Axisymmetric Workpiece Research Articles

Hot upsetting of axisymmetric workpieces made of titanium alloys

Hot upsetting of axisymmetric workpieces made of titanium alloys

Deep drawing with unconventional tooling: impact of process parameters on a part accuracy

The analysis of influencing factors and their effects on the deep drawing process is essential for producing cost-effective, high-quality workpieces. In this study, the impact of deep drawing process variables, including die radius, blank holder force, and lubrication conditions, on the distribution of wall thickness and changes in radius for axisymmetric workpieces is explored. For the investigation, specialized tooling was created, with core components such as the punch, die, and blank holder made from a two-component resin and fabricated using rapid tooling technology - vacuum casting. The Taguchi method was employed as a statistical tool for planning the experiments, which allowed the impact of process factors to be determined with minimal variability.

Finite Element based Numerical Modelling of Near-Dry EDM with Glycerin-Air Dielectric Mixture

Electrical discharge machining (EDM) is an advanced, non-traditional machining process that is widely employed in sectors such as manufacturing, automotive, aerospace, and medicine. Near-dry EDM is a prospective technology that offers advantages over dry and wet EDM in terms of material removal rate (MRR), tool wear rate (TWR), and surface integrity. A 2D model of the axi-symmetric workpiece based on the Gaussian distribution of the heat flux is used to simulate the single spark in near-dry EDM. The MRR of near-dry EDM is determined at various glycerin flow rates in the glycerin-air combination. The simulation is then performed on the SS304 workpiece with different glycerin flow rates. The results are compared to EDM simulations using N2 and O2 as the dielectric medium. The average MRR of near-dry EDM with an 8 ml/min glycerin flow rate is determined to be 204% higher than that of N2 and 117% higher than that of O2 gas dielectric. When the volumetric ratio of glycerin in the glycerin-air combination increases, the MRR was also found to be increasing. The maximal MRR of near-dry EDM was found to be 129.30703 mm3/min with an 8 ml/min glycerin flow rate and a 0.18 volumetric ratio and a maximal MRR of 144.3407 mm3/min was found with a 15 ml/min glycerin flow rate and a 0.35 volumetric ratio.

Influence of hydrodynamics of electrolyte flow during electrochemical treatment on the quality of the treated surface

The features of the hydrodynamics of the electrolyte in the interelectrode gap during electrochemical processing of a profile axisymmetric workpiece are considered. The distribution of average flow rates and flow lines is calculated for a specified electrolyte supply. The nature and rate of the electrolyte flow are established. The unevenness of the current density is determined taking into account the change in the electrical conductivity of the electrolyte from heating and gas filling of the interelectrode gap, as well as the quality of the treated surface. Keywords: electrochemical treatment, roughness, electrolyte, electrical conductivity, gas filling. kharchenko.mv@bk.ru

Mechanical properties of rotary swaged steel components

The radial infeed rotary swaging is widely used as a diameter reduction forming process of axisymmetric workpieces, improving the mechanical properties with excellent near net shape forming. In the present study, rotary swaging experiments with different parameter setups were performed on steel tubes and bars under different material states and several resulting property modifications were investigated such as stress-strain curve, hardness, fatigue strength and surface residual stresses. The results show a significant work hardening induced by the rotary swaging process and an improvement in the static and dynamic mechanical properties was observed. Furthermore, the hardness distribution was homogenous in the cross section of the rotary swaged workpieces. Moreover, depending on the process conditions, different residual stresses distribution were generated along the surface.

Special automatic control system for the accuracy of processing axisymmetric workpieces

The article discusses a special automatic control system for the machining process as applied to metal turning lathe. In processing, generalized information about the precision parameters of the processing system is gathered that makes affordable to integrate four control loops into its system. The first control loop stabilizes the tool post body. The second control loop stabilizes the workpiece axis during cutting. The third control loop stabilizes the cutting edge and the fourth one stabilizes the tool-workpiece.

Optimization of fixture flexibility for irregular geometries of workpiece based on metamorphic mechanisms

This paper proposes a novel flexible fixture for workpiece with irregular geometries like non-axisymmetric cylinder. According to the processing condition and geometric characteristics, a new 3-2-1 locating principle, which is different with the 4-1-1 in the case of axisymmetric cylindrical workpiece, is proposed. Based on this, a novel flexible fixture containing locating and clamping systems is designed. The core part of it is the clamping system based on a metamorphic mechanism that consists of specially designed “spring balls” and “chasing turntables” which provide strong flexibility for indenters. The spring balls are capable to change connection state between indenters automatically with respect to whether single indenter is resisted by workpiece or not, while the chasing turntables are able to automatically connect indenters again after all of them have been resisted. Therefore, the flexible fixture is adaptable to different geometries by enabling the indenters to approach the irregular surface synchronously, touch it asynchronously, clamp it synchronously, and release it synchronously. The main contribution of this paper is the application of metamorphic mechanism to fixture designing that has not been widely concerned yet. This work significantly improves the clamping efficiency of fixture and its adaptability to irregular workpieces.

Implementation of Low-Sensitivity Adaptive Control Systems in Machining Low-Stiffness Axisymmetric Workpieces

Abstract This work analyses and proposes an application of adaptive control systems exhibiting low-sensitivity to changes in the technological system parameters in machining low-stiffness axisymmetric workpieces. Secondly, the frequency ranges at which the adaptive control system shows high sensitivity to changing machining allowance were determined. Finally, the developed method enables increasing the control accuracy of dynamic system parameters under changing feed rate and adjusting the elastic-strain parameters of the low-stiffness workpiece by means of the introduction of an error correction block in the form of negative feedback relative to the cutting force. The paper presents the method for constructing adaptive control systems that exhibit low sensitivity to modification of turning or grinding parameters.

A study on the effect of tool electrode thickness on MRR, and TWR in electrical discharge turning process

Turning by electrical discharge machining (EDM) is an emerging area of research. Generally, wire-EDM is used in EDM turning because it is not concerned with electrode tooling cost. In EDM turning wire electrode leaves cusps on the machined surface because of its small diameters and wire breakage which greatly affect the surface finish of the machined part. Moreover, one of the limitations of the process is low machining speed as compared to constituent processes. In this study, conventional EDM was employed for turning purpose in order to generate free-form cylindrical geometries on difficult-to-cut materials. Therefore, a specially designed turning spindle was mounted on a conventional die-sinking EDM machine to rotate the work piece. A conductive preshaped strip of copper as a forming tool is fed (reciprocate) continuously against the rotating work piece; thus, a mirror image of the tool is formed on the circumference of the work piece. In this way, an axisymmetric work piece can be made with small tools. The developed process is termed as the electrical discharge turning (EDT). In the experiments, the effect of machining parameters, such as pulse-on time, peak current, gap voltage and tool thickness on the MRR, and TWR were investigated and practical machining was carried out by turning of SS-304 stainless steel work piece.

The influence of microstructure deformation on the corrosion resistance of cold formed stainless steel

Rotary swaging is an incremental cold forming process to produce axisymmetric workpieces from rods and tubes. The process also induces changes of the microstructure of the material depending on the process parameters. This in turn influences the mechanical properties like hardness as well as the electrochemical properties. As a result of changed electrochemical properties, the passivity of the material and thus the corrosion behavior changes. In order to investigate the influence of rotary swaging on the corrosion behavior of the stainless steel AISI304, deformed micro parts are electrochemically analyzed. The measurements reveal a dependency of corrosion rate and impedance on both feed velocity and final diameter of the rotary swaging process. A higher feed velocity decreases the corrosion rate and increases the impedance indicating a better resistance against corrosion as a side effect of rotary swaging.

Generation of residual stresses in rotary swaging process

Infeed rotary swaging is an established incremental cold forming production technique for axisymmetric workpieces. Among others, work hardening as well as near net shape forming are advantages of this production technique. Due to the incremental open die forging process, the rotary swaging induces a complex material flow history which is dependent on the process control. This material flow history influences the material modifications such as work hardening as well as residual stresses. In this study, the properties of steel tubes were investigated after rotary swaging using varying parameters by experimental and simulation analysis. In particular, the influence of lubrication with different feeding velocities was analysed. The workpiece quality, the hardness and the residual stresses were characterized in detail. After rotary swaging, an influence of the process parameters on the geometrical and surface quality could be observed. The workpieces showed significant work hardening which was higher at the surface and process dependent, while below 100 μm, this increased hardness was observed over the complete wall thickness independently of the process parameters. The residual stress state was highly fluctuating at the surface and was in tensile for all conditions. The results showed that the process parameters influenced the properties near the surface, while a few hundred micrometers below the surface, the workpiece properties seemed to be driven only by the total deformation.

Study on Cutting Marks by Turn Mill Process

Recently, the demand for reducing machining time and cost is increased on the site of production. Therefore, the turn-mill complete machining center that have both the functions of turning and milling have been developed according to the demand of the users. One of the processing methods being paid attention is the turn-mill process that gives intermittent cutting along the outside of the axisymmetric workpiece with turn-mill complete machining center. Although this method is high-speed and high efficiency process, there is a problem that it can be used only for roughing process because specific spiral texture is generated on the cut surface and the surface roughness is large. In this study, in order to apply this turn-mill process to finish machining, experiments were performed with the radius endmills that have both features of square endmills and ball endmills.

Identification and Analysis of Residual Stresses in the Axisymmetric Workpiece Existing before and after Machining

Semi-manufactured parts dedicated for precise machining often have internal stresses which have remained after previous cutting and plastic processing. These stresses reside in a fixed state of balance over the entire volume of the workpiece. Removal of the machining allowance is associated with a change in the state of balance and deformation of the workpiece, which affect its dimensional and shape accuracy. The study, involving non-stress removal of precisely defined volume of the machining allowance and determination of the impact of this treatment on the deformation of the workpiece surface is presented. It is important from the point of view of dimensional tolerance of the axially symmetrical workpiece, finally processed by turning.

A study of basic mechanics in the multi-point single-point incremental combined forming of sheets metal

Based on highly efficient multi-point forming and highly accurate single-point incremental forming, precise and efficient digital formation of three-dimensional metal sheets can be realised. In this article, stress states during the forming process were investigated based on mechanical equilibrium theory. The results showed that contact points of the matrix were subject to vertical tensile stresses when friction coefficient between metal sheets and matrix was relatively low and the angle between metal sheets and vertical plane was small. In other cases, the contact points of matrix were subjected to compressive stresses and dimplings may occur. For the axisymmetric workpieces, radial shear stress in the deformed zone decreased with the increasing radius of tool head and decreasing feed. The theoretical formula of forming force was deducted based on the principle of conservation of energy. According to this formula, the forming force was proportional to the thickness and yield strength of metal sheets and increased with increasing feed. Based on the study of multi-point single-point incremental combined forming, the parameters of tests and numerical simulations can be optimised.

A Prediction of Quenching Parameters Using Inverse Analysis

Abstract The cooling curves of still water and of water-based polymer quenchant polyalkylene glycol (PAG) were recorded with the ISO Inconel 600 probe with 12.5 diameter and 60 mm length equipped with a type K thermocouple inserted into the probe's geometric center. The research included recording of cooling curves for still water in temperature range from 20 to 60°C, as well as quenching experiments with water based polymer solutions with concentration from 10 to 30 vol. % of PAG. The possibility of a new cooling curve determination method for any given water temperature based on interpolation model and experimental data for cooling curves at three different water temperatures was tested. Surface temperature, heat flux density, and heat transfer coefficient (HTC) were estimated based on the recorded cooling curve at the center of the ISO Inconel 600 probe using the solutions of inverse heat conduction problem (IHCP). The results of the inverse heat transfer analysis of the ISO Inconel 600 probe cooling in water and water based polymer solutions were compared to the results of the commercial software ivf SQintegra ver4.0 for the same cooling experiments. The proposed inverse determination of HTC can be used for the specification of boundary conditions in numerical simulations of quenching axisymmetric work pieces with similar dimensions to the ISO Inconel 600 probe.

A Same Area Method Used to Calculate the Strain in Forming for an Axisymmetric Workpiece

An experimental study is conducted to explore a new method to calculate the strain in axisymmetric workpiece forming. When designing deep drawing die for an axisymmetric workpiece, the principal strain during the forming is needed to estimate formability and to decide whether the forming is finished in one pass. Strain calculation is a difficult task, so an ideal same area method used to calculate the strain for an axisymmetric workpiece along with a correction same area method considered thickness reduction rate is proposed here. The deep drawing test for an axisymmetric workpiece is used to obtain the strain along circumference and generatrix direction. The strain along the two directions calculated by the ideal same area method and correction same area method is compared with experimental results. The results show that ideal same area method can be used to calculate the strain during the forming process for an axisymmetric workpiece and the result from correction same area method is close to the experiment.

Deformation determination of the layers in the axisymmetric forming a two-layer billet

The paper describes the experimental study of an axisymmetric two-layer workpiece forming with viscoelastic bonding layer. It shows the distribution of thinning of layers in radial the direction is received. It is revealed that the distribution pattern of thinning of the outer and inner layers of the cross section of the billet significantly differ.

Optimal control of a nonlinear induction heating system using a proper orthogonal decomposition based reduced order model

This paper considers the problem of obtaining control inputs for induction heating processes involving nonlinearities and nontrivial geometries. The considered system falls within the much broader class of multiphysics or coupled, distributed parameter systems that are well known for the challenges they pose towards modeling, simulation and control. The approach is based on the versatile finite element method (FEM) widely popular in industry for modeling of such systems. The large dynamic model obtained through FEM is reduced using proper orthogonal decomposition (POD) technique, applicable to nonlinear systems, while preserving the input–output characteristics almost exactly. In the present work, using the reduced model, an optimal control input current for the induction heating system is obtained, for transferring the temperature profile over an axi-symmetric work piece from any initial temperature profile to any other desired temperature profile. The reduced model enables application and numerical implementation of established optimal control techniques based on Hamilton–Jacobi–Bellman theory for the system. Further, although the controller is developed using the reduced model, it is shown to perform perfectly well when used with the original unreduced model as well. Results of the numerical implementation are presented to evaluate the overall proposed approach.

FEM Analyses of Friction Coefficient in Open Die Coining Process of Different Grain Sizes

The study concerns the analysis of significant contact friction changes by changing the size of crystal grains in the processes of free axisymmetric work pieces upsetting, initial height of 2 mm. The friction changes result with significant changes in forming force. This phenomenon usually characterizes micro forming processes. Using hard experimental data in the creation of numerical FE (finite element) model, a dependence of the changes of contact friction in correlation to the change of the work piece crystal grain size for three different grain sizes: 39, 47 and 76 μm is presented. It is shown that the friction factor is increased by reducing the size of crystal grains. Physical interpretation of the results is given by theory of Bowden and Tabor.

大型回转类锻件的三维重建方法

大型回转类锻件的三维重建方法