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.

Effect of Rolling Parameters on Plate Curvature during Snake Rolling

In order to predict the plate curvature during snake rolling, FE model was constructed based on plane strain assumption. The accuracy of the FE model was verified by the comparison between the plate curvature conducted by FE model and experiment respectively. By using FE model, the effect of offset distance, speed ratio, reduction, roll radius and initial plate thickness on the plate curvature during snake rolling was investigated. The experimental results show that, a proper offsetting distance can efficiently decrease plate curvature, however an excessive offsetting distance will increase plate curvature. A larger speed ratio, reduction will cause a large plate curvature, however a larger roll radius has effect to reduce plate curvature. Plate which undergoes a larger reduction and plate with a larger initial thickness always need a larger offset distance to keep the plate the minimum plate curvature, but for a larger roll radius a smaller offset distance is needed.

Continuous FEM simulation of multi-pass plate hot rolling suitable for plate shape analysis

In order to continuously simulate multi-pass plate rolling process,a 3-D elastic hollow-roll model was proposed and an auto mesh-refining module with data passing was developed and integrated with FE software,Marc.The hollow-roll model has equivalent stiffness of bending resistance and deformation to the real solid and much less meshes,so the computational time is greatly reduced.Based on these,the factors influencing plate profile,such as the roll-bending force,initial crown,thermal crown and heat transfer during rolling and inter-pass cooling can be taken into account in the simulation.The auto mesh-refining module with data passing can automatically refine and re-number elements and transfer the nodal and elemental results to the new meshes.Furthermore,the 3-D modeling routine is parametrically developed and can be run independently of Marc pre-processing program.A seven-pass industrial hot rolling process was continuously simulated to validate the accuracy of model.By comparison of the calculated results with the industrial measured data,the rolling force,temperature and plate profile are in good accordance with the measured ones.

Bending analysis and control of rolled plate during snake hot rolling

In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element(FE) models were established. Effects of different initial thicknesses, pass reductions, speed ratios and offset distances on the bending value of the plate were analyzed. ‘Quasi smooth plate' and optimum offset distance were defined and quasi smooth plate could be acquired by adjusting offset distance, and then bending control equation was fitted. The results show that bending value of the plate as well as the extent of the increase grows with the increase of pass reduction and decrease of initial thickness; the bending value firstly increases and then keeps steady with the ascending speed ratio; the bending value can be reduced by enlarging the offset distance. The optimum offset distance varies for different rolling parameters and it is augmented with the increase of pass reduction and speed ratio and the decrease of initial thickness. A proper offset distance for different rolling parameters can be calculated by the bending control equation and this equation can be a guidance to acquire a quasi smooth plate. The FEM results agree well with experimental results.

Analysis of strain variation in cross shear zone of plate during snake hot rolling

In order to study the distribution of equivalent and shear strain of aluminum alloy plate during snake hot rolling, several coupled thermo-mechanical finite element models(FEM) are established. Effects of speed ratio and offset distance on strain distribution of the plate are analyzed. The length of cross shear zone is defined to have a better understanding of the deformation characteristic in cross shear zone, which is the essential difference from symmetrical rolling in deformation zone. The results show that the equivalent strain and shear strain of lower part both increase with the increase of speed ratio, while the upper part decreases; the equivalent strain through the whole thickness decreases with ascending offset distance, while the shear strain of lower part increases. The length of cross shear zone quickly increases with ascending speed ratio and slightly decreases with ascending offset distance. The "positive" and "negative" cross shear zones are formed with the increase of speed ratio and offset distance, respectively. The value of the sensitivity coefficient of speed ratio is an order of magnitude bigger than the offset distance. However, the shear strain at center point increases with the ascending speed ratio and offset distance for different mechanism. As speed ratio increases, the asymmetry of the distribution of equivalent is becoming larger and the shear strain is generated in the same direction in cross shear zone. The FEM results agree well with experimental results.

INFLUENCES OF EDGING ROLL SHAPE ON THE PLASTIC STRAIN DISTRIBUTION OF SLAB DURING MULTI-PASS V-H ROLLING PROCESS

Multi-pass slab vertical-horizontal （V-H） rolling process with variable edging roll shape have been simulated with explicit dynamic finite element method and updating geometric method. The distributions of plastic strain contour in slab daring rolling process with different edging roll and under different rolling stage have been obtained. The results show that there exist two thin strain assembling zones in slab when the flat edging roll is used, and there just exist one strain assembling zone in slab when the edging roll with groove is used. And compared the deformation equality between flat edging roll and edging roll with groove, the lateris better than the former, which supplies the theory prove to the slab deformation distribution during V-H rolling process and is helpful for predicting the slab texture.

2205/Q420/2205蛇形轧制复合变形规律研究

为研究三层不锈钢复合板在不同工艺参数下轧制复合的变形规律,采用ANSYS有限元软件模拟了2205/Q420/2205三层复合板轧制复合过程,研究了同步轧制、同速异径轧制和同速异径蛇形轧制三种不同工艺下,复合板结合界面等效塑性应变和弯曲曲率的变化规律,分析了不同压下率、初始厚度比和错位量对轧后板形的影响规律,并进行了轧制复合实验。研究结果表明,蛇形轧制通过调整错位量,能有效提高轧后板材界面结合强度并降低轧后弯曲。轧后弯曲曲率随着压下率的增大呈现出先减小后增大的趋势。等效塑性应变随着错位量的增加先增大后减小,轧后弯曲曲率随着错位量的增加逐渐降低,这表明通过适当调整错位量可以使轧后板材同时达到优良的结合强度和平直度。

厚规格板材异步和蛇形轧制分析及研究综述

随着钢铁行业和工业技术的飞速发展,各种规格和不同种类的板材相继出现,蛇形轧制技术在其中起到了重要的作用,它是为解决厚规格板材异步轧制复合弯曲问题发展而来的一种新型轧制工艺。自2001年蛇形轧制出现以来,受到了国内外专家学者和各种钢厂的广泛关注。为了使读者对蛇形轧制技术及应用能够有更加全面的了解并深入认识到新型工艺的发展前景,文中首先介绍了异步轧制和蛇形轧制工艺技术,给出了蛇形轧制在应用领域的优势所在;然后从蛇形轧制的基本原理着手,将理论与实践有机结合,进而重点概述了蛇形轧制在应变、弯曲曲率、轧制力以及力学性能和组织性能机理分析三个方面的国内外研究现状;最后,总结分析了当前蛇形轧制技术在工业中的应用发展前景,为新一代热机械控制加工工艺的革新提供方向指导。

双层金属板材同速异径蛇形轧制复合变形研究

采用ANSYS Multiphysics/LS-DYNA软件对Q345碳钢/NM400耐磨钢复合板轧制复合过程进行了有限元模拟,并开展蛇形轧制实验,验证了所建立有限元模型的准确性。总结了轧辊直径、错位量、摩擦条件和压下量对复合板变形行为的影响,结果表明,其他工艺参数不变条件下,初始辊径和摩擦条件对复合板平直度的影响较大,初始辊径越大和摩擦系数越小,复合板越平直;错位量和压下量对复合板结合面处等效塑性应变的影响较大,错位量适当增大,压下量越大,复合板结合面处变形更充分;轧辊直径对复合板厚度比影响较大,轧辊直径越大,复合板层厚比越大。其中蛇形轧制错位量的调整可同时实现对板材厚度比、等效塑性应变和弯曲曲率的正向调控,证明了可以通过调整蛇形轧制的错位量获得形性兼优的金属复合板。

非对称轧制及冷却对中厚板板形及应变的影响

基于非对称轧制与差温轧制在提高厚板心部变形程度的优势,在蛇形轧制的基础上研究了差温轧制对厚板心部变形程度和轧后弯曲的影响规律。采用有限元软件,模拟不同工艺参数下的中厚板蛇形轧制过程,研究不同错位量、异速比对心部变形及轧后弯曲的影响规律。根据轧后板材弯曲情况,设定轧后冷却策略,模拟非对称冷却抑制弯曲的影响规律。开展差温轧制模拟及实验,观察轧后板材心部变形情况,研究轧板组织性能变化。结果表明:蛇形轧制及非对称冷却均能够有效改善板形,如当初始厚度为60 mm、异速比为1.02、错位量为30 mm时,对轧后板材进行非对称冷却后,得到的板材最为平直。相对于均温轧制,差温轧制后板形心部变形程度提高,板材力学性能提升。以上研究为实际工业生产提供理论和技术参考。

Self-adaptive rolling motion for snake robots in unstructured environments based on torque control

Snake robots have great potential for exploring and operating in challenging unstructured environments,such as rubble,caves,and narrow pipelines.However,due to the complexity and unpredictability of unstructured environments,designing a controller that can achieve adaptive motion is crucial.This paper proposes a self-adaptive torque-based rolling controller for snake robots,enabling compliant motion in unstructured environments.First,a controller is designed to modify the torque of each motor by focusing on the different motion states of the rolling gait.Second,an experimental platform is established for snake robots to verify the effectiveness of the controller.Finally,a series of rolling experiments are conducted using the torque-based rolling controller.In conclusion,the self-adaptive torque-based rolling controller enhances snake robot adaptability and mobility.

蛇形轧制复合成形镁/铝板材的弯曲曲率研究

针对镁/铝板材轧制复合在轧后容易出现弯曲问题,提出了蛇形轧制复合工艺,以达到降低轧后弯曲曲率并提高界面结合强度的目的。利用ANSYS LS-DYNA有限元软件,研究了蛇形轧制复合过程中不同错位量、异速比、压下量、层厚比及轧制温度对轧后复合板的弯曲曲率的影响规律,并开展轧制复合实验,验证了有限元计算结果的准确性。结果表明,与异步轧制相比,蛇形轧制可有效降低轧后复合板弯曲曲率。相同轧制条件下,异步轧制轧后弯曲曲率随着异速比的增大而增大,随着压下量及层厚比的增大而减小。蛇形轧制错位量可对轧后弯曲抑制产生明显的效果,在一定范围内,复合板的弯曲曲率随错位量的增大而减小。当初始板厚为50 mm、层厚比为2:3、压下量为30 mm、轧制温度为400℃、异速比为1.05和错位量为30 mm时,轧后复合板接近平直。

碳钢/不锈钢同速异径蛇形轧制复合变形规律

为提高碳钢/不锈钢板材轧制复合界面结合强度并降低轧后弯曲,采用ANSYS LS-DYNA有限元软件模拟了碳钢/不锈钢在1200℃开轧温度下的同速异径蛇形轧制复合过程,分析了不同压下率、辊径比、错位量与初始板厚等对轧后板材变形行为的影响规律,并进行了轧制复合实验,验证了有限元模拟的准确性。结果表明,与同步轧制和异步轧制相比,同速异径蛇形复合轧制能提高轧后板材界面结合强度并降低轧后弯曲。增大压下率可提高轧后板材界面的结合强度和轧后层厚比,且随压下率和辊径比的增大,轧后板材均出现反向弯曲,表明存在合适工况使轧后板材平直,如当初始板厚为20 mm,压下率为40%,错位量为5 mm,辊径比为1.15~1.20,初始层厚比为0.25~0.33时,轧后板材接近平直。

镁/铝板材同速异径蛇形轧制复合弯曲曲率研究

针对镁/铝板材轧制复合过程中金属流动性差异大,轧后容易出现弯曲的问题,提出了同速异径蛇形轧制复合工艺,可以降低轧后弯曲曲率。采用ANSYS/LS-DYNA有限元软件模拟了AZ31B/5052的轧制复合过程,分析了蛇形轧制复合过程中轧制温度、辊径比、压下量、错位量、层厚比及初始总板厚等参量与弯曲曲率的关系,并通过实验对模拟结果进行了验证。结果表明,相比于异步轧制,蛇形轧制能够降低复合板的弯曲曲率;相同轧制条件下,异步轧制弯曲曲率在一定范围内随层厚比的增大而减小,在1.01~1.20辊径比范围内,弯曲曲率随辊径比的增大而增大;在一定范围内,复合板的弯曲曲率随错位量的增大而减小,蛇形轧制有效抑制了轧后弯曲;当总板厚为8 mm、层厚比为0.25、压下量为3.6 mm、轧制温度为400℃、辊径比为1.01以及错位量为15 mm时进行轧制复合所得复合板接近平直。

Q345R/316L蛇形轧制复合应变及曲率研究

为解决同步轧制工艺制备复合板时出现的结合强度低和板材弯曲等问题,提出了同径异速蛇形轧制复合工艺。采用Deform-2D平台对碳钢Q345R/不锈钢316L蛇形轧制复合过程进行模拟,获得了变形及微观组织,对结合面等效塑性应变、弯曲曲率和晶粒大小进行了对比分析与研究。研究结果表明,与同步轧制相比,蛇形轧制能够显著提高复合板结合强度、降低弯曲程度并细化晶粒;在一定工艺参数范围内,结合面等效塑性应变随着初始层厚比、辊速比及工作辊直径的减小,压下率的增大而显著提高;在相同的工况下,当辊速比为1.20时,复合板接近平直状态;这为工业生产中制备性能优异且板形平直的复合板材提供技术支撑。

Insight into deformation allocation in the multi-pass roll forming of a double-walled brazed tube

Deformation allocation is an important factor that affects 720°curling forming from copper-coated steel strips to double-walled brazed tubes(DWBTs).In this study,four schemes of deformation allocation,considering different weights of the total feed distance,are proposed,and a 3D finite element(FE)model of the multi-pass roll forming process for DWBT is developed and verified to investigate the cross-sectional evolution and deformation features.The results show the following.(i)In the 720°curling forming process from the steel strip into double-walled tubes,the curvature of the formed circular arc initially increases and then remains stable with roll forming,and the inner and outer tubes of the DWBT are formed in the third and fifth forming passes.Size forming can eliminate the gap between the double walls and improve the overall roundness.(ii)For different deformation allocations,the cross-sectional profiles of the roll-formed parts exhibit a discrepancy,and the deformation amount varies with the roll-forming process.The deformation amount in Scheme three is the maximum,and the cross-sectional profile deviates significantly from the ideal shape and fails to form a DWBT,which indicates that the deformation allocation is unsuitable.(iii)The roundness of the outer tube is better than that of the inner tube.Therefore,the roundness of the inner tube is the key to restricting the forming accuracy of the DWBT.Compared with Schemes one and two,Scheme four with a linear allocation of the total feed distance exhibits the best roundness,and the deformation allocation is reasonable;i.e.,when the contact points between the rollers and steel strip are in a straight line,the roundness of the DWBT is in good agreement with the ideal condition.

The dynamic responses of lamellar and equiaxed nearβ-Ti alloys subjected to multi-pass cross rolling

This work gives a comparison on the microstructural characteristics,textural discrepancies,and twinning behaviors of lamellar and equiaxed nearβ-Ti alloys during multi-pass cross rolling with a rolling reduction of 20%,50%and 80%.The results showed that the restoration mechanism of the alloy inβphase is strongly dependent on theαmorphologies,and in comparison,strain path has weaker influences on the grain refinement of theβmatrix.Therefore,the texture intensities of bothαandβphases were weakened owing to the dynamic recrystallization(DRX)of the two phases in the equiaxed microstructure.While,with regard to the lamellar microstructure,dynamic recovery(DRV)of theβphase predominated,forming elongatedβsubgrains.Besides,theαandβmatrix in lamellar microstructures obeyed the Burgers orientation relationship,which was gradually broken down until the final reduction.Lastly,the{1101}twinning exhibits a strong size effect.With the continuous DRX ofαphases,theα-twinning is suppressed owing to progressive grain refinement.The activation ofβ-twinning,namely{332}?113?and{112}?111?,in nearβ-Ti alloys is heavily dependent on the deficientβ-stabilizing elements and the local stress concentration.These findings provide an effective way to obtain ultra-fine grain microstructures of this alloy.

主应力法计算蛇形轧制的轧制力

使用主应力法建立蛇形轧制过程中轧制力与轧制力矩的解析预测模型。将解析模型的计算结果与实验结果进行比较,验证了解析模型的准确性。运用该模型对蛇形轧制过程中不同的异速比、轧辊偏移距离、压下量和摩擦系数对轧制力和轧制力矩的影响规律进行研究。同时研究"搓轧区"对轧制力和轧制力矩的影响。结果表明,异速比的增大将导致"搓轧区"的增大,从而使轧制力和上轧辊轧制力矩减小,下轧辊轧制力矩增加。当异速比增大到速度较大的轧辊带动速度较小的轧辊时,慢速轧辊的轧制力矩将变为负值。轧辊错位距离的增大导致"搓轧区"减小,从而导致轧制力增加,上、下轧辊轧制力矩减小。压下量的增加导致"搓轧区"的减小,从而导致轧制力和上、下轧辊轧制力矩的增加。轧辊与轧板之间摩擦系数的增加使"搓轧区"减小,同时导致轧制力和上、下轧辊轧制力矩同时减小。研究为蛇形轧制在超大厚度板材制造中的应用,提供了理论基础。

蛇形轧制对Al-Cu-Mg合金板材强韧性能及微观组织的影响

基于实验室自制蛇形轧制装置,采用室温拉伸、Kahn撕裂、电子背散射衍射(EBSD)等测试方法对比研究蛇形轧制非对称工艺参数对Al-Cu-Mg合金轧制板材的室温强度、断裂韧性和显微组织的影响。结果表明:合理的蛇形轧制工艺在能够使Al-Cu-Mg合金板材保持强度性能的同时,显著提升其断裂韧性。当偏移量相同时,蛇形轧制板材的强度性能随着异速比增加而提高,但伸长率和断裂韧性降低;当异速比相同时,随着偏移量增加,蛇形轧制板材强度降低,伸长率和断裂韧性明显升高。在偏移量10mm且异速比为1.1的条件下,蛇形轧制试样裂纹单位形核能提升高14%~36%。这是由于蛇形轧制能够增强Al-Cu-Mg合金板材Cube织构并减弱Brass织构,形成具有更高裂纹扩展阻力的织构组态所致。

蛇形机器人的翻滚运动及其越障研究

提出了一种新型蛇形机器人机构。该机构既可以实现平面运动又可以实现空间运动。建立了其空间运动学模型并实现了空间翻滚运动。实验结果表明 :翻滚运动不需依靠模块与地面之间动摩擦力方向差来实现驱动 ,而是通过模块与地面之间静摩擦力和互相垂直的两个运动平面内异相波的相互作用产生驱动力。翻滚的方向和姿态由两个波形曲线的相差和传播方向决定。利用翻滚运动 。