用弦角测量控制法确定型材成形的模拟实验与分析

船用型材冷弯成形常采用端点测量控制法,但采用该方法时,冷弯设备的检测机构庞大、操作不便、造价高、难于制造和安装。为此,提出一种弦角测量控制法代替传统的端点测量控制法实现型材的冷弯成形。为了验证该方法的可行性,采用铜线模拟型材的中性层曲线进行压弯实验,同时对压弯的支点距离、进料步长等进行分析和论证。结果表明,采用该方法获得的铜线形状与型材样条曲线基本吻合。研究结果可为型材冷弯成形提供理论依据。     

变曲率型材滚弯的压下量逐点设计法及其适用条件

在小变形的前提下,推导出在变曲率型材的滚弯过程中,坯料任意一点的成形过程与附近点的成形过程互不干扰的充要条件是:与塑性曲率对应的弯矩对无量纲弧长的相对变化率小于2.对于给定截面的型材,先通过定曲率滚弯的数值试验建立弹塑性梁的弯矩-曲率关系,再选择合适的辊距使得充要条件成立;然后采用逐点设计的方法求得中辊下压力与弧长的关...     

复杂截面铝合金型材拉弯成形有限元模拟

本文对矩形管截面铝合金型材拉弯成形工艺进行了研究 ,建立了位移控制拉弯工艺的有限元模型 ,采用ABAQUS软件对几种不同截面的铝合金型材拉弯成形过程进行了数值模拟 ,分析了不同补拉量对型材的截面畸变和回弹的影响以及不同截面形状抵抗拉弯成形时截面畸变的能力。其结果和方法对铝合金型材的拉弯成形工艺具有参考价值。     

塑料包覆铝型材拉伸弯曲实验研究

针对轿车用复杂截面PVC塑料包覆铝型材密封条的三维拉弯成形,采用控制拉伸量的方法,通过选择合理的预拉量、恰当的成形模具截面及型材间填充物,对该截面型材进行了平面和垂直拉弯成形实验,得到了该型材平面和垂直拉弯的半径回弹量。结果显示,垂直拉弯回弹量是平面回弹量的1倍多,实验结果为研制该型材及同类产品拉弯工装模具和工艺参数选择,提供了依据。     

精密冷弯技术在钣金自动化生产中的应用

随着冷弯工艺技术的进步,冷弯成形截面精度不断提高,可以达到0.02mm～0.04mm.同时,基于冷弯工艺特性,大量高强度、复杂截面型材以及特殊材料型材均采用该工艺技术生产.冷弯技术的广泛应用,给钣金加工带来变革;反之,钣金行业又对冷弯技术提出不少新的课题.     

中空铝合金型材拉弯成形工艺研究

拉弯成形工艺具有成形精度高、回弹量小、生产效率高的优点,对轨道列车端顶弯梁进行拉弯数值模拟与成形实验。利用数学解析法计算得到了型材拉弯过程中夹钳的运动轨迹,并定义了型材拉弯过程中典型的成形缺陷。利用有限元模拟对比分析不同选材和工艺参数下成形后零件的应力分布、回弹、截面畸变和空间扭转。研究结果表明:选用ENAW-6005-T4材料可以避免型材拉弯过程中的断裂;采用预拉0.5%和补拉1.5%的加载组合时,型材的卸载回弹量最小;采用1.5 MPa的填充压强可以有效地抑制型材外壁的内凹;改善摩擦条件可以减小成形后的空间扭曲。采用优化后的工艺参数进行了实验验证,测量结果和数值分析规律相吻合。     

基于虚拟弯曲理论的叠合型材冷弯成形

冷弯成形工件具有高效、经济的特点,发达国家每年冷弯成形工件的用量占钢铁用量的8%,而叠合型材是冷弯件中应用最多的一类,但由于存在回弹引起的质量问题,设计人员通常会以降低工件的其他性能以达到相似产品形状。该文基于型材叠合的虚拟弯曲理论,利用PROFIL冷弯轧辊计算机辅助设计软件及该软件自动建立ABAQUS模型的功能,分析冷弯成形过程。为验证虚拟弯曲理论的设计效果,分别建立了常见原始工艺路线和基于虚拟弯曲理论的叠合成形工艺路线,并利用有限元模拟,分析了两种板材叠合成形的工艺路线。受力分析结果和模拟结果均表明,叠合型材的补助弯曲设计可以解决叠合型材的回弹问题。     

铝合金型材拉弯有限元模拟

型材拉弯成形过程模拟属于高度非线性准静态问题,选择动力显示模块进行数值模拟时,需要考虑模拟分析步时间的敏感性。针对通用的型材拉弯工艺,在模拟分析步时间的敏感性分析基础上,采用ABAQUS/Explicit模块,建立了型材拉弯成形的准静态分析有限元模型。并采用ABAQUS/Standard模块分析预测回弹、侧壁厚度和截面畸变。为验证模拟方法的有效性,采用A-7B数控拉弯成形机完成2024-O铝合金Z型截面型材拉弯试验,测量试验件的回弹量、厚度和截面畸变情况。试验与模拟结果对比表明:补拉伸量对回弹量、厚度和截面畸变的影响趋势一致,其中,回弹量和厚度的平均相对误差分别为13.74%,1.66%。建立的模型能有效地应用于铝合金型材拉弯成形模拟。     

变截面辊弯成形边波机理

通过建立柔性变截面辊弯有限元模型,分析变截面型材边腿的应力应变变化过程,对变截面辊弯过程中型材边腿出现边波褶皱的机理进行研究。结果表明,型材凹弧区边腿在成形后纵向受拉,表面光滑无褶皱;当其纵向压应力足够大时,凸弧区边腿会由于失稳而褶皱,出现边波现象。增加边腿高度或减小边腿成形半径,均可以有效扩大凸弧区边腿的最大理论形变率,并增大边波的剧烈程度。     

型材2D拉弯数值模拟建模技术研究

型材拉弯成形有限元模拟关键在于型材夹持端运动轨迹的合理描述。对于由力控制的拉弯成形方式, 夹钳运动轨迹很难直接给出。本文探讨了拉伸作动筒的建模技术, 给出了型材2D拉弯数值模拟载荷边界条件的确定方法。应用动力显式有限元软件Pam -Stamp2000对挤压铝合金矩形管拉弯成形过程进行了数值模拟, 模拟结果和实验结果相当吻合, 证实本文提出的拉弯成形数值模拟建模技术是有效的、可靠的。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.