Slave rotation analysis of miniature inner grooved copper tube through rotary swaging process

Miniature inner grooved copper tube (MIGCT) is widely applied in industries. To overcome the weak rigidity and strength of MIGCT during stepped tubes manufacturing, rotary swaging process was selected after comparing with radial forging process. The working principle of the rotary swaging was analyzed. A rotary swaging machine, whose workpiece feeding and clamping was respectively driven by an air cylinder and a finger cylinder, was designed. Experiments indicate that the MIGCT was slave rotating with forging dies during rotary swaging. Theoretical analysis was done to investigate the reason of the slave rotation. Experiments were carried out to verify the theoretical analysis. Furthermore, the influences of push force and clamping force on rotation speed were discussed. With the increase of clamping force, the rotation speed of MIGCT decreases gradually in a constant ratio. However, the push force influences the tube rotation speed slightly. In general, it found that an optimal rotation speed of MIGCT is beneficial to the manufacture of the stepped tube.     

Fabrication of copper/aluminum composite tubes by spin-bonding process: experiments and modeling

The aim of this work is to produce two layered thin-walled Cu/Al composite tube by the spin-bonding process. The process is utilized to bond the aluminum tube into the copper one at thickness reductions of 20?C60% and process temperatures of 25°C, 130°C, and 230°C. The bond strength is measured by T-peeling test, and the bond interfaces are examined by metallography and scanning electron microscopy (SEM). The results show that after a threshold thickness reduction of about 30%, the bond strength increased with the amount of deformation. SEM fractography of the peel surfaces confirms that the copper oxide film is broken in a shear manner during deformation. Severe shear strains applied during spin-bonding process, in fact, make it appropriate for bonding the copper to aluminum. Based on the results, at higher temperatures the resulted bond strength is decreased. It is shown that formation of the brittle intermetallic layer on the interface at high temperatures leads to decrease in the bond strength. In addition to the experiments, a procedure is proposed by which it is possible to calculate the bonding length through the comparison of FEM simulations and the experiments. Based on these calculations and the bonding mechanism, a bond strength model is developed and verified by the experiments.     

Forming limit diagram of aluminum/copper bi-layered tubes by bulge test

Chemo-mechanical-grinding (CMG) is a hybrid process which integrates chemical reaction and mechanical grinding between abrasives and workpiece into one process. It has been successfully applied into manufacturing process of silicon wafers where both geometric accuracy and surface quality are required. This paper aims to study the potential of CMG process in manufacturing process of single crystal sapphire wafers. The basic material removal mechanism in terms of chemical effect and mechanical effect in CMG process has been analysed based on experiment results of two different kinds of CMG wheels. The experiment results suggest that chromium oxide (Cr₂O₃) performs better than silica (SiO₂) in both material removal rate (MRR) and surface quality. It also reveals that, no matter under dry condition or wet condition, CMG is with potential to achieve excellent surface quality and impressive geometric accuracy of sapphire wafer. Meanwhile, test result by Raman spectrum shows that, by using Cr₂O₃ as abrasive, the sub-surface damage of sapphire wafer is hardly to be detected. Transmission electron microscopy (TEM) tells that the sub-surface damage, about less than 50 nm, might remain on the top surface if chemical effect is not sufficient enough to meet the balance with mechanical effect in CMG process.     

Automatic tooling design for rotary draw bending of tubes

Cold rotary draw bending of tubes is a CNC metal forming process widely used in industry. When planning a new process, trial and error is often required in order to calculate the proper overbending and to avoid wrinkling, excessive thinning and flattening. Process design is a critical, difficult, experience-based activity, that requires the selection of several variables. In this paper, a comprehensive, computer-based methodology, called Tube ProDes, is proposed for process design of the rotary draw bending of tubes. The approach can be described as follows. First, numerical calculations are carried out in order to compensate for springback, to evaluate the severity of the bend (i.e. the risk of the occurrence of defects), and to assess the sensitivity of the process to a change in the material properties. Then, the tooling setup is completely designed by fuzzy logic, using the tube material properties, the geometrical data of the bend and the variables previously calculated as input.     

Hydroforming of aluminum extrusion tubes for automotive applications. Part II: process window diagram

Based on the mathematical formulations for predicting forming limits induced by buckling, wrinkling and bursting of free-expansion tube hydroforming, a theoretical “Process Window Diagram” (PWD) is proposed and established in this paper. The theory developed in the first part of the present work was formulated within the context of free-expansion tube hydroforming with both combined internal pressure and end feeding. The PWD is designed to provide a quick assessment of part producibility for tube hydroforming. The predicted PWD is validated against experimental results conducted for 6260-T4 60×2×320 (mm) aluminum tubes. An optimal loading path is also proposed in the PWD with an attempt to define the ideal forming process for aluminum tube hydroforming. Parametric studies show that the PWD has a strong dependency on tube geometry, material property and process parameters. To the authors’ knowledge, this is the first attempt that a PWD is being formulated theoretically. Such a concept can be advantageous in deriving design solutions and determining optimal process parameters for tube hydroforming processes.     

Optimization of machining parameters in rotary EDM process by using the Taguchi method

Electrical discharge machining (EDM) is one of the advanced methods of machining. Most publications on the EDM process are directed towards non-rotational tools. But rotation of the tool provides a good flushing in the machining zone. In this study, the optimal setting of the process parameters on rotary EDM was determined. A total of three variables of peak current, pulse on time, and rotational speed of the tool with three types of electrode were considered as machining parameters. Then some experiments have been performed by using Taguchi's method to evaluate the effects of input parameters on material removal rate, electrode wear rate, surface roughness, and overcut. Moreover, the optimal setting of the parameters was determined through experiments planned, conducted, and analyzed using the Taguchi method. Results indicate that the model has an acceptable performance to optimize the rotary EDM process.     

Hydroforming of aluminum extrusion tubes for automotive applications. Part I: buckling, wrinkling and bursting analyses of aluminum tubes

Three possible failure modes have been identified in tube hydroforming: buckling, wrinkling and bursting. A general theoretical framework is proposed for analyzing these failure modes as an elastoplastic bifurcation problem. This framework enables advanced yield criteria and various strain-hardening laws to be readily incorporated into the analysis. The effect of plastic deformation on the geometric instability in tube hydroforming, such as global buckling, axisymmetric wrinkling and asymmetric wrinkling, is precisely treated by using the exact plane stress moduli tensor. A mathematical formulation for predicting the localized condition for bursting failure is established herein. Furthermore, the critical conditions governing the onset of buckling, axisymmetric wrinkling and asymmetric wrinkling are derived in closed-form expressions for the critical axial compressive stresses. Closed-form solutions for the critical stress are developed based on Neale–Hutchinson's constitutive equation and an assumed deformation theory of plasticity. It is demonstrated that the onset of asymmetric wrinkling always requires a higher critical axial compressive stress than the axisymmetric one under the context of tube hydroforming with applied internal pressure and hence the asymmetric wrinkling mode can be excluded in the analysis of tube hydroforming. Parametric studies show that buckling and axisymmetric wrinkling are strongly dependent on geometric parameters such as t₀/r₀ and r₀/ℓ₀, and that axisymmetric wrinkling is the predominant mode for short tubes while global buckling occurs for long slender tubes.     

铝型材挤压过程的一种数值模拟方法

通过优化几何模型,采用有限元法与有限体积法相结合,并在有限体积模拟阶段进行分步计算模拟的方法,成功地进行了一薄壁大挤压比铝型材挤压过程的数值模拟,获得了型材挤压过程中的材料流动速度、应力、应变和温度分布图,并对其结果进行讨论.     

Joining of aluminium and copper materials with friction welding

Radial basis network (RBN), a special type of artificial neural networks (ANN), is introduced to the field of machining process modeling and simulation. This feed-forward three-layer fully interconnected neural network is successfully used to establish the relationship between the machining conditions (inputs) and process parameters (outputs) for the case of ball end milling. A set of four key input parameters is selected to represent the cutting conditions, while four important characteristics of the instantaneous cutting force are used as the output set. Experiments are conducted to train as well as to validate and assess the performance of the proposed network. In addition, a case study, consisting of a typical machining scenario found in industry, is performed to test and verify the model. A very good agreement is observed between the forces predicted by the new model and their experimental counterparts, thus validating the new approach.     

Joining different metallic sheets without protrusion by flat hole clinching process

In this paper, we propose an architecture based on an artificial neural network (ANN), to learn welding skills automatically in industrial robots. With the aid of an optic camera and a laser-based sensor, the bead geometry (width and height) is measured. We propose a real-time computer vision algorithm to extract training patterns in order to acquire knowledge to later predict specific geometries. The proposal is implemented and tested in an industrial KUKA KR16 robot and a GMAW type machine within a manufacturing cell. Several data analysis are described as well as off-line and on-line training, learning strategies, and testing experimentation. It is demonstrated during our experiments that, after learning the skill, the robot is able to produce the requested bead geometry even without any knowledge about the welding parameters such as arc voltage and current. We implemented an on-line learning test, where the whole experiments and learning process take only about 4 min. Using this knowledge later, we obtained up to 95 % accuracy in prediction.     

曲面铝合金锤击平整技术研究

以曲面铝合金为例,利用工业机器人锤击的方式对曲面类零件表面进行平整,并探究各锤击工艺参数对其表面的粗糙度、硬度及表面形貌的影响.将锤击装置装夹到工业机器人上,控制工业机器人以矩形光栅式运动路径对曲面铝合金表面进行锤击加工,并对锤击后表面的粗糙度、硬度及表面形貌进行测量观察.结果表明:经锤击加工后的铝合金表面粗糙度可达0...     

Modeling of abrasive flow rotary machining process by artificial neural network

Abrasive flow machining (AFM) is one of the non-traditional machining processes applicable to finishing, deburring, rounding of edges, and removing defective layers from workpiece surface. Abrasive material, used as a mixture of a polymer with abrasive material powder, has reciprocal motion on workpiece surface under pressure during the process. In the following study, a new method of AFM process called henceforth abrasive flow rotary machining (AFRM) will be proposed, in which by elimination of reciprocal motion of abrasive material and the mere use of its stirring and rotation of workpiece, the amount of used material would be optimized. Furthermore, AFRM is executable by simpler tools and machines. In order to investigate performance of the method, experimental tests were designed by the Taguchi method. Then, the tests were carried out and the influence of candidate effective parameters was determined and modeled by artificial neural network (ANN) method. To evaluate the ANN results, they were compared with reported results of AFM. An agreement between our ANN results on predictions of AFRM material removal value and surface roughness was observed with AFM data. The results showed through AFRM, in addition to saving of abrasive material, surface finish is achievable same as AFM’s.     

基于火焰图像的回转窑烧成状态识别方法研究

烧成带状态的准确识别是回转窑烧结过程中最为关键的一环.给出了一种新颖的基于火焰图像的烧成状态识别方法.首先,基于一种新颖的设计方法得到的压缩Gabor滤波器组作为预处理阶段,增强具有不同纹理特性的物料区域和火焰区域的可分性.然后,对预处理后的火焰图像采用主成分分析寻找特征火焰图像,通过关联每幅火焰图像与特征火焰图像提取火焰图像的全局特征向量,最终经由概率神经元网络分类器对特征向量进行分类识别.实验结果表明了该方法的有效性.     

一种用车床加工铝长筒的方法

针对铝质长筒零件,提出了生产中常规的加工方法,通过分析其存在的不足,改进了装夹方式及刀具,得出了更为合理的加工方法.     

An analysis of the formability of aluminum/copper clad metals with different thicknesses by the finite element method and experiment

In this research, the possibility of applying forming limit diagrams to the formability and fracture prediction of clad metal sheets is examined. The forming limits of clad metal sheets with different thickness combinations (e.g., A1050 1.0, 1.5, 2.0 mm/C1100 1.0 mm) are investigated via forming limits test (punch stretching tests). The true stress–strain curves of Al/Cu clad metal sheets are obtained through tensile tests. Using the experimental forming limit diagrams and the stress–strain curves, the fracture prediction of clad metal sheets are simulated by finite element analysis. Moreover, deep drawing tests are carried out to compare the experimental with the numerical results. These results can verify the accuracy of finite element model. Finally, significant differences in formability are found, and comparisons of the fracture prediction of clad metals with different initial thickness ratios are analyzed both numerically and experimentally.     

On the process and mechanics of rotary elastoabrasive finishing

Advanced finishing processes, both bonded and loose abrasive type, can be used effectively for microfinishing of internal tubular surfaces. However, generation of uniform finish without altering the geometric form is a key challenge in many of the existing methodologies. Rotary elastoabrasive finishing is proposed as a new methodology to meet similar requirements. Elastoabrasives in the form of mesoscale balls are flexible and convenient to use without any slurry/liquid medium and are capable of controlling the abrasion through an elastomeric backup. The mechanics of material removal and the effect of elastomeric medium in the proposed methodology are discussed, supplemented by systematic experimental investigation using response surface methodology. The average roughness of hardened steel tubes with initial roughness 0.160 μm was significantly reduced to 0.017 μm, after a processing time of 40 min without altering their cylindricity. The experimental setup with rotary attachment presented in this paper is demonstrated to be a flexible system for fine finishing tubular specimens, sleeves, and high aspect ratio bores, which find extensive industrial applications.