曲面构件外环约束无模旋压新工艺

为了有效解决大径厚比曲面构件在传统旋压过程中出现的法兰起皱失稳缺陷以及减少生产模具带来的高昂成本,提出了外环约束无模旋压新工艺,并分析了该工艺成形的基本原理。运用合适的工艺窗口,采用多道次逐次逼近的旋压方式得到目标成形件,并对目标件的壁厚均匀性和轮廓精确性进行实验研究。分析表明:在加工过程中,不同的旋轮轨迹路径会导致成形件的中心下沉缺陷;而加载合适的旋轮轨迹得到的目标成形构件的壁厚遵循中心较厚,边缘较薄的分布规律,沿成形件母线上的各点的实际壁厚均位于理论壁厚上下限之内,壁厚均匀性良好且无明显缺陷。     

Safety analysis of 200 m LPG spherical tank manufactured by the dieless hydro-bulging technology

This paper briefly introduces the design and manufacturing process of a 200 m³ LPG spherical tank manufactured by the dieless hydro-bulging technology, and then puts emphasis on its safety analysis. The results of measurements and experiments show that the geometrical tolerance and the mechanical properties can meet the requirements of the concerned codes, the wall thickness distributes evenly and there exist compressive residual stresses on the inside surface, which latter are favorable for preventing the hydro-bulged spherical tank from stress-corrosion cracking (SCC) and can improve the fatigue strength.     

三辊轧管机组厚壁管轧制壁厚不均研究

分析了三辊轧管机组在轧管过程中过大的扩径穿孔率、不合理的变形量分配以及各工序轧辊形状等对厚壁钢管 (D /S≤ 6且S≥ 2 2 ) 壁厚不均的影响 ,得出扩径率控制在 5%以下 ,轧管变形量在 2 5mm以下 ,及选择相匹配的坯料直径和顶杆、顶头尺寸等有利于保证厚壁管的壁厚精度     

Fundamentals for controlling thickness and surface quality during dieless necking-in of tubes by spinning

Dieless necking-in by spinning is a highly flexible process to manufacture tubular parts with variable cross-sections and nearly arbitrary contours. However, the thickness distribution of such products is influenced primarily by the toolpath. Based on analytical models this study introduces the fundamentals to control the tube thickness. Two principal tool movements are identified causing different deformation modes: shear-necking, which leads to thickening, and stretch-necking, which leads to thinning. Based on an additional model for the surface quality general criteria are derived to setup basic process parameters. The developed approach is validated by various experiments.     

Effect of the hydrobulging process on mechanical properties of spherical pressure vessels

This paper deals with the effect of large plastic deformation and angular deformation occurring during the hydrobulging process of polyhedral shells on mechanical properties. The results of the experiments show that strain ageing resulting from the plastic deformation causes increase of strength and decrease of plasticity and toughness of steel and its welded joints. The increasing or decreasing degree mainly depends on magnitude of the plastic deformation. The larger the plastic deformation, the more serious the unfavorable effect of the strain ageing. Appropriate heat treatment can eliminate the unfavorable effect and recover the mechanical properties to the original values.     

非均质厚壁球壳液压胀形过程有限元模拟

对非均质厚壁球壳液压胀形过程有限元模拟进行了研究 ,探讨了壳体液压胀球过程中的应力应变的分布规律。研究结果表明 :随着屈服强度比Yr 增大 ,焊缝的内侧应力变化梯度增大 ,热影响区的应力梯度明显增大 ;最大等效应力点的位置逐渐由热影响区转换到焊缝 ;应变由焊缝向热影响区转移 ,即热影响区的相对应变增大 ,应变由内向外逐渐变小 ,但应变梯度的变化较小。     

压力容器免除焊后热处理的最大厚度

工程实践表明现代钢材质量与焊接技术足以保证结构钢在更大厚度时免除焊后热处理,相关厚度值远高于现行规范源于工程经验的最大焊后热处理(Post weld heat treatment,PWHT)豁免厚度规定。从压力容器防脆断的角度出发,基于断裂力学原理,研究了材料最大PWHT豁免厚度的影响因素,结合Q345R钢性能数据,评价了具体厚度值的工程适用性,分析指出保守的防脆断条款是导致我国压力容器规范最大PWHT豁免厚度小于欧美规范的根本原因。     

橡皮囊液压成形模拟算法的开发及应用

基于有限元增量理论和BWC壳单元,提出一种新的快速模拟橡皮囊液压成形的算法。该算法可简化橡皮囊层与板料接触模型,能够对橡皮囊层所施加作用的板料区域进行自动判断,并对该区域进行液压加载;根据橡皮囊的容积,可自动调整囊内的液压强度,将液压力均匀地分配在零件的节点上;同时,采用该算法对橡皮囊层与板料的摩擦模型进行处理。以一直弯边零件为研究对象,选择铝合金材料AA2024-O进行橡皮囊液压成形模拟,其模拟结果与相关文献中的数据进行比较证明,该文算法对橡皮囊液压零件成形具有良好的精度。     

板带板形与横向厚度分布关系探讨

分析了板带板形与板带横向厚度分布之间的关系、板坯状况对板形的影响     

拼焊板单向拉伸变形非均匀性

从金属塑性理论出发,结合拼焊板成形特点,推导出同材差厚拼焊板试件单向拉伸情况下缩颈时焊缝两侧薄厚板变形量公式。并基于垂直于拉伸方向居中焊缝的拼焊板单向拉伸实验,将实验结果与公式推导结果比较,初步验证了公式的合理性。进而进行了不同焊缝位置(焊缝垂直于拉伸方向,薄厚板厚度比例不同)情况下的拼焊板试件单向拉伸有限元模拟,进一步验证了所推导公式是正确的。另外,分析了单向拉伸状态下焊缝两侧薄厚板变形的非均匀特性,利用文章所提出的公式,可以定量地预测单向拉伸状态下拼焊板试件焊缝两侧材料非均匀性变形量,从而为提高焊缝两侧材料的匹配性以减小拼焊板变形的非均匀性提供了参考依据。     

球面配流副的优化模型研究

本文根据力、力矩平衡、泄漏小以及结构紧凑的原则,建立了球面配流副的优化设计模型。采用这一模型设计,可以获得球面配流副的最佳结构参数,实现力和力矩平衡,并可大大缩短设计周期。     

试论实现高精度板形和厚度一体化控制的途径

分析了板带轧制过程中板形和凸度控制的重要性,减少凸度能显著提高成材率,而轧制过程的固有特性命名得板形和凸度难以控制,为此,讨论了当前常用的3种板形控制模型及其特点,探讨了板形和厚度一体化控制的实施途径。     

球形件拉深成形内皱曲研究

利用ANSYS／LS－DYNA3D软件,建立了包括凸凹模、压边圈及板料在内的整体分析模型。对球形件的成形过程进行了数值模拟计算,得到了板料内外层纬向应力场及其变化过程,并给出了判定内皱曲的依据因素。对于揭示板料内皱曲的机理有重要意义。     

多弯角宽板弯曲成形板厚变化特性研究

以典型的多弯角零件为研究对象,分别用理论计算分析、计算机数值模拟以及物理实验的方法研究了多弯角板料同时成形的变形特性,尤其注重了板料弯曲过程中常见的减薄、伸长等现象的研究.研究结果表明,对多弯角零件同时成形工艺的制定有着一定的理论和实践指导意义.     

无模拉拔感应加热比功率分布函数的理论计算及应用

建立无模拉拔多匝感应线圈加热的比功率分布函数解析模型;提出一种采用图形拟合并结合遗传反求算法确定加热比功率分布函数中待定函数的方法,以镍钛合金无模拉拔为例,确定了一定感应加热条件下,工件的感应加热比功率与感应加热电流、轴向相对位置和工件半径之间的关系;利用所建立的感应加热比功率分布函数,作为镍钛合金无模拉拔成形有限元模拟的热边界条件,计算获得了工件表面温度场,且计算结果与实验结果吻合较好,最大相对误差为7.4%。     

Research of microstructure of spherical graphite iron by electropulsing annealing

This paper investigated the solid-state graphitization of spherical graphite iron by electropulsing annealing. The results indicated that the electropulsing annealing can accelerate the decomposition of cementite, improve the diffusion ability of carbon in the matrix and make more neonatal graphites in small size be formed. With the increase of electropulsing annealing temperature, the graphitization rate is accelerated. At the high temperature and the quick heating rate, the solid-state graphitization can be finished in a short time. Analysis shows that electropulsing annealing promotes the nucleation of graphite and the decomposition of cementite, consequently, the solid-state graphitization of spherical graphite iron is accelerated.     

Investigation into the effects of metallic coating thickness on the corrosion properties of Zn-Al alloy galvanising coatings

Galvalloy (4.5% Al 95.5% Zn) coatings were produced on a continuous coil coating line at Corus Colors’ Shotton works with varying metallic coating thickness from 7.8 μm (120 g m⁻²) to 48 μm (325 g m⁻²) controlled using air knives. An overall decrease in aluminium content from 5.1% to 4.5 wt% and a primary zinc volume fraction increase from 16.2% to 32.8% occurred as the coating thickness is decreased. This reflects greater nucleation in thinner coatings and some removal of Al enriched molten phases. The scanning vibrating electrode technique (SVET) was used to show that increasing the coating thickness from 7.8 to 48 μm resulted in a decrease in the level of zinc removed during corrosion from a 20 mm exposed cut edge from 530 to 220 μg in the 24 h exposure to 5% NaCl solution. The same trend was also observed when external zinc runoff measurements were made at the Port Talbot weathering site. The increasing corrosion observed at lower coating weights results from greater undercutting of these coatings that are further away from a eutectic composition and an increasing tendency for crevice driven corrosion brought about through primary zinc dendrite interconnectivity.     

提高森吉米尔轧机横向厚度精度控制的研究

森吉米尔轧机广泛应用于轧制硅钢片、不锈钢、薄规格有色金属等材料；随着高速冲床的广泛应用。用户对板材的横向厚度提出了更高的要求；通过分析森吉米尔轧机辊系、凸度、轧制工艺，提出了如何用森吉米尔轧机轧制横向厚度高精度板材的方案。