Theory Of Machining Research Articles

Grinding force model for ultrasonic assisted grinding of γ-TiAl intermetallic compounds and experimental validation

Abstract The introduction of ultrasonic vibration in the grinding process of γ-TiAl intermetallic compounds can significantly reduce its processing difficulty. It is of great significance to understand the grinding mechanism of γ-TiAl intermetallic compounds and improve the processing efficiency by studying the mechanism of ordinary grinding of abrasive grains. Based on this, this study proposes a grinding force prediction model based on single-grain ultrasonic assisted grinding (UAG) chip formation mechanism. First, the prediction model of grinding force is established based on the chip formation mechanism of abrasive sliding ordinary grinding and the theory of ultrasonic assisted machining, considering the plastic deformation and shear effect in the process of material processing. Second, the UAG experiment of γ-TiAl intermetallic compounds was carried out by using diamond grinding wheel, and the unknown coefficient in the model was determined. Finally, the predicted values and experimental values of grinding force under different parameters were compared to verify the rationality of the model. It was found that the maximum deviation between the predicted value of tangential force and the actual value is 23%, and the maximum deviation between the predicted value of normal force and the actual value is 21.7%. In addition, by changing the relevant parameters, the model can predict the grinding force of different metal materials under different processing parameters, which is helpful for optimizing the UAG parameters and improving the processing efficiency.

Mechanics of wedge turns in alpine skiing

A simple approximate theory of snow machining is applied to modelling successive wedge turns of alpine skiing. The model involves predefined control functions describing skier’s control over the turns via angle of attack, edge angle and loading of the skis. To demonstrate the model’s potential, reasonable control functions with a small number of free parameters are designed and used in attempt to reproduce the data obtained in a previous field study by other researches. The results are in semi-quantitative agreement with the data. In particular, the model explains the nature of the abnormally high values for the “coefficient of friction” deduced in that study. Future field studies of wedge turns should aim at measuring the angle of attack, edge angle and loading of the skis. This will allow to determine the control functions from the experimental data and hence to conduct a more stringent verification of the model.

The pre-stress scratching test investigation on silicon carbide ceramics

Based on the theory of pre-stress machining, In this paper the pre-stress scratching test was carried out on SiC ceramics, and the single-point diamond indenter moved with uniform speed under constant normal load. Combining with acoustic emission testing, the acoustic emission signal, the depth of scratch and the damage of surface / subsurface were analyzed under different pre-stress. The results showed that the existence of pre-stress can shorten the depth of median cracks and reduce the surface / sub-surface damage when adopting pre-stress machining method to study the machining of ceramic materials, moreover, with the increasing of pre-stress to a certain extent, the depth of median cracks were decreased and the propagation length of lateral cracks were shortened.

A new localization theory of thin-walled feature machining for near-net-shape part

Localization is usually required for the near-net-shape billet before machining. In conventional research, the to-be-cut features only need to be transformed into the middle of billet to leave the to-be-cut material. However, if it is applied on the thin-walled feature, the machined feature would easily be beyond tolerance due to cutting deformation. Thus, conventional localization principle is not best for the thin-walled feature before the machining. To reduce reject rate for the near-net-shape billet, a new localization theory for the thin-walled features is investigated in this article. The workpiece’s stiffness and cutting force distribution are considered in thin-walled feature localization. By the adjustment of the to-be-cut material, the cutting force is optimized to control the deformation of workpiece. Base on this principle, the cutting deformation is introduced into the constraint conditions of the localization optimization. Thus, the deviation of machined feature is prevented to be outside of tolerance as much as possible. In this work, a practical plate machining is rendered to verify this approach. It lays a theoretical foundation of thin-walled feature localization and is an effective solution for improving qualification rate of the near-net-shape part in industry.

Mechanics of side-slipping in alpine skiing: theory of machining snow and ice

Side-slipping (or skidding) is a feature of several manoeuvres in alpine skiing, including a few types of skiing turns. On hard snow, side-slipping involves removal of a thin top layer of snow, that makes it similar to machining of materials in manufacturing. In this paper, we briefly review the theory of machining and then propose an approximate model that can be used to describe side-slipping in skiing. We test this model against published results of laboratory experiments in machining of ice and snow and find agreement.

A new localization theory of adaptive machining of near-net-shape blades

In the fabrication of aero-engine blades, a great deal is gained when massive material removal is avoided at the end of the process, and as little as possible material is left on the blade billet. Due to the uncertainty of pre-process, the billet shapes are inconsistent. Sometimes, the near-net-shape billet doesn’t cover the blade design surface to be cut. Therefore, blade localization is necessary for these billets before the machining. In conventional localization methods, the design surface’s location focused on guaranteeing enough material to be cut. However, because the to-be-cut surface is in near-net and free-form shape, it is difficult to find a valid localized surface model to generate the tool path. Different from the localized surface is taken as rigid in previous investigation, it is allowed to deviate from the design surface no more than the tolerance band. In term of this principle, the tolerance band is utilized to promote localization ability. A series of optimization models with different priorities is established to avoid the abandonment expensive blade billet. Finally, with the experiments performed on the near-net-shape blades, the blade localization theory and the promotion of localization ability are verified.

Materials and machining trends in terms of the existing axioms of the machining theory

AbstractThe paper provides new insight into existing axioms of theory of machining. The existing theory of metalworking was based on the development of cutting materials during the 20th century. In particular, the improvement of cutting materials, the new special materials and progressive technologies and the trends to increase cutting speed call for a review of existing definitions and relations. Appling previously defined relations between cutting conditions and results of machining, the inaccuracies occur and this may lead to an incorrect choice of cutting conditions in the specific conditions of machining. The paper analyses existing well‐known equations used in practice and on the basis of extensive experimental analysis it modifies them. Furthermore, the paper concerns the evaluation of physical and technological parameters, such as chips compression, machined surface roughness, cutting forces, cutting tool‐wear and tool‐life.

Pseudotransient method for modeling of electrochemical machining

The electrochemical machining is aimed at the fabrication of parts of prescribed shape and dimensions by the anodic metal dissolution using tool-electrodes of various types. The task of the theory of electrochemical machining is to calculate the shape and dimensions of the workpiece depending on the shape of tool-electrode and operation conditions. In this work, a pseudotransient method of modeling, which is new for the steady-state electrochemical machining, is developed. In this method, first, the initial approximation of workpiece surface is prescribed; in the course of modeling, it shifts in the normal direction at a rate proportional to the residual of steady-state condition. The proposed method requires substantially lower computational cost than the non-steady-state method and can be used for the tool-electrodes of arbitrary shape.

The single factor experiment of the non-linear tube in abrasive flow machining

In order to obtain high quality of special channel surface and improve overall performance of machine or parts, this paper regarded the non linear tube-nozzle as the research object, and the single factor experiment was performed in the critical process parameter of abrasive flow machining(AFM) with self-developed abrasive medium, to study the relationship between process parameters and channel surface of microstructure and the influence of process parameters on the workpiece surface quality. The results show that abrasive flow technology can obviously improve surface quality of the non-linear tube, and has important practical value to improve the stability and the functional performance of the non-linear tube. The results can provide technical support for the deep research in the theory of abrasive flow machining.

Development Of A Cathode Designing Method To Avoid Electrodes’ Interference During Blisk Electrochemical Machining

<p>Electrochemical machining plays a prominent role in blisk (bladed integrated disk) construction process. Since blisk channel is narrow and twisted, interference between electrodes may happen during electrochemical machining. Therefore, this paper develops a cathode designing method to avoid interference. Firstly, according to theory of electrochemical machining, machined channel is predicted by calculation. Second, with this channel, interference analysis is carried out and a cathode is designed. Finally, the cathode is employed in experiment and no interference appears.</p>

Effect of cutting edge radius on surface roughness in diamond tool turning of transparent MgAl2O4 spinel ceramic

Transparent magnesium aluminate spinel (MgAl2O4) ceramic is one of an important optical materials. However, due to its pronounced hardness and brittleness, the optical machining of this material is very difficult. Diamond turning has advantages over the grinding process in flexibility and material removal rate. However, there is a lack of research that could support the use of diamond turning technology in the machining of MgAl2O4 spinel ceramic. Using brittle-ductile transition theory of brittle material machining, this work provides critical information that may help to realize ductile-regime turning of MgAl2O4 spinel ceramic. A characterization method of determination the cutting edge radius is introduced here. Suitable diamond tools were measured for sharpness and then chosen from a large number of candidate tools. The influence of rounded cutting edges on surface roughness of the MgAl2O4 spinel ceramic is also investigated. These results indicate that surface quality of MgAl2O4 spinel is relate to the radius of diamond tool’s cutting edge, cutting speed, and feed rate. Sharp diamond tools (small radius of cutting edge) facilitated ductile-regime turning of MgAl2O4 spinel and shows great potential to reduce surface roughness and produce smoother final surface.

Material adhesion and stresses on friction stir welding tool pins

During friction stir welding, polygonal tool pins experience severe stresses and, under certain conditions, loss of functionality due to adhesion of plasticised material on their surfaces. The extent of adhesion is analysed for various pin geometry and welding conditions based on the theory of machining. The effective stresses on the polygonal pins are evaluated following the principles of mechanics. The results show that the polygonal pins with fewer sides can avoid permanent adhesion of plasticised material at higher weld pitch, which is defined as a ratio of welding speed and tool rotational speed. The computed pin geometries for minimum adhesion are compared with the pin profiles recommended by various investigators based on independent experiments. The computed stresses show that pins with larger number of sides will experience lower stresses for any given set of welding variables.

Method of immediately cutting process stoppage

The paper dealt with method of immediately cutting process stoppage, process of chip formation and the non-linear finite element analysis. To be able to follow the process of chip formation and machined surface during machining, it is necessary to stop this process immediately, if it is possible. The paper provides results of non-linear numerical experiment for presented method. The state of plastic deformation in machined material and in front of the tool cutting edge enables to follow the intensity of deformation, friction process between the tool, chip and workpiece, sources of heat in the machining zone. Knowing these processes enables to select optimal tool geometry, cutting conditions, mainly cutting speed, cutting environment, tool material so that cutting process could run with minimal energy consumption and required quality of machined surface could be reached. To understand the process of chip formation is important for the theory and practice of machining of materials.

Evaluation of Machining Strategies for Production of Free Form Surfaces Using 3-Axle Milling

The components with formed surfaces are being an important category of the machine parts. They are applied in the most of industrial branches. In order to produce such type of machine parts it is necessary to harmonise the contradictory requirements, e.g. the minimal production time, the required precision of dimensions and the surface quality. A relevant role is playing the chosen machining strategy specified for the above-mentioned demands, namely during the finishing operations. The most important evaluation criteria for selection of the concrete CAM-system are: the disposable machining strategies, visualisation level of the proposed process and recognition of the virtually machined surface. The term "machining strategy" represents the pre-defined (and in the CAM-system also the available) tool trajectories that are optimised for machining of the variable formed surfaces so that the work-piece could be machined most effectively. A projection and evaluation of the cutting trajectories is not a simple process. There are at disposal many professional articles, which started to be published after occurrence of the first software solutions created as a support of the NC-software development. A development of the new strategies, i.e. the projection and optimisation of the new methods for control of the tool movement on the machined surface, is a multidisciplinary area, which requires knowledge from the theory of machining, descriptive geometry, informatics and also mathematics. The standard machining applications are such strategies, for example, that are able to optimise the cutting conditions in order to achieve a constant loading of the tool and in this way they enable prolongation of the tool durability as well as improving of the manufactured surface quality. Another important area is also evaluation and comparison of the existing strategies because the proper choice of them can help to reduce the machining times and the tool wear-out due to a shortened length of the tool operational path. This fact has a relevant impact on the production efficiency. The main topic of this paper is a description of the quality analysis focused on a surface area, which was machined by means of the various milling strategies and at the same time there were monitored deviations of the machined surface in comparison to the original 3D-model of the free-form surface area. This matters is analysed in [1], [2], [3], [4].

Simulation on Anode Electric Field Intensity about Electrochemical Jet Machining

The theory of electrochemical jet machining was introduced, and effect of different parameters on anodic electric field intensity is finite element analyzed by ANSYS software. The Simulation results show that, the electric field shares the same distribution under different electrolysis voltage, which generally contains three parts, uniform distribution area, gradually weakened area, scattered area. In the uniform distribution area, electric field shows comparative uniformity. The anode electric field generated by different jet distance is also obvious distribution areas, the electric field intensity shows decreasing trend. Electric field intensity is found to have a close relationship with electro jet nozzle diameter, in which a faster jet velocity would bring more concentrated distribution of the electric field as well as a smaller size of electric field.

Design of Electron Beam Polishing Equipment on Mould

The electron beam polishing equipment technology is brought forward and its characteristic is explained because general processing method can’t obtain preferable machining efficiency and product quality. The theory of electronic beam machining is explained in detail, which include electronic beam come into being. The structural drawing is bring brought by this study. The drive principle of worktable movement and the procedure control of electronic beam machining is describe detailedly. The elementary problem is solved on electronic beam machining in theory.

DEM Simulation of Machining Damage in SiC Pre-Stressing Cutting Process

Based on the theory of metal pre-stressing machining, the method of pre-stressing suitable for ceramic materials machining was presented. Using the cluster method, the discrete element method (DEM) model of ceramic materials machining was established. The DEM simulations of cutting process of SiC ceramic under different machining parameters were carried out by orthogonal test design method, and the effects of machining parameters on the number of surface cracks and maximum crack depth after processing were also analyzed. The results showed that the tool edge radius influenced greatly on the number of surface cracks, while the pre-stress influenced greatly on the maximum crack depth.

One problem of the theory of dimensional electrochemical machining of metals

A method is proposed for determining the shape of the anode-article boundary for a given shape of the cathode-tool in plane problems of the theory of dimensional electrochemical machining of metals. Under the assumptions used, the boundary of the anode-article is divided into the working zone, where metal dissolution occurs, and an adjacent zone, where the treatment (dissolution) is terminated. The initial problem is reduced to a problem of a fictitious plane-parallel potential flow of an ideal fluid with a nonlinear condition on the free surface. The point of separation of the fictitious flow from the solid boundary corresponds to the point separating these two zones of the anode boundary. The Brillouin-Will condition of smooth separation is imposed at the separation point to construct a closed system of equations determining the problem solution.

A hydrodynamic interpretation of a problem in the theory of the dimensional electrochemical machining of metals

A method of determining the form of the anode-blank boundary for a specified form of the cathode tool in plane problems of the theory of the dimensional electrochemical machining of metals is proposed. Within the assumptions made, the anode-blank boundary is divided into a working zone, in which solution of the metal occurs, and a region next to it in which the machining ceases. The initial problem is reduced to a problem of plane-parallel potential flow of an ideal liquid with non-linear conditions on its surface. The point which separates these two regions of the anode boundary corresponds to the point where the jet separates from the solid boundary. The Brillouin-Villat smooth separation condition is specified when compiling the closed system of equations at the point where the jet separates.

A scheme for the electrochemical machining of metals by a cathode tool with a curvilinear part of the boundary

The solution of a non-linear plane problem in the theory of the electrochemical machining of metals, associated with the determination of the shape of a surface (the anode) during its treatment with a cathode tool with a curvilinear part of the boundary, is obtained by methods developed for problems of jet flow past curvilinear obstacles. A condition is obtained which is identical to the well known Brillouin-Villat condition in fluid dynamics for smooth separation, the use of which enables one to determine the position of the transition point from the zone of steady treatment conditions into a region where the dissolution of the metal does not occur. The fixed shapes of the anode boundary are found for two cathode configurations.