封头的多点成形工艺分析和数值模拟研究

结合多道次成形和分段成形工艺方式,文章对封头的多点成形过程进行了工艺分析。通过对其成形过程的有限元数值模拟,研究了封头多道次成形和分段成形的成形规律,制定了封头的多点成形工艺,并进行了实验验证。结果表明,通过合理的成形工艺,可以用多点成形设备成形封头,并能得到良好的成形效果。     

转向齿扇多向精密成形工艺

为了降低转向齿扇成形载荷、提高成形模具寿命,通过对转向齿扇的结构特点和工艺性分析,结合多向成形金属流动特点,提出了转向齿扇多向精密成形工艺方案。采用有限元模拟软件DEFORM-3D,对转向齿扇多向精密成形过程进行了数值模拟,对其成形过程中的金属流动规律进行了分析并预测成形载荷。结果表明,成形过程中齿扇充填均匀,角隅充填饱满,多向精密成形工艺最大成形载荷比单向闭塞挤压成形载荷降低了29%,成形时间缩短了53%,有利于提高模具的使用寿命。对多向精密成形工艺进行了成形试验,试验成形出的转向齿扇充填饱满,成形载荷与预测载荷基本一致。试验结果表明了该工艺的可行性和实用性。     

汽车B柱热成形技术的比较分析

对乘用车B柱所使用的7种热成形技术进行了介绍,包括普通热成形、补丁板的热成形、与冷冲件拼接的热成形、软硬分区的热成形、不等厚板的热成形、激光拼焊板的热成形,带B柱的热成形门环等。阐述了不同热成形技术对材料、设备、热成形模具和成形前板料等的要求以及不同技术成形的B柱所能达到的碰撞性能和轻量化效果,进而从材料成本、技术难度、轻量化效果、碰撞安全性等角度,对比分析了7种热成形技术组合而成的11种热成形B柱的优劣,对未来热成形B柱的发展趋势进行了展望。分析结果表明,普通热成形B柱技术要求和成本最低,而碰撞性能、轻量化效果最好的为带B柱的热成形门环。     

多点成形中弹性垫变形及其对成形结果影响的数值分析

多点成形过程中的弹性垫技术是抑制压痕的有效方法,但是弹性垫的使用对成形件的形状也有影响。为得到精确的成形件,在成形面造型时必须基于弹性垫的变形对基本体群成形面进行修正。文章对采用不同参数的弹性垫的球面与马鞍面成形件的多点成形过程进行了系统的数值模拟研究,分析了不同参数的弹性垫的不均匀变形及其对成形结果的影响,找出了影响成形件精度的主要原因,为基本体群成形面的补偿提供了依据。     

电弧快速成形工艺的研究现状

介绍了一种新型的快速成形方法--利用焊接电弧进行成形.通过分析比较阐述了电弧成形与其他金属成形方法相比所具有的优势.回顾了迄今为止,基于电弧成形的国内外发展现状.分别选取基于非熔化极气体保护焊、熔化极气体保护焊以及等离子弧焊的快速成形工艺进行阐述,从成形产品性能、表面状态、成形精度方面加以分析,着重阐述了工艺参数对成形效果的影响.指出了现阶段成形工艺所存在的问题.最后对电弧成形的研究方向进行了预测.     

一种空间异形三通半管成形工艺改进北大核心CSCD

为解决一种空间异形三通半管零件在传统冲压成形过程中的成形失效、表面质量不佳及成形效率低等问题,根据零件特征,结合AutoForm有限元仿真软件,对该零件的传统冲压成形过程进行了数值模拟并优化,通过分析其成形失效原因,提出了采用充液拉深成形工艺代替传统冲压成形工艺,并对该零件的充液拉深成形过程进行数值模拟并优化。通过对两种工艺成形效果的对比,验证了工艺改进的可行性。最后,在800 t双动充液成形液压机上,分别采用两种成形工艺试制零件,验证了数值模拟的可靠性和实际的工艺改进效果。通过成形工艺的改进,有效地解决了成形失效问题,表面质量和成形效率得到了显著提升,零件成形效果满足工艺需求。     

汽车覆盖件成形工艺方案优化设计

在汽车覆盖件成形过程中通常会涉及到不同的成形工艺,许多典型汽车覆盖件的成形工艺方案是各种成形工艺的应用集成。该文主要介绍了汽车覆盖件成形工艺方案的拟定,在对典型汽车覆盖件成形工艺进行了具体分析的基础上,对汽车覆盖件成形工艺方案进行应用性研究,通过典型汽车覆盖件成形工艺得出不同的优化设计方案,实现了汽车覆盖件成形工艺的优化设计过程。     

空调前板冲压成形分析与数值模拟

采用板料成形分析软件DYNAFORM对某空调前板的拉深成形进行了数值模拟仿真。对该零件成形工艺进行了优化,研究了不同的压边力、最小模具圆角半径对冲压成形的影响,通过对模拟结果的分析得出了空调前板的最优化成形方案。     

管式连铸结晶器爆炸成形与修复质量分析

对近年来利用爆炸成形技术成形与修复内腔精度高且形状复杂的管式连铸结晶器质量进行了总结,并在大量实验和数值模拟的基础上,对爆炸成形与修复过程进行了分析.分析结果表明,采用爆炸成形加工方法成形与修复管式结晶器可以达到良好的成形精度,且爆炸硬化效应明显,药量等诸多影响因素对成形结果至关重要.这对进一步提高应用爆炸成形与修复管...     

数控渐进正/反向复合成形中成形顺序对成形质量的影响

对于数控渐进成形中装夹面上下两侧都具有形体特征的复杂钣金件,仅利用单一的数控渐进反向成形或正向成形无法完成其成形。针对此问题,提出了一种基于正向成形与反向成形相结合的数控渐进复合成形方法,并给出了3种复合成形策略即正向成形与反向成形的3种成形顺序:反向-正向成形、正向-反向成形、正向/反向并行成形。同时利用数值模拟和实际成形实验对比分析了上述3种成形顺序对成形质量的影响。研究结果表明,采用正向-反向成形和正向/反向并行成形的成形效果优于反向-正向成形;在3种复合成形方式中,采用正向-反向成形的成形质量与成形效率最高。     

The influence of the microstructure of three Al–Si alloys on the cutting-force amplitude during fine turning

When cutting metallic materials, the magnitude and the variation of the amplitude of the cutting force and the quality of the treated surface are of major importance. During the fine turning of alloys that have similar mechanical properties, differences will show both in the roughness of the machined surface and in the magnitude of the cutting forces measured, which can be attributed to the influence of the microstructure of the workpiece material.This paper deals with the influence of the microstructure of Al alloys containing different amounts of silicon on the variation of the amplitude of the signal of the dynamic component of the main cutting force during fine turning. An analysis of the energy spectra and the auto-correlation functions of the amplitude of the dynamic component of the cutting force confirmed the relationship between the latter and the size of the phases in the microstructure of the workpiece material. It was confirmed that the microstructural changes were directly related to the amplitude of the cutting-force variation in the cutting zone. The microstructural changes and the cutting force can be considered as random phenomena; therefore, they may be described by statistical parameters such as the mean value, the standard deviation, and the coefficient of variation. The values calculated for the individual alloys differed considerably and confirmed a close relationship between the statistical values of the intercept lengths of the phases in the microstructure and the dynamic component of the cutting force.     

Crystallographic analysis of the FCC → BCC martensitic transformation in high-carbon steel

Based on the phenomenological crystallographic theory of martensitic transformations, the following crystallographic characteristics of the tetragonal martensite in high-carbon steel have been calculated: orientation relationships between the crystal lattices of the bct martensite and fcc austenite; the magnitude and direction of the macroscopic shear; the habit plane; the angle and the axis of rotation of the crystal lattice of the martensite. The calculation was performed for three variants of lattice deformation: Bain deformation; two-shear Kurdjumov-Sachs deformation; and the deformation we suggested upon the analysis of the fcc-bcc transformation. In the last variant, a minimum rotation of the crystal lattice of martensite is required; consequently, this variant is closest to the real mechanism of the martensitic transformation. An expression has been derived that describes the interrelation between the degree of tetragonality of the crystal lattice of martensite and the magnitude of the shear deformation of the lattice. It has been shown that the 12 crystal-lographically equivalent variants of shear upon the formation of the lattice of the tetragonal martensite form three groups in each of which the martensite has the same tetragonality axis. For each variant of the shear, we have two equivalent variants of deformation of the martensite with invariant lattice. This results in 24 variants of orientation relationships.     

数值模拟技术在汽车覆盖件成形中的应用

金属薄板成形的数值模拟技术在汽车覆盖件生产及其模具设计制造中起着十分重要的作用。数值模拟技术的广泛应用可以帮助模具设计人员显著地减少模具开发时间、试模周期和费用。为此，详细介绍了应用Dynaform软件模拟覆盖件成形过程的一般步骤，并以某汽车覆盖件的拉深为例，对其成形过程进行了数值仿真。通过对模具零件的运动、板料的成形，以及板料厚度的变化，应力应变分布，成形极限预测等结果的分析，进一步弄清了板料形状，压料筋布置以及压边力大小等工艺参数对汽车覆盖件质量的影响。在案例分析的基础上，针对覆盖件坯料拉深过程中可能出现的起皱现象，给出了相应的拉深工艺优化和模具方案优化。     

中凸变椭圆活塞横截面车削加工过程分析

通过分析活塞横截面特征,在满足横截面椭圆度公差要求的前提下,从车削加工的特点入手,提出横截面椭圆离散等分点数量必须满足的要求,并给以恰当的数学描述。在此基础上,用相对运动的原理对直线电机在横截面椭圆加工中的运动过程进行了详细的分析,指出了直线电机要满足横截面椭圆车削加工所必须满足的基本条件。并用MATLAB对活塞横截面车削加工的轨迹进行了仿真。     

The speed of flows in the pool in arc welding in a transverse magnetic field

Physical modelling of arc welding with a wire shows that the flow speed of liquid metal, directed into the tail part of the pool and induced by the constant transverse magnetic field, increases with the increase of current and the transverse component of induction of the field. Experimental results show that the distribution of the flows is determined by the distribution of the density component of the current spreading in the liquid metal of the weld pool. The results can be used in the determination of the optimum frequency of the transverse magnetic field for controlling the dimensions of the penetration zone of the metal and the process of solidification of the weld pool metal in arc surfacing and welding.     

轴向柱塞泵配流副楔形角和方位角求解算法研究

针对配流副油膜形状理论建模难且与试验数据偏差大的问题,基于配流副油膜周向三点试验法,考虑力与力矩因素、偏磨因素和主轴与柱塞缸同轴度误差因素对配流副油膜形状的影响,建立柱塞缸轴向力平衡模型和配流副油膜厚度模型及配流副油膜形状的拟合算法。结果表明：3种试验工况下的三点膜厚拟合曲线与试验曲线吻合良好,进一步求解出配流副楔形角和方位角的时变曲线,为后续研究配流副润滑、摩擦和磨损特性奠定基础。     

Study on heat efficiency of laser-TIG double-side welding

A series of laser-TIG double-side welding experiments for aluminum alloys were carried out to investigate the heat efficiency of the process. The melting efficiency was introduced to evaluate quantitatively the degree of the mutual effect of the laser and the arc. The results showed that the melting efficiency of laser-TIG double-side welding exceeded the sum of the laser and the arc taken separately. With the increase of heat input, the weld depth and melting efficiency of the laser and the arc were increased signifwantly. This, in fact, implies the strong mutual effect of the laser and the arc as heat sources joined simultaneously in the process. Comparatively, the higher efficiency of the laser constituent of heat sources plays the main role in the increase of the process efficiency. The phenomena of arc column convergence, increased laser absorptivity and the formation of heat accumulation region are the causes of the improvement of heat efficiency.     

激光-电弧复合焊接头根部特性分析

对厚板HQ785T1低合金高强钢填充HS-70焊丝激光—电弧复合焊接头根部化学成分分析及元素线扫描分析，结果表明，焊缝部位主要元素的含量介于母材和焊丝之间，焊缝从上部到根部，随着深度的增加，焊缝元素组成越接近母材，根部焊缝组成以母材成分为主，焊丝成分所占比例较小；焊缝根部冲击韧性低于焊缝上部, 增大坡口钝边，焊缝根部的冲击韧性降低；金相显示根部焊缝中心组织为粒状贝氏体组织，随着钝边尺寸的增加，碳化物析出量减少，组织略显粗大，组织脆性增加.     

Ar-N2混合气体对奥氏体不锈钢焊缝化学成分的影响

为了验证Ar-N2混合气体对焊缝中各元素含量和焊缝铁素体数(FN值)的影响，对SS304L奥氏体不锈钢进行了4种比例的Ar-N2混合气体GTAW多层多道焊接试验，研究了4种Ar-N2比例对焊缝金属中各元素含量的影响，以及每条焊缝中各元素含量随着焊道层数的变化趋势。结果表明，不同保护气体类型的11种焊缝化学元素中，只有N元素随着保护气体中氮气比例的升高而明显增加，其它元素则没有明显的影响；经过汇总分析，认为由于稀释率的原因，导致各元素含量在同一保护气体焊缝中的规律为：C元素含量随着层数的增加而下降；Si，P，S和Nb元素含量随着层数的增加无明显上升或下降趋势；Mn，Ni，Cr，Mo和Cu元素含量随着层数的增加而上升；而N元素在纯氩气保护SG-A时的含量随着层数的增加而稍微下降，在SG-AN-0.5，SG-AN-1，SG-AN-1.5 3种保护气体中N元素含量随着层数的增加而上升；分析结果也表明,Creq/Nieq值和FN值有相同的变化趋势，都与氮气含量呈现反比关系。 创新点： 采用了阶梯式的多层多道焊，保留了各层焊缝的原始信息，验证了GTAW焊接方法在保护气体中添加氮气对奥氏体不锈钢焊缝各种化学元素成分的影响，为Ar-N2混合气体GTAW焊接奥氏体不锈钢在工程中的应用提供了可参考的试验数据。     

Analysis of circular trajectory equivalent to cone-frustum milling in five-axis machining centers using motion simulator

The present paper describes the effect of the half apex angle of the cone-frustum on the motion trajectory under simultaneous five-axis motion and the effect of the sensitive direction of the ball bar when the motion trajectory is measured along the three-dimensional circular conical path. In the present paper, simulation of the measurement by means of a ball bar instrument is mainly conducted using a motion simulator developed previously. In particular, a precise mathematical model was developed to express the pitch errors of the axes of rotation of the five-axis machining center having a tilting rotary table driven by worm gears. In the experiment and simulation, primarily the center position and half apex angle of the cone-frustum were varied. In addition, two sensitive directions of the ball bar were investigated. The motion simulator incorporating the pitch error model can express the detailed trajectories obtained by the ball bar, even if the half apex angle and center position of the cone-frustum and the sensitive direction of the ball bar were changed. Then, the influence of the frictional force of the linear axes of motion, and the backlash and pitch error of the axes of rotation on the circular trajectories were analyzed. In particular, for the case of a half apex angle of 45°, the trajectory due to the errors of the axis of rotation is strongly affected by the sensitive direction of the ball bar.