Study on the deformation mechanism for forming shafts without concavity during the near-net forming cross wedge rolling process

Intelligent robotic welding involves replicating the role of a manual professional welder to adaptively control the welding process. This is necessary to achieve accurate, fast and high-quality welding process in addition to the challenging factors for humans to operate in the welding environment. Therefore, robotic welding exists since the early days of robotics and it is still an active research area. This is why there have been numerous researches in this area for a very long time. Among various techniques proposed by researchers for the adaptive control of the robotic welding process, vision-based control is the most popular due to its non-invasiveness. Therefore, in this paper, we review, analyse and categorise the proposed vision-based techniques with the aim of covering the different image processing and feature extraction aspect of the techniques. The focus is mainly on the active vision system where various image processing techniques have been utilised in extracting the welding seam features. The challenges and difficulties to extract seam features in active vision system have been highlighted. The trends and new approaches have been indicated in order to provide a comprehensive source for researchers who are planning to carry out research related to the intelligent robot vision techniques for welding automation.     

Analysis of a cross wedge rolling process for producing drive shafts

The paper discusses the problems of forming parts such as stepped shafts by cross wedge rolling (CWR). In industrial practice, this rolling process is performed at stages, i.e., in several passes, when large cross-sectional reductions are involved. The same can also be done using a different design of this forming process, namely, multi-wedge cross rolling (MWCR), in which the workpiece is simultaneously formed by several pairs of tools (wedges). This paper compares the above two methods with respect to forming a drive shaft. Wedge tools used in both forming processes are described, and the numerical results of the simulations performed to verify the adopted solutions are reported. The results demonstrate that the MWCR method offers more advantages than the classical CWR technique. Consequently, MWCR is then verified in experimental tests. The experimental results confirm that parts such as stepped shafts can be formed by the MWCR method.     

齿轮轴楔横轧齿形成形质量影响因素研究

应用楔横轧技术生产齿轮轴不仅生产效率高,材料浪费率低而且成形的齿轮轴具有更高的强度.应用Deform软件对齿轮轴楔横轧成形过程中轧件温度、齿数、模数、模具运动速度和分度圆直径对齿形质量的影响进行研究;得出了各因素的重要性影响大小的顺序和各个因素对齿形成形质量的影响规律.     

楔横轧多楔成形汽车半轴工艺可行性分析

分析多楔成形长轴类零件时内/外楔对接段的各种形状及其优缺点,建立了楔横轧多楔成形汽车半轴的三维有限元模型.通过选取合理的轧制工艺,模拟楔横轧多楔轧制汽车半轴的过程,获得了内/外楔之间过渡光滑的汽车半轴.结果表明:楔横轧多楔成形汽车半轴工艺是可行的,该研究为多楔成形半轴的模具设计提供了理论依据.     

轧辊直径对楔横轧大型轴类件应力应变影响分析

合理选择轧辊直径是楔横轧成形大型轴类件的重要技术指标,采用ANSYS/LS-DYNA有限元分析软件,对楔横轧轧制大型轴类件进行模拟,分析轧辊直径对楔横轧大型轴类件应力应变影响规律,阐明轧辊直径对于楔横轧大型轴类件轧件质量的影响程度,研究结果为实现大型轴类件楔横轧经济化生产提供理论依据.     

基于动态仿真的多道冲压工序研究

通过对复杂多次冲压件冲压工艺的分析,初步确定工件各道工序的形状与尺寸。利用DYNAFORM软件对冲压工序进行动态模拟,分析冲压工序的合理性。通过修改参数,确定切实可行的冲压方案。再根据确定的方案设计制造模具,冲压出符合要求的工件。对冲压工序的设计方法和多道成形的动态模拟方法进行了说明,确保模具设计的成功,缩短生产周期,降低生产成本。     

多次冲压工序的数值模拟研究

通过对多次冲压件冲压过程的初步计算和动态仿真,直观地了解了整个冲压过程的各道工序的变形情况,包括应力、应变和厚度分布等,从而知道哪些位置是危险区,并对冲压工艺进行调整。根据模拟结果,设计模具、确定冲压参数,确保了模具设计的成功。     

VBA技术在楔横轧模具数控加工编程中的应用

根据楔横轧模具的特点,设计了模块化的程序结构,并采用Excel的VBA编程技术,开发了模具数控加工代码的自动生成系统,经实践证明该系统高效、方便、实用.     

The establishment of a failure criterion in cross wedge rolling

Internal defects in the cross wedge rolling (CWR) process can lead to the catastrophic failure of products. Using specialised experiments and the explicit dynamic finite element model (FEM), this work investigates the mechanisms of void generation and growth in the cross wedge rolling process. Based on a combined numerical and experimental approach, the morphology of void generation is determined as a function of the workpiece material and three primary parameters in the cross wedge rolling process: the forming angle, , the stretching angle, and the area reduction, _A . Through the definition of a non-dimensional deformation coefficient, , a method for predicting the likelihood of void formation is subsequently ascertained and discussed with respect to CWR tooling design and operating conditions.     

楔横轧轴向力对轧件质量的影响

分析了楔横轧零件时轴向力不平衡所导致的问题及解决办法.     

楔横轧加工铝合金内部损伤的研究

目前优质钢的楔横轧加工方面的研究已经成熟,但铝合金的楔横轧研究很少。使用韧性破坏准则对楔横轧铝合金的内部损伤进行了研究,得到了各个工艺参数对轧件内部损伤的影响规律:最大损伤量随加工温度的升高而下降;随轧辊转速的升高而升高;随模具的展宽角、成形角、断面收缩率的增大而减小。结论对实际生产具有一定的指导意义。     

Analysis of stress in cross wedge rolling with application to failure

In the present investigation, a previously developed three-dimensional finite-element model for the cross-wedge rolling (CWR) process has been used to characterize the workpiece material stress and deformation behavior. Particular attention has been paid to the center and mid-radius points of the billet where internal defects (i.e. internal cracks and porous voids) often occur. Several failure criteria in the solid mechanics theory are summarized. The effect of three important CWR parameters, namely the forming angle, the area reduction, and the friction coefficient, on the field variables has been investigated, including the first principal stresses, maximum shear stresses, etc. A total of 14 rolling conditions are analyzed for the billet material aluminum alloy 1100. After initially verifying the numerical results, several tendencies for the CWR process, as related to failure, are ascertained and discussed.     

Numerical simulations on reducing the unloading springback with multi-step multi-point forming technology

Multi-point forming (MPF) is an innovative flexible manufacturing technology for three-dimensional sheet metal forming. It replaces the conventional solid dies with a set of height-adjustable discrete punches, called the “punch group”. A set of punches can construct various three-dimensional curved surfaces freely and conveniently, through adjusting the relative position of each punch. MPF technology not only saves a significant amount of money and time in the design, manufacture, and adjusting of the dies but it can also be applied to change the deformation path and to improve the forming quality. Unloading springback is an inevitable phenomenon in sheet metal forming using MPF. To control and reduce springback, numerical simulations for the MPF process and the unloading springback are carried out using the explicit-implicit coupled finite element method. Subsequently, influencing factors such as thickness, deformation amount, and material properties of MPF springback are researched to investigate the MPF springback tendency. Next, the multi-step MPF technology is introduced to reduce MPF springback. Based on numerical simulation analysis, it is obviously validated that the unloading springback is decreased when the multi-step MPF method is applied. Finally, it is verified that the equidifferent deformation path and small deformation amount of each forming step can improve the workpiece stress state and minimize the unloading springback effectively by an evaluation result of the deformation path effect on the multi-step MPF.     

Influence analysis of area reduction for necking in twice-stage cross wedge rolling

A symmetric twice-stage cross wedge rolling (CWR) model was developed to analyze the generation mechanisms of necking by using rigid-plastic finite element method (FEM), and particular attention has been paid on the effect of area reduction on necking. After a brief summarize of necking criteria in single-stage CWR, the distribution coefficient of area reduction was presented to analyze the laws of necking in twice-stage CWR. The influences of area reduction on the field variables, including the effective strain, displacement, and damage, have been investigated to explain the laws of necking. With the necking behavior deteriorates, the displacement and damage increase. The traditional idea about distribution of area reduction is that the main deformation, which occurs in first stage, can effectively prevent necking in twice-stage CWR, but in this study, it has been found that the optimal state was achieved when the distribution coefficient of area reduction is close to 1. The production experiment on connecting rod preforming process was given to validate the simulation results. The results show that the law is desirable and gives a good guide for CWR die design.     

A multi-step progressive fault diagnosis method for rolling element bearing based on energy entropy theory and hybrid ensemble auto-encoder

It is meaningful to efficiently identify the health status of bearing and automatically learn the effective features from the original vibration signals. In this paper, a multi-step progressive method based on energy entropy (EE) theory and hybrid ensemble auto-encoder (HEAE), systematically blending the statistical analysis approach with the deep learning technology, is proposed for rolling element bearing (REB) fault diagnosis. Firstly, a preliminary detection about the REB health status is performed by the statistical analysis technique integrated with the EE theory. Secondly, if fault exists in REB, a new HEAE is constructed based on denoising auto-encoder and contractive auto-encoder to strengthen the feature learning ability and automatically extract the deep state features from the raw data. Subsequently, a modified t-distributed stochastic neighbor embedding (M-tSNE) algorithm is developed to achieve the features reduction to further improve the diagnosis efficiency. Finally, the low-dimensional representations after features reduction are as the inputs of softmax classifier to recognize the fault conditions. The proposed method is applied to the fault diagnosis of REB. The results confirm the effectiveness and superiority of the proposed method, and it is more suitable for the actual engineering applications compared with other existing methods.     

基于能量转换的精密级进模卷圆成形研究

结合能量转换理论对多步弯曲成形的卷圆件进行设计,应用ABAQUS软件对其进行有限元数值模拟研究.以射频(RF)连接器中的端子件为例,应力能量特征变化曲线,分析每步成形后的尺寸及回弹,并对整形工序作研究,以控制合口间隙.指导精密级进模设计,提高端子件成形精度.     

Theoretical method for estimation of mean pressure on contact area between rolling tools and workpiece in cross wedge rolling processes

The paper gives a new method no determine the mean unit contact pressures on a material—tool contact surface in cross wedge rolling processes (CWR). The dependencies worked out on the basis of the energy and the upper bound methods permits rolling forces to be determined which are comparable to experimentally measured ones. The analysis provides equations which relate the mean contact pressure q_m to the basic process parameters, namely the forming angle α, the spreading angle β, the relative reduction of a portion δ and the shear friction factors m and m_k.     

汽车半轴楔横轧机辊系动态特性分析

应用ANSYS有限元动力学分析模块,求出汽车半轴楔横轧机辊系在现有边界条件下的固有频率和振型,分析辊系在不同中心距和不同约束下固有频率和振型的变化规律,研究结果为进一步优化该轧机设计,提高汽车半轴精度,实现汽车半轴高效化生产提供了理论基础.