Hydrogen-rich blast furnace is one of the most important approaches to low-carbon ironmaking in China's blast furnaces. However, due to the differences in the reduction properties of H2 and CO, the softening-melting dripping behavior of sinter in hydrogen-rich blast furnaces is different, which in turn affects the formation of the softening-melting and molten dripping zone in the blast furnace. In this paper, the softening-melting-dripping behavior of sinter under different atmospheres was investigated by controlling the proportion of H2 in the reducing gas, and the mechanisms driving these changes were elucidated. The results indicate that the softening temperature of the sinter increases and the softening-melting interval becomes wider as the proportion of hydrogen increases from 0 % to 30 %. In addition, after reduction with H2 instead of CO, the melting and dripping temperatures of the sinter increased significantly, the molten dripping interval narrowed, the Delta Pmax of sinter decreased gradually, and the permeability of the sinter burden was improved. Notably, the effect of hydrogen-rich reduction on the FeO content is extremely significant, further affecting the softening, melting, and dripping behavior. The reason is that the high reactivity of hydrogen excessively promotes the reduction of FeO and hinders the generation of low melting point substances in the slag phase.

Abstract The thermal compression experiments of TB17 titanium alloy under different thermal deformation process parameters were carried out using a thermal simulation compressor. The high-temperature plastic flow behaviour of the alloy was studied. It was found that with the decrease of the deforming temperature and the increase of the strain rate, the flow stress increased, and the discontinuous yield phenomenon occurred in hot deformation. The larger the strain rate, the more obvious the discontinuous yield phenomenon. The thermal activation energy Q decreased with the increase of strain, and the average value of activation energy Q is 209.54 KJ / mol. The constitutive equation of high-temperature plastic flow of TB17 titanium alloy was established. The predicted values of this equation are in good agreement with the experimental values. The average error is 3.987 %, and the correlation coefficient is 0.9972, which has high accuracy. Based on the Prasad criterion, the hot processing map of TB17 titanium alloy was constructed. It was found that the flow instability zone was mainly concentrated in the high strain rate region. The flow instability zone was determined to be 795 °C ~ 895 °C, 0.046s-1 ~ 1s-1, and the stable deformation zone was mainly located in the region with high temperature and low strain rate. The optimum processing parameter range is 860 °C ~ 895 °C, 0.001 s-1 ~ 0.025 s-1.

Electroless copper-plated multiwalled carbon nanotube-reinforced titanium matrix (MWCNT-Cu/Ti) composites were prepared by spark plasma sintering (SPS). The microstructure evolution, interface characteristics and properties of the composites, including strength and corrosion resistance, were investigated. The results showed that the surface impurities and structural defects of the MWCNTs were successfully removed, and the oxygen-containing functional groups such as-OH, and -COOH were introduced by acid functionalization. The structure of the electroless-plated Cu layer is that of crystalline Cu. The precipitation of TiC phases by the interface reaction of the MWCNT-Cu/Ti composites is prevented. The compressive strength of the MWCNT-Cu/Ti composites was 2303 MPa, which is approximately 2 times greater than that of pure Ti. The corrosion resistance decreased in the order MWCNT-Cu/Ti > MWCNTs/Ti > pure Ti. The orientations of [11(2) over bar0]alpha-Ti//[1(1) over bar0]TiC, ((1) over bar100)alpha-Ti//(1(1) over bar1)TiC in the MWCNTs/Ti composites and Ti2Cu((2) over bar00)//Ti((1) over bar100), Ti2Cu (211) //Ti((1) over bar010) in the MWCNT-Cu/Ti composites are related.

For the inner wire joint parts in automobile brake pipeline, the boss structure which is the internal key part has the characteristics of small size and high size accuracy requirement. A six-die and six-punch cold heading processing method was adopted for production. Firstly, the orthogonal experiment of three factors and three levels were designed according to the key dimension factors affecting the boss forming. Secondly, Deform-3D finite element analysis software was used to analyze equivalent stress, equivalent strain and force distribution of die for the boss forming step in the orthogonal experiments, and the calculated deformation degrees of step 2-step 4 were 42.7%, 66.0% and 40.0%, respectively. At the same time, the affecting degrees of various factors on the boss forming was obtained as preformed boss depth ＞ flange height ＞ distance from upper end surface and top surface of preformed flange, and the optimal size combination was found under the conditions of full boss forming and minimum punch force, that is, the preformed boss depth is 9 mm, the flange height is 6 mm, and the distance from upper end surface and top surface of preformed flange is 11 mm. The study result provides a certain guidance for the cold heading of the similar boss parts in the future.

采用冷镦研究了 Ti-6Al-4V(TC4)钛合金管成形,采用Simufact有限元软件进行振动辅助预成形、正挤压、镦头、反挤压等成形工艺的仿真,研究钛合金材料在振动冷镦过程中的成形特性.通过正交试验法分析了振幅、振动频率和凸模进给速度对坯料成形规律的影响.结果表明:当凸模进给速度大于临界速度时,模具与材料保持接触不分离,成形力波动不明显;当凸模进给速度小于临界速度并施加振动时,模具和材料会随振动发生暂时分离现象,导致总的平均成形力减少,流动应力降低,且在每个道次的影响程度大小均为:振幅＞凸模进给速度＞频率.

To seek a fundamental understanding for further improving the Ti-6Al-4 V alloy utilization of cross-wedge rolling (CWR) and the comprehensive mechanical properties of shaft parts, the effect of the CWR processing parameters on the microstructure evolution of Ti-6Al-4 V alloy shaft preform is studied in this paper. An Arrhenius-type microstructure evolution model was employed and implemented into the finite element software DEFORM-3D. The average grain size and dynamic re-crystallization (DRX) volume fraction distribution in the α + β two-phase region and the β single phase region under different rolling temperature, roller rotating speed, and area reduction were analyzed, respectively. It is found that the microstructure evolution of Ti-6Al-4 V alloy is affected by CWR processing parameters. Meanwhile, the corresponding CWR metallographic experiments were conducted to verify the reliability of the FE-simulation results. The difference in average grain size in the β phase region between simulation and experimental is ranged from 5.77 to 18.56%. However, the agreement of the process parameter effect on dynamic recrystallization in the α + β two-phase region is reasonably well. The evenly distributed microstructure can be found as the area reduction rate of 50%, rolling temperature of 950℃ and the speed of 5 r⋅min−1 were employed. In addition, the higher tensile strength of Ti-6Al-4 V alloy shaft preform increased by 18.57% and the plasticity enhanced significantly due to smaller grain size and α + β two-phase microstructure can be obtained by CWR under optimized processing conditions.

In the paper, a novel method to improve the uniformity of the temperature distribution on the surface of the hot-plate is presented. Firstly, the effect of magnetic flux density under coupling of the electromagnetic and heat transfer on target surface temperature is studied numerically by using the commercial simulation software COMSOL Multiphysics. To evaluate the uniformity of the temperature distribution on the target surface, the temperature nonuniformity index on the target surface was firstly employed in terms of a specific designed electric coil. Secondly, the principal components analysis combined with the orthogonal test method is employed to analyze the shape parameters and obtain optimized temperature distribution at the target surface of the hot-plate. The simulated results show that the uniformity of temperature can be greatly improved by appropriately adjusting distribution of magnetic flux and the uniform temperature distribution can be achieved on a heating surface of 130 mm in length, 130 mm in width, and 30 mm in height. Finally, the optimizations of target surface temperature on hot-plate with different target temperatures were studied as well.

The skew rolling is a ideal metal forming technique for producing ball parts of various sizes. In order to analyze the forming mechanism ensuring the highest quality of copper ball during warm skew rolling, in this paper, a new modeling method was used for roller design based on the CREO platform. By using commercial FEM software Simufact 14.0, an FE simulation of warm skew rolling was established to predict the distribution of strain field, stress field, temperature field. meanwhile, the variation of rolling force and torque for copper balls during warm skew rolling were analyzed. Based on numerical simulation results, the deformation characteristics of copper ball during warm skew rolling is clarified. The simulation and experimental results Highly consistent and the copper balls have a high manufacturing quality confirm that the developed FE-simulation is reliable. This study was developed a new modeling method to overcome the difficulties and deficiencies in available finite element modeling process for complicated roller and lays a theoretical foundation for the high-quality copper balls manufacturing during warm skew rolling.

在3D打印中,成型方向的选择是影响产品成型质量的关键因素之一.针对目前算法仅考虑在等厚分层的前提下进行优化的问题,提出基于自适应分层的模型成型方向优化算法.首先结合3D打印层层叠加的特点,在分析不同成型方向对产品表面精度影响的基础上建立了以模型成型方向为变量、最小体积误差为目标的优化函数;然后通过STL模型的坐标变换、自适应分层等步骤并利用遗传算法在全局范围内搜索最优解,得到最佳成型方向.实验结果表明,该算法能够找到在自适应分层前提下的最佳成型方向,与现有算法相比能够进一步降低体积误差,提升表面质量.

由于实际中某些复杂性工程问题的解具有各向异性的特点,为采用更少的网格单元数及更好的单元质量来进行有限元分析,以实现高效求解,各向异性剖分单元则是一种有效的前处理技术.因此为生成高质量各向异性网格,首先在给定黎曼度量的基础上形成各向异性背景网格,然后通过各向异性Delaunay原则进行边交换,再基于力平衡实现节点的光滑平顺,由标准化面积和标准化边长规定节点的添加与删除,以及节点近似投影的边界约束,得到一个与具有方向性问题相匹配的网格.最后通过3个实例验证给出的各向异性网格划分算法的可行性.

Abstract In this paper, a novel method based on electromagnetic heating theory is introduced to achieve a stable and uniform temperature distribution on the target surface of the hot-plate. The heat process of hot-plate is divided into two stages. At first, the thin layer of S45C was coated on the surface of the hot-plate by thermal spraying. Due to skin effect, coated S45C layer can be considered as heat source in terms of the law of electromagnetic heating. Secondly, the hot-plate made of pure aluminium with a high thermal conductivity can be employed to reduce the temperature difference. Finally, the target surface temperature of the hot-plate is stabilized at specific temperature by changing the holding current.

针对鸡蛋检测分级系统复杂、集成化程度低、多品质因素综合检测的问题,设计出一体化的鸡蛋品质无损检测与分级系统,利用机器视觉算法实现了鸡蛋裂纹、尺寸、新鲜度与品质等级的自动化在线检测与分级.系统主要包括图像采集单元、分级单元、传输单元、图像处理单元和单片机控制单元.基于梯度幅度直方图和类间方差最大法进行自动阈值选取,对一级分级时的裂纹蛋进行剔除;采用外接最小矩形法测量鸡蛋最大横径、最大纵径、蛋行指数;利用鸡蛋透射图颜色信息的变化与哈夫单位值间的关系建立新鲜度BP神经网络,对鸡蛋新鲜度进行分级.试验结果表明,裂纹识别正确率为98.18％,对不同新鲜度等级的鸡蛋品质识别正确率为97.48％.

In view of the problem about uneven image acquisition and inaccurate edge extraction in pipeline detection process, a pipeline robot defect inspection method based on adaptive image enhancement is proposed. Firstly, a single-scale Retinex adaptive image enhancement algorithm is designed, which uses the guided filter to estimate the illumination component of the Value component of the image, and gets the illumination equilibrium image by adaptive Gamma correction, so as to realize the image enhancement. Then, the traditional Canny edge detection method is improved, using bilateral filtering to smooth the image. Besides, the defect images are segmented by the iterative threshold method, and the edge connection is carried out according to the edge pixel similarity. Therefore, the defect contour of the pipe-wall is extracted effectively. Thirdly, a pipeline robot defect detection system based on adaptive image enhancement is built, and a crawler car equipped with the pan-tilt-zoom camera conducts all-round visual inspection of the defects in the pipeline inner wall. The experimental results show that the detection method in this paper can adaptively correct the image brightness, and the uneven brightness of the image is significantly improved. Compared with the sub-optimal algorithm, the information entropy of the image is increased by 2.4%, the average gradient of the image is increased by 2.3%, and the peak signal to noise ratio is increased by 4.4%, and the pipeline defect edges are extracted effectively with the detection accuracy up to 97%.

The effect of the multistep imprint in elastic deformation recovery was studied numerically with more than one roll and different depth ratios. As well as effect hold-on time on the elastic deformation recovery of polymer Cyclic Olefin Copolymer (COC) material was studied using Generalized Maxwell (GM) constitutive model and their parameters in finite element simulation software of ABAQUS were presented. Firstly, the modified Genetic Algorithm (GA) was employed to obtain a Prony series of the viscoelastic model in terms of experimental data of the complex modulus for COC. To evaluate the elastic recovery of the microstructure, the cross-sectional area of micro-channel before and after hot-imprinting was computed and compared numerically. The simulated results were analysed and clearly showed an improvement in the elastic recovery rate of the microstructure area as the multi-step of rolling was employed.

基于Deform-3D软件建立双向偏心轴楔横轧成形的有限元模型,分析双向偏心轴楔横轧的成形原理,研究成形角、展宽角和坯料温度对偏心距的影响规律.应用MATLAB程序进行非线性拟合,验证双向偏心轴楔横轧成形的可行性.研究结果表明,成形角为31°、展宽角为6°、坯料温度为1 150℃时,双向偏心轴的楔横轧成形质量最优.

基于润滑近似理论,建立了毛细管力作用下牛顿及非牛顿流体在微纳米通道中的流动控制方程,其时间依赖性的接触角由实验数据拟合,弯月面曲率的变化规律可由其末点与初点曲率比值控制;并利用圆弧分割近似的方法得到不同时刻液体弯月面的动态变化,将该算法应用于求解牛顿流体酒精毛细作用下的液柱高度,结果与Hamraoui的实验吻合很好.该算法进一步扩展到求解非晶材料PC(聚碳酸酯)热压印过程中在微纳通道中的流动高度.通过模拟分析得知:当非牛顿指数n为0.715时,材料易流动且柱体高度上升快;Bond数为0.1时,毛细力对柱体弯月面的作用效果更强,弯月面高度值更大.

The deforming process is complicated and both the end concave and the central defect can be easily formed in multi-step shafts shaped by the cross-wedge rolling technology. To realize the accurate forming of multi-step shafts without stub bar, this article breaks the bondage of traditional flat-end billet, and introduces into convex-end billet. Based on established mechanical models and the damage computation principles, the distribution and change features of stress fields, strain fields and microstructures in different segments of the multi-step shaft during the progressive forming process are analyzed, and the location of the central defect is predicted. It is found that the concave depth of shaft ends decreases as the length of the convex-end of billet increases, the microcosmic grains are affected by the section shrinkage of the shaft segments and the larger the section shrinkage is, the smaller the size of the microcosmic grain will be. It records the longest duration of maximum stress, the largest fluctuation of lateral stress and the most frequent cycle of transverse strain in the multi-step shaft end and therefore the central defect is most likely to occur. The research findings settle a dependable theoretical basis for enhancing the molding quality and realizing the accurate forming for multi-step shafts in cross wedge rolling.

The slicing of the model is an important step for pre-processing of 3D printing. Aiming at current low efficiency of slicing and difficulty in effectively preserving subtle features, a new adaptive slicing is proposed in terms of STL model feature. The slicing result via a two-step optimization scheme are computed. Firstly, the feature edge of the model is extracted, and the surface with the feature edge is partitioned by the region growth algorithm. Secondly, the different strati-fication intersection algorithms are used for different surface types. Using VC++6.0 and OpenGL platform, the thicknesses of slicing layers are optimized adaptively to reduce the step effect, save the printing time and preserve the visual quality of printing results. In addition, optimized slicing direction can be achieved to obtain fine resolution of the part in terms of its actual printing direction.

In this paper, the effect of mandrel feeding speed was investigated numerically and experimentally for the inner ring of high-speed rail bearing made of GCr15. Firstly, the cold ring rolling process is simulated systematically using nonlinear finite element software package of ABAQUS. Nonlinear constitutive equation was employed to study rolling torque for material GCr15. Secondly, the effect of mandrel feeding speed modes on rolling torque was presented to find an optimized feeding speed mode. To verify the numerical results, cold ring rolling experiment was carried out. The agreement of the roundness of the inner ring and rolling torque between predicted and experimental is good. In addition, the metallographic experiment of the bearing ring before and after cold ring rolling was conducted to obtain microstructure of the part. The scanning electron microscope (SEM) technique was used to capture the sample before and after the process. It was observed that there were a small amount of spherical cementites and lamellar pearlites, and black carbide particles distributed uniformly in the inner ring, where the grains were significantly refined after cold ring rolling. Good agreement between experimental observation and numerical predictions indicated that the procedures were useful in capture the effect of the mandrel feeding speed for the high-speed rail bearing inner ring of cold ring rolling.