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.     

Influence of tool parameters on tool wear in two-roll cross-wedge rolling

A simulation model for two-wedge two-roll cross-wedge rolling was presented by using three-dimensional rigid plastic finite element method. Based on the simulation results, the influence of three tool parameters—the forming angle α, the spreading angle β, and the area reduction Ψ on tool wear—is ascertained and discussed. The study results indicate that the tool wear depth increases with larger α, β, and Ψ. Simultaneously, tool wear can be improved under the condition of α?=?28°, β?=?8°, Ψ₁?=?48.6 %, and Ψ₂?=?53.3 %. Subsequently, blank forming for the engine connect rod was produced in the factory and statistical data from the factory manifests the feasibility of study results.     

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.     

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.     

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.     

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.     

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。     

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.     

Influence of tool wear on surface roughness in hard turning using differently shaped ceramic tools

Hard turning has been applied in many cases in producing bearings, gears, cams, shafts, axels, and other mechanical components since the early 1980s. Mixed ceramics (aluminum oxide plus TiC or TiCN) is one of the two cutting tool materials (apart from PCBN) widely used for finish machining of hardened steel (HRC 50–65) parts, especially under dry machining conditions and moderate cutting speed ranging from 90 to 120 m/min. This paper reports an extensive characterization of the surface roughness generated during hard turning (HT) operations performed with conventional and wiper ceramic tools at variable feed rate and its changes originated from tool wear. Moreover, it compares some predominant tool wear patterns produced on the two types of ceramic inserts and their influence on the alteration of surface profiles. After the hard turning tests, the relevant changes of surface profiles and surface roughness parameters were successively registered and measured by a stylus profilometer. In this investigation, a set of 2D surface roughness parameters, as well as profile and surface characteristics, such as the amplitude distribution functions, bearing area curves and symmetrical curves of geometrical contact obtained for the machined surface, were determined and analyzed. A novel aspect of this research is that the notch wear progress at the secondary cutting (trailing) edges was found to produce the substantial modifications of the individual irregularities, and constitute the altered surface profiles. Moreover, this research contributes to practical aspects of HT technology due to exploring the relations between the tool state at different times within the tool life and the relevant surface roughness characterization.     

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.     

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.     

Prediction model of the exit cross sectional shape of workpiece in round-oval-round pass rolling

A reliable analytic model that predicts the surface profile of the exit cross section of workpiece in round-oval (or oval-round) pass sequence is established. The presented model does not require any plasticity theory but needs the only geometric information on workpiece and roll groove. Formulation is based on the linear interpolation of the radius of curvature of an incoming workpiece and that of roll groove in the roll axis direction when the maximum spread of workpiece is known beforehand. The validity of the analytic model is examined by hot rod rolling experiment with the roll gap, specimen size, design parameter of oval groove and steel grade changed. Results revealed that the cross sectional shapes predicted by the model were in good agreement with those obtained experimentally. We found that the analytic model not only has simplicity and accuracy for practical usage but also saves a large amount of computational time in comparison with finite element method.     

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.