空心铝型材双孔分流组合模设计

通过实例介绍了空心铝型材的双孔分流组合模的设计,有关主要参数的选择以及其与单孔模设计的区别。     

空心铝型材分流组合挤压模CAD系统开发

利用面向对象的设计思想,采用对象模型技术(object modeling technology,OMT)方法,确定了铝型材分流组合挤压模CAD系统的整体构架。用UG/OPEN API接口和UG/OPEN GRIP语言的功能,开发了空心铝型材分流组合挤压模CAD系统。实例证明,利用该系统可以方便地设计出参数化的铝型材分流组合挤压模。用有限体积法模拟铝型材挤压过程,分析金属流动、应力的变化,为优化挤压模结构提供依据。     

空心铝型材蝶形模挤压技术的应用

介绍了一种新型空心铝型材挤压模具即蝶形模的设计技术,蝶形模是将传统分流组合模的矩形分流桥设计成拱形,而且分流桥的中心部位较低,用来减少突破挤压力,改善金属的流动性.系统研究了蝶形模的主要结构及特点.列举了蝶形模在空心铝型材挤压中的一些应用实例,并与传统分流组合模进行了比较研究,通过对比表明:使用蝶形模可以有效降低挤压力...     

基于轮廓法测试惯性摩擦焊接头内部残余应力

采用轮廓法测试小尺寸镍基高温合金惯性摩擦焊接头的内部环向应力、中等尺寸惯性摩擦焊接头内部环向和轴向应力;分析惯性摩擦焊接头内部环向和轴向残余应力分布特征. 结果表明,轮廓法能测试小尺寸及窄小焊缝试件的内部残余应力,能反映出窄小焊缝内部的大梯度焊接残余应力全貌;惯性摩擦焊接头的环向应力沿轴向变化剧烈,沿环向分布均匀,沿厚度分布不均匀;焊缝中心位置外表层区域环向应力小于内表层区域环向应力;焊缝中心外表面轴向应力为压应力,而内表面轴向应力为拉应力,且轴向应力沿厚度呈线性变化.     

防撞梁用空心铝型材挤压模设计及结构改进

以防撞梁空心铝型材为研究对象,根据相关设计标准设计挤压模,利用数值模拟技术获得连续挤压过程中金属流动速度分布情况以及型材截面新旧坯料的变化过程,计算型材横向焊缝的长度,根据模拟结果,针对金属流动速度的不合理性,对分流桥、焊合室以及工作带等结构进行改进。改进后,型材出口处金属流速均匀,横向焊缝长度降低,试模试验与数值模拟结果吻合,为模具结构的设计和改进提供了指导。     

空心型材分流组合挤压CAD/CAE模型的建立

通过对CAD/CAM软件和CAE软件的分析和集成,构筑了型材挤压CAD/CAE/CAM平台,并基于该平台进行了空心型材分流组合挤压的CAD建模、CAD/CAE信息传递和CAE建模,为进一步分析型材挤压过程和优化模具参数打下了基础。     

多次补焊对铝合金型材焊接接头力学性能的影响

针对中空铝合金挤压型材6005A薄壁对接接头在焊态下和分别进行1~3次焊接修补后的拉伸、弯曲、硬度和疲劳性能进行了测试实验和对比分析。结果表明,与焊态下相比,焊缝金属经过1~3次补焊后,焊接接头的抗拉强度和弯曲性能均符合标准规定的要求,接头延伸率变化不大但都低于母材延伸率。在焊态下和分别经过1次、2次补焊后,接头在寿命107周次条件下的疲劳极限也符合规范要求,但经3次补焊后的接头的疲劳极限未能达到要求值。硬度和拉伸实验均表明,在焊接接头的热影响区存在过时效软化区,且软化区为整个焊接接头最为薄弱的环节。     

Bio-mimetic surface structuring of coating for tribological applications

A novel multilayered coating was developed for applications associated with friction reduction and wear resistance improvement. The nano-engineered coating integrates a soft lubricating layer, consisting of MoS₂-PTFE, onto hard load-supporting layers, with controlled surface morphology (roughness and patterning) of cBN-TiN. The coating was synthesized by sequential procedures including electrostatic spray deposition of cBN particles with different average particle sizes, chemical vapor deposition of TiN, deposition of nano- and micro-sized MoS₂ dispersed in PTFE, and curing. The effect of cBN particle size (with different combinations of particle size) and deposition parameters (specifically electrical voltage) on the cBN-TiN surface morphology were studied experimentally and optimized. SEM characterization of the as-synthesized cBN-TiN coating shows surface features similar to that of colocasia esculenta, with alternating nano- and micro-sized domes and “pockets”; the MoS₂-PTFE top layer has MoS₂ particles retained in the pockets by a basket structure formed during PTFE curing. Tribological and scratch tests were carried out for the as-prepared cBN-TiN and cBN-TiN/MoS₂-PTFE multilayered coatings. Sliding test results demonstrate significantly lower friction coefficient for the multilayered coating, showing that the unique integration of soft lubricating layer and biomimetically structured hard layer can effectively improve tribological performance. It is suggested that lubrication at the frictional contacts was realized by continuous release of the lubricants, MoS₂ and PTFE, from the pockets.     

铝合金型材对搭接搅拌摩擦焊接头中Hook缺陷的安全评定

基于断裂力学理论对铝合金型材对搭接搅拌摩擦焊接头中Hook缺陷进行安全评定,并通过疲劳试验进行验证.金相显示Hook缺陷的本质是搭接面在搅拌头剧烈搅拌作用下向上迁移的结果,显现为裂纹的形式.将Hook缺陷归一化为延伸到焊缝内部的单边裂纹,裂纹扩展速率线性拟合得出应力强度因子幅度门槛值ΔKth为2.509 MPa·m1/...     

小波多尺度C—V模型的红外图像分割

由于红外图像大多具有目标边缘模糊、对比度低、噪声多的特点,传统的C-V模型在进行分割时,易产生过分割且计算量大.针对这一问题,本文提出了一种兼顾目标同质性信息的小波多尺度C-V模型红外图像分割方法,该方法根据图像目标和背景同质性信息所占面积比例关系自适应地调节模型的参数.首先对红外图像做小波分解,从分解的顶层低频图像开始,利用改进能量函数,寻找目标边界,通过插值由粗尺度到细尺度逐层演化,最终获得原始图像的分割.该方法与原有方法相比,大大减少数据的计算量,有效地提高了分割速度,改善了分割效果.仿真实验证明了算法的有效性.     

高速轮廓运动综合位置误差控制的研究

高速轮廓运动控制技术已广泛应用于工业中。目前研究主要从减少伺服跟随误差和采用交叉耦合控制减少轮廓误差两个方面来提高运动精度。文章对几种常见的控制方法进行了讨论，并给出了一种综合位置误差控制的方案。该控制方案可在不改变原位置环的基础上大大提高位置伺服的性能，减小高速运动和参数扰动时的轮廓误差。控制理论分析和仿真结果表明了其有效性，且该方案容易实现。     

凝固微观组织的多层次模拟

通过引入溶质再分配、溶质扩散、界面能各向异性和界面曲率,构建了描述合金凝固微观组织形态演变的元胞自动机模型.在介观和微观尺度上的模拟结果表明,该模型可有效地解决微观组织形成的多尺度问题.模拟结果清晰地再现了与实测结果相一致的枝晶形态和生长现象.根据分形理论采用分维定量比较了模拟结果和实验结果,两者的计盒维数分别为1.703和1.694,阐述了分维定量表征枝晶形貌的物理含义.模拟结果表明熔体过冷度和树枝晶的计盒维数呈近似抛物线关系.     

Multi-scale analysis of engineering surfaces

Conventional surface characterization techniques involving random process analysis are limited in characterizing multi-scale surface features relevant to manufacturing processes and functions. This paper introduces a novel technique for multi-scale characterization of engineering surfaces by applying wavelet transform. The main advantages of wavelet transform over other existing signal processing techniques are its space-frequency localization and multi-scale view of the components of a signal. Utilizing these properties of wavelet transform, we can effectively apply multi-channel filter banks to the surface data and link the manufacturing and functional aspects of a surface with its multi-scale features. Surfaces produced by typical manufacturing processes are analyzed using wavelet transform, and the usefulness of wavelet transform in the multi-scale analysis of engineering surfaces is demonstrated.     

Optimization of welding conditions for curvilinear joints

Welding conditions in welding curvilinear joints were optimized. The arc welding of structured panels with a thickness of 0.7 mm with curvilinear welded joints is used as an example to show the solution of the direct task of heat conductivity by the source method. The optimum distribution of the arc power along the length of the curvilinear welded joint with a constant width is determined.     

零件大回弹量时修边线的计算方法

在模具设计中怎样准确计算翻边零件的修边轮廓仍是模具行业的一大难题.许多论文曾提出一些修边线的计算方法,但是一般未考虑到后续回弹过程的影响,尤其是有大的回弹时,这些方法得到的结果就更加不准确了.为了解决大回弹量时的修边线确定问题,研究了有限元变形路径迭代的基本算法,分析了修边轮廓切除、增补过程,回弹的基本解决方法.最后提出了一种考虑大回弹时的修边线确定方法.通过对某汽车底板主保险杠修边线的计算,验证了该方法计算结果的可靠性及在工程上的可行性.     

Multi-scale and multi-representation CAD models reconciliation for knowledge synthesis

Over the last decades, concurrent engineering and design for X approaches have introduced knowledge-based decision supports, analysis methods and feature-based modelling techniques to deliver designed solutions ready for specific lifecycle purposes. However, to cover the emerging knowledge synthesis issue in engineering design, the underlying 3D representations need to be better understood and chained. This paper aims at developing original multi-representation and multi-scale CAD models to integrate properly knowledge in their most suitable form. Reconciliation mechanisms can be set up to validate semantic continuity of the geometric models and to justify the knowledge structuring the design solutions space.     

Multi-scale Al 5083 for military vehicles with improved performance

Mechanical millingat cryogenic temperatures produces a nanostructured powder that can be used to manufacture a bulk, ultrafine-grained (UFG), non-heat-treated aluminum alloy with an attractive combination of physical and mechanical properties. The use of a higher-strength aluminum alloy for the construction of military vehicles will reduce their weight substantially and lead to improved fuel consumption, range, reliability, and speed. By introducing coarse grains and creating a multi-scale microstructure, the ductility of the cryomilled aluminum alloy can be increased above that achieved with a fully UFG structure while still retaining high strength levels. The addition of reinforcing ceramic, in the form of particulate addedduring the milling process, has the ability to increase strength levels even further.     

Composite structural elements for permanent joints

It is shown to be possible to produce permanent joints using composite elements. This approach increases the efficiency of technical solutions as a result of taking into account the scale factor, the more efficient determination of the dimensions of the component and the application of rolled metal waste in production. New designs of welded and brazed joints of the T-, lap and butt joint type are proposed. It is shown that with the non-uniform distribution of working stresses, it is possible to increase the efficiency of loading as a result of using composite elements produced from materials of different strength.