Height Of Workpiece Research Articles

Machining performance of micro-pit and micro-groove composite textured tools in tungsten alloy turning

Tungsten alloys are widely used in aerospace because of their high-temperature resistance, corrosion resistance, high strength, and other excellent comprehensive properties. But tungsten alloys are typical hard-to-machining materials. Surface micro-textures can improve friction properties, such as preparing micro-textures on the surface of cutting tools for tungsten alloys, which is expected to enhance the cutting performance of tungsten alloys. Still, the relevant cutting laws need to be further studied. A combination texture of micro-pit and micro-groove was designed, and the micro-textured tool surface was prepared by laser machining. Compared with non-textured tools, micro-pit and micro-groove composite textured tools can effectively improve the processing quality of tungsten alloys. It happened because textures on the tool’s surfaces enhance machining performance by reducing the actual contact area between the tool and the chip and storing lubrication medium. At the same time, comparative experiments of micro-textured tools and non-textured tools were carried out. The results showed that when cutting W93NiFe alloys with textured and non-textured tools, the maximum reduction in resultant cutting forces with textured tools was 9%. The maximum reduction in surface roughness was 39.3%, the surface burr height of the tungsten alloy workpiece was lower, the number of surface grooves was lesser, and the surface was more flat. The research results are significant in achieving the efficient processing and high-quality manufacturing of tungsten alloys.

Analysis of thread rolling process using an analytical single tooth rolling model based on the slip line field theory and slab method

A thread rolling process is one of manufacturing techniques for producing high performance thread parts. Despite the importance of the process, its design has been dependent on mostly experience of experts, and the parameters of the thread rolling process may not have been systematically optimized. In this study, a new analytical model is proposed for the thread rolling process simplified as a single tooth rolling. The modeling with the slip line field (SLF) theory is used to calculate the protrusion height of workpiece, and the force and torque of the thread rolling are analytically calculated from the classical slab method. Then, the proposed model is used to analyze the effects of lubrication and plastic deformation on the performance of formed part. Moreover, experiments on the single tooth rolling process are carried out to validate the proposed modeling approach. The parametric study shows that the model can predict the force and torque of the thread rolling process with certain accuracy. The viscosity of lubricant has a significant effect on the lubrication pressure, and the friction factor determines the stress during plastic deformation. Also, it is found that the radial feed of the roller has more dominant effect on the lubrication pressure than the tangential speed by squeezing the lubrication during process.

FEM simulation of C45 steel and Cu-ETP billet shaping at hot upsetting between convex conical dies

On the basis of finite element analysis (FEA), geometric differences in the shaping during hot upsetting of cylindrical billets with a height-to-diameter ratio of 1.0 and 2.0 made of C45 (1.0503) steel and copper (Cu-ETP) between pointed convex conical dies with a cone slant angle of 12.5°, 15.0° and 17.5° are considered. The stroke velocity of the upper die is 0.5 m/s; process temperature (t) and accepted surface friction coefficient (|μ): for steel - t = 1100 °C, μ = 0.32, for copper - t = 850 °C, μ = 0.34. An equation is obtained for the relation between values of reduction in height ratio and engineering strain on height of workpiece during upsetting between conical dies, taking into account the initial billet dimensions and unevenness of forming due to the geometry of tool. The presence of qualitative and quantitative differences in shaping along the height of upset steel and copper billets was revealed, i.e. influence on unevenness of forming the rheological properties of materials under process conditions. It is advisable to use the results obtained to design and improve of technological processes of open die and closed die forging with preforming of billets.

Nonlinear dynamic analysis for machine tool table system mounted on linear guides

In this paper, a three-degree-of-freedom dynamic model of a machine tool table system considering nonlinear contact behaviors is established to obtain vibration characteristics. The relationship between contact deformation and force is derived via Hertz contact theory, and piecewise nonlinear interaction forces are obtained. Then, dynamic differential equations of the three-degree-of-freedom system are constructed. The numerical simulations are solved by Runge–Kutta integration method to investigate the dynamic behaviors of the dynamic system. When the system is under a small excitation force, it exhibits softening nonlinear behavior in the primary resonance region. With excitation amplitude increasing to a larger value, the system exhibits hardening nonlinear behavior. In order to better investigate the effects of excitation amplitude, excitation angle, installation distance and height of work piece on the vibration characteristics, frequency–amplitude curves, 3-D frequency spectrum, time history, frequency domain, phase diagram and Poincare section are employed. Jump discontinuity phenomenon, super-harmonic resonance and varied frequency components are dependent on the key parameters. Some conclusions are drawn to suppress the vibration of machining process and improve the quality of work piece.

Three-dimensional finite element simulation analysis of milling deformation of SiCp/Al composites thin-walled parts

In this paper, a three-dimensional simulation analysis by finite element analysis software ABAQUS on the machinability of silicon carbide particle reinforced aluminium matrix (SiCp/Al) composites thin-walled parts with a polycrystalline diamond tool (PCD) has been carried out. It revealed the influence of radial depth, axial depth, feed rate, cutting speed and thin-walled dimensions on machining deformation of the workpiece. The results indicate that the deformation of thin-walled parts at the both ends is larger than in the middle. With an increase in radial depth, axial depth and feed rate, the deformation also increases, but the influence of feed rate is less than axial depth and the influence of axial depth is less than radial depth. Cutting speed has slight influence on the deformation. In addition, the deformation increases with an increase in height of workpiece and decreases with an increase in thickness and length.

Research on the system matching model in ultrasonic vibration-assisted grinding

In this paper, the ultrasonic vibration-assisted grinding is studied, and a new method is provided to solve the problem of matching the machine tool system and the ultrasonic system. By establishing the matching model, this problem is theoretically solved optimally. Moreover, the abrasive grain motion equations, the removal rate model, and grinding force prediction model are presented. Then the grinding force and the processing quality in system matching are researched by numerical simulation. When ultrasonic system parameters exceed the critical value, the surface scallop height of workpiece becomes lower with single-grain track and intergranular track overlapping. The grinding force decreases as the spindle speed, vibration amplitude, and vibration frequency increase. And the grinding force increases as the grinding depth and feed rate increase. Thus, the surface morphology of the workpiece and the change trends of the grinding force can be predicted through the system matching model. As a result, the best ultrasonic equipment can be decided accordingly to cooperate with the machine tool for grinding.

Adaptive Model to Apply the Upper-Bound Theorem in Plain Strain Forging

Present work applies the Upper-Bound Theorem (UBT) with Triangular Rigid Blocks (TRB) to metal forming compression processes like plane strain forge, offering an upper limit to required deformation energy. This analytical method, usually used by means of simplified models, is developed here incorporating different effects that impact in evolution of deformation process like shape factor and friction. By means of a new adaptive model, the shape and size of the rigid zones used for the UBT application are optimized according to the ratio of the width and the height of workpiece.

Study on Spinning of Pentagonal Cross-Section Hollow-Part Based on Orthogonal Experiment Design

The investigation of the effect of processing parameters on forming quality has been one of the highlight researches in spinning. The thickness distribution is an important criterion to evaluate the forming quality. Spinning force affects the processing and equipment design greatly. Combining with the FEA simulation and orthogonal test method, taking the maximum reduction ratio in thickness of workpiece and the maximum spinning force as the evaluation criterion, the esequence of the main forming parameters, such as the feed rate and roundness radius of roller, and the relative height of workpiece were analyzed based on an orthogonal scheme of three-factor and three-level. Both FEA simulation and experiment results show that, during the pentagonal section hollow-part spinning, the influence sequence on the maximum reduction ratio in thickness is relative height of workpiece, feed rate and roundness radius of roller; the influence sequence on the maximum spinning force is relative height of workpiece, roundness radius of roller and feed rate.

Research on Uniform Surface Roughness in Grinding of Revolving Curved Surface

When grinding the revolving curved surface with Arc Envelope Grinding Method, the different curvatures in the convex and concave surfaces make a great difference in the surface roughness. In order to solve this problem, the relationship among envelope height, feeding rate, rotational speed and curvature of workpiece was analyzed based on equal-envelope-height grinding method. The results presented that, low feeding rate of grinding wheel and high rotational speed of workpiece were helpful to obtain smaller envelope height. And the smaller the radius of workpiece curvature, the more different the surface roughness. Besides, it was an effective method to solve this problem by changing feeding rate. The feeding rate should be changed directly proportionally to radius of workpiece curvature. Then, the experimental results indicate that, the fluctuation ratio of surface roughness with variable feeding rate is reduced to 4.896% from 26.17% with constant feeding rate. It proves the validity of hypothesis.

Effect of size of the cylindrical workpiece on the cold rotary-forging process

Cold rotary forging is an advanced but much complex incremental metal forming process with multi-factors coupling interactive effects. The size of the workpiece has a significant effect on the cold rotary-forging process. In the current work, a reliable 3D elastic–plastic dynamic explicit FE model of cold rotary forging of a cylindrical workpiece is established under the ABAQUS software environment. Based on the valid 3D FE model, the effect laws of size of the cylindrical workpiece on metal flow, degree of inhomogeneous deformation of workpiece and force and power parameters in the cold rotary-forging process have been investigated. The research results show the following: (1) With increasing the initial diameter of the cylindrical workpiece D 0, the “mushroom” effect of the deformed cylindrical workpiece becomes less obvious and the deformation becomes more homogeneous, while the maximum axial forging force and forging moment gradually increase. (2) With increasing the initial height of the cylindrical workpiece H 0, the “mushroom” effect of the deformed cylindrical workpiece becomes more obvious and the deformation becomes more inhomogeneous. Meanwhile, the maximum axial forging force and forging moment increase slowly. (3) The effect of the height to diameter ratio H 0 /D 0 by changing D 0 on the cold rotary-forging process is different from that by changing H 0. The above results have been explained by the critical parameter affecting the cold rotary-forging process significantly, namely the length to height ratio of the plastic deformation zone K ¯ .

Cold deformation smoothing of the cylindrical external surfaces by mechanical shocks

The objective of this study is to present a cylindrical exterior surfaces finishing method using repetitive mechanic shocks. The structural changes of the surface layer during impact and after the tools are retracted had been studied. The necessary mechanic shocks are obtained using balls or reels inserted in metallic disks. A mathematic relation that evaluates the micro-irregularities height of the final work piece is presented in the end.

Friction of plasticity: Application of the dynamic friction model

There have not been any suitable friction models to properly solve plasticity problems yet. Most recently, a new dynamic friction model merging the definition expression of the viscosity with the Amontons-Coulomb friction model suggested by the author has been successfully applied in axisymmetric upsetting to predict the contact stresses. In this paper, the dynamic friction model is further used for resolving the problem of plane-strain compression. With element-equilibrium approach, contact stresses in plane-strain compression have been derived. The mathematical expressions of these contact stresses are verified by the previous experimental data with various ratios of instant length to instant height of workpiece and different lubrications. The curves obtained from the dynamic friction model agree with these experimental results very well, not only for contribution of the normal pressure, mean normal pressure, but also for contribution of the friction stress. Comparisons of results of the dynamic friction model, the Amontons-Coulomb friction model, and the constant friction model with the experimental data are also made. It is seen that the predictions by the dynamic friction model show much better solutions to the practical plasticity problems. It is believed that the dynamic friction model could extensively be used to plasticity problems of solids.

Front and back end crop-losses in slab ingot rolling

When a rolling schedule for slab ingots is planned, designers usually take a keep interest in the rolled form developed at the front and back end. Usually, these parts assume a concave shape, such overlaps making up crop losses, which have to be minimized by using the proper rolling technique. Crop losses may make up 3% of the total slab- or bloom-weight and even figures of 10% have been reported from industry. The shape of overlaps formed at the front and back end in slab ingot rolling has been studied theoretically and experimentally and the influence of roll radius, height of workpiece and reduction has been analysed. The theory has been carried out by means of plane-strain upper-bound solutions, whilst the experiments were performed with plasticine (Filia wax) and aluminium in the cold condition: the main part of the experimental programme was accomplished using plasticine. The end shapes obtained from theory and experiment are of the same nature and in good qualitative agreement. However, the experimental results obtained by means of plasticine and aluminuim differ. The best quantitative correspondence with theory is found for the plasticine crop-loss volumes. It is concluded that overhangs and crop-loss volumes formed at the front end are larger than those at the back end. The overhangs and the crop-loss volumes decrease when large rolls are used — especially for heavy reductions — but this phenomenon is, however, less pronounced when considering the back end. When large rolls and heavy reductions are used for small workpiece heights, the concave end-shapes gradually become convex.

定荷重研削切断加工に関する研究(第2報)

The feed rate and the grinding ratio for abrasive cut-off process of S 50 C steel were analyzed 100 times in terms of different combination of grinding conditions. The analysis included the length of cut and the load. The tests were carried out at the wheel speed of 4 800 m/min in order to investigate the optimal abrasive cut-off system. Autoregressive-moving average model, ARMA(2, 1) is developed to represent the stochastic process of the feed rate and the grinding ratio. The feed rate and the grinding ratio are optimum when the pressure between the wheel and the workpiece is 6.67 N/mm2. Best abrasive cut-off performance by the constant load system is obtained by using the length of cut of 15 mm and the load of 300 N with the height of workpiece of 22 mm at the wheel speed of 4 800 m/min.

超塑性Zn-Al合金の開放型盛り上げ加工

The open-die extrusion experiment of both the water quenched superplastic Zn-Al alloy (the water quenched material) and the annealed non-superplastic alloy of the same composition (the annealed material) was carried out under various working conditions to investigate the effect of superplasticity on deformation phenomenon of the material. The results obtained were as follows.(1) The reduction in height (αs) at which the water quenched material began true reverse extrusion decreased with increasing working temperature, while it increased with increasing working speed.(2) The height of workpiece (H0βs) at which the water quenched material began true reverse extrusion increased with increasing working temperature, but decreased with increasing working speed.(3) When the water quenched material was extruded at 250°C with lubricant, the value of αs was large and the value of H0βs was smaller than those obtained under the same conditions but with no lubricant.(4) The reduction in height at which the material began true reverse extrusion nearly coincided with the one at which the diameter of neutral position of workepiece became equal to the diameter of the punch hole.(5) At 250°C, the value of αs for the both materials decreased while the value of H0βs increased with increasing diameter or decreasing height of the unworked workpiece.(6) The adaptability of the annealed material for open-die extrusion was greater than that of the water-quenched material.

A New Method of Cold Extrusion

A new method has been developed, as a consequence of analysis of plastic flow in the cold extrusion process of steel. As a result of experimental studies on the effects of tool shape, extrusion speed and heat treatment of work materials, it has been found that the extrusion pressure in this method is reduced by about 40% compared with the usual one. Moreover, the height of work piece has little effect on the extrusion pressure, so that deeper shells can be obtained without danger of buckling the punch. The duoble-action die has proved that this method can be applied to the production of various ferrous shells.