连续挤压铜扁排的阻流角设计及物理场分布

基于Deform-3D平台,建立了Conform连续挤压生产大宽厚比铜扁排有限元模型,研究了连续挤压过程中阻流角变化对模具出口处金属流动及相应应力场分布的影响规律,并结合方差分析法获得了模具出口处的流速均方差,观察模具阻流角对扁排成型的影响.研究表明:模具阻流角从3°~15°变化时,随着阻流角的增加,金属流速均方差先增大后减小,其阻流角区域等效应力值以及模具入口处沿挤压方向应力也逐渐增加;在定径带长度一定以及模具载荷允许的情况下,选择3°、5°、15°的阻流角可使模具出口处金属流速相对稳定,扁排成形性较好;当模具容易损坏时,选择3°和5°阻流角既可降低模具载荷又可获得板形均匀的扁排.     

实心边框铝型材挤压数值模拟与模具结构优化

目的针对汽车用某实心边框铝型材出口流速不均匀的现象,改进模具的工作带、阻流块和促流角结构。方法运用专业铝型材挤压成形有限元软件系统,对型材的挤压过程进行分析,模拟稳态挤压成形过程,以速度相对差作为衡量速度均匀程度的指标。结果初始模具结构挤出的型材流速不均匀。通过改变工作带长度、增设阻流块以及增加促流角的方法,使得模具出口处的金属流速变得均匀。结论改进后模具所受的压力更小,可以减小模具的磨损,增加模具寿命,模拟结果与实验吻合。     

大型复杂薄壁铝合金空心型材挤压成形工艺

目的 解决大型复杂薄壁铝合金空心型材挤压过程中材料流速均匀性控制难,以及模具局部应力集中导致模具寿命低、挤压型材尺寸稳定性差的问题。方法 采用有限元模拟方法对此类典型型材挤压过程进行仿真分析,根据仿真结果中型材出口材料流速分布情况,通过调控不同部位材料流入量及材料流动阻力,并以型材出口流速差和流速均方差（SDV）作为衡量挤压过程中材料流速均匀性的指标,逐步迭代优化模具结构以提高材料流动均匀性;根据仿真结果中挤压模具应力分布情况,以模具最高应力作为衡量模具强度的指标,逐步迭代优化模具结构以减小模具应力。结果 通过迭代仿真依次优化模具工作带长度、分流孔尺寸、阻流块高度等参数,最终型材出口流速差由25.07 mm/s降至2.72 mm/s,流速均方差由9.84 mm/s降至0.72 mm/s;通过迭代仿真优化焊合角度,最终模具最高应力由945 MPa降至863 MPa。采用基于有限元仿真优化结构的挤压模具成功制备了合格的铝合金型材样件,挤压试验结果与数值模拟结果吻合。结论 通过优化模具工作带长度、分流孔尺寸及阻流块高度,调控不同部位材料流入量及材料流动阻力,能够有效解决大型复杂薄壁铝合金空心...     

基于模具创新设计的高强钛管小半径加热绕弯扁化控制

目的 发展小直径高强钛管小弯曲半径(R=1.5D)加热弯曲成形的截面扁化缺陷控制技术.方法 基于对管材弯曲前预变形和弯曲过程中施加有效约束的原理,设计变曲率型腔的反变形压力模结构、勺形芯模结构和带芯球的柔性芯模结构,结合有限元仿真分析,研究探索不同模具结构设计对弯管截面扁化的影响.结果 与"压力模+圆形芯棒"模具组合相...     

U型铜材连挤连展工艺产品极限尺寸的研究

采用U型模具连续挤压铜板带时,U型产品尺寸的变化对连续挤压成型过程会产生较大的影响。为了降低模具研发成本,本文通过有限元模拟与解析法得到了U型产品可挤压的极限尺寸。采用有限元法与理论计算研究了不同几何参数比(厚度挤压比λ₁、直径扩展比λ₂、产品宽厚比λ₃)对U型连续挤压产品的流速均方差(SDV)以及模具型腔压力σ_x、挡料块应力p_d和挤压轮扭矩T的影响规律,并建立了模具型腔内接触应力和挤压轮扭矩的函数模型。研究表明:随着λ₁的增大,出口截面的速度差越来越大,SDV值增加幅度明显;λ₂增大,流速最快区域从U型两侧转移至圆弧处,SDV值变化范围不大。通过主应力法计算得到U型模具腔体内压应力σ_x与产品尺寸r₀的函数,利用上限法求解出挡料块应力p_d与腔体进料口压力p_k的关系。将SDV、p_d、T作为挤压极限厚度的判定标准,当坯料直径为30 mm,展平宽度为420 mm时,得到可挤压的极限厚度为7 mm。U型铜带连续挤压实验表明,实验结果与理论扭矩对比,误差可控制在10%以内,证明了理论计算极限尺寸的可行性与准确性。     

热泵平行流换热器结构参数对换热性能的影响

采用正交试验法及模拟仿真分析，研究了热泵平行流换热器的结构参数对换热器换热量等指标的影响。结果显示：扁管宽度是对换热器换热量影响最大的因素，贡献率达43.1%;随着扁管宽度增加换热器换热量大幅提升。扁管厚度对换热器换热量影响较大，贡献率达29.7%;当扁管厚度超过2 mm,随扁管厚度增大换热器换热量大幅下降，这主要与换热器背风侧的气流低速区较大，且换热效率低有关。翅片卡槽间距对换热器换热量贡献率为20.8%,翅片卡槽间距为11 mm时换热器换热量最优。翅片卡槽深度对换热器换热影响较小。     

非均匀退磁场对NiFe薄膜AMR元件性能的影响

采用磁控溅射制备了NiFe各向异性磁电阻(AMR)薄膜,经过光学曝光及离子刻蚀将NiFe薄膜制成了宽度w=20μm、厚度t=20nm、长度l=2.5mm的AMR元件.测量了NiFe元件的磁电阻效应.考虑沿宽度方向退磁场的非均匀性,计算了磁电阻比率.结果表明,理论和实验符合.     

扁形钛铜复合棒挤压模具设计与应用

对长宽比较大的扁形截面钛铜复合棒的挤压模具进行了设计研究。通过合理选材,并选择使挤压力最小的模具模腔轮廓曲线和半模角,改变模孔工作带的几何形状与尺寸,选择适当的挤压速度等,优化设计制备出扁形钛铜复合棒专用挤压模具。增加工作带长度可以增大摩擦阻力,使向该处流动的供应体的流动静压力增大,迫使金属向阻力小的方向流动,从而使型材整个断面上金属流量更加均匀。挤压实验结果表明,合理的模具设计对挤压材的挤压过程和挤压制品质量有重要影响,锥形模具更适合于扁形钛铜复合棒的挤压。解决了科研生产实际对大的长宽比扁型钛铜复合棒的需求。     

熔体快淬对纳米晶和非晶Mg2Ni型合金贮氢动力学性能的影响

用快淬技术制备了名义成分为Mg2Ni1-xCox(x=0、、0.1、0.2、0.3、0.4)的贮氢合金.获得长度连续,厚度约为30μm,宽度约为25mm的快淬合金薄带.用XRD、HRTEM表征了快淬态合金薄带的微观结构,用自动控制的Sieverts设备测试了合金的吸放氢动力学性能.用程控电池测试仪测定了合金薄带的电化学...     

快淬纳米晶/非晶Mg2Ni1-xMnx(x=0～0.4)合金电极的电化学性能

用快淬工艺制备了纳米晶和非晶Mg2Ni型Mg2Ni1-xMnx(x=0、0.1、0.2、0.3、0.4)合金,获得长度连续,厚度约为30μm,宽度约为25mm的薄带.用XRD、HRTEM分析了快淬合金薄带的微观结构,测试了合金薄带的电化学性能及电化学交流阻抗谱(EIS),测试了电位阶跃后的阳极电流-时间相应曲线,并计算...     

Numerical investigation of an arc inlet structure extrusion die for large hollow sections

This paper aims to improve the working life of extrusion dies by optimal structure design, which plays an important role in mass production. First, an arc-shaped inlet die structure for an aluminum large-hollow-section profile was developed. Second, a three-dimensional finite-element model of the porthole extrusion process was established using an arbitrary Lagrangian-Eulerian method. Third, the comparison of the formability was analyzed and discussed, including the diversity of extrusion forces and uniformity properties between the proposed design and two traditional design schemes using the same extrusion process. A group of square-profile extrusion dies was used to set up a L16_4_3 orthogonal experimental scheme, considering the side length of profiles, L, with four levels, 110, 100, 90, and 80 mm; inlet angles, α, of the porthole bridge of 0°, 10°, 20°, and 30°; and profile wall thicknesses, t, of 1, 1.5, 2, and 2.5 mm. The results of the orthogonal tests were similar to those of the actual production die model. Two different analysis models reached the same conclusion: the inlet angle or the arc inlet structure has a small effect on the metal flow and the forming distribution, but the arc inlet structure can alleviate the stress load of the dies. The die testing and production validation results indicate that the novel structural design of the arc inlet die will have a long working life.     

Influence of inlet conditions on vortex characteristics

Vortex chambers are normally used for arc stabilization in linear plasma torches. In the present work, the effect of uniformity of the gas inlet channel distribution on the stabilizing characteristics of a swirled flow is studied numerically. The formation of a complex flow pattern with a toroidal recirculating flow area inside the vortex chamber is observed. For some regimes, two local maxima of the tangential velocity are observed in the middle section of the chamber. It is shown that an increment of the number of gas inlet channels leads to a more uniform gas input with disappearance of the second maximum, which increases the velocity amplification coefficient and, correspondingly, results in a better stabilizing effect. The obtained profiles of the radial distribution of the tangential velocity are compared with the results of Oseen’s equation for an unconfined vortex.     

7022铝合金FSJ连接区减薄机理分析

针对10mm厚的7022铝合金进行了FSJ连接实验,并利用工具显微镜对连接区横截面形貌进行分析研究。结果表明,前进侧的连接区塑化金属在搅拌针表面的挤压作用下瞬时针方向流入空腔,后进侧的连接区塑化金属在搅拌针表面的挤压作用下逆时针方向流入空腔。轴肩摩擦软化的塑化金属在搅拌头高速旋转下,形成涡旋流动并在轴肩下压力作用下流入空腔;随着搅拌针的高速旋转,空腔内的塑化金属向四周挤压,致使母材发生塑性变形,同时将底部部分塑化金属挤压到母材上表面,且在轴肩下压力作用下,挤压到轴肩外围形成"飞边";由于涡旋流动,致使连接区中间部位的金属层下凹,形成连接区表面中间部位凹陷。造成了连接区"减薄效应"现象发生。"填充式间接挤压-涡旋流动"模型能准确表达连接区金属塑性流动和减薄形成过程。     

Experimental study of the gas flow behavior in the inlet of a granular bed filter

The Moving Granular Bed Filter (MGBF) is an important apparatus being developed for filtration of the hot gas. Our research group demonstrated a good solution to diminish stagnant zones in MGBF during the filtration process. However, there still remain some systematic problems that have to be worked out prior to commercializing a whole facility.The design of the gas inlet component of the granular bed filter is important for achieving a uniform gas distribution and higher usage rate of the filter media. Non-uniformity may lead to a lower usage rate. The new gas inlet component design uses baffle devices in order to achieve a more uniform gas velocity distribution. Fixed bed and moving bed conditions were studied. The uniformity of the gas velocity distribution can be characterized by the standard deviation definitions and the differences in the mean velocities between the two filtration surfaces. The baffle lengths and angles affected the uniformity of gas velocity in inlet and filtration surfaces. The optimal experimental parameters were found by using different baffle lengths, angles and mass flow rate of filter media. The uniform gas velocity distributions were obtained by a series experiments. Furthermore, the results give important information about IGCC system that will be helpful for designing better models of moving granular bed filters in the future.     

磁控溅射膜厚均匀性与靶-基距关系的研究

从理论上分析了平面磁控溅射靶沉积薄膜的厚度均匀性.根据磁控溅射阴极靶刻蚀的实际测量数据,建立了靶的刻蚀速率方程,以此为依据,对膜厚均匀性的有关公式进行了讨论.采用计算机计算了基片处于不同靶-基距时,膜厚均匀性的分布.研究结果表明,随着靶基距的增加,膜厚均匀性逐渐变好.在同样的靶基距下,沿靶长度方向的均匀性明显优于宽度方向.最后,通过实验证实了上述结论.     

碳纤维壳体壁厚对陶瓷球初速及性能的影响?

为控制低附带毁伤战斗部中杀伤元的杀伤范围及杀伤威力,研究战斗部壳体厚度对初速及性能的影响。将炸药与陶瓷球混合构成新型复合装药结构,采用LS-DYNA软件对不同壁厚的战斗部进行数值模拟,从中筛选出壁厚为2、4、6 mm的壳体,进行静爆试验。对比分析得出,仿真与试验结果规律吻合较好,陶瓷球的初速与壳体厚度线性相关。相同装药结构中,随着壳体厚度的变化,爆轰瞬间,陶瓷球的初速、强度、毁伤效能等均有相应变化。可适当调节壳体壁厚来控制陶瓷球的初速。     

双向凸台皮带轮冲锻成形有限元分析

根据皮带轮壁厚不均匀且带有双向凸台的结构特点,对其进行冲锻成形工艺研究。利用有限元软件Deform-3D对冲锻阶段金属的流动、成形缺陷及成形载荷进行模拟分析,并采取在冲锻模上模增加不同高度分流槽的形式来降低成形载荷。结果表明,对于双向凸台皮带轮可以采用冲锻成形工艺来成形;在分流槽高度为2mm时,成形效果良好,成形载荷较小。     

The effect of oscillating flow on a horizontal dilute-phase pneumatic conveying

ABSTRACT

A horizontal dilute-phase pneumatic conveying system using vertically oscillating soft fins at the inlet of the gas–particle mixture was studied to reduce the power consumption and conveying velocity in the conveying process. The effect of different fin lengths on horizontal pneumatic conveying was studied in terms of the pressure drop, conveying velocity, power consumption, particle velocity, and intensity of particle fluctuation velocity for the case of a low solid mass flow rate. The conveying pipeline consisted of a horizontal smooth acrylic tube with an inner diameter of 80 mm and a length of approximately 5 m. Two types of polyethylene particles with diameters of 2.3 and 3.3 mm were used as conveying materials. The superficial air velocity was varied from 10 to 17 m/s, and the solid mass flow rates were 0.25 and 0.20 kg/s. Compared with conventional pneumatic conveying, the pressure drop, MPD (minimum pressure drop), critical velocities, and power consumption can be reduced by using soft fins in a lower air velocity range, and the efficiency of fins becomes more evident when increasing the length of fins or touching particles stream by the long fins. The maximum reduction rates of the MPD velocity and power consumption when using soft fins are approximately 15% and 26%, respectively. The magnitude of the vertical particle velocity for different lengths of fins is clearly lower than that of the vertical particle velocity for a non-fin conveying system near the bottom of the pipeline, indicating that the particles are easily suspended. The intensities of particle fluctuation velocity of using fins are larger than that of non-fin. The high particle fluctuation energy implies that particles are easily suspended and are easily conveyed and accelerated.