile and portable devices in application scenarios,neural networks have limitations in terms of calculating resources,size and power consumption.Therefore,the efficient lightweight model MobileNet is used as the basic network in this study for optimization.First,the accuracy of the MobileNet model is improved by adding methods such as the convolutional block attention module(CBAM)and expansion convolution.Then,the MobileNet model is compressed by using pruning and weight quantization algorithms based on weight size.Afterwards,methods such as Python crawlers and data augmentation are employed to create a garbage classification data set.Based on the above model optimization strategy,the garbage classification mobile terminal application is deployed on mobile phones and raspberry pies,realizing completing the garbage classification task more conveniently.

An Analysis of the Kinetic Features of Scissor Elevator Mechanism and Its Optimized Design

A mathematical model has been established for the research on scissor elevator for ship passenger stairs.The kinematical and kinetic simulation analyses were carried out with MATLAB/Simulink.The relative kinetic relation between hydraulic cylinder and other parts,as well as its rules of change has been found.A 3-D model of ship scissor elevator was established with Pro/E.The design of the mechanism was optimized in Pro/MECHANICA based on the findings from simulation analysis.Practice has proved that the design is scientific and reasonable and could serve as the theoretical guidance and reference for the design of scissor mechanism of other uses.

Geological division of gas in the Pingdingshan mine area based on its tectonic dynamics characteristics

In this paper,we used tectonic dynamics theories to study the tectonic evolution characteristics of the Pingdingshan mine area,and analyzed the impact of tectonic progressive control on gas occurrence.The study results are as follows:the Pingdingshan mine area has been mainly controlled by multiple squeezing and shearing actions of the Qinling orogenic belt since early and middle Yanshan,forming the tectonic control characteristics of master control in two directions,namely NWW trending and NNE trending;the NWW trending structure is dominated by squeezing and shearing,while the NNE trending structure is dominated by tension.Progressively controlled by the structure,the gas occurrence presents partition and zonation,i.e.compared with the western structure,the eastern NWW-NW trending structure of the mine area is more highly developed,resulting in the mine area gas occurrence distribution characteristics are distinct in the east while indistinct in the west.Based on this,the mine area can be divided into the following two geological dynamic areas:the western half of mine area,namely the Guodishan fault control area,where the NW-SE trending synchronous tension action suffered by the northeast side(footwall) is relatively strong,and compared with the southwest side(hanging wall),its coal and gas outburst seriousness is weak;and the eastern half of mine area,namely the NWW-NW thrust nappe fracture fold control area,which is a serious area of coal and gas outburst,in particular the axial area of the Likou syncline is the intersection compound and combination position of the NW and NE trending structures,a tectonic concentrated area,and the gas pressure and content here are the largest.

Radial Orientation Mechanism and Experimental Research of Short Fiber in Tread Compound

Combining with Jeffery ：quation and mechanics model of fixed point of Euler rigid btdy, the mechanism and method of short fiber radial orientrion and characteristics of movement in tread extrusion process were studied. The influences of tension flow field and shear flow field in flow channel on short fiber orientation trove been systemically analyzed. The extrusion die, which had a hinder dam by adopting such principle, was designed. The results show that the expansion ratio and expanding angle of cross section are the key factors to determine the radial orientation of short fiber. Mathematical model of short fiber radial orientation was established. The results also show that the best expansion ratio is 3 - 4, the expanding angle is 75°, obtaining the average orientation angle between 70°- 80°, and the rationality of the radial oriented mechanism and the mathematical model are verified.

Study on Low-Temperature Traction Behavior of a Space Lubricating Oil No.4116

The traction behavior of space lubricating oil No. 4116 was measured and analyzed at various oil inlet temperatures below 0 ℃ and various rolling speeds under normal loads by a test rig simulating the operating conditions of space bearings. A traction coefficient calculation model was presented. The rheological property and rheological parameters of the lubricant at a low oil inlet temperature were analyzed based on the Tevaarwerk-Johnson model. The results showed that the lubricating oil No. 4116 was sensitive to the rolling speed and had lower sensitivity to the normal load. This lubricating oil is more suitable for applications under high speed when it is used below 0 ℃. It behaves as an elastic-plastic fluid operating below 0 ℃. Both the average limiting shear stress and the average elastic shear modulus have a negative correlation with the rolling speed and oil inlet temperature and have a positive correlation with the normal load.

Seismic behavior and mechanism analysis of innovative precast shear wall involving vertical joints

To study the seismic performance and load-transferring mechanism of an innovative precast shear wall(IPSW) involving vertical joints, an experimental investigation and theoretical analysis were successively conducted on two test walls. The test results confirm the feasibility of the novel joints as well as the favorable seismic performance of the walls, even though certain optimization measures should be taken to improve the ductility. The load-transferring mechanism subsequently is theoretically investigated based on the experimental study. The theoretical results show the load-transferring route of the novel joints is concise and definite. During the elastic stage, the vertical shear stress in the connecting steel frame(CSF) distributes uniformly; and each high-strength bolt(HSB)primarily delivers vertical shear force. However, the stress in the CSF redistributes when the walls develop into the elastic-plastic stage. At the ultimate state, the vertical shear stress and horizontal normal stress in the CSF distribute linearly; and the HSBs at both ends of the CSF transfer the maximum shear forces.

Optimal Control of a Beam with Discontinuously Distributed Piezoelectric Sensors and Actuators

Because of its light weight, broadband, and adaptable properties, smart material has been widely applied in the active vibration control （AVC） of flexible structures. Based on a firstorder shear deformation theory, by coupling the electrical and mechanical operation, a 4-node quadrilateral piezoelectric composite element with 24 degrees of freedom for generalized displacements and one electrical potential degree of freedom per piezoelectric layer was derived. Dynamic characteristics of a beam with discontinuously distributed piezoelectric sensors and actuators were presented. A linear quadratic regulator （LQR） feedback controller was designed to suppress the vibration of the beam in the state space using the high precise direct （HPD） integration method.

RNA-binding proteins in neurological diseases

Emerging studies support that RNA-binding proteins （RBPs） play critical roles in human biology and pathogenesis. RBPs are essential players in RNA processing and metabolism, including pre-mRNA splicing, polyadenylation, transport, surveillance, mRNA localization, mRNA stability control, translational control and editing of various types of RNAs. Aberrant expression of and mutations in RBP genes affect various steps of RNA processing, altering target gene function. RBPs have been associ- ated with various diseases, including neurological diseases. Here, we mainly focus on selected RNA-binding proteins including Nova-i/Nova-2, HuR/HuB/HuC/HuD, TDP-43, Fus, Rbfoxl/Rbfox2, QKI and FMRP, discussing their function and roles in human diseases.

On the material invariant of 110°-conjugate angle of shear bands——Reply to Gomez-Rivas and Griera(2015)

After their experimental data were re-explained in terms of the maximum-effective-moment （MEM） criterion, Gomez-Rivas and Griera （2015） challenge the validity of the MEM-Criterion in terms of shear fractures, which have mixed up with shear fractures and shear bands. The two features are similar in appearance but different in deformation mechanism （s）. The MEM-criterion proves that ±55° to σ1era are the maximum effective moment directions and the shear bands that formed by mate- rial-line （beddings or fabrics） rotation mechanism have a constant conjugate angle of 110°. Theoretically, the 55° or 110° is a material-invariant, and practically, a statistic-invariant or preferred direction with average deviation of -10°. By this angle, shear bands can be easily recognized from shear fractures with conjugate angle never over 90°. The High-strain deformation in the lozenges usually predates the surrounding shear bands. Two stress states can not coexisted simultaneously in the same place and the resolving cr1＇ normal to the related shear zone represents 0-100% deformation partitioning, depending on the original kinematic vorticity of the shear zones.